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PHYSL 210 > CNS - Lecture 3 > Flashcards

CNS - Lecture 3 Flashcards

1
Q

What is localization

A

determining the position of a stimulus on or within the body

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2
Q

explain the location and transmission of modality-specific signals

A

travels along sensory axons in specific spinal cord tracts towards the brain

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3
Q

The ability to locate a stimulus depends on:

A

the size and the density of the receptive fields of the receptors

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4
Q

lateral inhibition

A

enhances spatial acuity within the CNS by refining sensory information in afferent neurons (like making an image sharper)

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5
Q

Acuity is

A

the ability to differentiate between closely spaced stimuli

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6
Q

How does spatial acuity work

A

ascending sensory signals are focused by lateral inhibition within the CNS

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7
Q

process and outcome of ascending sensory axons that cross the midline in the brain

A

process: ascending sensory axons synapse on brainstem neurons that cross the midline

outcome: conveys sensory information from the right side of the body to the left side of the brain & vice versa

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8
Q

what is two-point discrimination

A

the ability to distinguish between two closely spaced stimuli

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9
Q

small receptive fields and high two-point discrimination/acuity are a result of

A

tightly packed receptors

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10
Q

large receptive fields and low two-point discrimination/acuity are a result of

A

spaced receptors

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11
Q

what is the relationship between receptive field size and acuity

A

receptive field size determines sensory acuity or two-point discrimination

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12
Q

what are receptive fields

A

specific areas or regions of the body that, when stimulated, activate a particular sensory neuron or receptor

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13
Q

overlapping stimulation between neighbouring receptive fields provides

A

general information about the location of a stimulus

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14
Q

what is divergence

A

each sensory afferent sends branches to many neurons in the CNS
see document for diagram

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15
Q

what is convergence

A

a given neuron in the CNS receives inputs from many sensory afferents
see document for diagram

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16
Q

how does lateral inhibition allow the location of a stimulus to be perceived more accurately?

A

focuses the activation of the neurons on the centre of a stimulus

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17
Q

describe firing rate profile in the presence of lateral inhibition

A

narrower firing rate profile due to lateral inhibition

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18
Q

two-point discrimination is best and worst where?

A

best: hands and the face
worst: abdomen and parts of the limbs

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19
Q

why is two-point discrimination best on hands and face

A
  1. there is a higher density of receptors
  2. more surface area of sensory cortex is devoted to sensory input from the face and hands
20
Q

sensation

A

the conscious awareness of a stimulus

21
Q

perception

A

when a sensation is combined with an understanding of it’s meaning

22
Q

sensation and perception result from processing in the

A

cerebral cortex

23
Q

what parts of the body is the somatosensory cortex largely devoted to receiving input from? which parts not as much?

A
  • face and hands
  • abdomen, legs and feet
24
Q

what does a sensory topographic map show

A

which areas of the skin are connected to specific regions in the brain.

25
Q

what is projection area

A

a specific region in the brain that receives and processes information from a particular sensory organ

26
Q

projection area of any given organ in the sensory cortex is related to

A

functional importance

27
Q

plasticity

A

topographic maps change according to usage

28
Q

dynamic plasticity means

A

the maps constantly change, sometimes within seconds

29
Q

what is descending inhibition

A

activity descending from higher centers in the brain and brainstem that can block out certain types of sensory information by inhibiting neurons in the afferent pathway

30
Q

how does presynaptic inhibition act

A

by reducing transmitter release at synapse between first and second order sensory neurons. inhibits specific sensations

31
Q

how does postsynaptic inhibition act

A

acts by hyperpolarizing second order membranes to move their potential further away from threshold

32
Q

how long does postsynaptic inhibition last?

A

very short, less than a ms

33
Q

what mediators are released when tissue is damaged, what do they do?

A

prostaglandins and histamine - activate the pain receptors

34
Q

pain receptors fire _______ _________ which travel to the _______ part of the spinal cord

A

action potentials
dorsal

35
Q

what releases substance P and what does it do

A
  • activated pain fibres in the spinal cord
  • activates interneurons called projection neurons
36
Q

what do projection neurons do

A

signal pain (pain sensation)

37
Q

what is analgesia

A

suppression of pain transmission

38
Q

how does aspirin work

A

blocks production of prostaglandins released by damaged tissue

39
Q

what does gabapentin do

A

blocks conduction of nociceptors

40
Q

how do opioids (morphine) work

A

block the release of substance P onto projection neurons in spinal cord

41
Q

What neurons release endogenous opiate neurotransmitters

A

Neurons in the brainstem and reticular formation

42
Q

What are the functions of endogenous opiate neurotransmitters

A
  • reduce the release of substance P (reduce activity in the projection neurons that signal pain to the thalamus and the cortex)
  • gets released during fright, flight and flight reactions to reduce pain (nociceptive input)
43
Q

Why is pain from the viscera and internal organs interpreted by the brain as pain on the skin

A

Sensory afferents from the vicera enter the spinal cord and synapse onto the same interneurons as sensory afferents from the skin

44
Q

in the somatosensory system, pathways that mediate pain and temperature are different than those that mediate

A

touch pressure and muscle stretch (mechanoreceptive)

45
Q

What afferents are involved in the Anterolateral system

A

Pain and temperature

46
Q

What afferents are involved in the Dorsal column system

A

Touch, pressure and stretch

47
Q

** See document for the processes of neuron transmission in the somatosensory system

A

PHYSL 210 (16 decks)

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