Brain Regions and Anatomy

• Rostrally: Higher, anterior brain regions toward the snout.
• Caudally: Inferior, posterior brain regions toward the tail.
• Cerebrum: Composed of the cerebral hemispheres.
• Diencephalon: Forebrain part between cerebral hemispheres and midbrain, includes thalamus, hypothalamus, and third ventricle.
• Brain stem: Midbrain, pons, and medulla oblongata combined.
• Cerebellum: "Little brain" attached to the pons.

Brain Regions

• Four main regions: cerebrum, diencephalon, brain stem, cerebellum.
• Brain stem includes the midbrain, pons, and medulla oblongata.

Brain Stem Parts

• Midbrain: Between diencephalon and pons.
• Pons: Between midbrain and medulla oblongata.
• Medulla oblongata: Inferior brain stem part.

Primary Brain Vesicles (Week 4)

• Prosencephalon (forebrain).
• Mesencephalon (midbrain).
• Rhombencephalon (hindbrain).

Forebrain

• Prosencephalon divides into telencephalon and diencephalon.
• Telencephalon becomes cerebrum, cerebral hemispheres, cerebral cortex, white matter, and basal nuclei; associated with lateral ventricles.
• Diencephalon becomes thalamus, hypothalamus, epithalamus, and retina; associated with the third ventricle.

Midbrain

• Mesencephalon remains undivided, forming the midbrain of the brain stem; associated with the cerebral aqueduct.

Hindbrain

• Rhombencephalon divides into metencephalon and myelencephalon.
• Metencephalon becomes pons of the brainstem and cerebellum; associated with the fourth ventricle.
• Myelencephalon becomes the medulla oblongata of the brain stem.

Secondary Brain Vesicles

• The five secondary vesicles: telencephalon, diencephalon, mesencephalon, metencephalon, and myelencephalon.
• The neural tube's expansions and constrictions create three primary vesicles that further divide into five secondary vesicles, which then differentiate into specific brain structures.

Ventricles

• Ventricles: expansions of the brain's central cavity, filled with cerebrospinal fluid and lined by ependymal cells
• Play a role in the production, transport, and removal of cerebrospinal fluid.

Lateral Ventricles

• Lie close together in the cerebral hemispheres and are separated by the septum pellucidum.

Septum Pellucidum

• Thin membrane separating the lateral ventricles.

Third Ventricle

• Located in the diencephalon.

Cerebral Aqueduct

• Lies in the midbrain and connects the third and fourth ventricles.

Fourth Ventricle

• Located between the brain stem and cerebellum, featuring three openings: two lateral apertures and one median aperture.

Apertures

• Connect ventricles to the subarachnoid space to allow cerebrospinal fluid to fill ventricles and subarachnoid space.

Ependymal Cells

• Neuroglia forming the epithelial lining of brain ventricles and spinal cord's central canal.

Cerebrospinal Fluid

• Clear liquid that fills and surrounds the CNS, cushioning and nourishing the brain and spinal cord.

Cerebral Cortex

• Sheet of gray matter covering the cerebrum.

Cerebral White Matter

• Myelinated fibers bundled into tracts that carry impulses to or from the cortex.

Deep Gray Matter

• Contains short, nonmyelinated axons and clusters of neuron cell bodies called brain nuclei to allow complex neural functions.

Sulci

• Shallow grooves on the surface of the cerebral hemispheres.

Gyri

• Twisted ridges of brain tissue between sulci.

Fissure

• Grooves deeper and larger than the sulci.

Lobes of the Cerebrum

• Five lobes: frontal, parietal, occipital, temporal, and insula.

Frontal lobe

• Plans, initiates, and enacts motor movement including eye movement and speech production.

Parietal Lobe

• Processes sensory stimuli, enabling conscious awareness of somatic sensations, spatial awareness, and speech understanding.

Occipital Lobe

• Contains the visual cortex.

Temporal Lobe

• Contains auditory and olfactory cortexes. Functions include the recognition of objects, words, and faces, comprehension, emotional response and memory.

Insula

• Contains the visceral sensory cortex for taste and general visceral sensations.

Central Sulcus

• Separates frontal lobe from parietal lobe.

Precentral Gyrus

• Contains the primary motor cortex, anterior to the central sulcus.

Postcentral Gyrus

• Contains the primary somatosensory cortex, posterior to the central sulcus.

Parietooccipital Sulcus

• Separates parietal lobe from occipital lobe.

Lateral Sulcus

• Separates temporal lobe from parietal and frontal lobes.

Frontal Lobe (Function)

• Voluntary movement, planning movement, eye movement, speech production, executive cognitive functions, and emotional response.

Parietal Lobe (Function)

• General somatic sensation, spatial awareness of objects, sounds, and body parts, understanding speech.

Occipital Lobe (Function)

• Vision

Temporal Lobe (Function)

• Hearing, smell, object identification, emotional response, memory

Insula Lobe (Function)

• Taste

Sensory Areas

• Allow conscious awareness of sensation.

Primary Sensory Cortex

• Sensory areas for each of the major senses.

Association Areas

• Integrate diverse information to enable purposeful action.

Sensory Association Areas

• Each primary sensory cortex has association areas linked to it that process the sensory information.

Multimodal Association Areas

• Association areas that receive and integrate input from multiple regions of the cerebral cortex.

Motor Areas

• Control voluntary motor functions.

Primary Somatosensory Cortex

• Receives information from the general somatic senses and enables conscious awareness of these senses.

Somatosensory Association Center

• Communicates with the primary somatosensory cortex to integrate sensory inputs into a comprehensive understanding.

Primary Visual Cortex

• Receives visual information that originates from the retina of the eye and merges info from both eyes.

Visual Association Area

• Communicates with the primary visual cortex and continues processing the information by analyzing color, form, and movement.

Primary Auditory Cortex

• Functions in conscious awareness of sound; sound waves excite the sound receptors in the inner ear.

Auditory Association Area

• Relates the sound information to loudness, rhythm, and pitch and evaluates the sound.

Vestibular Cortex

• Responsible for conscious awareness of the sense of balance, specifically the position of the head in space.

Gustatory Cortex

• Conscious awareness of taste stimuli.

Olfactory Cortex

• Olfactory nerves from the nasal cavity transmit impulses that are relayed to this resulting in smell.

Visceral Sensory Cortex

• Receives general sensory input from the thoracic and abdominal organs.

Primary Motor Cortex

• Brings about precise voluntary movements of the body; especially forearms, fingers, and facial muscles.

Premotor Cortex

• Coordinates complex movements and relays the plan to the primary motor cortex for implementation; controls voluntary actions that depend on sensory feedback about spacial relations.

Frontal Eye Field

• Controls the voluntary movements of the eyes especially when one looks quickly at something.

Broca's Area

• Controls the motor movements necessary for speaking; extensively connected to the language comprehension areas in the posterior association area.

Posterior Association Area

• Integrates sensory input from the visual, auditory, and somatosensory association areas to form a unified perception of the sensory input; spatial location of the body in reference to the outside world.

Wernicke's Area

• Functions in speech comprehension and in the coordination of the auditory and visual aspects of language.

Anterior Association Area

• Prefrontal cortex; receives highly processed information from the posterior association area, integrates this with past experiences (limbic), and plans and initiates motor responses through linkage with the motor regions; thinking, perceiving, intentionally remembering and recalling informationi.

Limbic Association Area

• Integrates sensory and motor behaviors with past experiences, helps form memory, and uses those past experiences to influence future motor responses; processes emotions involved in complex personal and social interactions.

White Matter

• Underlies the gray matter of the cerebral cortex; the many fibers that form the white matter function to connect different parts of the brain together and to the brain stem and spinal cord.

Fibers in White Matter

• Commissural, association, and projection fibers.

Commissural Fibers

• Cross from one side of the CNS to the other; interconnect corresponding gray areas of the right and left cerebral hemispheres and allow the two hemispheres to function together as a coordinated whole.

Association Fibers

• Connect different parts of the same hemisphere; short fibers connect neighboring cortical areas and long fibers connect separated cortical lobes.

Projection Fibers

• Either descend from from the cerebral cortex to more caudal parts or ascend to the cortex from lower regions; how sensory information enters the cerebral cortex cortex and motor information leaves it.

Corpus Callosum

• Large band of commissure fibers connecting the two brain hemispheres.

Internal Capsule

• A compact bundle of projection fibers that pass between the thalamus and deep gray matter.

Corona Radiata

• Projection fibers that radiate through cerebral white matter to cortex in a fan shaped arrangement.

Deep Gray Matter

• Consists of the basal nuclei, basal forebrain nuclei, and the claustrum; works with the cerebral cortex to control voluntary movements.

Thalamus

• A paired structure that makes up 80% of the diencephalon and contains a dozen thalamic nuclei divided into three groups.

Thalamic Nuclei

• Ventral posterolateral nuclei, medial geniculate body, and lateral geniculate body.

Ventral Posterolateral Nuclei

• Thalamic nucleus that acts as relay stations for the sensory information ascending to the primary sensory areas of the cerebral cortex.

Medial Geniculate Body

• Thalamic nucleus that receives auditory input and links to the auditory cortex.

Lateral Geniculate Body

• Thalamic nucleus that receives visual input and transmits to the visual cortex.

Thalamus (Function)

• Every part of the brain that communicates with the cerebral cortex must relay its signals through a nucleus of this. Either tones down or amplifies the signals headed for the cerebral cortex.

Hypothalamus

• Inferior portion of the diencephalon that lies between the optic chiasma and the posterior border of the mammillary bodies.

Hypothalamus (function)

• Control of the autonomic nervous system; regulation of body temperature, hunger and thirst, sleep-wake cycles; control of the endocrine system, emotional responses, and motivational behavior; formation of memory.

Optic Chiasma

• The point at which the optic nerves cross.

Mammillary Bodies

• Rounded bumps that bulge from the hypothalamic floor.

Pituitary Gland

• Projects inferiorly from the hypothalamus and controls the other endocrine glands.

Infundibulum

• A stalk that attaches the pituitary gland to the hypothalamus.

Pineal Gland

• A small, unpaired knob on the most dorsal part of the diencephalon that is an endocrine gland that secretes melatonin.

Brain Stem

• The most caudal region of the brain that is made of the medulla oblongata, pons, and midbrain.

Brain Stem (Function)

• Acts as a passageway for all the fiber tracts running between the cerebrum and the spinal cord; heavily involved with the innervation of the face and hands (10 of 12 cranial nerves attach to it); produces rigidly programmed, automatic behaviors necessary for survival; integrates auditory and visual reflexes.

Midbrain

• The most rostral region of the brain stem that lies between the diencephalon and the pons.

Cerebral Aqueduct

• Central cavity of the midbrain that divides the midbrain into a tectum dorsally and cerebral peduncles ventrally.

Tectum

• The roof of the midbrain that is responsible for auditory and visual reflexes.

Cerebral Peduncles

• Form vertical pillars that appear to hold up the brain and contain the pyramidal motor tracts.

Superior Cerebellar Peduncles

• Contain fiber tracts that connect the midbrain to the cerebellum and carry efferent instructions from the cerebellum toward the cerebral cortex.

Corpora Quadrigemina

• Located in the midbrain and contains reflex centers for vision and auditory reflexes making up the tectum.

Superior Colliculi

• Acts in visual reflexes; when the eyes track and follow objects subconsciously.

Inferior Colliculi

• Acts in auditory reflexes; like when you are startled by a loud noise.

Periaqueductal Gray Matter

• Gray matter surrounding the cerebral aqueduct which contains cranial nerves III and IV.

Substantia Nigra

• Midbrain structure where dopamine is produced; involved in control of movement; the neuronal cell bodies are functionally linked to the deep gray matter.

Red Nucleus

• A large nucleus of the midbrain that receives inputs from the cerebellum and motor cortex and sends axons to motor neurons in the spinal cord; helps bring about flexion movement.

Pons

• A brain structure that relays information from the cerebellum to the rest of the brain; a bulge wedged between the midbrain and the medulla oblongata containing cranial nerves V, VI, and VII.

Pyramids

• Two longitudinal ridges that flank the ventral midline of the medulla and are made of pyramid fibers.

Decussation of the Pyramids

• In the caudal part of the medulla where 70-90% of pyramid fibers cross over to the other side of the brain.

Inferior Cerebellar Peduncles

• Fiber tracts that connect the medulla to the cerebrum dorsally. Arise from the medulla and carry primarily afferent fibers from the vestibular nuclei (equilibrium) and from the spinal cord (proprioception) into the cerebellum.

Inferior Olivary Nucleus

• A large wavy fold of gray matter in the olive that coordinates signals from the spinal cord to the cerebellum.

Visceral Reflex Centers

• Cardiac, vasomotor, and medullary respiratory centers.

Cardiac Center

• Adjusts force and rate of heartbeat.

Vasomotor Center

• Regulates blood pressure and flow by dilating and constricting blood vessels.

Medullary Respiratory Center

• Controls rhythm and rate of breathing.

Cerebellum

• Located dorsal to the pons and medulla oblongata and makes up 11% of the brain. Smooths and coordinates body movements that are directed by other brain regions.

Cerebellar Hemispheres

• Two halves that make up the cerebellum.

Vermis

• Connects the two cerebellar hemispheres.

Folia

• Folded ridges on the surface of the cerebellum.

Lobes of the Cerebellum

• Anterior, posterior, and flocculonodular.

Anterior Lobe

• Coordinates trunk and limb movements in the front.

Posterior Lobe

• Coordinates trunk and limb movements in the back.

Flocculonodular Lobe

• Adjusts posture to maintain equilibrium and coordinates head and eye movements. Hidden ventral to the posterior lobe.

Cerebellar Cortex

• Outer cortex of gray matter that covers the cerebellum and functions to smooth out body movements.

Arbor Vitae

• White matter of the cerebellum that consists of axons that carry information to and from the cortex.

Deep Cerebellar Nuclei

• Deeply situated gray matter that gives rise to axons that relay the instructions from the cerebellar cortex to other parts of the brain.

Cerebellar Peduncles

• Thick fiber tracts that connect the cerebellum to the brain stem.

Middle Cerebellar Peduncles

• Connect the pons to the cerebellum; afferent pathway that carries information from the cerebral cortex and pontine nuclei to the cerebellum.

Ipsilateral

• Located on the same side of the body.

Limbic System

• Responsible for the emotional impact actions, behaviors, and situations have on us and directs our responses to these emotions; functions in creating, storing, and retrieving memories, particularly those that elicit strong emotions.

Reticular Formation

• Runs through the core of the brain stem and is involved in alertness, arousal, and sleep; also contains visceral centers that control heart rate, breathing rate, and vomiting.

Skull

• Protects the brain from injury due to external force along with the meninges and cerebrospinal fluid.

Meninges

• Three connective tissue membranes that lie just external to the brain and spinal cord.

Dura Mater

• The strongest of the meninges; two-layered sheet of dense fibrous connective tissue.

Layers of Dura Mater

• Periosteal (superficial) and meningeal (deep).

Periosteal Layer

• Superficial; attaches to the internal surface of the brain.

Meningeal Layer

• Deep; forms the true external covering of the brain.

Dural Venous Sinuses

• Where the two dura mater layers separate; collect blood from the brain and conduct it into the jugular veins of the neck.

Falx Cerebri

• Sheet of dura mater that separates the two cerebral hemispheres.

Falx Cerebelli

• Sheet of dura mater that separates the two hemispheres of the cerebellum.

Tentorium Cerebelli

• Sheet of dura mater that separates cerebrum from cerebellum.

Subdural Space

• A thin potential space between the dura and arachnoid mater; has the potential to fill with fluid due to disease of trauma.

Arachnoid Mater

• Lies just deep to the dura mater and both surround the brain loosely and do not dip into the sulci.

Subarachnoid Space

• Deep to the arachnoid membrane which is spanned by weblike threads that hold the arachnoid mater to the pia mater; filled with CSF.

Arachnoid Villi

• Project superiorly through the dura mater into the superior sagittal sinus; valves that allow CSF to pass from the subarachnoid space into the dural venous sinuses.

Pia Mater

• A layer of delicate connective tissue, richly vascularized, that clings tightly to the brain's surface.

Choroid Plexus

• Capillary rich membranes located in the roofs of the four brain ventricles that makes cerebrospinal fluid.

Cerebrospinal Fluid

• A watery broth that fills the subarachnoid space and the central hollow cavities of the brain and spinal cord; provides a liquid medium that surrounds and floats the brain and spinal cord.

Cerebrospinal Fluid (Function)

• Resists compressive forces and cushions the brain and spinal cord; helps nourish the brain, removes wastes produced by neurons, and carries chemical signals such as hormones between different parts of the CNS.
• CSF is produced by the choroid plexus of each ventricle, flows through the ventricles into the subarachnoid space, gets absorbed into the dural venous sinuses.

Meningitis

• An inflammation of the meninges caused by a bacterial or viral infection.

Encephalitis

• Spreads from meningitis and causes inflammation of the brain tissue.

Hydrocephalus

• Excessive accumulation of the CSF in the ventricles or subarachnoid space that can exert a crushing pressure on the brain.

Blood Brain Barrier

• Protects the CNS by preventing bloodborn toxins, such as urea, mild toxins from food, and bacterial toxins from entering brain tissue; made of the least permeable capillaries in the body.

Spinal Cord

• Runs through the vertebral canal of the vertebral column from the foramen magnum to the 1st or 2nd lumbar vertebra.

Characteristics of the Spinal Cord

• Sensory and motor innervation, two-way conduction path, and major center for reflexes.

Sensory and Motor Innervation

• Through the spinal nerves that attach, the spinal cord is involved with this in the entire body inferior to the head.

Two Way Conduction Path

• Through ascending and descending tracts traveling within its white matter, the spinal cord provides this for signals between the body and brain.

Major Center for Reflexes

• Through sensory and motor integration in its gray matter, the spinal cord is responsible for this.

Spinal Dural Sheath

• Tough dura mater; differs from the brains dura mater because it does not attach to the surrounding bone.

Epidural Space

• External to the spinal dura that is filled with a cushioning fat and a network of veins.

Conus Medullaris

• At the inferior end of the spinal cord where it tapers into a cone.

Filum Terminale

• A long filament of connective tissue that extends from the conus medullaris to the coccyx and anchors the spinal cord in one place.

Cervical Enlargement

• Enlargement in the cervical region where the nerves to the upper and lower limbs arise.

Lumbar Enlargement

• Enlargement in the lumbar region where the nerves to the upper and lower limbs arise.

Cauda Equina

• The collection of lumbar and sacral nerve roots at the inferior end of the vertebral canal.

Denticulate Ligaments

• Lateral extensions of the pia mater that anchor the spinal cord to the dura mater.

Dorsal Median Sulcus

• Runs the length of the spinal cord, partly dividing it into left and right halves.

Ventral Median Fissure

• Wider than the dorsal median sulcus but serves the same purpose.

Central Canal

• Within the gray commissure is the narrow central cavity of the spinal cord.

Dorsal Root

• Where the axons of the dorsal root ganglia reach the spinal cord.

Ventral Root

• Where the axons of the motor neurons are sent out of the spinal cord.

Gray Commissure

• The crossbar of the H that is composed of unmyelinated axons that cross from one side of the CNS to the other.

Posterior Horns

• The posterior arms of the H.

Anterior Horns

• The two anterior arms of the H.

Lateral Horns

• Present in the thoracic and superior segments of the spinal cord and are small gray matter columns.

Ascending Tracts

• Carry information to the more rostral regions of the CNS and carry sensory information to the brain.

Descending Tracts

• Carry information to the more caudal regions of the CNS and carry motor instructions to the effectors of the body.

Commissural Tracts

• Connect corresponding cortical areas in the two hemispheres.

Posterior Funiculus

• A portion of the white matter that contains many fiber tracts with similar destinations and functions; subdivided into the fasciculus gracilis and fasciculus cuneatus.

Anterior Funiculus

• Front long rope that contains many fiber tracts.

Lateral Funiculus

• Divided from the anterior funiculus by an imaginary line and contains many fiber tracts.

Pyramidal Tract

• Controls precise and skilled voluntary movements and is also called corticospinal tracts, direct pathway because it extends without synapsing from the pyramidal cells in the cerebral cortex to the spinal cord.

Pyramidal Cells

• Large neurons found in the primary motor cortex of the brain.

Extrapyramidal Tracts

• Stimulates body movements that are subconscious, coarse, or postural and originate in the subcortical motor nuclei of the brain stem.

Concussion

• Transient brain injury typically produced from a blow or violent shaking.

Contusion

• Marked destruction of brain tissue and produces a coma.

Cerebrovascular Accident

• Stroke, blockage or interruption of blood flow to a brain region that is caused by burst or torn cranial vessels or by a blood clot blocking cranial vessels.

Alzheimer's Disease

• A progressive degenerative disease of the brain that ultimately results in dementia; loss of memory, shortened attention span, depression, and disorientation.

Paraplegia

• The lower limbs lose movement but not the upper; transection occurs between T1 and L2 vertebrae.

Quadriplegia

• All four limbs lose the ability to move that happens if there is damage to the cervical region; if it occurs between C3 and C5, the person cannot survive without life support.