Coordination and Response in Humans

Coordination and Response in Humans

1. Homeostasis

   • The ability of an organism to maintain a constant internal environment in response to changing environmental or internal conditions
   • Negative feedback
     • If a particular variable (e.g. temperature) moves away from its normal value, different mechanisms work together to bring it back to the norm

2. Thermoregulation

   • Heat given off by
     • F - Blood flow in capillaries increases
       • Vasodilation
     • D - Hair muscles relax. Hairs lie flat so heat can escape.
     • E - Sweat secreted by sweat glands. Cools skin by evaporation.
     • Skeletal muscles shiver - energy released due to increased movement
   • Heat conserved by
     • C - Blood flow in capillaries decreases.
       • Vasoconstriction
     • A - Hair muscles pull hairs on end.
     • B - Erect hairs trap air.
   • Thermoregulatory centre in brain
     • receptors which are sensitive to temperature of blood flowing through the brain
     • Impulses from skin recepors

3. Nervous system

   • Receptors detect a stimulus
     • Sensory neurones carry electrical impulses to spinal cord
       • Relay neurones carry the impulses in the spinal cord
         • Motor neurones carry the impulses to the effector
           • Effectors carry out the response
           • Reflex Arc - Sensory, Relay, Motor
       • sticky out circle means sensory
   • Responds to change
     • Fast, short lived response
   • Central Nervous System decides what to do
   • Effectors are a muscle or gland
     • NOT a part of nervous system

4. Hormones

   • Responds to change
     • Slow, long lasting response
   • ADH
     • Increased permeability of kidney tubules to water, so more water is reabsorbed and less urine is produced
       • Pituitary gland
   • Adrenaline
     • 'Fight or flight' hormone, increases heart and breathing rate, diverts blood flow to skeletal muscles and brain
       • Adrenal glands
   • Insulin
     • Produced when blood glucose level increases. Enables the liver to convert glucose to glycogen for storage.
       • Pancreas
   • Testosterone
     • Development of male secondary sexual characteristics
       • Testes
   • Oestrogen
     • Development of female secondary sexual characteristics, control of the menstrual cycle
       • Ovaries
   • Progesterone
     • Maintains the uterus lining (endometrium) during pregnancy
       • Ovaries

5. The Eye

   • Iris Reflex
     • Bright Light
       • Circular muscles contract, Pupil constricts, Less light enters eye
     • Dim Light
       • Radial muscles contract, Pupil dilates, More light enters eye

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