Homeostasis

• How are nerve cells adapted to their jobs:

  • Long axon - increases travel distance.
  • Myelin sheath - stops electrical nerve signals leaking out.
  • Dendrites - Transfers electrical messages.
• 2 types of effectors:

  • Muscels, contract.
  • Glands, release hormones.
• Co-ordination centers are loacted in the:

  • Brain.
  • Spinal Cord.
• Negative feedback reverses the effect of the stimulus and returns it back to it's original state.
• Role of sensory neurone - transfer signal from receptor to CNS.

  Role of motor neurone - transfer signal from the CNS to an effector.

  Role of relay neurone - transfer signal from sensory neurone to motor neurone.
• Pathway of reflex arc:

  Stimulus -> receptor -> sensory neurone -> relay neurone -> motor neurone -> effector -> response.
• Pitiuary gland (loacted in near the brain) - releases multiple hormones - sends signals to other glands to release hormones.

  Thyroid gland (located in neck) - releases thyroxine - regulates rate of metabolism .

  Adrenal glands (located on top of kidneys) - releases adrenaline (only when we are startled) - increases heart rate.

  Pancreas (located in front of kidneys) - produces insulin - regulates blood glucose conc.
• Differences between nervous and endocrine system:

  • Endocrine system relies on hormones and is transported by the blood stream, whereas , nervous system relies on electrical impulses and is transported by nerve cells.
  • Hormones spread more slowly which means thier effects last longer , whereas , electrical impulses in nervous system are spread very fast meaning thier effects don't last long.
  • Hormones spread aorund the whole body (general), whereas , nerve impulses are sent to one specific area (precise).
• Menustrual Cycle (period):

  • Stage 1 (menustration), period of bleeding as uterus lining is breaking down.
  • Stage 2, building up of uterus lining.
  • Stage 3 (ovulation), release of egg from the ovaries.
  • Stage 4, maintenance of uterus lining.
• Lutenising hormone (LH) is the hormone that stimulates the egg to be released.
• Follicle stimulating hormone is the hormone that stimulates the egg follicle to mature.
• Progesterone is the hormone used to maintain the lining of the uterus.