AQA B5 - Homeostasis and Response (excluding controlling fertility , adrenaline and thyroxine)

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  • Created by: Richoo123
  • Created on: 17-10-17 17:03
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  • B5 - Homeostasis and Response
    • Homeostasis
      • This is the regulation system to maintain a stable internal environment in response to external and internal changes
      • There are automatic control systems in the body
        • These include nervous and hormonal communication systems
          • There are systems to control body temp, blood glucose level and amount of water in the body
      • Negative Feedback works to keep internal environment stable.
        • Whenever something gets too high or too low, body uses negative feedback to combat this
          • Increase - Receptor detects a stimulus
            • The coordination centre (Central Nervous System) receives information and organises a response
              • An effector is triggered which produces an response to restore optimum level so the level decreases.
          • receptor detects stimulus is too low
            • Coordination centre receives information and triggers a response via an effector which restores the increase to optimum level.
    • The Nervous System
      • Central Nervous System is the brain and spinal cord, this is connected to body by sensory and motor neurons
        • sensory neurons carry electrical impulses from receptors - CNS
        • Motor Neurons carry electrical impulses from CNS to effectors
        • Effectors are Muscles and Glands
          • The difference between the nerve  system and hormonal system is
            • Nerves - fast acting , Hormones - slow acting
            • Nerves - act for short time, Hormones - last for long time
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    • Synapses and Reflexes
      • Synapses are gaps between neurons (a gap between 2 neurons) where the nerve signal is transferred by chemicals across the gap via diffusion.
      • Reflexes are rapid automatic responses to a stimulus to reduce chances of injury
        • Reflex actions don't involve the conscious part of the brain
        • Passage of information from receptor to effector is called the reflex arc.
      • When a stimulus is detected by receptors, impulses are sent along the sensory neurone to relay neurone
        • The signal moves along the relay neurone through synapses until the impulses reach the motor neurone
          • The impulses travel along the motor neurone to the effector
    • The Endocrine System
      • This is the hormonal system and releases hormones into blood
        • The difference between the nerve  system and hormonal system is
          • Nerves - fast acting , Hormones - slow acting
          • Nerves - act for short time, Hormones - last for long time
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      • Pituitary Gland, Thyroid, Ovaries, testes, Adrenal Glands, Pancreas
      • The pituitary gland is known as the master gland a the hormones secrete from it act on other glands to secrete hormones.
    • Controlling Blood Glucose
      • If blood glucose level is too high
        • Insulin secreted by pancreas
          • Now there is too much glucose as well as insulin
            • Glucose moves into liver and muscle cells
              • Insulin causes liver to convert glucose into glycogen
        • Insulin causes liver to convert glucose into glycogen
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      • If glucose level is too low , glucagon is added
        • Glucagon is secreted by pancreas
          • Too little glucose as well as glucagon
            • Glucose is released by liver into the blood
              • Glucagon causes liver to turn glucagon into glucose
        • Glucagon causes liver to turn glucagon into glucose
      • Type 1 and Type 2 diabetes
        • Ttpe 1
          • Pancreas produces little or no insulin they may have to take injections of insulin throughout the day , this is to make sure glucose is removed from the blood once food is digested.
        • Type 2 diabetes - this is where someone becomes resistant to their own insulin. insulin is still produced but cells don't respond to it, this can lead to a sharp increase in blood glucose level. Overweight and obesity is a huge factor in this.
    • Puberty and the Menstrual Cycle
      • Stage 1 (day 1 -4) the lining breaks down
        • stage 2 (day 4 -14) the lining builds up again ready to receive a fertilised egg
          • Stage 3 (day 14-21) at around day14 an egg is released from the ovaries , this is called ovulation)
            • Stage 4 ( day 21-28)if no egg has landed on the lining of the uterus by day28 , the ling breaks down and whole cycle repeats.
      • FSH(follicle stimulating hormone) this is produced in pitutarty gland and causes an egg to ature in an ovary. Stimukates ovaries to produce oestrogen
        • LH (luteinising Hormone) is responsible for the release of an egg. produced by pituitary gland
          • Oestrogen  - produced in ovaries, causes lining of the uterus to grow, Stimulates relase of LH and stops release of FSH
            • Progesterone - produced in ovaries by remains of follicle after ovulation , maintains lining of wall during 2nd half of the cycle , if level of progesterone falls, lining breaks down. Stops release of LH and FSJ

Comments

Natalie

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Thank you so much for this, This topic is my weakest and this has really helped me to remember the key bits of the information

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