Endocrinology

Question 1

What is an endocrine gland?

Answer 1

Secrete substances (hormones) into the blood stream which act on target cells which may be distant from the gland
No ducts, very rich blood supply

Question 2

Hormones

Answer 2

Thyroxine - amine
Insulin - amine
Testosterone - steroid
Adrenaline - peptide
Oxytocin - peptide
Oestrogen - steroid

Question 3

What is the role of the parathyroid hormone

Answer 3

To increase plasma calcium

Question 4

What is the role of calcitonin?

Answer 4

Decrease a raised plasma calcium

Question 5

What is the role of aldosterone?

Answer 5

Increase plasma sodium

Question 6

What is the role of ADH?

Answer 6

Increase water reabsorption at the kidneys

Question 7

What is the role of ANP?

Answer 7

Increase sodium loss at the kidneys

Question 8

Hypothalamus

Answer 8

Forms walls and floor of third ventricle
Regulating function
Closely related to pituitary
Produces releasing hormones

Question 9

Posterior pituitary

Answer 9

Releases ADH and oxytocin

Hormones travel down to axons into secretory vesicles

Question 10

Anterior pituitary

Answer 10

Enclosed by capsule of collagenous connective tissue
Surrounded by thin walled blood vessels
Secretes 6 hormones… TSH (thyroid) ACTH (adrenal cortex) FSH & LH (testes/ovaries), GH (growth hormone, entire body), PRL (prolactin, mammary glands)

Question 11

Hormonal cascades

Answer 11

Hypothalamus
                    releasing hormone
Anterior pituitary
             hormone 1 stimulating
Endocrine organ
                   hormone 2
Target tissue

Question 12

Thyroid gland

Answer 12

Cold detected by internal and external receptors
Hypothalamus
                         TRH
Anterior pituitary
                         TSH
Thyroid gland
                         T3/T4
Liver/muscle = basal metabolic rate increases, increasing core temperature

Question 13

What is TRH?

What is TSH?

Answer 13

Thyrotropin-releasing hormone, stimulates release of TSH
Thyroid-stimulating hormone, stimulates breakdown of thyroglobulin into T4 and T3

T4 converted to T3 at target tissue, an example of an amine

Question 14

Thyroid hormone function

Answer 14

Crosses cell membrane easily
Receptors:
- nucleus
- mitochondria
- cytoplasm
alter gene expression and increase ATP production
> increases metabolic rate- increase HR and respiratory rate to accommodate increase in metabolic demand
> increases temperature

Question 15

Defects of thyroid hormone function

Answer 15

Hypothyroidism = legarthy, developmental delay, goitre
Hyperthyroidism = BP/HR increases, goitre

Question 16

Role of calcitonin

Answer 16

Produced by C cells in thyroid gland
Responsible for lowering calcium phosphate levels in blood
+by reducing amounts released from bones and increasing amount excreted by the kidney+

Question 17

What are the 3 endocrine receptors?

Answer 17

Peptide hormones - membrane receptors
Steroid hormones - cytoplasmic/nuclear receptors
Amine hormones - similar to steroid, activate transcription of specific genes

Question 18

Hormones using secondary messenger system

Answer 18

cAMP opens ion channels and activates enzymes
Hormones:
- adrenaline/noradrenaline
- ADH, ACTH, FSH, LH, TSH
- PTH
- calcitonin
- glucagon

Question 19

Steroid hormone action

Answer 19

Diffuse into cell
Direct effects on specific genes
- proteins produced
Examples:
- mineralocorticoids.. aldosterone (adrenal cortex, Na+ balance, increases osmolality of blood by causing Na+ reabsorption from DCT of kidney nephron)
- glucocorticoids.. cortisone
- sex steroids.. oestrogen, testosterone

Question 20

Mechanism for amine hormones

Answer 20

Example.. thyroid hormone

1. bind to mitochondrial receptor to enter the membrane
2. binds to nuclear receptor
3. causes transcription of mRNA and translation
4. this alters cell activity and targets cell response

Question 21

Other hormone secreting tissues

Answer 21

Heart = ANP
Kidneys = calcidiol
Brain = BNP
Small intestine = CCK, secretin
Pineal gland = melatonin
Parathyroid = PTH
Placenta = hCG, progesterone
Thymus = thymosin

Question 22

Define paracrine

Answer 22

Effects of hormone are restricted to local environment

Question 23

Define autocrine

Answer 23

Self stimulation through cellular production of a hormone

Question 24

Nervous system

Answer 24

Electrical impulses propagate as action potentials

High speed transmission