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Medicine Year 1 - Semester 2 - Part 1 > Sensory Receptors > Flashcards

Sensory Receptors Flashcards

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1
Q

List the main classes of sensory receptor found in the body

A

Mechanoreceptors - tactile and position sensations

Thermoreceptors - detect heat and cold

Pain receptors - detect damage to the tissue

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2
Q

What is glabrous skin ?

A

Skin that doesn’t have hair on it

e.g. palm of hand / sole of foot

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3
Q

What is hairy skin ?

A

Skin that has hair on it

Touch from receptors in skin surface

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4
Q

Name some structures found in the dermis

A

Pacinian corpuscle
Meissners corpuscle
Ruffini’s ending
Hair follicle receptor
Free nerve endings

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5
Q

What do cutaneous mechanoreceptors respond to ?

A

Touch from receptors in skin surface

Pressure from receptors in deep tissue

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6
Q

Spray endings

A

Ruffini’s ending (specialised nerve endings)

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7
Q

Encapsulated endings

A

Pacinian corpuscles (receptor cells around nerve)

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8
Q

Muscle endings

A

Muscle spindles
Golgi tendon organs

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9
Q

Describe Pacini’s corpuscle

A

Largest mechanoreceptor in the skin (2mm long)

Onion like encapsulation of nerve ending

Found in deep layers of the dermis

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10
Q

Explain the structure of Pacini’s corpuscle

A

1st part is unmyelinated
2nd part is myelinated (as it leaves receptor cell)

ABeta fibres (quick) - glabrous & hairy skin

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11
Q

Function of Pacini’s corpuscle

A

Detects high frequency (40-500Hz) vibration

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12
Q

State some features of Pacini’s corpuscle

A

Rapidly adapting due to a slick viscous fluid between layers.

Has a low activation threshold (i.e. it is sensitive)

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13
Q

Describe Meissner’s corpuscle

A

Encapsulated nerve endings similar to Pacini’s but MUCH smaller

Found between dermal papillae

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14
Q

Explain the structure of Meissner’s corpuscle

A

Stacks of discs interspersed with nerve branch endings

ABeta Fibres (quick) - Glabrous skin types

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15
Q

Function of Meissner’s corpuscle

A

Detects touch, flutter and LOW frequency vibration
(2-40Hz)

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16
Q

State some features of Meissner’s corpuscle

A

Rapidly adapting - low activation threshold
(sensitive )

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17
Q

Describe Merkel’s discs

A

Non -encapsulated nerve endings

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18
Q

Explain the structure of Merkel’s discs

A

Consist of a specialised epithelial cell + nerve fibre

ABeta fibres - all skin types

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19
Q

Function of Merkel’s discs

A

Found just under the skin surface

e.g. fingertips : good discrimination :

  • Detects static touch
  • Light pressure

Work with Meissner’s corpuscles to help determine texture.

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20
Q

State some features of Merkel’s discs

A

Slowly adapting - low activation threshold (sensitive)

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21
Q

Describe hair follicles

A

Embedded in the skin

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22
Q

Function of hair follicles

A

Detect muscular movements of the hair (erector muscle) and external displacements of hair

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23
Q

What are hair follicles innervated by ?

A

Innervated by nerve endings wrapped around the follicle.

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24
Q

Describe Ruffini corpuscle

A

Encapsulated nerve endings

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25
Function of Ruffini corpuscle
Responds to skin stretch and is located in the deeper layers of the skin as well as tendons and ligaments
26
Structure of Ruffini corpuscle
Nerve endings weave between collagen fibres which activate the nerve when they are pulled longitudinally. ABeta fibres - all skin, but especially abundant in hands and fingers as well as sole of feet
27
Features of Ruffini corpuscle
Slow adapting - low threshold activation (sensitive)
28
Skeletal muscle receptor types
Muscle spindles Golgi Tendon organs
29
What are muscle spindles ?
Main proprioceptors that provide infrmaoin about the state of musculature.
30
Where are muscle spindles found ?
Muscle spindles lie within muscles in parallel with skeletal muscle fibres. Particularly numerous in fine motor control muscles (e.g. eyes, hands)
31
What are muscle spindles innervated by ?
Innervated by gamma-motoneurons (efferents) and group Ia and II afferent fibres
32
What are Golgi tendon organs ?
Main proprioceptors that provide information about the state of musculature.
33
Where are Golgi Tendons Organs found ?
Liw within tendons in a series with contractile fibres.
34
How do Golgi tendons act ?
Respond to a degree of tension within the muscle. Group Ib afferent fibres relay information to CNS (particularly spinal cord and cerebellum)
35
What is a generator potential ?
The potential caused by a stimulus to a nerve ending. Generates action potentials in a sensory neuron.
36
What is a receptor potential ?
Potential causes by a stimulus to a receptor cell. Affects the amount of neurotransmitter released by a receptor cell onto sensory neuron.
37
What can a receptor potential be caused by ?
Mechanical deformation of receptor Chemical application to membrane Temperature change of membrane Effects of electromagnetic radiation
38
Mechanical deformation of receptor
[causes a receptor potential] Stretch receptor membrane and open ion channels
39
Chemical application to membrane
[causes a receptor potential] Opens ion channels
40
Temperature change of membrane
[causes a receptor potential] Changes the permeability of membrane
41
Effects of electrochemical radiation
[causes a receptor potential] e.g. light on retinal receptor
42
Explain receptor potential generation in a Pacini Corpuscle
Tip unmyelinated - nerve fibre myelinated before leaving corpuscle Compression anywhere on outside of corpuscle elongates, indents/deforms central fibre Receptor potential induces local current flow (Na+ current) which spreads along the nerve fibre At the 1st Node of Ranvier local current flow depolarises fibre membrane at this node, which sets off action potentials to CNS
43
Function of the 1st Node of Ranvier in the Pacini Corpuscle
At the 1st Node of Ranvier local current flow depolarises fibre membrane at this node, which sets off action potentials to CNS.
44
Describe the relationship between receptor potential and action potential generation
When receptor potential rises above the threshold in nerve fibre - action potentials fire. The more the receptor potential rises above the threshold level, the greater the action potential frequency.
45
Describe how the receptor potential rises ?
Amplitude of receptor potential increases rapidly at first, then less rapidly at high stimulus strength.
46
How is action potential related to stimulus size ?
APs generated in a sensory nerve at a frequency directly related to stimulus size.
47
Describe adaptation of sensory receptors
Some sensory receptors adapt rapidly to constant stimulus so their generator potentials do too.
48
What are tonic receptors ?
Slowly adapting receptors which detect continuous stimulus strength.
49
What are rate/movement/phasic receptors ?
Rapidly adapting receptors which detect a change in stimulus strength.
50
C fibres
Unmyelinated Slow Sensation of dull pain (generalised)
51
A Delta
Myelinated Fast Sharp localised pain
52
State some myelinated nerve fibre types
A alpha (Ia) A alpha (Ib) A beta (II) A gamma (II) A delta (III) B
53
State the order of magnitude of the axon diameters (from largest to smallest)
A alpha (Ia) A alpha (Ib) A beta (II) A gamma (II) A delta (III) B C (IV)
54
State the order of magnitude of axon conduction velocities (from largest to smallest)
A alpha (Ia) A alpha (Ib) A beta (II) : 35-75 A gamma (II) : 15-30 A delta (III) : 5-30 B : 3-15 C (IV)
55
State the quickest nerve fibres in the body
A alpha 80-120 m/s
56
State the widest nerve fibres in the body
A alpha 12-20
57
State the slowest nerve fibres in the body
C nerve fibres 0.5 - 2
58
State the thinnest nerve fibres in the body
C nerve fibres 0.2 - 1.5
59
Describe A alpha (Ia)
Somatic motor (Annulospiral endings of muscle spindle)
60
Describe A alpha (Ib)
Golgi tendon organs
61
Describe A beta (II)
Cutaneous tactile receptors (touch, pressure) Flower spray endings of muscle spindle
62
Describe A gamma (II)
Motor to spindle
63
Describe A delta (III)
Crude touch Temperature Pain sensation
64
Describe B
Preganglonic autonomic
65
Describe C (IV)
Pain and temperature sensation Postganglionic sympathetic
66
What is precisions localisation of a particular stimulus determined by ?
Size of individual nerve fibre receptive field Density of sensory units Amount of overlap in nearby receptive fields
67
Describe receptive field distribution
Higher the resolution, higher the number of modalities for a given situation, the better the understanding.
68
Describe the receptive field of Pacini's corpuscle
Pacini's corpuscle have broad receptive field
69
Describe the receptive field of Meissner's corpuscle
Meissner's corpuscle and Merkel's discs are very small Note : Small receptive fields allow high spatial resolution.
70
What is 2 point discrimination ?
Horizontal bars represent minimum distance at which 2 points can be perceived at a distinct.
71
How does 2 point discrimination work ?
It is a result of receptive field size and receptor density in an area. Does NOT represent sensitivity to stimulus.
72
What is the function of lateral inhibition ?
Aids in enabling localisation of stimulus
73
Where does the information from touch receptors go to ?
The dorsal column which exists at all levels of the spinal cord
74
Describe the spinothalamic tract
Information crosses over at the spinal cord level (e.g. pain), and goes up the spinothalamic tract to the opposite side of the brain. You can use this information to determine where lesion may occur in the spinal cord.
75
What is the somatosensory cortex ?
Sensory information passes through the thalamus to the primary sensory cortex. Sensory information projected in a topographical manor to this area. Areas of higher discrimination/senses having a larger proportion of the space.
76
Where is the somatosensory cortex located ?
Located in a strip posterior to the post central sulcus of the brain

Medicine Year 1 - Semester 2 - Part 1 (51 decks)

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