Endocrinology Flashcards Preview

Anatomy and Physiology > Endocrinology > Flashcards

Flashcards in Endocrinology Deck (24):
1

What is an endocrine gland?

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

2

Hormones

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

3

What is the role of the parathyroid hormone

To increase plasma calcium

4

What is the role of calcitonin?

Decrease a raised plasma calcium

5

What is the role of aldosterone?

Increase plasma sodium

6

What is the role of ADH?

Increase water reabsorption at the kidneys

7

What is the role of ANP?

Increase sodium loss at the kidneys

8

Hypothalamus

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

9

Posterior pituitary

Releases ADH and oxytocin
Hormones travel down to axons into secretory vesicles

10

Anterior pituitary

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)

11

Hormonal cascades

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

12

Thyroid gland

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

13

What is TRH?

What is TSH?

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

14

Thyroid hormone function

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

15

Defects of thyroid hormone function

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

16

Role of calcitonin

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+

17

What are the 3 endocrine receptors?

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

18

Hormones using secondary messenger system

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

19

Steroid hormone action

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

20

Mechanism for amine hormones

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

21

Other hormone secreting tissues

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

22

Define paracrine

Effects of hormone are restricted to local environment

23

Define autocrine

Self stimulation through cellular production of a hormone

24

Nervous system

Electrical impulses propagate as action potentials
High speed transmission