chapter 5

• The maintenance of constant internal environments, in responsive to external and internal conditions
• 3 main systems


  • Receptors
  • Co-ordination centres
  • Effectors (muscle or glands)
• Receptors


  • Detect a change
• Co-ordination centres


  • Interpret the change
  • Decide what needs to be done
• Effectors (muscle or glands)


  • Carry out the change
  • Restore optimum levels
• Nervous systems and endocrine system carries the signal between receptors, coordination centres and effectors
• Maintaining blood sugar levels

  1. Blood sugar goes low

  2. Pancreas releases glucagon

  3. Glucagon turns into glucose

  4. Blood sugar goes back to normal
• Maintaining blood sugar levels

  1. Blood sugar goes high

  2. Pancreas releases insulin

  3. Blood sugar goes back to normal
• The Brain

  • Cerebral cortex consciousness, memory etc
  • Cerebellum muscle coordination
  • Medulla unconscious activities
• How scientist Study the brain

  1. study people with brain damage

  2. Scanning the brain

  3. Pet scan- radioactive chemicals measuring the

  4. MRI scan- magnetic fields
• Why treating the brain is so difficult?


  • wide range of things that can go wrong.
  • Difficult to diagnose some diseases when alive
  • The brain is delicate, hard to fix
• The eye

  • Cornea-refracts light as it enter the eye.
  • Iris - control how much light enter the pupil
  • Pupil - allows light into the eye
  • Lens - Focus Light on to the retina.
  • Retina- contain the light receptors
  • Optic nerve- carries impulse from the eye to the brain.
  • sclera- protect the eye from damage
  • Ciliary muscle- Change the shape of the lens to focus light on the retina (relax or contract)
  • suspensory ligaments - change the shape of the lens ( loose or lighten).
• In the dark


  • Iris get smaller
  • Radial muscle contract
  • Circular muscle relax
  • pupil get larger - more light enter the eye
  • Eye dilated
• Accommodation

  The eye adjust to focus on close up or far away objects
• Long-sighted

  Light focuses long of the retina corrected = convex lens can’t focus on close objects
• Short-sighted

  Light focuses short of the retina corrected = concave lens can’t focus on far objects
• Thermoregulation

  the control of our internal body temperature.
• Thermoregulatory centre (in the brain)

  • Acts as a thermostat
  • Contains receptors sensitive to the temperature of the blood
  • the skin contains temperature receptors sends nervous impulses to the thermoregulatory centre.
• Warm up

  1. blood vessels constrict - no heat is lost by radiation

  2. erector muscle contract - hair stand up, trap air ( insulator)

  3. muscles contract - cause shivering and it require energy from respiration=heat produce as waste
• Cool down

  1. blood vessels dilated

  2. erector muscle relax - hair lies flat

  3. sweat is produced from sweat glands - evaporates from skin taking heat with it
• The endocrine system

  • Glands - secrete hormones
• Type 1 diabetes

  unknown cause, insulin producing cell are destroyed
• Symptoms (type 1)

  • tiredness, weight loss, extreme thrust, needs the toilet a lot
• Treatment (type 1)

  inject insulin ,reducing sugar in the diet, excercise regularly
• Type 2 diabets

  • can't produce enough insulin, Obesity, liver and muscle cells won't response on it (become resistant to insulin)
• Symptoms (type 2)

  • tiredness, usually feel thirsty, pass urine more often.
• Treatments (type 2)

  1. healthy low sugar diet, regular exercise, monitor their blood sugar concentration.
• How does the kidney filter blood?

  1. the tubule filter the blood as it make it ways through the kidney

  ~ absorb anything small.

  ~ water, urea, ions and glucose

  All of the glucose are re-absorb and some water

  ~ water, ions and urea goes into the urine instead of being re-absorb
• Digestion of protein results in excess amino acids. In the liver, these amino acid are deaminated to form ammonia (toxic). Ammonia converted into urea (less toxic).
• Kidney failure

  • Treatment: kidney transplant and kidney dialysis.
• Dialysis

  • contain dialysis fluid and partially permeable membranes
  • Dialysis fluid contain same useful substances as healthy blood.
  • Urea passed out from the blood into the dialysis fluid.
• Transplant

  • Healthy Kidney from 1 person is transfer to a patient that needs it
  • Mostly from people recently died.
• Dialysis pros and cons

  • pros: cleans the blood Replace kidney‘s job
  • Cons: Time-consuming uncomfortable expensive
• Human reproduction

  • menstrual cycle:
  • average length. 28 days
• Stage 1: menstruation (0-4 days)


  bleeding due to breakdown of uterus lining
• Stage 2 (4-14 days.)


  Iining starts to build up and prepare for fertilised egg
• Stage 3: ovulation (1 day)


  egg being release
• Stage 4 (16-28 days).


  maintaining the lining of the uterus
• follicle


  • when egg is make and release, the follicle turns into corpus luteum
• Secondary sex characterratic.

  • males - pubic hair, growth of testies + penis, growth spurt, increased muscles + broadening of shoulders
  • Females - pubic hair, period, growth spurt, growth of beast, hip widen for childbirth