The endocrine system (1)

Question 1

What is the endocrine system’s role and what does it do?

Answer 1

1. Acts with the nervous system to coordinate and integrate body activities
2. Influences metabolic activities via hormones transported in the blood

Question 2

What is the meaning of endocrinology?

Answer 2

The study of hormones and endocrine organs

Question 3

What does the endocrine system control and integrate? (5)

Answer 3

1. Reproduction
2. Growth and development
   3.Maintenance of electrolyte, water, and nutrient balance of blood
3. regulation of cellular metabolism and energy balance
4. Mobilisation of body defences

Question 4

What is hormone (and what does it do)

Answer 4

A chemical messenger secreted by ductless glands directly into the blood stream to have an effect elsewhere in the body at its target issue

Question 5

What are neurotransmitters and what do they do? (+ example)

Answer 5

Released by axon terminals into synaptic junctions and act locally to control nerve cell functions
~ Acetylcholine, epinephrine

Question 6

What do endocrine hormones do? (+ example)

Answer 6

Release into the blood and affect target cells at another location in the body
~ Thyroid hormones, growth hormone, estrogen, insulin.

Question 7

What do neuroendocrine hormones do?

Answer 7

Secreted by neurons into the blood and affect target cells at another location.

Question 8

What do paracrines do? (+ examples)

Answer 8

Secreted by cells into the ECF and affect neighbouring target cells.
~ Somatostatin, histamine, eicosanoids

Question 9

What do autocrines do? (+ examples)

Answer 9

Secreted by cells into the ECF and affect the function of the same cells that produced them
~ Eicosanoids (prostaglandins, thromboxanes)

Question 10

What are cytokines what do they do?

Answer 10

Peptides that are secreted into the ECF and can function as paracrines, autocrines or endocrine hormones.

Question 11

What are exocrine glands and what do they do?

Answer 11

-Ducts carry secretion to a surface or organ cavity
-Extracellular effects (food digestion)
-GIT

Question 12

What are endocrine glands and what do they do?

Answer 12

-No ducts
-Intracellular effects, alter target cell metabolism

Question 13

Examples of glands

Answer 13

1. Pineal gland (side of head)
   2.Thyroid gland (throat)
   3.Ovary/ testis

Question 14

What are the two main classes of hormones and what do they include?

Answer 14

1. Amino acid-based hormones (amino acid derivatives, peptides and proteins)
2. Steroids (synthesized from cholesterol, gonadal and adrenocortical hormones)

Question 15

What are target cells?

Answer 15

Tissues with receptors for a specific hormone

Question 16

Examples of water-soluble hormones and what do they act on?

Answer 16

-All amino acid-based hormone except thyroid hormones
1. Act on plasma membrane receptors
2.Act via G protein second messengers

Question 17

Major difference between water and lipid soluble hormones

Answer 17

Water soluble CANNOT enter cell, lipid soluble CAN

Question 18

Examples of liquid-soluble hormones and what do they act on?

Answer 18

• Steroid and thyroid horones
  -Act on intracellular receptors that directly activate genes

Question 19

Which hormones exert effects through second-messenger systems?

Answer 19

Amino acid-based hormones (except thyroid hormone)

Question 20

What are the two main second-messenger systems?

Answer 20

1. Cyclic AMP
2. PIP2- calcium

Question 21

Go through the steps of the cyclic AMP second messenger system (6)

Answer 21

1.Hormone binds to the receptor within the cell membrane (1st messenger)
2. Receptor activates G protein (Gs)
3. G protein activates adenylate cyclase
4. Adenylate cyclase converts ATP to cAMP (2nd messenger)
5. cAMP activates protein kinases
6. The active protein kinases triggers responses of target cells (activates enzymes, stimulates cellular secretion, opens ion channel etc.)

Question 22

Which effector enzyme does hormone-activated G protein activate?

Answer 22

Phospholipase C

Question 23

Which two messengers does activated phospholipase C split membrane phospholipid PIP2 into?

Answer 23

1. Diacylglycerol (DAG)
2. Inositol trisphosphate (IP3)

Question 24

What do Diacylglycerol and Inositol trisphosphate do?

Answer 24

1. Activates protein kinases
2. Causes Ca2+ release from intracellular storage sites

Question 25

How do calcium ions act as another second messenger?

Answer 25

Ca2+ alters enzyme activity and channels, or binds to regulatory protein calmodulin

Question 26

What does calcium-bound calmodulin do?

Answer 26

Activates enzymes that amplify cellular response

Question 27

Steps undertaken by intracellular receptors and direct gene activation (hormones) (5)

Answer 27

1. The steroid hormone (lipid-soluble hormones and thyroid diffusing into target cells) diffuses through the plasma membrane and binds an intracellular receptor 2. The receptor-hormone complex enters the nucleus 3. The receptor-hormone complex binds to a specific DNA region 4. Binding initiates transcription of the gene to mRNA 5. The mRNA directs protein synthesis.

Question 28

What does negative feedback prevent?

Answer 28

Overactivity of hormone systems

Question 29

What can surges of hormones occur with? (+ example)

Answer 29

Positive feedback , e.g. oxytocin

Question 30

What are the three stimuli that endocrine hormones are stimulated to synthesize and release hormones in response to?

Answer 30

1. Humoral stimuli 2. Neural stimuli 3. Hormonal stimuli

Question 31

What are humoral stimuli (+ example)

Answer 31

-Changing blood levels of ions and nutrients directly stimulate secretion of hormones e.g. Ca2+ in blood: Declining blood Ca2+ concentration stimulates parathyroid glands to secrete PTH (parathyroid hormone), PTH causes Ca2+ conc to rise = stimulu s removed

Question 32

What happens during a neural stimuli and example of one.

Answer 32

- Nerve fibers stimulate hormone release -Sympathetic nervous system fibers stimulate adrenal medulla to secrete catecholamines

Question 33

Hormonal stimulus and example.

Answer 33

-Hormones stimulate other endocrine organs to release their hormones - e.g. Hypothalamic hormones stimulate release of most anterior pituitary hormones then anterior pituitary hormones stimulate targets to secrete more hormones.

Question 34

What three factors does target cell activation depend on?

Answer 34

1. Blood levels of hormone 2. Relative number of receptors on/in target cell 3. Affinity (strength) of binding between receptor and hormone

Question 35

What is up-regulation (target cell specificity)

Answer 35

Target cells form more receptors in response to low hormone levels

Question 36

What is down-regulation and its importance to target cells.

Answer 36

When target cells lose receptors in response to high hormone levels -Desensitize the target cells to prevent them from overreacting to persistently high levels of hormone.

Question 37

All hormones circulate in the blood freely without carriers except?

Answer 37

Steroid an thyroid hormones which are attached to plasma proteins.

Question 38

What does the concentration of circulating hormones reflect? (2)

Answer 38

1. Rate of release 2. Speed at which it is inactivated and removed from body

Question 39

How can hormones be removed from the body? (3)

Answer 39

1. Degrading enzymes 2. Kidneys 3. Liver

Question 40

Definition of Half-life

Answer 40

Time required for level of hormone in blood to decrease by half (can vary from half a minute to a week)