BMS 345 Final Exam Study Guide PDF

BMS 345: Final Exam Study Guide CEREBROVASCULAR SYSTEM: Know the location (on gross specimens) and what area of the brain each artery supplies blood to: o Internal Carotid Artery (ICA) ▪ Location: In the neck, ascending to the base of the skull and entering the cranial ca...

BMS 345: Final Exam Study Guide CEREBROVASCULAR SYSTEM: Know the location (on gross specimens) and what area of the brain each artery supplies blood to: o Internal Carotid Artery (ICA) ▪ Location: In the neck, ascending to the base of the skull and entering the cranial cavity through the carotid canal. ▪ Supplies: Anterior and middle parts of the brain, including the cerebral hemispheres. o Anterior Cerebral Artery (ACA) ▪ Location: Branches from the ICA and runs medially along the longitudinal fissure. ▪ Supplies: Medial frontal and parietal lobes, corpus callosum. o Anterior Communicating Artery (AComm) ▪ Location: Connects the left and right ACAs near the optic chiasm. ▪ Function: Part of the Circle of Willis, facilitating collateral circulation. o Middle Cerebral Artery (MCA) ▪ Location: Extends laterally from the ICA, traveling within the Sylvian fissure. ▪ Supplies: Lateral aspects of frontal, parietal, and temporal lobes; basal ganglia. o Anterior Choroidal Artery (no identification) ▪ Supplies: Optic tract, internal capsule, thalamus, hippocampus, and choroid plexus. o Lenticulostriate Arteries (no identification) ▪ Supplies: Deep structures like the basal ganglia and internal capsule; vulnerable to stroke. o Posterior Cerebral Artery (PCA) ▪ Location: Arises from the basilar artery and courses posteriorly. ▪ Supplies: Occipital lobe, inferior temporal lobe, and posterior parietal cortex. o Posterior Communicating Artery (PComm) ▪ Location: Links ICA to PCA. ▪ Function: Completes the Circle of Willis, collateral supply. o Superior Cerebellar Artery (SCA) ▪ Location: Arises from the basilar artery near its bifurcation. ▪ Supplies: Superior surface of the cerebellum, midbrain. o Basilar Artery ▪ Location: Runs along the midline of the brainstem.  ▪ Supplies: Brainstem, cerebellum, and PCA. o Pontine Arteries ▪ Location: Branch from the basilar artery along the pons. ▪ Supplies: Pons. o Vertebral Arteries ▪ Location: Ascend through transverse foramina of cervical vertebrae, merging to form the basilar artery. ▪ Supplies: Medulla, cerebellum, and posterior brain structures. o Anterior Inferior Cerebellar Artery (AICA) ▪ Location: Branches from the basilar artery. ▪ Supplies: Inferior cerebellum and parts of the brainstem. o Posterior Inferior Cerebellar Artery (PICA) ▪ Location: Branches from the vertebral artery. ▪ Supplies: Inferior cerebellum, medulla. o Anterior Spinal Arteries (1) ▪ Location: Single artery running along the anterior spinal cord. ▪ Supplies: Anterior two-thirds of the spinal cord. o Posterior Spinal Arteries (2) ▪ Location: Two arteries along the posterior spinal cord. ▪ Supplies: Posterior one-third of the spinal cord. Blood Brain Barrier: function and structure o Function: Protects the brain from toxins, pathogens, and fluctuating plasma composition while allowing nutrient exchange. o Structure: Composed of endothelial cells with tight junctions, a basal lamina, astrocyte end-feet, and pericytes. Anastomoses: functional vs anatomical o Functional Anastomoses: Active blood flow channels that provide collateral circulation. o Anatomical Anastomoses: Physical connections between vessels, some of which may not normally carry blood flow. Cerebrovascular Accidents 1. Thrombus: A blood clot that forms in a vessel, obstructing blood flow. 2. Embolus: A clot or debris traveling through the bloodstream that lodges in a distant vessel. 3. Infarct: Tissue death due to prolonged lack of blood supply. 4. Ischemia: Reduced blood supply leading to tissue damage.  5. Transient Ischemic Accidents (TIAs): Temporary blockage causing reversible symptoms. 6. Aneurysm: Localized dilation of a blood vessel due to weakness in the wall, risk of rupture. SKULL: Know the location on skulls and its purpose: 1. Jugular Foramen ○ Location: At the base of the skull, between the temporal and occipital bones. ○ Purpose: Passage for the internal jugular vein and cranial nerves IX (glossopharyngeal), X (vagus), and XI (accessory). 2. Foramen Magnum ○ Location: Large opening in the occipital bone. ○ Purpose: Passage for the medulla oblongata, vertebral arteries, and accessory nerve. 3. Cribriform Plate ○ Location: Part of the ethmoid bone, located at the roof of the nasal cavity. ○ Purpose: Passage for olfactory nerve fibers (CN I) for the sense of smell. 4. Frontal Crest ○ Location: Midline ridge in the frontal bone, near the anterior cranial fossa. ○ Purpose: Attachment for the falx cerebri, a dural fold. 5. Crista Galli ○ Location: Vertical projection of the ethmoid bone, superior to the cribriform plate. ○ Purpose: Attachment for the falx cerebri. 6. Olfactory Grooves ○ Location: Depressions lateral to the cribriform plate in the anterior cranial fossa. ○ Purpose: Accommodate the olfactory bulbs. 7. Sella Turcica ○ Location: Saddle-shaped depression in the sphenoid bone. ○ Purpose: Houses the pituitary gland. 8. Hypophysial Fossa ○ Location: Central part of the sella turcica. ○ Purpose: Direct seat for the pituitary gland. 9. Clinoid Processes ○ Location: Projections around the sella turcica (anterior and posterior). ○ Purpose: Anchor points for the tentorium cerebelli. 10. Groove for Middle Meningeal Artery ○ Location: Indentation in the inner surface of the temporal and parietal bones. ○ Purpose: Protects the middle meningeal artery. 11. Groove for Superior Sagittal Sinus ○ Location: Along the midline of the calvaria (skullcap). ○ Purpose: Houses the superior sagittal sinus, a dural venous sinus. 12. Groove for Confluence of Sinuses ○ Location: Near the internal occipital protuberance. ○ Purpose: Convergence point for the superior sagittal, straight, and transverse sinuses. 13. Groove for Transverse Sinus  ○ Location: Horizontal grooves on the internal occipital bone. ○ Purpose: Houses the transverse sinuses, draining venous blood from the brain. 14. Groove for Sigmoid Sinus ○ Location: Curved groove on the internal surface of the temporal and occipital bones. ○ Purpose: Houses the sigmoid sinuses, which drain into the jugular vein. Cranial Herniations 1. Falcial Herniation ○ Definition: Displacement of brain tissue under the falx cerebri, usually involving the cingulate gyrus. ○ Impact: May compress the anterior cerebral artery, causing ischemia. 2. Tentorial Herniation ○ Definition: Herniation of brain tissue through the tentorial notch (incisura). ○ Impact: Compresses the midbrain, potentially causing changes in consciousness, pupil dilation, and hemiparesis. 3. Tonsillar Herniation ○ Definition: Downward displacement of the cerebellar tonsils through the foramen magnum. ○ Impact: Can compress the medulla, leading to respiratory and cardiovascular compromise. Coup and Contrecoup Injuries Coup Injury: Damage occurs at the site of impact due to a direct blow to the skull. Contrecoup Injury: Damage occurs opposite the site of impact due to brain movement and collision with the inner skull. Purpose of Study: Understand brain trauma mechanics and clinical implications. VENTRICLES/CSF: Know the location (on gross specimens) and BE ABLE TO KNOW THE ORDER OF CSF/VENOUS FLOW FROM LATERAL VENTRICLES TO JUGULAR VEIN!! Lateral Ventricles (2) o Location: Located in each hemisphere of the brain. o Regions: Anterior horn, body, atrium, inferior horn, and posterior horn. o Function: The primary spaces where cerebrospinal fluid (CSF) is produced and stored. Interventricular Foramen (Foramen of Monro) o Function: Connects the two lateral ventricles to the third ventricle. Third Ventricle o Location: A narrow cavity located between the two halves of the diencephalon. o Function: Houses the choroid plexus, which produces CSF. Mesencephalic (Cerebral) Aqueduct o Location: Connects the third ventricle to the fourth ventricle. o Function: Allows the flow of CSF from the third to the fourth ventricle. Fourth Ventricle o Location: Located in the pons and medulla, it is a diamond-shaped cavity.  o Function: Releases CSF into the subarachnoid space via the medial and lateral apertures. Medial Aperture (Foramen of Magendie) o Location: Single opening in the fourth ventricle. o Function: Allows CSF to flow from the fourth ventricle into the subarachnoid space. Lateral Apertures (Foramina of Luschka) o Location: Two openings on either side of the fourth ventricle. o Function: Allows CSF to flow into the subarachnoid space. Superior Sagittal Sinus o Location: A large venous sinus located along the top of the brain in the falx cerebri. o Function: Drains CSF and venous blood from the brain into the venous system. Inferior Sagittal Sinus o Location: Located along the lower margin of the falx cerebri. o Function: Drains blood from the deep parts of the brain. Straight Sinus Location: Found along the junction of the falx cerebri and tentorium cerebelli. Function: Drains venous blood from the deep brain structures and CSF from the inferior sagittal sinus. 11. Confluence of Sinuses Location: Junction where the superior sagittal sinus, straight sinus, and transverse sinuses meet. Function: Drains blood from the brain and CSF into the transverse sinuses. 12. Transverse Sinus Location: Found along the edge of the tentorium cerebelli. Function: Drains blood and CSF toward the sigmoid sinus. 13. Sigmoid Sinus Location: Continuation of the transverse sinus, located along the posterior side of the skull. Function: Drains blood and CSF into the internal jugular vein. 14. Jugular Vein Location: Runs down the side of the neck. Function: Carries deoxygenated blood from the head and neck back to the heart. Other Structures 1. Septum Pellucidum ○ Location: Thin membrane separating the lateral ventricles. ○ Function: Divides the lateral ventricles in the brain but does not play a role in CSF flow. 2. Massa Intermedia ○ Location: A mass of gray matter connecting the two halves of the thalamus. ○ Function: Though its function is unclear, it is involved in communication between thalamic halves. Choroid Plexus Location: Found in the ventricles, particularly the lateral ventricles, third ventricle, and fourth ventricle. Function: Produces CSF by filtering blood. CSF Production and Reabsorption  Production: CSF is produced by the choroid plexus, primarily in the lateral ventricles. Reabsorption: CSF is reabsorbed into the venous system through the arachnoid villi, which protrude into the superior sagittal sinus. Hydrocephalus Definition: A condition where there is an excessive accumulation of CSF in the ventricles, often due to obstruction in the CSF pathways. Cause: Obstruction of CSF flow, impaired reabsorption, or overproduction. Symptoms: Increased intracranial pressure, headache, vomiting, visual disturbances, and cognitive dysfunction. Blockages in the CSF Pathway 1. Blockage of the Interventricular Foramen ○ Effect: Causes non-communicating hydrocephalus, as CSF cannot flow from the lateral ventricles to the third ventricle. 2. Blockage of the Mesencephalic Aqueduct ○ Effect: Leads to non-communicating hydrocephalus between the third and fourth ventricles, causing a buildup of CSF in the third ventricle and lateral ventricles. 3. CSF Leaks Through the Dura ○ Effect: May cause a decrease in intracranial pressure (known as a CSF leak), potentially leading to headaches, dizziness, and visual disturbances. Leaks can also result from trauma, surgery, or spontaneous perforations of the dura mater. MENINGES: Know the location (on gross specimens) and know what it is attached to and if there is a real/potential space. o Pia Mater ▪ Location: Adheres closely to the brain and spinal cord. ▪ Space: None (directly on neural tissue). o Arachnoid Mater ▪ Location: Lies superficial to the pia mater. ▪ Space: Subarachnoid space (real space containing CSF). o Arachnoid Granulations/Villi ▪ Location: Protrude into the superior sagittal sinus. ▪ Function: CSF reabsorption into venous circulation. o Dura Mater ▪ Meningeal Layer: Closely adheres to the brain. ▪ Periosteal Layer: Attached to the inner surface of the skull. ▪ Space: Epidural space (potential space in the skull). Other structures to know on specimens: know what their purpose is o Falx cerebri o Tentorium cerebelli  o Middle meningeal artery What is the function of the meninges? Cranial Bleeds: o Epidural hematoma o Subdural hematoma CSF Flow and Venous Flow (Order and Locations on Specimens) 1. CSF Flow from Lateral Ventricles to Jugular Vein: ○ Lateral Ventricles (2): Locations: Deep within each cerebral hemisphere. Sections: Anterior horn, body, atrium, inferior horn, posterior horn. ○ Interventricular Foramen (of Monro): Connects lateral ventricles to the third ventricle. ○ Third Ventricle: Located in the diencephalon, between the two halves of the thalamus. ○ Mesencephalic Aqueduct (Aqueduct of Sylvius): Narrow canal connecting the third and fourth ventricles, located in the midbrain. ○ Fourth Ventricle: Located between the brainstem and cerebellum. ○ Medial Aperture (of Magendie): Drains CSF from the fourth ventricle to the subarachnoid space. ○ Lateral Apertures (of Luschka): Paired openings for CSF drainage from the fourth ventricle. 2. Venous Flow from Sinuses to Jugular Vein: ○ Superior Sagittal Sinus → Confluence of Sinuses ○ Inferior Sagittal Sinus → Straight Sinus → Confluence of Sinuses ○ Confluence of Sinuses → Transverse Sinus → Sigmoid Sinus → Jugular Vein Structures to Know Septum Pellucidum: Thin membrane separating the lateral ventricles. Massa Intermedia: Connects the two thalamic halves (present in some individuals). CSF Production and Clinical Implications Choroid Plexus: Specialized tissue in the ventricles that produces CSF. ○ How CSF is Produced: Filtration of blood plasma through choroid plexus capillaries. ○ How CSF is Reabsorbed: Through arachnoid granulations into the superior sagittal sinus. Hydrocephalus: Excess CSF accumulation leading to ventricular enlargement. Blocked Interventricular Foramen: Enlargement of lateral ventricles upstream. Blocked Mesencephalic Aqueduct: Enlargement of third and lateral ventricles. CSF Leaks Through Dura: Intracranial hypotension, resulting in headaches. Other Structures  Falx Cerebri: Separates the two cerebral hemispheres; attaches to the crista galli. Tentorium Cerebelli: Separates the cerebellum from the occipital lobes. Middle Meningeal Artery: Supplies blood to the dura; located beneath the pterion. Cranial Bleeds 1. Epidural Hematoma ○ Bleed between the periosteal dura and skull. ○ Cause: Rupture of the middle meningeal artery. 2. Subdural Hematoma ○ Bleed between the dura mater and arachnoid mater. ○ Cause: Rupture of bridging veins. SPINAL CORD: Gray Matter 1. Posterior Horn: Processes sensory information. 2. Anterior Horn: Contains motor neurons that send axons to skeletal muscles. 3. Lateral Horn: Processes autonomic (sympathetic) information; present in thoracic and upper lumbar segments. White Matter 1. Posterior Funiculus: Contains ascending sensory tracts like the Fasciculus Gracilis (lower body sensory) and Fasciculus Cuneatus (upper body sensory). 2. Lateral Funiculus: Contains mixed tracts (e.g., Lateral Corticospinal Tract). 3. Anterior Funiculus: Contains mixed motor and sensory tracts (e.g., Anterior Corticospinal Tract). Hallmarks of Spinal Cord Segments 1. Cervical Enlargement: ○ Large anterior horns. ○ Increased white matter. ○ Supplies nerves to upper limbs. 2. Thoracic Segment: ○ Small anterior and posterior horns. ○ Presence of a lateral horn. ○ Smaller gray matter due to fewer limb muscles. 3. Lumbosacral Enlargement: ○ Enlarged anterior horns. ○ Dense gray matter for lower limb control. 4. Sacral Segment: ○ Smallest white matter. ○ Prominent gray matter. Tracts  1. Posterior Columns (PCML): ○ Modality: Fine touch, vibration, proprioception. ○ Cell Bodies: Dorsal root ganglia (ipsilateral). ○ Decussation: Medulla. ○ Target: Contralateral thalamus → somatosensory cortex. 2. Anterolateral System (ALS): ○ Modality: Pain, temperature, crude touch. ○ Cell Bodies: Dorsal horn (contralateral). ○ Decussation: Spinal cord (anterior white commissure). ○ Target: Thalamus → somatosensory cortex. 3. Posterior Spinocerebellar Tract: ○ Modality: Proprioception for lower limbs. ○ Cell Bodies: Dorsal nucleus of Clarke (ipsilateral). ○ Decussation: None. ○ Target: Ipsilateral cerebellum. 4. Lateral Corticospinal Tract: ○ Modality: Voluntary motor control. ○ Cell Bodies: Primary motor cortex. ○ Decussation: Pyramids of the medulla. ○ Target: Contralateral anterior horn. 5. Rubrospinal Tract: ○ Modality: Flexor muscle tone. ○ Cell Bodies: Red nucleus. ○ Decussation: Midbrain. ○ Target: Contralateral spinal cord. 6. Lateral Vestibulospinal Tract (LVST): ○ Modality: Posture and balance. ○ Cell Bodies: Vestibular nuclei (ipsilateral). ○ Decussation: None. ○ Target: Ipsilateral motor neurons. 7. Medial Vestibulospinal Tract (MVST): ○ Modality: Head and neck stabilization. ○ Cell Bodies: Vestibular nuclei. ○ Decussation: Partially in the medulla. ○ Target: Bilateral cervical spinal cord. 8. Reticulospinal Tracts (LRST and MRST): ○ Modality: Posture, locomotion, muscle tone. ○ Targets: Ipsilateral (LRST) or bilateral (MRST). Reflexes 1. Monosynaptic/Tendon Reflex: Direct synapse between sensory and motor neurons (e.g., patellar reflex). 2. Withdrawal Reflex: Polysynaptic; flexor response to noxious stimuli. 3. Cross-Extension Reflex: Opposite limb extends during withdrawal reflex. Structures to Locate on Gross Specimens 1. Cervical and Lumbosacral Enlargements: Areas with increased gray matter for limb control. 2. Anterior Median Fissure: Landmark for anterior spinal artery and organization. 3. Dentate Ligaments: Anchor spinal cord laterally. 4. Filum Terminale: Anchors spinal cord to coccyx. 5. Posterior Roots: Carry sensory information. 6. Anterior Roots: Carry motor information. 7. Cauda Equina: Bundle of lumbar and sacral nerve roots extending below the spinal cord. Atlas Sections Posterior Columns: Fasciculus gracilis (lower body), Fasciculus cuneatus (upper body). Anterior White Commissure: Allows fibers (e.g., ALS) to cross midline. Lateral Horn: Autonomic information (thoracic and lumbar). Intermediolateral Cell Column: Sympathetic preganglionic neurons. Arterial Blood Supply Anterior Spinal Artery: Supplies anterior two-thirds. Posterior Spinal Arteries: Supply posterior one-third. Radicular Arteries: Reinforce spinal arteries. SOMATOSENSATION: Types of Somatosensation Fast Somatosensation (large myelinated fibers, rapidly transmitted): 1. Discriminative touch: Fine touch for texture, shape, and two-point discrimination. 2. Vibration sense: Detection of oscillatory stimuli on the skin. 3. Proprioception: Awareness of body and joint position. Slow Somatosensation (smaller or unmyelinated fibers, slower transmission): 1. Temperature: Detection of warmth or cold. 2. Crude touch: Non-discriminative touch, like pressure. 3. Pain: Includes both fast (sharp pain) and slow (dull, aching pain). Structures (Atlas) and Their Functions 1. Medial Lemniscus (ML) ○ Function: Carries sensory information from the posterior column-medial lemniscus (PCML) pathway, specifically fine touch and proprioception. ○ Orientation of Homunculus: At the medulla: Feet are ventral, arms are dorsal. At the pons: Feet move laterally. At the midbrain: Feet are lateral, arms and face medial.  2. Nucleus Gracilis ○ Function: Processes sensory input from the lower body (below T6). 3. Nucleus Cuneatus ○ Function: Processes sensory input from the upper body (above T6). 4. Internal Arcuate Fibers ○ Function: Decussating fibers from the nucleus gracilis and nucleus cuneatus that form the medial lemniscus. 5. Lateral (Accessory) Cuneate Nucleus ○ Function: Relays proprioceptive information from the upper limbs to the cerebellum (part of the cuneocerebellar tract). 6. Spinal Nucleus of Trigeminal ○ Function: Processes pain and temperature sensation from the face. 7. Mesencephalic (Descending) Nucleus of Trigeminal ○ Function: Carries proprioceptive information from the face (e.g., jaw position). 8. Principal Nucleus of Trigeminal ○ Function: Processes fine touch and vibration from the face. Pathways 1. Posterior Column-Medial Lemniscus (PCML) Pathway ○ Modality: Fine touch, vibration, proprioception. ○ Crossing: Internal arcuate fibers (medulla). ○ Target: Ventral posterolateral nucleus (VPL) → Primary somatosensory cortex. 2. Posterior Spinocerebellar Tract ○ Modality: Proprioceptive information from the lower limbs. ○ Crossing: Does not cross. ○ Target: Cerebellum (ipsilateral). 3. Cuneocerebellar Tract ○ Modality: Proprioceptive information from the upper limbs. ○ Crossing: Does not cross. ○ Target: Cerebellum (ipsilateral). 4. Anterolateral System (ALS) ○ Modality: Pain, temperature, and crude touch. ○ Crossing: Anterior white commissure (spinal cord). ○ Target: Ventral posterolateral nucleus (VPL) → Primary somatosensory cortex. 5. Ventral Trigeminothalamic Tract (VTT) ○ Modality: Pain, temperature, and touch from the face. ○ Crossing: Brainstem (midline). ○ Target: Ventral posteromedial nucleus (VPM). Key Nuclei 1. Ventral Posterolateral Nucleus (VPL) ○ Function: Relays somatosensory information from the body to the primary somatosensory cortex. 2. Ventral Posteromedial Nucleus (VPM)  ○ Function: Relays somatosensory information from the face to the primary somatosensory cortex. Primary Somatosensory Cortex (Post-Central Gyrus) Location: Parietal lobe, posterior to the central sulcus. Homunculus Orientation: ○ Medial: Legs/feet. ○ Middle: Arms/hands. ○ Lateral: Face/mouth. Sensory Ataxia Definition: Loss of coordination caused by impaired sensory input (e.g., proprioception). Symptoms: Difficulty maintaining balance with eyes closed (positive Romberg test). MOTOR SYSTEMS GENERAL: Be able to locate on gross specimens, atlas sections or both. Know their purpose/function, what information is carried processed. o Pyramidal tract o Inferior Olivary nucleus o Crus cerebri (cerebral peduncles) o Internal Capsule ▪ Anterior limb – what information is carried here? ▪ Posterior limb– what information is carried here? ▪ Genu – what information is carried here? o Motor nucleus of trigeminal o Lateral corticospinal tract o Corticobulbar fibers o Rubrospinal tract o Reticulospinal tracts (LRST & MRST) o Vestibulospinal tracts (LVST & MVST) o Red nucleus o Vestibular nuclei o Reticular formation o Medial Longitudinal Fasciculus (MLF) ▪ Descending to spinal lower motor neurons (LMNs) ▪ Ascending to cranial nerve lower motor neurons (LMNs) What is Motor Ataxia? What is the function of the primary motor cortex? o What is the orientation of the homunculus? What is the function of the pre-motor cortex? Describe what the final common pathway is for LMNs. What arteries supply blood to the internal capsule? Where are the cell bodies of LMNs that innervate flexor muscles in the anterior horn? Where are the cell bodies of LMNs that innervate extensor muscles in the anterior horn?  Where are the cell bodies of LMNs that innervate distal muscles in the anterior horn? Where are the cell bodies of LMNs that innervate proximal muscles in the anterior horn? Define the following motor disorders: o Tremors o Apraxia o Tardive Dyskinesia o Tics/Tourette’s Syndrome Motor Systems Structures to Locate (Gross Specimens/Atlas) 1. Pyramidal Tract ○ Function: Major descending pathway carrying voluntary motor commands. ○ Information: Upper motor neuron (UMN) axons for corticospinal and corticobulbar tracts. 2. Inferior Olivary Nucleus ○ Function: Relays sensory and motor information to the cerebellum for coordination. ○ Location: Medulla. 3. Crus Cerebri (Cerebral Peduncles) ○ Function: Contains corticospinal and corticobulbar fibers descending from the motor cortex. 4. Internal Capsule ○ Function: Major white matter structure connecting the cerebral cortex to subcortical regions. ○ Divisions: Anterior limb: Carries frontopontine and thalamocortical fibers (motor planning). Genu: Carries corticobulbar fibers (motor control of cranial nerves). Posterior limb: Carries corticospinal fibers (motor control of the body) and thalamocortical sensory fibers. 5. Motor Nucleus of Trigeminal ○ Function: Innervates muscles of mastication. ○ Location: Pons. 6. Lateral Corticospinal Tract ○ Function: Controls voluntary movement of limbs. ○ Crossing: Decussates in the medullary pyramids. 7. Corticobulbar Fibers ○ Function: UMN fibers controlling cranial nerve motor nuclei. 8. Rubrospinal Tract ○ Function: Facilitates flexor muscles and inhibits extensor muscles (fine motor control). ○ Crossing: Decussates in the midbrain (red nucleus). 9. Reticulospinal Tracts ○ Lateral Reticulospinal Tract (LRST): Inhibits extensor reflexes. ○ Medial Reticulospinal Tract (MRST): Facilitates extensor reflexes. 10. Vestibulospinal Tracts ○ Lateral (LVST): Facilitates extensor tone to maintain posture. ○ Medial (MVST): Controls head and neck position. 11. Red Nucleus ○ Function: Origin of rubrospinal tract; coordinates flexor activity.  12. Vestibular Nuclei ○ Function: Origin of vestibulospinal tracts; involved in balance and posture. 13. Reticular Formation ○ Function: Motor, autonomic, and arousal control. 14. Medial Longitudinal Fasciculus (MLF) ○ Function: Descending: Coordinates head/eye movements via vestibulospinal tracts. Ascending: Coordinates gaze control via cranial nerves. Other Concepts 1. Motor Ataxia ○ Definition: Incoordination caused by motor system dysfunction, often due to cerebellar damage. 2. Primary Motor Cortex ○ Function: Executes voluntary motor commands. ○ Homunculus Orientation: Medial: Lower limbs. Middle: Upper limbs. Lateral: Face and mouth. 3. Pre-Motor Cortex ○ Function: Plans and coordinates complex movements. 4. Final Common Pathway ○ Definition: Lower motor neurons (LMNs) that directly innervate skeletal muscles. Blood Supply Internal Capsule: Supplied by the lenticulostriate arteries (branches of the middle cerebral artery) and anterior choroidal artery. LMN Cell Body Locations in the Anterior Horn 1. Flexor Muscles: Posterior portion of the anterior horn. 2. Extensor Muscles: Anterior portion of the anterior horn. 3. Distal Muscles: Lateral portion of the anterior horn. 4. Proximal Muscles: Medial portion of the anterior horn. Motor Disorders 1. Tremors  ○ Definition: Involuntary rhythmic oscillations of a body part. ○ Types: Resting, postural, or intention tremors. 2. Apraxia ○ Definition: Inability to perform purposeful movements despite normal strength and coordination. 3. Tardive Dyskinesia ○ Definition: Involuntary repetitive movements, often caused by long-term use of antipsychotic medications. 4. Tics/Tourette’s Syndrome ○ Definition: Sudden, repetitive, involuntary movements or vocalizations. ○ Associated with: Basal ganglia dysfunction. AUDITORY SYSTEM: Be able to locate on gross specimens, atlas sections or both. Know their purpose/function, what information is carried processed. o Inferior colliculus o Brachium of inferior colliculus o Medial geniculate body/complex o Transverse temporal gyrus (primary auditory cortex) o Cochlear nucleus o Lateral lemniscus Review the pathway drawn in lecture. KNOW THIS PATHWAY!! Define sound What is the function of the following and what is it comprised of: o External ear o Middle ear o Inner ear o Tympanic membrane o Cochlea o Organ of Corti How is frequency coded? What is the tonotopic map? How is sound localized? o Interaural level difference o Interaural timing difference Deafness: o Conduction o Sensorineural o Based on the auditory pathway, know if a patient will experience deafness if each component is lesioned. Aphasia: o Wernicke’s – Where is Wernicke’s area? What symptoms would you see? o Broca’s – Where is Broca’s area? What symptoms would you see? Auditory System Structures to Locate (Gross Specimens/Atlas) 1. Inferior Colliculus ○ Function: Integration and processing of auditory signals; relays auditory information to the thalamus. ○ Location: Midbrain. 2. Brachium of Inferior Colliculus ○ Function: Connects the inferior colliculus to the medial geniculate body (MGB). 3. Medial Geniculate Body/Complex (MGB) ○ Function: Thalamic relay for auditory information to the auditory cortex. ○ Location: Thalamus. 4. Transverse Temporal Gyrus (Primary Auditory Cortex) ○ Function: Processes auditory input for perception of pitch, tone, and speech. ○ Location: Superior temporal gyrus. 5. Cochlear Nucleus ○ Function: First processing station in the auditory pathway, located in the medulla. ○ Information: Processes timing and intensity of auditory signals. 6. Lateral Lemniscus ○ Function: Major ascending auditory pathway from cochlear nuclei to the inferior colliculus. Auditory Pathway (Know This Pathway) 1. Cochlea → Cochlear Nucleus (medulla). 2. → Superior Olivary Complex (pons): First site of binaural input. 3. → Lateral Lemniscus (pons/midbrain): Conveys auditory information. 4. → Inferior Colliculus (midbrain): Integrates and processes signals. 5. → Medial Geniculate Body (thalamus): Relays to the cortex. 6. → Primary Auditory Cortex (transverse temporal gyrus): Perception and processing. Sound Definition: Vibrations transmitted through air or another medium, perceived as auditory signals. Functions and Components 1. External Ear ○ Function: Collects and funnels sound waves to the tympanic membrane. ○ Components: Pinna, auditory canal. 2. Middle Ear  ○ Function: Amplifies sound waves via ossicles (malleus, incus, stapes). ○ Components: Tympanic membrane, ossicles, eustachian tube. 3. Inner Ear ○ Function: Converts sound waves into electrical signals via hair cells in the cochlea. ○ Components: Cochlea, semicircular canals, vestibule. 4. Tympanic Membrane ○ Function: Vibrates in response to sound waves, transmitting vibrations to the ossicles. 5. Cochlea ○ Function: Contains hair cells that transduce sound vibrations into neural signals. 6. Organ of Corti ○ Function: Contains hair cells responsible for detecting frequency and intensity of sound. Coding and Localization 1. Frequency Coding ○ Mechanism: Hair cells in different regions of the cochlea respond to specific frequencies. ○ Base: High frequencies. ○ Apex: Low frequencies. 2. Tonotopic Map ○ Definition: Spatial arrangement of hair cells in the cochlea that corresponds to specific frequencies. 3. Sound Localization ○ Mechanisms: Interaural Level Difference (ILD): Compares sound intensity between ears (useful for high frequencies). Interaural Timing Difference (ITD): Compares time of arrival of sound waves at each ear (useful for low frequencies). Deafness Types 1. Conduction Deafness ○ Cause: Impaired transmission through the external or middle ear. ○ Example: Otosclerosis, tympanic membrane perforation. 2. Sensorineural Deafness ○ Cause: Damage to hair cells, cochlear nerve, or central auditory pathways. ○ Example: Noise-induced hearing loss, presbycusis. Auditory Pathway Lesion Effects 1. Unilateral Cochlear Nerve Lesion: Complete deafness in the affected ear.  2. Lesion Beyond Cochlear Nuclei: Reduced localization ability but no complete deafness (bilateral processing). Aphasia 1. Wernicke’s Aphasia ○ Location: Wernicke’s area (posterior superior temporal gyrus). ○ Symptoms: Fluent but nonsensical speech. Difficulty understanding spoken or written language. 2. Broca’s Aphasia ○ Location: Broca’s area (posterior inferior frontal gyrus). ○ Symptoms: Non-fluent speech with intact comprehension. Difficulty producing grammatically correct sentences. VESTIBULAR SYSTEM: Be able to locate on gross specimens: o Cranial Nerve 3 o Cranial Nerve 4 o Cranial Nerve 6 o Cranial Nerve 8 Be able to locate on atlas sections: o Nuclei associated with CN 3, 4, 6, 8 o Medial longitudinal fasciculus o Vestibular nuclei o LVST & MVST o Anterior horn of spinal cord What is the purpose for the VOR? o Why is it important? Be able to draw out the VOR o Be able to explain symptoms we would expect if any part of the VOR is lesioned. What is the Vestibulocollic reflex? o It is mediated by which tract? o Know the basic pathway for this reflex. What is the Vestibulospinal Reflex? o Is it mediated by which tract? o Know the basic pathway for this reflex. What is the importance of the basal activity of the vestibular system? The slow phase of nystagmus is controlled by what? The fast phase of nystagmus is controlled by what? Nystagmus is named after which phase? What is Romberg Test? What are the functions of the vestibular system?  What is the bony labyrinth? o It is filled with what fluid? What is the membranous labyrinth? o It is filled with what fluid? What are the properties of Hair cells? o The hair bundle is surrounded by what fluid? o The cell body is surrounded by what fluid? o What maintains the barrier between endolymph and perilymph? o Hair cells release what neurotransmitter? o The hair cell will DEPOLARIZE if the hair bundle moves towards/away (pick one) from the stereocilia. o The hair cell will HYPERPOLARIZE if the hair bundle moves towards/away (pick one) from the stereocilia. Semicircular canals contain hair cells that respond to what kind of acceleration? What is the cupula/gelatinous mass? The otolith organs are made up of what two structures? The utricle detects what kind of acceleration? The saccule detects what kind of acceleration? Vestibular System Overview: Cranial Nerves: CN 3 (Oculomotor Nerve): Controls eye movement (most extraocular muscles), pupil constriction, and accommodation. CN 4 (Trochlear Nerve): Controls the superior oblique muscle, which moves the eye downward and inward. CN 6 (Abducens Nerve): Controls the lateral rectus muscle, which abducts the eye (moves it outward). CN 8 (Vestibulocochlear Nerve): Carries sensory information for both hearing (cochlear division) and balance (vestibular division). Atlas Sections: Nuclei associated with CN 3, 4, 6, 8: ○ The oculomotor nucleus (CN 3) is located in the midbrain. ○ The trochlear nucleus (CN 4) is located in the midbrain (in the inferior colliculus). ○ The abducens nucleus (CN 6) is located in the pons. ○ The vestibular nuclei (CN 8) are located in the pons and medulla. Medial Longitudinal Fasciculus (MLF): A pathway that connects the nuclei of CN 3, 4, and 6 to coordinate eye movements, especially during gaze shifts. Vestibular Nuclei: Includes four main nuclei (superior, medial, lateral, and inferior), which are involved in processing information related to balance and head position. LVST & MVST: These tracts (Lateral Vestibulospinal Tract and Medial Vestibulospinal Tract) are involved in motor control, with LVST facilitating balance and MVST controlling head movements. Anterior Horn of Spinal Cord: Contains motor neurons responsible for voluntary muscle movement. Vestibulo-Ocular Reflex (VOR): Purpose: The VOR stabilizes the visual field during head movements by producing compensatory eye movements. Importance: It is crucial for maintaining stable vision during dynamic movements (e.g., when walking or running). Draw out the VOR: ○ When the head turns in one direction, the VOR causes the eyes to move in the opposite direction to stabilize the visual field. Symptoms of VOR Lesion: If the VOR is disrupted, the individual may experience blurry vision or difficulty focusing on objects during head movement. Reflexes: Vestibulocollic Reflex (VCR): ○ Mediated by the Medial Vestibulospinal Tract (MVST). ○ Pathway: Involves vestibular input influencing neck muscles to stabilize the head in response to changes in posture or head movements. Vestibulospinal Reflex (VSR): ○ Mediated by the Lateral Vestibulospinal Tract (LVST). ○ Pathway: Vestibular signals project to spinal cord motor neurons to adjust posture and balance by activating extensor muscles and inhibiting flexor muscles. Basal Activity of the Vestibular System: The vestibular system is always active, even in the absence of motion, to provide a sense of balance and maintain posture. This basal activity helps the body to adapt to changes in head position and accelerations. Nystagmus: Slow phase: Controlled by the vestibular system to initiate smooth eye movement. Fast phase: Controlled by the brainstem to reset the eyes. Naming Nystagmus: Nystagmus is named based on the direction of the fast phase. Romberg Test: A clinical test used to assess balance. The patient stands with feet together and eyes closed. A positive test (loss of balance) suggests vestibular dysfunction. Functions of the Vestibular System: 1. Balance and Posture: Provides information about head position and movement to maintain balance and adjust posture. 2. Eye Movement Control: Coordinates eye movements (e.g., VOR) to stabilize vision during head movements. Bony vs. Membranous Labyrinth:  Bony Labyrinth: The rigid outer structure within the temporal bone that houses the vestibular system and cochlea. It is filled with perilymph. Membranous Labyrinth: A soft, fluid-filled structure within the bony labyrinth that contains sensory organs for hearing and balance. It is filled with endolymph. Hair Cells: Properties: Sensory receptors in the vestibular system that detect head movement. When deflected by movement, they generate electrical signals. Hair bundle surroundings: Surrounded by endolymph in the membranous labyrinth. Cell body surroundings: Surrounded by perilymph in the bony labyrinth. Mechanism of Hair Cell Activity: Depolarization: Occurs when the hair bundle moves towards the stereocilia. Hyperpolarization: Occurs when the hair bundle moves away from the stereocilia. Neurotransmitter Release: Hair cells release glutamate to transmit information to the afferent neurons. Semicircular Canals: Function: Detect angular acceleration (rotational movement of the head). Cupula: A gelatinous mass in the semicircular canals that moves in response to fluid flow, deflecting the hair cells. Otolith Organs: Structures: Utricle and saccule. Utricle: Detects horizontal acceleration. Saccule: Detects vertical acceleration. VISUAL SYSTEM: What are the properties of light? What are the layers of the eye from outside to inside? What is the optic disc? o What type of cells are missing here? What is the fovea? What produces aqueous humor? What is the function of aqueous humor? o Blockage of aqueous humor can lead to what? How does the shape of the lens change when objects are far/close to eye? Define the following: o Hyperopia o Myopia o Astigmatism What is the function of the iris?  o Reflexes of the iris are mediated by which cranial nerves? Define the following: o Photoreceptor cells o Bipolar cells – where are their receptive fields large and small? o Retinal ganglion cells – where are their receptive fields large and small? o Horizontal cells o Amacrine cells What are the properties of cones? o What are the 3 types of cones? o Explain how colorblindness happens. What are the properties of rods? Know the transduction pathway (review the diagram from class) Bipolar cells respond to what neurotransmitter that is released by what cells? What is the difference between ON BPCs and OFF BPCs? Horizontal cells respond to which neurotransmitter from which cells? o Where do HCs project to? What neurotransmitter do HCs release? How does our visual system process edges? Where do retinal ganglion cells project to? (hint: there are 4 places) Review how the different visual FIELDS are processed o Nasal retina vs temporal retina o Know the diagram that was drawn in lab (from retina to primary visual cortex) Magno RGCs are concerned with what kind of information? Parvo RGCs are concerned with what kind of information? The lateral geniculate nucleus contain show many layers? o Layers 1, 4 and 6 process information from where? o Layers 2, 3 and 5 process information from where? Explain optic radiation and what information is carried in which fibers. Where is the primary visual cortex? What anatomical structure is involved in the primary motor cortex? What is the difference between the dorsal and ventral stream? Be able to locate the following structures: o Optic nerve o Optic chiasm o Optic tract o Lateral geniculate nucleus o Primary visual cortex ▪ Calcarine sulcus What are the two types of eye movements? What are saccades? o When are they used? o Review the flow chart from class What are smooth pursuit? o When are they used? o Review the flow chart from class How do vergence eye movements work? Visual System Overview: Properties of Light: Wavelength: Determines the color of light. Amplitude: Affects brightness. Frequency: Determines the pitch (in the context of sound) but also correlates with the energy and color in light. Refraction: The bending of light as it passes through different mediums (important for focusing light on the retina). Layers of the Eye (from outside to inside): 1. Cornea (transparent outer layer, helps focus light). 2. Aqueous humor (fluid-filled chamber between cornea and lens). 3. Lens (focuses light onto retina). 4. Vitreous humor (gel-like substance that maintains eye shape and transmits light). 5. Retina (light-sensitive layer at the back of the eye). 6. Optic nerve (transmits visual information to the brain). The Optic Disc: Definition: The point where the optic nerve exits the retina, often referred to as the "blind spot" because it lacks photoreceptors (rods and cones). The Fovea: Definition: A small, central part of the retina where visual acuity is highest. It contains a high density of cones, enabling detailed color vision. Aqueous Humor: Produced by: The ciliary body. Function: Provides nutrients to the avascular structures (cornea and lens) and helps maintain intraocular pressure. Blockage of aqueous humor: Can lead to glaucoma, a condition where increased intraocular pressure damages the optic nerve. Shape of the Lens: For distant objects: The lens flattens. For close objects: The lens becomes more rounded (accommodation) to focus light on the retina. Defining Common Refractive Errors: Hyperopia (Farsightedness): The eye is too short, causing difficulty focusing on nearby objects. Myopia (Nearsightedness): The eye is too long, causing difficulty focusing on distant objects. Astigmatism: The cornea or lens is irregularly shaped, leading to blurred vision. Function of the Iris: The iris controls the size of the pupil, regulating the amount of light entering the eye. Reflexes of the iris are mediated by CN 2 (optic nerve) and CN 3 (oculomotor nerve). Retinal Cells and Their Functions: Photoreceptor Cells (Rods and Cones): Convert light into electrical signals. Bipolar Cells (BPCs): Located between photoreceptors and retinal ganglion cells. ○ Receptive Fields: Larger in peripheral areas, smaller in the fovea for precise vision. Retinal Ganglion Cells (RGCs): Receive input from bipolar cells and send visual information to the brain. ○ Receptive Fields: Larger in the periphery, smaller in the fovea. Horizontal Cells: Modify the signal between photoreceptors and bipolar cells, contributing to contrast and edge detection. Amacrine Cells: Involved in processing motion and contrast by modulating the output of bipolar cells. Cones: Properties: Responsible for color vision, require brighter light to function. Types of Cones: 1. S-cones (short): Sensitive to blue light. 2. M-cones (medium): Sensitive to green light. 3. L-cones (long): Sensitive to red light. Colorblindness: Cause: A genetic mutation in the genes encoding for the photopigments of cones, typically affecting red or green cones, leading to difficulty distinguishing certain colors. Rods: Properties: Responsible for vision in dim light, do not detect color. Function: Better for peripheral vision and motion detection. Transduction Pathway: Light hits the photoreceptor cells (rods or cones), causing a chemical change in photopigments. This activates a cascade involving cGMP and Na⁺ channels, leading to the hyperpolarization of photoreceptors. This signal is transmitted to bipolar cells and then to retinal ganglion cells. Neurotransmission in the Retina: Bipolar cells: Respond to glutamate released by photoreceptor cells. ON vs. OFF Bipolar Cells (BPCs): ○ ON BPCs: Depolarize in response to light (active when light levels increase). ○ OFF BPCs: Depolarize in darkness (active when light levels decrease).  Horizontal Cells: Respond to glutamate and release GABA, modulating the response of adjacent photoreceptors. Processing Edges: The visual system enhances edges by utilizing horizontal cells' lateral inhibition, which sharpens contrast between light and dark areas. Retinal Ganglion Cell Projections: Where they project: 1. Lateral Geniculate Nucleus (LGN) of the thalamus – primary relay for visual information. 2. Superior colliculus – involved in visual reflexes. 3. Pretectal area – involved in pupillary light reflex. 4. Suprachiasmatic nucleus – involved in circadian rhythms. Visual Fields: Nasal retina vs. Temporal retina: ○ Nasal retina: Information from the peripheral part of the visual field, crosses at the optic chiasm. ○ Temporal retina: Information from the central part of the visual field, does not cross at the optic chiasm. Magno vs. Parvo RGCs: Magno RGCs: Concerned with motion and spatial location (larger receptive fields). Parvo RGCs: Concerned with fine detail and color vision (smaller receptive fields). Lateral Geniculate Nucleus (LGN): 6 layers in total: ○ Layers 1, 4, 6: Process information from the contralateral retina. ○ Layers 2, 3, 5: Process information from the ipsilateral retina. Optic Radiation: Fibers carry information from the LGN to the primary visual cortex. ○ Upper fibers: Carry information from the lower visual field (via the temporal lobe). ○ Lower fibers: Carry information from the upper visual field (via the parietal lobe). Primary Visual Cortex (V1): Located in the occipital lobe along the calcarine sulcus. It is the first area to process visual information. Dorsal vs. Ventral Stream: Dorsal Stream (Where): Involved in spatial processing, motion detection, and object localization. Ventral Stream (What): Involved in object recognition and identification. Eye Movements: Two types: 1. Saccades: Rapid, jerky movements of the eye that occur when shifting focus to a new target. 2. Smooth Pursuit: Continuous, smooth movements that track a moving target. Vergence Movements: The eyes move towards or away from each other to maintain focus on a near or far object, respectively. Visual Pathway from Retina to Primary Visual Cortex: 1. Light enters the eye and is focused on the retina. 2. Photoreceptors (rods and cones) convert light into electrical signals. 3. Bipolar cells transmit the signal to retinal ganglion cells. 4. The axons of RGCs form the optic nerve. 5. At the optic chiasm, fibers from the nasal retina cross. 6. The fibers travel along the optic tract and synapse in the LGN of the thalamus. 7. Visual information is transmitted through the optic radiation to the primary visual cortex (V1) in the occipital lobe. GUSTATORY SYSTEM: GUSTATORY SYSTEM 1. What 3 things contribute to flavor? ○ Taste: Detected by taste receptors on the tongue. ○ Smell: Olfactory receptors contribute significantly to flavor perception. ○ Texture: The feel of the food, which includes temperature and mouthfeel, plays a role in flavor perception. 2. Define taste. ○ Taste refers to the sensory perception produced when certain chemicals in food interact with receptors on the taste buds of the tongue, triggering signals to the brain. 3. What are the 5 tastes that we can sense with our taste cells? ○ Sweet ○ Sour ○ Salty ○ Bitter ○ Umami 4. What are their modalities? ○ Sweet: Associated with sugars and energy-rich molecules. ○ Sour: Caused by the presence of hydrogen ions (H+), typically from acidic substances. ○ Salty: Resulting from the presence of sodium ions (Na+). ○ Bitter: Often associated with potentially toxic compounds; typically detected by receptors for alkaloids.  ○ Umami: Caused by glutamate and other amino acids, typically linked to the savory taste of protein-rich foods. 5. The anterior 2/3 of the tongue contains what kind of papillae? With how many taste buds? ○ Type of papillae: Fungiform papillae. ○ Taste buds: These papillae contain around 1-5 taste buds each. 6. Taste buds that are innervated by which cranial nerve? ○ Cranial nerve: The facial nerve (VII) innervates the taste buds of the anterior two-thirds of the tongue. 7. The lateral back of the tongue contains what kind of papillae? With how many taste buds? ○ Type of papillae: Foliate papillae. ○ Taste buds: Each foliate papilla contains around 100 taste buds. 8. Taste buds that are innervated by which cranial nerve? ○ Cranial nerve: The glossopharyngeal nerve (IX) innervates the taste buds on the posterior third of the tongue. 9. The central back of the tongue contains what kind of papillae? With how many taste buds? ○ Type of papillae: Circumvallate papillae. ○ Taste buds: Each circumvallate papilla contains around 100-200 taste buds. 10. Taste buds that are innervated by which cranial nerve? ○ Cranial nerve: The glossopharyngeal nerve (IX) innervates these taste buds as well. 11. The pharynx contains taste buds that are innervated by which cranial nerve? ○ Cranial nerve: The glossopharyngeal nerve (IX) and the vagus nerve (X) innervate taste buds in the pharynx. 12. The palate contains taste buds that are innervated by which cranial nerve? ○ Cranial nerve: The facial nerve (VII) innervates taste buds on the soft palate. 13. Be able to draw out the taste bud/cell (diagram drawn in class) with different taste cell types. ○ Types of taste cells: Type I cells: Supportive cells. Type II cells: Receptor cells that respond to sweet, bitter, and umami tastes via G-protein-coupled receptors (GPCRs). Type III cells: Presynaptic cells that respond to sour and salty tastes and transmit signals to afferent neurons. 14. What are the two main transduction mechanisms? ○ Ion channels: Activated by salty and sour tastes, causing depolarization of the taste receptor cell. ○ G-protein-coupled receptors (GPCRs): Activated by sweet, bitter, and umami tastes, leading to intracellular signaling cascades. 15. Which receptor proteins encode the sweet taste? ○ Sweet receptors are primarily encoded by the T1R2 and T1R3 receptors. 16. Which receptor proteins encode the umami taste? ○ Umami receptors are primarily encoded by the T1R1 and T1R3 receptors. 17. Which receptor proteins encode the bitter taste? ○ Bitter receptors are encoded by the T2R family of receptors, which respond to a wide variety of bitter compounds. 18. Be able to explain the gustatory pathway. ○ Gustatory pathway involves the following steps:  Taste stimuli are detected by taste receptor cells on the tongue and other areas. The sensory information is transmitted via the facial nerve (VII) (anterior 2/3 of the tongue), the glossopharyngeal nerve (IX) (posterior 1/3 of the tongue), and the vagus nerve (X) (pharynx and palate). These afferent nerves send signals to the solitary nucleus in the brainstem. The information is then relayed to the thalamus, specifically the ventral posterior medial nucleus. Finally, taste information is processed in the gustatory cortex, located in the insula of the brain. 19. Be able to locate the structures that are involved in the pathway. ○ Taste receptors (on tongue and palate) ○ Cranial nerves: VII, IX, X ○ Solitary nucleus (in brainstem) ○ Thalamus (ventral posterior medial nucleus) ○ Gustatory cortex (insula) OLFACTORY SYSTEM: Olfactory receptor neurons are located where? Axons from ORNs for what cranial nerve? o This cranial nerve enters the CNS by protruding through what structure? o These axons synapse where? (include laterality) Be able to draw out the olfactory pathway (seen in lecture notes) Does the olfactory pathway include thalamic relay? How can head trauma affect olfaction? How can viruses/bacteria affect olfaction? ORNs have what kind of receptors? How does transduction occur? How is olfaction coded? Define the following: o Anosmia o Hyposmia Olfactory receptor neurons (ORNs) are located where? o Olfactory receptor neurons are located in the olfactory epithelium of the nasal cavity, specifically in the upper part of the nasal cavity. Axons from ORNs for what cranial nerve? o The axons from olfactory receptor neurons form cranial nerve I (olfactory nerve). This cranial nerve enters the CNS by protruding through what structure? o The olfactory nerve enters the CNS by passing through the cribriform plate of the ethmoid bone. These axons synapse where? (Include laterality) o The axons of the olfactory nerve synapse in the olfactory bulb, located just above the cribriform plate. The olfactory bulbs are located bilaterally (on both sides of the brain), and axons from both sides converge here. Be able to draw out the olfactory pathway (seen in lecture notes):  o Olfactory Pathway: ▪ Olfactory receptor neurons in the nasal epithelium. ▪ Olfactory nerve (CN I) axons through the cribriform plate. ▪ Synapse in the olfactory bulb. ▪ Olfactory tract (comprising the axons from the olfactory bulb). ▪ Olfactory cortex (primary olfactory cortex, including the piriform cortex, entorhinal cortex, and parts of the amygdala). ▪ Olfactory information can be processed further in the orbitofrontal cortex for perception of smell. Does the olfactory pathway include thalamic relay? o No, the olfactory pathway does not include a thalamic relay. Olfactory signals are unique in that they bypass the thalamus and project directly to the olfactory cortex. How can head trauma affect olfaction? o Head trauma can cause olfactory dysfunction or anosmia due to damage to the olfactory nerve (CN I) as it passes through the cribriform plate. This can lead to the loss of the sense of smell. How can viruses/bacteria affect olfaction? o Viruses (such as COVID-19) and bacteria (such as in sinus infections) can damage the olfactory receptor neurons or olfactory epithelium, leading to anosmia or hyposmia. They can also cause inflammation or blockage in the nasal passages, impairing olfactory function. ORNs have what kind of receptors? How does transduction occur? o Olfactory receptor neurons have G-protein coupled receptors (GPCRs) that are specific to different odorant molecules. When an odorant binds to these receptors, it activates a G-protein signaling cascade that increases cyclic AMP (cAMP) levels, which in turn opens ion channels (such as sodium and calcium channels), causing depolarization of the olfactory receptor neuron and generating an action potential. How is olfaction coded? o Olfactory coding occurs via temporal and spatial patterns of action potentials. Different combinations of receptors are activated by different odorants, and the brain interprets the specific pattern of activity across the olfactory receptor neurons to perceive distinct smells. Each odorant activates a specific set of receptors, leading to unique patterns of neural firing that are mapped in the olfactory cortex. Definitions: Anosmia: Complete loss of the sense of smell. It can be caused by head trauma, viral infections, or damage to the olfactory system. Hyposmia: Reduced sense of smell or partial loss of olfaction. It can occur due to aging, nasal congestion, infections, or other factors affecting the olfactory system. AUTONOMIC NERVOUS SYSTEM What are the functions of the ANS? The ANS is controlled by what?  What are the 3 division of the ANS? What effects does the sympathetic and parasympathetic NS have on: o Heart rate o Blood pressure o Blood flow to muscles o Blood flow to guts o Digestions o Pupils Visceral afferents enter the CNS via which cranial nerves? o Then, axons run in which tract? Where do visceral efferents project to? Where are the cell bodies of sympathetic neurons found? Compare and contrast the Sympathetic and Parasympathetic NS o Where is the ganglion located? o Where are the preganglionic neurons located? o The preganglionic neuron releases what NT? o The postganglionic neurons releases what NT? o What kind of divergence does each system have? o What kind of effects does each system have? Functions of the Autonomic Nervous System (ANS): The ANS regulates involuntary physiological processes, including: Heart rate and blood pressure Respiratory rate Digestion and gastrointestinal motility Pupil dilation and constriction Urination and sexual arousal Sweating and body temperature regulation Blood flow distribution Control of the ANS: The ANS is primarily controlled by the hypothalamus, which coordinates autonomic responses via input from higher brain centers (e.g., cerebral cortex) and afferent input from the body. The brainstem (especially the medulla and pons) also plays a key role in regulating autonomic functions. Three Divisions of the ANS: 1. Sympathetic Nervous System (SNS): Often associated with the "fight or flight" response. 2. Parasympathetic Nervous System (PNS): Associated with "rest and digest" functions. 3. Enteric Nervous System (ENS): Often considered a "second brain," it governs the gastrointestinal system. Effects of the Sympathetic and Parasympathetic Nervous Systems: Sympathetic Nervous System (SNS): Heart rate: Increases (tachycardia) Blood pressure: Increases (due to vasoconstriction) Blood flow to muscles: Increases (via vasodilation of skeletal muscle blood vessels) Blood flow to guts: Decreases (via vasoconstriction of gastrointestinal vessels) Digestion: Inhibits digestion Pupils: Dilates (mydriasis) Parasympathetic Nervous System (PNS): Heart rate: Decreases (bradycardia) Blood pressure: Decreases (due to vasodilation) Blood flow to muscles: Decreases Blood flow to guts: Increases (supports digestion) Digestion: Stimulates digestion Pupils: Constricts (miosis) Visceral Afferents Entering the CNS: Visceral afferents (sensory fibers) enter the CNS primarily via cranial nerves VII, IX, and X (facial, glossopharyngeal, and vagus nerves), and spinal nerves (especially through the dorsal roots). Axon Pathways of Visceral Afferents: After entering the CNS, visceral afferents ascend in the solitary tract, which projects to the brainstem and other regions of the CNS for processing. Visceral Efferents: Visceral efferents (motor fibers) project to smooth muscles, cardiac muscles, and glands throughout the body. Location of Sympathetic Neuron Cell Bodies: Sympathetic preganglionic neurons are located in the lateral horn of the spinal cord between T1 and L2 (thoracolumbar region). The sympathetic ganglia are located in the sympathetic chain and prevertebral ganglia. Sympathetic vs. Parasympathetic Nervous System: Sympathetic Nervous System: Ganglion location: Sympathetic chain ganglia (near the spinal cord) and prevertebral ganglia. Preganglionic neurons: Located in the thoracolumbar spinal cord (T1-L2). Neurotransmitter at preganglionic synapse: Acetylcholine (Ach). Neurotransmitter at postganglionic synapse: Norepinephrine (NE) (except for sweat glands, where Ach is used).  Divergence: High divergence, as a single preganglionic fiber may synapse with many postganglionic neurons, allowing for widespread effects. Effects: "Fight or flight" responses, promoting alertness, energy expenditure, and readiness for physical activity. Parasympathetic Nervous System: Ganglion location: Near or within target organs (e.g., cardiac, digestive). Preganglionic neurons: Located in the brainstem (cranial nerves III, VII, IX, and X) and sacral spinal cord (S2-S4). Neurotransmitter at preganglionic synapse: Acetylcholine (Ach). Neurotransmitter at postganglionic synapse: Acetylcholine (Ach). Divergence: Lower divergence compared to the sympathetic system, resulting in more localized and specific effects. Effects: "Rest and digest" responses, promoting relaxation, energy conservation, and restoration of body functions. Additional Points: Ganglion location: Sympathetic ganglia are near the spinal cord (sympathetic chain), while parasympathetic ganglia are near or within target organs. Preganglionic neurons: Sympathetic preganglionic neurons are in the thoracolumbar spinal cord, while parasympathetic preganglionic neurons are in the brainstem and sacral spinal cord. Neurotransmitters: Both systems use acetylcholine at the preganglionic synapse. However, the sympathetic system primarily uses norepinephrine at the postganglionic synapse (with the exception of sweat glands), while the parasympathetic system uses acetylcholine throughout. CRANIAL NERVES: CRANIAL NERVES: Cranial Nerve 1: Olfactory Nerve Pathways of Olfactory Information: Olfactory receptors in the nasal cavity send axons to the olfactory bulb, where they synapse. Axons from the bulb form the olfactory tract, which projects to the olfactory cortex and limbic system. Location: Olfactory bulb and tract are located on the inferior side of the frontal lobe, above the nasal cavity. Cranial Nerve 2: Optic Nerve Pathways of Visual Information: Visual information from the retina travels via the optic nerve, crosses at the optic chiasm (partial decussation), and then travels via the optic tract to the lateral geniculate nucleus of the thalamus, from where it is sent to the visual cortex. Location: The optic nerve can be seen exiting the eye, and the optic chiasm is located at the base of the brain, near the pituitary gland. Cranial Nerve 3: Oculomotor Nerve  Eye Muscles Innervated: The oculomotor nerve innervates the superior rectus, medial rectus, inferior rectus, inferior oblique, and the levator palpebrae superioris muscles (bilateral). Function of the Edinger-Westphal Nucleus: Controls parasympathetic innervation for pupil constriction (pupillary light reflex). Involvement in the VOR (Vestibulo-Ocular Reflex): CN3 helps control eye movement to maintain stable vision during head movements. Pupillary Light Reflex: Light stimulus triggers pupillary constriction via CN2 and CN3. Damage to CN3 causes a fixed, dilated pupil. Accommodation Reflex: Involves pupil constriction and lens curvature changes for near vision. Cranial Nerve 4: Trochlear Nerve Muscles Innervated: The trochlear nerve innervates the superior oblique muscle (contralateral). Damage Symptoms: Damage to the trochlear nerve causes difficulty in looking down and inward (e.g., difficulty reading). Damage to Trochlear Nucleus: Results in similar symptoms, affecting the contralateral eye. Cranial Nerve 5: Trigeminal Nerve Muscles Innervated: The motor nucleus of CN5 innervates the muscles of mastication: masseter, temporalis, medial, and lateral pterygoids (bilateral). LMN Lesion Symptoms: Weakness or paralysis of chewing muscles. UMN Lesion: Typically causes mild weakness due to bilateral cortical innervation. Divisions of CN5: Ophthalmic (V1), Maxillary (V2), Mandibular (V3). Slow SS Pathways: Synapse in the trigeminal spinal nucleus (contralateral), projecting to the thalamus via the trigeminal lemniscus. Proprioception Pathways: Proprioception from the face enters the mesencephalic nucleus, then synapses in the trigeminal motor nucleus (ipsilateral). Fast SS: Synapse in the principal sensory nucleus of CN5 and project to the thalamus. Cranial Nerve 6: Abducens Nerve Muscles Innervated: The lateral rectus muscle (ipsilateral). Activation: Leads to abduction (lateral movement) of the eye. Innervation of CN3: Axons from CN6 synapse in the oculomotor nucleus to coordinate eye movements. Damage Symptoms: Results in inability to abduct the eye, leading to esotropia (inward gaze). Cranial Nerve 7: Facial Nerve Muscles Innervated: Muscles of facial expression (bilateral upper face, contralateral lower face). LMN Lesion Symptoms: Complete paralysis of muscles on the affected side. UMN Lesion Symptoms: Sparing of the upper face muscles, with weakness in the contralateral lower face. Axons from the Superior Salivatory Nucleus: Synapse in the submandibular and pterygopalatine ganglia, leading to salivation and lacrimation (bilateral). Taste Pathways: Taste from the anterior two-thirds of the tongue via the chorda tympani, synapsing in the solitary nucleus. Cranial Nerve 8: Vestibulocochlear Nerve Auditory and Vestibular Sections: Cochlear nerve carries auditory information to the cochlear nuclei, and vestibular nerve carries balance information to the vestibular nuclei. Cranial Nerve 9: Glossopharyngeal Nerve Muscles Innervated: The nucleus ambiguus innervates muscles of the pharynx (contralateral). LMN Lesion Symptoms: Difficulty swallowing and reduced gag reflex. Axons from Inferior Salivatory Nucleus: Synapse in the otic ganglion, projecting to the parotid gland for saliva secretion. General Visceral Afferents: Carry baroreceptor and chemoreceptor information from the carotid body and sinus. Taste: Taste from the posterior third of the tongue enters via CN9, synapsing in the solitary nucleus. Cranial Nerve 10: Vagus Nerve Muscles Innervated: Nucleus ambiguus innervates muscles of the larynx and pharynx (contralateral). LMN Lesion Symptoms: Difficulty swallowing, hoarseness, or loss of gag reflex. Axons from DMV (Dorsal Motor Nucleus of Vagus): Project to the heart, lungs, and digestive organs (bilateral). General Visceral Afferents: Carry sensory information from thoracic and abdominal organs, synapsing in the solitary nucleus. Cranial Nerve 11: Accessory Nerve Muscles Innervated: The accessory nucleus innervates the sternocleidomastoid and trapezius muscles (ipsilateral). LMN Lesion Symptoms: Weakness or paralysis in head rotation and shoulder elevation on the affected side. Cranial Nerve 12: Hypoglossal Nerve Muscles Innervated: Intrinsic and extrinsic muscles of the tongue (ipsilateral). UMN Lesion Symptoms: Contralateral tongue weakness, leading to deviation of the tongue to the side of the lesion. LMN Lesion Symptoms: Ipsilateral tongue atrophy and fasciculations, with deviation to the affected side when protruding the tongue. BASAL NUCLEI: Basal Nuclei: General Function: The basal nuclei are involved in the regulation of voluntary motor control, procedural learning, routine behaviors, and emotions. They help modulate the output of motor systems, controlling the initiation and coordination of movement. Input Region of the Basal Nuclei: The input region of the basal nuclei is the striatum, which includes the caudate nucleus and putamen. These regions receive information from various cortical areas, especially from the motor cortex, prefrontal cortex, and sensory areas. Output Region of the Basal Nuclei: The output region is the globus pallidus (both internal and external segments), and the substantia nigra (particularly the pars reticulata), which project to the thalamus and ultimately influence motor control areas of the cortex. Role of the Substantia Nigra in the Basal Nuclei: The substantia nigra is crucial for movement regulation, providing dopaminergic input to the striatum. This input modulates the activity of the direct and indirect pathways of the basal nuclei, facilitating smooth and coordinated motor function. The pars compacta of the substantia nigra releases dopamine, which is essential for proper motor control. Differences Between D1 and D2 Receptors: D1 receptors are excitatory and are involved in the direct pathway of the basal ganglia, promoting movement initiation. D2 receptors are inhibitory and are involved in the indirect pathway, inhibiting movement. Basal Nuclei Movement Disorders: Positive Signs: Dyskinesia (involuntary, uncontrolled movements) Resting tremor Chorea (irregular, jerky movements) Athetosis (slow, writhing movements) Negative Signs: Bradykinesia (slowness of movement) Hypokinesia (reduced amplitude of movement) Akinesia (lack of movement) Structures to Locate on Gross Specimens: Caudate nucleus Putamen Globus pallidus Ventral striatum / Nucleus accumbens Substantia nigra (pars compacta and pars reticulata, although differentiation is not required) Structures to Locate on Atlas Sections: Caudate nucleus Putamen Globus pallidus Ventral striatum / Nucleus accumbens  Substantia nigra Subthalamic nucleus Thalamic fasciculus Direct Loop of the Basal Nuclei: The direct pathway facilitates movement: 1. Cortex → Striatum (caudate and putamen) 2. Striatum → Globus Pallidus Internus (GPi) 3. GPi → Thalamus 4. Thalamus → Motor cortex (facilitates movement) Purpose of Dopaminergic Neurons Projecting from the Substantia Nigra: These neurons facilitate the direct pathway (via D1 receptors) and inhibit the indirect pathway (via D2 receptors), enhancing movement. Parkinson’s Disease: Parkinson’s disease is caused by degeneration of dopaminergic neurons in the substantia nigra, leading to: Reduced activation of the direct pathway and excessive activation of the indirect pathway. Symptoms: Bradykinesia, resting tremor, rigidity. Disinhibited Structure in Parkinson’s Disease: The thalamus becomes disinhibited, leading to abnormal motor control. Indirect Loop of the Basal Nuclei: The indirect pathway inhibits movement: 1. Cortex → Striatum 2. Striatum → Globus Pallidus Externus (GPe) 3. GPe → Subthalamic nucleus 4. Subthalamic nucleus → GPi 5. GPi → Thalamus (inhibition of movement) Huntington’s Disease: In Huntington's disease, there is degeneration of the striatum, particularly affecting the indirect pathway. This results in reduced inhibition of the thalamus, leading to excessive, involuntary movements (chorea). Disinhibited Structure in Huntington’s Disease: The thalamus becomes disinhibited, leading to uncontrolled movements. Cortical Decision-Making and Striatum: Motor activity decisions are processed in the motor cortex and primarily in the putamen. Cognitive decisions come from the prefrontal cortex and are processed in the caudate nucleus.  Emotional behaviors are influenced by the limbic cortex and processed in the ventral striatum/nucleus accumbens. Disinhibition: Disinhibition refers to the removal of inhibitory control, leading to the increased activity of a structure. In basal nuclei circuits, disinhibition typically involves the thalamus, allowing for enhanced or abnormal motor activity. Arteries Providing Blood to the Basal Nuclei: The basal nuclei receive blood from the lenticulostriate arteries (branches of the middle cerebral artery), which supply the striatum, globus pallidus, and other structures involved in motor control. Basal Nuclei Disorders and Symptoms: Dyskinesia: Abnormal involuntary movements, often seen in Parkinson's disease or as a side effect of medication. Dystonia: Sustained muscle contractions causing twisting movements and abnormal postures. Resting Tremor: Involuntary tremors occurring when the muscles are at rest (common in Parkinson's disease). Athetosis/Chorea: Slow, writhing movements (athetoid) or jerky, dance-like movements (chorea). Hemiballismus/Ballismus: Violent, flinging movements typically affecting one side of the body due to damage in the subthalamic nucleus. CEREBELLUM: Cerebellum: Structures to Locate on Gross Specimens: Cerebral hemispheres: The large, lateral regions of the cerebellum. Vermis: The midline region of the cerebellum that connects the two hemispheres. Paravermis region: The area adjacent to the vermis, between the vermis and the cerebellar hemispheres. Flocculonodular lobe: A small lobe located at the base of the cerebellum, involved in balance and eye movements. Tonsil: Part of the cerebellar hemisphere, located near the posterior lobe, and involved in motor control. Anterior and posterior cerebellar lobes: The anterior lobe is the portion of the cerebellum anterior to the primary fissure; the posterior lobe lies posterior to it. Primary fissure: The fissure that divides the cerebellum into the anterior and posterior lobes. Horizontal fissure: Divides the cerebellum into superior and inferior parts. Inferior cerebellar peduncle: A large bundle of afferent fibers that connect the cerebellum to the medulla. Middle cerebellar peduncle: Carries input from the pons to the cerebellum. Superior cerebellar peduncle: Carries output from the cerebellum to the midbrain and thalamus.  Arbor vitae: The white matter tracts in the cerebellum that look like a tree, located beneath the cortex. Cerebellar Circuits: Vestibulocerebellum Circuit: Function: Involved in balance and eye movements (coordination of head and eye movements). Muscles influenced: Primarily muscles involved in posture and equilibrium, particularly those of the trunk and proximal limbs. Mossy fibers synapse onto: The granule cells in the cerebellar cortex. Deep cerebellar nuclei: Fastigial nucleus. Targets: The circuit ultimately influences the vestibular nuclei and reticulospinal pathways, affecting balance and posture. Cerebrocerebellar Circuit: Function: Coordination of voluntary movements, motor planning, and cognitive functions. Muscles influenced: Primarily distal limb muscles, involved in fine motor control. Mossy fibers synapse onto: The granule cells in the cerebellar cortex. Deep cerebellar nuclei: Dentate nucleus. Targets: The thalamus, particularly the ventrolateral nucleus, which relays information to the motor cortex. Spinocerebellar Circuits: There are two types: Posterior Spinocerebellar Tract (PSCT) and Cuneocerebellar Tract (CCT). Function: These circuits help with proprioception and motor control feedback. Muscles influenced: Muscles involved in posture, balance, and limb movement. Mossy fibers synapse onto: Granule cells in the cerebellar cortex. Deep cerebellar nuclei: Interposed nuclei (emboliform and globose) and fastigial nucleus. Targets: The circuits influence the red nucleus, vestibular nuclei, and thalamus to modify motor commands. Overall Functions of the Cerebellum: The cerebellum is essential for: Coordinating voluntary movements. Maintaining posture and balance. Modifying motor commands for smooth execution. Motor learning (fine-tuning movements). Cognitive and emotional processing (especially in the cerebellar hemispheres). Functions of the Cerebellar Peduncles: Superior cerebellar peduncle: Carries output from the cerebellum, mainly to the thalamus and midbrain (important for motor coordination). Inferior cerebellar peduncle: Carries input from the spinal cord (especially proprioceptive signals) and brainstem to the cerebellum. Middle cerebellar peduncle: Carries input from the pons, primarily the pontocerebellar fibers, involved in motor control and coordination. Cerebellar Layers and Their Contents: 1. Molecular layer: Contains parallel fibers from granule cells and Purkinje cell dendrites. 2. Purkinje cell layer: Contains the Purkinje cells, which are the primary output cells of the cerebellar cortex. These cells are inhibitory (GABAergic). 3. Granule cell layer: Contains granule cells, which are the most numerous cells in the brain and are excitatory (glutamatergic). Their axons form parallel fibers that synapse on Purkinje cells. Cerebellar Fiber Types: Mossy fibers: ○ Origin: The pontine nuclei, spinocerebellar tract, vestibular nuclei, and other sources. ○ Target: Granule cells in the cerebellar cortex. ○ Excitatory: They are excitatory (glutamatergic). Granule cells: ○ Origin: These cells are located in the granule cell layer. ○ Target: Purkinje cells via their parallel fibers. ○ Excitatory: They are excitatory (glutamatergic). Climbing fibers: ○ Origin: The inferior olivary nucleus in the brainstem. ○ Target: Directly synapse on Purkinje cells. ○ Excitatory: They are excitatory (glutamatergic). Purkinje cells: ○ Input: Receive input from mossy fibers (via granule cells) and climbing fibers. ○ Output: Project to the deep cerebellar nuclei. ○ Inhibitory: They are inhibitory (GABAergic). Blood Supply to the Cerebellum:  Superior cerebellar artery (SCA): Supplies the superior cerebellum, including the cerebellar hemispheres. Anterior inferior cerebellar artery (AICA): Supplies the inferior cerebellum, including the flocculonodular lobe and parts of the anterior lobe. Posterior inferior cerebellar artery (PICA): Supplies the posterior cerebellum, including parts of the vermis and lateral cerebellar hemispheres. Cerebellar Disorders: Dysrhythmia: An abnormal rhythm in movement, often seen in disorders like cerebellar ataxia. Dysmetria: Inability to properly judge distances or the force of a movement (e.g., overshooting or undershooting). Intention tremor: Tremors that occur during voluntary movement, typically seen in cerebellar damage. Decomposition of movement: The inability to perform smooth, coordinated movements; movements may appear segmented or jerky. Spinocerebellar Tracts: Posterior Spinal Cerebellar Tract (PSCT): ○ Modality: Proprioception. ○ Pathway: Carries proprioceptive information from the lower limbs to the cerebellum via the dorsal columns. ○ Structures: Dorsal column nuclei, lateral cuneate nucleus, and cerebellar cortex. Cuneocerebellar Tract: ○ Modality: Proprioception from the upper limbs. ○ Pathway: Information from the cervical spinal cord to the cerebellum. ○ Structures: Cuneate nucleus and cerebellum. Lesions in the Cerebellum: Medial lesions: Affect balance, truncal ataxia, and posture (e.g., vermis lesions). Lateral lesions: Affect fine motor control, leading to limb ataxia and dysmetria (e.g., hemispheric lesions). LIMBIC/HYPOTHALAMUS: Limbic System Structures and Functions 1. Cingulate Gyrus/Cingulum ○ Location: Above the corpus callosum, forming part of the limbic lobe. ○ Function: Involved in emotion formation, processing, and regulation, particularly in linking behavioral outcomes to motivation. 2. Hypothalamus ○ Location: Located below the thalamus, above the brainstem.  ○ Function: Regulates autonomic functions like hunger, thirst, sleep, temperature, and emotional responses. It also controls the endocrine system through the pituitary gland. 3. Hypothalamic Sulcus ○ Location: A groove separating the hypothalamus from the thalamus. ○ Function: Marks the boundary between the hypothalamus and other brain regions, critical for anatomical organization. 4. Infundibulum ○ Location: The stalk connecting the hypothalamus to the pituitary gland. ○ Function: Transmits hypothalamic signals to the pituitary gland, controlling hormone release. 5. Mammillary Bodies ○ Location: Paired structures at the base of the brain, part of the hypothalamus. ○ Function: Involved in memory processing, part of the Papez circuit. 6. Anterior/Posterior Perforated Substance ○ Location: Located at the base of the brain, near the optic chiasm. ○ Function: Contains openings through which blood vessels pass; related to olfactory processing and limbic functions. 7. Uncus ○ Location: The anterior part of the parahippocampal gyrus, part of the temporal lobe. ○ Function: Involved in olfactory processing and memory functions. 8. Parahippocampal Gyrus ○ Location: A region of the temporal lobe surrounding the hippocampus. ○ Function: Involved in memory encoding and retrieval. 9. Amygdala ○ Location: Deep within the temporal lobe, near the hippocampus. ○ Function: Essential for processing emotions, particularly fear and pleasure. It also plays a role in memory. Hypothalamus Subdivisions and Functions 1. Preoptic Division ○ Location: Anterior part of the hypothalamus, near the optic chiasm. ○ Function: Involved in thermoregulation, reproductive behaviors, and sleep-wake cycles. 2. Anterior Region ○ Location: Near the optic chiasm. ○ Function: Regulates parasympathetic functions like temperature regulation and water balance. 3. Tuberal Region ○ Location: Middle portion of the hypothalamus. ○ Function: Involved in regulating hunger, thirst, and hormonal control via the pituitary gland. 4. Posterior Region ○ Location: Near the mammillary bodies. ○ Function: Regulates sympathetic functions and controls response to stress and temperature. 5. Periventricular Zone ○ Location: Around the third ventricle. ○ Function: Involved in the regulation of the hypothalamic-pituitary axis and autonomic control. 6. Medial Zone  ○ Location: Near the center of the hypothalamus. ○ Function: Involved in the regulation of emotions, feeding, and circadian rhythms. 7. Lateral Zone ○ Location: Lateral parts of the hypothalamus. ○ Function: Involved in hunger and energy regulation, including the stimulation of appetite. Inputs and Outputs of the Hypothalamus 1. Major Inputs to the Hypothalamus: ○ From the limbic system (e.g., amygdala, hippocampus) ○ From the brainstem (e.g., reticular formation) ○ From the thalamus ○ From the olfactory system ○ From the cortex (e.g., prefrontal cortex, cingulate gyrus) ○ From the sensory systems (e.g., visceral and somatic afferents) 2. Pituitary Gland Link to Hypothalamus ○ The hypothalamus controls the pituitary gland by releasing hormones into the bloodstream that regulate various endocrine functions. ○ The anterior pituitary (adenohypophysis) is controlled by hypothalamic releasing and inhibiting hormones. ○ The posterior pituitary (neurohypophysis) is controlled by hypothalamic neurons that release oxytocin and vasopressin. The Limbic System Components 1. Components of the Limbic System: ○ Cingulate gyrus ○ Hippocampus ○ Amygdala ○ Hypothalamus ○ Mammillary bodies ○ Fornix 2. General Functions of the Limbic System: ○ Regulation of emotions, memory, and certain autonomic functions. ○ Involvement in motivation, behavior, and long-term memory. Key Limbic System Structures and Their Functions 1. Amygdala ○ Function: Involved in emotional processing, particularly fear, pleasure, and aggression. It is also central to memory formation linked to emotions. 2. Hippocampus ○ Function: Critical for the formation of new memories and spatial navigation. 3. Papez Circuit ○ Function: A neural circuit involved in the regulation of emotion and memory.  ○ Purpose: Facilitates communication between the hippocampus and hypothalamus and helps regulate emotional responses. ○ Pathway: Hippocampus → Fornix → Mammillary bodies → Anterior thalamic nucleus → Cingulate gyrus → Back to hippocampus. Disorders and Memory Functions 1. Korsakoff’s Syndrome ○ Cause: Often due to thiamine (vitamin B1) deficiency, commonly seen in alcoholics. ○ Symptoms: Anterograde amnesia (inability to form new memories), retrograde amnesia (loss of past memories), and confabulation (making up memories). 2. Memory Types: ○ Declarative (explicit): Conscious recall of facts and events. ○ Non-declarative (implicit): Unconscious memory, such as procedural memory (skills and habits).