biology 2

the co-ordination and control chapter

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coordination and control part 1

responding to change;

  • the nervous system has receptors to detect stimuli.
  • the receptors are found in sense organs, the eye, ear, nose, tongue and the skin.
  • light simulates the eye and electrical impulses then pass to the brain along neurones (nerve cells).
  • other stimuli include sound chemicals, temp change, tough or pain.
  • the brain coordinates responses to many stimuli.
  • the brain and spinal hord form the centeral nervous system (CNS) 
  • nerves contain nurones:
  • sensory neurones carry impuleses from receptors to the CNS.
  • Motor neurones carry impulses from the CNS to the effector organs which may be muscles or glands.
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coordination and control part 2

reflex actions:

the main steps are:

  •  receptor detects a stimulus (e.g a sharp pain).
  • a sensory nurone transmits the impulse to the CNS.
  • a relay nurone passes the impulse on.
  •  a motor nurone is stimulated.
  • the impulse passes to an effector (muscle or gland)
  • action is taken (the response
  • the gaps between the nurones are called synapses.

hormones and the menstral cycle

  • FSH is made in the pituitary gland- this makes the egg mature.
  • oestrogen is produced by the ovaries and stops any more FSH being made.
  • this stimulates LH to be made and stimulates the womb linng. LH releases the egg.
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coordination and control part 3

the artificial control of fertility:

  • the contraceptive pill (oral contraceptive) may conatin oestrogen and progesterone. some pills are progesterone only pills and have fewer side effects.
  • these pills stop the production of FSH so no eggs are matured.
  • if a woman cannot produce mature eggs FSH and LH can be given. ths is known as fertility treatment. the FSH causes the egg to mature and LH releases it.

controling conditions

  • the body controls its internal enviroment. internal condition that include: water content, ion content, temprature and blood sugar level. 
  • water leaves the body as we breath, sweat and pee.  we loose ions in our sweat and the urine.
  • the level if sugar in our bodies is contolled by the pancreas.
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coordination and control part 4

hormones nad the conrol of plan growth;

  • plants are sensitive to gravity, light and moisture.
  • plants shoot towards light (phototropism)
  • roots grow towards gravity (gravitropism)
  • roots also grow towards water.
  • auxin is a hormone that controls phototropism and gravitropism.
  • un equal auxin can cause un equal growth and bending stems.

using hormones;

  • plant hormones can be used by gardeners and farmers on their crop.
  • weed killers are used to kill unwanted plants.
  • when cuttings are taken from plants, hormones are used to encourage roots to grow before the cutting is planted.
  • some hormones are used to encourage fruit to ripen.
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