Block 2 Flashcards
bony encasement
- skull and vertebrae
- provides protection of the CNS from external injury
Meninges
- 3 connective tissue layers
- provide mechanical suspension system anchored to bones to protect CNS from internal injury
- provide a space for CSF circulation
purposes of CSF
- provides buoyancy
- provides a source of nutrients and assists in waste removal
pia mater
- (delicate mother)
- thin membrane covering brain and spinal cord
- surface blood vessels travel just above it, and their capillaries penetrate the pia into the brain
arachnoid
- slightly thicker than pia matter
- is the middle layer
- does not follow surface contours, will bridge over major depressions
- since it bridges, it makes the subarachnoid space which is where the CSF will circulate
cisterns
enlargements of the subarachnoid space
subdural space
the minimal space between the dura and the arachnoid layers
dura matter
-much thicker than meningeal layers
-two parts: outer–> periosteal dura
inner–> meningeal dura
The sublayers of the dura matter are normally fused except at
sinus
sinuses
-CSF and venous blood drain into the sinuses
dural reflections
- the infolding and fusion of the meningeal layers of the dura
- this acts as a hammock-like suspension system
falx cerebri
keeps the two cerebral hemispheres frm impacting each other
what structure prevents the cortex from driving into the cerebellum or brainstem during blows to the head?
tentorium cerebelli
denticulate ligaments
attach layers of meningeal layers to each other
lateral ventricles
-backwards C shape of telencephalon
3rd ventricles
lie within the diencephalon
the cerebral aqueduct
within the mesencephalon
4th ventricle
-within the pons and medulla
choroid plexus
lies within the lateral, third, and fourth ventricles
-is where the CSF is produced
cappillaries in the choroid plexus are lined with ___ cells that are ____
-endothelial cells that are leaky
Blood pressure may force water solutes into the space between the capillary and choroid epithelium, but they wont pass into the ventricles why?
because the choroid epithelial cells are connected to each other by tight junctions
blood-cerebrospinal fluid barrier
-prevents solutes and water from entering into the ventricles
Is CSF a simple ultrafiltrant of blood ?
No. It is formed by actively transporting substances by carrier proteins in the choroid epithelium
describe the flow of CSF
-lateral–>third–> cerebral aqueduct–> fourth
How does CSF gain access to the subarachnoid space to supply the surface structures?
-the median aperture and the two lateral apertures
where is CSF collected for diagnostic purposes?
from cisterns, like the lumbar cistern
blockage of cerebral aqueducts or apertures can lead to
-hydrocephalus
Where do surface veins of the brain empty?
-the superior sagittal sinus which is along top of the falx cerebri—> transverse sinuses along the back of the tentorium cerebelli
Deep veins feed into the
-inferior sagittal sinus
where do all sinuses ultimately drain into?
internal jugular vein
what two major vessels supply the brain?
-paired internal carotid and the vertebral arteries
branches of the vertebral arteries
anterior spinal artery and the paired posterior spinal artery
basilar artery
-forms just below the pons as the vertebral arteries merge
branches of the basilar artery supplies
- the brainstem
- cerebellum
- choroid plexus of the fourth ventricle
the posterior cerebral artery
-supplies the occipital lobe, inferior temporal lobe, and parts of the diencephalon and midbrain
name the two major branches off of the internal carotid and one minor
- anterior cerebral artery
- middle cerebral artery
- minor: anterior choroidal artery
what does the anterior cerebral artery supply?
-anterior and medial cortical structures
the middle cerebral artery supplies
-most of the lateral cortical hemispheres and bulk of the basal ganglia
the minor anterior choroidal artery supplies
deeper parts of the basal ganglia, amygdala, and hippocampus and choroid plexus of lateral and 3rd
what joins the internal carotid and the vertebral artery systems at the base of the brain?
-posterior communicating arteries
Circle of Willis
provides potential redistribution of blood when one major artery is blocked… not so good with sudden blockages like in embolisms
name the 4 things the vestibular system can do
- relays signals to motorneurons that control posture, to help prevent loss of balance
- relay signals to extraocular motorneurons to aid in visual fixation during head movements
- provides for a sense of where self is in space , gives an implicit knowledge of up and down
- helps to provide for changes in changes in respiration and circulation that are necessary as we move and change posture
what composes the vestibular labrynth
3 semicircular canals and two otolith organs
what special kind of medium bathes the stereocilia
the endolymph
what does it mean that the vestibular afferents in VIII have a resting discharge
at rest, the stereocilia of the hair cells are unbent yet still releasing neurotransmitter
ampulla
swelling at the central end of each semicircular canal where the hair cells are confined
how are hair cells in the horizontal canal oriented in the ampulla?
kinocilia point to the utricle (the central end of each ampulla)
crista ampullaris
-the sensory epithelium within an ampulla
describe how the semicircular canals respond to the following head movements:
head rotation to the left
Left: Lateral- increase Superior- 0 Posterior- 0 Right: lateral- decrease Superior-0 Posterior-0
describe how the semicircular canals respond to the following head movements:
head rotation to the right
Left: Lateral-decrease superior-0 posterior-0 Right: lateral-increase superior-0 posterior- 0
describe how the semicircular canals respond to the following head movements:
Left ear down
Left:
lateral-0
superior- +
posterior- +
Right:
lateral-0
superior- -
posterior- -
describe how the semicircular canals respond to the following head movements:
right ear down
Left: lateral- 0 superior- (-) posterior-(-) Right: lateral- 0 superior- + posterior- +
describe how the semicircular canals respond to the following head movements:
Pitch forward
Left: Lateral-0 superior- (+) posterior- (-) Right: lateral-0 superior- (+) posterior- (-)
describe how the semicircular canals respond to the following head movements:
Pitch backwards
Left: Lateral-0 superior- (-) posterior- (+) Right: lateral-0 superior- (-) posterior- (+)
what information is not coded by the semicircular canals, but by the otilith organs?
- info concerning static position of head in space (location with respect to gravity)
- information regarding linear accelerations placed on the head as occurs when falling or de/accelerating in a car
name the two otilith organs
utricle and sacculus
name the two important ways the utricle and sacculus differ from the semicircular canals
1-the stereocilia of the otilith organs are in the otilithic membrane which has a higher specific gravity than the surrounding fluid- its the membrane that shifts in position when tilted
2- the hair cells do not face in one direction! they are in many different orientations
hair cells in the utricular macula are affected by
-linear acceleration in the horizontal plane
tilting of head with respect to gravity
hair cells in saccular macula are affected by
- linear acceleration in the vertical plane
- tilting head with respect to gravity
the striola
the imaginary line where direction of hair cells reverse abruptly
most vestibular afferents project to one of 4 brainstem nuclei
the 4 brainstem nuclei are:
- superior
- inferior
- lateral (Deiter’s nucleus)
- medial
some neurons in the vestibular nuclei lack neck inputs and fire during head and whole body type movements. Give an example
neurons that project to extraocular motorneurons
flocculus
-portion of the cerebellum that along with the medial cerebellum regulates activity of the vestibular nuclei
which vestibular nuclei have projections to the cranial nerve nuclei III, IV, and VI and why
- medial and superior nuclei
- these connections are responsible for powerful vestibulo-ocular reflexes
medial vestibulo-spinal tract (MVST)
- mainly influences neck motorneurons
- important for maintaining stable head position in space
lateral vestibulo-spinal tract
-involved in maintaining balance through its effects on limb motorneurons
direction of sound waves
large auricle (external ear)–> external auditory meatus–> tympanic membrane–> malleus, incus, and stapes
Eustachian tube
- connects the middle ear to the throat
- works to keep the pressure on the two sides of the ear drum equal
name the 3 fluid-filled chambers of the cochlea
- scala vestibuli
- scala tympani
- scala media
helicotrema
-where the two perilymph-filled chambers join at the apex of the cochlea
when sound causes the tympanic membrane and middle ear bones to vibrate, the force is transmitted to through the ____ into the ___. The necessary pressure release to allow fluid to vibrate is allowed by the ____
- oval window
- scala vestibuli
- round window
what and where are the sensory epithelia for the auditory system?
- organ of corti
- located in cochlear duct
Hair cells of organ of Corti are innervated by afferents of the ____ nerve. The cell bodies of these afferents are located in the ________, which is found in the bone just outside the cochlea
- cochlear nerve
- spiral ganglion
the stereocilia of auditory hair cells are imbedded in
tectorial membrane
the hair cells are attached to
the basilar membrane
____ send their axons through the VIII cranial nerve to innervate ___ hair cells
- neurons in the superior olivary mucleus
- outter
function of auditory outter hair cells
-to adjust sensitivity in the peripheral auditory system
If people lose hair cells, but retain innervation of the cochlea by the VIII nerve then ___ can be used ti restore hearing
-cochlear implants
parts of the cochlear implant
- microphone: detects sound
- speech processor: to determine which sound frequencies are present. Has a microprocessor to filter out noise
- transmitter and receiver/stimulator: that converts signals from sound processor to electrical pulses
- 22 electrodes to go along the cochlea
name the two brainstem nuclei that the auditory afferents can terminate?
-dorsal cochlear nuclei
ventral column nuclei
projects directly to the inferior colliculus
dorsal cochlear nucleus
the dorsal cochlear nucleus projects directly to the inferior colliculus which projects to the ____ which projects to Brodmann’s areas ____
- medial geniculate
- 41 and 42
name the difference between the brain capillary endothelial cells and the choroid capillary endothelial clls
- the brain capillary endothelial cells have tight junction
- the choroid capillary endothelial cells do not have tight junctions ** its the choroid epithelial cells that have the tight junctions
Common features of ascending dorsal column and spinothalamic tract
- consist of 3 neurons in series
- mostly crossed
- somatotopically organized
- maintain modality specificity
