LO CNS Flashcards
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.
Vestibular apparatus
- 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
- -contain perilymph
- scala media
- -contain endolymph
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:
- brainstem: consiousness, level of consiousness
- reticular formation, ascending and descending neurons. - 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. - 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:
- noepinephrine: focus on a task, suppress less important info. if damaged, less arousal.
- dopamine: focus on accomplishing something and waking, promotes motivation and exploratory behaviors, if damaged, youre not motivated.
- serotonin: quiet wakeful state, modulator, lack of gives you insomnia
controls anxiety and aggression - histamine: midbrain, wakefulness, antihistamines are drowsy
- 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).
intarlaminar TRN - mesh of neurons, dense reciprocal connections with other areas - GABA ergic neurons, 40hz biring
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.
