CNS - Exam 3 (Final)

The midbrain is also known as the:

mesencephalon

What is found on the posterior roof of the midbrain?

tectum

The tectum is located ________ to the cerebral aqueduct (of Sylvius)

posterior

The cerebral aqueduct is a channel for _______ between the _______ and _______ ventricles

CSF

third and fourth

What surrounds the cerebral aqueduct? Why is it important?

periaqueductal gray, nuclei for CN 3 and 4 are found in/near this area

The tectum is composed of _________ made up of __________

quadrigeminal plate, 4 collicular bodies (2 superior, 2 inferior)

The 2 superior colliculi of tectum function in what pathway?

2 inferior?

visual (motion)

auditory (hearing)

T/F? The optic tract goes through the thalamus

False, bypasses thalamus to superior colliculi where nucleus of origin is for tectospinal tract

Explain the route of the motion (visual) reflex pathway

optic tract

bypasses thalamus

superior colliculus

tectospinal tract

Explain the route of the auditory reflex pathway?

lateral lemniscus

bypasses thalamus

inferior colliculus

superior colliculus

tectospinal tract

ALL conscious sensory info goes through the ___________

thalamus (MGB and LGB)

What 3 things are found in the cerebral peduncles?

tegmentum

substantia nigra

crus cerebri

Describe the location of the tegmentum:

most posterior aspect of the anterior part of the midbrain

The tegmentum contains the nuclei of origin for which cranial nerves?

3 and 4

The reticular formation of the brain is found in what midbrain structure?

tegmentum

Where is the red nucleus and rubrospinal tract found?

tegmentum of midbrain

The rubrospinal tract deals with what?

contralateral flexor musculature

Both rubrospinal and tectospinal tracts function...

below the level of consciousness (extrapyramidal)

The tectospinal tract is involved in what 2 protective reflexes?

turn our head away from loud sounds and from objects moving in our field of vision

The tectospinal tract influences neurons through which cranial nerve? It innervates which muscles?

spinal accesory nerve (11)

SCM and Trapezius

T/F? Lesions of tectospinal tract impair voluntary eye movements

False - only the perception of motion

What are the 2 regions of the red nucleus?

What are key characteristics of both?

Parvocellular - extends to the subthalamus of diencephalon, highly vascular (think blood supply)

Magnocellular - where rubrospinal tracts come from

Where is the substantia nigra located?

between tegmentum and crus cerebri

T/F? Substantia nigra secretes melanin

False!

melanin gives it black color

it secretes dopamine

Dopamine is needed to make movements _____________

smooth and effective (extrapyramidal)

If substantia nigra is damaged, what is the clinical result?

Parkinson's (lack of dopamine)

Parkinson's is associated with what symptoms?

tremor at REST, abnormal gait, loss of speech (in severe cases)

Where is dopamine stored?

caudate + putamen

Why are dopamine injections ineffective for Parkinson's patients?

What can be used instead?

dopamine will NOT cross BBB

L-dopa

Describe the location of crus cerebri:

ventrolateral aspect of cerebral peduncles (of midbrain)

The crus cerebri is composed of what?

descending pyramidal tract fibers (from cerebral cortex)

What is the function of descending pyramidal tract fibers?

initiate skilled voluntary movement

Which structure in the midbrain contains fibers that initiate skilled voluntary movement?

crus cerebri - descending pyramidal tracts (cortico-)

Axons from corticomesencephalic tract terminate on __________

What do they initiate?

CN nuclei 3 and 4

voluntary motor movements of eyes

What are 4 unique characteristics associated with CN 4?

smallest CN

ONLY CN with apparent origin on posterior side

ONLY CN who's fibers cross

travels FURTHER in the cranial vault than any other CN

Where is CN 4 apparent origin (be specific)

mid dorsal aspect, inferior to inferior colliculus

CN 4 supplies what muscle?

superior oblique (trochlear muscle)

CN 3 supplies what muscles?

4/6 extraocular eye muscles and levator palpebrae superioris (raises eyelids)

What is the apparent origin of CN 3 (be specific)

ventral from interpeduncular fossa (into cistern)

Oculomotor nerve carries _________ axons from _______ nucleus to innervate which 2 muscles?

preganglionic parasympathetic axons

occulomotor accessory (AKA Edinger- Westphal) nucleus

sphincter pupillae

ciliaris

Functions of:

1. Ciliaris muscle

2. Sphincter pupillae

ciliaris --> lens accommodation, focus

sphincter pupillae --> pupillary constriction

Which 2 structures of the midbrain extend up into the subthalamus of diencephalon?

parvocellular region of red nucleus

substantia nigra

What is found in the diencephalon?

Third ventricle

Thalamus

Epithalamus

Hypothalamus

Subthalamus

What are the 3 general functions of the diencephalon?

most significant relay center for sensory input to cerebrum

integrative

control of autonomic and endocrine functions

Where is the epithalamus located?

superior to tectum

What are the 2 structures found in the epithalamus?

pineal gland and posterior commissure

The pineal gland is also called the....

epiphysis cerebri

What 3 things does the pineal gland secrete?

serotonin, melatonin, norepinephrine

T/F? Pineal gland is known as "brain sand"

False! Only calcified pineal gland is called this - happens as we age

What kind of capillaries are found in pineal gland? What is the significance of this?

fenestrated vascular capillary beds - no BB barrier so hormones can go directly to bloodstream

What kind of support cells are found in the pineal gland?

glial support cells (glue-like)

T/F? Melatonin is the controller of the circadial cycle

False! It is a function of circadial cycle

controlled by suprachiasmatic nucleus

Where is the posterior commissure located?

superior to tectum

What is the primary function of posterior commissure?

pupillary light reflex fibers

How does the pupillary light reflex work?

R pupil constricts and because there is connection via posterior commissure, L pupil will ALSO constrict

What is found anterior and inferior to posterior commissure? What does it do?

subcommissural organ

may produce aldosterone, composed of ependymal cells

What is the largest of all nuclei in the CNS?

thalamus

The lateral and medial geniculate bodies are also referred to as...

metathalamus

The thalamus is made up of 2 __________ joined together by a bridge called ________

2 large ovoid masses (gray)

mass intermedia or interthalamic adhesion

The thalamus forms the bulk of what?

lateral walls of third ventricle

What is found lateral to each thalamic mass? (hint: white matter)

posterior limb of internal capsule

The thalamus is involved in ALL sensory input into cerebral hemispheres EXCEPT what?

olfaction (smell)

The thalamus and the reticular formation of brain help to do what?

focus attention of cerebral cortex (think increase/decrease sensitivity)

T/F? Pain and temperature can be interpreted at the thalamic level without going to the cerebrum

False! must go to higher brain center for complete integration

hint: you know it hurts, but you don't know where until it makes it to higher brain center

What is the largest part of the thalamus? Where is it located?

Pulvinar

located posteriorly - found only among highest of primates

What is the internal medullary lamina?

myelinated pathway for axons in thalamus (white matter) and divides subnuclei

The hypothalamus forms what?

floor of third ventricle + portions of lateral walls

What 2 structures do we find in the hypothalamus?

infundibular stalk and optic chisma

T/F? The hypophysis cerebri is found in the hypothalamus

FALSE - AKA pituitary gland is not found here

What are 4 general functions of the hypothalamus?

drives of hunger, thirst, sex

controls physical aspects of emotional expression (crying/blushing/flushing)

autonomic/visceral functions

direct/indirect endocrine control

The anterior and intermediate areas of hypothalamus are associated with sympathetic or parasympathetic?

parasympathetic (rest and digest)

The posterior area of hypothalamus is associated with sympathetic or parasympathetic?

sympathetic (fight or flight)

With direct endocrine control within hypothalamus, what happens?

neuron axons extend directly into POSTerior pituitary

With indirect endocrine control within hypothalamus, what happens?

neurohormones control release of ANTerior pituitary (carried in blood)

Is the supraoptic and paraventricular nucleus involved in direct or indirect endocrine control?

direct

Where do supraoptic and paraventricular nucleus terminate?

What do they release?

posterior pituitary

oxytocin and ADH

What tract do supraoptic and paraventricular nucleus utilize?

Where do axons travel through?

hypothalamohypophyseal AKA supra-opticohypophyseal

infundibular stalk

Which nucleus controls circadial rhythm? (sensitive to light)

Suprachiasmatic Nuclei

T/F? Suprachiasmatic nuceli exerts influence over pineal gland

True

What is the function of the anterior nucleus of hypothalamus?

parasympathetic control center

What is the function of the preoptic area?

thermo-regulator, activates when get too WARM, initiates sweating

What is the function of the dorsomedial nuclei?

parasympathetic control over GI tract, increase rate of digestion

What is the function of the ventromedial nuclei?

satiety center that becomes active when we are satisfied eating or drinking

T/F? Arcuate nuclei are involved in DIRECT endocrine control

False! indirect that act on ANTERIOR pituitary

What tract does arcuate nuclei utilize to act on anterior pituitary?

tuberoinfundibular tract

What kind of hormones are being carried in tuberoinfundibular tract?

Are they carried a short distance or long distance?

releasing factors (AKA hypothalamic hypophysiotropic hormones)

short distance in blood

What is the gray swelling formed from arcuate nuclei called? Where is it found?

tuber cinerium

between infundibular stalk and mammillary bodies

What is the function of the posterior nucleus?

thermo-regulator, activates when we get too COLD, initiates shivering

Mammillary bodies are associated with what function?

short-term memory

What is the clinical condition associated with mammillary bodies? Explain the causes/symptoms

Korsakov's Syndrome

malabsorption of vitamin B, loss of short-term memory, confabulation

(usually alcohol related)

The pars nervosa and neurohypophysis are synonyms for...

posterior pituitary

T/F? The posterior pituitary is an extension of the brain

True, develops from diencephalon - think direct

Adenophyophysis is a synonym for...

anterior pituitary

Where does the anterior pituitary/adenohypophysis develop from?

Rathke's pouch (orophyargneal membrane)

think indirectly

What is the initial source of hypophyseal portal system?

internal carotid blood vessel

What structure in hypophyseal portal system takes releasing factor from one capillary to the next?

hypophyseal portal vein

Where is the subthalamus located?

under lateral ventral aspect of thalamus

What 3 structures are found in the subthalamus?

parvocellular region of red nucleus

substantia nigra

subthalamic nuclei (AkA corpus luysi)

The corpus luysi sends and receives fibers to and from where?

Is it pyramidal or extrapyramidal?

globus palludis

extrapyramidal

Lesions of corpus luysi result in what?

ballism or hemiballism - flinging movements of shoulders and hips