Exam 1 Study Guide PDF

Exam 1 Study Guide ​ Organization of the brain (with its subdivisions) and spinal cord (including relationships with the vertebral column). ○​ Central Nervous System: CNS ​ Brain ​ Spinal Cord ○​ Peripheral Nervous System: PNS ​ Cranial Nerves...

Exam 1 Study Guide ​ Organization of the brain (with its subdivisions) and spinal cord (including relationships with the vertebral column). ○​ Central Nervous System: CNS ​ Brain ​ Spinal Cord ○​ Peripheral Nervous System: PNS ​ Cranial Nerves ​ Spinal Nerves ○​ Neuron ​ Cell Body → contains the nucleus and cytoplasm; metabolic center ​ Axon → conducts nerve impulses away from the cell body ​ Dendrite → received signals from other neurons ​ Synapse → junction between neurons where communication occurs ​ Myelin → fatty substance insulating axons; speeds up signal transmission ​ Nodes of Ranvier → gaps in the myelin sheath; facilitate rapid signal conduction ○​ Types of Neurons ​ Multipolar → one axon, multiple dendrites; motor neurons ​ Bipolar → one axon, one dendrite; sensory neurons in the retina ​ Unipolar → one process that bifurcates to act both as an axon and dendrite ○​ Terms ​ Nucleus → cluster of neurons in CNS ​ Ganglion → cluster of neurons in the PNS ​ Tract → bundle of axons in the CNS ​ Nerve → bundle of axons in the PNS ​ Afferent → signals toward the CNS ​ Efferent → signals away from the CNS ○​ CNS ​ Astrocytes → support neurons, maintain blood-brain barrier ​ Oligodendrocytes → produce myelin in the CNS ​ Microglia → act as immune cells, remove debris ​ Ependymal cells → line ventricles and produce cerebrospinal fluid (CSF) ○​ PNS ​ Schwann cells → produce myelin in the PNS ​ Satellite cells → support neurons in ganglia ​ Organization of the Brain ○​ Forebrain (Prosencephalon) ​ Telencephalon (cerebrum)  ​ 2 cerebral hemispheres connected across the midline by the corpus callosum and other pathways ​ Gray matter: mostly superficial, comprised of neurons and glia ​ White matter: deep to the cerebral cortex, contains axons ​ Comprise of 5 lobes: frontal, parietal, temporal, occipital, and insular ​ Basal ganglia: series of interconnected deep structures (nuclei) that are involved in motor planning and programming ​ Diencephalon ​ Thalamus: major relay for sensory function and reciprocally connected with the cortex ​ Hypothalamus: maintains homeostasis/equilibrium, motivated behaviors, and functions in concert with endocrine and autonomic systems ○​ Midbrain (Mesencephalon) ​ Major structures include ​ Cerebral peduncles ​ Substantia nigra ​ Red nucleus ​ Oculomotor and trochlear nuclei ​ Superior and inferior colliculi (III-IV) ○​ Hindbrain (Rhombencephalon) ​ Metencephalon ​ Pons: contains many ascending (medial lemniscus) and descending (pyramidal fibers) fiber tracts; also contains trigeminal, abducens, and facial motor nuclei (V-VII) ​ Cerebellum: processes proprioceptive information from muscles, tendons,s, and joints and coordinates motor activity. It contains three pairs of peduncles (stalks) that connect it to the various levels of the brainstem ​ Mylencephalon ​ Medulla oblongata: contains numerous ascending and descending fiber tracts and sensory relay nuclei (nucleus gracilis and cuneatus). Contains motor nuclei for cranial nerves IX, X, and XII ○​ The term “brainstem: refers to the midbrain, pons, and medulla and does not include the cerebellum ○​ Cerebral Cortex ​ Precentral gyrus ​ Central sulcus ​ Postcentral gyrus  ​ Lateral fissure ​ Organization of Spinal Cord ○​ 31 Segments and pairs of spinal nerves ○​ 8 cervical C ○​ 12 Thoracic (T) ○​ 5 Lumbar (L) ○​ 5 sacral (S) ○​ 1 coccygeal ○​ Spinal Segment ​ White matter → composed of nerve cell processes. They have a white appearance because of an insulating coat of a fatty substance called myelin ​ Gray matter → composed of nerve cell bodies. Because they are without the myelin coating, the groups of cell bodies appear gray ​ Dorsal horn → sensory nerve processes bringing information into the spinal cord ​ Doral root ganglion → the nerve cell bodies of the unipolar, sensory neurons from this enlarged structure ​ Ventral root → nerve cell processes of efferent fibers on their way to muscles. The bodies of the motor neurons are located in the ventral horn of the gray matter ​ Ventral horn → ​ Spinal nerve (mixed) → a mixture of incoming sensory processes and the outgoing motor processes. There are 31 pairs of these spinal nerves ​ Dorsal ramus → the mixture of sensory and motor fibers that branch posteriorly ​ Ventral ramus → the mixture of sensory and motor fibers that branch anteriorly. These are the processes that will be involved in the formation of nerve plexuses ​ Meninges (dura, arachnoid, pia) and ventricular system (including direction of CSF flow, release from the 4th ventricle into subarachnoid space, and entry into the venous system at ○​ Meninges ​ Dura mater → superficial layer, thick and tough ​ Double layer in the skull (periosteal and meningeal) ​ A single layer around the spinal cord ​ Arachnoid → middle layer ​ Spider web-like, delicate ​ Pia mater → deepest layer  ​ Closely adheres to brain surface; virtually transparent superior sagittal sinus). ○​ Ventricular System ○​ Ventricles (cavities) ​ Lateral ventricle (2)--> cavity of the telencephalon (extends to all lobes) ​ Interventricular foramen (of Monro) ​ 3rd ventricle → cavity of the diencephalon ​ Cerebral aqueduct → cavity of the mesencephalon ​ 4th ventricle → cavity of the metencephalon and myelencephalon ​ Foramen of Magendie (1; posterior), foramen of Luschka (2; lateral)--> continuous with subarachnoid space, exit site for CSF in the ventricular system ​ Central canal → cavity of spinal cord ○​ Choroid plexus → highly vascularized connective tissue (mesodermal origin), produces 60% of cerebrospinal fluid. Located in the lateral, third, and fourth ventricles ○​ Direction of flow ​ Lateral ventricle → interventricular foramina → third ventricle → cerebral aqueduct → fourth ventricle → foramen of magendie or foramina of luschka → subarachnoid space (SAS) → arachnoid granulations → superior sagittal sinus ​ Lateral ventricles, connected to the third ventricle via interventricular foramina ​ The third ventricle, connected to the fourth ventricle via the cerebral aqueduct ​ Fourth ventricle, releasing CSF into the subarachnoid space via the median and lateral apertures ​ CSF flows through ventricles, into the subarachnoid space, and drains into the superior sagittal sinus ​ Specializations of dura ( cerebri, etc.)and arachnoid (direction of blood flow within the dural venous sinuses to the internal jugular vein), arachnoid granulations ○​ Specializations of Arachnoid ​ Arachnoid granulations → extensions of arachnoid through the dura into the venous sinus (superior sagittal sinus) which permits CSF to enter venous circulation ○​ Specialization of Dura ​ Falx cerebri → separates cerebral hemispheres in the midline ​ Falx cerebelli → small dural sheath at posterior cerebellum ​ Tentorium cerebelli → dural sheath separating occipital lobe (above) from cerebellum (below)  ​ Diaphragma sellae → anchors pituitary into sella turcica; (forms roof of stella turcica) ​ Dural Venous sinuses ​ Superior sagittal sinus ​ Inferior sagittal sinus ​ Straight sinus ​ Transverse sinus ​ Sigmoid sinus ​ All of these drain into the internal jugular vein ​ CSF ○​ Production ​ 60% from choroid plexus (highly vascularized tissue of mesodermal origin) located in lateral, third and fourth ventricles ​ 40% from ependymal cells lining the entire ventricular system ○​ Function ​ Chemical buffer ​ Physical buffer ​ Buoyancy ○​ Rate of formation ​ 500 cc/day ​ Total volume: 150 cc ○​ Constituents ​ Water, electrolytes, glucose, proteins (few), lymphocytes (few) ​ Organization of 6-layered cerebral cortex; input vs output layers; relations to 3 principal fiber types (association, commissural, projection) ○​ Cerebral Cortex ​ Features → 2-4 mm thick, highly convoluted gray substance over half of which is hidden in depths of sulci/fissures. In total comprises half of brain volume ​ Divisions ​ Neocortex (isocortex) 6 layers (~ 95% of all cortex) ​ Allocortex (other cortex) 3-5 layers with variable lamination pattern ○​ Palwo cortex (e.g olfactory cortex) ○​ Archicortex (e.g. hippocampus) ​ Lamination Pattern ​ Layer 1 → molecular level- superficial layer rich in horizontally oriented dendrites and axon ​ Layer 2 → external granular later - mostly smaller neurons and few pyramidal cells. Inputs from layer II neurons  ​ Layer 3 → external pyramidal cell layer - contains medium-sized pyramidal neurons (apical dendrite, multiple basal dendrites) that give rise to association/commissural axon that terminate in layer II at the destination ​ Layer 4 → internal granular layer - contains mainly stellate neurons and few pyramidal neurons. Received thalamic input ​ Layer 5 → internal pyramidal layer - contains many large pyramidal neurons, including giant cells (Betz); axons become projection fibers to subcortical structures and spinal cord ​ Layer 6 → multiform layer - contains multiple cell types. Includes pyramidal cells that project to the thalamus ​ 3 principal fiber types ​ Association fibers → interconnect portion of cerebral cortex in the same hemisphere. They are axons of pyramidal cells in layer 3 that terminate in layer 2. They may be short or long ​ Commissural fibers → interconnect hemispheres. The overwhelming majority comprise the corpus callosum, some 200-300 million axons. They are axons of pyramidal cells in layer 3 that terminate in layer 2 in the contralateral hemisphere ​ Projection fibers → These axons project downstream to the thalamus, deep forebrain structures, brainstem, or spinal cord. These arise from the large pyramidal cells in layer 5, with the exception of those that project to the thalamus ​ 3 principal fiber types simplified ​ Association fibers: connect areas within the same hemisphere ​ Commissural fibers: connect corrsesponing areas of both hemispheres (e.g, corpus callosum) ​ Projection fibers: connect the cortex to lower brain regions and spinal cord ​ Cortical layers/fiber types ​ III → II association fibers ​ III → commissural fibers ​ V → SubC projection fibers ​ VI → thalamus corticothalamic fibers ​ Thal → IV thalamocortical fibers ​ Six-layered neocortex ​ Input layers: II (external granular) and IV (internal granular) ​ Output layers: III (external pyramidal) and V (internal pyramidal) ​ Layer I (molecular) consists mostly of fibers ​ Layer VI sends projection to the thalamus ​ Location of primary motor and sensory cortices ​ Types of Cortex ○​ Primary ​ Precentral gyrus (motor) ​ Postcentral gyrus (somatosensory) ​ Cuneus and lingual gyrus (at calcrine fissure; vision) ​ Superior temporal gyrus (auditory) ​ Piriform cortex (at the rhinal fissure of parahippocampal gyrus; olfaction) ○​ Association ​ Unimodal or hetero-modal; responsible for higher-order processing and integration ○​ Primary motor cortex → controls voluntary movements ○​ Primary sensory cortex → processes sensory input ○​ Homunculus → represents the somatotopic organization of body parts ​ Map major motor system from precentral gyrus, through various levels of the brainstem, to spinal cord white matter. ○​ Corticospinal tract (pyramidal tract) ​ Originates in precentral gyrus ​ Descends through internal capsule, cerebral peduncles, medulla pyramids, where most fibers decussate (cross midline) at the pyramidal decussation ​ Controls voluntary movements of limbs ○​ Rubrospinal tract ​ Originates in red nucleus of midbrain ​ Facilitates flexor movements in the upper limbs ○​ Vestibulospinal and reticulospinal tracts ​ Involved in posture and balance ​ Circle of Willis, branches, and vascular territories of major branches (anterior, middle, posterior cerebral arteries). ​ Circle of Willis ○​ Internal Carotid Artery (2) ​ Anterior cerebral artery (2) ​ Anterior communicating artery (1) ​ Middle cerebral artery (2) ​ Lenticulostriate aa. (many small)n ​ Ophthalmic artery ​ Anterior choroidal artery ○​ Basilar Artery (1) ​ Posterior cerebral artery (2) ​ Posterior communicating artery (2) ​ Superior cerebellar artery (2)  ​ Pontine aa. (4 pairs) ​ Anterior Inferior Cerebellar Artery (AICA) (2) ○​ Vertebral Artery (2) ​ Posterior inferior cerebellar artery (PICA) (2) ​ Anterior spinal artery (1) ○​ Posterior Spinal Arteries (2) ○​ Major arteries ​ Anterior cerebral artery (ACA): supplies medial, frontal, and parietal lobes ​ Middle Cerebral artery (MCA): supplies lateral frontal, parietal, and temporal lobes ​ Posterior Cerebral artery (PCA): supplies occipital libe ​ Details regarding major ascending sensory systems and crossover points, and consequences of lesions ○​ Dorsal column-medial lemniscus pathway ​ Carries fine tough, vibration, proprioceptions ​ Crosses at the medulla ○​ Spinothalamic tract ​ Carries pain and temperature ​ Crosses at the spinal cord level ○​ Dorsal spinocerebellar tract ​ Carries unconscious proprioception ​ Does not cross ​ Organization or dorsal root entry zone (DREZ) in terms of fiber diameter and conduction velocity; organization of spinal cord dorsal horn layers and names (especially II, IV, VI) ○​ DREZ is organized by fiber diameter and conduction velocity ○​ Spinal cord gray matter layer (rexed laminae) ​ Lamina II (substantia gelatinosa): pain modulation ​ Lamina IV: sensory relay ​ Lamina VI: proprioceptive input ​ Spinal reflexes and associated classes of sensory fiber type (I, II, III, IV) ○​ Reflex types ​ Stretch reflex: mediated by la fibers ​ Flexor withdrawl reflex: mediated by II and III fibers ○​ Sensory fiber types ​ Ia & II: muscle spindles (proprioception) ​ III & IV: free nerve endings (pain, temperature) ​ Sensory receptor types (Free Nerve Ending, Merkel, Meissner, Ruffini, Pacinian, Muscle spindle, GTO) and associated ascending sensory system ○​ Free nerve endings → pain and temperature (spinothalamic tract)  ○​ Merkel discs: light tough and pressure (dorsal column- medial lemniscus pathway) ○​ Meissner corpuscles → fine touch, low-frequency vibration (dorsal column-medial leminsicus pathway ○​ Ruffini endings → skin stretch, deep pressure (dorsal column-medial lemniscus pathway) ○​ Pacinan corpuscles → deep pressure, high frequence vibration (dorsal column-medial lemniscus pathway) ○​ Muscle spindles → proprioception, muscle stretch (dorsal column-medial lemniscus pathway, spinocerebellar tract) ○​ Golgi tendon organs (GTOs) → proprioception, muscle tension (spinocerebellar tract) ​ Trigeminal system for sensation from face (trigeminal nerve, spinal trigeminal nucleus, tigeminothalamic tract, VPM) ○​ Trigeminal Nerve (CN V) ​ First-order neurons in trigeminal ganglion ​ Second-order neurons in spinal trigeminal nucleus ​ Third-order neurons in VPM of thalamus, projecting to postcentral gyrus ​ Organization of autonomic nervous system: origins (thoracolumbar vs craniosacral), ganglia, targets, sympathetic vs parasympathetic responses ○​ Sympathetic (Thracolumbar) ​ Short preganglionic, long postganglionic fibers ​ Neurotransmitters: ACh (preganglionic), NE (postganglionic) ○​ Parasympathetic (craniosacral) ​ Long preganglionic, short postganglionic fibers ​ Neurotransmitter: ACh at both synapses