HOMEOSTASIS

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  • Created by: Lula207
  • Created on: 23-10-19 17:23
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  • Homeostasis - the regulation of internal conditions to maintain optimum conditions for enzyme action and cell function.
    • Principles
      • The nervous system has nerve impulses which are electrical. these impulses are rapid and precise, and carried to specific locations
      • The endocrine system  sends a chemical hormone through the blood to a location. it is slower than the nervous system.
      • Negative feedback is where a change made to a system is reversed.
    • Nervous impulses
      • The nervous systems send out electrical impulses to regulate internal conditions and react to stimuli.
      • A neurone is a nerve cell which carries the impulse. A  bundle is called a nerve.
      • Stimulus-receptor-sensory neurone-brain-spinal cord-motorneurone-effector-response
        • A sensory neurone stays internal and  a motor neuron carries the message to external factors.
    • Reflex actions
      • Rapid, automatic responses to stimulus
    • The endocrine system
      • Made up of glands that secrete hormones into the blood to a target organ. this then has receptors .
        • Hormones are chemical messages carried in the blood
      • Hormones
        • Pituitary-Brain-controls growth, thyroid gland, sex hormones
        • Thyroid-controls metabolism
        • Pancreas-glucose levels
        • Adrenal-fight or flight
        • Ovaries/Testes-sexual development
      • KEYWORDS
        • Glucose-soluble, broken down carbs, respiration
        • Glycogen-stored glucose, insoluble
        • Glucagon-hormone secreted by pancreas, releases blood glucose
        • Insulin- hormone secreted by pancreas-increases blood glucose.
        • Liver-stores glucose as glycogen
      • Diabetes - separate sheet
    • Adrenalin and Thyroxine
      • Adrenaline- produced when body is in fear or stress. Fight or flight. after response, broken down by liver-extra glucose released. effects include, faster heart rate, energy.
      • Thyroxine- secreted by thyroid gland into blood. Regulates metabolism, heart, digestion, muscle, brain development and bone maintenance.
    • Menstrual cycle
      • Hormones involved: FSH,LH,Progesterone,Oestrogen
        • FSH causes the follicle to develop into a mature egg in the ovaries. Stimulates ovaries to produce oestrogen.
        • LH triggers ovulation and causes oestrogen production to stop. LH falls after ovulation.
        • Progesterone maintains the uterus lining and stops release of LH. Secreted by empty egg follicle.
        • Oestrogen causes the pituitary gland to stop FSH production and start producing LH. Causes uterus lining to thicken
      • Hormone interaction with menstrual cycle- on other sheet.

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