PHGY 215- MODULE 3 PRACTICE
QUESTIONS AND QUALITY ANSWERS.
afferent neurons - Answer - carry nerve impulses from the peripheral receptors and special
sense organs to the CNS.
- also called receptors or sensory neurons
- have a small, round cell body with a single long dendrite and a short axon
- afferent nerve cell bodies are found in clusters called ganglia
- axons extend into the dorsal horn of the spinal cord
receptors - Answer - located at the peripheral ending of afferent neurons and respond to
stimuli from both the internal and external environments
- require a minimum threshold of stimulus before they are activated
transduction - Answer - in order to inform the CNS that a threshold stimulus has been reached
and a receptor activated
- afferent neurons use action potentials to propagate this signal
- this conversion of an environmental signal to an electrical signal
four properties to allow the CNS to accurately differentiate incoming signals from the PNS -
Answer modality, intensity, location, and duration
modality - Answer each type of receptor is specialized to respond to a different type of energy
or stimulus
photoreceptors - Answer receptors that are responsive to visible wavelengths of light
mechanoreceptors - Answer - receptors that are responsive to mechanical energy. ex. skeletal
muscle receptors are sensitive to stretch and the receptors in the ear contain fine hair cells that
bend in response to sound waves
- can also respond to vibration and acceleration
thermoreceptors - Answer receptors that are sensitive to heat
chemoreceptors - Answer receptors that are sensitive to specific chemicals. ex. taste, smell,
contents of the digestive tracts, as well as receptors that sense the presence of oxygen in the
blood
, intensity - Answer nerve cells code the intensity of information by the frequency of action
potentials
note: firing amplitude does not change with signal intensity
location - Answer the brain is able to identify the site of sensory stimulation using the location
of activated afferent fibres.
receptive field - Answer each neuron has a region of the environment to which it is sensitive. if
a stimulus appears here, the neuron will fire and location is communicated to the brain
multiple sensors - Answer our brain can compare inputs from more than one sensor. ex. we
have two eyes and two ears
gradients - Answer with smell, we can determine location based on gradients. ex. we smell
something and move in some direction, if smell becomes intense, we know we're going in the
right direction (source)
duration - Answer - afferent neurons also encode this of stimulus and communicate this to the
brain for processing
- some cells fire as long as the stimulus is present and some fire briefly as the stimulus goes on,
then stop, and then fire briefly when the stimulus goes off
receptor potential (generator potential) - Answer the grade potential change that occurs in a
sensory receptor in response to a stimulus; generates action potentials in the afferent neuron
fibre
specialized afferent ending - Answer the receptor potential itself can cause the afferent nerve
fibre to reach threshold and trigger an AP
separate receptor cell - Answer - when the receptor potential is strong enough it will release a
chemical messenger that diffuses to the afferent neuron and opens chemically gated sodium
channels
- if threshold is achieved, then the afferent nerve fibre will initiate and propagate an AP
site of action potential - Answer - AP is initiated in the periphery and travels towards the cell
body
- in contrast to interneurons and efferent neurons where AP are generated in the axon hillocks
and travel away from the cell body
QUESTIONS AND QUALITY ANSWERS.
afferent neurons - Answer - carry nerve impulses from the peripheral receptors and special
sense organs to the CNS.
- also called receptors or sensory neurons
- have a small, round cell body with a single long dendrite and a short axon
- afferent nerve cell bodies are found in clusters called ganglia
- axons extend into the dorsal horn of the spinal cord
receptors - Answer - located at the peripheral ending of afferent neurons and respond to
stimuli from both the internal and external environments
- require a minimum threshold of stimulus before they are activated
transduction - Answer - in order to inform the CNS that a threshold stimulus has been reached
and a receptor activated
- afferent neurons use action potentials to propagate this signal
- this conversion of an environmental signal to an electrical signal
four properties to allow the CNS to accurately differentiate incoming signals from the PNS -
Answer modality, intensity, location, and duration
modality - Answer each type of receptor is specialized to respond to a different type of energy
or stimulus
photoreceptors - Answer receptors that are responsive to visible wavelengths of light
mechanoreceptors - Answer - receptors that are responsive to mechanical energy. ex. skeletal
muscle receptors are sensitive to stretch and the receptors in the ear contain fine hair cells that
bend in response to sound waves
- can also respond to vibration and acceleration
thermoreceptors - Answer receptors that are sensitive to heat
chemoreceptors - Answer receptors that are sensitive to specific chemicals. ex. taste, smell,
contents of the digestive tracts, as well as receptors that sense the presence of oxygen in the
blood
, intensity - Answer nerve cells code the intensity of information by the frequency of action
potentials
note: firing amplitude does not change with signal intensity
location - Answer the brain is able to identify the site of sensory stimulation using the location
of activated afferent fibres.
receptive field - Answer each neuron has a region of the environment to which it is sensitive. if
a stimulus appears here, the neuron will fire and location is communicated to the brain
multiple sensors - Answer our brain can compare inputs from more than one sensor. ex. we
have two eyes and two ears
gradients - Answer with smell, we can determine location based on gradients. ex. we smell
something and move in some direction, if smell becomes intense, we know we're going in the
right direction (source)
duration - Answer - afferent neurons also encode this of stimulus and communicate this to the
brain for processing
- some cells fire as long as the stimulus is present and some fire briefly as the stimulus goes on,
then stop, and then fire briefly when the stimulus goes off
receptor potential (generator potential) - Answer the grade potential change that occurs in a
sensory receptor in response to a stimulus; generates action potentials in the afferent neuron
fibre
specialized afferent ending - Answer the receptor potential itself can cause the afferent nerve
fibre to reach threshold and trigger an AP
separate receptor cell - Answer - when the receptor potential is strong enough it will release a
chemical messenger that diffuses to the afferent neuron and opens chemically gated sodium
channels
- if threshold is achieved, then the afferent nerve fibre will initiate and propagate an AP
site of action potential - Answer - AP is initiated in the periphery and travels towards the cell
body
- in contrast to interneurons and efferent neurons where AP are generated in the axon hillocks
and travel away from the cell body
