The endocrine system

Question 1

What do hormones help to regulate?

Answer 1

Extracellular Fluid
Metabolism
Biological clock 
Concentration of cardiac and smooth muscle 
Glandular secretion 
Immune functions

Question 2

What are the two types of glands?

Answer 2

Exocrine- secrete products into ducts which empty into body cavities or body surfaces
Endocrine - Secrete products into interstitial fluid, diffuse into blood

Question 3

Examples of Endocrine glands?

Answer 3

Pituitary, thyroid, parathyroid, adrenal, pineal

Question 4

What is down-regulation?

Answer 4

Excess hormone leads to a decrease in number of receptors
Receptors undergo endocytosis and are degraded
This decreases the sensitivity of target cell to hormone

Question 5

What is up-regulation?

Answer 5

Deficiency of hormone leads to an increase in the number of receptors
Target tissue becomes more sensitive to the hormone

Question 6

What are the two types of hormones?

Answer 6

Circulating hormones - circulate in blood throughout the body
Local hormones - act locally

Question 7

What are the two divisions of local hormones

Answer 7

Paracrine - act on neighbouring cells

Autocrine - act on the same cell that secreted them

Question 8

What are the chemical classes of hormones?

Answer 8

Lipid-soluble - use transport proteins e.g. steroid, thyroid and NO
Water-soluble - circulate in ‘free’ form e.g. amine, peptide, eicosanoid

Question 9

What does the responsiveness of a target cell depend upon?

Answer 9

Hormone’s concentration
Abundance of target cell receptors
Influence exerted by other hormones

Question 10

How is hormone secretion regulated?

Answer 10

Signals from nervous system
chemical changes in the blood
other hormones

Question 11

How do lipid-soluble hormones act?

Answer 11

Diffuse through phospholipid bilayer and into the cell
Bind to specific receptor turning on/off specific genes
New mRNA is formed and directs synthesis of new proteins
New protein alters cell’s activity

Question 12

How do water-soluble hormones act?

Answer 12

CANNOT DIFFUSE THROUGH PLASMA MEMBRANE
Hormone binds (first messenger) to receptor on cell membrane
The activated receptor activates a membrane G-protein which turns on adenylate cyclase
Adenylate cyclase converts ATP into cyclic AMP which activates protein kinases
Protein kinases phophorylate enzymes which catalyse reactions that produce the physiological response

Question 13

Where does the hypothalamus receive input from?

Answer 13

cortex, thalamus, limbic system and internal organs

Question 14

Which gland does the hypothalamus control?

Answer 14

Pituitary gland with 9 different releasing and inhibiting hormones

Question 15

What do together the hypothalamus and pituitary gland regulate?

Answer 15

Growth, development, metabolism and homeostatis

Question 16

How are the hypothalamus and anterior pituitary connected?

Answer 16

Hormones transported via blood

Question 17

How are the hypothalamus and posterior pituitary connected?

Answer 17

Hormones transported via axons of hypothalamic neutrons and then stored in posterior pituitary

Question 18

What is the human growth hormone known as?

Answer 18

Somatotrophin

Question 19

How does somatotrophin act?

Answer 19

Indirectly on tissues by promoting the synthesis and secretion of small protein hormones called insulin-like growth factors

Question 20

How is human growth hormone regulated?

Answer 20

Low blood sugar stimulates release of hGH from anterior pituitary
This causes more glycogen broken down into glucose by liver cells

Question 21

What are the clinical uses of human growth hormone?

Answer 21

Growth hormone deficiency

Overactivity of growth hormone

Question 22

What does adrenocorticotrophic hormone (ACTH) stimulate?

Answer 22

Cells of the adrenal cortex to produce glucocsorticoids

Question 23

What are the functions of glucocorticoids?

Answer 23

Help regulate metabolism 
Increase rate of protein catabolism & lipolysis 
Conversion of amino acids to glucose 
Provide stress resistance 
Raise BP by vasoconstriction 
Anti-inflammatory effects

Question 24

What are the action of gonadotrophin releasing hormone?

Answer 24

GRH is secreted by neutrons in hypothalamus
Travels venous stream to anterior pituitary and activated receptors on the gonadotroph cells
Gonadotroph cells the secrete FSH and LH

Question 25

What are the reproductive functions of FSH?

Answer 25

Initiates the formation of follicles within the ovary
stimulates follicle cells to secrete oestrogen
stimulates sperm production in testes

Question 26

What does LH stimulate in females?

Answer 26

Secretion of oestrogen
Ovulation of 2nd oocyte from ovary
Formation of corpus luteum
Secretion of progesterone

Question 27

What are the clinical uses of FSH and LH?

Answer 27

Assisted reproducion
Ovulation induction
Male infertility

Question 28

What is the role of Prolactin?

Answer 28

Initiates and maintains mile secretion by the mammary glands

Question 29

What are the features of the posterior pituitary gland?

Answer 29

Does not synthesise hormones
Consists of axon terminals of hypothalamic neutrons
Neurons release two neurotransmitters into capillaries

Question 30

What are the 2 neurotransmitters released from the posterior pituitary gland?

Answer 30

Oxytocin

Antiduiretic hormone

Question 31

What are the target tissues of oxytocin?

Answer 31

Uterus and mammary glands which are both involved in neuroendocrine reflexes

Question 32

What role does oxytocin play after delivery of baby and placenta?

Answer 32

Stimulates contraction of the uterus and ejection of milk from the breasts
Nursing stimulates oxytocin release promoting uterine contractions and the expulsion of the placenta

Question 33

What is the role of antidiuretic hormone?

Answer 33

Stimulates water reabsorption by the kidneys and arteriolar constriction
Decreases urine volume and conserve body water
Controlled primarily by osmotic pressure of the blood

Question 34

What is the stress response?

Answer 34

3 stages
Initial fight or flight
Slower resistance reaction
Exhaustion

Question 35

What are the effects of prolonged exposure to stress?

Answer 35

Wasting of muscles
suppression of immune system
ulceration of GI tract
Failure of pancreatic beta cells