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Year 1- Principles of Normal Function (FOM) > Sensory Receptors > Flashcards

Sensory Receptors Flashcards

1
Q

What is the function of sensory receptors?

A

They inform your brain about external and internal environment.

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2
Q

What do sensory receptors turn stimuli into?

A

The frequency of action potentials.

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3
Q

Name three tyes of sensory receptor.

A

Mechanoreceptors, proprioceptors and nociceptors.

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4
Q

Describe mechanoreceptors.

A

Stimulated by mechanical stimuli - pressure, stretch, deformation - give us skin sensations of touch and pressure

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5
Q

What are proprioceptors?

A

Mechanoreceptors in joints and muscles. They signal information about body or limb position

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6
Q

Describe nociceptors.

A

Respond to painful stimuli

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7
Q

What receptors are found in the nose and tongue?

A

Chemical receptors.

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8
Q

What receptors are found in the ears?

A

Sound and position receptors

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9
Q

What receptors are found in the eyes?

A

Light receptors

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10
Q

What receptors are found in the skin?

A

Touch, pain, temperature and pressure receptors.

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11
Q

What is sensory modality?

A

The stimulus type that activates a particular receptor: eg. touch, pressure, joint angle, pain

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12
Q

What is an adequate stimulus?

A

The form of energy to which a receptor normally responds.

Minimum amount of energy required.

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13
Q

What does sensory receptor transduction involve?

A

The opening and closing of ion channels.

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14
Q

What is receptor potential/ generator potential?

A

When an adequate stimulus causes a graded membrane potential change (only a few mV) –

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15
Q

What is the adequate stimulus in cutaneous mechanoreceptors and proprioceptors?

A

Membrane deformation.

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16
Q

What does membrane deformation activate?

A

Activates stretch-sensitive ion channels – so ions flow across the membrane and change the membrane potential locally.

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17
Q

When do action potentials start firing?

A

When depolarisation reaches the area with voltage-gated ion channels (the first node of Ranvier)

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18
Q

How does stimulus intensity impact the production of action potentials?

A

Lowest stimuli intensity=no action potentials
Highest stimuli intensity= most action potentials

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19
Q

In a sensory nerve, a larger stimulus…?

A

Causes a larger receptor potential and a higher frequency of action potentials (frequency coding of stimulus intensity).

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20
Q

The info from the receptors on the skin depends on what?

A

The properties of nerve endings and of accessory, non-neuronal structures

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21
Q

Why do nociceptors not adapt?

A

As they detect pain due to the free nerve endings, it is important not to ignore pain generated.

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22
Q

Describe the Pacinian corpuscle.

A

Mechanoreceptor
It comprises a myelinated nerve with a naked nerve ending
enclosed by a connective tissue capsule of layered membrane lamellae
each layer is separated by fluid : (a bit like a spongy onion)

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23
Q

How does the Pacinian corpuscle respond?

A
  1. A mechanical stimulus deforms the capsule and the nerve ending
  2. This stretches the nerve ending and opens ion channels
  3. Na+ influx causes local depolarisation - a receptor/generator potential
  4. APs are generated and fire where myelination begins (because regenerative Na+ channels cluster at nodes of Ranvier)
24
Q

What component of sensory receptors mean that you can feel an itch?

A

Receptive fields

->a somatic sensory neuron is activated by stimuli in a specific area called the receptive field
A touch-sensitive neuron in the skin responds to pressure within a defined receptive field (area of skin)

24
Q

What is the Pacinian corpsule?

A

Sensory receptors for vibration and deep pressure and are essential for proprioception

25
Q

Our ability to tell 2 points apart on the skin is measured by the…?

A

Two point discrimination test.

26
Q

The ability for the two point discrimination test depnds on two things. Name them.

A

Receptive field size
Neuronal convergence.

27
Q

What is the two point discrimination?

A

Two-point discrimination is the ability to discern that two nearby objects touching the skin are truly two distinct points, not one.

28
Q

WWhat is transduction?

A

Change from external energy into internal action potentials in known as transduction

29
Q

What does the Pancinian corpusle sense?

A

Senses vibrations

30
Q

What are proprioceptors?

A

Mechanoreceptors that signal body or limb position

31
Q

Name three proprioceptors.

A

Muscle spindles
Golgi tendon organs
Joint receptors.

32
Q

Name the three functions of receptors.

A
  1. Control voluntary movement
  2. Generate spinal reflex movement
  3. they provide sensory information to perceive limb and body position and movement in space = kinaesthesia.
33
Q

What do muscle spindles monitor?

A

Monitor muscle length and rate of change of muscle length - they control reflexes and voluntary movements..

34
Q

What do Golgi tendon organs monitor?

A

Tension on tendons

35
Q

Discuss lateral inhibition.

A

Receptors at edge of a stimulus are more strongly inhibited than receptors near centre
enhances the contrast between relevant and irrelevant information.

36
Q

Briefly describe the pathway of info from the body to the brain.

A

Info relayed by spinal cord -> thalamus -> somatosensory cortex

37
Q

There are a few specialized muscle fibres have their own sensory and motor innervation…what are they called?

A

Intrafusal muscle fibres.

38
Q

Name the two types of intrafusal fibre.

A

Nuclear bag fibres and nuclear chain fibres

39
Q

Describe the structure of nuclear bag fibres and nuclear chain fibres.

A

Nuclear bag fibres- bag shaped w nuclei collected together
Nuclear chain fibres- nuclei lined up in a chain

40
Q

Muscle fibres are multinucleated..what does this mean?

A

More than two nuclei.

41
Q

What motor neurons have a smaller diameter- gamma or alpha?

A

Gamma

42
Q

How does spindle information contribute to perception of body position and movement?

A

Joint movement is organized by groups of muscles working in opposition ie. agonists and antagonists (eg. biceps and triceps)
When agonist contracts, antagonist relaxes and the joint moves

43
Q

Stretching the agonist joint…

Contracting the agonist joint…

A

…increases spinal discharge

…decreases spinal discharge

44
Q

Stretching the antagonist joint…

Contracting the antagonist joint…

A

…decreases spinal discharge

…increases spinal discharge

45
Q

How muscles develop tension?

A

Contracting to stretch the tendons as this stretches the nerve endings of the GTO and
initiates APs in the group 1b afferent fibre from the GTO (Golgi tendon organs).

46
Q

How do muscle spindles lie and how to Golgi tendon organs lie?

A

Muscle spindles- in parallel.
GTOs- in series.

47
Q

What is the significance of the gamma motor innervation to the contractile ends of muscle spindles?

A

Allows muscle fibres to change length and fire action potentials.

48
Q

What would happen if an Alpha motor neuron fired without gamma?

A
49
Q

What can joint receptors monitor?

A

Joint angle, rate of angular movement and tension on the joint

50
Q

Which are more contractile- intrafusal or extrafusal muscle fibres?

A

Extrafusal

51
Q

What kind of innervation can intrafusal muscle fibres provide?

A

Motor and sensory

52
Q

How is joint movement organised?

A

By groups of muscles working in opposition- when the agonist contracts, the antagonist relaxes and the joint moves :)

53
Q

Are tendons affected by passive stretch?

A

No as are inelastic

54
Q

How do muscles develop tension?

A

By contracting to stretch the tendons

Year 1- Principles of Normal Function (FOM) (21 decks)

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