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Semester 2 Year 1 > Sensory Receptors > Flashcards

Sensory Receptors Flashcards

1
Q

What are the five basic types of sensory receptor?

A 
Mechanoreceptors
Thermoreceptors 
Nociceptors (pain receptors) 
Electromagnetic receptors (rods and cones) 
Chemoreceptor
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2
Q

What do mechanoreceptors do?

A

detect mechanical compression / stretching of the receptor or tissue

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3
Q

What do thermoreceptors do?

A

detect changes in temperature (cold and warmth receptors)

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4
Q

What do nociceptors (pain receptors) do? (I’ll give you three guesses)

A

detect physical or chemical damage of tissues

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5
Q

What do electromagnetic receptors (rods and cones) do?

A

detect light on retina of eye

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6
Q

What do chemoreceptors do?

A

Transduces a chemical substance (endogenous or induced) to generate a biological signal
e.g., taste, smell, arterial oxygen level, osmolality, blood carbon dioxide

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7
Q

What category of receptor provide the tactile senses of the skin (epidermis and dermis)?

A

cutaneous mechanoreceptors

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8
Q

What types of cutaneous mechanoreceptors are there in the skin?

A 
Free nerve endings
Expanded tip endings
    - Merkel’s discs
Spray endings
Ruffini’s endings
Encapsulated endings
    - Meissner’s corpuscles
Hair end-organs
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9
Q

What types of cutaneous mechanoreceptors are there in the deep tissue that provide deep tissue senses?

A 
Free nerve endings
Expanded tip endings
Spray endings
    - Ruffini’s endings
Encapsulated endings
    - Pacinian corpuscles
Muscle endings
    - Muscle spindles
    - Golgi tendon organs
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10
Q

What two corpuscles act as touch receptors?

A

Pacini’s corpuscle

Meissner’s corpuscle

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11
Q

Describe Pacini’s corpuscle

A
  • Pacini’s corpuscle
  • largest mechanoreceptor - 2mm long
  • Onion like encapsulation of nerve endings
  • Found in deep layers of dermis
  • Detects high frequency (40-500Hz) vibration
  • Aβ fibres - glabrous & hairy skin
  • Rapidly adapting due to a slick viscous fluid between the layers
  • Has a low activation threshold i.e. is sensitive
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12
Q

Describe Meissner’s corpuscle

A
  • Encapsulated nerve endings similar to Pacini’s but much smaller
  • Stacks of discs interspersed with nerve branch endings
  • Found between dermal papillae
  • detects touch, flutter & low frequency vibration (2-40Hz)
  • Aβ fibres - glabrous skin types
  • Rapidly adapting - low activation threshold (sensitive)
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13
Q

What receptors act as pressure/touch receptors?

A

Merkel disks

Hair follicles

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14
Q

Describe Merkel discs

A
  • Non-encapsulated nerve endings
  • Consist of a specialised epithelial cell + nerve fibre
  • Found just under the skin surface in for example the finger tips – good discrimination - detects static touch and light pressure
  • Aβ fibres - all skin types
  • Slowly adapting - low activation threshold (sensitive)
  • Work with Meissner’s corpuscles to help determine texture
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15
Q

Describe hair follicles

A
  • Embedded in skin – innervated by nerve ending wrapped around its follicle
  • detect muscular movements of the hair (erector muscle) and external displacements of hair
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16
Q

Name a stretch receptor?

A

The Ruffini corpuscle

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17
Q

Describe the Ruffini corpuscle

A
  • Encapsulated nerve ending
  • Nerve ending weave between collagen fibres which activate the nerve when they are pulled longitudinally
  • responds to skin stretch and is located in the deeper layers of the skin as well as tendons and ligaments
  • Aβ fibres - all skin types but especially abundant in hands and fingers as well as soles of feet
  • Slowly adapting - low threshold activation (sensitive)
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18
Q

What are muscle spindles?

A

Main proprioceptors that provide information about the state of musculature

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19
Q

Where do muscle spindles lie?

A

Muscle spindles lie within muscles in parallel with skeletal muscle fibres
Particularly numerous in fine motor control muscles (e.g. eyes, hands)

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20
Q

What are muscle spindles innervated by?

A

by y(gamma)-motoneurons (efferents) and group Ia and II afferent fibres

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21
Q

What is the difference between afferent and efferent neurons?

A

Afferent neurons are sensory neurons that carry nerve impulses from sensory stimuli towards the central nervous system and brain, while efferent neurons are motor neurons that carry neural impulses away from the central nervous system and towards muscles to cause movement

Afferent - sensory
Efferent - motor

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22
Q

What do the afferents and efferents do in muscle spindles

A

Afferents respond to muscle stretch while y(gamma)-efferent activity regulates the sensitivity of the spindle

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23
Q

What are Golgi tendon organs?

A

Main proprioceptors that provide information about the state of musculature
Respond to degree of tension within the muscle
Group Ib afferent fibres relay information to CNS (particularly spinal cord and cerebellum)

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24
Q

Where are Golgi tendon organs found?

A

Golgi tendon organs lie within tendons in series with contractile fibres

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25
Q

What is the difference between a generator potential and a receptor potential?

A

Generator potential refers to potential caused by a stimulus to a NERVE ENDING
Receptor potential refers to potential caused by stimulus to a RECEPTOR CELL

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26
Q

What does a generator potential do?

A

Generates action potentials in a sensory neuron

27
Q

What does a receptor potential do?

A

Affects amount of neurotransmitter released by receptor cell onto sensory neuron

28
Q

Discuss receptor potential generation in a pacini corpuscle?

A

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 nerve fibre

At 1st node of Ranvier local current flow depolarizes fiber membrane at this node, which sets off action potentials to CNS

29
Q

Discuss the relationships between receptor potential and action potential generation

A

When receptor potential (from receptor) rises above threshold in nerve fiber - action potentials fire

Amplitude of receptor potential increases rapidly at first then less rapidly at high stimulus strength

The more receptor potential rises above threshold level, the greater the action potential frequency

APs generated in a sensory nerve at a frequency directly related to stimulus size

_F_o_r_A_p_e_B_r_a_i_n
Receptor potential go up
Action potential happen more often
Should be calculable

30
Q

What happens to the generator potentials of sensory receptors that adapt more rapidly?

A

Their generator potential adapts more quickly too: Impulses per second will rapidly decrease after initial stimulus

31
Q

What cutaneous mechanoreceptor would respond to a light brush?

A

Hair follicles

32
Q

What cutaneous mechanoreceptor would respond to dynamic deformation?

A

Meissner corpsucle

33
Q

What cutaneous mechanoreceptor would respond to vibration?

A

Pacinian corpsucle

34
Q

What cutaneous mechanoreceptor would respond to indentation depth?

A

Merkel cell - neurite complex

35
Q

What cutaneous mechanoreceptor would respond to stretch?

A

Ruffini corpsucle

36
Q

What cutaneous mechanoreceptor would respond to touch?

A

C - fibre LTM (Low threshold mechanoreceptors)

37
Q

What cutaneous mechanoreceptor would respond to injurious forces?

A

Mechano-nociceptor

Polymodal nociceptor

38
Q

What are slowly adapting receptors that detect continuous stimulus strength called?

A

Tonic receptors

39
Q

What are rapidly adapting receptors that detect continuous stimulus strength called?

A

Rate receptors/movement receptors/phasic receptors

40
Q

What is the precision of localisation of a particular stimulus is determined by?

A

Size of individual nerve fibre receptive field

Density of sensory units

Amount of overlap in nearby receptive fields

41
Q

What is receptive field distribution?

A

Different sensory modalities used by brain to describe World around us

42
Q

Why is receptive field distribution important?

A

Quality of information relates directly to ability to comprehend them
Higher the resolution, higher the number of modalities for a given situation, the better the understanding

____
Sometimes we gotta know all about shit

43
Q

Give an example of two cutaneous mechanoreceptors with different receptive field distribution?

A

Pacini’s corpuscles and Meissner’s corpuscles are both sensitive, but have different receptive field sizes

- Pacini corpuscles have broad receptive field
- Meissner’s corpuscles and Merkel’s disks are very small
44
Q

What is the benefit of a small receptive field distribution?

A

Small receptive fields allow high spatial resolution

45
Q

What does two point discrimination describe?

A

minimum distance at which two points can be perceived as distinct

46
Q

What is two point discrimination a result of?

A

receptive field size and receptor density in area

47
Q

what does two point discrimination not represent?

A

sensitivity to stimulus

48
Q

What is lateral inhibition?

A

Information from afferent neurons whose receptors are at edge of a stimulus are strongly inhibited compared to information from the stimulus’ centre

49
Q

What does lateral inhibition aid?

A

Aids in enabling localisation of stimulus

50
Q

What is the dorsal column–medial lemniscus pathway?

A

A sensory pathway of the central nervous system that conveys sensations of fine touch, vibration, two-point discrimination, and proprioception (position) from the skin and joints.

51
Q

Where is the dorsal column?

A

Dorsal column (Fasciculus gracilis) exists at all levels of the spinal cord

52
Q

What are the three groupings of neurons present in the dorsal column–medial lemniscus pathway?

A

first-order neurons (neuron I)
second-order neurons (neuron II)
third-order neurons (neuron III)

53
Q

What are the first order neurons (neuron I)the dorsal column/medial lemniscus?

A

Sensory neurons located in the dorsal root ganglia represented from lower (T6-S5) and upper limbs (C1-T5)

54
Q

What are the second order neurons (neuron II)the dorsal column/medial lemniscus?

A

Second-order neurons (neuron II) in the nucleus gracilis and cuneatus cross in the midline to form the medial lemniscus (and so make contact with neuron I), ascends through medulla, pons & midbrain to thalamus

55
Q

What are the third order neurons (neuron III) in the dorsal column/medial lemniscus?

A

Axons of third-order neurons (neuron III) in thalamus travel in the internal capsule and terminate in the somatosensory cerebral cortex

56
Q

Where do second order neurons (neuron II) terminate in the dorsal column/medial lemniscus?

A

Terminates in the contralateral ventral posterolateral nucleus of the thalamus

57
Q

What do first order neurons form in the direct spinothalamic tract?

A

dorsal root ganglion cells (neuron I) synapse with neurons of nucleus proprius

58
Q

How do the second order neurons ascend the spine in the direct spinothalamic tract?

A

Second-order neurons (neuron II) cross via the anterior white commissure & enter contralateral white matter
Ascend in spinothalamic tract

59
Q

Where are the third order neurons (neuron III) in the direct spinothalamic tract?

A

Third-order neurons (neuron III) located in the ventral posterolateral nucleus of the thalamus
Axons of third-order neurons project to primary sensory cortex

60
Q

How does the somatosensory cortex receive sensory information?

A

Sensory information passes through the thalamus to the primary sensory cortex

61
Q

Where is the somatosensory cortex located?

A

In a strip posterior to the post central sulcus of the brain

62
Q

How is sensory information projected in the somatosensory cortex?

A

in a topographical manner to this area

63
Q

How is the somatosensory cortex organised?

A

Areas of higher discrimination/senses having a larger proportion of the space

Semester 2 Year 1 (82 decks)

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