reflexes and reflex arcs vs voluntary arcs

what is a reflex?

• an automatic action

• in response to a stimulus

• very fast

• to protect body from something

what is a stimulus?

a change in environment

what is a receptor?

specialised cell/group of cells that detect stimulus

what is the coordination centre?

where the electrical impulse gets processed to travel to the effector

what is an effector?

muscles or hormones that effect a response, either by: #

• contacting/relaxing muscles

• or glands secreting chemicals/hormones

what is a response?

what the body does in reaction to the stimulus

what is the CNS (central nervous system)?

the brain and spinal cord that consists of relay neurones

what is the PNS (peripheral nervous system?)

neurones in all parts of the body that aren’t the brain or spinal cord

what is the arc for a reflex action?

stimulus→receptor→relay neurone in spinal cord(via sensory neurone)→effector(via motor neurone)→response

what is the arc for a voluntary action?

stimulus→receptor generating the impulse→coordination centre which is the brain(via sensory neurone)→effector(via motor neurone)→response

what are the gaps between neurones called?

synapses

how are electrical impulses transferred across synapses from one neurone to the next?

• impulse arrives at the end of one neurone

• releases chemicals (neurotransmitters) into the synapse

• the chemicals travel and bind to receptors on the next neurone to generate the impulse again

by what process do neurotransmitters transfer from one neurone to the next?

diffusion

• the end of one neurone has many neurotransmitters

• the next neruone doesn’t

• neurotransmitters travel along the concentration gradient to get to where there are fewer neurotransmitters

• this is the next neurone

what is the difference between the arc for a reflex action vs a voluntary action?

reflex arc has the impulse travel from the receptor to the relay neurone which is in the spinal cord. In a voluntary action, the impulse travels from a receptor to the coordination centre which is the brain.