UNIT 2: Brain Stems and Supporting Systems Flashcards
what does the diencephalon include
thalamus, epithalamus, subthalamus, hypothalamus, plus mammillary bodies
describe the thalamus
- contains multiple nuclei that are part of motor, sensory, and associative pathways
- receives ALL sensory feedback (except olfactory), and relays to the cortex (i.e. thalamus decides whether the info is worthwhile - like a gate keeper/amplifier … decides what is worthwhile and also whether the the dial needs to be turned up or down)
- motor contribution –> transmits info from cerebellum and BG to primary motor cortex (involved in motor planing and initiation of speech)
- axons that connect thalamus and cerebral cortex pass thru the internal capsule
what is the thalamus made up of
many nuclei - each do something specific and talk to specific systems (ex. vision)
Connection bw limbic sys and thalamus
limbic sys will tell the thalamus whether it needs to focus on something in relation to memories associated w a sensory or motor signal
hypothalamus functions
- controls many body activities - major regulator of homeostasis
- sensory input related to somatic, visceral, and special (taste, smell, vision) senses arrive here
- important connections w pituitary gland; produces a variety of hormones
- controls and integrate activities of the ANS - major regulator of visceral activities (contraction of smooth and cardiac muscle, gland secretion)
- regulates emotion + behaviour, eating and drinking, body temp, circadian rhythms, and consciousness
describe the composition of the cerebellum
- external portion is gray matter (cortex)
- internal core is comprised of white matter (tracts) and deep nuclei (subcortical nuclei)
- communicates w pons via cerebellar peduncles (afferent and efferent tracts)
- each hemisphere has 3 lobes: anterior, posterior, flocculonodular
- vermis = central cortex that connects the 2 cerebellar hemispheres (analogous to corpus callosum)
- more neurons than cortex!
function of cerebellum
- primary structure responsible for coordination of fine movement: integrates somatic info related to vestibular function (balance), muscle and joint sense, and perception of the body in space
- works w cerebrum to fine tune the motor plan for optimal execution
- i.e. helps us compare what I thought i was gonna do to what I actually did (motor learning ) - whereas the BG helps us select a motor plan
what are the 3 functional divisions of the cerebellum?
- vestibulocerebellum (flocculonodular lobe)
- spinocerebellum (anterior lobe and posterior lobe)
- cerebrocerebellum (posterior lobe)
vestibulocerebellum (flocculonodular lobe) of cerebellum
integrates vestibular info about body position w motor plan
spinocerebellum (anterior lobe and posterior lobe) of cerebellum
integrates proprioceptive info (body sense of position and movement in space) and controls gait and stance
cerebrocerebellum (posterior lobe) of cerebellum
execution of voluntary motor plans initiated by cerebral cortex - feedback to smooth movements, correct errors, coordinate complex sequences of muscle contraction
3 anatomic divisions of the brainstem
mesencephalon = midbrain
metencephalon = pons (minus cerebellum)
myelencephalon = medulla oblongata
all pathways to and from cerebrum pass through…
the brainstem (afferent and efferent)
the brainstem contains what types of nuclei
- many autonomic regulatory nuclei
- nuclei associated w cranial nerves II thru XII
what does the midbrain contain
aqueduct, fibre tracts, nuclei
the midbrain’s aqueduct connects to…
the 3rd ventricle above w the 4th ventricle below
the fibre tracts of the midbrain are also called “___” and contain “___” and “____”
- cerebral peduncles (pair of vertical fibre tracts)
- corticopsinal, corticobular, and corticopontine motor neuros (refer to where they go)
- sensory neurons from medualla to thalamus
what are the 4 nuclei of the midbrain
superior colliculi, inferior colliculi, substantia nigra, red nuclei
superior colliculi
- nuclei in the midbrain
- central visual pathway nuclei
inferior colliculi
- nuclei in the midbrain
- central auditory pathway nuclei
substantia nigra
- nuclei in the midbrain
- subconscious muscle activity (functionally part of the basal ganglia)
red nuclei
- nuclei in the midbrain
- minor role in motor function (i.e. limb flection) in association w cerebellum
which cranial nerves are associated w the midbrain
oculimotor nerve (III) (motor), trochlear nerve (IV) (motor), mesencephalic nerve of trigeminal tract (V) (sensory)
what and where is the pons
- enlarged section of the brainstem bw the midbrain (above) and medulla (below)
- bridge to the cerebellum (anterior to it)
the pons contains
- fibre tracts
- CN nuclei
on the ventral side of the pons you can see what type of fibre tracts?
- cerebral peduncles –> horizontal fibre tracts allowing communication bw cerebrum, brainstem, and cerebellum (maximizes efficiency of voluntary motor control)
- basilar sulcus –> cradles the basilar artery (a depression)
on the dorsal side of the pons there are fibre tracts similar to the…
medulla - carry both sensory and motor info - corticobular and corticospinal tracts
which cranial nuclei are in the pons
- trigeminal motor nuclei
- principal sensory nuclei of the trigeminal tract
-abducent nuclei (motor) - facial motor nuclei
- superior salivatory nuclei (motor)
the pons also has the emergence of which critical cranial nerves
- CN V - trigeminal
- CN VI - abducens
- CN VII - facial
- CN VIII - Vestibulocochlear
medulla’s location/function/contents
- most caudal portion of the brainstem; in bw the pons (above) and spinal cord (below)
- 2.5 cm in length, 1 cm in diameter
- extremely vital for life functions (ex. respiratory drive, cardiac function)
- contains fibre tracts and CN nuclei
What are the pyramids of the medulla
a structure where all motor fibres from the cerebrum to spinal cord travel through
pyramidal decussation of the medulla
location where corticospinal tracts decussate (where fibers cross) (contralateral innervation)
list the CN nuclei of the medulla
-vestibular nuclei (sensory)
-cochlear nuclei (sensory)
- N of the spinal tract (sensory)
- N tractus solitarius (sensory)
- N ambiguus (motor)
- Dorsal motor n.
- spinal n. of the accessory nerve (motor)
what critical cranial nerves emerge from the medulla
- CN VIII (vestibulocohlear)
- CN IX (gloffopharyngeal)
- CN X (vagus)
- CN XI (accessory)
- CN XII (hypoglossal)
3 supporting systems of NS
meninges, ventricular system, vascular system
meninges function
protection of the brain (and spinal cord) and its vasculature
ventricular system functions
nutrient supply and protection
vascular systems functions for NS
oxygen and glucose supply
3 types of meninges
dura mater, arachnoid mater, pia mater
Dura matter is
- the most superficial meninge
- 2 layers thick (bilaminar) w epidural space bw
- limits excessive movement of brain
3 extensions of the dura mater
falx cerebri, falx cerebelli, tentorlum cerebelli
the arachnoid mater is
- the meninge deep to the dura mater
- thinner, more elastic
- follows brain convultions more closely
- has blood vessels and CSF
the space bw the dura mater and arachnoid mater is
subdural space
pia mater is
- the deepest meninge
- very thin
-clings to surfaces, follows fissures and sulci - surrounds blood vessels that pierce the cortex
space bw the arachnoid mater and pia mater
subarachnoid space (CSF and cerebral arteries/veins)
3 components of the ventricular system
- lateral ventricle
- 3rd ventricle
- 4th ventricle
lateral ventricles
- bilateral
- deep in both hemispheres
- where most CSF is produced (choroid plexi)
3rd ventricle
slit like cleft bw the R and L thalamus
4th ventricle
bw cerebellum and brainstem
explain flow of CSF thru ventricles
mostly produced in lateral ventricle, then flows to third vent thru the interventricular foramen, then thru cerebral aqueduct to 4th ventricle, and then eventually into venus draining system
ventricular system communicates via
- inter-ventricular foramen
- cerebral aqueduct
cerebrospinal fluid
- cushions the CNS and delivers nutrients, removes waste
- replenished every 7 hours
- absorbed by venous system
if the brain swells what part of the ventricular system is vulnerable
cerebral aqueduct
where is CSF produced
choroid plexus of each ventricle, particularly in the lateral ventricles
describe the vascular system of the NS (why is it special in terms of demand)
- nervous tissue has the highest metabolic rate of any human tissue… cannot store nutrients and therefore needs a constant supply of oxygen
10 sec oxygen disruption leads to
loss of consciousness
3-4 min oxygen disruption leads to
brain damage
how many pathways can blood get to the brain
2
describe the path of blood flow from the aorta through the subclavian arteries to the brain
- blood from aorta enters subclavian arteries (L + R)
- To verterbral arteries (R + L) which ascend thru transverse formina of 6 C vertebrae
- enter cranial vault thru foramen magnum
- L and R join (anastamose) to form the basilar artery
describe the path of blood flow from the aorta through the common carotid artery to the brain
- blood from aorta goes thru the common carotid artery (R + L)
- Goes into internal carotid artery (R and L)
- enters temporal bone thru carotid canal (L and R)
- exits tempora bone thru foramen lacerum
- Joins the basilar artery at the circle of willis
interal carotides course in the
anterior lateral neck
external carotids supply…
structures of the head outside the skull
the circle of willis is formed by
- basilar artery
- internal carotid arteries
- middle cerebral arteries
- anterior cerebral arteries
- posterior cerebral arteries
- anterior communicating artery
- posterior communicating arteries
middle cerebral arteries, anterior cerebral arteries, and posterior cerebral arteries take blood from circle of willis and move it to…
the brain
damage to which cerebral artery would produce the worst stroke symptoms on speech/swallowing
middle cerebral artery, bc it feeds this area of the brain
middle cerebral artery is the most direct continuation of the _____ important for ____and supplys ____
- internal carotid artery
- speech, swallowing, hearing, language
- lateral cortex (including operculum and insula), internal capsule, basal ganglia, and thalamus
the anterior cerebral artery supplies
medical and superior surfaces of frontal and parietal lobes
posterior cerebral artery supplies
occipital lobe and the inferior and medial parts of the temporal lobe
Branches of the vertebral/basilar system supply 3 things
cerebellum, brainstem, spinal cord
the venus return system does what
where blood drains to so that it can be directed back to the heart
