5.2 HORMONAL COMMUNICATION

Question 1

What hormones does the pituitary gland secrete?

Answer 1

The pituitary gland secretes ADH, FSH, LH and growth hormones.

Question 2

What hormones does the pineal gland secrete?

Answer 2

The pineal gland secretes melanin for sleep cycles and hormones to initiate puberty.

Question 3

What hormones does the thyroid gland secrete?

Answer 3

The thyroid secretes thymosisn.

Question 4

What hormones does the adrenal gland secrete?

Answer 4

The adrenal gland secretes adrenaline.

Question 5

What hormones does the pancreas secrete?

Answer 5

The pancreas secretes insulin and glucagon in the control of blood glucose concentration.

Question 6

What hormones do the ovaries secrete?

Answer 6

The ovaries secrete oestrogen and progesterone.

Question 7

What hormones do the testes secrete?

Answer 7

The testes secrete testosterone.

Question 8

What are hormones?

Answer 8

Hormones are substances secretes by an endocrine gland carried in the blood plasma to another part of the body.

Question 9

What are steroid hormones?

Answer 9

Steroid hormones:
- lipid soluble (pass through plasma membrane)
- bind to steroid hormone receptors in cytoplasm or nucleus forming a hormone-receptor complex
- complex acts as a transcription factor either facilitating or inhibiting the transcription of a specific gene

Question 10

What are non-steroid hormones?

Answer 10

Non-steroid hormones:
- hydrophilic so cannot pass directly through plasma membrane
- bind to specific receptors on plasma membrane or target cell
- binding triggers a cascade reaction mediated by secondary messengers

Question 11

What are target cells?

Answer 11

Target cells are cells that have receptors embedded in the plasma membrane that are complimentary in shape to specific hormone molecules.

Question 12

What is the difference between endocrine and exocrine glands?

Answer 12

Endocrine glands secretes substance to the inside (like the blood) and exocrine glands secrete substances into ducts.

Question 13

What is hormone action?

Answer 13

Hormonal action:
1. secreted from endocrine
2. transported in blood plasma
3. diffuses out of blood
4. binds to specific receptors on membrane or in cytoplasm of target cells
5. once bound, hormone stimulates target cells to produce a response

Question 14

What are the regions of adrenal glands?

Answer 14

Adrenal glands:
- capsule = thin, outer, connective tissue
- adrenal cortex = outer region, produces essential hormones (e.g cortisol, aldoesterone)
- adrenal medulla = inner region, produce non-essential hormones (e.g adrenaline)

Question 15

What is the exocrine gland of the pancreas?

Answer 15

Exocrine gland:
- exocrine glandular tissues makes up most of the pancreas to produce digestive enzymes and alkaline pancreatic juice
- enzymes and juice are secreted into ducts which lead to the pancreatic duct
- then released in duodenum

Question 16

What is the endocrine gland of the pancreas?

Answer 16

Endocrine gland:
- pancreas responsible for production of insulin and glucagon
- insulin and glucagon secreted from beta and alpha cells in the islets of langerhans

Question 17

How do you identify the exocrine and endocrine glandular tissue of the pancreas?

Answer 17

Islets of langerhans - lightly stained - large, spherical clusters - endocrine
Pancreatic acini - darker stained - small, berry-like clusters - exocrine

Question 18

What are islets of langerhans?

Answer 18

Islets of langerhans:
- within islets there are alpha cells that produce and secrete glucagon and beta cells that produce and secrete insulin
- beta cells are most abundant
- alpha cells are larger
- capillaries are required to transport the hormones
- a differential stain (e.g immunoperoxidase) is used to identify alpha and beta cells

Question 19

How does immunoperoxidase staining work?

Answer 19

Immunoperoxidase:
- antibody to glucagon identifies alpha cells
- antibody to insulin identifies beta cells

Question 20

What is somatostatin?

Answer 20

Somatostatin is produced by delta cells and prevents the production of other hormones and stop the unnatural rapid reproduction of cells.

Question 21

What are the adaptations of alpha and beta cells?

Answer 21

Adaptations of alpha and beta cells:
- contain many ribosomes and RER to efficiently manufacture protein hormones
- also contain a large number of golgi apparatus involved in packaging the hormones into vesicles, the hormones are then secreted by exocytosis from secretory vesicles
- as the cells are very active, they contain a large number of mitochondria for ATP production

Question 22

What is the importance of regulating blood glucose?

Answer 22

Importance in regulating blood glucose:
- glucose effects osmotic properties of cells
- too much glucose = decrease water potential of blood plasma
- too little glucose = increase water potential of blood plasma
- low levels of glucose reduce the rate of respiration
- normal blood glucose conc = 90mgcm3

Question 23

What is the process of insulin secretion from beta cells?

Answer 23

Insulin secretion from beta cells:
1. cell membrane has potassium and calcium voltage - gated ion channels
2. the potassium ion channels are normally open so potassium ions flow out
3. when blood glucose level is high the glucose moves into the cell
4. glucose is metabolised to produce ATP in the mitochondria
5. the ATP closes the potassium ion channels
6. the accumulation of potassium ions alters the potential difference across the membrane - the inside becomes less negative (from -70mv to -30mv)
7. the change in potential difference (depolarisation) opens the calcium ion channels
8. calcium ions cause the vesicles of insulin to fuse with the cell membrane, releasing insulin by exocytosis

Question 24

What is glycogenesis?

Answer 24

Glycogenesis is the formation of glycogen from glucose.

Question 25

What is glycogenolysis?

Answer 25

Glycogenolysis is when glycogen stored in the liver and muscles is converted into glucose.

Question 26

What is gluconeogenesis?

Answer 26

Gluconeogenesis is the process of synthesising glucose in the body from non-carbohydrate sources.

Question 27

What is the ‘fight or flight’ response?

Answer 27

The fight or flight response is an instinct that all mammals possess. When a potentially dangerous situation is detected, the body automatically triggers a series of physical responses. These are intended to help mammals survive by preparing the body to either run or fight for life.

Question 28

How is the fight or flight response triggered?

Answer 28

Flight or fight response triggered:
1. a threat is detected by the autonomic nervous system, the hypothalamus communicates with the sympathetic nervous system and the adrenal-cortical system
2. sympathetic nervous system uses neuronal pathways to initiate body reactions whereas the adrenal-cortical system uses hormones in the bloodstream
3. the combined effects of these two systems triggers the fight or flight response

Question 29

What does the sympathetic nervous system do during the fight or flight response?

Answer 29

During the fight or flight response, the sympathetic nervous system sends out impulses to glands and smooth muscles and tells the adrenal medulla to release adrenaline and noradrenaline into the bloodstream. These hormones cause several changes in the body, including an increased heart rate.

Question 30

What does the adrenal-cortical system do doing the fight or flight response?

Answer 30

During the fight or flight response, the adrenal-cortical system activates the pituitary gland to secrete the hormone ACTH, which arrives at the adrenal cortex and releases approximately 30 hormones which have longer term action.

Question 31

What physiological responses does the fight or flight response trigger?

Answer 31

Physiological responses triggered by fight or flight response:
. heart rate increases - to pump more oxygenated blood around the body
. pupils dilate - to take in as much light as possible for better vision
. arterioles in skin constrict - more to major muscle groups, brain, heart and muscles of ventilation
. blood glucose level increases - increase respiration to provide energy for muscle contraction
. smooth muscle of airways relaxes - to allow more oxygen into lungs
. non-essential systems (like digestion) shut down - to focus on emergency functions
. difficulty focusing on small tasks - brain solely focused only on where threat is coming from

Question 32

What is the function of adrenaline during the fight or flight response?

Answer 32

During the flight or fight response, the main function of adrenaline is to trigger the liver cells to undergo glycogenolysis so that glucose is released into the bloodstream. This allows respiration to increases so more energy is available for muscle contraction.

Question 33

What is the action of adrenaline?

Answer 33

Action of adrenaline:
1. adrenaline is a hydrophilic hormone so cannot pass through cell membranes
2. instead it binds with complementary receptors on cell membranes and triggers a chain reaction inside the cell
3. when adrenaline fuses with the receptor site it activates adenylyl cyclase (an enzyme) inside the membrane
4. adenylyl cyclase converts ATP to cAMP on the inner surface of the cell membrane in the cytoplasm
5. cAMP acts as a secondary messenger. an increase in cAMP levels activates specific enzymes called protein kinases which phosphorylate and activate other enzymes which trigger the conversion of glycogen to glucose

Question 34

What are the two regions of the adrenal glands?

Answer 34

Regions of adrenal glands:
. adrenal cortex - outer region of the glands, produces hormones that are vital to life such as cortisol and aldosterone
. adrenal medulla - inner region of the glands, produces non-essential hormones like adrenaline that help the body react to stress

Question 35

What hormones are produced by the adrenal cortex?

Answer 35

The production of hormones in the adrenal cortex is itself controlled by hormones released from the pituitary gland. Three main types of hormones the adrenal cortex produces:
. glucocorticoids - includes cortisol which helps regulate metabolism by controlling how the body converts fats, proteins and carbohydrates into energy. it also helps regulate blood pressure and cardiovascular function in response to stress. another is corticosterone which works with cortisol to regulate the immune response and suppress inflammatory reactions. the release of these hormones is controlled by the hypothalamus
. mineralocorticoids - main one is aldosterone which helps control blood pressure by maintaining the balance between salt and water concentrations in the blood and body fluids. its release is mediated by signals triggered by the kidney
. androgens - small amounts of male and female sex hormones are released, their impact is relatively small compared with the larger amounts of hormones, such as oestrogen and testosterone, released by the ovaries and testes after puberty, but they are still important, especially in women after the menopause

Question 36

What hormones are secreted by the adrenal medulla?

Answer 36

The hormones in the adrenal medulla are released when the sympathetic nervous system is stimulated. The hormones secreted by the adrenal medulla are:
. adrenaline - this increases the heart rate sending blood to the muscles and brain. it also rapidly raises blood glucose concentration levels by converting glycogen to glucose in the liver
. noradrenaline - this hormone works with adrenaline in response to stress, producing effects such as increased heart rate, widening of the pupils, widening of air passages in the lungs, and the narrowing of blood vessels in non-essential organs (resulting in higher blood pressure).