The endocrine system

Question 1

What does the endocrine system regulate?

Answer 1

-development
-growth
-reproduction
-parturition (giving birth)
-lactation
-metabolism
-blood pressure
-conc. of ions in blood
-behaviour

Question 2

What are hormones?

Answer 2

Signalling molecules/mediators secreted from endocrine cells into the blood

Question 3

Where are endocrine cells found?

Answer 3

-in endocrine tissues or glands
-close proximity to capillary beds

Question 4

What do endocrine cells enable?

Answer 4

Enable cell signalling across long distances to distant target tissues

Question 5

Is endocrine signalling slow or fast, and specific or non-specific?

Answer 5

-slow due to long distance
-specific to receptors but not specific to particular tissues/organs

Question 6

What can hormones be?

Answer 6

-protein e.g insulin
-amino acid derived e.g adrenaline
-steroid e.g estradiol

Question 7

What does hormone type influence?

Answer 7

Its cell membrane permeability

Question 8

For peptide hormones, what are they synthesised from, how are they released, what are their receptors and what is their response time?

Answer 8

synthesis-from amino acids
release-secretory granules + exocytosis
receptors-cell membrane surface receptors
response time-seconds to minutes

Question 9

For amino acid derived hormones, what are they synthesised from, how are they released, what are their receptors and what is their response time?

Answer 9

synthesis-derivatives of tyrosine. Requires specific enzymes
release-vesicles via exocytosis (except thyroid hormone)
receptors-cell membrane surface receptors (except thyroid hormone)
response time-seconds to minutes (except thyroid hormone)

Question 10

For steroid hormones, what are they synthesised from, how are they released, what are their receptors and what is their response time?

Answer 10

synthesis-metabolites of cholesterol. Requires specific enzymes
release-lipid soluble
receptors-diffuse into cells + bind to intracellular/nuclear receptors
response time-hours to days

Question 11

What are the classic 7 endocrine glands?

Answer 11

1. pituitary - anterior + posterior
2. thyroid
3. parathyroids (4 of them)
4. adrenals - cortex + medulla (on top of kidneys)
5. ovaries
6. testes
7. endocrine pancreas

Question 12

What are some endocrine tissues?

Answer 12

-hypothalamus
-kidneys
-gastrointestinal tract
-heart
-liver
-adipose tissue
-endocrine factors + neuropeptides (can be called hormones but don’t properly fit)

Question 13

Where is the adenohypophysis?

Answer 13

-Anterior lobe of the pituitary (towards the front)
-develops from an upward projection of the pharynx

Question 14

What does the adenohypophysis do?

Answer 14

-troph cells are stimulated by hormones and are carried in the hypophyseal portal system from hypothalamic neurons
-different hormones stimulate different troph cells

Question 15

What is a nuclei in a nervous system?

Answer 15

Group of cell bodies that perform the same function

Question 16

What is a hypophyseal portal system?

Answer 16

Blood travels through different areas to different organs before returning to the heart

Question 17

Where is the neurohypophysis?

Answer 17

-posterior lobe of pituitary (towards back)
-develops from a downward projection of the brain (neural tissue)

Question 18

What does the neurohypophysis do?

Answer 18

Releases hormones from the large diameter neurons directly into systemic circulation

Question 19

What are the major pituitary hormones?

Answer 19

-oxytocin: important for parturition + lactation
-ADH: important for fluid balance
-growth hormone (GH), adrenocorticotropic hormone (ACTH), thyroid-stimulating hormone (TSH), gonadotropic hormones (FSH + LH): tropic hormones

Question 20

What hormones does the thyroid gland secrete?

Answer 20

T3 and T4 amino acid derived hormones

Question 21

What is the synthesis and release of hormones from the thyroid gland dependent upon?

Answer 21

-hypothalamic-pituitary hormones
-iodine: essential trace element

Question 22

How are hormones secreted from the thyroid gland transported?

Answer 22

Across cell membranes using facilitated diffusion

Question 23

What do hormones released from the thyroid gland bind to and regulate?

Answer 23

Bind to nuclear receptors to regulate transcription. Also regulates metabolism and development + growth

Question 24

What does the parathyroid gland release, what does it regulate and what does it target?

Answer 24

Releases parathyroid hormone (PTH) - peptide
Regulates: plasma calcium + plasma phosphate
Targets: bones, intestine, kidneys

Question 25

How does PTH regulate plasma calcium by negative feedback?

Answer 25

1. increased plasma Ca2+ by Chief cells
2. decreased PTH released
3. decreased kidney tubule reabsorption
4. decreased bone Ca2+ resorption (taking Ca2+ out of bones)
5. decreased intestinal Ca2+ absorption
6. results in lowering plasma Ca2+

Question 26

What is the structure of the adrenal gland?

Answer 26

-adrenal cortex (outer layers)
-adrenal medulla (middle part)

Question 27

What does the adrenal cortex do?

Answer 27

-releases steroid hormones
-split into 3 layers (2 main ones):
-zona glomerulosa released mineralocorticoid
-zona fasciculata releases glucocorticoid which influences glucose levels

Question 28

What does the adrenal medulla do?

Answer 28

-chromaffin cells (which have neuronal properties) release adrenaline via exocytosis
-releases catecholamines –> adrenaline, noradrenaline

Question 29

What are the cells in the endocrine pancreas?

Answer 29

Islets of Langerhans:
- beta cells release insulin
-alpha cells release glucagon
both are released into portal blood to influence the liver

Question 30

How does the pancreas decrease blood glucose?

Answer 30

Negative feedback loop:
1. increased blood glucose detected by beta cells of Islets of Langerhans
2. secrete insulin
3. if secreted to liver, decrease in glucose synthesis
4. if secreted to muscle, increase in glucose storage
5. decrease blood glucose

Question 31

What hormones are produced in the ovaries?

Answer 31

Cells within the developing follicles of the ovary produce the steroid hormones oestrogen + progesterone
-can switch from using negative feedback loops to positive feedback loops

Question 32

What hormones are produced in the testes?

Answer 32

-Leydig cells in testes produce the steroid hormone testosterone
-testosterone is found in males + females –> one step process from testosterone to oestrogen
-stimulates protein synthesis
-can lead to development and growth