unit 14 - coordination and response Flashcards
what is a nerve
a bundle of neurons
where are electrical impulses sent through
through nerves to quickly send signals around the body
what are nerve electrical impulses used for
examples (5)
for rapidly coordinating or regulating the bodies functions
eg pupils dilate, breathing contractions, bladder relaxes, stomach digestion, heart rate.
what does the central nervous system consist of
brain and spinal cord
function and look of dendrites
receive signals from surrounding neurons . they are branches to allow connections with many neurons
function of axon
a long structure off the cell body that electrical signals can rapidly be sent through. its long length allows for signals to be sent rapidly
what is the axon terminal
where the signal is passed to the next neuron over the synapse
4 steps of reflex responses / how nerve signals are sent
- a stimulus is received by a receptor
- sensory neurons pass these signals back to the relay neuron in the CNS
- relay neuron sends this signal on to the motor neuron
- motor neuron sends the signal to an effector organ which is then stimulated to respond.
stimuli examples
light, sound, touch, temperature, chemicals.
what is a reflex action
a means of automatically and rapidly integrating and coordinating stimuli with the response of effectors
what are effector organs
muscle or gland
where is cell body on a sensory neuron
half way down axon
defining look of relay neuron
short axon
where is cell body on motor neuron
at end with dendrites
what is the synapse
the junction between 2 neurons
what does the presynaptic cell do
releases neurotransmitters into the synaptic cleft, which then bind to receptors on the postsynaptic cell, triggering a response
how electrical impulses trvael from neurone to neurone
- electrical impulses trvael along the first axon
- this triggers the nerve ending of the presynaptic neurone to release neurotransmitters from vesicles which fuse with the presynaptic membrane
- neurotransmitters diffuse across the synaptic cleft and bind with the receptor molecules on the postsynaptic membrane
- thus stimulates 2nd neurone to generate and electrical impulse that trvales down the 2nd axon
why are neurotransmitters destroyed
to prevent continued stimulation which would cause repeated impulses to be sent
why do impulses only travel one way
neurotransmitters are released from the presynaptic end only and their receptors are present on the postsynaptic end only
function of the optic nerve
sends nerve signals from rod and cone cells in the retina to the brain.
function of the retina
is where light is focused in the eye. it contains light sensitive rod and cone receptor cells
function of the iris
is the coloured part of the eye which affects pupil size
function of the lens
is able to change shape to focus light on the retina
function of pupil
is the opening in the eye which allows light to enter
function of cornea
the curved part of the eye which refracts light as it enters
function of the suspensory ligaments
attaches the lens to the ciliary muscles
function of the ciliary muscles
they contract or relax to make the suspensory ligaments go slack or tight respectively, therefore changing the shape of the lens.