Exam 2 Flashcards
What are the two major blood vessels that supply blood to the brain
Vertebral Arteries and Internal Carotid Arteries
What are the vertebral arteries
Part of the posterior circulation system
where do the vertebral arteries supply blood to
upper spinal cord
brainstem
cerebellum
posterior part of the forebrain
What are the internal carotid arteries
part of the anterior circulation system
where does the internal carotid arteries
mainly supply blood to the anterior part of the forebrain
What are the branches of the vertebral arteries
anterior spinal artery
posterior spinal arteries
what are the basilar artery
formed where the vertebral arteries merge below the pons
runs along the ventral side of the pons
what are the branches of the basilar artery
pontine arteries
superior cerebellar arteries
anterior inferior cerebellar arteries
where does the posterior cerebral arteries supply blood to
midbrain
diencephalon
inferior temporal lobe
posterior parietal lobe
occipital lobe
what are the branches of the internal carotid arteries
anterior cerebral arteries
middle cerebral arteries
where does the anterior cerebral arteries supply blood to
anterior and medial cortical structures
where does the middle cerebral arteries supply blood do
most of the lateral side of the cortical hemispheres
portions of the basal ganglia
what is the anterior communicating artery
connects the left and right anterior cerebral arteries
what is the posterior communicating arteries
place where the internal carotid and vertebral artery systems join on the ventral surface of the brain
what is the circle of willis
the communicating arteries complete a circle of blood vessels which allows for redistribution of blood when a major artery in this circle is blood
what is the dura mater
outermost layer
tough, thickest layer
does not closely follow the contours of the sulci
what are the two layers of the dura mater
periosteal layer
meningeal layer
what is the periosteal layer
layer of dura mater closest to the bone
what is the meningeal layer
layer of dura mater closest to the brain
what is the arachnoid mater
middle layer
thinner than the dura
closely apposed to the dura
does not closely follow the contours of the tissue below it
what is the subdural space
between the dura and arachnoid layer
can fill with fluid in response to injury
what is the pia mater
innermost layer of the meninges
thin membrane covering the surface of the brain
closely follows the shape of the tissue below it
small capillary branches of surface blood vessels penetrate the pia and go into the brain
what is the subarachnoid space
physical space between the arachnoid and the pia
cerebrospinal fluid circulates through this space
surface capillaries run through it just above the pia
what is arachnoid trabeculae
thin threads of connective tissue that connect subarachnoid layer to the pia
what is a dural reflection
meningeal layer of the dura fold inward and fuse to form a space
suspension system that protects the brain
what are the two dural reflections
flax cerebri
tentorium cerebelli
what is the falx cerebri
meningeal dura that lies within the longitudinal fissure and keeps the two cerebral hemispheres from colliding
what is the tentorium cerebelli
covers the cerebellum and brainstem to keep the cortex from colliding with the cerebellum and/or brainstem
what are the lateral ventricles
located in the telencephalon
three ‘horns”: frontal, temporal, occipital
what is the third ventricle
in the diencephalon
lies along the midline between the left and right thalami
what is the interventricular foramen
passage that connects the lateral ventricles to the third ventricle
what is the fourth ventricle
located in the pons and medulla between the cerebellum and the dorsal side of the brainstem
what is the cerebral aquaduct
located in the midbrain
passage that connects the third and fourth ventricles
what is the choroid plexus
tissue that makes cerebrospinal fluid in all four ventricles
where is CSF found in
all four ventricles
passages that connect ventricles
central canal
around brain and spinal cord in the subarachnoid space
what direction does cerebrospinal fluid flow in through the ventricles
caudally
how is the choroid plexus
formed by invaginations of the pia mater and capillaries into the ventricular space
what is a sinuses
formed at a separation between the periosteal and meningeal layers of the dura
what are the arachnoid granulations
Place through which CSF drains from subarachnoid space into the sinuses
what is the superior sagittal sinus
runs along the top of the falx cerebri
surface veins feed into this sinus
what is the inferior sagittal sinus
runs along the base of the cerebri
deep veins feed into this sinus
drains to the straight sinus
what is the confluence of sinuses
fluid from the superior and straight sinus goes into this place
what is the transverse sinuses
run laterally from the confluence of sinuses where the tentorium cerebelli is attached to the occipital
where does in sigmoid sinus drain into
the internal jugular vein
what is the somatosensory system
processes information related to the body surface, muscles, and tendons
What are cutaneous receptors
transduce information about something touching the skin
located on the peripheral axons of pseudo-unipolar cells which are primary afferent neurons
how do cutaneous receptors differ
type of nerve ending
sensory threshold
adaption rate
what are the types of nerve endings
free nerve endings
encapsulated endings (corpuscles)
what are free nerve endings
tip of axon is in the cutaneous tissue without anything surrounding
what are encapsulated nerve endings
have a cap of connective tissue surrounding the tip of the sensory axon
what is a low threshold receptor
respond to minimal stimuli
ex. touch of a feather
what is a high threshold receptor
respond to only stronger stimulation
ex. tackle
what does it mean for a nerve to be slowly adapting
respond throughout the entire stimulus though the action potential rate with gradually decrease throughout
what does it mean for a nerve to be rapidly adapting
respond only when a stimulus begins and ends but not while the stimulus is present and not changing
what are cutaneous thermoreceptors
communicate skin temperature
free nerve endings, low threshold, rapidly adapting
do all thermoreceptors respond to the same temperature
no, some thermoreceptors respond to hot and some cold; different types of thermoreceptors have different temperature ranges
what are cutaneous nociceptors
communicate possible/impending tissue damage
free nerve ending
slowly adapting
what are the types of nociceptors
high threshold mechanoreceptors
thermal nociceptors
chemosensitive nociceptors
what are high threshold mechanoreceptors
respond only to intense mechanical stimulation that is likely to cause tissue damage
what is a thermal nociceptor
respond to extremes of heat and cold temperatures
what is a chemosensitive nociceptor
mainly respond to chemicals released in response to tissue damage and inflammation but can also respond to external chemicals such as capsaicin
what is nociceptor sensitization
occurs when nociceptors react to lower amounts of pain than they normally would
what can nociceptor sensitization lead to
allodynia
hyperalgesia
what is allodynia
normally NON-painful stimuli are now painful
what is hyperalgesia
PAINFUL stimuli are now cause more pain than normal
what are cutaneous mechanoreceptors
distortions of the skin, muscles, or tendons physically pull ion channels open
what are tactile cutaneous mechanoreceptors
related to sense of touch
all tactile receptors are cutaneous mechanoreceptors
what is a peritrichial receptor
receptors in hairy skin
nerve endings around the roots of skin hairs
free nerve endings, low threshold, rapidly adapting
what are encapsulated tactile receptors
meissner’s corpuscle
merkel’s disc
pacinian corpuscle
ruffini corpuscle
what does low spatial resolution mean
low density (few axons)
large receptive fields
high overlap
ex. back
what does high spatial resolution mean
high density (many axons)
small receptive fields
low overlap
ex. finger tips
what are meissner’s corpuscles
nerve endings inside capsules of connective tissue
encapsulated, low threshold, rapidly adapting, small receptive fields
sense velocity of objects moving on skin
what are merkel’s discs
nerve ending in close contact with a capsule of connective tissue
encapsulated, low threshold, slowly adapting, small receptive fields
senses constant contact with skin and intensity of touch
what are pacinian corpuscles
large sensory axons embedded in fluid filled layers of connective tissue cells deep in the skin
encapsulated, low threshold, very rapidly adapting, large receptive fields
respond mainly to vibration
what are ruffini corpuscles
sensory axons runs through bundles of collagen fibers deep in the skin
the collagen fibers deform the sensory axon when the skin is stretched
encapsulated, low threshold, slowly adapting, large receptive fields
sense stretching of skin
what are proprioceptors
respond to movement of the tissue in which they are embedded
important components of reflex circuitry
helps maintain balance, control limb movement, and maintain grip strength
what are the types of proprioceptors
muscle spindles
golgi tendon organs
what are muscle spindles
respond to muscle stretch
what are golgi tendon organs
respond to muscle contraction
found at junctions between tendons and muscles
Dorsal column pathway
tactile and proprioceptive information from body to CNS
spinothalamic pathway (anterolateral pathway)
pain, temperature, and crude touch from body to CNS
spinoreticular pathway
diffuse pain from body to wisespread areas of the thalamus and cortex
trigeminal afferent pathway
tactile and pain information from face to CNS
What are the common characteristics across all the ascending pathways
three neurons in series
pathway crosses midline
somatotopically organized
each pathway maintain modality specificity
what does the conduction velocity of neurons depend on
axon diameter and degree of myelination
What is the conduction velocity of fibers from fastest to slowest
A alpha, A beta, A delta, C
what is layers I-VI of Rexed’s laminae
dorsal horn
sensory neurons
interneurons
what is layer VII of Rexed’s laminae
lateral horn and ventral horn
preganglionic motor neurons of the ANS
what is layer VIII and IX of Rexed’s laminae
ventral horn
somatic motor neurons
where do the first order neurons of the dorsal column enter
enter the gray matter on the medial side
describe the main branches of the first order neurons of the dorsal column
do not synapse at the level of entry
ascend via the dorsal column
terminate in the dorsal column nuclei
describe the collateral branches of the first order neurons of the dorsal column
terminate in layers III-VI of the dorsal horn and in layers VII and IX of the ventral horn
What areas are in the gracile fasciculus in the dorsal column
sacral (closest to the midline) and lumbar
what areas are in the cuneate fasciculus in the dorsal horn
thoracic (medial) cervical (lateral)
where do the first order neurons synapse onto the second order neurons in the dorsal column
gracile and cuneate brainstem nuclei in the lower medulla
where is the decussation of the dorsal column
second order neurons cross the midline in the medulla
where do the second order neurons project to the third order neurons in the dorsal column
project via the medial lemniscus to 3rd order neurons in the thalamus
where are the 3rd order neurons located in the dorsal horn
ventroposterior lateral thalamus
where do the 3rd order neurons project to in the dorsal column
project ipsilaterally in the internal capsule to the primary somatosensory cortex and to the secondary somatosensory cortex
describe the A delta fibers of the spinothalamic pathway
terminate in layers I and V
synapse onto second order spinothalamic neurons
describe the C fibers of the spinothalamic pathway
terminate in layer II where there are no second order spinothalamic cell bodies
where do the 1st order neurons synapse onto the 2nd order neurons in the spinothalamic pathway
in layers I-V in the dorsal horn
where do the 2nd order neurons project to the 3rd order neurons in the spinothalamic pathway
project across the midline and travel via the spinothalamic tract to 3rd order neurons in VPL thalamus
what is the somatotopic organization of the spinothalamic tract
cervical (closest to midline), thoracic, lumbar, sacral (fartherest)
where is the decussation of the spinothalamic pathway
spinal cord
describe pain sensation from A delta fibers
faster conduction than C fibers
arrives in SI cortex earlier than C
sharp intense pain
easy to localize
describe pain sensation from C fibers
slower conduction
perceived as more diffuse pain
harder to localize
describe the spinoreticular pathway
spinothalamic pathway axons ascend and synapse on 3rd order neurons in reticular formation in the brainstem; these RF neurons project to the intralaminar nucleus of the thalamus
what is the spinoreticular pathway important for
mediating a global awareness of pain
describe the trigeminal afferent pathway
1st: CN V to trigeminal brainstem nuclei
2nd: trigeminal nuclei to contralateral VPM thalamus
3rd: VPM to SI cortex
what are soundwaves
rhythmic compressions of air molecules
what dictates the pitch of sound
the frequency of the compressions of air
what is the frequency range of human hearing
20 - 20,000 Hz
What are the parts of the outer ear
auricle, external auditory meatus, tympanic membrane
what are the parts of the middle ear
auditory ossicles and oval window
what is the inner ear
cochlea
what is the function of the middle ear
amplifies vibrations of the tympanic membrane and transfers them to the oval window
what is the function of the malleus
receives vibrations from the tympanic membrane
what is the function of the incus
forms a lever with the malleus to amplify vibrations of the tympanic membrane
what is the function of the stapes
base touches the oval window
what are the auditory ossicles
malleus, incus, stapes
what is the eustachian tube
connects middle ear and throat
what can a blockage of the eustachian tube cause
otitis media
what are scala
three fluid filled chambers that run along the length of the cochlea
what is the helicotrema
two scala joined at the apex of the cochlea
describe the scala vestibuli
filled with perilymph
one end contains the oval window
describe the scala media
filled with endolymph
contains the organ of corti and the tectorial membrane
describe the scala tympani
filled with perilymph
one end contains round window
continuous with the scala vestibuli at the heliocotrema
describe the vestibular membrane
separates scala vestibuli from scala media
very thin so vibrations in scala vestibuli vibrate the fluid in the scala media as well
describe the basilar membrane
cell bodies of hair cells are attached to this membrane
vibrates in response to movement in the fluid within the scala vestibuli
describe the tectorial membrane
in the scala media
stereocilia of hair cells touch this membrane
more rigid than the basiliar membrane
describe the tectorial membrane
in the scala media
stereocilia of hair cells touch this membrane
more rigid than the basiliar membrane
what is the function of hair cells
transduce mechanical pressure into a neuronal signal
what are the two types of hair cells
inner and outer hair cells
describe inner hair cells
sensory cells
single row along basiliar membrane
stereocilia touch the tectorial membrane
describe outer hair cells
3 rows along external side of basiliar membrane
receive efferent signals via CNVIII that cause the outer hair cells to shorten
What does the shorten of outer hair cells do
the change in shape alters the spacing between the tectorial membrane and the hair cells which adjusts the sensitivity of the inner hair cells to fluid vibrations
what is the function of stereocilia
fine cilia on hair cells that detect fluid movement in cochlea and semicircular canals
what are tip links
connects adjacent stereocilia; connected to cation channels in the membrane of stereocilia
what happens whens stereocilia are bent
tip links pull the cation channels open which changes the membrane voltage of the hair cell
what happens when stereocilia move toward the tallest stereocilia
channels open and K+ goes into the hair cell
hair cell depolarizes which releases more neurotransmitter than at rest
what happens when stereocillia move away from the tallest stereocilia
more channels close than at rest
hair cell hyperpolarizes which releases less neurotransmitter than at rest
describe a stereocilia at rest
some cation channels are open so a baseline level of glutamate is released when the stereocilia are not deflected
how are hair cells activated
movements of the basilar membrane pushes the stereocilia against the tectorial membrane which causes them to bend
what is the tonotopy of the base of the basiliar membrane
stiff and narrow
vibrates best at high frequencies
what is the tonotopy of the apex of the basiliar membrane
wider and more flexible
vibrates best at low frequencies
where do the auditory afferents travel to via CNVIII
dorsal and ventral cochlear nuclei
where do the neurons in the dorsal and ventral cochlear nuclei project to
inferior colliculus
where does the inferior colliculus project to
medial lateral geniculate nucleus of the thalamus
where does the MLG project to
primary auditory cortex
describe the primary auditory cortex (A1)
located in the superior temporal gyrus inside the lateral fissure
tonotopic map of the cochlea
describe the secondary auditory cortex
located in the superior temporal gyrus lateral to A1
