Flashcards in LO CNS Deck (26)
Describe the anatomy of the vestibular apparatus and cochlea including the location and composition of fluids within these structures.
Info enters CNS from vestibular apparatus via VIII cranial nerve for posture and movement of eyes relative to external environment
cochlea: detects sound
Both contained in the temporal bone of the skull. chambers and canals (bony labyrinth)
- labyrinth lined with membrane, between this and the body is the perilympth 150mm na+
- inside labyrinth there is the endolymph, high k+ 150mM, positive.
- 3 semicircular canals for rotation
- 2 chambers for acceleration
Detail how hairs cells and stereocilia transduce mechanical movements into electrical signals.
Hair cells are transducers on an apical pole. stereocilia move towards the kinocilium and mechanically open the base which have vesicles containing glutamate. K+ comes in during bending and leads opening of ca 2+ channes at base which leads to glutamate release. connected by tight junctions. only apical tips and cilia are exposed to high K+ endolymph usually. if bent in the other direction opposite happens. perpendicular nothing happens.
Describe the organisation of semicircular canals within the head with particular attention to the orientation of hair cells.
arranged in 3 pairs
horizonal anterior and posterior. each canal opens into the utricle
each has an ampulla with crista where hairs are located.
hairs in a genatinous structure (CUPULA)
Understand and describe how rotation of the head is sensed and converted to an electrical signal.
- all hairs in same direction!! only get firing if the fluid moves in one way.
allows you to detect all rotations
ex: rotate to the right, increase firing on right because endolymph lagged behind and pushing cupulae to the left. decrease firing on the left. If you get a mismatch: sickness. if you keep rotating the endolymph catches up.
maintain the position of the eyes during head movement, cr.nerves 3, 6 and 8: vestibulo-ocular reflex: maintain fixed gaze with movement.
Describe in detail the organisation and function of the utricle and saccule. Compare and contrast the types of movements sensed by the utricle and saccule with those of the semicircular canals
utricle and sacule both contain a macula which is the same as the ridge where the hair cells are
-project to otolithic membrane which has calcium carbone crystals called the otoconia, 5x as dense. respond to gravity and linear acceleration. (same lagging mechanism)
utricle: macula is on the floor (horizontal) front back left right, maintained tilt
saccule: macula is on the wall (verticle)
hair cells not in the same direction so they can do anything. some hair cells will always be depolarized.
up down left right maintained tilt.
Describe how information from the vestibular system is used to adjust posture and body position.
cause reflex adjustments. cr8 leads to alpha motor neurons where body motion (unexpected tilt) will put you back in a regular position.
Input from VA goes into brainstem on vestibular nuclea at pontomedullary junction
Superior VN: eyes
Medial VN: utricle and saccule: neck and trunk via medial vestibulospinal tract
Lateral VN: from uticle and saccule: limbs via lateral vestibulospinal tract
Inferior VN: all components to cerebellum
Describe the anatomy and organization of the outer and inner ear including the location and composition of fluids within these structures
pinna and auditory canal
- collects sound (oscillations in air pressure)
- dircects it to tympanic membran e
middle ear: ossicles (malleus, incus and stapes with amplify sound 20x)
oval window: into inner ear and fluid filled cochlea
cochlea: 3 fluid filled cavities: base to apex
- scala vestibuli and scala tympani
- scala media
base of hair cells attached to basilar membrane.
cilia of hair cells project to tectorial membrane
Describe the transduction process that converts sound into an electrical signal including detail on how different wavelengths of sound are detected.
Vibrates the tympanic membrane, moves the bones, goes to oval window. this plunges the fluid making vibrations. this vibrates basilar membrane at different places (its a continuum of frequency). the basilar membrane shakes at its frequency and moves hair cells which are deflected by the tectorial membrane and transduce! release glutamate onto cranial nerve 8.
more stiff at the base, higher frequencies at the base.
this info goes to cochlear nuclei in brainstem, to medial geniculate nucleus of the thalamus, progect to autitory cortex and temporal lobe, input from both ears. if one is damaged internally you can still get input from both ears.
Identify the 3 primary components of consciousness and the broad anatomical areas responsible for them:
1.brainstem: consiousness, level of consiousness
- reticular formation, ascending and descending neurons.
2.thalamus: response to stimulus, state of consiousness
- relay station, intralaminar and TRN nucleus on the outside, a mesh of neurons. 40hz firing with cortex to maintain consiousness.
3. cerebral cortex: content of consiousness.
-develops the plan, association areas
all required and have reciprocal connectoins
Identify the 5 neurotransmitters within the ARAS and their state their contributions to consciousness:
1. noepinephrine: focus on a task, suppress less important info. if damaged, less arousal.
2. dopamine: focus on accomplishing something and waking, promotes motivation and exploratory behaviors, if damaged, youre not motivated.
3. serotonin: quiet wakeful state, modulator, lack of gives you insomnia
controls anxiety and aggression
4. histamine: midbrain, wakefulness, antihistamines are drowsy
5. ACh: increases thalamocortical activation and arousal (talking between the two areas)
all neuromodulators of conciousness
Describe the thalamic nuclei involved in the generation of consciousness (intralaminar and thalamic reticular nuclei).
- mesh of neurons, dense reciprocal connections with other areas
- GABA ergic neurons,
Identify the two cortical areas primarily involved in mediating the content of consciousness.
PFC and parietal cortex
PFC: association area, phineas gage etc. identifies what youre looking at
Describe how neuronal the communication between these three anatomical areas required for consciousness to occur (reciprocal connections communicating at a frequency of AP firing of 40Hz).
all have reciprocal connections, need all of them to work to perform higher functions
need coalitions of neurons.
Understand the development of the CNS
The NS is divided into CNS and PNS
CNS develops from a hollow tube (enlarged at one end -rostral which becomes the brain) non enlarged as caudal (stays as spinal chord)
- rostral becomes forebrain (telencephalon/diencephalon, midbrain (mesencephalon) hindbrain (metencephalon-pons, myelencephalon-medulla)
started out as a flat sheet that "zips up" into a hollow fluid-filled core, 28 day development
Identify the ventricles containing CSF and explain the origin, function and path of flow of CSF within ventricles
right and left lateral ventricles: in cerebral hemispheres
middle 3rd ventricle: in diencephalon
4th ventricle: small in pons/cerebellum. connected via cerebral aqueduct.
all flow to each other. filled with CSF
- which is made in choroid plexus that pulls it out of plasma
- it goes though apertures or holes, and fills the space surrounding ENTIRE CNS 90% in the subarachnoid space
its produced and filtered continuously (reabsorbed back into dura sinus by arachnoid projections) and if there is a blockage it can lead to hydrocephalus (pressure fluid buildup) this isn't as bad as a baby because the plates on your brain just let it out in a bulbus bunch
Function: buoyant effect, excretion of waste-especially during sleep when CSF production increases, transport of hormones.
Detail the names and functions of the membranes covering CNS tissue.
pia mater: small thin sran wrap
arachnoid membrane: loose fit, creates subarachnoid space where fluid is. CSF reabsorbed back into veins at this site (arachnoid granulations)
dura mater: thick tough
Describe pathways and connectivity of neurons carrying touch and proprioceptive info from peripherty into cns
Touch & Proprioception are in group I and II
In the cord, 1st order ascend up without crossing or synapsing in the DORSAL COLUMNS
in caudate medulla, they synapse with 2nd order neuron in the DORSAL COLUMN NUCELI and then they cross and go up to ventroposteriolateral nucleus (VPL) to cortex.
Describe pathways of neurons carrying pain and temp from peripher into the CNS
Pain & Temp are in group III and IV
1st order neurons synapse in dorsal horn with 2nd neuron, 2nd order crosses at the same level and goes up SPINOTHALAMIC TRACT on the OPPOSITE SIDE.
up through VPL and to cortex.
Describe in detail pathway and connectivity of neurons carrying motor output from the CNS to the periphery
- voluntary movement (one neuron from cortex to the spinal chord (upper motor neuron) to lower motor neuron (alpha or gamma) which terminates on muscle.
-cell bodies in precentral gyrus (primary motor cortex) which is anterior to sensory cortex. motor homunculus. the more neurons devoted, the more fine control. Larger ones have more power but lose dexterity.
THE CORTICOSPINAL TRACT
-through the internal capsure
-through cerebral peduncle on ventral midbrain
- through pons (little clumps forming pyramids)
-through medulla in ventral pyramids
-cross to other side (in medulla: "decussation of pyramids") to the lateral column (lateral corticospinal tract)
- leave at the spinal chord, enter ventral horn of grey matter, and synapse with motor neurons.
85% of fibres cross, 15% are used by both sides (like sitting up)
describe function of the corticobulbar, reticulospinal and vestibulospinal pathways
bulbar: face musles, terminates on cravial nerve in the brainstem and crosses there
reticulospinal: reticular formation, whole brainstem, projects BILATERALLY descending fibres influence gamma motor neurons
influence muscle spindle and tone!!
vestibulospinal: cr8 medial goes to neck nad trunt. lateral goes to limbs.
excite extensor muscles
define alpha gamma coactivation and state its role in the function of spinal reflexes
ensures sensitivity of the spindle is maintained regardless of length of extrafusal fibres, makes sure it never goes slack:)
describe oranization, neuronal connectivity and function of basal ganglia including specific neurotransmitters and location of exitatory and inhibitory synapses
When you see this card: draw it out. no exceptions.
- globus pallidus internal/external
- substantia nigra
- subthalamic nucleus
-copy of command from cortex
output of BG from GPI is inhibitory (GABA) to thalamus
thalamus to cortex is excitatory (glutamate)
1. Direct pathway: single inhibitory neuron GO pathway
2. Indirect pathway, excitatory neuron in the ST. STOP pathway.
Output cell is under two influences!
When thalamus is DISINHIBITED then it increases movement
Dopamingeric progection. D1 stimulates direct
D2 inhibits indirect. causes movement.
loss of movement: parkinsons dopamine
excessive movement huntingtons (degeneneration of indirect pathway)
how do association areas work of cerebral hemispheres and how do they contribute to our interpretation of the world. What's an agnosia?
retina sees very similar things, but association cortex has to compare them to previous life experiences.
close to primary cortex is an association cortex for that thing.
Agnosia: can't determine what something is even tho you're consious of the sensory info.
Damage to a primary, couldn't feed or see. but damage to association you can feel and see but don't know what is it.
describe organization and function of the cerebral hemispheres and of wernickes and brocas areas in the ability to understand and express language.
its function of a single cerebral hemisphere, mostly (90%) left hemisphere in right handed ppl, left hemisphere is in 70% left handers, and remaining 30% mostly mixed or right hemisphere.
decipher sound waves and make them meaningful.
wernickes area: parietal and tempporal lobe junction. for comprehension (written and spoken), not making sense and have a hard time comprehending what you say too
broca's area: inferior frontal lobe, anterior to head area of motor cortex.
for generation of language
connected by superior longitudinal fasiculus
Aphasias: can't use language.
common features of basal ganglia and cerebellum?
no direct projections to spinal chord
modify performance of motor neurons via feedback
- receive a copy of motor command
-info processed before it returns to origin
- circuits that are modified.