Neuro Anatomy

Question 1

Telencephalon

Answer 1

“cerebral hemispheres”

consists of 6 lobes on each side
frontal
parietal
temporal
occipital
insular
limbic

Question 2

Frontal lobe

Answer 2

Precentral gyrus: primary motor cortex for voluntary muscle activation

Prefrontal cortex: controls emotions and judgements

Broca’s area: controls motor aspects of speech

Question 3

Parietal lobe

Answer 3

Postcentral gyrus: primary sensory cortex for integration of sensation
-receives fibers conveying touch, proprioception, pain and temperature sensations from OPPOSITE side of the body

Question 4

Temporal lobe

Answer 4

Primary auditory cortex: receives/processes auditory stimuli

Associative auditory cortex: processes auditory stimuli

Wenicke’s area: language apprehension

Question 5

Occipital lobe

Answer 5

Primary visual cortex: receives/processes visual stimuli

Visual association cortex: processes visual stimuli

Question 6

Insula

Answer 6

deep within lateral sulcus, associated with visceral functions

Question 7

Limbic system

Answer 7

consists of the limbic lobe (cingulate, parahppocampal and subcallosal gyri), hippocampal formation, amygdaloid nucleus, hypothalamus and anterior nucleus of the thalamus

phylogenetically the oldest part of the brain- concerned with instincts and emotions contributing to preservation of the individual

Basic functions: feeding, aggression, emotions and endocrine aspects of sexual response

Question 8

White matter

Answer 8

myelinated nerve fibers located centrally

1-Transverse (commissural) fibers: interconnect the 2 hemispheres, including corpus callosum (the largest), anterior commissure and hippocampal commissure.

2-Projection fibers: connect cerebral hemispheres with other portions of the brain and SC

3- Association fibers: connect different portions of the cerebral hemispheres, allowing cortex to function as integrated whole

Anterior, lateral and posterior white columns or funiculi in the SC

Question 9

Basal ganglia

Answer 9

masses of gray matter deep within cerebral hemispheres
-includes: striatum (caudate nucleus, nucleus accumbuns, putamen), globus pallidus (external & internal segment), subthalamic nucleus and substantia nigra.

“Lenticular nucleus” = putamen and globus pallidus

forms an associated motor system (extrapyramidal system) with other nuclei in the subthalamus and the midbrain

consists of multiple circuits:
1- oculomotor circuit (caudate loop)
2- motor loop (putamen loop)
3-limbic circuit

Question 10

Oculomotor circuit

Answer 10

“caudate loop”
associated motor system of the BG

originates in frontal and supplementary motor eye fields

projects to caudate

functions with saccadic eye movements

Question 11

Motor loop

Answer 11

“Putamen loop”
associated motor system of the BG

originates in precentral motor and postcentral somatosensory areas

projects to and excites putamen neurons; putamen cells inhibit globus pallidus neurons, which in turn boosts activity in the ventral lateral nucleus and supplemental motor area

functions to scale amplitude and velocity of movements reinforces selected pattern, suppressed conflicting patterns; preparatory for movement

Question 12

Limbic circuit

Answer 12

associated motor system of the BG

originates in prefrontal and limbic areas of cortex to BG to prefrontal cortex

functions to organize behaviors (executive functions, problem solving, motivation) and for procedural functions

Question 13

Diencephalon consists of:

Answer 13

1-thalamus
2-subthalamus
3-hypothalamus
4-epithalamus

Question 14

thalamus

Answer 14

sensory nuclei: integrate and relay sensory information from body, face, retina, cochlea, and taste receptors to cerebral cortex and subcortical regions
*smell (olfaction) is only exception

Motor nuclei: relay motor info from cerebellum and globus pallidus to percentile motor cortex

Other nuclei: assist in integration of visceral and somatic functions

Question 15

Subthalamus

Answer 15

involved in control of several functional pathways for sensory, motor and reticular function

Question 16

Hypothalamus

Answer 16

integrates and controls the functions of the ANS and the neuroendocrine system

maintains body homeostasis

Question 17

Epithalamus

Answer 17

habenular nuclei: integrate olfactory, visceral and somatic afferent pathways

pineal gland: secretes hormones that influence the pituitary gland and several other organs; influences circadian rhythm

Question 18

Brainstem consists of:

Answer 18

1-midbrain (mesencephalon)

• connects pons to cerebrum
• superior peduncle connects midbrain to cerebellum

2- pons
-connects medulla oblongata to midbrain- allows passage of important ascending and descending tracts

3- medulla oblongata
-connects SC to pons

Question 19

midbrain

Answer 19

“mesencephalon”
connects pons to cerebrum

superior peduncle connects midbrain to cerebellum

contains cerebral peduncles (2 lateral halves), each divided into an anterior part or basis (crus cerebra and substantia nigra) and a posterior part (tegmentum)

Tegmentum contains all ascending tracts and some descending tracts; the red nucleus receives fibers from the cerebellum; is the origin for the rubrospinal tract, important for coordination;
-contains CN nuclei: oculomotor and trochlear

Substantia nigra is a large motor nucleus connecting with the BG and cortex; important in motor control and muscle tone

Superior and inferior colliculi

Periaqueductal gray: contains endorphin-producing cells (important for the suppression of pain) and descending autonomic tracts

Question 20

Superior vs. inferior colliculi

Answer 20

Superior: important relay station for vision and visual reflexes

Inferior: important relay station for hearing and auditory reflexes

Question 21

Pons

Answer 21

connects the medulla oblongata to the midbrain, allowing passage of important ascending and descending tracts

middle cerebellar peduncle -anterior basal acts as a bridge to cerebellum

midline raphe nuclei project widely and are important for modulating pain and controlling arousal

tegmentum contains several important CN nuclei: abducens, trigeminal, facial, vestibulocochlear

Question 22

Medulla oblongata

Answer 22

connects SC with pons

contains relay nuclei of dorsal columns (gracilis and cuneatus); fibers cross to give rise to medial lemniscus

inferior cerebellar peduncle relays dorsal spinocerebellar tract to cerebellum

corticospinal tracts cross (decussate) in pyramids

Medial longitudinal fasciculus arises from vestibular nuclei and extends t/o brainstem and upper cervical SC; important for control of head movements and gaze stabilization (vestibular-ocular reflex)

olivary nuclear complex connects cerebellum to brainstem and is important for voluntary movement control

contains several important CN nuclei: hypoglossal, dorsal nucleus of vagus and vestibulocochlear

contains important centers for vital functions: cardiac, respiratory and vasomotor centers

Question 23

Cerebellum

Answer 23

located behind dorsal pons and medulla in posterior fossa

• joined to brainstem by 3 pairs of peduncles
• comprises 2 hemispheres and midline vermis

Lobes:

1-Archicerebellum (flocculonodular lobe)

• connects with vestibular system
• concerned with equilibrium and regulation of muscle tone; helps coordinate vestibule-ocular reflex

2- Paleocerebellum (rostral cerebellum, anterior lobe; spinocerebellum)

• receives input from proprioceptive pathways
• concerned with modifying muscle tone and synergistic actions of muscles
• important in maintenance of posture and voluntary movement

3-Neocerebellum (cerebellar hemisphere, posterior lobe, pontocerebellum)

• receives input from cortiopontocerebellar tracts and olivocerebellar fibers
• concerned with the smooth coordination of voluntary movements
• ensures accurate force, direct and extent of movement
• important for motor learning, sequencing of movements and visually triggered movements
• may have role in assisting cognitive function and mental imagery

Question 24

central gray matter consists of:

Answer 24

Anterior horns: contain cell bodies that give rise to efferent (motor) neurons

• alpha motor neurons to affect muscles
• gamma motor neurons to affect muscle spindles

Posterior horns: contain afferent (sensory) neurons with cell brides located in the dorsal root ganglia

Central gray commissure with central canal

2 enlargements: cervical and lumbosacral for origins of nerves of UE and LEs

Lateral horn is found in thoracic and upper lumbar segments for preganglionic fibers of the ANS

Question 25

Ascending fiber systems/sensory pathways

Answer 25

1- Dorsal columns/medial lemniscal system: 2- Spinothalamic tracts 3-Spinocerebellar tracts 4- Spinoreticular tracts

Question 26

Dorsal columns/medial lemniscal system:

Answer 26

convey sensations of proprioception, vibration and tactile discrimination divided into: 1-fasciculus cuneatus (UE tracts, laterally located) 2- Faciculus gracilis (LE tracts, medially located neurons ascend to medulla where fibers cross = lemniscal decussation) to form medial lemniscus as ascend to thalamus and then to somatosensory cortex

Question 27

Spinothalamic tracts:

Answer 27

convey sensations of pain and temperature (lateral spinothalamic), and crude touch (anterior spinothalamic) tracts ascend 1 or 2 ipsilateral SC segments (Lissauer's tract), synapse and cross in SC to opposite side and ascend in ventrolateral spinothalamic system

Question 28

Spinocerebellar tracts

Answer 28

convey proprioception info from muscle spindles, GTO and touch and pressure receptors to cerebellum for control of voluntary movements Dorsal spinocerebellar tract ascends to ipsilateral inferior cerebellar peduncle Ventrospinocerebellar tract ascends to contralateral and ipsilateral superior cerebellar peduncle

Question 29

Spinoreticular tracts

Answer 29

convey deep and chronic pain to reticular formation of brainstem via diffuse, polysynaptic pathways

Question 30

Descending fiber systems (motor pathways)

Answer 30

1- Corticospinal tracts 2- Vestibulospinal tracts 3- Rubrospinal tracts 4- Reticulospinal system 5- Tectospinal tract

Question 31

Corticospinal tract

Answer 31

arise from primary motor cortex, descend in brainstem, cross in medulla (pyramidal decussation), via lateral corticospinal tract to ventral gray matter (anterior horn cells) 10% of fibers do not cross and travel in anterior corticospinal tract to cervical and upper thoracic segments important for voluntary motor control

Question 32

Vestibulospinal tracts

Answer 32

arise from vestibular nucleus and descend to SC in lateral (uncrossed) and medial (crossed and uncrossed) vestibulospinal tracts important for control of muscle tone, antigravity muscles and postural reflexes

Question 33

Rubrospinal tracts

Answer 33

arise in contralateral red nucleus and descend in lateral white columns to spinal gray assist in motor function

Question 34

Reticulospinal system

Answer 34

arises in the reticular formation of the brainstem and descends (crossed and uncrossed) in ventral and lateral columns terminates both on dorsal gray (modifies transmission of sensation, especially pain) and on ventral gray (influences gamma motor neurons and spinal reflexes)

Question 35

Tectospinal tract

Answer 35

arises from superior colliculus (midbrain) and descends to ventral gray assists in head turning responses to visual stimuli

Question 36

Autonomic Nervous System (ANS)

Answer 36

concerned with innervations of involuntary structures: smooth muscle, heart, glands helps maintain homeostasis- constant internal body environment DIVISIONS: (both have afferent and efferent nerve fibers; pre & post ganglionic fibers) 1- Sympathetic (thoracolumbar division, T1-L2) - prepares body for fight or flight, emergency responses - increases HR and BP, constricts peripheral blood vessels and redistributes blood - inhibits peristalsis (intestinal contraction) 2-Parasympathetic (craniosacral division, CN III, VII, IX, X; pelvic nerves) - conserves and restores homeostasis - slows HR and reduces BP - increases peristalsis and glandular activity Autonomic plexuses: cardiac, pulmonary, celiac (solar), hypogastric, pelvic Modulated by brain centers: 1- Descending autonomic system: arises from control centers in hypothalamus and lower brainstem (cardiac, respiratory, vasomotor) and projects to preganglionic ANS segments in thoracolumbar (sympathetic) and craniosacral (parasympathetic) segments 2- CN: visceral afferent sensations via glossopharyngeal and vagus nerves; efferent outflow via oculomotor, facial, glossopharyngeal and vagus nerves

Question 37

meninges

Answer 37

3 membranes that envelop the brain 1- dura mater: outer, tough, fibrous membrane attached to inner surface of cranium -forms falx and tentorium 2- Arachnoid: delicate, vascular membrane Subarachnoid space: contains cerebrospinal fluid (CSF) and cisterns, major arteries 3- Pia mater: thin, vascular membrane that covers the brain surface -forms tela chloridea of ventricles

Question 38

brain ventricles

Answer 38

4 cavities/ventricles filled with CSF and communicate with each other and with SC canal 2 lateral ventricles: large, irregularly shaped with anterior, posterior and inferior horns -communicates with 3rd ventricle through foramen of Monro 3rd ventricle: located posterior and deep between the 2 thalami -communicates with 4th ventricle through cerebral aqueduct 4th ventricle: pyramid-shaped cavity located in the pons and medulla -foramina of Luschka and Magendie communicate with 4th ventricle through subarachnoid space

Question 39

Cerebrospinal fluid

Answer 39

provides mechanical support (cushions brain) controls brain excitability by regulating ionic composition aids in exchange of nutrients and waste produces produced in choroid plexuses in ventricles

Question 40

Blood brain barrier

Answer 40

selective restriction of blood borne substances from entering the CNS associated with capillary endothelial cells

Question 41

Blood supply

Answer 41

brain= 2% of body weight with a circulation of 18% total blood volume Carotid system: internal carotid arteries arise off common carotids and branch to form anterior and middle cerebral arteries -supplies a large area of brain and many deep structures Vertebrobasilar system: vertebral arteries arise off subclavian arteries and unite to form the basilar artery - this vessel bifurcates into 2 posterior cerebral arteries - supplies the brainstem, cerebellum, occipital lobe and parts of thalamus Circle of Willis: formed by anterior communicating artery -connecting the 2 anterior cerebral arteries and the posterior communicating artery, connecting each posterior and middle cerebral artery Venous drainage: includes cerebral veins and dural venous sinuses

Question 42

Neuron structure

Answer 42

cell bodies: genetic center -dendrites: receptive surface area to receive info via synapses axons: conduct impulses AWAY from cell body (1 way conduction) Synapses: allow communication between neurons - chemical neurotransmitters are release (chemical synapses) - electrical signals pass directly from cell to cell (electrical synapses) neuron groupings/types - nuclei are compact groups of nerve cell bodies; in the peripheral NS these groups are call ganglia - projection neurons carry impulses to other parts of the CNS - interneurons are short relay neurons - axon bundles are called tracts or fasciculi; in the SC, collections of tracts are called columns or funiculi Neuroglia= support cells that don't transmit signals - important for myelin and neuron production - maintenance of K+ levels and repute of neurotransmitters after neural transmission at synapses

Question 43

Neuron function/ neuronal signaling

Answer 43

resting membrane potential: positive outside, negative inside (~ -70 MV) action potential: increased permeability of Na+ and influx into cell with outflow of K+ results in polarity changes (inside to ~ +35 mV) and depolarization; generation of an action potential is all or none) conduction velocity is proportional to axon diameter; largest myelinated fibers conduct fastest repolarization results from activation of K+ channels many axons are covered with myelin with small gaps (nodes of Ranvier) where myelin is absent; action potential jumps from one node to the next (saltatory conduction); myeline functions to increase speed of conduction and conserve energy

Question 44

Nerve fiber types

Answer 44

A fibers: large, myelinated, fast-conducting - alpha: proprioception, somatic motor - beta: touch, pressure - gamma: motor to muscle spindles - delta: pain, temp, touch B fibers: small, myelinated, conduct less rapidly; preganglionic autonomic C fibers: smallest, unmyelinated, slowest conducting - dorsal root: pain, reflex responses - sympathetic: postganglionic sympathetics

Question 45

peripheral nerves

Answer 45

LMN motor/efferent fibers originate from motor nuclei (cranial nerves) or anterior horn cells (Spinal nerves) sensory/afferent fibers originate in cells outside of brainstem or spinal cord with sensory ganglia (cranial nerves) or dorsal root ganglia (spinal nerves) ANS fibers: sympathetic fibers at thoracolumbar spinal segments and parasympathetic fibers at craniosacral segments

Question 46

Cranial nerves

Answer 46

12 pairs; all distributed to the head and neck (except CN X which is distributed to the thorax and abdomen) ``` I: Olfactory II: Optic III: Oculomotor IV: Trochlear V: Trigeminal VI: Abducens VII: Facial VIII: Vestibulocochlear IX: Glossopharyngeal X: Vagus XI: Spinal accessory XII: Hypoglossal ```

Question 47

CN: pure sensory

Answer 47

pure sensory, carry special senses of smell, vision, hearing and equilibrium I: olfactory II: optic VIII: vestibulocochlear

Question 48

CN: pure motor

Answer 48

pure motor, controlling eye movements and pupillary constriction III: oculomotor IV: trochlear VI: abducens pure motor, innervating SCM, trapezius and tongue XI: spinal accessory XII: hypoglossal

Question 49

CN: mixed motor and sensory

Answer 49

mixed motor and sensory involved in: - chewing (V) - facial expression (VII) - swallowing (IX, X) - vocal sounds (X) sensations: - from head (V, VII, IX) - alimentary tract, heart, vessels and lungs (IX, X) - taste (VII, IX, V)

Question 50

CN: carry parasympathetic fibers of ANS

Answer 50

III- oculomotor VII- facial IX- glossopharyngeal X- vagus involved in: - control of smooth muscles of inner eye (III) - salivatory and lacrimal glands (VII) - parotid gland (IX) - muscles of the heart, lung and bowel (X)

Question 51

CN I

Answer 51

Olfactory nerve smell Anosmia= inability to detect smells -seen with frontal lobe lesions

Question 52

CN II

Answer 52

Optic nerve - vision- central and peripheral visual acuity - pupillary reflexes blindness myopia= impaired far vision presbyopia= impaired near vision homonymous hemianopsia= visual field deficit

Question 53

CN III

Answer 53

Oculomotor nerve - extraocular movements: turns eye up, down and in - pupillary reflexes - lifts eyelid stabismus= eye deviates from normal conjugate position (eye pulled outward by CN VI) Mydriasis= dilated pupil loss of light and accommodation reflexes Ptosis= drooping eyelid

Question 54

CN IV

Answer 54

Trochlear nerve -turns adducted eye down eye can't look down when adducted diplopia looking down- difficulty with stairs

Question 55

CN V

Answer 55

Trigeminal nerve - Sensory: face, cornea - Motor: temporal and masseter muscles

Question 56

CN VI:

Answer 56

Abducens -pulls out laterally Esotropia= pulls eyes inward

Question 57

CN VII:

Answer 57

Facial nerve - Motor: facial expression (eyebrows, frown, smile, close eyes, puff cheeks) - Sensation: anterior 2/3 taste of tongue; glands and mucosa of the pharynx, palate, nasal cavity, paranasal sinuses, submaxillary and sublingual gland Bell's palsy

Question 58

CN VIII

Answer 58

Vestibulocochlear nerve - vestibular: eye head coordination, vestibular-ocular reflex - cochlear function: auditory acuity vertigo dysequilibrium nystagmus deafness/impaired hearing tinnitus sensorineural loss: sound heard in good ear conductive loss: sound heard through bone is equal to or longer than air

Question 59

CN IX

Answer 59

Glossopharyngeal nerve - phonation - swallowing - palatal, pharynx control - gag reflex - posterior 1/3 of tongue taste ``` dysphonia= difficulty with speech dysphagia= difficulty swallowing ```

Question 60

CN X

Answer 60

Vagus nerve - phonation - visceral sensations and reflexes - cardiac depressor - bronchoconstrictor - GI tract peristalsis and secretion palpitation, tachycardia, vomiting, slowing of respiration, ipsilateral paralysis of soft palate and larynx, hoarseness, anesthesia of the larynx

Question 61

CN XI

Answer 61

Spinal Accessory nerve - Carotid/cranial part: deglutition and phonation - Spinal part: trapezius and SCM innervation

Question 62

CN XII

Answer 62

Hypoglossal nerve -tongue movement dysarthria= difficulty articulating words deviates to weak side on protrusion

Question 63

Spinal nerves

Answer 63

``` 31 pairs- correspond to vertebral segments; each has a ventral and dorsal root 8 cervical 12 thoracic 5 lumbar 5 sacral 1 coccygeal ``` Ventral root: efferent/motor fibers to voluntary muscles (alpha and gamma motor neurons), and to viscera, glands and smooth muscles (preganglionic ANS fibers) Dorsal root: afferent/sensory fibers from sensory receptors from skin, joints and muscles; each dorsal root possesses a dorsal root ganglion (cell bodies of sensory neurons); no dorsal root for CI nerve roots exit from the vertebral column through the intervertebral foramina - Cervical spine: numbered roots exit horizontally above the corresponding vertebral body - Thoracic, lumbar and sacral spine: roots exit below the corresponding vertebral body after emerging from the intervertebral foramen, each spinal nerve divides into a large anterior ramis (supplying the muscles and skin of the ant/lat body wall and limbs) and a small posterior ramis (supplying muscles and skin of the back); each ramus contains motor and sensory fibers Anterior rami joint at the root of the limbs to form nerve plexuses - Cervical plexus: C1-4 nerve roots - Brachial plexus: C5-T1 - Lumbar plexus: T12-L4 - Sacral plexus: L4-S3

Question 64

dermatome

Answer 64

specific segmental skin area innervated by sensory spinal axons

Question 65

myotome

Answer 65

skeletal muscles innervated by motor axons in a given spinal root

Question 66

spinal level reflexes

Answer 66

stretch (myotatic) reflex - reciprocal inhibition - reciprocal innervation inverse stretch (myotatic) reflex gamma reflex loop flexor (withdrawal) reflex Crossed extension reflex

Question 67

Stretch (myotatic) reflex

Answer 67

stimulus: muscle stretch reflex arc: afferent Ia fiber from muscle spindle to alpha motor neurons projecting back to muscle or origin (monosynaptic) functions for maintenance of muscle tone, support agonist muscle contraction and provide feedback about muscle length clinically, sensitivity of the stretch reflex and intactness of SC segment are tested by DTR reciprocal inhibition: via an inhibitory interneuron, the same stretch stimulus inhibits the antagonist muscle reciprocal innervation: describes the effects of a stretch stimulus on agonist (autogenic facilitation), antagonist (reciprocal inhibition) and synergistic muscles (facilitation)

Question 68

Inverse stretch (myotatic) reflex

Answer 68

stimulus: muscle contraction reflex arc: afferent Ib fiber from GTO via inhibitory interneuron to muscle of origin (polysynaptic) functions to provide agonist inhibition, diminution of force of agonist contraction, stretch-protection reflex

Question 69

gamma reflex loop

Answer 69

stretch reflex forms part of this loop alows muscle tension to come under control of descending pathways (reticulospinal, vestibulospinal and others) descending pathways excite gamme motor neurons, causing contraction of muscle spindle, and in turn increased stretch sensitivity and increased rate of firing from spindle afferents; impulses are then conveyed to alpha motor neurons

Question 70

flexor (withdrawal) reflex

Answer 70

stimulus: cutaneous sensory stimuli reflex arc: cutaneous receptors via interneurons to largely flexor muscles; multisegmental response involving groups of muscles (polysynaptic) functions as a protective withdrawal mechanism to remove body part from harmful stimuli

Question 71

crossed extension reflex

Answer 71

stimulus: noxious stimuli and reciprocal action of antagonists; flexors of one side are excited, causing extensors on same side to be inhibited; opposite responses occur in opposite limb reflex arc: cutaneous and muscle receptors diverging to many SC motor neurons on same and opposite side (polysynaptic) function: coordinates reciprocal limb activities such as gait.