Communication, hormones and homeostasis

Question 1

What are endocrine glands

Answer 1

Groups of cells that are specialised to secrete hormones

Question 2

What are hormones

Answer 2

Chemical messengers often proteins or peptides and some are steroids

Question 3

When are hormones secreted

Answer 3

When an endocrine gland is stimulated such as by a change in concentration of a specific substance. They can also be stimulated by electrical impulses

Question 4

How do hormones travel around the body

Answer 4

They diffuse into the blood and take them around the circulatory system. They then diffuse out of the blood and around the body each hormone binding to specific receptors for that hormone found on membranes of cells called target cells.

Question 5

What is tissue that contains target cells

Answer 5

Target tissue

Question 6

What is the pathway of a response for chemical signals such as low blood glucose concentration

Answer 6

Stimulus - blood glucose concentration
Receptors on pancreas cells detect the low concentration
Hormone - The pancreas releases the hormone glucagon into the blood
Effectors - Target cells in the liver detect glucagon and convert glycogen into glucose
Response - Glucose is released into the blood, so glucose concentration increases

Question 7

What is another word for a hormone and why

Answer 7

A first messenger because it carries the chemical message the first part of the way from the endocrine gland to the receptor on the target cells

Question 8

What does a hormone binding to its receptor cause

Answer 8

Activates an enzyme in the cell membrane which catalyses the production of a molecule inside the cell called a signaling molecule which signals to other parts of the cell to change how the cell works

Question 9

Why is a signaling molecule called a second messenger

Answer 9

It carries the chemical message the second part of the way from the receptor to other parts of the cell

Question 10

What is the cascade that the hormone adrenaline results in

Answer 10

Adrenaline is the first messenger and it binds to specific receptors in the cell membranes activating an enzyme called adenylyl cyclase. This catalyses the production of a second messenger called cyclic AMP. Then a cascade of enzyme reactions occur making more glucose available to the cell by catalyzing glycogen breaking down to glucose

Question 11

What are the adrenal glands

Answer 11

Endocrine glands that are found just above the kidneys containing the cortex and medulla

Question 12

What is the function of the cortex of the adrenal glands

Answer 12

Secretes hormones such as cortisol and aldosterone when you are stressed which have a role in long and short term responses to stress.

Question 13

How does the cortex section of the adrenal gland when responding to stress

Answer 13

• Stimulating the breakdown of proteins and fats into glucose, increasing the amount of energy avaliable so the brain and muscles can respond to the situation
• Increasing blood volume and pressure by increasing the uptake of sodium ions and water by the kidneys
• Suppressing the immune system

Question 14

What is the function of the medulla of the adrenal gland

Answer 14

Secretes catecholamine hormones (adrenaline and noradrenaline) when stressed. These act to make more energy in the short term

Question 15

How does the medulla section of the adrenal gland respond to stress

Answer 15

• Increasing heart and breathing rate
• Causing cells to break down glycogen to glucose
• Constricting some blood vessels so that blood is diverted to the brain and muscles

Question 16

What are the islets of Langerhans

Answer 16

Areas of the pancreas containing endocrine tissue found in clusters around blood capillaries. They secret hormones directly into the blood

Question 17

What are the islets of Langerhans made from

Answer 17

Alpha and beta cells

Question 18

What do alpha cells secrete

Answer 18

Glucagon

Question 19

What do beta cells secrete

Answer 19

Insulin

Question 20

What are ectotherms

Answer 20

Animals that can’t control their body temperature internally and must control by changing their behavior.

Question 21

What are ectotherms internal temperature, activity and metabolic rate controlled by

Answer 21

Their internal temperature and activity depends on the external temperature. They are more active in higher temperatures. Their metabolic rate is variable and generate very little heat themselves

Question 22

What is an endotherm

Answer 22

An animal that controls their body temperature internally by homeostasis but can also do so by behaviour

Question 23

What are endotherms internal temperature, activity and metabolic rate controlled by

Answer 23

Their internal temperature is less affected by external temperature and their activity is largely independent of temperature. They constantly have a high metabolic rate and generate a lot of heat from metabolic reactions.

Question 24

What are mammals mechanisms to reduce body temperature

Answer 24

Sweating - secreted from sweat glands, taking heat from the body and evaporating it

Hairs lie flat - less air is trapped so the skin is less insulated and heat can be lost more easily

Vasodilation - arterioles dilate near the skin surface so more blood flows through the capillaries in the surface levels of the dermis. This means that more heat is lost from the skin by radiation and temperature is lowered.

Question 25

What are the mechanisms to increase body temperature

Answer 25

Shivering - muscles contract in spasms so more heat is produced from increased respiration Much less sweat - reduces heat loss Hairs stand up - erector pili muscles contract trapping more air preventing heat loss Vasoconstriction - arterioles near the surface of the skin constrict so less blood goes to the capillaries in surface of the dermis. Hormones - release of adrenaline and thyroxine increasing metabolism and therefore heat

Question 26

What are the different types of thermoreceptors and what do they do

Answer 26

Thermoreceptors in the hypothalamus detect internal temperature Thermoreceptors in the skin (peripheral temperature receptors) detect external temperature

Question 27

What controls mammals body temperature

Answer 27

The hypothalamus

Question 28

What occurs when there is a rise in body temperature

Answer 28

- Thermoreceptors detect temp is too high - Hypothalamus sends signals to effectors - Vasodilation, sweating, hairs lie flat, no shivering, no adrenaline or thyroxine - More heat's lost and less heat is produced by the body

Question 29

What occurs when there is fall in body temperature

Answer 29

- Thermoreceptors detect temp is too low - Hypothalamus sends signals to effectors - Vasoconstriction, much less sweating, hairs stand upright, shivering, adrenaline and thyroxine release - More heat is produced and conserved by the body

Question 30

What can change your blood glucose concentration

Answer 30

Eating carbs will rise and exercise will make it fall due to respiration

Question 31

What is the normal concentration of glucose in the blood

Answer 31

90mg per 100cm^3

Question 32

What is blood glucose monitored by

Answer 32

Cells in the pancreas called islets of Langerhans

Question 33

What are insulin and glucagon

Answer 33

Peptide hormones which respond to restore the blood glucose concentration to the normal level

Question 34

How does insulin lower blood glucose

Answer 34

1) Binds to specific receptors on the cell membranes of liver cells and muscle cells 2) Increases the permeability of cell membranes to glucose so cells take up more glucose 3) Insulin also activates enzymes that convert glucose into glycogen 4) Cells are able to store glycogen in their cytoplasm as an energy source 5) The process of forming glycogen from glucose is glycogenesis 6) This increases the rate of respiration of glucose in muscle cells

Question 35

How does glucagon raise blood glucose concentration when too low

Answer 35

1) It binds to specific receptors on cell membranes of liver cells 2) Activates enzymes that break down glycogen into glucose called glycogenolysis 3) Glucagon promotes the formation of glucose from glycerol and amino acids 5) The process of forming glucose from non carbs is gluconeogenesis

Question 36

What occurs in the negative feedback mechanism if a rise in blood glucose is detected

Answer 36

- Pancreas detects blood glucose concentration is too high - Beta cells secrete insulin and alpha cells stop secreting glucagon - Insulin binds to receptors on liver and muscle cells - Cells take up more glucose, glycogenesis is activated, cells respire more glucose - Less glucose in blood

Question 37

What occurs in the negative feedback mechanism if a fall in blood glucose is detected

Answer 37

- Pancreas detects blood glucose concentration is too low - Alpha cells secrete glucagon and beta cells stop secreting insulin - Glucagon binds to receptors on liver cells - Glycogenolysis is activated, gluconeogenesis is activated, cells respire less glucose - Cells release glucose into the blood

Question 38

How do beta cells secrete insulin

Answer 38

1) When blood glucose conc is high, more glucose enters the beta cells by facilitated diffusion 2) More glucose in a beta cell causes the rate of respiration to increase making more ATP 3) The rise in ATP triggers the potassium ion channels in the beta cell plasma membrane to close 4) This means potassium ions can't get through the membrane so build up inside the cell 5) This makes the inside of the beta cell less negative as there are more positively charged potassium ions inside the cell so the plasma membrane of the beta cell is depolarized 6) Depolarisation triggers calcium ion channels in the membrane to open, so calcium ions diffuse into the beta cell 7) This causes the vesicles to fuse with the beta cell plasma membrane, releasing insulin by exocytosis

Question 39

What is diabetes full name

Answer 39

Diabetes mellitus

Question 40

What is diabetes mellitus

Answer 40

A condition where blood glucose concentration can't be controlled properly. Either type 1 or 2

Question 41

What is type 1diabetes

Answer 41

No insulin is produced. Auto-immune disease where the body attacks and destroys the beta cells in the islets of Langerhans . After eating, blood glucose conc rises and stays high which can result in death if untreated. The kidneys are unable to reabsorb all the glucose so some is excreted in the urine`

Question 42

How to treat type 1 diabetes

Answer 42

With insulin therapy: - Regular insulin injections - Insulin pump Islet cell transplantation

Question 43

What do people with type 1 diabetes need to do

Answer 43

Regularly monitor blood glucose conc and think about diet and activity

Question 44

What is type 2 diabetes

Answer 44

Occurs when beta cells don't produce enough insulin or the body does not respond properly to insulin. Linked to obesity. Glucose conc is higher than normal if insulin receptors do not work.

Question 45

How to treat type 2 diabetes

Answer 45

Lifestyle changes: eating healthy, exercise and losing weight Medication: - Metformin, sulfonylureas, thiazolidinedione's Insulin therapy

Question 46

How else can insulin be produced

Answer 46

By genetically modified bacteria. It can be extracted from animal pancreases but GM bacteria is more commonly used. Stem cells could also be produced by growing them into beta cells to be implanted into the pancreas making insulin as normal for type 1 suffers

Question 47

Why is GM bacteria used to produced insulin over from animal pancreas's

Answer 47

- Cheaper - Large quantities can be produced - Less likely to trigger an allergic reaction or be rejected by immune system - More ethical/religious