coordination and response

a change in the environment that can be detected by an organism

• The CNS (central nervous system) • The PNS (peripheral nervous system)

• Composed of: - brain and spinal cord • Responsible for coordinating all reactions and nervous communication around the body

• Composed of: - Nerves in the other parts • Responsible for transmitting the impulses from the CNS to all parts of the body

• sensory neurone • motor neurone • relay neurone

• Transfer nerve impulses from receptor cells to the spinal cord when a stimulus is detected.

• Transfer nerve impulses from the brain or spinal cord to effectors (such as muscles)

• Connect one neuron to the next • Found in the brain • Make links between the sensory neurons and the motor neurons in the spinal cord

• Junction between two neurons • Allows an impulse to travel from an axon terminal of one neuron to a dendrite in another neuron

• Axon terminals contain tiny, bubble-like structures called vesicles • Vesicles contain substances called neurotransmitters • Receptor molecules in dendrites bind to neurotransmitters

by diffusion

• Rapid • Automatic • Innate (you don’t need to learn how to do them)

• The pathway through the body that brings about a reflex action • receptor → sensory neurone → relay neurone → motor neurone → effector

• Cells that detect different stimuli Include: - Touch receptors in the skin - Sound receptors in the ear - Light receptors in the eye - Taste (chemical) receptors in the nose, tongue and mouth - Temperature receptors in the skin and brain

• Produce a response Eg. A muscle or a gland that produces a hormone

group of receptor cells that respond to a specific stimulus

• cornea → pupil → lens → optic nerve

refracts light, focusing it towards the retina

refracts light, focusing it onto the retina

controls the amount of light passing through the pupil

responds to light levels and to light of different colors

carries nerve impulses from the retina to the brain

• Pupil dilates • Radial muscles contract • Circular muscles relax

• Pupil constricts • Radial muscles relax • Circular muscles contract