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neurologyYou need to know

• Homeostasis is the regulation of internal conditions, such as blood glucose concentration, body temperature and water levels, to keep them within narrow limits despite internal or external change.
• Homeostasis is important because cells and enzymes need stable conditions to function efficiently and to prevent damage to the body.
• A control system includes receptors that detect a stimulus, coordination centres such as the brain, spinal cord or pancreas that process information, and effectors such as muscles or glands that bring about a response.
• The nervous system uses electrical impulses carried by neurones and is usually fast, short-lived and localised, whereas the endocrine system uses hormones carried in the blood and is usually slower, longer-lasting and widespread.
• A reflex action is a rapid automatic response in which a stimulus is detected by a receptor, an impulse travels along a sensory neurone to the central nervous system, crosses synapses to a relay neurone and then a motor neurone, and causes an effector to respond.
• Reflex actions are involuntary, rapid and protective because they reduce the time between detecting danger and producing a response.
• A synapse is the junction between two neurones where the electrical impulse is transferred across a small gap using chemical neurotransmitters.
• At a synapse, an electrical impulse causes neurotransmitter to be released from one neurone, the neurotransmitter diffuses across the gap, binds to receptors on the next neurone, and triggers a new electrical impulse.
• A hormone is a chemical messenger released by an endocrine gland into the blood and carried to specific target organs.
• The pituitary gland is located at the base of the brain and is called the master gland because it releases hormones that control other endocrine glands.
• The main endocrine glands include the pituitary gland in the brain, thyroid gland in the neck, adrenal glands above the kidneys, pancreas in the abdomen, ovaries in females and testes in males.
• Adrenaline is released by the adrenal glands and prepares the body for fight or flight by increasing heart rate and blood flow to muscles, while thyroxine from the thyroid gland controls metabolic rate, growth and development.
• Negative feedback is a control mechanism in which a change away from the normal level triggers responses that bring the level back towards normal.
• The pancreas monitors blood glucose concentration and releases insulin when blood glucose is too high and glucagon when blood glucose is too low.
• Insulin lowers blood glucose concentration by causing body cells to take up glucose and causing liver and muscle cells to convert glucose into glycogen for storage.
• Glucagon raises blood glucose concentration by causing liver cells to break down glycogen into glucose and release glucose into the blood.
• Type 1 diabetes is usually caused by the pancreas producing little or no insulin and is treated with insulin injections and careful diet, whereas type 2 diabetes is linked to insulin resistance and is often managed by diet, exercise, weight loss and sometimes medication.
• The menstrual cycle is controlled by FSH, oestrogen, LH and progesterone: FSH stimulates egg maturation and oestrogen production, oestrogen rebuilds the uterus lining and triggers LH release, LH triggers ovulation, and progesterone maintains the uterus lining.
• The kidneys remove urea from the blood, adjust ion levels and control water content by filtering the blood and selectively reabsorbing useful substances such as glucose, some ions and the amount of water needed by the body.
• Auxin is a plant hormone that controls growth responses to light and gravity by causing unequal growth rates in shoots and roots.

• Calculate reaction time from practical results, then compare results using appropriate units and identify patterns or anomalies.
• Interpret graphs, charts and tables by describing trends, comparing values and using data to support biological explanations.
• Construct a stimulus-response pathway for a reflex action in the correct order: stimulus, receptor, sensory neurone, relay neurone, motor neurone, effector and response.
• Explain negative feedback by identifying the change from the optimum, the receptor or coordination centre, the effector response and how the response restores the normal level.
• Compare type 1 and type 2 diabetes by linking the cause of each condition to its treatment and explaining how blood glucose regulation is affected.
• Interpret menstrual cycle graphs by linking changes in FSH, oestrogen, LH and progesterone to egg maturation, ovulation and changes in the uterus lining.
• Evaluate hormonal and non-hormonal contraception by comparing effectiveness, side effects, protection from sexually transmitted infections, convenience and ethical or personal factors.
• Evaluate infertility treatment using hormones and IVF by weighing possible benefits, risks, success rates, cost, emotional impact and the perspectives of patients and doctors.
• Explain kidney function using the processes of filtration and selective reabsorption, including how ADH changes water reabsorption to control blood water levels.
• Explain plant responses by linking the direction of light or gravity to auxin distribution and the resulting unequal growth of shoots or roots.