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First semester > PSL - CNS and senses up until Lec 4 > Flashcards

PSL - CNS and senses up until Lec 4 Flashcards

1
Q

what make up the CNS vs the PNS

A

the CNS is made up of brain and spinal cord while the PNS is made of everything outside the CNS as it includes all neurons and parts of neurons outside CNS

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2
Q

how is the PNS further divided into

A

PNS is divided into the somatic nervous system which controls volunatry action using skeletal muscle and then the autonomic nervous sytem which maintain the viseral functions like heart rate and breathing

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3
Q

what is the enteric nervous system

A

it is part of autonomic nervous system which is controlled by digestion and movement of gut as it gets input from spinal cord but cna also work independentaly

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3
Q

What are the ventricles in the brain and what are they filled with

A

thereare 4 ventricles: 2 lateral vnetricals-one in each hemisphere-, third ventricle, fourth ventricle which are connected to spinal cord through central canal
all are filled with CSF

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4
Q

order the following from one with most number of neurons to least: CNS, enteric nervous system, and PNS

A

CNS has the most as the brain by itself contain around 86 billion and then the spinal cord has another 1 billion
PNS which has around less than 1 billion
ENS which has around 100-600 millions

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5
Q

What are glia cells

A

found in both CNS and PNS to protect and support neurons

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6
Q

how are the white and grey matters of teh CNS different

A

grey matter- have nerve cell bodies, unmyelinated axons, nd dendritis, the cell bodies are arranged in layers or in clusters called nuclei
white matter- consist of myelinated axons running in bundles called tracts

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7
Q

What are clusterrs of neurons called in PNS and what are bundles of axons called in PNS

A

cluster of neurons= ganglia
bundle of axons= nerves

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8
Q

how many segments does the CNS have and what do these segments consist of

A

there are 31 segments and each has pair of spinal nerves which consist of dorsal root and ventral root

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8
Q

How much energy does the brain utilizes

A

the brain make up around 2% of body’s mass but gets 15% of blood pumped by heart and consumes half of body’s glucose
even though that sounds like brain is using too much, thta is nothing compared to amount of energy other computers need that try to mimic teh brain

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9
Q

How does the CNS save energy

A

by limiting the communication of neurons since neurons communicate by sending AP down their axons, these AP takes lot of energy and energy supply to CNS support low rate of firing as it permits only 4% of neruons to fir in the cortex which is one spike every 6 sec
so communication is expensive and CNS has to use it sparingly

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10
Q

what is the difference between the dorsal root and ventral roots of the segment in spinal cord

A

dorsal root- carries afferent signal which is an incoming sensory signal and the dorsal root ganglion has cell bodies of neurons carrying these signals
ventral root- caries the efferent signal which is an outgoing one from CNS to body which also includes motor signals
dorsal= toward the back, ventral= toward the belly

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10
Q

where can the grey matter be found and where are the dorsal and ventral horns

A

the grey matter is in teh middle of spinal cord and has butterfly shape where it has ventrical and dorsal horn on each side

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11
Q

wht are the two nuclei in the grey matter

A

sensory nuclei- in dorsal horn because the signal arrive on dorsal root as somatic sensory nuclei get signal from skin and visceral sensory nuclei get signal from viscera , there is one somatic on eth right dorsal horn and one viseral one the left dorsal horn
efferent nuclei- are ventral, the autonomic efferent nuclei on the right ventral horn sends command to gland and smooth muscle and the somatic motor nuclei in leftventral horn send command to skeletal muscle

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11
Q

what are the 3 types of tracts that the white matter consist of

A

ascending tracts- carry sensory signal to brain, are mainly dorsal since sensory signal arrive at dorsal horn
descending tracts- are ones carrying signal from brain as they are mainly ventral, where the outgoing signal leave CNS
propriospinal tracts- stay in the spinal cord

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12
Q

How does the knee crack reflex happen when the physician hit the knee with rubber hammer

A

the hammer stretch’s a ligament below the kneecap and the snesory fibers carry this stretch news to dorsal horn and the sensory fibres send a branch up to teh brain but aslo excites neurons in ventral horn so those send signal out to the leg muscles to contract and counter the stretch so teh spinal cord ends up responding to stimuli without consulting the brain

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13
Q

\What are teh major six divisions of the brain

A

the cerebrum, cerebellum, pons, medulla, diencephalon, midbrain

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14
Q

What does teh cerebral grey matter include

A

an outer layer called cortex, limbic sysrtem, and basal ganglia to help control movement

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14
Q

What make up the brain stem and what are some of the main functions of the brain stem

A

brain stem consist of the medulla, pons, and midbrain and it is the main central center for any autonomic functions and reflexes like breathing, swallowing, vomitting, and regulating blood pressure

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15
Q

what cranial nerves arise from brain stem

A

cranial nerves III-X, XII,

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15
Q

What connects the 2 hemispheres

A

the corpus callosum whoch is large bundle of myelinated sheath

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15
Q

what are cranial nerves

A

the ones that enter and leave teh brain rather than the spinal cord, the information arrive or leave brain to go otr come from peripheray

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16
Q

What are the functions of the parts that make up teh diencephalon

A

thalamus- process information going to and from cerebral cortex
hypothalamus- regultes behavioural and endocrine and autonomic homeostasis ]
pituitary and pineal glands secrete hormones

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16
Q

what consist teh diencephalon

A

the thalamus, hypothalamus, pituitary, and pineal

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17
Q

What is cerebral lateralization

A

the idea of teh 2 hemisphere’s functions differing where the left hemisphere is more language and math while the right hemisphere is more spatial analysis

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18
Q

what are teh 4 lobes of the brain

A

frontal, temporal, occipital, and parietal

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19
Q

what is cingulate gyrus

A

part of limic system which is found in each hemisphere

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20
Q

what is the limic system

A

an evolutionary old group of brain regions which are the cingulate gyrus, amyglada, and hippocampus
it is concerned with motivation, emotion, and memory

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21
Q

What are the senses we are conscious of and which aren’t we conscious of

A

the consious sense are: 5 spatial sense where each has its own organ and are vision, hearing, equilibrium-sense motion, taste and smell , there are also 4 somatic senses which we are conscious of: touch, temperature, proprioception, and nocicption and are somatic because they share one sense organ which is teh skin
the unconscious senses are ones like blood pressure, lung inflation, blood glucose concentration, internal body temp, pH, etc

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21
Q

what do teh cells that have receptores to precieve stimuli do

A

these cells will convert stimuli into electrical signal and this conversion is called transduction

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22
Q

what are these receptor cells that are transducting the stimuli into electrical signal

A

these cells can be neurons like in vision or non neuronal epithelial cells like in hearing and even if they are neuronal, they may or may not fire an AP

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23
Q

the receptor cell is converting the stimuli into an electrical signal, what does that do to the rest of teh cell

A

this electrical signal is a graded change in membrane called receptor potential and depending on the change, it amy cause release of neurotransmitters to affect the neuron and if teh receptor is neuron, it can fire AP

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24
Q

does that mean receptor cells can only respond to the energy they are most responsive to

A

no, if the other stimuli are powerful, then the receptor cell will also be responsive to them

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24
Q

What is adequate stimulus

A

each type of receptor cell have it which is form of energy the receptor is most responsive to

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25
Q

how is receptor’s senstivity determined

A

by their receptor threshold which is teh weakest stimuli that will cause response and some photoreceptores can detect single photon of light while others might cause response only if there is at least 10 photons of light

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26
Q

how are receptors classified

A

according to their adequate stimuli:
chemoreceptores- respond to specific molecules/ions
mechanoreceptores- respond to mechanical energy like pressure, vibration, sound, gravity
thermoreceptores- respond to temp
photoreceptores- respond yo light

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27
Q

how is perceptual threshold different from receptor threshold

A

perceptual threshold is the weakest stimuli that will cause conscious perception in organism

28
Q

What is stimulus modality

A

sensory neurons don’t just carry electrical and energy signals throughout the process, they also carry other aspects of the stimulus like its modality, which just means what is the type of stimulus, is it light/sound/touch/ect and sensory systems can indicate that by labelled lines which means modality is revealed by which axons carry signal( the neurons activated are in which pathway, like photoreceptores activity means it is a light stimulus)

29
Q

What is teh idea od convergence

A

since many neurons are involved in sensory system, there are primary neurons which are the receptor cells or cells immediatly downstream of them, and those will synapse ontp secondary neurons, those secondary neurons may synapse into teritary ones and so on, but at any stage of synapse, amny presynaptic neurons will contact any one of post synaptic cell, so postsynaptic cell willhave convergence of signal from more than one presynpatoc cell and this allows higher up neurons to combine data from any receptor

30
Q

How do neurons also represent intensity

A

intensity is teh strength of teh stimuli and neurons can also represent that in two ways:
1- population coding which means stronger stimuli will have more neurons activated
2- frequency conding where stronger stimuli can cause neurons to fire at faster rate
these two ways can also be combined like strong stimuli increasing fire rates and causing more neurons to be active

31
Q

What does it mean when cells have dynamics

A

that means their activities don’t depend on stimuli only but also on how the stimuli is changing over time

32
Q

What are the three different dynamic in cell

A

phasic cell- cell responding breifly to any change and then ceasing firing
tonic cells- cell maintaining their activities when stimulus doesn’t change so they carry info for signalling at present levels
phasic tonic- react to change but doesn;t return all the way to zero firing when stimmulus is constant so they carry information about the steady level

33
Q

What type of dynamic do retinal cells have

A

phasic as they report change in your visual world when somthing moves, but if everything is constant, then there is nothing reporting

34
Q

Why are phasic signalling more efficient

A

because tehy make communication more efficient since it is reporting temporal changes which are changes through time

35
Q

What are spatial changes

A

another efficinet way of reporting changes but it is changes between neighbouring regions of space, also known as contrast where there is strong contrast in edges

36
Q

What is lateral inhibition

A

it is when cells inhibit their neighbors or inhibit cells their neighbor’s excite and this can help sensory systems accentuate edges

37
Q

do all sensory pathways run through thalamus for higher processing nd then go to their prospective regions

A

no, most pathways run though thalamus but olfactory pathwyas dont and equilibrium pathways project mainly to cerebellum

38
Q

What does it mean by brain making inferences

A

since the brain has to guess most of the time about the things around it, it can be fooled and mistrust coinsidences to mean something else

38
Q

What is lens

A

it is a transparent disk that focuses light and suspended by ligmants called zonules, it also divides the eye into 2 chambers: antyerior chamber is the one in front of the lens which is filled with aqueous humor and behind the lens is the vitrous chamber which is filled with the vitrous body(clear jelly that help maintain eyeball’s shape)

39
Q

What is the cornea

A

transparent buldge at front of the eye which is continous with the white of the eye (sclera- outer wall of teh eyeball) AND LIGHT ENTERS EYE THOUGH THE CORNEA

40
Q

What is retina and how does light go through teh eye

A

retina is inner lining of the eye that contains teh photoreceptores and the cornea with the lens focus the light on retina
the light passes from cornea to lens throufh hole in iris called pupil

41
Q

How does the pupil adjust with light

A

pupil can change size: in bright light it constrict to reduce the light reaching lens and in teh dark it dilate 20 times bigger to let more light in

42
Q

what controlls the pupil size changes

A

the smooth muscles in iris where in bright light the parasympathatic signal from brain contracts the ring shaped pupilary constrictor muscle shrinking the pupil and in teh dark it is the sympathatic signalling from brain that contract the radial pupilary dilator muscle of teh iris dilating pupil

43
Q

What does it mean by pupil helping focus light

A

small pupil ensures that each point on retina recieve light from just one direction in space and that is what focusing mean

44
Q

How is depth of field controlled by pupil

A

when pupil constrict, we have full depth of field as everything seen is equally in focus and when pupil is dilated, we have shallow depth of field as only object near one specific distance are oin focus

44
Q

Why does bending of the light occur in refraction

A

because light hits medium with different refreactive indecs like the one between air and collagen of the corneas

44
Q

What is the structure of teh lens

A

it is a mesh of long cells without nuclei, packed with clear proteins called crystallins and zipped together in concentric layers for flexibility and have no blood supply but absorb nutrients from aqueous humour

45
Q

How is the problem of using pupil alone to focus light fixed

A

using refraction which is light bends when it enters medium with different refractive index

45
Q

Is lens a concave or conves shaped

A

lens is convex shaped which is fatter in middle and thinner at edges to make light rays converge to focal point

45
Q

What structures of teh eye are responsible for the refraction of light

A

cornea is repsonsible for 2/3 of the refraction due to its different refractive indeces and 1/3 of refraction is due to the lens which changes shape to adjust focus

46
Q

How does rounding the lens affect light rays

A

rounding the lens will bend the light more and so has closer focal point and to have clear vision, the focal point must fall on retina

46
Q

How does angle at which the light rays hit teh medium of different indeces affect refraction

A

it depend on angle at which light rays hit interface between media which it the angle at which it hits lens surface and the angle depend on shape of teh lens and directions of light ray
it it strikes lens at right angles, then it doesn’t bend at all

46
Q

What will happen if teh object get closer but the lens doesn’t change shape

A

if object draw closer and the lens doesn’t get rounder then the focus fall behind the retina, teh focal point isn’t on retina so vision is blurry

47
Q

How does ciliary muscle get affected by signals from nervous system to change shpae of the lens

A

parasympathetic input from brain contract teh ring shaped ciliary muscle reducing tension in zonules and make lens rounder so light rays bend more and focal points move forward
sympathatic input will relx ciliary muscle making lens flatter for far vision

48
Q

what is accomodation

A

rounding lens fro near vision and the closest point a person can focus is called near point accomodation

49
Q

What is the issue with hyperopia and how is it fixed

A

this is also known as far sightedness where focal point fall behind retina so cna see object far but not close one because focal point falls behind retina
solved with convex lens because the lens of the eye isn’t beinding enough light rays so extra convex help out with bending the light rays for the eyes

50
Q

What is presbyopia

A

when with advance aging the lens stiffens and hinders accommodation

51
Q

what is the issue behind myopia and how is it fixed

A

also known as near sightened where the focal point falls in front of retina so can see close things but not far ones and solved with concave lenswhich causes light rays to disperse so they counteract the too much bending of light rays by the eye’s lens by spreading rays out slightly

52
Q

What are photoreceptores

A

they are in retina and are light sensitive neurons that convert light into electrical energy in cells and this conversion is called phototransduction

52
Q

what is fova’s role

A

use fovea for detailed vision, 5 degrees away from its centre

52
Q

What are the two types of photoreceptores in the retina and how are they different

A

they are teh cones and rods, cones are around 6 million and rods are 120 millions and are neurons but don’t fire AP, they respond with membrane graded potentials

52
Q

how are photoreceptores distributed in retina

A

they are distributed non uniformily where they are mosly dense packed in macula which is a central disk that have central pit called fova

52
Q

what is the structure of the cones and rods

A

they both share similiar structure:
outer segment- membrane folds into disk like layers which contain the visual pigment that respond to light
inner segment- where teh nucleus and organells are for protein synthesis and in basal layer have synapse that release glutamate

53
Q

how do photoreceptores detect light

A

using membrane bound visual pigments, these pigemnts change shape when l;ight hit them starting chemical cascade that hyperpolarize the cell which reduces the release of glutamate

53
Q

what is teh type of pigment in cones and rodes

A

cones have rhodospin and there are 3 types of cones with each having its own type of pigemnnt

54
Q

what is the characteristics of the blind spot

A

there are no receptores in it and that hole is where axons carrying visual information exit eyeball to form optic nerve

55
Q

How are the cones and rods different when it comes to light detection/sensitivity

A

cones are for bright light while rods are for bdim light that is because cones are less sensitive than rods and are responsible for vision in bright light and for distinguishing colours but they don’t operate in dim light so the ones that will take their place in dim light will be the rods that cna detect single photons but operate only in low light as their rhodopsin is broken down in daylight so they don’t sense light

56
Q

how is the distribution between rods and cones in the eye

A

the fovea contains mainly cones while the peripheral retina contains mainly rods and that is one of the reasons why the peripheral retina is more sensitive to light than fovea

57
Q

what makes up the three layers of neuron in retina and how is convergence utilized in there

A

the photoreceptores make up teh first layer that will synapse onto bipolar cells which make the second layer and those bipolar cells will synapse onto ganglion cells which make up the third layer
as the synapse go from photoreceptores to ganglion, convergence is used so that the 126 million photoreceptores are condensed into 1 million ganglion cells as
up to 45 photoreceptores converge onto one bipolar cell and then 2 bipolar cells converge onto one ganglion cells in peripheral retina and least in fovea where one bipolar synapse onto one ganglion

58
Q

how does the receptive field for bipolar cells look like

A

every neuron in visual system has receptive field also called visual field which is region of retina where light affect the cell’s activity and bipolar cells have a center surround fields with round center regions and doughnut shaped surround

59
Q

what are the two types of bipolar cell receptive fields

A

on center and off center
on center= excited by light in center of their fields and inhibited by light in surround so they respond when light spot fill their center and surround is dark
off center cells= inhibted by lught in center and excited by light in surround so they respond when dark spot fills their center and surround is light

60
Q

when do bipolar cells react the strongest

A

when lighting is not unifrom so there is contrast and that is because when light is uniform, bith types of bipolar cells (on and off center) are nonresponsive because the effect of center and surround cancel so cell is at its resting level of activity and evcen when bipolar cells respond, they respond with graded membrane potential

61
Q

How do ganglion cells contrast and compare with other layers of cells in retina

A

they get synapsed by bipolar cells biut unlike photoreceptores and bipolar cells, they do fire AP but like polar cells they mostly have center surround receptive fields and these fields are also on and off center so they best respond to contrast

62
Q

how does ganglion cell being positioned in different part of retina, either in fovea or peripheray affect their receptive fields

A

ganglion cell near fovea gets input from only few photoreceptores and are mostly cones and they are less sensitive to light but has better spatial resolution since they are getting input from less densly packed cones while in peripheray, the ganglion cell is very sensitive to light but poor at resporting spatial detail because it is getting info from wide number of rods

63
Q

What are the three classes of ganglion cells based on how their signals is used in brain

A

magnocellular ganglion cells (Mcells) which provide info that is used by brain to infer movement of object and these cells are phasic
parvocellular ganglion cells (Pcells) provide info used to infer form and fine details
melanopsin ganglion cells, make up 1% of ganglion cells, are photoreceptores with their own pigemnt called melanopsin and tbhey project to suprachiasmatic nucleus

64
Q

how is optic nerve formed

A

each of the million ganglion cellls in each retina send their axon out the back of eye through blind spot and these fibres from each eye form their own optic nerve aka as cranial nerve II

65
Q

what is optic chiasm

A

when each of the optic nerve reached this point called optic chiasm, half of its fibres cross to the other side and fibres from nasal half of each retina cross

66
Q

Why do the fibres cross

A

that is because in the eye, the right of the scene projects onto half side of each retina which is the nasal side of right retina and temporal side of left retina so because nasal fibres cross, all information from right hemifield come together in left cerebral hemisphere and vice versa

67
Q

how does info from chiasm then travels

A

the info move from chiams to thalamus and then to cortex as teh nerve bundle emerges from chiasm are now called optic tracts which ends in 2 lateral geniculate nuclei in thalamus which projects via the optic radiation to primary visual cortex snd together the 2 LGN have aroudn 2 million neurons while V1 have around 300 million in occipital lobe

68
Q

how is the arrangement of cells in retina related to the neurons in brain

A

many areas in the brain are organized retinotopicallu as neurons close to each other in brain get info from close together parts of retina but it doesn’t preserve area, even though fovea is small area opf retina, it projects to large area in V1 and other cortical regions and LGN and those large proportions of visual cells in brain receive and process data from foveal photoreceptores and one of reasons fovea get such a large space in brain is because it has many photoreceptores, bipolars, ganglion cells, etc.

First semester (14 decks)

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