Topic 4: Nervous System 2

Question 1

What 2 basic things happen when a receptor is stimulated?

Answer 1

Stimulus causes opening of gated channels (usually Na+) on receptor membrane

Graded potential occurs on membrane: stimulus becomes electrical

Question 2

What are phasic receptors?

Answer 2

They respond to stimulus CHANGE

In the presence of a constant stimulus (eg. wearing a hat) they show ADAPTATION — a decrease in sensitivity

Question 3

In the presence of a constant stimulus, the frequency of APs remains constant in these receptors (no adaptation)

Answer 3

Tonic receptors

Question 4

When is the only time you need an action potential?

Answer 4

Only when you are sending a signal down a long path

Very small cells, like special sense receptors, do not need them

Question 5

What types of potential are involved in vision?

Answer 5

Rods/cones: RECEPTOR P.
Bipolar neuron: GRADED P.
Ganglion cell: ACTION P.
***
Optic nerve (formed by axons of ganglion cells)
Optic tracts
Visual cortex

Question 6

What types of potentials are involved in hearing?

Answer 6

Hair cells in cochlear duct: RECEPTOR P.
nt release onto associated neuron: ACTION P.
***
AP on axon of cochlear branch of cranial nerve
Auditory cortex

Question 7

What are 2 types of receptors?

Answer 7

Dendrites on unipolar neurons
Individual cells which synapse to neurons (eg. hair cells in ear)

Question 8

When a receptor is stimulated, it creates a graded potential which is one of 2 types. What are the types?

Answer 8

GENERATOR potential
occurs on the dendrites of a first order sensory neuron and directly generates an AP

RECEPTOR potential
occurs in receptor cells separate from the neurons: releases nt onto the dendrites of a sensory neuron

Question 9

Explain the process of how phasic receptors allow you to stop feeling a hat on your head after a while

Answer 9

Mechanoreceptors in the skin detect the onset of the stimulus and initially there is a burst of APs (feel the hat)

Over time the receptors adapt and the AP frequency to CNS decreases

When the hat is removed, the receptors respond again to the change in pressure

Question 10

How does the brain perceive different types of stimuli?

Answer 10

Mainly by the type of receptor stimulated

Eg. stimulate Meissner’s corpuscle (touch receptor) in finger ~> impulses to post central gyrus reason
Eg. all signals received from the retina perceived as light

Question 11

How does the brain perceive stimuli of different strengths?

Answer 11

Mainly by the frequency of the APs