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Y1 Fundamentals of Neuroscience and Pharmacology > L13: Somatosensory > Flashcards

L13: Somatosensory Flashcards

1
Q

What type of neurons generate action potentials at their nerve endings rather than the cell body?

A

Primary sensory neurons.

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2
Q

What are the three main types of sensory receptors involved in detecting mechanical stimuli in the skin?

A

Mechanoreceptors, thermoreceptors, and nociceptors.

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3
Q

What is the main excitatory neurotransmitter in the central nervous system?

A

Glutamate.

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4
Q

How are axons classified based on diameter and conduction speed?

A

From thick and heavily myelinated (fast conduction, e.g., Aα and Aβ fibers) to thin and unmyelinated (slow conduction, e.g., C fibers).

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5
Q

What is the term for the area of skin innervated by branches of a single sensory neuron?

A

Receptive field.

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6
Q

What sensory test measures the ability to distinguish two points of contact on the skin?

A

Two-point discrimination test.

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7
Q

Which sensory receptors are found in high density in the fingertips and lips and are involved in detecting texture and form?

A

Merkel cells.

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8
Q

What is the function of Pacinian corpuscles?

A

To detect deep pressure and high-frequency vibration.

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9
Q

What kind of adaptation is characteristic of fast-adapting (phasic) receptors?

A

They respond to changes in stimulus but stop firing if the stimulus is constant.

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10
Q

What type of ion channels are activated by physical deformation of the skin?

A

Piezo channels.

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11
Q

What neurotransmitter is released at the synaptic junctions of primary sensory neurons?

A

Glutamate.

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12
Q

What are nociceptors and what do they detect?

A

Nociceptors are pain receptors that respond to noxious stimuli that could damage tissue.

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13
Q

Which receptors are activated by capsaicin, the chemical in chili peppers?

A

TRPV1 channels.

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14
Q

What is proprioception, and which sensory organs are involved?

A

Proprioception is the sense of body position and movement, involving muscle spindles and Golgi tendon organs.

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15
Q

How is sensory information transmitted to the brain from the body?

A

Through two main pathways: the dorsal column-medial lemniscal pathway (for fine touch and proprioception) and the spinothalamic pathway (for pain and temperature).

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16
Q

What is the difference between slow-adapting and fast-adapting receptors?

A

Slow-adapting receptors maintain their response as long as the stimulus is present, while fast-adapting receptors respond only to changes in the stimulus.

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17
Q

What is the function of the Golgi tendon organ?

A

It detects tension in muscles and provides feedback to regulate force generation.

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18
Q

Where are the cell bodies of primary sensory neurons located?

A

In the dorsal root ganglia, outside the central nervous system.

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19
Q

What are the two types of thermoreceptors, and what do they detect?

A

Warm receptors (respond to heat) and cold receptors (respond to cooling).

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20
Q

What kind of sensory information is carried by Aβ fibers?

A

Touch, pressure, and vibration.

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21
Q

What phenomenon explains why pain is felt after touch during an injury?

A

Touch signals are carried by faster Aβ fibers, while pain signals are transmitted by slower Aδ and C fibers.

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22
Q

What is the significance of receptive field size in sensory neurons?

A

Smaller receptive fields allow for greater precision in detecting stimuli, as seen in fingertips compared to the back.

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23
Q

How do free nerve endings differ from other sensory receptors in the skin?

A

Free nerve endings lack specialized structures and are involved in detecting pain, temperature, and some light touch.

24
Q

What is the main role of Meissner’s corpuscles?

A

To detect light touch and low-frequency vibration, particularly in glabrous (hairless) skin.

25
Q

What are Ruffini endings, and what do they detect?

A

Ruffini endings are mechanoreceptors that detect skin stretch and help in detecting sustained pressure.

26
Q

What is the dorsal column-medial lemniscal pathway responsible for transmitting?

A

Fine touch, vibration, and proprioception information.

27
Q

What is the primary difference between the dorsal column-medial lemniscal pathway and the spinothalamic pathway?

A

The dorsal column-medial lemniscal pathway transmits fast, precise sensory information, while the spinothalamic pathway transmits slower, less localized signals like pain and temperature.

28
Q

What kind of stimuli do TRPV1 channels respond to?

A

Heat, capsaicin (from chili peppers), and noxious heat (above 46°C).

29
Q

What is two-point discrimination, and why does it vary across the body?

A

Two-point discrimination measures the ability to perceive two separate stimuli. It varies due to differences in receptor density and receptive field size across body parts.

30
Q

How do fast-adapting receptors like Pacinian corpuscles help detect vibration?

A

They respond to changes in pressure and vibration, but not to sustained pressure.

31
Q

Why are elderly people more likely to drop objects?

A

They may lose sensory receptors over time, reducing their ability to detect slippage and adjust grip strength.

32
Q

How does the brain interpret temperature if thermoreceptors do not detect absolute temperature?

A

The brain integrates signals from both warm and cold receptors to perceive temperature changes.

33
Q

What triggers a reflex action mediated by proprioceptive sensory organs?

A

Stretch or tension detected by muscle spindles or Golgi tendon organs sends signals to the spinal cord, initiating a reflex.

34
Q

What are Piezo channels, and what stimuli do they respond to?

A

Piezo channels are mechanosensitive ion channels that respond to physical deformation, like touch or pressure.

35
Q

What type of mechanoreceptors are involved in detecting fine textures and sustained pressure?

A

Merkel cells.

36
Q

What does the term ‘polymodal nociceptors’ mean?

A

Nociceptors that respond to multiple types of noxious stimuli, including mechanical, thermal, and chemical.

37
Q

What is the purpose of tonic receptors, and how do they respond to stimuli?

A

Tonic receptors provide continuous information about a stimulus and do not adapt quickly, making them important for sustained sensations like pain or muscle stretch.

38
Q

Why is the density of sensory receptors higher in the fingers and lips compared to the back?

A

These areas are involved in fine tactile exploration and require greater sensory precision for tasks like handling objects or detecting textures.

39
Q

What role do hair follicle receptors play in sensory perception?

A

They detect deflection or movement of hairs, providing information about light touch and environmental changes.

40
Q

What Nobel Prize-winning discovery was made about sensory ion channels in 2021?

A

The discovery of Piezo channels for touch and TRPV1 channels for temperature and pain.

41
Q

How do nociceptors signal potentially damaging stimuli?

A

They have a high activation threshold and respond only to noxious stimuli that may damage tissues.

42
Q

What is the significance of the spinothalamic pathway in sensory transmission?

A

It carries slower signals related to pain, temperature, and crude touch to the brain via synapses in the spinal cord.

43
Q

How does receptor adaptation enhance sensory efficiency?

A

Fast-adapting receptors ignore constant stimuli to focus on changes, while slow-adapting receptors provide continuous feedback for ongoing stimuli.

44
Q

What is the role of muscle spindles in proprioception?

A

Muscle spindles detect changes in muscle length and provide information about the position and movement of limbs.

45
Q

What sensory information is primarily detected by Aδ fibers?

A

Sharp, localized pain and some temperature changes.

46
Q

What are the characteristics of C fibers, and what sensory signals do they carry?

A

C fibers are unmyelinated, slow-conducting fibers that transmit dull, aching pain and temperature.

47
Q

What sensory receptor type is responsible for detecting object slippage in the hand?

A

Ruffini endings, which respond to skin stretch.

48
Q

How do Merkel cell-neurite complexes function in sensory detection?

A

They detect sustained light touch and pressure, helping perceive texture and shape.

49
Q

What does the term ‘homunculus’ represent in sensory neuroscience?

A

A distorted representation of the body in the sensory cortex, reflecting the density of sensory neurons in different body areas.

50
Q

How does the brain prioritize sensory information from different body parts?

A

Areas like the hands and lips have more sensory neurons and occupy larger regions of the somatosensory cortex due to their importance in tactile exploration.

51
Q

What is signal transduction in sensory systems?

A

The process of converting a physical stimulus into electrical signals (action potentials) in sensory neurons.

52
Q

Why do some sensory neurons fire at higher frequencies during stronger stimuli?

A

The firing rate is proportional to the intensity of the stimulus, allowing the brain to gauge stimulus strength.

53
Q

What is the function of the dorsal root ganglion in sensory transmission?

A

It houses the cell bodies of sensory neurons that transmit signals from the periphery to the spinal cord.

54
Q

What type of stimuli do free nerve endings detect?

A

Pain, temperature changes, and crude touch.

55
Q

How does aging affect sensory receptor density and function?

A

Aging can reduce the number of sensory receptors, leading to decreased sensitivity and higher risk of dropping objects or missing stimuli.

Y1 Fundamentals of Neuroscience and Pharmacology (16 decks)

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