endocrine system

Question 1

how does cell communication occur

Answer 1

neuronal, autocrine, endocrine and paracrine

Question 2

what are the actions of the endocrine system

Answer 2

• control metabolic rate
• regulation of blood ions and nutrients (Na, K, glucos-insulin/glucagon)
• growth and development
• emergencies (adrenaline, cortisol)

Question 3

what are the major endocrine glands

Answer 3

pituitary glands, thyroid glands, adrenal glands

Question 4

what does the pituitary glands do

Answer 4

• growth hormone stimulates growth

- tropic hormones control other endocrine glands

Question 5

what does the thyroid gland do

Answer 5

hormones regulate metabolic rate & calcium

Question 6

what does the adrenal gland do

Answer 6

stress hormones (cortisol regulates plasma glucose adrenaline heart rate)

Question 7

what other organs have endocrine tissue

Answer 7

the gastrointestinal tract, kidneys, heart, adipose tissue (leptin) to suppress appetite

Question 8

what are the three major classes of hormones

Answer 8

peptide hormones, steroid hormones, amino acid derivatives

Question 9

what are peptide hormones

Answer 9

insulin, glucagon

Question 10

what are steroid hormones

Answer 10

testosterone, oestradiol

Question 11

what are amino acid derivatives

Answer 11

thyroid hormone, adrenaline

Question 12

what are the 4 main hormone receptors

Answer 12

1. g-protein-linked (beta-adrenoceptors)
2. ion channel (nicotinic receptors Ach)
3. steroid hormone (testosterone receptor)
4. tyrosine kinase (insulin receptor)

Question 13

what are hormones acting via g-protein linked receptors

Answer 13

largest class of receptors for many neurotransmitters/hormones.
all have similar serpentine structure (7 transmembrane spanning regions, but with very different amino acid sequences.
target for many drugs (eg. beta-blockers).
located in cell membrane
coupled to enzymes or ion channels via guanine nucleotide binding proteins (G-proteins).

Question 14

what are the different G-proteins

Answer 14

Gs – activate adenylate cyclase (eg. β-adrenoceptors)

Gi – inhibit adenylate cyclase (some muscarinic receptors)

Gq – activates to phospholipase C (some muscarinic receptors)

Question 15

what are adrenoceptors

Answer 15

These receptors (α & β) mediate the effects of adrenaline and noradrenaline

alpha-1, beta-1, beta-2, etc

Subtypes mediate different responses
e.g. β1 in heart; β-2 in lung bronchioles

Many drugs act at these receptors

Question 16

what are nuclear receptors for steroids and thyroid

Answer 16

Receptors located in the cytosol (steroids) or nucleus (thyroid hormones) rather than on the cell membrane

ligand must first cross the cell membrane, then translocate to the nucleus

ligand binding leads to alteration in gene transcription and protein synthesis within cell

Question 17

what are steroid hormone receptors

Answer 17

Group of hormones all synthesized from the lipid cholesterol

Includes male and female sex hormones

Small differences in structure result in very different effects

e.g. cortisol, estradiol, testosterone

Question 18

what are tyrosine kinase receptors

Answer 18

Hormones that act through these receptors are peptide or protein hormones

Examples:
Insulin
Growth factors
Nerve growth factor (NGF)

Question 19

what are ion channel receptors

Answer 19

Responses very fast and usually these are receptors for neurotransmitters rather than hormones.

The receptor structure itself is an ion channels
Number of transmembrane protein subunits
Form a cluster around a central pore

Question 20

what is the regulation of hormone release

Answer 20

negative feedback by hormone or negative feedback by the substance being controlled

control of release by tropic hormones or control of release by the nervous system

Question 21

what is the regulation of hormone concentration in the blood

Answer 21

Hormones bound to plasma proteins

- steroids 	
- thyroid hormone

Free in plasma
most other hormones
the unbound hormone exerts its actions on cells

Excretion
Water-soluble can be excreted by the kidney
Others are broken down in the liver

Question 22

what is the regulation of target cell sensitivity

Answer 22

Activation of the target cell depends on:

• Density of receptors
• Coupling of receptors to second messenger pathways

Question 23

what are the types of coupling receptors to second messenger pathways

Answer 23

up-regulation: - gain receptors in response to hormone

down-regulation: - lose receptors in response to the hormone

Question 24

what is permissiveness

Answer 24

can only act with another hormone present

Question 25

synergism

Answer 25

hormones act together

Question 26

antagonism

Answer 26

opposing action of another hormone