Coordination and Response in Humans

Homeostasis
1. The ability of an organism to maintain a constant internal environment in response to changing environmental or internal conditions
2. Negative feedback
  1. If a particular variable (e.g. temperature) moves away from its normal value, different mechanisms work together to bring it back to the norm
Thermoregulation
1. Heat given off by
  1. F - Blood flow in capillaries increases
    1. Vasodilation
  2. D - Hair muscles relax. Hairs lie flat so heat can escape.
  3. E - Sweat secreted by sweat glands. Cools skin by evaporation.
  4. Skeletal muscles shiver - energy released due to increased movement
2. Heat conserved by
  1. C - Blood flow in capillaries decreases.
    1. Vasoconstriction
  2. A - Hair muscles pull hairs on end.
  3. B - Erect hairs trap air.
3. Thermoregulatory centre in brain
  1. receptors which are sensitive to temperature of blood flowing through the brain
  2. Impulses from skin recepors
Nervous system
1. Receptors detect a stimulus
  1. Sensory neurones carry electrical impulses to spinal cord
    1. Relay neurones carry the impulses in the spinal cord
      1. Motor neurones carry the impulses to the effector
        Effectors carry out the response
        Reflex Arc - Sensory, Relay, Motor
    2. sticky out circle means sensory
2. Responds to change
  1. Fast, short lived response
3. Central Nervous System decides what to do
4. Effectors are a muscle or gland
  1. NOT a part of nervous system
Hormones
1. Responds to change
  1. Slow, long lasting response
2. ADH
  1. Increased permeability of kidney tubules to water, so more water is reabsorbed and less urine is produced
    1. Pituitary gland
3. Adrenaline
  1. 'Fight or flight' hormone, increases heart and breathing rate, diverts blood flow to skeletal muscles and brain
    1. Adrenal glands
4. Insulin
  1. Produced when blood glucose level increases. Enables the liver to convert glucose to glycogen for storage.
    1. Pancreas
5. Testosterone
  1. Development of male secondary sexual characteristics
    1. Testes
6. Oestrogen
  1. Development of female secondary sexual characteristics, control of the menstrual cycle
    1. Ovaries
7. Progesterone
  1. Maintains the uterus lining (endometrium) during pregnancy
    1. Ovaries
The Eye
1. Iris Reflex
  1. Bright Light
    1. Circular muscles contract, Pupil constricts, Less light enters eye
  2. Dim Light
    1. Radial muscles contract, Pupil dilates, More light enters eye

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Coordination and Response in Humans

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