2T

• The brain controls complex behaviour. It is made of billions of interconnected neurones and has different regions that carry out different functions.
• The cerebellum coordinates movement and balance.
• The medulla regulates unconscious activities such as breathing, heart rate, blood pressure, and digestion.
• The cerebral cortex is the largest part of the brain, responsible for conscious thought, memory, language, emotions, and sensory perception.
• The hypothalamus regulates body temperature, hunger, water balance.
• Neuroscientists have been able to map out different parts of the brain to different functions by; Studying patients with brain damage and seeing what functions they cannot do; Electrically stimulating parts of the brain to see any visual movements; Using MRI scans.
• The complexity and delicacy of the brain makes investigating and treating brain disorders very difficult.
• Brain surgery may be needed to remove a tumour, or excess fluid or to relieve pressure on the brain. All surgery carries a level of risk, but due to the complexity and delicacy of the brain, investigating and treating brain disorders can be extremely challenging.
• If surgery is undergone more damage or side-effects may be created, which could affect the patient's quality of life. Serious considerations about the risks involved against the benefits need to be undertaken.
• What is the function of the Cornea?

  Refracts light- bends it as it enters the eye
• What is the function of the Iris?


  Controls how much light enters the pupil
• What is the function of the Lens?

  Further refracts light to focus it onto the retina
• What is the function of the Retina?

  Contains the light receptors
• What is the function of the Optic Nerve?


  Carries impulses between the eye and the brain.
• What is the function of the Sclera?


  The tough white outer layer of the eye. It helps protect the eye from injury.
• Accommodation is the process of changing the shape of the lens to focus on near or distant objects.
• To focus on a near object, the ciliary muscles contract and the suspensory ligaments relax. This then means that the lens is thicker and refracts light strongly.
• To focus on a distant object, the ciliary muscles relax and the suspensory ligaments are pulled tighter. The lens is then pulled thin so only slightly refracts light.'
• Two common eye defects are myopia (short-sighted) and hyperopia (long-sighted) where the rays of do not focus onto the retina.
• Eye defects can generally be treated with spectacle lenses so the light rays are able to focus on the retina. Concave lenses are for hyperopia and convex lenses are for myopia.
• Body temperature is monitored and controlled by the thermoregulatory centre in the hypothalamus.
• The thermoregulatory centre contains receptors that are sensitive to the temperature of the blood while the skin contains temperature receptors and sends nervous impulses to the thermoregulatory centre.
• If body temperature becomes too high, blood vessels will begin to dilate (vasodilation) and sweat will be produced from sweat glands.
• If body temperature becomes too low, blood vessels will constrict (vasoconstriction), sweat will stop producing and skeletal muscles will begin to contract resulting in shivering.
• All methods to regulate body temperature are to cause a transfer of energy from the skin to the environment.
• If body cells lose or gain too much water by osmosis they do not function efficiently
• The digestion of proteins from the diet results in excess amino acids which need to be excreted safely. In the liver, these amino acids are deaminated to form ammonia. However, ammonia is toxic and needs to be converted to urea to be safely excreted.
• The kidneys produce urine by filtration of the blood and selective reabsorption of useful substances such as glucose, some ions and water.
• The body's water levels are controlled by the hormone ADH (antidiuretic hormone) which acts on the kidney's tubules; its effect is on their permeability.
• ADH is released by the pituitary gland when the blood is too concentrated and causes more water to be reabsorbed back into the blood from the kidney tubules resulting in more concentrated urine.
• When there is too much water in the blood, the pituitary gland releases less ADH and so less water is absorbed by the kidneys resulting in more dilute urine.
• People who suffer from kidney failure may be treated by organ transplant or by using Kidney dialysis.
• Kidney Dialysis uses an artificial kidney (hemodialyzer) to remove waste products from the blood. The blood is removed from the body and filtered through the artificial kidney. The filtered blood is then returned to the body with the help of a dialysis machine.
• Plants produce hormones to coordinate and control growth in response to light (phototropism) and gravity (gravitropism).
• Unequal distributions of auxin cause unequal growth rates in plant roots and shoots. Light destroys auxin.
• Gibberellins are important in initiating seed germination.
• Ethene controls cell division and the ripening of fruit.
• Shoots grow toward light but away from gravity. Auxins stimulate growth in shoots.
• Roots grow away from light but towards gravity. Auxins inhibit growth in roots.
• Auxin is used for weed killers, rooting powder and for promoting growth in tissue culture.