Neuroanatomy Exam #3

NT= neurotransmitter, ANS = autonomic nervous system, PANS = parasympathetic autonomic nervous system, SANS = sympathetic autonomic nervous system, HR = heart rate, BP = blood pressure

what are the functions of the ANS?

• regulates functions that normally don't require conscious awareness (ex: digestion, HR, sweating, respiratory rate, etc.)

• controls function of cardiac and smooth muscle glands

What are the 3 divisions of the ANS?

1. parasympathetic

2. sympathetic

3. enteric

describe the sympathetic nervous system. (what are its effects on the body, what type of response does it initiate)

• fight or flight response

• when it dominates = > HR, >BP, >breathing, dialated pupils, < gut motility

• blood diverted to SKM away from digestive system

• expends energy

describe the parasympathetic nervous system. (What are its effects on the boyd, what type of response does it initiate, etc.)

• rest and digest

• when it dominates = <HR, <BP, <respiration rate, constricted pupils, increased blood flow to digestive system

• conserves energy

describe the enteric nervous system (what does it include, where are its components, and what can it be regulated by)

• includes sensory, motor, and interneurons in walls of viscera

• call components outside of CNS

• normally regulated by SANS and PANS, but can function independently

During homeostasis, which components of the ANS are functioning?

most organs recieve input from both SANS and PANS. During most circumstances all 3 are operating at some leel

Where do visceral afferents send their information to in the brain? How does it get their?

• Information sent to hypothalamus, which controls the ANS

• info sent via nucleus of solitary tract

what are the two types of efferents in the visceral motor system and what controls them?

• PANS and SANS divisions

• controlled by hypothalamus

Describe pregangliongic sympathetic neurons (where are they located, how long are they, and what NT do they release)

• located in interomedial lateral cell column of thoracolumnar SC between T1-L2/3

• short axons

• release Ach

Describe the post-ganglion sympathetic neurons (where are there cell bodies, how long are they, what NT do they release)

• CB's located in sympathetic chain ganglia or prevertebral ganglia

• long axons

• release NE (norepinephrine)

Some pre-ganglionic sympathetic neurons synapse directly on to their target. What is this target and what is the effect?

• adrenal medulla → then releases NE into systemic ciruclation

in general, describe the effects of the SANS

widespread and long-lasting

Where are the preganglionic parasympathetic neurons located?

brainstem (CN III, VII, IX, or X) or sacral SC (S2-S4)

how long are the axons of preganglionic PS neurons and what NT do they release?

• short preganglionic axons

• release Ach

what 4 cranial nerves contain axons of preganglionic parasympathetic neurons?

III, VII, IX, X

what three things can visceral sensory afferents detect?

1. distortion

2. inflammation

3. tissue damage

why is visceral pain poorly localized?

fewer afferents and large receptive fields

what is referred pain?

the process by which visceral pain is referred to more superficial areas (perceived as coming from somewhere else than where the pain is actually coming from) due to connections and the fact that visceral pain is less common

why and how does referred visceral pain occur?

• visceral and somatic afferents both have CBs in DRG, then synapse onto the same secondary afferents, cross midline, and ascend in ALS

• this pathways is used to interpretating activity as pain coming from more superficial areas → when visceral afferents activate the pathway, pain is interpreted as a more superficial sensation

describe how both the parasympathetic and sympathetic nervous systems control iris/pupil size?

• sympathetic = iris dialator muscles

• parasympathetic = iris constrictor muscles

• iris is constantly changing sizes to due to influence of ANS

what causes Horner's Syndrome? What are the signs and symptoms of this?

caused by damage along head and neck descending sympathetic pathways = hypothalamic efferents, pre/post-ganglionic neurons

• miosis (constriction) of pupil

• ptosis = drooping eyelid

• ipsilateral anhydrosis (decreased or loss of sweating on ipsi side of lesion)

what must all cranial nerves do in order to be considered a cranial nerve?

exit the cranium through the foramina

what kind of modalities can CN's carry, what is the ONLY branch of the the ANS that CN's can carry?

ONLY EVER CARRY PARASYMPATHETIC

• motor, sensory or both fiber types

what 2 pathways comprise the corticobulbar tract?

two neuron white matter cranial nerve motor pathways

use a pneumonic to list all the modalities for the cranial nerves

Some: CN I = sensory

Say: CN II = sensory

Marry: CN III = motor

Money: CN IV = motor

But: CN V = both

My: CN VI = motor

Brother: CN VII = both

Says: CN VIII = sensory

Big: CN IX = both

Brains: CN X = both

Matter: CN XI = Motor

More: CN XII = motor

What cranial nerve(s) exit from the cribiform plate? what bone is this in?

CN I olfactory nerve, ethmoid bone

olfaction

What cranial nerve(s) exit from the optic canal? what bone is this in?

CN II optic nerve, sphenoid bone

vision

What cranial nerve(s) exit from the superior orbital fissure what bone is this in?

sphenoid bone

all related to movements of eyeball or sensation of eyball area:

• CN III (occulomotor n.)

• CN IV (trochlear n.)

• CN V1 opthalmic division of trigeminal

• CN VI (abducens n.)

What cranial nerve(s) exit from the foramen rotundum? what bone is this in?

sphenoid bone

maxillary nerve CN V2

What cranial nerve(s) exit from the foramen ovale? what bone is this in?

sphenoid bone

mandibular n. CN V3

What cranial nerve(s) exit from the internal acoustic meatus? what bone is this in?

temporal bone

• CN VII, Facial n.

• CN VIII, vestibulocochlear n.

What cranial nerve(s) exit from the jugular foramen? what bone is this in?

between temporal bone anteriorly and occiptal bone posteriorly

• CN IX, glossopharyngeal n.

• CN X, vagus n.

• CN XI, accessory n.

What cranial nerve(s) exit from the hypoglossal canal? what bone is this in?

occipital bone

• CN XII, hypoglossal n.

Describe the fiber types, functions, foraminal exit, and nucleus location/where fibers arise from of CN XI accessory n.?

fiber types: motor

fxn: somatic motor innervation to sternocleidomastoid and trapezius

foraminal exit: jugular foramen

nuclei location: medulla oblongata/SC jxn to C6 of SC

what is the pathway of the accessory nerve CN XI up into and out of the brain?

into skull via foramen magnum, exit through jugular foramen

why are CNs exiting from the jugular foramen at risk for being compressed? Which 3 CN's are these?

• next to jugular vein and carotid artery which may swell

• Cn IX, X, and XI

what is unique about the nucleus of CN XI?

NOT a part of the corticobulbar tract, unlike most motor fibers

which way does the SCM (sternocleidomastoid m.) turn the head?

contralaterally (L SCM turns head to R)

A lesion in the L CN XI would result in:

• weakness of shrugging IPSI, L shoulder (L trap is dysfunctional)

• weakness turning head to R (contra dxn), L SCM is dysfunctional

what are the 3 main branches of the hypoglossal nerve (CN XII)? What do these branches innervate? And where do the fibers originate?

1. meningeal branch

   • inn: floor and post. wall dura mater of post. cranial fossa

   • fibers from spinal n. C2

2. superior root of the ansa cervicalis

   • inn: infrahyoids

   • fibers from C1 and C2

3. lingual branch

   • inn: styloglossus, hyoglossus, intrinsic tongue muscles

Describe CN XII in the corticobulbar tract (UMNs, nucleus, LMN).

• UMN: motor Cx → hypoglossal nucleus

• nucleus located near caudal aspect of brain stem

• recieves bilateral inn. but contralateral inn. is dominant

• LMN: courses ipsilaterally from nucleus to target muscles

a R sided tongue defecit indicates a lesion on which side of the hypoglossal tract?

lesion on L

where is the location of the CN XII nucleus?

lateral to midline of the caudal brainstem

• CN X's motor nucleus is immediately lateral to this

what two CNs are affected by caudomedial brainstem lesions?

motor fibers of CN X and CN XII

Supranuclear injury causes weakness of _______ tongue muscles.

likely motor cx (stroke) injury, causes CONTRALATERAL tongue weakness

infranuclear injury causes weakness of the_________ tongue muscles

(hypoglossal canal chondroma) causes IPSILTERAL weakness