B5 - Homeostasis and Response

• Homeostasis

  A way to monitor changes INSIDE and OUTSIDE the body AND respond to them
• Central Nervous System

  Consists of the brain + spinal cord
• Peripheral Nervous System

  Consists of nerve cells (carries the information to the CNS)
• Receptors

  Detects stimuli e.g. skin receptors + light receptors
• Effectors

  Respond to impulses and bring about a change e.g. Muscles + Glands
• Muscles..

  CONTRACT
• Glands..

  SECRETE
• Sensory Neurons

  Carry info as electrical impulses from receptors to CNS
• Motor Neurons

  Carry electrical impulses from CNS to effectors
• Why is it important that receptors receive stimuli?

  > Respond quickly to changes

  > Avoid dangers
• Synapse

  Gaps in-between neurons to ensure the signals travels in ONE DIRECTION
• Relay Neurons

  Nerve cell that carries electrical impulses from the sensory neurones to the motor neurons
• Reflex

  Automatic and rapid response
• Presynaptic neurons contain?

  Chemicals
• How does the chemicals move across the synapse to the receptors?

  Through diffusion
• How is information transferred in a neurone?

  Electrical Impulses
• Why are conscious actions SLOWER than reflexes

  The electrical impulse has to travel to the brain and back
• RP - Investigating Reaction Time

  1. Person A holds out their hand with a gap between their thumb and first finger
  2. Person B drops a meter ruler without telling Person A and they must catch it as quickly as they can
  3. Repeat this several times and calculate a mean distance that the ruler fell

  • The further down the ruler is caught = slower their reaction time
• What organ monitors the blood glucose levels?

  Pancreas
• Negative Feedback

  Opposite response to changes in the body
• What cells convert glucose->glycogen

  Liver + Muscle cells
• The pancreas produces what hormone?

  Insulin
• What breaks down when glucose levels are too low?

  Glycogen
• Where is glycogen broken down?

  Liver + Muscle cells
• What happens when glucose enters the blood?

  Blood glucose levels INCREASE
• Type 1 Diabetes

  Pancreas does NOT produce enough INSULIN, resulting in high blood glucose
• Type 2 Diabetes

  Body cells do NOT respond to INSULIN
• The Nervous System

  • Faster
  • Short acting
  • Uses neurones
  • Sends electrical impulses
• The Endocrine System

  • Slower
  • Long acting
  • Uses bloodstream
  • Sends hormones
• Where is oestrogen produced and stored?

  Ovaries
• What is day 14 of menstrual cycle?

  Ovulation
• Menstruation

  When the egg cell is matured and is released
• Oestrogen

  Thickens uterus lining
• Progesterone

  Maintains thickness of uterus lining
• FSH

  Makes eggs mature in the ovary
• LH

  Stimulates release of an egg
• Contraception

  Form of birth control, preventing a female from becoming pregnant
• Pros and cons of the pill

  PROS: highly effective

  CONS: MUST be taken everyday and side-effects
• Pros of the injection

  PROS: more convenient than the pill
• CONS to all hormonal methods

  do not protect against STI