Brain and Cranial Nerve Anatomy

Nervous system

Subdivided into 2 divisions: central nervous system and peripheral nervous system

Central nervous system

Consists of brain and spinal cord

Peripheral nervous system

Consists of cranial and spinal nerves

Brain regions

Cerebrum, diencephalon, cerebellum, and brainstem (midbrain, pons, and medulla oblongata).

Cranial nerves

12 pairs

Cerebrum

Largest region of the brain comprising 80% of its total mass

Divided into left and right cerebral hemispheres by very deep longitidinal fissure

Corpus callosum

Two hemispheres are connected to each other by it

Formed by axons passing between the two hemispheres

Cerebral cortex

Outer surface of each hemisphere that is gray matter

White matter

Composed of myelinated axons interconnecting different regions of the cerebrum and other regions of the brain

Underneath the cerebral cortex and extending through the corpus callosum

Gyri

Singular is gyrus

Peaks of the brain

Sulci

Singular is sulcus

Valleys of the brain

Exceptionally deep sulci are called fissures

5 Lobes

Frontal, parietal, occipital, temporal, and insula

Frontal lobe

Functions include:

conscious thought

memory storage

motor control

judgement

problem solving

emotion

Broca's area

Motor control of the muscles involved in producing speech

In frontal lobe

Temporal lobe

Recieves auditory stimuli from cochlea of the ear

Pons

Name means "bridge"

Links cerebellum with rest of brain

Medulla oblongata

Regulates blood pressure, heart rate, and force of contraction, and respiratory rate

All ascending sensory and descending motor impulses pass through medulla

Site where many fibers cross to the other side

Continuous with spinal cord

Cerebellum

Second largest region of the brain

Located inferior to the occipital lobe

Works with cerebrum to coordinate skeletal muscles

2 parts are arbor vitae and folia

Occipital lobe

Receives visual stimuli from photoceptors in the eye

Parietal lobe

Functions include analyzing sensory stimuli

Fornix

Tract of white matter along inferior border of sptum pellucidum

Interconnects regions of cerebrum with the mammillary bodies

Anterior commissure

Tract of white matter

Interconnects optic chiasma and cerebral hemispheres

Infundibulum

Brain stem

Midbrain

Pons

Medulla oblongata

Diencephalon

Lies inferior to the cerebrum

Epithalamus and choroid plexus form the roof and the hypothalamus forms the floor and the thalamus forms the lateral walls

Third ventricle

Center of the diencephalon, with regions of the diencephalon arranged around it

Thalamus

Gray matter

form walls of third ventricle

Relays sensory information to correct region of cerebrum

Pineal gland

Part of epithalamus

an endocrine gland

Secretes melatonin

Regulates circadian rhythm

Mammillary body

Gray matter of the hypothalamus

Controls eating and swallowing reflexes

Pituitary gland

An endocrine gland

Connected to the hypothalamus by stalk of tissue called infundibulum

Secretion is regulated by hypothalamus

Optic chiasma

Point at which optic nerves cross

Hypothalamus

Lies below thalamus

Regulates appetite, thirst, body temperature

Controls pituitary gland

Choroid plexus

Vascular tissue in roof of third ventricle

Secretes cerebrospial fluid

Intermediate adhesion

Projection of gray matter from thalamus into the third ventricle

Fourth ventricle

Anterior to the cerebellum

Brainstem is anterior to the fourth ventricle

Arbor vitae

Network of white matter inside cerebellum

Folia

Folds in the surface of the cerebellum

Midbrain

Pons and diencephalon

Path for descending fibers to cerebellum and medulla

Cerebral aqueduct

Connects third and fourth ventricles

Superior colliculus

Part of midbrain

Form the corpora quadrigemina with inferior colliculi

Controls visual reflexes

Inferior colliculus

Part of the midbrain

Form the corpora quadrigemina with superior colliculi

Controls auditory reflexes

Meninges

Connective tissue layers that form a protective sac around the brain and spinal cord

Cerebral spinal fluid

acts as a cushion by absorbing jarring motions of the brain within the cranium

Dura mater

Superficial layer of meninges

Composed of dense irregular connective tissue

Forms a tough, protective sac

Consists of the outer periosteal layer and inner meningeal layer

Periosteal layer

Fused to periosteum of sull

Meningeal layer

Becomes outer covering for the brain

Arachnoid mater

Middle layer of meninges lying deep to dura mater

Thin layer of interstitial fluid separates two layers

Network of primarily collagen fibers

Connected to pia mater by web-like filaments

Pia mater

Deepest layer of meninges

Thin, delicate meshwork of elastic and collagen fibers

Fused to surface of brain

Subarachnoid space

Between arachnoid mater and pia mater

Contains cerebrospinal fluid (CSF)

Falx cerebri

Fold of dura mater

In longitudinal fissure between cerebral hemispheres

Superior sagittal sinus

Meningeal layer of dura mater splits to form sinus

Collects blood draining from brain

Subdural space

Between dura mater and arachnoid mater

Arachnoid villi

Extension of arachnoid mater through dura mater and into superior sagittal sinus

Allows CSF to be reabsorbed by venous system

Efferent

Motor

Afferent

Sensory

On Old Olympus' Towering Top A Friendly Viking Grew Vines And Hops

Cranial nerves mnemonic device

Olfactory (I)

"On"

Sensory: smell

Optic (II)

"Old"

Sensory: vision

Oculomotor (III)

"Olympus"

Motor: eyelid and eyeball movement, accommodation, and pupil constriction

Trochlear (IV)

"Towering"

Motor: movement of the eyeball

Trigeminal (V)

"Top"

Sensory: cutaneous sensations from face and mouth;

Motor: chewing from maxillary and mandibular

Abducens (VI)

"A"

Motor: movement of the eyeball

Facial (VII)

"Friendly"

Sensory: taste;

Motor: facial expression, saliva production, tear production

Vestibulo-cochlear (VIII)

"Viking"

Sensory: hearing and equilibrium

Glosso-pharyngeal (IX)

"Grew"

Sensory: taste; motor: swallowing and speech, saliva production

Vagus (X)

"Vines"

Sensory: general sense from the pharynx and epiglottis;

Motor: swallowing, coughing, speech, GI peristalsis, secretion of GI glands

Accessory (XI)

"And"

Motor: swallowing, movement of the head

Hypoglossal (XII)

"Hops"

Motor: swallowing and speech

medulla oblangata

controls heartbeat and breathing