Divisions of the Nervous System (11)

What structures make up the brain

2 cerebral hemispheres, diencephalon, branstem, cerebellum

Meninges

Mems that lie btw bone _ soft tissues of nervous sys to protect brain + spinal cord

Dura mater characteristics

Outer layer of meninges made of dct; dural sinuses + epidural space

Arachnoid mater characteristics

Middle web-like layer of meninges containing cerebrospinal fluid in subarachnoid space

Pia mater characteristics

Inner layer of meninges, attached to brain + sc surface, containing bvs + nerves; nourishes CNS

What connects the third ventricle to the lateral

Interventricular foramina

What connects the third ventricle and fourth ventricles

Cerebral aqueduct

What is CSF secreted by

Choroid plexuses: special capillaries of pia mater covered by epend, absorbed by arachnoid granulations after exchanging substances

Volume of CSF

140 mL

Concussion

A mild traumatic brain injury from one-time injury

Chronic traumatic encephalopathy

Mild repetitive TBI from many small injuries over time; symptoms begin years later + have long-lasting effects on memory + behavior

Blast-related brain injury

Severe TBI from explosions in combats; leads to cognitive decline years after injury

What keeps CFS pressure constant + how to relieve pressure

Continuous secretion + reabsorption; insertion of drain into subarachnoid space

What does the brain form from

3 vesicles (cavities)

• Forebrain (prosencephalon) → telencephalon, diencephalon → cerebrum, basal nuclei, diencephalon

• Midbrain (mesencephalon)

• Hindbrain (rhombencephalon) → metencephalon, myelencephalon → cerebellum, pons, medulla oblongata

Cerebrum

Largest part of brain halfed by falx cerebri

• Corpus callosum: connects cerebral hemispheres

• Gyri: ridges/convolutions

• Sulci: shallow grooves in surface

What is the cerebral cortex

Thin layer of gray matter which makes up outermost layer of all outer lobes; contains 75% of neuron cell bodies

What makes up most of cerebrum

White matter under cerebral cortex; contains myelinated axons that connect neuron cell bodies in cc to other portions

What functions is the cerebral cortex responsible for

• Interpreting impulses from sensory organs

• Initiating voluntary movements

• Storying info as memory

• Retrieving stored info

• Reasoning, seat of intelligence, personality

Where is the cutaneous sensory area + what is it responsible for (s)

Parietal lobe; interprets sensations on skin

Where is the sensory speech (Wernicke’s) area + what is it responsible for (s)

Temporal/parietal lobe left hemisphere; understanding + formulating language; Broca’s produce speech

Where is the visual area + what is it responsible for (s)

Occipital lobe; interprets vision

Where is the auditory area + what is it responsible for (s)

Temporal lobe; interprets hearing

Where is the sensory area for taste

Near base of central sulcus includes part of insula

Where is the sensory area for smell

Arises from centers deep within temporal lobes

What are association areas

Regions not motor/sensory that interpret sensory experiences; provide memory, reasoning, verbalization, judgment, emotions

Frontal lobe association areas function

Concentrating, planning, emotional + judging behavior

Parietal lobe association areas function

Understanding speech, choosing words to express

Temporal lobe association areas function

Interpret complex sensory exps, store memories

Occipital lobe association areas function

Analyze + combine visual images w/other sensory exps

Insula association area function

Translate sensory info into emotional responses

Where are the primary motor areas (motor cortex) + function

Frontal lobes; control voluntary muscles

Broca’s area (m)

Anterior to primary motor cortex in left hemisphere that controls speech muscles

Frontal eye field

Above Broca’s area controlling voluntary movements of eyes + lids

What does the dominant hemisphere control

Speech, writing, reading, verbal, analytical, computational; L hem dom in most ppl

What does the nondominant hemisphere control

Nonverbal tasks, motor tasks involving orientation in space, interpreting musical + visual patterns, emotional + intuitive thought process

How does short-term (working) memory work

• Neurons connected in a circuit stimulated repeatedly →

• Impulse flow ceases = memory cease unless enters long-term mem via memory consolidation

How does long-term memory work

• Changes structure/function of neurons, makes new synaptic connections by inc branching of processes

• Long-term potentiation: inc in nt release + effectiveness of synaptic transmission upon repeated stim

What is the basal nuclei

Masses of gray matter deep within cerebral hems that prod dopamine + help control voluntary movement; contains caudate nucleus, putamen, globus pallidus

Parkinsons disease (PD)

Neurons degen in substantia nigra (prod dopamine) so less reaches basal nuclei; no treatment

Where is the diencephalon + what is it made of

Btw cerebral hemispheres above brain stem, made of gray matter

• thalamus, hypothalamus, optic tracts, optic chiasma, infundibulum, posterior pituitary, mammillary bodies, pineal gland

Thalamus function

Receive all sensory impulses (no smell) ascending to cc

Hypothalamus function

Maintain homeostasis by regulating visceral activities like heart rate, bp, body temp, water + electrolyte bal, hunger, body weight, sleep + wakefulness, pituitary function; links nervous + endocrine sys

Limbic system function

Controls emotional responses, feelings, behavior oriented toward survival

Brainstem function + composed of

Connects brain to spinal cord + contains nerve fiber tracts and gray matter masses; midbrain, pons, medulla oblongata

Midbrain

Btw dien + pons containing bundles of fiber that join lwr parts of brainstem + spinal cord w/higher part of brain

• Cerebral aqueduct: connects 3 to 4 ventricle

• Cerebral peduncle: main motor pathways that connect cerebrum to lwr potions of nervous sys

• Corpora quadrigemina: centers for visual + auditory reflexes

• Red nucleus: postural reflexes

Pons function

Relay nerve impulses btw medulla oblongata & cerebrum + cerebrum to cerebellum; helps reg breathing rthyme

Medulla oblongata functions

Contains cardiac, vasomotor, respiratory control center, nonvital reflex control centers (coughing, sneezing, swallowing, vomiting)

What is reticular formation

Network of nerve fibers scattered throughout brainstem that filters incoming sensory info, passing some to cc + discarding unimp ones; arouses cc into wakefulness + decreased activity causes sleep

Non-rapid eye movement (Non-REM) sleep

Slow wave sleep when person is tired, dec activity of reticular formation, restful+ dreamless, reduced bp + respiratory rate

Rapid eye movement (REM) sleep

Aka parafoxical sleep bc some brain areas r active; heart + resp rates irregular + dreams

Cerebellum functions

Integrates sensory info concerning positions of body parts, coordinates skeletal muscle, maintains posture

• Two hemis separated by falx cerebelli

• Vermis connects hemispheres

• Cerebellar cortex (gray matter)

• Arbor vitae (white matter)

• Cerebellar peduncles

What are brain waves

Recordings of fluctuating electrical changes in brain recorded from EEG via electrodes on scalp that detect electrical changes in extracellular fluid of brain

• Alpha: awake, resting eyes closed

• Beta: active mental activity, under tension

• Theta: mostly in children, some in adults during sleep/stress

• Delta: during sleep

Spinal cord

Consists of 31 segments that each give rise to a pair of spinal nerves; grouped according to lvl of vertebra they associated w; nerve pairs numbered from superior to inferior within groups

Longitudinal section of the sc

• Cervical enlargement: supplies nerves to upper limbs

• Lumbar enlargement: supplies nerves to lwr limbs

• Conus medullaris: tapering region below lumbar enlargement

• Filum teminale: cord of ct that anchors sc to coccyx

• Cauda equina: group of lumbar + sacral nerves extending down from conus med in vertebal canal

Cross section of the sc

• Anterior meddian fissure + posterior median sulcus: grooves that extend whole length of sc

• White matter surrounds core of gray matter

• Gray commissure surrounds central canal

• Gm arranged in horns, wm in funiculi

• Posterior roots contain sensory neurons, cells bodies outside sc in posterior root ganglia

• Anterior roots contain motor neurons

Sc functions

Center for spinal reflexes, pathway for impulses to + from brain

What is a reflex

Automatic subconscious response to a stimulus within/outside body; maintain homeo by controlling invol processes

What is a reflex arc

Neural pathway made of a sensory receptor, ≥2 neurons, effector (simple ra only sensory + motor neurons)

Monosynaptic (stretch) reflex

2 neurons (sensory + motor), 1 sc synapse, helps maintain upright posture; ie knee jerk reflex

Withdrawal reflex

Polysnaptic (sensory, interneuron, motor), reciprocal innervation: flexors contract, extensors inhibited; when person touch smth painful

Cross extensor reflex

During withdrawal reflex, flexors on affected (ipsilateral) side contract + extensors inhibited; entensors on contralateral side contract, flexors inhibited

Reflexes usage

Used to assess nervous system condition: extent of ns damage, effectiveness of anesthetics

Ascending tracts

Conduct sensory impulses to brain (pink): fasciculus gracilis + cuneatus, spinothalamic tracts, spinocerebellar tracts

Descending tracts

Conduct motor impulses from brain to effectors via motor neurons (light brown): corticospinal tracts, reticulospinal tracts, rubrospinal tract

Amyotropic lateral sclerosis (ALS)/Lou Gehrig’s Disease

Degen of motor neurons in sc, braintem, cc from overactive microglia that kills neurons or buildup of oxygen-free radicals that neurons/astrocytes cannot counter; no cure

Sc injuries

Compression/distortion of sc → damage/death of neurons

• injury to ascending tracts → sensation loss

• injury to descending tracts → motor function loss, paralysis

Somatic nervous system

Cranial + spinal nerves that connect CNS to skin + skeletal muscles (conscious activities)

Autonomic nervous system

Cranial + spinal nerves that connect CNS to viscera (subconscious activities)

What are nerves and nerve fibers

Nerves = bundles of axons; nerve fibers = axons

Types of connective tissue coverings for nerves

• Endoneurium: loose ct that surrounds individual axons

• Perineurium: lct that surrounds fascicles

• Epineurium: dct that surrounds a group of fascicles

Mixed nerves

contain both sensory + motor nerve fibers; most nerves + all spinal nerves are mixed (except first pair)

Cranial nerves

12 pairs on underside of brain

• First pair has fibers starting in nasal cavity

• Second pair originates in eyes, fibers synapse in thalamus

Cranial nerve I

Olfactory nerve (s): bipolar neurons, olfactory receptor cells pass through cribriform plate + enter olfactory bulbs

Cranial nerve II

Optic nerve (s): neuron cell bodies form ganglion layers of retina + pass through optic foramina of orbits

Cranial nerve III

Oculomotor nerve (mostly m, proprioceptive fibers are s): raises eyelids; motor impulses to involuntary muscles that focus lens, adjust light entering eye (aNS)

Cranial nerve IV

Trochlear nerve (mostly m, proprioceptive fibers are s): smallest pair that motor impulses to one pair of muscles that move the eye

Cranial nerve V

Trigeminal nerve (mx): largest pair that has 3 large sensory branches + motor impulses to mastication muscle

• Ophthalmic: sensory from surface of eyes, tear glands, scalp, forehead, upper eyelids

• Maxillary: upper teeth + gum + lip, palate, face skin

• Mandibular: scalp, jaw skin, lwr teeth + gum + lip

Cranial nerve VI

Abducens nerve (mostly m, proprioceptive fibers are s): motor impulses to one pair of muscles that move the eye

Cranial nerve VII

Facial nerve (mx): sensory from taste receptors + motor impulses to muscles of facial expression, tear + salivary glands

Cranial nerve VIII

Vestibulocochlear aka acoustic/auditory (s)

• Vestibular branch: sensory from equilibrium receptors of ear

• Cochlear branch: sensory from hearing receptors

Cranial nerve IX

Glossopharyngeal (mx)

• Sensory from pharynx, tonsils, part of tongue

• Motor impulses to salivary glands + pharynx muscles

Cranial nerve X

Vagus (mx)

• Somatic motor impulses to pharynx muscle + larynx for speech + swallowing

• Autonomic motor impulses to heart + other viscera of thorax + abdomen

• Sensory from pharynx, larynx, esophagus, thorax + abdomen viscera

Cranial nerve XI

Accessory (mostly m, proprioceptive fibers are s)

• Cranial branch: joins vagus n; motor impulses to soft palate, pharynx, laynx muscles

• Spinal branch: motor to muscles of neck + back

Cranial nerve XII

Hypoglossal (mostly m, proprioceptive fibers are s): motor impulses to muscles of the tongue for speaking, chewing, swallowing

How many pairs of spinal nerves are there

31 pairs

• 8 cervical (C1-C8)

• 12 thoracic (T1-T12)

• 5 lumbar (L1-L5)

• 5 sacral (S1-S5)

• `1 coccygeal nerve

What is the cauda equina formed by

descending roots of lumbar, sacral, coccygeal nerves

What is the dermatome of spinal nerves

An area of skin innervated by sensory nerve fibers of particular sn (in all sn below C1)

What does the anterior (ventral/motor) root of a spinal n contain

Axons of motor neurons whose cell bodies are in the sc

What does the posterior (dorsal/sensory) root of a spinal n contain

Axons of sensory neurons; posterior root ganglion contains cell bodies of sensory neurons that conduct impulses from periphery into spinal cord

What are spinal n formed by

Union of anterior + posterior roots

What are nerve plexuses

Complex network formed by anterior rami (branches) of sn; not in T1-T12 because anterior rami become intercostal n

Cervical plexus

Formed by anterior rami of C1-C4 lying deep in the neck, supplies neck muscles + skin'; C3-C5 nerve roots contribute to phrenic n → transmit motor pulses to diaphragm

Brachial plexus

Formed by anterior rami C5-T1 lies deep in shoulder

• Musculocutaneous n: supple anterior arm muscles, forearm skin

• Ulnar + median n: forearm + hand muscles, hand skin

• Radial n: post arm muscles, forearm + hand skin

• Axillary n: muscle + skin of ant, lat, post arms

Lumbosacral plexus

Formed by ant branches of L1-S4 roots

• Obturator n: supply motor impulses to adductors

• Femoral n: motor impulses to ant thigh musc, sens impulses from thigh + leg skin

• Sciatic n: muscle + skin of thighs, legs, feet; largest + longest n

Whiplash

Sudden bending of the neck, compression of c plexus n → persistent headache, neck pain

Thoracic outlet syndrome

Pressure on b plexus from continuous flexion of arm (painting/typing) → neck, shoulder, upper limb pain

Sciatica

Compression of intervertebral disc in lumbar region → pain in lwr back, gluteal region, thigh, calf, foot

Carpal tunnel syndrome

Repeated movements of hand inflame tendons that pass through carpal tunnel (space btw wrist bones); swelling in tendons compresses median n → arm + wrist pain

What does the ANS control

Visceral activities + preps body for exercise