Anatomy Exam 3 - Brain and Cranial Nerves

neural tube

develops into the central nervous system (CNS) which consists of the brain and spinal cord

rostral vs. caudal neural tube

rostral neural tube: anterior end that develops into the brain (toward the head)

caudal neural tube: posterior end that develops into the spinal cord (toward the tail)

4 major parts of the brain

1) cerebrum

2) cerebellum

3) diencephalon

4) brainstem

cerebrum

largest part of the brain

responsible for conscious thought, memory, sensory perception, language, and voluntary movement

divided into left and right cerebral hemispheres

cerebellum

located posteriorly and inferiorly, behind the brainstem

coordinates balance, posture, and smooth, accurate movements

helps with motor learning

diencephalon

located between the cerebrum and brainstem

includes the thalamus and hypothalamus

processes sensory information and regulates homeostasis

brainstem

connects the brain with the spinal cord

includes the midbrain, pons, and medulla oblongata

controls the essential function such as breathing, heart rate, and alertness

meninges

connected tissue membranes that protect the skull

3 meninges of the skull

1) dura mater: outermost, tough protective membrane

2) arachnoid mater: middle, web-like membrane

3) pia mater: innermost, delicate membrane that closely follows the brain’s surface

meningeal spaces

1) epidural space

2) subdural space

3) subarachnoid space

epidural space

between the skull and dura mater

can form when blood separates the dura from the skull

subdural space

between the dura and arachnoid

can form when blood separates these membranes

subarachnoid space

between arachnoid and pia mater

contains cerebrospinal fluid (CSF) and blood vessels

choroid plexus

produces cerebrospinal fluid (CSF)

consists of blood capillaries and ependymal glial cells that form a specialized barrier + secrete CSF

cerebrospinal fluid (CSF)

cushions the brain and spinal cord, provides buoyancy, helps maintain a stable chemical environment, and transports waste products

brain ventricles

interconnected cavities within the brain that contain CSF

CSF flow pathway

1) choroid plexus produces CSF

2) lateral ventricles

3) interventricular foramina

4) third ventricle

5) cerebral aqueduct

6) fourth ventricle

7) openings into the subarachnoid space

8) subarachnoid space around the brain and spinal cord

9) arachnoid villi → dural venous sinuses → blood

the choroid plexus is found in the lateral, third and fourth ventricles; amount of CSF increases as it travels down

arachnoid villi (granulations)

structures that allow CSF to be reabsorbed into the venous blood

dural venous sinuses

channels b/w layers of dura mater that collect venous blood and receive reabsorbed CSF

cerebral hemispheres

left and right halves of the cerebrum

longitudinal fissure

deep groove separating the right and left hemispheres

transverse fissure

separates the cerebrum from the cerebellum

sulcus (plural sulci)

groove in the brain’s surface

gyrus (plural gyri)

raised ridge b/w sulci

cerebral cortex

outer layer of gray matter of the cerebrum

folds of the cerebrum increase the surface area available for neurons

central sulcus

separates the frontal lobe from the parietal lobe

lateral sulcus

separates the temporal lobe from the frontal + parietal lobes

precentral gyrus

located immediately anterior to the central sulcus; contains the primary motor cortex

postcentral gyrus

located immediately posterior to the central sulcus; contains the primary somatosensory cortex

gray vs white matter

gray matter:

contains neuron cell bodies, dendrites, and synapses

processes/integrates information

forms the cerebral cortex + deeper nuclei

white matter:

contains primarily myelinated axons

carries information b/w regions

forms tracts connecting different CNS regions

4 cerebral lobes

1) frontal lobe

2) parietal lobe

3) temporal lobe

4) occipital lobe

frontal lobe

voluntary motor control

planning, decision-making, judgment, and personality

speech production in the dominant hemisphere (Broca’s area)

contains the primary motor cortex

parietal lobe

processes touch, pressure, pain, temperature, and body position

contains the primary somatosensory cortex

helps with spatial awareness

temporal lobe

hearing and auditory processing

memory and aspects of emotion

language comprehension in the dominant hemisphere (often Wernicke’s area)

occipital lobe

primarily responsible for visual processing

contains the primary visual cortex

motor homunculus vs. sensory homunculus

homunculus: maps of the body represented across the cerebral cortex

motor - represents control of voluntary movement

sensory - represents bodily sensations

body parts requiring detailed sensation + precise movements (hands, lips, face) receive more cortical representation

3 types of white matter fibers

1) commissural fibers

2) association fibers

3) projection fibers

commissural fibers

connect the left and right cerebral hemispheres

ex: corpus callosum

association fibers

connect different areas within the same hemisphere

ex: fibers connecting the frontal and parietal cortical areas

projection fibers

connect the cerebral cortex w/ lower CNS structures, including the brainstem and spinal cord

ex: internal capsule fibers

major limbic structures

1) cingulate gyrus

2) hippocampus

3) amygdala

cingulate gyrus

curves along the medial surface of the cerebral hemisphere

involved in emotion, motivation, and attention

hippocampus

located in the medial temporal lobe

important for forming new memories + spacial memory

amygdala

located in the medial temporal lobe, near the hippocampus

helps process emotional significance (fear and threat)

primary functions of the limbic system

involved in emotion and emotional responses, learning and memory, motivation and reward, and linking emotions w/ memories and behavior

functions of the cerebellum

coordinating voluntary movement

maintaining balance and posture

regulating muscle tone

improving the timing and accuracy of movements

supporting motor learning

thalamus vs. hypothalamus

thalamus: major relay and processing station for most sensory information traveling to the cerebral cortex; also participates in motor and attention circuits

hypothalamus: regulates homeostasis, autonomic activity, endocrine function, body temperature, hunger, thirst, and circadian rhythms

brainstem components (rostral to caudal)

1) midbrain

2) pons

3) medulla oblongata

midbrain

involved in visual and auditory reflexes

helps control eye movements

participates in motor control

pons

relays information between the cerebrum and cerebellum

participates in breathing regulation

contains nuclei associated with several cranial nerves

medulla oblongata

regulates vital functions (heart rate, blood pressure, breathing)

contains reflex centers for swallowing, coughing, and sneezing

connects w/ spinal cord

reticular formation

network of neurons extending through the brainstem

maintains alertness and wakefulness, regulates the sleep-wake cycle, helps control attention and consciousness, filters incoming sensory information, contributes to muscle tone and autonomic regulation

RAS (reticular activating system) is especially important for arousal + maintaining consciousness

cranial nerves

12 pairs

originates in the brain or brainstem

distributes to the head and neck, with CN X extending to thoracic/abdominal organs

can function as sensory, motor, autonomic, or mixed

spinal nerves

31 pairs

originates in the spinal cord

distributes to trunk and limbs + some internal structures

all 31 spinal nerves are mixed nerves (carry sensory + motor fibers)

motor nerve

carries commands to skeletal muscle

autonomic nerve

carries parasympathetic signals to glands, smooth muscle, or cardiac muscle

general sensory nerve

carries touch, pain, temperature, and other general sensations

special sensory nerve

carries specialized senses such as smell, vision, hearing, balance, or taste

CN I

olfactory nerve - sensory

function: smell

modality: special sensory

CN II

optic nerve - sensory

function: vision

modality: special sensory

CN III

oculomotor nerve - motor + autonomic

function: moves most eye muscles, elevates the upper eyelid, constricts the pupil, and helps the lens accommodate for near vision

modality: motor and parasympathetic

CN IV

trochlear nerve - motor

function: controls the superior oblique eye muscle, which helps direct the eye downward when it is turned inward

modality: motor

CN V

trigeminal nerve - mixed

function: facial sensation and chewing

modality: general sensory and motor

3 branches: ophthalmic, maxillary, and mandibular

CN VI

abducens nerve - motor

function: controls the lateral rectus muscle, moving the eye laterally (abduction)

modality: motor

CN VII

facial nerve - mixed

function: facial expressions, taste, parasympathetic control of the lacrimal and several salivary glands

modality: motor, special sensory (taste), and parasympathetic

CN VIII

vestibulocochlear nerve - sensory

function: hearing and balance

modality: special sensory

CN IX

glossopharyngeal nerve - mixed

function: taste/sensation of tongue, swallowing, parasympathetic stimulation of the parotid salivary gland

monitors blood pressure through sensory receptors

modality: sensory, motor, parasympathetic

CN X

vagus nerve - mixed

function: parasympathetic regulation of thoracic + abdominal organs; contributes to swallowing + voice production

modality: sensory, motor, parasympathetic

CN XI

accessory nerve - motor

function: controls the sternocleidomastoid and trapezius muscles

actions: head rotation and shoulder elevation

modality: motor

CN XII

hypoglossal nerve - motor

function: controls most tongue muscles involves in tongue movement

modality: motor

cranial nerve mnemonic

Old - olfactory

Opie - optic

ocassionally - oculomotor

tries - trochlear

trigonometry - trigeminal

and - abducens

feels - facial

very - vestibulocochlear

gloomy, - glossopharyngeal

vague, - vagus

and - accessory

hypoactive - hypoglossal