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From Flashcardlet > PHYSIOL [A] nervous > Flashcards

PHYSIOL [A] nervous Flashcards

0
Q

what is the motor homunculus?

A

motor cortex with body plan of muscles mapped into it

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1
Q

what is the hierarchical levels in direct motor control in the CNS?

A

cerebral cortex(frontal lobe motor area)
brain stem
spinal cord

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2
Q

how do nerves attached to muscles get to the motor cortex?

A

gather in tracts through spinal cord and project to neighbouring neurons in the cortex

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3
Q

what 3 main things does the brain stem contribute to motor control?

A

1) integration (visual, vestibular(sense of balance in inner ear) & somatosensory(touch, vibration, pain))
2) maintains flow of excitatory stimuli to spinal cord => posture control
3) vital responses eg. yawning, head movements

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4
Q

how does information move up/down spinal cord?

A

within space inside vertebra are columns of neuronal structures(axons) clustered together
carry info up and down through afferent and efferent tracts

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5
Q

dorsal side?

A

“back entry” for spinal neurons

information comes INTO this “door” and goes to brain

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6
Q

ventral side?

A

“door” for information(signals) going from spinal cord out to body

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7
Q

what is the dorsal root ganglion

A

neuronal cell bodies

axons may be in your finger but cell body is located all the way back near dorsal spinal cord

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8
Q

what is the spinal cords role in motor control?

A

autonomic & stereotyped reflexes
withdrawal from painful stimuli
alternating activation of flexor and extensor(helps set proper motor pace)

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9
Q

where are the cell bodies of sensory neurons located in the PNS?

A

just outside the spinal cord

dorsal root ganglion

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10
Q

what is the function of motor neurons?

A

control contraction of skeletal muscle

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11
Q

where are the cell bodies of motor neurons located?

A

within spinal cord

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12
Q

how do sensory and motor neurons connect?

A

within grey matter of spinal cord via inter-neuron

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13
Q

what influences modulation of motor control?

A

cerebellum

basal ganglia

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14
Q

so info is processed in motor cortex but then where does it go before becoming final motor command?

A

motor cortex -> basal ganglia & cerebellum -> motor cortex ->
brain stem -> spinal cord

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15
Q

role of basal ganglia in modulation of motor control

A
  • 80% of total dopamine
  • balance muscle tone
  • suppress unwanted patterns of movement
  • coordinate slow sustained contractions(maintaining posture)
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16
Q

what is Parkinson’s disease?

A
  • up to 90% of the dopamine containing neurons die

- symptoms include tremor, difficulty in initiating movement, rigid posture

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17
Q

which area of the brain is parkinsons mostly associated with?

A

basal ganglia as it contains up to 80% of total dopamine and controls posture/unwanted patterns of movement

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18
Q

what could improve the symptoms of parkinsons disease?

A

prescription of L-DOPA which crosses blood-brain barrier and is converted into dopamine in the brain, aiding to better control movements and posture
-> lots of side effects though

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19
Q

what is the cerebellum?

A

the weird thing that hangs off the end of the brain heh
10% of total brain volume - its so fat
50% of total neurons - thats why it has so many folds!

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20
Q

functions cerebellum?

A
  • coordinates motor programs by modulating the output of the higher brain centres
  • “experience” drives improvement
    ie. motor performance benefits from training eg. elite athletes
  • intended movements(motor cortex) vs. sensory info(from muscles)
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21
Q

so does the cerebellum directly control movement?

A

nope! does not directly control motor nerves..
BUT damage disrupts the coordination/accuracy of movements of limbs and eyes - impairs balance - BUT does not control loss of specific muscle
eg. think of touching your nose diagram

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22
Q

brainstorm(lol pun not intended) some symptons of cerebellum impairment:

A
  • uncoordinated walk/unsteady
  • slurred speech
  • difficulty with repeated patterns of movement(“experience” part dodgey)
  • errors in judging distance(eyes effected)
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23
Q

whats locomotion?

A

the process of movement

the spinal cord controls this, alternating activation of flexor and extensor muscle

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24
Q

describe connections between neurons of the PNS and flexor/extensor muscles:

A

sensory neurons - flexor muscle

motor neurons - flexor and extensor

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25
Q

function of motor neurons in muscle movement?

A

simply follow orders and cause muscle contraction

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26
Q

what is the function sensory neurons in the movement of muscles?

A

they attach to flexor muscle - provide feedback

  • stimulate contraction of a stretched muscle
  • can inhibit motor neurons control of flexor muscle
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27
Q

what is the overall goal of the cerebellum?

A

constantly compares INTENDED MOVEMENTS set by motor cortex, with SENSORY INFO received back from joints and muscles

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28
Q

so what do the modulatory(basal ganglia, cerebellum) areas of the brain actually do?

A

The modulatory systems alter the output of the motor pathway in order to adjust the direction and degree of force

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29
Q

The control of motor function:
(A) involves the motor cortex, brainstem and spinal cord
(B) involves modulatory areas, which are the cerebellum and basal ganglia
(C) is organised into a pattern known as a somatotopic map (motor homunculus).
(D) answers A and B only
(E ) all of the above (A-C)

A

E) all

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30
Q

Cerebellum:
sensory feedback allows correction for errors between ______and _____ setting the______and _____of movements;

A

intent and performance

range and force

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31
Q

What are the 4 attributes of sensory stimulus?

A

1) Modality
2) Intensity
3) Duration
4) Resolution

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32
Q

Modality is an attribute of sensory stimulus…um what does it mean?

A

“type” of sensory stimulus

eg. eye nerves different to ear nerves

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33
Q

Intensity is an attribute of sensory stimulus…um what does it mean?

A

the “strength” of the stimulus

eg. brightness of light, how loud a sound is

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34
Q

Duration is an attribute of sensory stimulus…um what does it mean?

A

how long does it persist?

eg. flashes of light or consistently the same level of light

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35
Q

Resolution is an attribute of sensory stimulus…um what does it mean?

A

position of stimulus
eg. Think of compass experiment! can only feel one point when there’s 2!
ability to distinguish between closely spaced stimuli

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36
Q

what are the 5 main sensory modalities?

modes of senses

A
  1. Photoreception: Light
  2. Chemoreception: Taste, smell, O 2 and CO 2
  3. Mechanoreception: Hearing, vibration, touch, muscle stretch
  4. Osmoreception: Solute concentrations
  5. Nociception Pain: temperature eg. fast pricking pain, slow burning pain, heat and cold
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37
Q

where is sensory info routed through?

A

all sensory input pathways are routed through the thalamus and project to specialised areas of the cerebral cortex from there

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38
Q

how can array of sensory info remain interpretable?

A

info is mapped

  • routed through afferent pathways
  • retains spatial organisation
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39
Q

where are each of the following systems mapped?

A 
somatosensory = parietal cortex - somatosensory homunculus
visual = occipital cortex - retinotopic map
auditory = temporal cortex - tonotopic map
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40
Q

what actually are nerves?

A

collected axon tracts, which carry signals from adjacent receptive fields throughout the body

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41
Q

how do peripheral nerves enter CNS?

A

through spinal nerve dorsal roots to spinal cord

OR directly into brain stem via cranial nerves

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42
Q

what are Dermatomes?

A

body regions for each peripheral spinal nerves

**think of diagram of spine, different area = different body areas

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43
Q

what are the 4 dermatomes?

A

cranial
thoracic
lumbar
sacral

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44
Q

state somatosensory pathway FROM receptor TO cortex:

A

receptor ending -> dorsal root ganglion -> spinal cord -> medulla -> midbrain -> thalamus -> cortex

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45
Q

whats the difference between the pathway for pain and touch from receptor to cortex?

A

pathways for pain cross midline at spinal cord level

pathways for touch cross midline at brainstem(medulla) level

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46
Q

how do photoreceptors exit the eye?

A

through the optic nerve, AFTER signals are detected and processed by the retina

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47
Q

explain visual map

A

left field of vision for BOTH individual eyes is mapped in the right occipital cortex

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48
Q

layers of retina from outer most to inner most

A

pigment epithelium
photoreceptors
ganglion cells
optic nerves

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49
Q

where is light captured in the eye?

A

in Rhodopsin in photoreceptors which are at the back of the eye agains the retinal pigment epithelium

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50
Q

after photoreceptors capture light and send info to neurons in local network in retinal layer what intergrates all this info?

A

ganglion cells intergrate the info thats to be sent out of the eye through optic nerve

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51
Q

explain the concept of “seeing” light:

A

dark: cGMP-gated channels are open - steady influx of Na+ ions causing depolarisation and continuous neurotransmitter release
let there be LIGHT(lol): decrease in polarising current => hyperopolarisation => reduced neurotransmitter release - which is interpreted by the nervous system as the perception of light

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52
Q

what is the inner ear for?

A

hearing and balence

53
Q

what area of the inner ear is responsible for sensing sound?

A

the cochlea(snail thingo) it contains hair cell tuned to specific frequencies vibrated by the basilar membrane

54
Q

what is the name/function of loops coming off the cochlea?

A

vestibular apparatus

sense of balance

55
Q

how does info get from inner ear to brain?

A

cochlea and vestibular apparatus each have ganglion to which they send their info, which is then relayed through axons to the thalamus and then to the auditory cortex

56
Q

what happens to the signal after the basilar membrane vibrates the hair cells in the cochlea?

A

hair cells have mechanoreceptors that change the vibration into electrical stimulus

57
Q

describe the basilar membrane:

A

changes in thickness. thinnest at the tip the increases in thickness the further you spiral in
depending where the hair cell sits on the basilar membrane will determine what frequency it picks up.
higher frequency at thinner basilar membrane

58
Q

True or False: Light is detected by closure of cGMP-gated cation channels in the photoreceptors, which results in hyperpolarisation and a decrease in transmitter release.

A

TRUE!

59
Q

True or False: The cell bodies of somatosensory neurons are located at the site of stimulus detection, for example in the skin surface, and do not use axons to conduct the signals.

A

False! still need to get info from periphery to central!

60
Q

what is resting potential?

A

difference in charge inside and outside the membrane, voltage drop
-60mV

61
Q

what are transporters and channels in cell membranes?

A

proteins!

62
Q

describe layers of membrane

A

phospholipid bilayer
cholesterols
protein transporters/channels

63
Q

what type of channel spans entire memebrane?

A

intergral membrane protein

64
Q

describe the phospholipid bilayer part of membrane

A

two parts:
hydrophobic(repel or fail to mix with water) heads with oily tails
only lipid soluble agents can pass

65
Q

how do polar molecules cross the membrane?

A

through protein transporters

66
Q

what ions are in high concentrations inside/outside cell

A

K+ high in

Na+ and Cl- high out, Ca2+ also slightly higher out

67
Q

what substances can directly flux across membrane?

A

alcohol, steroids, gases

68
Q

what is simple diffusion?

A

influx directly related to external substrate concentration(linear)

69
Q

what is facilitated diffusion?

A

influx is a constant maximum limited capacity of cell to contain substrate

70
Q

what channels are open when membrane is at rest? and which way is the ion transport?

A

K+ out

Cl- into

71
Q

explain ions “dual” nature:

A

ELECTRICAL - interaction of charges with voltage -> membrane potential
CHEMICAL - concentration gradient high to low

72
Q

what does the magnitude of an ionic gradient depend on?

A

1) concentration

2) voltage (membrane potential)

73
Q

why are Cl- and K+ channels open at rest but Ca2+ and Na+ aren’t?

A

as their diving forces are at equilibrium
whereas Ca2+ and Na+ both have very strong inwards driving forces, so pathways are closed and only opened for limited periods of time - very controlled

74
Q

what does open Na+ and Ca2+ channels do?

A

drive positive changes in membrane that are excitatory

…generate excitable signals!

75
Q

what do open K+ and Cl- channels do?

A

help maintain negative resting level

76
Q

what is membrane potential?

A

source of potential energy cell uses to do work

77
Q

how does H2O move across membrane?

A

passive diffusion

78
Q

what drives the passive diffusion of H2O?

A

osmotic gradient..low salt to high salt content

“water follows salt”

79
Q

what units measure osmotic pressure?

A

mm mercury

80
Q

what extra feature allows balance of osmotic pressure?

A 
A- 
why? 
K+ and Cl- channels open
Na+ on outside of membrane cannot pass
A- balances positive cannot pass charge
81
Q

functional purpose of K+ channels?

A 
Kv = voltage gated, driven by membrane potential 
Kir = "leak" channel, active @ rest - maintains resting potential
82
Q

functional purpose of Na+ channels?

A

cause excitatory responses!
open in response to depolarisation
ball on string comes and blocks excitatory response

83
Q

why does the excitatory response of Na+ channels need to be kept brief?

A

to allow cell to recover

84
Q

functional purpose of Ca2+ channels?

A

regulates: neurotransmitter release(in synapse), muscle contraction(upon release), secretion of hormones
voltage gated channel
Ca2+ important 2nd messenger, coupling stimuli to responses

85
Q

what type of transport removes leaked ions from inside cell?

A

active transport via ATP pump

86
Q

what does one pump of ATP get?

A

1 ATP used pumps
3 Na+ out
2 K+ in
every high energy use

87
Q

how does active ATP pump contribute to membrane potential?

A

in one ATP pump, 3 Na+ go out and only 2 K+ come in…meaning gain of one net negative charge inside cell

88
Q

what does Ouabain do?

A

blocks the Na+ pump by competing for the K+ binding site

89
Q

what does Digitalis do?

A

blocks Na+ pump

lethal at high doses, but at low doses it is used as a cardiac stimulant

90
Q

how does Na+ work as a co-transporter?

A

Na+ has strong inward driving force, works as co-transporter by utilising potential energy in Na+ gradient to do work.

91
Q

example of Na+ being a co-transporter?

A

coupling with glucose and absorbing it across the gut membrane against a concentration gradient

92
Q

how does Na+ work as a counter-transporter?

A

utilising potential energy of Na+ gradient to move ions against electrical driving force

93
Q

example of Na+ working as counter-transporter:

A

utilises gradient to export protons(H+) to increase intercellular pH level

export Ca2+ ions after response

94
Q

what is the approx. internal and external ionic concentration of
K+, Na+, Cl- and Ca2+

A

K+ internal: 150 external: 5
Na+ internal: 15 external: 150
Cl- internal: 15 external: 150
Ca2+ internal: 0.0001 external: 2.5

95
Q

describe(in order) what happens after an excitatory response(Influx of Na+):

A

influx of Na+ causes positive shift in membrane potential, depolarisation( to around +50)
negative recovery response = repolarisation
Inhibition follows, where membrane potential drops below resting = hyperpolarisation, period in which no new signals can be conducted

96
Q

what equation would you use to calculate the particular voltage needed to balence membrane potential?

A

Ex = 60 log ([Xo]/[Xi])

where “Ex” is voltage at which chemical and electrical forces are equal and opposite(balenced)
and ([Xo]/[Xi]) is the concentration gradient

97
Q

how does the voltage calculation based on Nernst differ for cation and anions?

A 
Ex = 60 log ([Xo]/[Xi]) for cation 
Ex = 60 log ([Xi]/[Xo]) for anion
98
Q

what does Em stand for?

A

membrane potential

99
Q

what is the significance of the Nernst equation?

A
  • at any point other than Ex a driving force for net movement of X across membrane will exist (Em - Ex)
  • greater the diff. between membrane potential and Ex -> greater the driving force
  • however, actual flux required open channels!
100
Q

what 2 factors are required for an ionic gradient to be used to change the membrane potential?

A

1) driving force

2) permeability(open channels)

101
Q

driving force is the difference between _____ and ______:

A

membrane potential and the equilibrium potential

102
Q

what does an action potential actually do?

A

amplifies an input signal

that can be conducted over long distances

103
Q

what is an action potential?

A

event triggered by THRESHOLD depolarisation
rapid positive change in membrane potential (depolarisation)
rapid recovery (repolarisation)
undershoot(hyperpolarisation)

104
Q

where are action potentials found?

A

only in specialised cells with excitable membranes

105
Q

what is meant by action potentials have a stereotypic pattern?

A

voltage waveform

mexican wave in da cells yo

106
Q

describe ion movement at each stage of action potential conduction:

A 
depolarisation = influx of Na or Ca in some tissues(eg. muscles)
repolarisation = efflux of K 
hyperpolarisation = too much K ions leave, membrane potential drops below resting
107
Q

out of all ions which one sets membrane potential?

A

Most permeable ion sets membrane potential

108
Q

where are the equilibrium potentials(Ex) set?

A

at positive and negative limits
Ena = +60
Ek = -90

109
Q

what is the positive feedback loop and how is it limited:

A

Na channels bring positive change

are limited by inactivation mechanism of ball on chain

110
Q

what is the downstroke of activation potential determined by?

A

1) inactivation of Na channels

2) activation of Kv channels

111
Q

how does tetrodotoxin affect action potential?

A

blocks Na channel
SO blocks entire upstroke…meaning there wont be a downstroke..MEANING there wont be an action potential at all, only a small passive response

112
Q

how does tetraethylammonium affect action potential?

A

it blocks Kv channels (voltage gated)
no effect on Na channels so normal upstoke
BUT not as many Kv channels to restore resting so action potential will be prolonged

113
Q

what are dendrites?

A

“antennae” off the cell body (or soma) of the neuron

recieve transmitters from other neurons

114
Q

are all synaptic inputs equal in amplitude?

A

nope!
further away you are the smaller your input
ie. amplitude of effect decays with distance

115
Q

what happens at soma?

A 
integrates info(voltage signals) received in dendrites
summed together, if response is large enough an action potential is initiated at the axon hillock
116
Q

where are action potentials initiated?

A

at the axon hillock of neurons

117
Q

how do action potentials only go one way?

A

limiting the positive feedback loop: INACTIVATION

ball on chain blocks Na channel, initiating recovery period where it cannot be excited

118
Q

what is the refractory period?

A

where inactivation of Na channels have taken place

no response to stimuli as too few Na channels are avaliable to carry current

119
Q

what is myelin?

A

living extensions of the glial cells

it insulates axons to increase conduction distance, speed and efficiency

120
Q

what are oligodendrocytes?

A

octopuses that myelinate axons in CNS

121
Q

what are Schwann cells?

A

myelinate axons in PNS

122
Q

where are voltage gated Na channels located along the axon?

A

they are clustered within the NODES between segments of myelin

123
Q

what is demyelination?

A

occurs in patients with multiple sclerosis

the myelin sheath covering axon is destroyed with inflammation and scarring

124
Q

describe what happens in a demyelinated axon after AP is applied:

A

depolarisation occurs at site of applied AP

but ions leak from axon due to no myelin, meaning theshold is not reached to conduct next signal in wave

125
Q

function of Astrocytes:

A

blood brain barrier

126
Q

function of microglia:

A

play role in defence of brain as phagocytic scavengers

release nerve growth factor

127
Q

location and function of ependymal cells:

A

line the internal, fluid filled cavities of the CNS
contribute to formation of cerebrospinal fluid
serve as neural stem cells with potential to form new neurons and glial cells

128
Q

what connects the left and right side of the cerebrum?

A

corpus callosum

129
Q

what neurotransmitter is released from the vesicles?

A

Acetylcholine

130
Q

What is the name of the specific type of ligand-gated receptor?

A

nicotinic acetylcholine receptor (nAChR)

From Flashcardlet (34 decks)

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