CB7 - Control & homeostasis (Hormones)

• What are hormones?

  Chemical messengers that control the growth, differentiation, and metabolism of specific target cells
• What is a gland?

  An organ that releases small chemicals called hormones
• Where are hormones released from?

  A range of endocrine glands releasing them into the bloodstream. These are messengers in the blood stream
• What does it mean to 'secrete'

  To release
• What is homeostasis?

  process by which organisms maintain a relatively stable internal environment
• How does the endocrine system work?

  1. Hormones are secreted by glands and travel through the blood stream.

  2. They connect with a target cell /w the correct receptors.

  3. Hormone stimulates target cell to do something or stop doing something
• What is a target cell?

  Any cell with the correct receptor for the correct hormone.
• What is the pituatary gland?

  ~ It is the 'master gland' that controls all hormones.

  ~ It is located in the brain and it secretes several hormones into the blood in response to body conditions

  ~ These hormones can act on other glands to stimulate more hormones to be released for effects

  ~ This gland secretes FSH, LH, ACTH and growth hormones
• Whata produced in the thyroid gland?

  Thyroxine
• Whats produced in the adrenal gland


  Adrenaline
• Whats produced in the pancreas?

  Insulin & glucagon
• Whats produced in the testes?

  Testostrone
• Whats produced in the ovaries?

  Oestrogen & progestrone
• How can hormone release be affected?

  By negative feedback - when a substance goes below or above normal levels, a response is triggered to get it back to normal.
• Why are hormones known as hormones

  Because they are chemically produced by glands and secreted into the bloodstream to bind to target organs and create an effect.
• Two similarities between the endocrine system and the nervous system

  Similarites:

  ~ Both send messages around the body.

  ~ Both make an effect to the body in a way.
• Two differences between the endocrine system and the nervous system

  Differences:

  ~ Hormone responses are slower and travel slower while nervous impulses are very fast.

  ~ Hormone effects last longer while nervous effects dont last as long.
• What is adrenaline?

  ~ A hormone released by the adrenal glands.

  ~ Its released in response to scary or exciting situations.

  ~ When your brain detects fear or stress it sends nervous impulses to the adrenal glands which secrete adrenaline.

  ~ This triggers mechanisms like faster heart rate that increase the supply of oxygen and glucose to the muscle cells and parts of the brain.
• What are the effects of adrenaline?

  ~Increasing blood glucose conc for increased respiration in muscle cells.

  ~Increasing heart rate so glucose and oxygen can be delivered to muscle cells, and carbon dioxide taken away, from muscles cells more quickly.

  ~Diverting blood flow towards muscles and away from non-essential parts of the body to ensure the reactants of respiration are as available as possible.

  ~Dilating pupils so more light and info can enter the brain.
• How is the blood glucose concentration increased by adrenalin?

  Adrenalin stimulates the liver cells to break down the glycogen cells and convert it into glucose, releasing it into the blood.
• How is the heat rate increased by adrenalin?

  Adrenaline stimulates the heart muscle cells to contract more rapidly; increasing the heat rate & more strongly; increasing the blood pressure, hence more blood is pumped.
• How is the blood flow diverted to muscle cells by adrenalin?

  ~ The diameter of the blood vessels going to the muscles widens, hence more blood flow & allowing for more oxygen and glucose to enter the muscles.

  ~ However, in other blood vessels going to other organs, the diameter narrows, hence constricting blood flow & allowing for less oxygen and glucose to be sent to areas not involved in 'fight or flight'.
• What is metabolism?

  sum of all chemical reactions in the body
• What describes the metabolic rate?

  The speed that the energy stored in food is transferred by reactions that take place in your body to keep you alive.
• What describes the resting metabolic rate?

  The metabolic rate when the body's at rest, in a warm room, and long after the person had a meal. Usually measuring the intake of oxygen and production of CO2.
• Why is BMR measured in a warm room not a cold one?

  Because the body would be using additional energy to warm up in the cold.
• What does thyroxine do generally?

  ~ It regulates metabolism and its controlled by negative feedback as it maintains normal levels in the bloodstream.

  ~ It stimulates the basal metabolic rate (BMR); this is the speed at which chemical reactions occur in the body when it is at rest, the more thyroxine, the quicker the rate.
• What are the stages of producing thyroxine when the levels are too low? (How the negative feedback works for thyroxine)

  1. The hypothalamus produces TRH

  2. TRH production also stimulates TSH production from pituitary gland.

  3. Then the TSH acts on the thyroid to produce thyroxine.

  4. As the thyroxine levels go normal they inhibit the release of TRH and the production of TSH to prevent too much thyroxine being produced.

  
• What does thyroxine do mainly?


  It causes the heart cells to contract more rapidly and strongly. It also increases the rate proteins and carbs are broken down in cells.
• What happens if theres too much thyroxine being produced and it can't be controlled?

  Can lead to an increased heart rate continuously along with weight loss as the fats and carbs would already be synthesised.
• What happens if theres too little thyroxine being produced and it cant be controlled?

  Can lead to increased body mass as the fats and carbs aren't being broken down proerly and also lead to fatigue as energy is slowly being produced at a slow metabolic rate.