b5

• Cerebral cortex - language and memory
• cerebellum - muscle coordination
• medulla - unconscious behaviour
• hormones - chemical molecules carried in the blood
• reflex arc


  stimuli

  receptor

  sensory neurone

  motor neuron (cns)

  relay neurone

  effector (muscle or glands)

  response
• homeostasis controls..

  • blood glucose levels
  • water levels
  • body temperature
• nervous system

  the brain and spinal cord

  carry electrical impulses around the body

  immediate, short, precise
• endocrine system

  glands that secrete hormones into the bloodstream

  lasts longer and is slower compared to nervous system
• thyroid

  • produces thyroxine
  • regulates metabolism and heart rate
  • controls body temperature
  • found in neck
• pituitary gland

  • master gland
  • regulates body conditions
  • stimulates other glands
  • found in brain
• adrenal gland

  • produces adrenaline
  • involved in stressful situations
  • found in kidneys
• pancreas

  • produces insulin
  • controls blood glucose levels
• ovaries

  • produces oestrogen
  • involved in menstrual cycle
• testes

  • produces testosterone
• investigating brain function is difficult because

  • brain is complex and delicate
  • easily damaged
  • drugs cannot always reach the brain because of the membrane surrounding it
  • not fully understood what the brain does
• neuroscientists study the brain by

  • observing patients with brain damage
  • electrically stimulating different parts of the brain
  • mri scans
• synapse - gap between two neurones
• waste products examples

  • ions - from food
  • urea
  • water - leave as sweat or, depending on concentration, as urine
• Gibberellins are used for:

  1. Ending seed dormancy
  2. Promoting flowering
  3. Increasing fruit size
• As ethene controls ripening, it is used in the food industry.

  • Fruit is picked when it is not ripe
  • When it is needed to be sold, it is exposed to ethene and warmer temperatures
  • Ethene is involved in controlling cell division and stimulates enzymes that result in fruit ripening.
  • This reduces wastage as more fruit is suitable to be sold and it does not ripen too early
• 1. FSH causes maturation of an egg in the ovary, in follicle, produced in pituitary gland, stimulates the ovaries to produce oestrogen
  2. Oestrogen causes the lining of the uterus to grow again -Produced in the ovaries, Secreted as a result of FSH, Stimulates the production of LH and inhibits secretion of FSH
  3. LH - Produced in the pituitary gland, produced as a result of oestrogen, its release results in ovulation
  4. Progesterone - Produced in the ovaries and secreted from the egg follicle, maintains uterus lining, supports a pregnancy if the egg is fertilised, inhibits the release of FSH and LH
• FSH (follicle stimulating hormone) causes maturation of an egg in the ovary, in follicle, produced in pituitary gland, stimulates the ovaries to produce oestrogen
• Oestrogen causes the lining of the uterus to grow again - Produced in the ovaries, Secreted as a result of FSH, Stimulates the production of LH and inhibits secretion of FSH
• LH (luteinising hormone) - Produced in the pituitary gland, produced as a result of oestrogen, its release results in ovulation
• Progesterone - Produced in the ovaries and secreted from the egg follicle, maintains uterus lining, supports a pregnancy if the egg is fertilised, inhibits the release of FSH and LH
• 1. When blood glucose levels fall too low, it's detected by the pancreas.
  2. This causes the pancreas to release the hormone glucagon into the blood stream.
  3. This hormone then travels around the body, and binds mainly to cells in the liver.
  4. This stimulates those liver cells to break down their stored glycogen into glucose and release it into the blood. 
  5. This extra glucose increases blood glucose levels back up to normal.
• When blood glucose levels get too high, insulin is released from the pancreas into the bloodstream. This causes organs such as the liver and muscles to absorb glucose from the blood, and convert it into glycogen.
• • Retina: Layer of light sensitive cells found at the back of the eye. When light hits this, the cells are stimulated
  • Optic nerve: eye to the brain, carries impulses from retina to brain to create image
  • Sclera: White outer layer - supports structures inside, strong to prevent damage to the eye
  • Cornea: allows light through and the curved surface bends and focuses light onto the retina
  • Iris: Muscles that surround the pupil They contract or relax to alter the size of the pupil
  • Ciliary muscles and suspensory ligaments: Hold the lens in place, control its shape
• Short sightedness is called myopia.

  • The lens is too curved, so distant objects appear blurry.

  long sightedness is called hyperopia

  • The lens is too flat, so it cannot refract light enough.
• Human body temperature is 37.5

  If it becomes too high:

  • Sweat (evaporates from skin surface - increases energy transfer away from body) produced from sweat glands
  • Vasodilation means more blood flows closer to the surface of the skin, resulting in increased energy transfer from the body

  If it decreases too much:

  • Sweating stops
  • Skeletal muscles contract rapidly (shivering) to generate heat from respiration
  • Hairs stand on end to create an insulating layer, trapping warm air
  • Vasoconstriction means blood does not flow so close to the surface, resulting in less heat lost
• diabetes = cant control blood glucose level.

  Type 1 diabetes:

  • the pancreas cannot produce enough insulin so blood glucose level rises extremely
  • Glucose is excreted with urine and lots of urine is produced leaving the individual very thirsty
  • treated with insulin injections at meal times, results in glucose being taken up from the bloodstream
  • advised to limit intake of carbohydrates which contain lots of glucose, regular exercise
  • Doctors are attempting to cure diabetes with pancreas and pancreatic cell transplants, and genetically engineering pancreatic cells from mice to make insulin
• Type 2 diabetes: the body cells no longer respond to insulin

  • Blood glucose levels can rise to a fatal amount
  • Obesity is a risk factor for this disease
  • Treatments include reducing the number of simple carbohydrates in diet, losing weight and increasing exercise
  • There are also drugs to make insulin more effective on body cells, help the pancreas make more insulin or reduce the amount of glucose absorbed from the gut
• sightedness treatments


  spectacle lenses

  concave lenses spread out the light to treat myopia and convex lenses bring rays together to treat hyperopia

  Contact lenses

  work in the same way as glasses

  Laser eye surgery

  reduce the thickness of the cornea to refract light less to treat myopia or change curvature to refract light more strongly to treat hyperopia
• The process of accommodation:

  To focus on a near object:

  The ciliary muscles contract, The suspensory ligaments loosen, The lens is then thicker and more curved - this refracts the light more

  To focus on a distant object:

  The ciliary muscles relax, The suspensory ligaments tighten, The lens then becomes thinner - light is refracted less
• near objects - ciliary muscles contract, suspensory ligaments loosen

  distant object - ciliary muscles relax, suspensory ligaments tighten
• bright light:

  the circular muscles contract and radial muscles relax to make the pupil smaller- avoiding damage to the retina

  dim light:

  circular muscles relax, radial muscles contract to make the pupil larger- so more light can enter to create a better image.
• kidneys: filter blood, regulate levels of ions and water, Remove waste products such as urea

  • urea is made in the liver through a process called deamination

  1. If the body has more amino acids than it needs, it can convert them into lipids or carbohydrates, which can be stored as an energy source for later.
  2. The downside of this process is that it produces the waste product urea, which has to be excreted by the kidney. 
• water is taken in through foods and liquids and lost through sweat and breathing in the lungs and urine

  water regulation is important:

  cells can shrink if there's not enough water

  cells can burst if there's too much water gained through osmosis
• Anti-diuretic hormone (ADH) controls loss of water as urine.

  • released into pancreas by pituitary gland when a receptor in brain detects too little water in bloodstream
  • It travels in the bloodstream to the kidney tubules
  • increased amount of ADH reaching the tubules increases their permeability to water, so more moves out of the tubule and back into bloodstream
  • leaves with less urine that is more concentrated and less concentrated bloodstream

  negative feedback loop example:

  • concentration of the blood increases/decreases, more/less ADH is secreted reversing change
• consequences of kidney failure:

  poor regulation of ion and water levels

  increase waste products like urea