afferent nervous system: sensory "input"

Question 1

interpretation of sensory stimuli

Answer 1

-stimuli are detected by receptors (only respond to specific stimulus)

Question 2

receptors can be:

Answer 2

a. dendrites on a unipolar neuron

b. an individual cell that synapses to a neuron e.g. hair cell

Question 3

what happens when a receptor is stimulated

Answer 3

a. stimulus causes opening of gated channels (usually Na) on receptor membrane
b. GP on receptor membrane

Question 4

receptor dendrites

Answer 4

dendrite of unipolar neuron and GP directly generates an AP = generator potential

Question 5

individual cell receptor

Answer 5

individual cell e.g. hair cell ( no axon) = receptor potential - nt onto associated neuron

Question 6

types of receptors: phasic receptors

Answer 6

• receptors respond to stimulus change

- in the presence of a constant stimulus show adaptation

Question 7

types of receptors: tonic receptors

Answer 7

• frequency of APs remains constant - NO adaptation
• give continuous info, protective e.g. posture, pain, condition
• monitor presence + intensity of stimulus

Question 8

how does the brain perceive different types of stimuli

Answer 8

• mainly be type of receptor stimulated
• axon activated by receptor - synaptic connections to part of CNS concerned with that sense
• e.g. stimulate meissners corpuscle in right index finger - impulses to postcentral gyrus region for right index finger.

Question 9

how does the brain perceive stimuli of different strengths

Answer 9

e. g. determining if feather on foot or a brick.
- mainly by frequency of AP going to CNS
- stronger stimulus also activated ore receptors

Question 10

sensory (ascending) pathways

Answer 10

e. g. posterior (dorsal) column pathways for touch

- 3 neurons is succession 1st, 2nd and 3rd order

Question 11

special senses: vision

Answer 11

a. light enters pupil & image focused on retina (reduced + inverted)
b. light stimulates chemical reaction on rods and cones - produces a receptor potential (GP)

Question 12

special senses: hearing

Answer 12

hair cells in cochlear duct stim - receptor potential, no AP

• nt releases onto associated neuron (EPSP, get AP)
• AP on axon of cohlear branch of cranial nerve VIII
• auditory cortex (temporal lobe)

Question 13

special senses: equilibrium

Answer 13

• hair cells in semicircular ducts & saccule or utricle (in vestibule), receptor potential, no AP
• nt releases onto associated neuron, EPSP, get AP)
• AP on axon of vestibular branch of cranial nerve VIII
• then branches into 3 different regions: cerebellum, brain stem, thalamus