14.1-2 Nervous Control

14.1 Nervous control in humans

• Describe a nerve impulse as an electrical signal that passes along nerve cells called neurones

• Describe the human nervous system in terms of:

1. the central nervous system consisting of brain and spinal cord

2. the peripheral nervous system

3. coordination and regulation of body functions

• Identify motor (effector), relay (connector) and sensory neurones from diagrams

• Describe a simple reflex arc in terms of receptor, sensory neurone, relay neurone, motor neurones and effector

• Describe a reflex action as a means of automatically and rapidly integrating and coordinating stimuli with the responses of effectors (muscles and glands)

• Define a synapse as a junction between two neurones

Supplement:

• Distinguish between voluntary and involuntary actions

• Describe the structure of a synapse, including the presence of neurotransmitter containing vesicles, the synaptic cleft and neurotransmitter receptor molecules

• Describe how an impulse triggers the release of a neurotransmitter from vesicles into the synaptic gap and how the neurotransmitter diffuses across to bind with receptor molecules, in the membrane of the neurone after the synaptic gap, causing the impulse to continue

• State that in a reflex arc the synapses ensure that impulses travel in one direction only

• State that many drugs, e.g. heroin, act upon synapses

14.2 Sense organs

• Define sense organs as groups of receptor cells responding to specific stimuli: light, sound, touch, temperature and chemicals

• Identify the structures of the eye, limited to cornea, iris, pupil, lens, retina, optic nerve and blind spot

• Describe the function of each part of the eye, limited to:

1. cornea – refracts light

2. iris – controls how much light enters pupil

3. lens – focuses light onto retina

4. retina – contains light receptors, some sensitive to light of different colours

5. optic nerve – carries impulses to the brain

• Explain the pupil reflex in terms of light intensity and pupil diameter only

Supplement:

• Explain the pupil reflex in terms of light intensity and antagonistic action of circular and radial muscles in the iris

• Explain accommodation to view near and distant objects in terms of the contraction and relaxation of the ciliary muscles, tension in the suspensory ligaments, shape of the lens and refraction of light

• State the distribution of rods and cones in the retina of a human

• Outline the function of rods and cones, limited to greater sensitivity of rods for night vision and three different kinds of cones absorbing light of different colours for colour vision

• Identify the position of the fovea.