Lecture 14

Question 1

What are the 5 somatic senses?

Answer 1

touch, temperature, pain, proprioception, itch/vibration

Question 2

What are the 4 types of sensory receptors

Answer 2

mechano-, thermo-, photo-, chemo-

Question 3

Define adequate stimulus

Answer 3

stimulus that receptors respond most strongly to, may respond to other stimuli as well

Question 4

Define receptor potential

Answer 4

change in membrane potential of the receptor

threshold stimulus –> minimum stimulus needed to produce a receptor potential leading to an intracellular response

Question 5

Describe receptive fields and the perception threshold

Answer 5

perception threshold –> minimum stimulus intensity required for activation of 2/3 neurons and signal transmission to brain for perception

each neuron linked to a specific area, then synapses onto a 2 neuron. If 2 different 2 neurons are innervated, then it is sensed as discriminate signals, if the 2 primary neurons converge, there is no 2 point discrimination

Question 6

how is stimulus modality, location, intensity, and duration distinguished?

Answer 6

modality/location –> based on areas of brain innervated, type of receptor activated
-brain associates signal from group of receptors with particular modality (see photoreceptors as light even if triggered mechanically)
intensity/duration –> based on action potential frequency/duration

Question 7

Describe lateral inhibition

Answer 7

The neuron most activated will synapse onto adjacent neurons and inhibit their response, creates a greater difference in signalling for enhanced perception, enhances contrast

Question 8

How do sensors adapt?

Answer 8

either tonic or phasic
tonic = slow adapting, respond for duration of stimulus
phasic = rapidly adapting and turn off

Question 9

Describe the different skin receptor types

Answer 9

Ruffini --> skin stretch, deep, slow
Meissner --> stroking, surface, rapid
Merkel --> pressure, surface, tonic
Pacinian --> vibration, deep, rapid
free nerve endings --> pain/temperature/hair movement

Question 10

Describe the two sensory pathways

Answer 10

dorsal column (fine touch, proprioception, vision) --> synapses in medulla, crosses midline in medulla
spinal thalamic (coarse touch, temperature, pain) --> synapses in dorsal horn, crosses midline in the spinal cord, synapses to the thalamus