Chapter 14 Hormonal Communication

Question 1

What is the endocrine system made up of?

Answer 1

Endocrine glands
= a group of cells which are specialised to secrete hormones (directly into the bloodstream)

e.g. pancreas gland and adrenal gland

Question 2

Pituitary gland??

Answer 2

At the base of the brain makes several hormones - its close proximity to the hypothalamus ensures that the nervous and hormonal responses of the body are coordinated.

• produces GROWTH hormone
• produces ANTI-DIURETIC hormone (increases water absorption in the kidneys)
• produce GONADOTROPHINS (control the development of ovaries and testes)

Question 3

Pineal gland??

Answer 3

• produces MELATONIN (affects the reproductive development and daily cycles)

Question 4

Thyroid gland??

Answer 4

• produces THYROXINE (controls rate of metabolism, rate at which glucose is used up, and promotes growth)

Question 5

Thymus??

Answer 5

• produces THYMOSIN (promotes production and maturation of white blood cells)

Question 6

Adrenal gland??

Answer 6

• produces ADRENALINE (increases heart and breathing rate and raises blood sugar level)

Question 7

Pancreas??

Answer 7

• produces INSULIN (converts excess glucose into glycogen in the liver and glucagon which converts glycogen back into glucose)

Question 8

Testis??

Answer 8

• produces TESTOSTERONE (controls sperm production and secondary sexual characteristics)

Question 9

Ovary??

Answer 9

• produces OESTROGEN (controls ovulation and secondary sexual characteristics)
• produces PROGESTERONE (prepares the uterus lining for receiving an embryo)

Question 10

What is the diff between ENDOcrine glands and EXOcrine glands?

Answer 10

EXOcrine glands secrete chemicals through ducts into organs, or to the surface of the body.

Question 11

Types of hormones?

Answer 11

(1) steroids

(2) proteins

(3) glycoproteins

(4) polypeptides

(5) amines

(6) tyrosine derivatives

Question 12

When are hormones secreted generally?

Answer 12

When a gland is stimulated - which can occur as a result of…
- a change in conc.
- another hormone
- nerve impulse

Question 13

Target cells??

Answer 13

Once secreted the hormones are transported in the blood plasma all over the body.

Hormones diffuse out of the blood and bind to specific receptors of that hormone
- found on the membranes or in the cytoplasm of cells in the target organs = target cells

Once bound to their receptors the hormones stimulate the target cells to produce a response.

Question 14

What are steroid hormones?

Answer 14

They are LIPID SOLUBLE.
- they pass through the lipid component of the cell membrane
- they bind to steroid hormone receptors = hormone-receptor complex
(receptors either in cytoplasm or nucleus)

e.g. Oestrogen

Question 15

What does the hormone-receptor complex do?

Answer 15

Attaches to DNA…

Acts as a transcription factor which either inhibits/facilitates the transcription of a specific gene.

Question 16

What are non-steroid hormones?

Answer 16

They are hydrophilic so cannot pass directly through the cell membrane.
- they bind to the specific receptors at the surface membrane of the target cell

• this triggers a cascade reaction mediated by chemicals called SECOND MESSENGERS

e.g. Adrenaline

Question 17

Hormonal v.s. Neuronal communication?

Answer 17

Hormones are to released directly onto their target cells = slower and less specific form of communication.

Hormones are not broken down as quickly as neurotransmitters, therefore have a longer lasting and widespread response.

Question 18

What are the adrenal glands?

Answer 18

3cm- 5cm

• located at the top of each kidney and made up of 2 distinct parts surrounded by a capsule

(1) ADRENAL CORTEX
- outer region of the glands
- produces the ESSENTIAL hormones (e.g. cortisol and aldosterone)

(2) ADRENAL MEDULLA
- inner region of the glands
- produces the NON-essential (e.g. adrenaline)

Question 19

What are the 3 main types of hormones produced by the adrenal cortex?

Answer 19

The production of hormones by the adrenal cortex is controlled by hormones released from the pituitary gland.

(1) GLUCOCORTICOIDS (release controlled by hypothalamus)
- CORTISOL (regulates metabolism - by controlling how the body converts fats, proteins, and carbs into energy) AND (regulates blood pressure and cardiovascular function in response to stress)

• CORTICOSTERONE (works with cortisol to regulate immune response and suppress inflammatory reactions)

(2) MINERALCORTICOIDS (release triggered by kidneys)
- ALDOSTERONE (which helps controls blood pressure by maintaining the balance between salt and water conc. in blood and body fluids).

(3) ANDROGENS
- small amounts of male/female sex hormones
(relatively small impact compared to those of larger amounts - oestrogen and testosterone)
- still important especially in women after menopause.

Question 20

What are the hormones secreted by the adrenal medulla?

Answer 20

The hormones of the adrenal medulla are released when the sympathetic nervous system is stimulated (when the body is stressed).

(1) ADRENALINE
- increases the heart rate sending blood quickly to the muscles and brain
- rapidly raises blood glucose conc. levels by converting glycogen into glucose in the liver

(2) NORADRENALINE
- works with adrenaline in response to stress
- increases heart rate
- widens pupils
- widens air passages in the lungs
- narrowing of blood vessels in non-essential organs (higher blood pressure)

Question 21

What are the 2 main functions of the pancreas in the body?

Answer 21

(1) exocrine gland
- to produce enzymes and release them via a duct into the DUODENUM

(2) endocrine gland
- to produce hormones and release them into the blood

Question 22

Pancreas’ role as an EXOcrine gland? AND what three digestive hormones does it produce?

Answer 22

• most of the pancreas is made up of exocrine glandular tissue
  (this tissue is responsible for producing digestive enzymes and an alkaline fluid - pancreatic juice)
• the enzymes and pancreatic juice are secreted into ducts which eventually lead to the pancreatic duct
• they are released into the duodenum (top part of the small intestine)

(1) AMYLASE - breaks down starch into simple sugars

(2) PROTEASE - breaks down proteins into amino acids

(3) LIPASES - breaks down lipids into fatty acids and glycerol

Question 23

Pancreas’ role as an ENDOcrine gland?

Answer 23

• the pancreas is responsible for producing insulin and glucagon (roles in blood glucose conc.)

Within the exocrine tissue, there are regions of ENDOcrine tissue = ISLETS OF LANGERHANS
- responsible for producing insulin and glucagon and secreting these directly into the blood

Question 24

Histology of the pancreas? (diff between pancreatic acini and islets)

Answer 24

Appearance
- islets = LIGHTLY stained
- acini = DARKER staines

Shape
- islets = large, spherical clusters
- acini = small, berry-like clusters

Type of tissue
- islets = endocrine pancreas
- acini = exocrine pancreas

Function
- islets = produce and secrete hormones
- acini = produce and secrete digestive enzymes

Question 25

Different types of cells in the Islets of Langerhans?

Answer 25

(1) a = alpha cells = produce and secrete GLUCAGON (2) ß = beta cells = produce and secrete INSULIN - alpha cells are larger and more numerous than beta cells within an islet.

Question 26

What type of staining do you use on the pancreas?

Answer 26

Differential staining ß cells = blue a cells = pink

Question 27

What is glucose?

Answer 27

Glucose is a small, soluble molecule that is carried in the blood plasma. - it is normally maintained at a concentration of approx. 90mg/cm^3 of blood

Question 28

When can blood glucose conc. INCREASE?

Answer 28

(1) Diet - when you eat carb-rich foods (high in starch or sucrose) - carbs are broken down into glucose - glucose released is absorbed into the bloodstream, and blood glucose conc. rises (2) GLYCOGENOLYSIS - glycogen stored in the liver and muscle cells is broken down into glucose and released into the blood (3) GLUCONEOGENESIS - the production of glucose from non-carb sources

Question 29

When can blood glucose conc. DECREASE

Answer 29

(1) Respiration - some of the glucose in the blood is used up by cells to release energy. (2) GLYCOGENESIS - the production of glycogen (store when glucose conc. is too high)

Question 30

How do the islets of Langerhans react when blood glucose conc. is too high?

Answer 30

Insulin is produced by the BETA cells of the islets. Beta cells detect the rise in conc. and respond by secreting insulin directly into the bloodstream.

Question 31

INSULIN??

Answer 31

Most body cells have insulin receptors on their cell surface membrane. - when insulin binds to its glycoprotein receptor, it causes a change in the tertiary structure of the glucose transport protein channels. - this causes the channels to open allowing more glucose to enter the cell - insulin also activates enzymes within some cells to convert glucose to glycogen and fat

Question 32

How does insulin lower blood glucose conc. ?

Answer 32

(1) increasing the rate of absorption of glucose by cells (2) increasing the respiratory rate of cells - increases their need for glucose (3) increasing the rate of glycogenesis - stimulates the liver (4) increasing the rate of glucose to fat conversion (5) inhibiting the release of glucagon from the alpha cells of the islets

Question 33

Negative feedback??

Answer 33

When blood glucose conc. falls below a set level... - the beta cells detect this and reduce their secretion of insulin When blood glucose conc. rises above a set level... - the alpha cells detect this and reduce their secretion of glucagon

Question 34

GLUCAGON??

Answer 34

Glucagon is produced by alpha cells of the islets. The only cells that have glucagon receptors are the liver and fat cells.

Question 35

How does glucagon raise blood glucose conc. ?

Answer 35

(1) glycogenolysis - liver breaks down glycogen store into glucose (2) reducing the amount of glucose absorbed by the liver cells (3) increasing gluconeogenesis - increasing the conversion of amino acids and glycerol into glucose in the liver

Question 36

Why is the system o maintaining blood glucose conc. considered to be self-regulating?

Answer 36

It is the level of glucose in the blood that determines the quantity of insulin and glucagon that is released.

Question 37

Control of insulin secretion (mechanism)?

Answer 37

(1) at normal levels, POTASSIUM channels in the plasma membrane of beta cells are open and K+ ions diffuse out of the cell. - the inside of the beta cell is at a potential of -70mV (2) when conc. rises, glucose enters the cell by a glucose transporter (3) the glucose is metabolised inside the mitochondria - producing ATP (4) the ATP binds to the potassium channels and causes them to close = ATP-sensitive potassium channels (5) as K+ ions can no longer diffuse out of the cell, the potential reduces to -30mV and DEPOLARISATION occurs (6) Depolarisation causes the voltage-gated CALCIUM channels to open (7) Ca2+ (calcium ions) enter the cell and cause secretory vesicles to release the insulin they contain by EXOCYTOSIS.