Somatic Senses Flashcards
(49 cards)
1
Q
What is a receptor?
A
- any structure specialised to detect a stimulus, there are different designs
2
Q
What are the somatic senses?
A
- touch
- pressure
- temperature
- pain
3
Q
How many types of receptor present in the skin are there?
A
- three
4
Q
Part A Receptor:
A
- simplest design
- cluster of free nerve endings
- myelinated or not
- sensory nerve fibre
5
Q
What is mediated by design A of a receptor?
A
- pain
- heat
- cold
6
Q
Part B Receptor:
A
- meissner’s corpuscle = touch receptor
- sensory nerve fibre
- has unmyelinated nerve endings
- in a connective tissue capsule
7
Q
Part C Receptor:
A
- pacinian corpuscle = pressure receptor
- unmyelinated nerve ending is surrounded by
- concentric layers of modified Schwann cells
8
Q
What are the last two remaining receptor types?
A
- both control touch
- merkel discs
- ruffini’s corpuscles
9
Q
What are merkel’s discs?
A
- the combination of enlarged myelinated axon terminals and the merkel cell
- the receptor = the merkel cell
- they are close in the epidermal layer
10
Q
What are ruffini’s corpuscle?
A
- in the dermis
- consists of a bundle of collagen fibrils with a myelinated sensory axon
- that branches between fibrils, enclosed inside a flattened capsule
11
Q
What is the signal that receptors generate?
A
- the action potential
12
Q
What is signal transduction?
A
- the process of converting the stimuli into action potentials
13
Q
What is the receptor potential?
A
- the membrane potential change when a receptor responds to a stimulus
14
Q
When is an action potential elicited?
A
- when the receptor potential reaches the threshold
15
Q
Why do receptor potentials occur?
A
- due to ions crossing the cell membrane
- ion channel opening
- change in cell membrane permeability
16
Q
What can cause changes to membrane permeability?
A
- mechanical deformation
- release of a chemical can open ion channels
- changes in tissue temperature
17
Q
When a continuous stimulus is applied, what happens most receptors?
A
- adaptation
- there is a decrease in action potential generation overtime
18
Q
If the steady state changes…
A
- the receptors are quick to respond
- rapidly adapting
- meissner’s corpuscles
19
Q
Baroreceptors are very slow to adapt, so:
A
- good at continually monitoring stimuli
20
Q
What do pain receptors do?
A
- adapt very little
- can become more sensitive to stimuli
- responding to not real stimuli
21
Q
Most touch receptors:
A
- back of hand
22
Q
What is the action potential, what type of response is it?
A
- all or nothing
- can’t be varied
23
Q
How does the brain know what type of signal is being received?
A
- the labelled line principle
= the type of sensation felt when a nerve fibre is stimulated, is dictated by the point to which the fibre leads
= as nerve fibres can transmit only an action potential
24
Q
How can we distinguish between the intensity of pain felt, if the action potential is all or nothing?
A
- spatial summation
- temporal summation
25
What is spatial summation?
- occurs when
- as the stimulus intensity increases,
- so does the number of individual neurones within a nerve generating an action potential
26
What is temporal summation?
- this occurs when,
- as the stimulus intensity increases,
- so does the number of action potentials generated by individual neurones per unit time
27
What are the first two somatic sense?
- touch
- pressure
28
What is pressure?
- sustained touch
29
What are the stimuli for touch and pressure?
- mechanical deformation
- receptors involved = mechanoreceptors
30
What is light touch mediated by?
- Merkel discs
- meissner’s corpuscles
31
What is heavy touch mediated by?
- Ruffini corpuscles
32
What is pressure mediated by?
- pacinian corpuscles
- Ruffini corpuscles
33
Where are touch and pressure receptors found?
- throughout the skin & subcutaneous tissue
- skin, fingers, lips
34
What is the third somatic sense?
- temperature
35
How is the human body able to detect thermal gradations in its external environment?
- discrimination of temperature depends on the activation of three types of receptors
36
What are the three types of receptors for temperature?
- cold receptors
- warm receptors
= both are thermoreceptors
- pain receptors responding to extremes of temperatures
37
When are warmth receptors stimulated?
- when temperatures are greater than 30 degrees
38
When are heat-pain receptors stimulated?
- at temperatures above 45 degrees
39
When are cold receptors stimulated?
- at temperatures less than 45 degrees
40
When are cold-pain receptors stimulated?
- stimulated at temperatures less than 15 degrees
41
How does thermal detection occur?
- it could occur through changes in the metabolic rates of receptor cells
- or changes in membrane permeability
42
Cold and warm receptors adapt rapidly, what does this mean?
- thermal senses respond to changes in temperature rather than steady states of temperature
43
What is the fourth somatic sense?
- pain
44
Somatosensory Cortex summary:
- somatic senses don’t have a part of the brain that deals with them all separately
- organised into tissue location
- the more sensitive the body part, the greater the area of the cortex allocated
- the more sensitive the body part, the greater the number of sensory receptors located there, more brain tissue is required to deal with the amount of incoming data
45
What does communication with the somatosensory cortex give us?
- conscious awareness of somatic sensations
46
What are somesthetic projection pathways?
- the neuronal pathways which carry somatic signals to the parietal lobe of the cerebral cortex
47
Where do somatic senses starting in the head travel to?
- travel via the trigeminal nerve
- to the somatosensory cortex allocated
48
Where do somatic senses travelling from areas below the head travel to?
- signals travel via spinothalamic tracts
- signals pass up the spinal cord
- into the brainstem, via spinothalamic tracts
- that cross over the spinal cord
- the cortex receives sensory information from the opposite side of the body
49
What do dorsal columns of the spinal cord do?
- carry proprioceptive signals and the sensation of fine touch
