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✅Sensory Receptors Flashcards

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1
Q

What are sensory receptors?

A

Specialized cells or cell processes that provide the CNS with information (stimuli) about conditions inside or outside the body.

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2
Q

What does Activation of a sensory receptor by an adequate stimulus result in?

A

depolarization or graded potentials that trigger nerve impulses along the afferent fibres coursing to the CNS

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3
Q

What is sensation?

A

The arriving information

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4
Q

What is perception?

A

The conscious awareness of a sensation

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5
Q

What are the two classes of sensory receptors?

A

Special senses

General sensor receptors

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6
Q

Describe special senses

A

provided by receptors that are localised and more complex in structure. This information is distributed to specific areas of the cerebral cortex and to centres throughout the brain stem

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7
Q

What are the four special senses?

A

Hearing and balance- ear- cochlea & labyrinth
Smell - nose - olfactory receptors
Taste - tongue - gustatory receptors
Vision- eye - photoreceptors

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8
Q

Describe general sensor receptors

A

widely distributed, simple in structure. Some of the information they send to the CNS reaches the primary sensory cortex and our conscious awareness.

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9
Q

What are the four general sensor receptors?

A
  1. Nociceptors (pain)
  2. Thermoreceptors (temperature)
  3. Mechanoreceptors (physical distortion)
  4. Chemoreceptors (chemical concentration)
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10
Q

What are the 3 functional categories of the general senses?

A

Exteroceptors
Proprioceptors
Interoceptors

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11
Q

What do exteroceptors provide?

A

provideinformationaboutexternal environment (touch, pressure, vibration, pain, temperature, special sense receptors)

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12
Q

What do proprioceptors provide?

A

provide information about body position and movement by monitoring the degree of stretch

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13
Q

What do interoceptors provide?

A

provide information about internal systems (sensitive to chemical changes, tissue stretch and temperature changes)

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14
Q

What do guard and down hair follicles contain?

A

Guard hair (G-hair) and down hair (D-hair) follicles contain nerve endings that form a circumferential array of unmyelinated nerve terminals derived from myelinated axons.

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15
Q

Describe g-hair and d-hair

A

These receptors are rapidly adapting (RA), low threshold (LT) afferents and detect light touch

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16
Q

Describe pacinian corpuscles

A

have the typical structure of an encapsulated receptor. They are RA LTMs that allow perception of distant events through transmitted vibrations

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17
Q

Describe merkel cell-neuritis complexes

A

lie at the base of the epidermis and are formed of clusters of 50–70 cells connected to terminals of a myelinated Aβ axon. They function as slowly adapting (SA) LTMs and are responsible for form and texture perceptions

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18
Q

Describe ruffini corpuscles

A

lie in the dermis, with the distinct outer capsule surrounding a fluid- filled capsule space. They are SA cutaneous mechanoreceptors and contribute to the perception of object motion

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19
Q

What are C-fibre LTM?

A

Free nerve endings and unmyelinated receptors terminate in the subepidermal corium

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20
Q

Describe C-fibre LTMs

A

respond to innocuous tactile stimulation and signal pleasant stimulation in affiliative social body contact in humans. The perception of painful touch is initiated by high-threshold (HT) C-fibre and Aδ nerve endings (g), which can be mechanosensitive or polymodal in nature

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21
Q

What are the three types of cutaneous afferents?

A

Type Aβ
Type Aδ
Type C

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22
Q

What is Type Aβ?

A

Various rapidly and slowly adapting mechanoreceptors

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23
Q

What is Type Aδ?

A

Pain,temp, certain hair receptors

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24
Q

What is type C?

A

Unmyelinated (pain)

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25
What can muscle spindles be thought as?
Length detectors
26
What are the two groups of muscle spindles?
Group IA: Velocity + direction Group II: Sustained, static position
27
What can golgi tendons be thought of?
Force detectors
28
What is Group Ib (golgi)
Branched in collagen fibres to form tendons
29
What are the two somatic efferents?
Alpha motoneurons | Gamma motoneurons
30
What are alpha motoneurons?
Large diameter Type A large anterior horn cells/motoneurones innervate skeletal muscle
31
What are gamma motoneurons?
Small diameter Type A axons innervating intrafusal muscle fibres. Peripheral Nerves are classified according to conduction velocity/fibre diameter
32
Diameter of afferent fibres innervating muscle have a different distribution from what?
Those innervating the skin
33
How are the muscle afferents classified?
``` Group I (Aα) large myelinated (proprioceptors) Group II (Aβ) small myelinated (proprioceptors) Group III (Aδ) smallest myelinated (proprioceptors/pain) Group IV (C) unmyelinated (pain) ```
34
What to the receptive fields of three primary sensory neurons do?
Overlap
35
What does the second sensory neuron have?
A large receptive field
36
What do the primary sensor neurons do?
Converge on one secondary sensory neuron
37
What is the somatic sensory pathway for the right side of the body?
Receptors for discriminative touch, stereognosis, proprioception, weight discrimination and vibration First order neuron Nucleus gracilis Medial lemniscus Thalamus
38
What is the somatic sensory pathway for the left side of the body?
Spinal nerve Posterior column: fasciculus cuneatus, fasciculus gracilis Nucleus cuneatus Second order neuron Third order neuron Primary somatosensory area of cerebral cortex
39
What are the steps of the sensory pathway?
1- pain, temperature and coarse touch cross the midline in the spinal cord 2- fine touch, vibration and propriocption pathways cross the midline in the medulla 3. Sensory pathways synapse in the thalamus 4. Sensations are perceived in the primary somatic sensory cortex
40
What does the CNS receive input from?
A large number of sensory receptors
41
What do somatic motor neurons contract?
Voluntary skeletal muscles
42
What do autonomic motor neurons (sympathetic) relax?
Involuntary muscles around many internal organs ; accelerates heart
43
What do autonomic motor neurons (parasympathetic) contract?
Involuntary muscles around many internal organs; slows heart
44
What do somatic sensory neurons control?
Skin and pain sensors
45
What do visceral sensory neurons control?
Receptors in internal organs
46
Where do all sensory and motor neurons go? (PNS)
Spinal cord
47
Where do all special senses (CNS) go?
Brain
48
What is the language of the CNS?
electric signals, each of the various types of receptor cells must convert, or transduce, its sensory input into an electric signal.
49
Structures with sensory receptors provide selectivity to what?
electric signals, each of the various types of receptor cells must convert, or transduce, its sensory input into an electric signal.
50
What is the pathway of the electric signals? (Radio)
``` External signal Receptor Transducer Amplifier Response ```
51
What is the pathway From stimulus to frequency modulated AP output?
``` Stimulus Structural change in membrane Conductance change Receptor change Receptor current Receptor potential Modulated impulse frequency in receptor cell axon/ modulated transmitter release from receptor cell Modulated impulse frequency in 2nd order neuron ```
52
An adequate stimulus will open channels where?
at the receptor, resulting in an inward flux of Na+ (in most cases) and depolarisation (a receptor potential).
53
A receptor potential is a type of what?
graded potential: The strongest the stimulus, the greater the graded potential. They have no refractory period so sustained contraction is possible
54
What is the pathway of an adequate stimulus?
1- reception n 2- transduction 3- transmission 4- perception
55
Sensory neurones transform what?
A physical stimulus into electrical activity
56
What are the steps of sensory neurone transformation?
1- receptor potential 2- trigger action 3- action potential 4- output
57
What is The different responses of different receptors to a similar stimuli is called?
Adaption
58
Describe tonic receptors
o Always active o Show little peripheral adaptation o Slow-adapting receptors o Remind you of an injury long after the initial damage has occurred. o Examples: pain receptors, joint capsules and muscle spindles.
59
In tonic receptors, what happens when the stimulus increases or decreases?
The rate of action potential generation changes accordingly
60
What do tonic receptors generate?
Action potentials at a frequency that reflects the background level of stimulation.
61
Describe Phasic receptors
o Normally inactive o Become active for a short time whenever a change occurs o Provide information about the intensity and rate of change of a stimulus o Fast-adapting receptors. o Example: Pacinian corpuscle.
62
When do phasic receptors become active for a short period of time?
In response to a change in the conditions they are monitoring
63
How do tonic receptors respond to a stimulus?
For the duration of a stimulus
64
How do phasic receptors respond to stimuli?
They rapidly adapt to a constant stimulus and turn off. They fire once more when the stimulus is turned off
65
What do local anaesthetic block and how?
Action potential propagation by acting on NA+ channels
66
In what order does conduction block occur?
1. Small myelinated axons (pain) | 2. Non-myelinated axons 3.Large myelinated axons (motor and sensory
67
What is the order of block?
Pain>Temp>Touch>Proprioception & Motor
68
What effects are in reverse order?
Pressure block Electrical stimulation largest diameter axons blocked by pressure first largest diameter axons activated at lower currents than smaller axons

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