Homeostasis

• Homeostasis


  the regulation of internal conditions of cells or organisms to maintain optimum conditions for function in response to internal and external changes
• Homeostasis in humans:

  used to keep blood glucose concentration, body temperature and water level constant
• Homeostasis consists of automatic control systems so internal conditions of body are constant
• Receptors -> detect a stimulus -> pass information/ electrical impulses to the co-ordination centre e.g. brain & spinal cord -> send instructions to the effector which job is to carry out the response
• Centralised Nervous System


  brain + spinal cord, acts as a coordinator
• The nervous system allows us to react to surroundings and co-ordinate our behaviour - e.g. reflex arc - no decision-making, the unconscious part of the brain working, rapid response, save from danger
• Sensory -> relay -> motor neurones


  Electrical impulses passes to each of these neurones and the synapse diffuses a chemical which is diffused to the next neurone and triggers another electrical impulse
• Endocrine system

  consists of many glands and secretes hormones directly to the bloodstream
• Hormones

  chemicals which are carried in the bloodstream
• Difference between the Nervous system and Endocrine System

  NS: fast but short-lived

  ES: slow effect but long-lived
• Pancreas gland

  release hormones - controls the blood glucose concentration levels
• OVARIES AND TESTES ARE GLANDS
• Ovaries and testes

  release oestrogen and progesterone which is involved in puberty and reproduction
• Thyroid gland

  produce hormones which maintains the basal metabolic rate and involved in growth
• Basal Metabolic Rate


  shows how rapid the body's reactions take place
• Adrenal gland

  release adrenaline when in fear or stressed - target organ is the heart
• Pituitary Gland

  MASTER GLAND - release different hormones into the blood depending on the conditions and those hormones act on other glands and cause other hormones to be released - trigger many effects in the body
• Which gland controls the blood glucose concentration?

  Pancreas - it aims to keep it constant
• What happens when blood glucose level rises?

  Pancreas detects - produces insulin - travels in the bloodstream all around the body and triggers cells to take up glucose from blood to reduce the glucose levels - insulin triggers liver and muscle cells to store excess glucose as a store called GLYCOGEN
• Why can blood glucose levels fall to very LOW levels?

  VIGOROUS exercising

  NOT eating
• What happens if glucose levels are low?

  pancreas senses it - produces hormone GLUCAGON which travels into bloodstream and triggers liver cells to convert glycogen BACK into glucose and causes levels to go normal
• Diabetes cause:

  if blood glucose control doesn't work effectively
• Type 1 Diabetes

  pancreas doesn't product enough/sufficient insulin - can be seen on a graph (BG level stays high)
• Treatment for Type 1:

  monitor their BG concentration

  inject them with insulin if BG level is too high

  if too high, can also use medication

  can get a pancreatic cell transplant
• Type 2 Diabetes

  when body is resistant to the insulin/body stops responding to the insulin - BG levels therefore rise too high
• How is Type 2 diabetes treated?

  Exercising

  Active

  Eating healthy/diet with controlled level of carbs

  CHANGE LIFESTYLE
• Insulin and glucagon have opposite effects on the BG concentration - meaning they form a negative feedback cycle
• What does reproductive hormones produce?

  secondary sexual characteristics
• What do men produce (secondary S.C)?

  Hormone testosterone from the testes - stimulates to produce sperm
• What do women produce (Secondary S.C)?

  Ovaries produce hormone oestrogen - stimulates to produce egg
• Ovulation

  In puberty, eggs start to mature and every 28 days, one egg is released
• FSH (Follicle Simulating Hormone)

  causes egg to mature in the ovary
• LH (Luteinising Hormone)


  causes egg to be released - OVULATION'
• Oestrogen and progesterone (menstrual cycle)

  maintain uterus lining incase egg fertilises and implants
• Describe how hormones work in the menustral cycle? Step 1

  FSH released by pituitary gland which travels in blood to ovaries - causes egg to mature - ATST the FSH triggers ovaries to make oestrogen and stops master gland from releasing FSH
• Describe how hormones work in the menustral cycle? Step 2

  Master gland releases LH which triggers ovulation and egg is released
• Describe how hormones work in the menustral cycle? Step 3

  Once ovary released the egg, ovary produces progesterone - stops the master gland from releasing FSH + LH - prevents more eggs from maturing and keeps uterus lining thick incase egg implants
• Describe how hormones work in the menustral cycle? Step 4

  If no fertilisation happens - level of progesterone falls - uterus lining and egg is released - PERIOD!
• Contraception

  ways to prevent fertilisation
• Contraceptive pill

  contains hormone that prevents body from producing FSH as that causes egg to mature - highly effective - if you forget to take it daily it won't be effective - doesn't protect from STIs - can get blood clots or breast cancer