5 - Homeostasis and response

• Enzymes


  proteins that speed up chemical reactions and act as biological catalysts
• Glucose


  the sugar needed for respiration. It is carried in the blood
• Body temperature


  37 degrees centigrade
• Blood water levels


  the amount of water in the blood, this needs to be kept constant
• Pancreas


  an organ next to our stomach that produces enzymes and the hormone insulin that controls blood sugar
• The endocrine system is composed of...

  ...glands which secrete chemicals called hormones directly into the bloodstream
• Structure of the endocrine system

  Look at this diagram. You must know where the following are on the body: pituitary gland, pancreas, thyroid, adrenal gland, ovary, testes

  
• Describe the endocrine system

  1. Glands secrete chemicals directly into the bloodstream

  2. The blood carries the hormones to a target area where it produces an affect

  3. Compared to the nervous system the effects are slower but last for longer
• Hormone


  a chemical messenger that is produced in a gland and travels in the blood to a target organ
• Target organ


  the organ that a hormone has an effect on
• Pituitary gland


  1. A gland in the brain that secretes several hormones into the blood in response to body conditions

  2. These in turn act on other glands to stimulate other hormones to be released to bring about effects.
• Master gland


  the pituitary gland in the brain is known as this because it monitors and controls so many conditions
• Thyroid


  a gland in the neck that produces the hormone thyroxine that controls metabolism
• Adrenal glands


  two glands on the kidneys that produce the hormone adrenaline that is involved in flight or fight
• Ovary


  (cis) women have two of these, they produce the hormones oestrogen and progesterone and are involved in maturing and releasing eggs
• Testes


  (cis) men have two of these and they produce the hormone testosterone. Sperm are also made here
• Insulin


  a hormone released by the pancreas when blood concentration is too high that causes glucose to move from the blood into cells
• Describe what happens when the blood glucose concentration is too low.

  1. The pancreas produces glucagon

  2. Which causes glycogen to be converted into glucose and released into the blood
• Describe what happens when the blood glucose concentration is too high.

  1. Pancreas produces insulin

  2. Which causes glucose to move from the blood into cells
• Glycogen


  this is how glucose is stored in the liver and muscles
• Liver


  A large organ where glucose is stored as glycogen. It also make bile
• Type 1 diabetes


  A disease people suffer from where the pancreas does not produce enough insulin. People with this disease need to have insulin injections or an insulin pump
• Type 2 diabetes


  A disease people suffer from if their cells no longer respond to insulin. It can be treated with a carbohydrate-controlled diet and an exercise regime. Obesity is a risk factor.
• Glucagon


  A hormone released by the pancreas when the blood sugar levels are too LOW, it causes glycogen to be converted into glucose and released into the blood
• Negative feedback cycle


  where a change in something brings about a process that causes the opposite effect - e.g. controlling blood sugar. It keeps levels constant
• Thyroxine


  A hormone released by the thyroid gland stimulates the basal metabolic rate. It is important in growth and development
• Thyroid gland


  a gland in the neck that produces thyroxine
• Adrenaline


  A hormone released from the adrenal glands in times of fear or stress. It increases the heart rate and boosts the delivery of oxygen and glucose to the brain and muscles, preparing the body for 'fight or flight'.
• Flight or fight


  A response caused by adrenaline that causes muscles to get ready to either run away from danger or to fight it off
• Basal metabolic rate


  The rate of metabolism in the body
• How is excess glucose stored?

  It is converted to glycogen and stored in the muscles and liver
• Thyroxine levels are controlled by...

  ...negative feedback
• Homeostasis


  The regulation of internal conditions of a cell or organism to maintain optimum function in response to internal and external changes

  
• Homeostasis maintains optimum conditions for...

  ...enzyme action and all cell functions
• In the human body, homeostasis includes control of...

  ...blood glucose concentration

  Body temperature

  Water levels
• What does the nervous system enable humans to do?

  React to their surroundings and coordinate their behaviour
• What do all control systems contain?

  Receptors

  Coordination centres

  Effectors
• Receptor


  Cells which detect stimuli (changes in the environment)

  
• Coordination centre


  Recieves and processes information from receptors (this includes the brain, spinal cord and pancreas)

  
• Effectors


  Muscles and glands which bring about responses that restore optimum levels