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Neurology Week 2 2018/19 > 2: Physiology - Primary sensory neurons and their modalities > Flashcards

2: Physiology - Primary sensory neurons and their modalities Flashcards

1
Q

Which senses is the somatosensory system concerned with?

A

Touch (inc. fine, firm, pressure, vibration)

Pain

Temperature

Itch

Proprioception

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2
Q

Which structures are classed as the

a) CNS
b) PNS?

A

a) Brain and spinal cord

b) Nerves outside the brain and spinal cord

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3
Q

In which nervous system are the bodies of first-order neurons of the somatosensory system found?

A

PNS

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4
Q

Where in the PNS are most first-order neurons found?

A

Dorsal root ganglion

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5
Q

Most first-order neurons are found at the dorsal root ganglion. Where are they found in the head and neck?

A

Cervical ganglia

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6
Q

Which cranial nerve supplies sensory fibres to the anterior head?

A

CN V

Trigeminal nerve

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7
Q

Where do pre-ganglionic sensory fibres from the trigeminal nerve synapse?

A

Cervical ganglia

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8
Q

Second-order neurons of the somatosensory system can be found in either the dorsal horn or the medulla.

Which sensory pathways have second order neurons in the

a) dorsal horn
b) medulla?

A

a) Dorsal column - medial lemniscus system

b) Spinothalamic tract

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9
Q

What sensations are picked up by the

a) DC/ML system
b) spinothalamic tract?

A

a) Fine touch, proprioception, vibration

b) Firm touch, pressure, temperature, pain

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10
Q

Where are third-order neurons of the somatosensory system found?

A

Thalamus

No matter which pathway

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11
Q

In the

a) DC/ML pathway
b) spinothalamic tract

which structures are connected by the first-order neurons?

A

a) Dorsal root ganglia TO medulla

b) Dorsal root ganglia TO spinal cord

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12
Q

As the intensity of a sensory stimulus increases, what happens to the amplitude of the receptor’s potential?

A

As intensity increases, receptor potential amplitude increases

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13
Q

A somatic receptor will generate an action potential once a ___ potential has been reached.

A

threshold

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14
Q

To generate a sensory signal, a stimulus must have enough ___ to overcome the threshold potential of the receptor.

A

intensity

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15
Q

In relation to sensory receptors, what is meant by the term adequate stimulus?

A

Receptors are only activated by the stimulus they are programmed for

e.g a mechanoreceptor won’t generate an action potential in response to heat

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16
Q

Which type of receptors sense touch, pressure and vibration?

Where are they found?

A

Mechanoreceptors

Skin

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17
Q

Which type of receptors are responsible for proprioception?

Where are they found?

A

Mechanoreceptors

Joints and muscles

18
Q

Which type of receptors are responsible for detecting temperature?

A

Thermoreceptors

19
Q

Which type of receptors are responsible for the sensation of pain?

A

Nociceptors

20
Q

What is an adequate stimulus?

A

A stimulus matching the type of receptor which senses it

21
Q

Different receptors respond to increasing ___ of stimulus.

A

intensities

22
Q

What happens to the frequency of action potentials generated by a receptor as the intensity of a stimulus increases?

A

APs become more frequent

23
Q

Which receptors respond to

a) low intensity stimuli
b) high intensity, damaging stimuli?

A

a) Thermoreceptors, mechanoreceptors, etc.

b) Nociceptors

24
Q

What is the difference between low intensity receptors and high intensity nociceptors?

A

Different threshold potentials

i.e each is activated by different intensities of stimulus

25
Q

In slowly adapting receptors, what is the relationship between stimulus intensity and firing rate?

A

Directly proportional

The greater the stimulus intensity, the greater the firing rate

26
Q

In fast adapting receptors, what increases the firing rate?

A

Greater RATE of change in stimulus

i.e a sharp increase will increase the firing rate more than a slow one

27
Q

Which two factors affect the conduction velocity of an axon?

A

1. Diameter of axon (which is difficult to change in real time)

2. Degree of myelination

28
Q

Which type of receptors tend to have the

a) fastest
b) slowest conduction velocities?

A

a) Proprioceptors (body needs constant feedback on where its bits are)

b) Pain fibres (why there’s a delayed response between burning your hand on something and feeling it)

29
Q

Sensory axons are arranged in groups from A to C.

What happens to the axon diameter and degree of myelination as you go from A to C?

A

Axon diameter decreases

Degree of myelination decreases

So conduction velocity decreases

30
Q

What is the term for a sensory nerve’s territory on the skin?

A

Receptive field

31
Q

What is a receptive field?

A

Area on the skin corresponding to the territory of ONE sensory neuron

32
Q

How are sensory nerves arranged in areas of

a) low acuity

b) high acuity?

A

a) Few neurons, big receptive fields

b) Loads of neurons each with their own small receptive fields

33
Q

Sensory nerves have numbered types depending on whether they have small receptive fields or large receptive fields.

What are these types?

A

Type 1 - small sensory fields (high acuity)

Type 2 - large sensory fields (lower acuity)

34
Q

From Dermatology, which skin cells/structures are notable for being prone to a high mortality cancer?

A

Merkel cells

35
Q

Which sensory receptors are found as complexes with Merkel cells?

What a) adaptation and b) receptive field properties do they have?

What do they sense?

A

Merkel cell-neurite complexes

Slow adapting, small receptive fields (so SA1 for short)

Pressure, texture and object edges

36
Q

What do Meissner corpuscles sense?

A

Light touch

37
Q

What do Pacinian corpuscles sense?

A

Pressure

38
Q

What do Ruffini endings detect?

A

Shearing forces

39
Q

What is detected by

a) Merkel cell-neurite complexes
b) Ruffini endings
c) Pacinian corpuscles
d) Meissner corpuscles?

A

a) Fine touch

b) Shearing forces (skin stretching))

c) Pressure, high frequency vibration

d) Low frequency vibration

40
Q

What is a dermatome?

A

Area of skin supplied with sensory fibres from a root of a spinal nerve

So anterior root does the anterior dermatome, posterior root does the posterior dermatome

41
Q

The skin of most of the body is supplied with sensory fibres by spinal nerves.

Which part of the body is supplied with sensory fibres by CN V?

A

Face

42
Q

Which ganglion becomes infected by varicella zoster to cause shingles in a dermatomal pattern?

A

Dorsal root ganglion

Neurology Week 2 2018/19 (10 decks)

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