14. Coordination and Response

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

• Describe the human nervous system in terms of:

– the central nervous system consisting of brain and spinal cord

– the peripheral nervous system

– coordination and regulation of body function

• 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

• Distinguish between voluntary and involuntary actions functions

• 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

• 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:

– cornea – refracts light

– iris – controls how much light enters pupil

– lens – focuses light onto retina

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

– optic nerve – carries impulses to the brain

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

• 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

• Define a hormone as a chemical substance, produced by a gland and carried by the blood, which alters the activity of one or more specific target organs

• Identify specific endocrine glands and their secretions, limited to adrenal glands and adrenaline, pancreas and insulin, testes and testosterone and ovaries and oestrogen

• Describe adrenaline as the hormone secreted in ‘fight or flight’ situations and its effects, limited to increased breathing and pulse rate and widened pupils

• Give examples of situations in which adrenaline secretion increases

• State the functions of insulin, oestrogen and testosterone

• Discuss the role of the hormone adrenaline in the chemical control of metabolic activity, including increasing the blood glucose concentration and pulse rate

• Compare nervous and hormonal control systems in terms of speed and longevity of action

• Define homeostasis as the maintenance of a constant internal environment

• Name and identify on a diagram of the skin: hairs, hair erector muscles, sweat glands, receptors, sensory neurones, blood vessels and fatty tissue

• Describe the maintenance of a constant internal body temperature in humans in terms of insulation, sweating, shivering and the role of the brain (limited to blood temperature receptors and coordination)

• Explain that homeostasis is the control of internal conditions within set limits

• Explain the concept of control by negative feedback

• Describe the control of the glucose concentration of the blood by the liver and the roles of insulin and glucagon from the pancreas

• Outline the symptoms and treatment of type 1 diabetes (detail of β cells is not required)

• Describe the maintenance of a constant internal body temperature in humans in terms of vasodilation and vasoconstriction of arterioles supplying skin surface capillaries

• Define gravitropism as a response in which parts of a plant grow towards or away from gravity

• Define phototropism as a response in which parts of a plant grow towards or away from the direction from which light is coming

• Investigate gravitropism and phototropism in shoots and roots

• Explain phototropism and gravitropism of a shoot as examples of the chemical control of plant growth

• Explain the role of auxin in controlling shoot growth, limited to:

– auxin made in shoot tip (only)

– auxin spreads through the plant from the shoot tip

– auxin is unequally distributed in response to light and gravity

– auxin stimulates cell elongation

• Describe the use in weedkillers of the synthetic plant hormone 2,4-D