3.3 the endocrine system

Question 1

Whats the endocrine system?

Answer 1

The endocrine system consists of the tissues (mainly glands) that create and release hormones.

Question 2

What are hormones?

Answer 2

Hormones are chemical messenegrs which coordinate(travelling through bloodstream) different functions in the body; controlling activites in areas such as growth, reproduction, blood solute concentration, blood temperature etc.

Question 3

What are the three types of hormones

Answer 3

• Peptide hormones (consists of short polypeptide chain of amino acids)
• Protein hormones (longer chains of amino acids)
• Steroid hormones (lipid-based hormones)

Question 4

Describe the properties of the peptide hormones.

Answer 4

• Synthesis: require cleavage to activate
• Storage: stored in vesicles
• Solubility: most are polar and travel through the blood
• Receptors: bind to receptors in the cell membrane
  examples: insulin, glucagon, anti-diuretic hormone(ADH)

Question 5

Describe the properties of protein hormone.

Answer 5

• Synthesis: synthesised from tyrosine
• Storage: stored before release
• Solubility: some are polar (water soluable)
• Receptors: some act on cell membrane receptors others act on nuclear membrane
  examples: adrenaline, thyroxine

Question 6

Describe the properties of steroid hormones

Answer 6

• Synthesis: synthesised from cholestrol
• Storage: immediently released into bloodstream
• Solubility: non-polar (lipid soluable)
• Receptors: bind to intracellular receptors
  examples progesteone, oestrogen, testrone

Question 7

What hormones can travel in the cell?

Answer 7

The protein and peptide hormones are often polar and cannot travel into the cell. As they cannot enter they bind to target cell membranes which have complementary receptors to the hormones.

sterioid hormones.are lipid soluable and bring about their effect by travelling into the cell (diffsue through phospholipid bilayer)and binding to internal receptors.

Question 8

What are the major endocrine glands of the human body and their location?

Answer 8

• Hypothamus (brain)
• Pituitary glands (brain)
• Thyroid gland (front of the throat)
• Parathyroid glands (four tiny glands located around the thyroid in the throat)
• Thymus gland (upper chest, behind your breastbone[sternum]).
• Adrenal glands (two small triangle-shaped glands in the upper abdomen)
• Pancreas (high in the abdomen)
• Ovary (female gonad, located lower left and right quadrants of the abdomen)
• Testes (male gonad, located inside the scrotum).

Question 9

What hormones does the pituaitary gland release

Answer 9

• Oxytocin (uterine contractions during childbirth)
• Antidiuretic ADH (reabsorption of water in the kidneys)
• Human growth hGH (grwoth of body cells and tissues)
• Follicle stimulating FSH ( stimulates ovaries and testes
• Luteinising LH( stimulates ovulation [release of eggs] in females and the release of testosteron in males)
• Thyroid-stimulating TSH (stimulates the activity of the thyroid gland

Question 10

What hormones does the thyroid gland release and describe its action.

Answer 10

Thyroxine, which stimulates metabolism and heat production.

Question 11

What hormones does the parathyroid gland release and describe its action.

Answer 11

Parathyroid (PTH), which stimulates the release of calcium from bone into the blood.

Question 12

What hormones does the pancreas release and describe its action.

Answer 12

Insulin and glucagon, loweing blood glucose as well as raising blood glucose.

Question 13

What hormones does the adrenal glands release and describe its action.

Answer 13

Adrenaline, which increases blood sugar, constricts blood vessels and increases heart and breathing rate.

Question 14

What hormones does the ovaries release, and describe its function.

Answer 14

Oestrogen and progestrone, developing female secondary sexual characteristics and maintaing uterine lining.

Question 15

What hormones does the testes release and describe its function.

Answer 15

Testostrone, developing male secondary sexual characteristics, muscle development and controls the sperm production.

Question 16

Why is the pituitary gland called the master endocrine gland?

Answer 16

The pituitary gland is located at the base of the brain and acts like the master controller, releasing hormones which control other endocrine glands e.g. TSH which then stimulates the thyroid gland.

Question 17

What is glucose?

Answer 17

Glucose is an essential for energy supply, and is broken down through both aerobic and anaerobic respiration releasing ATP.

Question 18

Why most glucose be kept between tolerance limits, how can it exceed them?

Answer 18

Glucose must be kept within certain tolerance limits to avoid certain disease.

Homeostatic processes such as negative feedback operate to keep glucose levels between tolerance levels, using both insulin and glucagon (both peptide hormones).

Eating foods(specifcially carbohydrates), drinking sugary drink, fasting and exercise can lead to high blood glucose levels.

Question 19

Why does glucose need insulin?

Answer 19

Insulin’s main job is to move glucose from our bloodstream into the body’s cells to make energy. If you don’t have enough insulin, glucose builds up in your bloodstream rather than getting into your cells to provide energy.

Question 20

Use the stimulus response model to describe the blood glucose regulation.

Answer 20

Cells in the islets of langerhans, in the pancreas have chemoreceptors which are sensitive to glucose concentration in the blood (note there is two cells: alpha and beta cells).

When blood glucose levels are too low, the alpha cells in the pancreas secrete more glucagon (hormone which travels in the blood and can travel to complementary receptors on livers cells. Causing the conversion of Glycogen to glucose.

glycogen stores excess glucose, which can be broken down later, and released into the bloodstream, where the blood glucose levels rise back to normal

When blood glucose levels are too high, beta cells will release more insulin, more insulin binding to muslces and liver cells causes them to absorp and store more glycogen (storage form of glucose), reuslting in a normal blood glucose level.

Question 21

What does insufficient production of insulin lead to?

Answer 21

An insufficent prodution of insulin leads to an accumulation of glucose in the blood and may result in diabetes.

Question 22

What is metabolism?

Answer 22

Metabolism refers to the vast array of biochemical reaction occuring in an organism. Amongst which cell repisration such as which release energy for ATP production and heat are most important.

Question 23

What hormone controls metabolism?

Answer 23

Thyroxine is a hormone produced by the thryoid gland and is secreted into the circulatory system (bloodstream). Acting in most cells to regulate metbaolism, increasng the basal metabolic rate (BMR). As a result thyroxine promotes the generation of heat.

Question 24

Is iodine required for the production of thyroxine.

Answer 24

Iodine is required for the production of thyroxine, a lack of iodine can cause the thyroid to enlarge, causing a condition known as goitre (enlarged thryoid gland).

Question 25

What does a lack of thryoxine lead to?

Answer 25

Lack of thryoxine can lead to slowing of thought and speech, lethargy, sleepiness, decreased appetite and cold intolerance.

Question 26

What can high thryoxine levels lead to?

Answer 26

Too much thyroxine can cause rapid heartbeat, shortness of breath, increased appetite and intolerance to heat.

Question 27

How are blood thyroxine levels mainatained, explain the feeback loop.

Answer 27

• If thyroxine levels fall, receptors in the hypothalamus detect it.
• The hypothalamus secretes thyrotropin releasing hormones (TRH) which stimulates the anterior pituarity gland to release thyroid stimulating hormone(TSH).
• TSH travels through the bloodstream to the thyroid gland which then releases thyrone.

Increased levels of thyroxine increase metabolic rate and thus stimulate energy release for ATP and heat production.

When thyroxine levels fall, hormones receptors detect this and the thyroid gland reverses the stimulus secreting more thyroxine. The stimulus is ‘fed-back’ reversing the initial stimulus.
Thus is a negative feedback loop.

Question 28

Is this a negative or positive feedback loop?

Answer 28

This is an example of negative feedback where increasing thyroxine levels are detected by the hypothalamus and the stimulus is reversed.

Question 29

What is osmosis?

Answer 29

The diffusion of water across a semi-permeable membrane.

Question 30

Whats the homeostatic control of water?

Answer 30

Osmoregulation, maintaining water/ solute balance in cells.

Question 31

What main hormone is used in osmoregulation?

Answer 31

There are at least six seperate hormones which impact osmoregulation in humans, one of them is antiduretic hormone (ADH) which is produced in the hypothalamus and stored before release from the pituarity gland.

Question 32

Water balance be effected by what factors?

Answer 32

Drinking/not drinking water
Consuming foods with high salt balance
Exercise (sweating and exhalation)
Decrease in blood volume caused by bleeding

Question 33

What are examples of stimuli impacting water/solute concentration

Answer 33

• A decrease in blood volume
• A decrease in blood pressure
• Increase in solute concentration in the blood.

Question 34

State reasons why osmoregulation is important for organisms?

Answer 34

Most chemical cannot dissolve without, supports cells and is a important transport medium throughout the body e.g. blood.

Question 35

Describe how osmoregulation works?

Answer 35

• Stimuli are detected by osmoreceptors (a type of chemoreceptor) in the hypothalamus and stretch receptors in the heart and arteries.
• ADH is made in neurons in the hypothalamus and then stored in the pituarity gland. With higher solute concentration more ADH is released into the bloodstream and travels to the kidney tubules (in the nephrons) to reabsorb more water
• Blood volume, pressure and solute concentration are restored

an example of negative feedback

Question 36

Outline the role of the nephron in osmoregulation?

Answer 36

The nephron is the exchange surface of the kidney, specifically the tubules of the nephron are responsible for reabsorbing water back into the bloodstream. By increasing or decreasing the water reabsorbed, this will change the water/solute concentration.

Question 37

State the stimulus, receptor, hormones, effector and respsone in the blood/glucose concentration

Answer 37

Stimulus: Low/high blood sugar
Receptor: Cells in pancreas
Hormones: Glucagon/ insulin
Effector: Muslces/liver
Response: Increase/decrease in blood/glucose

Question 38

State the stimulus, receptor, hormones, effector and respsone in the metabolic rate

Answer 38

Stimulus: Increase/decrease in metabolic rate
Receptor: Hypothalamus/thyroid gland.
Hormones: Thyroxine
Effector: Mitochondira/cells/tissues
Response: increase/decrease in metabolic rate.

Question 39

State the stimulus, receptor, hormones, effector and respsone in osmoregulation

Answer 39

Stimulus: Increase/decrease in solute concentration in the blood
Receptor:Hypothalamus/heart/arterie
Hormones: Antidiuretic hormone
Effector: Tubules in the kidney
Response: Changed absorption rate in the tubules.