The endocrine system-hormonal communication

Question 1

3 key homeostatic regulations

Answer 1

-thermoregulation, control of body temp
-control of blood glucose
-osmoregulation, the control of water potential of bodily fluids

Question 2

define hormone

Answer 2

-a chemical messenger produced by an endocrine gland and carried by the blood
-they are chemicals which transmit info from one part of an organism to another and bring about a change
-they alter the activity of one or more target organs

Question 3

what is a gland

Answer 3

a group of cells that produces and releases one or more substances (a process known as secretion

Question 4

first and second messenger hormones

Answer 4

-The first messenger is the hormone that brings the “information or signal” from the endocrine gland
-Hormones don’t actually enter the cell, they bind to a receptor on the cell surface membrane
-A second messenger inside the cell causes the effect
-(e.g first = adrenaline, Cyclic amp =second which enters the cell)

Question 5

where are the adrenal glands located + 2 main parts they are made up off

Answer 5

-above the kidney
-central medulla and outer cortex

Question 6

role of the cortex in adrenal glands

Answer 6

-produces steroid hormones (mainly aldosterone and cortisol) that carry out a variety of functions including the control of concentrations of mineral ions, carbohydrates and proteins

Question 7

role of medulla in adrenal gland

Answer 7

-produces adrenaline, a hormone produced at times of stress or excitement that affects many body organs, preparing the body to respond to emergency situations- i.e fight or flight

Question 8

exocrine gland vs endocrine gland

Answer 8

-endocrine, secretes hormones straight into blood
-exocrine, secretes hormones via a duct

Question 9

exocrine and endocrine function of the pancreas

Answer 9

exocrine- produce pancreatic juice (digestive enzymes) which are delivered to small intestine to help w digestion. Under microscope, most of cells produce digestive enzymes
endocrine- produce glucagon and insulin. (Islets of Langerhans do in kidney)

Question 10

Islets of langerhan

Answer 10

-small sections of cells in pancreas which contain two cell types: alpha cells, which secrete glucagon, and beta cells, which secrete insulin

Question 11

3 ways glucose can enter bloodstream

Answer 11

-Absorption in the gut following carbohydrate digestion
-Hydrolysis of glycogen stores
-Non-carbohydrates such as lipids, lactate and amino acids that have been converted to glucose

Question 12

decrease in blood concentration

Answer 12

-The α cells respond by secreting glucagon
-The β cells respond by stopping the secretion of insulin
GLYCOGENEOLYSIS
1-glucagon binds to receptors on csm of liver cells
2-binding causes a change in receptor protein= activates G protein= activates adenylyl cyclase=catalyses conversion of ATP - cAMP= binds to protein kinase A enzymes= activates glycogen phosphorylase enzymes= catalyse breakdown of glycogen to glucose

This process amplifies the original signal from glucagon= release extra glucose from liver

Question 13

How can adrenaline raise blood glucose levels

Answer 13

-it binds to different receptors on surface of liver cells that activate enzyme cascade in glycogenolysis
-also stimulates the breakdown of glycogen stores in muscle during exercise

Question 14

Increase in blood glucose concentration

Answer 14

-detected by B cells in pancreas
-glucose molecules enter the β cells by facilitated diffusion
-cells respire this glucose and produce ATP
-High concentrations of ATP cause the potassium channels in the β cells to close, producing a change in the membrane potential=voltage-gated calcium channels open
-in response to calcium ions, B cells secrete insulin
-Insulin-containing vesicles move towards the cell-surface membrane where they release insulin into the capillaries
-once in bloodstream, it stimulates the uptake of glucose by muscle + fat cells and liver

Question 15

action of insulin with glucose transporter proteins

Answer 15

-muscle liver + fat cells have glucose transporter proteins in their csm
-they allow for uptake of glucose via facilitated diffusion, uptake of glucose is limited by no. of glucose transporter proteins present
-Insulin binds to specific receptors on the membranes of target cells
-This stimulates them to activate/add more glucose transporter proteins to their cell surface membrane which increases the permeability of the cells to glucose

Question 16

action of insulin in liver

Answer 16

-stimulates glycogenesis
-Once glucose has entered a liver cell an enzyme rapidly converts it to glucose phosphate
-Different enzymes then convert glucose phosphate into glycogen= helps to lower glucose concentration within the liver cell
-A steep diffusion gradient is maintained between the blood in the capillaries and the liver cells

Question 17

negative feedback during blood glucose maintenance

Answer 17

-α and β cells in the pancreas act as the receptors
-They release the hormones glucagon (secreted by α cells) and insulin (secreted by β cells)
-Liver cells act as the effectors in response to glucagon and liver, muscle and fat cells act as the effectors in response to insulin

Question 18

glycogenesis, glycogenolysis and gluconeogenesis

Answer 18

1-synthesis of glycogen from glucose molecules, initiated by insulin
2-breakdown of glycogen to produce glucose molecules initiated by glucagon
3-synthesis of glucose molecules from non-carb molecules, triggered by glucagon

Question 19

type 1 diabetes

Answer 19

-condition in which the pancreas fails to produce sufficient insulin to control blood glucose levels
-normally due to an autoimmune response where the body attacks the islets of langerhan
-

Question 20

type 2 diabetes

Answer 20

• the pancreas still produces insulin but the receptors have reduced in number or no longer respond to it
  -lack of response to insulin means there is a reduced glucose uptake which leads to an uncontrolled high blood glucose concentration

Question 21

diabetes and blood pressure

Answer 21

-high blood glucose concentration lowers the water potential of the blood which causes more water to move from the tissues into the blood vessels by osmosis
- =there is a larger volume of blood within the circulatory system which causes blood pressure to increase

Question 22

recombinant DNA

Answer 22

DNA that has been altered by introducing nucleotides from another source
-produces recombinant proteins (insulin as e.g)

Question 23

advantages of recombinant insulin

Answer 23

-identical to human insulin unless modified to have different properties (eg. act faster or to act more slowly)
-reliable supply available to meet demand
-Fewer ethical, moral or religious concerns (proteins are not extracted from cows or pigs)
Fewer rejection problems or side effects or allergic reactions
-Cheaper to produce in large volumes

Question 24

stem cells on treatment of diabetes

Answer 24

-Stem cells can be treated so that they differentiate into pancreatic β cells
-These newly developed β cells can then be transplanted into the pancreas of a diabetic individual, replacing the damaged cells and allowing them to produce insulin
-not yet work on humans