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Science for shegs > Sensory receptors > Flashcards

Sensory receptors Flashcards

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1
Q

Sensory receptors are described as transducers, why?

A

Convert external energy to a number/frequency of AP

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2
Q

A certain amount of energy is needed to make a sensory receptor respond.

What is the term used to describe this?

A

Adequate stimulus

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3
Q

What is sensory modality used to describe?

A

The type of stimulus that the receptor responds to

ie touch, temperature etc

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4
Q

What are mechanoreceptors used for?

A

Stimulated by pressure, stretch, deformation

Used for hearing, balance, pain, blood pressure, touch etc

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5
Q

What is the name given to mechanoreceptors that are found in bones and joints, and signal the body about limb position?

A

Proprioceptors

proprioception - sense of bodily position

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6
Q

Nociceptors respond to what type of stimulus?

A

Pain, heat and tissue damage

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7
Q

Sensory receptors are often described as cutaneous. What does cutaneous mean?

A

Skin

These receptors sense stimuli acting on the skin

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8
Q

Cutaneous mechanoreceptors and proprioceptors sense stimulus using a specific type of ion channel. Describe what it is and how it works.

A

Stretch sensitive ion channels

Adequate stimulus causes membrane deformation ∴ ion channels open ∴ ion flow causes change to local membrane potential

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9
Q

Explain what is wrong with this statement.

An adequate stimulus causes graded potentials to travel along the receptor to the first node. At the first node, Voltage gated ion channels exist. Provided the depolarisation reaches the VG channel, action potentials will fire.

A

First part correct

However, APs will only fire if the depolarisation is strong enough to reach threshold

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10
Q

Aside from frequency of action potentials, what reflects the intensity of a stimulus?

A

Number of receptors activated per unit area

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11
Q

Free nerves are often wrapped around the roots of hair. These attach to what type of receptor, and what is the system used to sense?

A

Pacinian corpuscle

Senses vibrations

Nerves at hair root sense movement of hair

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12
Q

The Ruffini corpuscle is a type of sensory receptor, used to respond to what?

A

Stretches in the skin

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13
Q

Merkel receptors are present in the epidermis. What is their function?

A

Steady pressure

Texture

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14
Q

What type of receptors are used to detect ‘stroking and fluttering movements’?

A

Meissner’s courpuscles

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15
Q

True or false

All mechanoreceptors are designed so that if a stimulus persists, they basically ignore the stimulus unless there is a change.

A

False

Only some mechanoreceptors do this

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16
Q

What is adaption of mechanoreceptors?

A

Mechanoreceptors only responding to onset of stimulus

Then will only respond to change or a novel event

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17
Q

Why is it important that nociceptors do not show adaptation to stimulus?

A

Nociceptors respond to painful stimulus

Important not to ignore painful stimuli

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18
Q

Receptors can be categorised as rapidly adapting or slowly adapting.

Pacinian corpuscles and meissner’s corpuscles are classed as what type?

A

Rapidly adapting

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19
Q

Describe the structure of Pacinian corpuscles.

A

Capsule made of connective tissue

Layered membrane lamellae with fluid between

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20
Q

How does the pacinian corpuscle respond to stimulus?

A

Mechanical stimulus deforms capsule

Stretch ion channels opened ∴ Na+ flow

Depolarisation ∴ generator potential

If threshold, AP fired where the myelination begins

21
Q

Why does the structure of pacinian corpuscles allow rapid adaptation?

A

Stimulus = deformation due to vertical force

Redistribution of internal fluid dissipates force

Vertical force effectively gone ∴ ion channels close

No GP ∴ no AP ∴ no feeling

22
Q

In terms of the pacinian corpuscle, the non-neural component refers to what?

A

The CT capsule

Anything that isn’t the nerve

23
Q

Presynaptic neurons often exhibit neuronal convergence. Why is this useful in terms of summation?

A

Multiple sub-threshold stimuli can synapse onto a secondary neuron and cause APs

large receptive field

24
Q

What does lots of convergence and a large secondary receptive field indicate about the sensitivity of an area?

A

Insensitive

25
Q

What is the 2-point discrimination test?

A

Distance between points adjusted until two points can be felt, not one

26
Q

What is acuity?

A

The ability to locate a stimulus on the skin, and differentiate it from another closeby

27
Q

What is the relationship between neuronal convergence and acuity?

A

High convergence = low acuity

28
Q

In lateral inhibition, what happens to the surrounding sensory neurons to where the stimulus is applied?

A

Stimulated sensory neuron inhibits the surrounding neurons to stop them firing despite being slightly stimulated

29
Q

Why is it important that inhibitory interneurons use a different neurotransmitter from the other neurons?

A

Specific to inhibition

Otherwise signals would be confused

30
Q

Where does most lateral inhibition take place?

A

Spinal cord

31
Q

What do muscle spindles do?

A

Monitor muscle length and rate of change of muscle length

Reflexes + voluntary movements

32
Q

What organs are used to monitor the tension on tendons?

A

Golgi tendon organs

33
Q

What do joint receptors monitor?

A

Joint angle

Rate of angular movement

Tension on the joint

34
Q

Which receptors are involved with spinal cord reflexes?

A

Muscle spindles

Golgi tendon organs

35
Q

Where would you find intrafusal muscle fibres?

A

Muscle spindle

36
Q

The capsule encasing muscle spindles is made out of what tissue?

A

Connective tissue

37
Q

What is the difference between alpha and gamma neurones in terms of the muscle fibres they link to?

A

Alpha = extrafusal

Gamma = intrafusal

38
Q

In the muscle spindles, there are two types of nuclear fibres. What are they?

A

Nuclear bag fibre

Nuclear chain fibre

39
Q

Which is thicker, alpha axons or gamma axons?

A

Alpha

40
Q

What are annulospiral endings?

A

Primary endings from 1a afferent nerves wrap around the intrafusal fibres

41
Q

What is the arrangement of contractile sarcomeres in intrafusal fibres?

A

Sarcomeres contained in ends of intrafusal fibres

Not in centre

42
Q

What type of ion channels are in the type 1A afferents that surround the fibres in the muscle spindle?

A

Stretch sensitive

43
Q

Describe the relationship between the velocity of spindle stretching, and frequency of generated potentials.

A

Proportional

The faster the stretch - the higher the frequency of APs

44
Q

True or false

The difference between the initial length and final length of spindle informs about the muscle length.

A

True

45
Q

Example

How would the AP frequency look from the afferent neurones surrounding nuclear bag fibre during contraction, when compared to relaxed?

A

Frequency is lower when contracted

Less stretched ∴ lower frequency

46
Q

Describe what happens to the AP frequency in the neurones in the golgi tendon organs during contraction.

A

AP frequency increases with load

Tendons stretched more ∴ more APs

47
Q

What type of afferent neurones innervate tendons?

A

1B

48
Q

A muscle contracts but it’s length stays the same. What happens to the 1A and 1B neurones, in terms of Action potentials?

A

1B fires because tendons stretched

1A does not fire because muscle length unchanged

49
Q

Why is it important that gamma motoneurons fire to contract the intrafusal fibres at the same time as alpha motoneurons fire?

A

So that intrafusal fibres shorten to match the shortening of the extrafusal fibres.

This means the sensory gamma neurones stay active

Science for shegs (28 decks)

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