14 Coordination and Response

along neurones

PNS (peripheral nervous system) - nerves outside brain and spinal cord. CNS (central nervous system) - brain and spinal cord

coordination and regulation of bodily functions

a bundle of nerve cells/neurones

transmit nerve impulses from receptors in sense organs to the brain

transmit nerve impulses from CNS to effector

transmit nerve impulses from sensory to motor neurones

towards the cell body

away from cell body

a pathway where the brain is not involved in creating the response. by the time the brain receives the electrical impulse, the effector is already carrying out the response. stimulus ⇢ receptor ⇢ sensory neurone ⇢ relay neurone (CNS) ⇢ motor neurone ⇢ effector ⇢ response

automatically and rapidly integrating and coordinating stimuli with the responses of effectors

junction between two neurones

• an impulse stimulates the release of neurotransmitter molecules from vesicles into the synaptic gap • neurotransmitter molecules diffuse across the gap down a concentration gradient • neurotransmitter molecules bind with receptor proteins on the next neurone • an impulse is stimulated in the next neurone

collect information from other cells

controls metabolism of nerve cell

carry information over long distance

electrical insulation, prevents distortion of the nervous impulse by activities of neighbouring cells

rapid conduction of impulse by forcing message to jump from one node to the next

• neurotransmitters cannot reach receptors, so there are no impulses. no impulses reach the CNS, so there is no sensitivity to stimuli and no response. • neurotransmitters stay in the synaptic gap, and it can bind to receptors, which continuously stimulates the postsynaptic neurone. more impulses are sent, causing repeated response.

vesicles containing neurotransmitters are only present in the presynaptic bulb, while receptors are only found in the postsynaptic neurone

a group of receptor cells responding to specific stimuli

refracts light

control how much light enters the eye

focuses light into retina