Chapter 5: Reflexes & Reaction Times

neuron

nerve cell, single cell that specializes in communication via electrical impulses

soma

cell body; large part of neuron containing the nucleus and organelles

axon

single long projection responsible for transmitting information from the cell body to the next cell

axon hillock

portion of axon connecting the cell body; swollen

- site of action potential generation

axon terminals

end of an axon will branch slightly--responsible for converting the electrical impulse to a chemical signal and passing information to the next cell in line

synapse

junction between two nerve cells

pre-synaptic neuron

neuron that sends signal

post-synaptic neuron

neuron receiving the signal

action potential

electrical impulse that travels down the axon of a neuron

neurotransmitter

a chemical that is used to communicate between neurons

local potential

a small electrical impulse that fades over a distance

excitatory

causes next neuron to initiate an action potential in its axon

inhibitory

less likely to initiate an action potential in next neuron

afferent (sensory) neurons

convey impulses towards the central nervous system from sensory receptors found throughout the body

efferent (motor) neurons

convey impulses away from the central nervous system to a target---muscle or gland

interneurons

found within the central nervous system; connect afferent and efferent neurons and integrate sensory and motor input

reflex

a very fast, involuntary response to a stimulus

latency

a reflex refers to the amount of time that passes between the initial stimulus and the response

in what direction does the action potential travel in the sensory neuron?

to the spinal cord

in what direction does the action potential travel in the motor neuron?

away from spinal cord

Where is the cell body of the afferent neuron located?

dorsal root ganglion

Where does the axon of the afferent neuron enter the spinal cord?

through the dorsal root

Where are the cell bodies of efferent neurons located?

ventral horn

where does the axon of the efferent neuron exit the spinal cord?

ventral root

What is the difference between a reflex and a voluntary reaction?

reflex: involuntary, rapid response to stimulus--only travels to spinal cord

voluntary: take longer---needs to travel to the brain

factors that could increase or decrease reaction time

fatigue & injury

compare the amplitude & latency of a knee-jerk response without and with the Jendrassik maneuver

Latency: doesn't change

- should be the same because reflexes go through same maneuver

Amplitude: higher, less inhibition in movement--kick higher because not focused on it

Two volunteers, Liam (6ft tall), Jackie (5 ft tall)-- which volunteer will have the faster knee-jerk response and why?

Jackie--shorter, less distance for signal to travel

Latency difference between visual and auditory cues?

longer for auditory because it takes longer to hear than to see