Endocrine

Question 1

what’s included in the classical endocrine system?

Answer 1

Hypothalamus
Pituitary gland
Thyroid gland
Parathyroid gland
Adrenal glands
Pancreas
Testis
Ovaries

Question 2

Primary functions of the endocrine system?

Answer 2

Growth + development: hormone release plays primary and permissive role in development
Reproduction: regulate growth of sexual organs, pattern of sexual behaviour
Maintenance of Homeostasis: control ECF, electrolyte composition and bone, muscle, fat stores
Energy balance regulation: store energy and mobilise it when necessary, balancing food consumption and energy expenditure

Question 3

Where do endo and exocrine glands secrete their products?

Answer 3

Endocrine glands secrete into interstitial fluid and then blood (pituitary; thyroid)
Exocrine glands secrete into ducts (salivary; sweat)

Question 4

Define autocrine and paracrine hormones

Answer 4

bioactive messenger molecules
Autocrine: act on cells that released them (endothelial cells will secrete hormone that triggers development of endothelium)
Paracrine: act on cells adjacent to the cell that released it (neurotransmitters released at synapse, impact neighbouring cell)

Question 5

Outline the processes of peptide hormone production

Answer 5

Synthesised in ribosomes
enzymatically cleaved in the ER
Packaged in secretory vesicles in the golgi apparatus
exocytosis (membrane-bound vesicles transported to cell membrane

Question 6

In hormone context, describe a negative feedback loop

Answer 6

Gland A secretes hormone A
hormone A stimulates production of hormone B from gland B
hormone B triggers desired effect and inhibits production of hormone A

Question 7

Outline the journeys of water soluble and lipid soluble hormones from production to target cell

Answer 7

Water soluble
Hormone produced, exocytosis occurs due to vesicles transporting hormone past the plasma membrane
transported freely in blood, picked up by receptors on surface of target cell

Lipid soluble
Diffuse freely across plasma membrane, require transport protein molecule to move through blood
diffuse across target cell membrane, modified by enzymes in target cells, nuclear receptors act as transcription factors

Question 8

What do hormones bind to specifically?

Answer 8

Receptor site of glycoproteins

receptor specificity

Question 9

2 types of cell receptors?

Answer 9

Cell surface + intracellular

Question 10

Outline cell surface receptor pathway

Answer 10

Hormone binds to plasma membrane receptor
G protein pathway activated
Adenylate cyclase
ATP > cAMP
Activates protein kinases
They phosphorylate cellular proteins
lots of phosphorylated proteins cause physiological change

Question 11

Outline intracellular receptor pathway

Answer 11

Hormone diffuses into plasma membrane
binds to receptors in cytoplasm or nucleus
hormone-receptor complex alters gene expression
Altered DNA formed
altered mRNA formed
messenger RNA directs synthesis of new specific proteins that bring about physiological changes

Question 12

What are islets of langerhans, what are the 4 types?

Answer 12

Pancreatic cells that secrete glucagon and insulin

Alpha - Beta - Delta - F

Question 13

What do alpha cells (pancreas) secrete and what does it do?

Answer 13

Secrete glucagon - raises blood glucose level by accelerating breakdown of glycogen into glucose in the liver (glycogenolysis)
converts other nutrients into glucose (gluconeogenesis)

Question 14

What do beta cells (pancreas) secrete and what does it do?

Answer 14

Secrete insulin - decreases blood glucose level by accelerating movement of glucose into cells, converting to glucose to glycogen (glycogenesis)
inhibits gluconeogenesis and glycogenolysis

Question 15

What is the GSIS mechanism?

Describe it

Answer 15

Glucose Stimulated Insulin Secretion

Glucose is transported into the cell by GLUT-2, a transporter protein

It is phosphorylated by glucokinase to become glucose-6-phosphate

Undergoes glycolysis, krebs, ETC in the mitochondria, ATP is produced

the change in ATP : ADP ratio triggers the closing of the ATP sensitive K+ channel proteins

This causes the cell membrane to depolarise if -55mV threshold is met (-70mV at rest)

Voltage dependent Ca2+ channels (CDCC) open, influx of Ca2+ into the cell

Ca2+ binds to vesicles (made by golgi) containing insulin, vesicles near membrane surface release insulin out of the cell

Blood insulin increases and therefore blood glucose decreases

Question 16

2 characteristics of type 2 diabetes?

Answer 16

Characterised by:
Dysfunction of pancreatic b cells to produce and secrete insulin
Insulin resistance, inability of cells to respond to insulin

Question 17

A common anti-diabetic drug affects the cell in what way that overrides a symptom of diabetes?

Answer 17

In a diabetic person, less insulin is being made, therefore less glucose is getting transported into the cells
Without glucose, the GSIS mechanism cannot occur

The antidiabetic drugs inhibit (close) the ATP gated K+ channels that would usually close due to the change in ATP:ADP ratio in the cell

Leading to the depolarisation of the membrane, the VDCC to open, Ca2+ influx and exocytosis of the insulin contained within the vesicles

Question 18

What is the difference between GLUT2 and GLUT4

Answer 18

GLUT2 is found in the liver, pancreas etc
GLUT4 is found in the muscle, adipose, heart
GLUT 4 is not naturally found in the membrane, it is present on vesicles in the intracellular space

Question 19

Someone is suffering with hypoglycaemia, what could counteract this and why?

Answer 19

Glucagon, as it increases blood glucose by stimulating gluconeogenesis and glucogenolysis (breakdown of glycogen to glucose)

Question 20

Describe Type 1 Diabetes Mellitus

Answer 20

A lack of insulin secreting b pancreatic cells
Without insulin, Glucose cannot enter the cells, leads to high blood glucose levels
Also high volume of urine with high solute concentration