Sensory receptors

Question 1

What are sensory receptors?

Answer 1

Nerve endings, often with specialised non-neural structures. They are transducers that convert different forms of energy into frequency of Action Potentials (APs).

Question 2

Sensory modality

Answer 2

a type of stimulus activating a particular receptor: eg. touch, pressure, pain, temperature, light.

Question 3

An adequate stimulus

Answer 3

the type of energy a receptor normally responds to.

Question 4

What are Mechanoreceptors?

Answer 4

stimulated by mechanical stimuli - pressure, stretch, or deformation. Detect many stimuli - hearing, balance, blood pressure and skin sensations of touch and pressure.

Question 5

What are Proprioreceptors?

Answer 5

are mechanoreceptors in joints and muscles that signal information related to body or limb position

Question 6

What are nociceptors?

Answer 6

respond to painful stimuli - tissue damage and heat

Question 7

Cutaneous Mechanoreceptors and Proprioceptors

Answer 7

• are good examples of the principles of peripheral sensory processing
• transduction in ALL sensory receptors involves opening or closing of ion channels

Question 8

What does an adequate stimulus cause?

Answer 8

• an adequate stimulus causes a graded membrane potential change called a receptor potential or a generator potential (millivolts)
• the adequate stimulus in cutaneous mechanoreceptors and proprioceptors is called membrane deformation.
• this activates stretch-sensitive ion channels causing ion flow across the membrane.

Question 9

What does a stimulus cause?

Answer 9

It causes local current to flow to the part of the membrane with voltage-gated ion channels.

• This generates action potentials (APs).
• In myelinated sensory nerves, this is where myelination starts

Question 10

What is the frequency coding of stimulus intensity.

Answer 10

-The larger the stimulus, the larger the receptor potential and
the HIGHER THE FREQUENCY of APs in a sensory nerve

Question 11

What is adaptation?

Answer 11

• some mechanoreceptors ADAPT to a maintained stimulus and only signal change – eg. the onset of stimulation.
• The mechanoreceptor only signals the onset of a stimulus.

Question 12

Do nociceptors adapt?

Answer 12

NO

Nociceptors which are free nerve endings detecting painful stimuli and it is important not to ignore important stimuli.

Question 13

How does the Pacinian corpuscle (mechanoreceptor) respond?

Answer 13

• a mechanical stimulus deforms the capsule and nerve ending
• This stretches the nerve ending and opens ion channels
• Na+ influx causes local depolarisation – a generator potential
• APs are generated and fire at the myelinated nerve

Question 14

What is the receptive field?

Answer 14

The area in which a somatic sensory neuron is activated by stimuli/

Question 15

What 2 things allows us to tell 2 points on the skin apart?

Answer 15

Receptive field size and Neuronal convergence.

-It is determined by a two point discrimination test.

Question 16

What is acuity?

Answer 16

-The ability to locate a stimulus on the skin and differentiate it from another close by.

Question 17

Lateral inhibition

Answer 17

• Is a major mechanism for “sharpening or cleaning up” sensory information.
• Is a major component in pathways with high precision information eg touch and skin hair movement.
• Allows precise localisation to a single skin hair movement.