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Anatomy > ✅Sensory Receptors > Flashcards

✅Sensory Receptors Flashcards

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
Q

What can muscle spindles be thought as?

A

Length detectors

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26
Q

What are the two groups of muscle spindles?

A

Group IA: Velocity + direction Group II: Sustained, static position

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27
Q

What can golgi tendons be thought of?

A

Force detectors

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28
Q

What is Group Ib (golgi)

A

Branched in collagen fibres to form tendons

29
Q

What are the two somatic efferents?

A

Alpha motoneurons

Gamma motoneurons

30
Q

What are alpha motoneurons?

A

Large diameter Type A large anterior horn cells/motoneurones innervate skeletal muscle

31
Q

What are gamma motoneurons?

A

Small diameter Type A axons innervating intrafusal muscle fibres. Peripheral Nerves are classified according to conduction velocity/fibre diameter

32
Q

Diameter of afferent fibres innervating muscle have a different distribution from what?

A

Those innervating the skin

33
Q

How are the muscle afferents classified?

A 
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
Q

What to the receptive fields of three primary sensory neurons do?

A

Overlap

35
Q

What does the second sensory neuron have?

A

A large receptive field

36
Q

What do the primary sensor neurons do?

A

Converge on one secondary sensory neuron

37
Q

What is the somatic sensory pathway for the right side of the body?

A

Receptors for discriminative touch, stereognosis, proprioception, weight discrimination and vibration

First order neuron

Nucleus gracilis

Medial lemniscus

Thalamus

38
Q

What is the somatic sensory pathway for the left side of the body?

A

Spinal nerve

Posterior column: fasciculus cuneatus, fasciculus gracilis

Nucleus cuneatus

Second order neuron

Third order neuron

Primary somatosensory area of cerebral cortex

39
Q

What are the steps of the sensory pathway?

A

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

  1. Sensory pathways synapse in the thalamus
  2. Sensations are perceived in the primary somatic sensory cortex
40
Q

What does the CNS receive input from?

A

A large number of sensory receptors

41
Q

What do somatic motor neurons contract?

A

Voluntary skeletal muscles

42
Q

What do autonomic motor neurons (sympathetic) relax?

A

Involuntary muscles around many internal organs ; accelerates heart

43
Q

What do autonomic motor neurons (parasympathetic) contract?

A

Involuntary muscles around many internal organs; slows heart

44
Q

What do somatic sensory neurons control?

A

Skin and pain sensors

45
Q

What do visceral sensory neurons control?

A

Receptors in internal organs

46
Q

Where do all sensory and motor neurons go? (PNS)

A

Spinal cord

47
Q

Where do all special senses (CNS) go?

A

Brain

48
Q

What is the language of the CNS?

A

electric signals, each of the various types of receptor cells must convert, or transduce, its sensory input into an electric signal.

49
Q

Structures with sensory receptors provide selectivity to what?

A

electric signals, each of the various types of receptor cells must convert, or transduce, its sensory input into an electric signal.

50
Q

What is the pathway of the electric signals? (Radio)

A 
External signal 
Receptor 
Transducer 
Amplifier 
Response
51
Q

What is the pathway From stimulus to frequency modulated AP output?

A 
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
Q

An adequate stimulus will open channels where?

A

at the receptor, resulting in an inward flux of Na+ (in most cases) and depolarisation (a receptor potential).

53
Q

A receptor potential is a type of what?

A

graded potential: The strongest the stimulus, the greater the graded potential. They have no refractory period so sustained contraction is possible

54
Q

What is the pathway of an adequate stimulus?

A

1- reception n
2- transduction
3- transmission
4- perception

55
Q

Sensory neurones transform what?

A

A physical stimulus into electrical activity

56
Q

What are the steps of sensory neurone transformation?

A

1- receptor potential
2- trigger action
3- action potential
4- output

57
Q

What is The different responses of different receptors to a similar stimuli is called?

A

Adaption

58
Q

Describe tonic receptors

A

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
Q

In tonic receptors, what happens when the stimulus increases or decreases?

A

The rate of action potential generation changes accordingly

60
Q

What do tonic receptors generate?

A

Action potentials at a frequency that reflects the background level of stimulation.

61
Q

Describe Phasic receptors

A

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
Q

When do phasic receptors become active for a short period of time?

A

In response to a change in the conditions they are monitoring

63
Q

How do tonic receptors respond to a stimulus?

A

For the duration of a stimulus

64
Q

How do phasic receptors respond to stimuli?

A

They rapidly adapt to a constant stimulus and turn off. They fire once more when the stimulus is turned off

65
Q

What do local anaesthetic block and how?

A

Action potential propagation by acting on NA+ channels

66
Q

In what order does conduction block occur?

A
  1. Small myelinated axons (pain)

2. Non-myelinated axons
3.Large myelinated axons (motor and sensory

67
Q

What is the order of block?

A

Pain>Temp>Touch>Proprioception & Motor

68
Q

What effects are in reverse order?

A

Pressure block
Electrical stimulation

largest diameter axons blocked by pressure first
largest diameter axons activated at lower currents than smaller axons

Anatomy (20 decks)

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