Principles of Sensory Physiology Flashcards

1
Q

What is a stimulus?

A

A change detectable by the body

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2
Q

What are the 5 modalities, or energy forms, of stimuli?

A
Heat
Light
Sound
Pressure
Chemical
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3
Q

Receptors are found at the _________ end of _______________.

A

Peripheral end

Afferent Neuron

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4
Q

Receptors convert the energy from a stimulus into _________________. This is called ___________________.

A

Electrical signals

Sensory Transduction

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5
Q

Stimuli bring about _________ potentials known as ________________ in the receptor.

A

Graded Potentials

Receptor Potentials

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6
Q

Receptors are specialised to respond to ____ stimulus, the ___________________.

A

One stimulus

Adequate stimulus

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7
Q

Some receptors can respond weakly to other stimuli, this gives rise to _______________________________.

A

The same sensation that the receptors adequate stimulus would cause

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8
Q

What are the 6 types of receptors and their adequate stimuli?

A
Photoreceptor = light
Mechanoreceptor = mechanical energy
Thermoreceptor = heat and cold
Osmoreceptor =  changes in osmotic activity
Chemoreceptors = specific chemicals
Nociceptors = Tissue damage
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9
Q

Receptors can either be:

A

Specialised endings of afferent neurons
OR
Separate receptor cells closely associated with the peripheral ending of a neuron

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10
Q

Stimulation of a receptor results in a change in ___________________. This usually occurs due to the opening of _______________. which causes an __________ and .’. ______________.

A

Membrane potential
Na Channels
Influx of Na
Depolarisation

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11
Q

What makes the receptor potential a graded potential?

A

The stronger the stimulus, the greater the permeability change and .’. the larger the receptor potential.

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12
Q

Because receptor potential have _____ refractory periods, summation in response to rapidly successive stimuli is ________.

A

No

Possible

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13
Q

How do specialised afferent endings transmit the signal to the afferent neuron?

A

If depolarised to threshold, voltage gated Na+ channels open and trigger an AP that is conducted along the afferent neuron

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14
Q

How do separate receptor cells transmit the signal to the afferent neuron?

A
  1. Receptor potential promotes opening of voltage gated Ca2+ channels
  2. Ca2+ entry causes exocytosis of neurotransmitters (nts)
  3. nts diffuse across the synapse and bind to receptors on the afferent
  4. Na+ channels open = AP
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15
Q

Where are APs initiated in the efferent and interneurons?

A

Axon Hillock: region at the start of the axon next to the cell body

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16
Q

Where are Aps initiated in afferent neurons?

A

The peripheral end of the fibre next to the receptor, a long distance from the cell body

17
Q

The larger the receptor potential, the _________ the frequency of APs

A

Greater frequency of APs

18
Q

The more rapidly an afferent fibre fires it will release _____ neurotransmitter.

A

More nt

19
Q

What is adaptation?

A

The ability of a receptor to diminish the extent of it’s depolarisation despite a sustained stimulus strength

20
Q

What are tonic receptors?

A

Receptors that do not adapt or adapt slowly, they are useful when it is important to maintain info about the stimulus i.e. muscle stretch receptor

21
Q

What are phasic receptors?

A

Receptors that adapt rapidly to stimuli by no longer responding to a maintained stimuli. They are useful when it’s important to signal a change in stimulus intensity i.e. touch receptors

22
Q

How do mechanoreceptors detect stimuli?

A

Mechanical forces distort non-specific cation channels in the membrane of these receptors which causes Na+ entry = receptor potential

23
Q

What are some examples of tactile receptors?

A

Hair receptor - rapid adaptor, senses hair and gentle movement

Merkel’s Disc - slow adaptor, senses light sustained touch and texture

Pacinian Corpuscle - rapid adaptor, senses vibration and deep pressure

Ruffini endings - slow adaptor, sense deep, sustained pressure and skin stretch

Meissner’s Corpuscle - rapid adaptor, senses light, fluttering touch

24
Q

How do receptors adapt?

A

Adaptation is a result of inactivation of channels that opened in response to the stimulus

25
Q

What is an accessory structure?

A

Cellular or non-cellular structures that modify the stimulus before it reaches the receptor, can filter or amplify the stimulus

26
Q

What are labelled lines?

A

Discrete chains of neurons synaptically connected in a particular sequence to accomplish progressively more sophisticated processing of sensory information.

1st order sensory (detects) –>2nd order sensory (relays)–> 3rd order sensory (in the thalamus, directs info to correct region in the brain)

27
Q

What are somatosensory receptors?

A

Specialised neurons that usually don’t have a synaptic input

28
Q

What are the features of a somatosensory receptor?

A
  • Has 2 axons
  • Have specialised ion channels at the end of 1 axon that open in response to the stimulus (Mechanical force, temp, pH, factors that signal tissue damage)
  • Opening of these channels = generator potentials
29
Q

What is a Nociceptor?

A

A receptor that respond to noxious/harmful stimuli, they have free nerve endings

30
Q

What are the 2 categories of nociceptors?

A

Aδ fibres: respond to intense mechanical stimuli, fast conduction due to thick myelinated fibres
C fibres: respond to noxious chemical and thermal stimuli, slow conduction due to lack of myelin

31
Q

Thermoreceptors result in 4 main types of sensation:

A

Cold
Cool
Warm
Hot

32
Q

How do thermal receptors detect stimuli?

A

They detect the relative difference in temperature between the external and internal enviornment

33
Q

What is a receptive field?

A

The area that a receptor is responsible for responding to stimulus