Sensory System Flashcards

1
Q

What are tonic receptors?

A

Tonic receptors are slow adapting receptors. They will respond to the stimulus as long as it persists, and produce a continuous high frequency of action potentials.

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2
Q

What are phasic receptors?

A

Phasic receptors are rapidly adapting receptors. They will respond quickly to stimuli but stop responding upon continual stimulation. Therefore action potential frequency decreases during prolonged stimulation. The receptor remains sensitive to a change in stimulus energy or removal of the stimulus.

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3
Q

What are nociceptors?

A

Nocioceptors are phasic receptors, which respond to noxious stimuli (stimuli that would cause tissue injury if they were to persist) and result in the sensation of pain.

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4
Q

What types of fibres carry pain?

A

type Aδ fibres and type C fibres that transmit the pain sensation.

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5
Q

How can receptors be categorised?

A

Mechanical – stimulated by the distension of skin (stretch) and pressure eg. in inflammation

Thermal – stimulated by extremities of temperature

Chemical – stimulated by exogenous and endogenous chemical agents, such as prostanoids, histamines etc

Polymodal – can respond to more than one stimuli

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6
Q

Where are mechanoreceptors found and what do they respond to?

A

These are located in joint capsules, ligaments, tendons, muscle and skin, and respond to deformation by the means of pressure, touch, vibration or stretch.

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7
Q

Give examples of mechnoreceptors?

A
Merkel's discs
Meissner's corpuscle
Pacinian corpuscle
Ruffini end-organs
Muscle spindles and Golgi tendon organs
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8
Q

Describe Merkel’s discs

A

These are tonic receptors present in skin, near the border of the dermis and epidermis. They respond to pressure and help to differentiate texture and shape of objects.

Small receptive field, slowly adapting. Sense gentle pressure.

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9
Q

Describe Meissner’s corpuscles

A

These are phasic present in the dermis of the skin skin, namely on the palms of the hands, soles of the feet, lips and tongue. Consisting of Aβ fibres, they enable two-point discrimination- fine touch.

Small receptive field, rapidly adapting. Sense slower vibration and light touch

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10
Q

Describe Pacinian corpuscles

A

These phasic receptors that also consist of Aβ fibres, and are the largest category of mechanoreceptors. They respond to pressure changes and vibration. They exist places such as: the dermis, hypodermis, ligaments and external genitalia

Large receptive field, rapidly adapting. Found deep in dermis. Sense fast vibration and gross pressure changes.

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11
Q

Describe Ruffini end organs

A

These are tonic receptors present in the dermis and respond to stretch

Large receptive field, slowly adapting. Sensitive to skin stretch, sustained pressure

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12
Q

Describe muscle spindles and golgi tendon organs.

A

These exist in skeletal muscle and detect sensory stimuli relating to stretch. Input is responsible for reflexes and motor control via the cerebellum. It is also transmitted to the DCML component of the spinal cord, reaching the cerebral cortex and provides information about posture, position and orientation

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13
Q

What do Krause end bulbs detect?

A

Thermoceptors - head and cold

Mucus membranes and joints

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14
Q

How is sensory acuity determined?

A

the size of the receptive field – acuity is higher with a smaller receptive field (and acuity is enhanced by lateral inhibition via inhibitory interneurons). 

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