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KS4 Nervous System
5.1.1 The Importance of Homeostasis
- Know that Homeostasis is the regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes.
- Be able to explain the importance of homeostasis in maintaining optimal conditions for enzyme action and all cell functions.
- Know that in the human body examples include the control of blood glucose concentration, body temperature and water levels.
- Know that automatic homeostatic control systems may involve nervous responses or chemical responses.
- Know that all control systems include:
- cells called receptors, which detect stimuli (changes in the environment)
- coordination centres (such as the brain, spinal cord and pancreas) that receive and process information from receptors
- effectors, muscles or glands, which bring about responses which restore optimum levels.
5.2.1 Structure and function
- Be able to explain how the structure of the nervous system is adapted to its functions.
- Know that the nervous system enables humans to react to their surroundings and to coordinate their behaviour.
- Know that information from receptors passes along cells (neurones) as electrical impulses to the central nervous system (CNS).
- Know that the CNS is the brain and spinal cord and that it coordinates the response of effectors which may be muscles contracting or glands secreting hormones.
- Know the nervous pathway:
stimulus → receptor → coordinator → effector → response
- Be able to explain how the various structures in a reflex arc relate to their function and understand why reflex actions are important.
- Know that reflex actions are automatic and rapid; they do not involve the conscious part of the brain.
- Know that in a simple reflex action such as a pain-withdrawal reflex:
- impulses from a receptor pass along a sensory neurone to the CNS
- at a junction (synapse) between a sensory neurone and a relay neurone in the CNS, a chemical is released that causes an impulse to be sent along a relay neurone
- a chemical is then released at the synapse between a relay neurone and motor neurone in the CNS, causing impulses to be sent along a motor neurone to the effector
- the effector is usually a muscle, in this case to withdraw the limb from the source of pain.
- Be able to extract and interpret data from graphs, charts and tables, about the functioning of the nervous system.
- Be able to translate information about reaction times between numerical and graphical forms.
5.2.2 The brain
- Know that the brain controls complex behaviour and that it is made of billions of interconnected neurones and has different regions that carry out different functions:
- The cerebral cortex is concerned with consciousness, intelligence, memory and language.
- The cerebellum is concerned mainly with the coordination of muscular activity.
- The medulla is concerned with unconscious activities such as heartbeat and breathing.
- Be able to identify the cerebral cortex, cerebellum and medulla on a diagram of the brain.
- Know that neuroscientists have been able to map the regions of the brain to particular functions by studying patients with brain damage, electrically stimulating different parts of the brain and using MRI scanning techniques. But the complexity and delicacy of the brain makes investigating and treating brain disorders very difficult. (HT only)
- Be able to explain some of the difficulties of investigating brain function and treating brain damage and disease.
- Be able to evaluate the benefits and risks of procedures carried out on the brain and nervous system.
5.2.3 The eye
- Be able to relate the structures of the eye to their functions, including accommodation to focus on near or distant objects and adaptation to dim light.
- Know that the eye is a sense organ containing receptors sensitive to light intensity and colour.
- Be able to identify the main structures of the eye on a diagram.
- Know that in the eye:
- the retina contains receptor cells that are sensitive to light
- the optic nerve carries impulses from the retina to the brain
- the tough outer sclera has a transparent region at the front called the cornea
- the muscular iris controls the size of the pupil and the amount of light reaching the retina
- the ciliary muscles and suspensory ligaments can change the shape of the lens to focus light onto the retina.
- Know that accommodation is the process of changing the shape of the lens to focus on near or distant objects.
- Know that to focus on a near object:
- the ciliary muscles contract, the suspensory ligaments loosen, the lens is then thicker and refracts light rays strongly.
- Know that to focus on a distant object:
- the ciliary muscles relax, the suspensory ligaments are pulled tight, the lens is then pulled thin and only slightly refracts light rays.
- Know that two common defects of the eyes are myopia (short sightedness) and hyperopia (long sightedness) in which rays of light do not focus on the retina.
- Know that generally myopia and hyperopia are treated with spectacle lenses which refracted the light rays so that they do focus on the retina.
- Know that new technologies now include hard and soft contact lenses, laser surgery to change the shape of the cornea and a replacement lens in the eye.
- Be able to interpret ray diagrams demonstrating how spectacle lenses correct myopia and hyperopia.
5.2.4 Control of body temperature
- Know that body temperature is monitored and controlled by the thermoregulatory centre in the brain that contains receptors sensitive to the temperature of the blood.
- Know that the skin contains temperature receptors and sends nervous impulses to the thermoregulatory centre.
- Know that if the body temperature is too high, blood vessels dilate (vasodilation) and sweat is produced from the sweat glands. Both these mechanisms cause a transfer of energy from the skin to the environment.
- Know that if the body temperature is too low, blood vessels constrict (vasoconstriction), sweating stops and skeletal muscles contract (shiver).Be able to explain how thermoregulatory mechanisms lower or raise body temperature in a given context. (HT only)
Required practical 7: Plan and carry out an investigation into the effect of a factor on human reaction time.
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