Brain Structures

Forebrain

one of the three regions of the brain that consists of the cerebrum and the diencephalon/thalamus, is the area responsible for the conscious perception of sensory input, integration of information, memory, emotions, initiation of behavioral responses, and homeostasis

Hemisphere

one half of the cerebrum or cerebellum

Cortex

outer layer of gray matter in the cerebrum and cerebellum

Gyrus

ridge of cerebral cortex

Folium

ridge of the cerebellar cortex

Sulcus

grooves in the cortex between gyri and folia

Cerebrum

part of the forebrain with two cerebral hemispheres separates on midline by the longitudinal fissure, has white matter located centrally organized in tracts, and gray matter located peripherally in the cortex and deep in functional nuclei

Lobe

gross anatomical division of the cerebral hemisphere, including both gray and white matter

Cerebral Cortex

peripheral area of the cerebrum with gray matter, has further distinct functional areas within each lobe

Frontal Lobe

primary motor cortex, prefrontal cortex

Parietal Lobe

somatosensory cortex (except olfaction)

Occipital Lobe

visual cortex

Temporal Lobe

auditory cortex, learning, and memory

Piriform Lobe

Olfactory cortex, learning and memory

Prefrontal Cortex

the phylogenetically newest part of the brain, most rostral aspect of the frontal lobe, function include problem solving, planning, and abstract thought

Cranial Nerve I

olfactory sensory nerve, afferent pathway for olfaction, detected by chemoreceptors located in the mucosa of the caudal nasal cavity, axons join to form the olfactory nerves, which passes though the cribriform plate of the ethmoid bone, continues to the olfactory bulb → olfactory peduncle → piriform lobe

Cribriform Plate

part of the ethmoid bone that allow passage of the axons of CN I to reach the piriform lobe

Olfactory Bulb

rostral portion of the brain that receive CN I and project axons to the olfactory peduncle to the piriform lobe

Olfactory Peduncle

input of the CN I is projected caudally through the tracts to the piriform lobe

Hippocampus

specialized region of cerebral cortex that is part of the limbic system, functions include learning and memory, and contribution of emotional and behavioral responses to sensory stimuli, has two-way projections with the hypothalamus

Thalamus

largest part of the diencephalon and functions as a sensory relay center, has both direct and diffuse cortical projection system

Direct Cortical Projection System

pathway of the thalamus that transmits precise sensory information to a specific functional region of cerebral cortex

Diffuse Cortical Projection System

pathway of the thalamus that receives input from the thalamic reticular system and disperses signals throughout the brain, important for integration

Hypothalamus

part of the diencephalon ventral to the thalamus and dorsal to the pituitary gland, functions include control of the autonomic nervous system and synthesizes hypocretin

Hypocretin

aka orexin, a neuropeptide hormone involved in the regulation of sleep, produced by the hypothalamus

Cranial Nerve II

optic nerve, axons for the conscious perception of visual stimuli synapse with the thalamus before reaching the occipital lobe, axons for reflex function synapse with the midbrain

Decussation

directly related to a larger field of view and inversely related to depth perception

Signs of Forebrain Dysfunction

changes in behavior or quality of mentation, somatosensory and/or visual deficits

Brainstem

one of the three sections of the brain consisting of the midbrain, pons, and medulla; responsible for involuntary life-sustaining functions, determination of level of arousal or consciousness, and motor functions in quadrupeds

Ascending Reticular Activating System (ARAS)

functional network that activates the cerebral cortex, establishes the awake state and level of consciousness, extends from the medulla to the thalamus, receives collateral axons from all conscious sensory pathways being projected through the thalamus and prioritizes input in terms of importance

Signs of Brainstem Dysfunction

changed in the level of arousal or consciousness or the quantity of mentation (stupor/coma), deficits in CNN III - XII, abnormal cardiac and respiratory patterns

Cerebellum

consists of two cerebellar hemispheres and a central vermis, sets the postural platform, regulates muscle tone, coordinates but does not initiate voluntary movement, and regulates balance, connects to brainstem via cerebellar peduncles, white matter centrally located in arbor vitae

Vermis

central portion of the cerebellum

Cerebellar Peduncles

connects the brainstem and the cerebellum

Arbor Vitae

white matter in the cerebellum, located centrally

Dura Mater

outer meninx with strong connective tissue

Arachnoid

delicate middle meninx fused to the inner Dura Mater

Subarachnoid space

space beneath the arachnoid layer containing CSF

Pia Mater

thin innermost meninx covering brain and spinal cord

Falx cerebri

partition of dura mater extending into the longitudinal fissure

tentorium Cerebelli

partition of dura mater extending into the transverse fissure between the occipital lobes and cerebellum

Lateral Ventricles

largest ventricles, one on each side of the cerebral hemispheres above the hippocampus

Third Ventricle

encircles the interthalamic adhesion

Mesencephalic Aquaduct

small canal running longitudinally through the midbrain to connect the third and fourth ventricle

fourth ventricle

located between the brainstem and overlying cerebellum and is continuous with the central canal of the spinal cord

Obex

narrowing of fourth ventricle to form the central canal of the spinal cord