Homeostatis

Question 1

Def of homeostasis

Answer 1

Physiological control systems maintain the internal environment within restricted limits

Question 2

Why is homeostasis important for organisms

Answer 2

Homeostasis is important
1. Maintains optimum conditions for enzyme action and cellular function

Question 3

Examples of physiological factors controlled by homeostasis

Answer 3

1. Core body temperature
2. Metabolic waste concentrations (urea + CO2)
3. Blood pH
4. Concentration of glucose in blood
5. Water potential of the blood
6. Concentration of respiratory gases in blood

Question 4

What is a hormone

Answer 4

Chemical substance released by endocrine glad that is carried by the blood to stimulate an effect on target organ

Question 5

Compare endothermic and ectotherms

Answer 5

Endotherms
- warm blooded
- heat from the inside

Ectotherms
- cold blooded creatures
- heat themselves by environmental conditions

Question 6

Where does body heat energy come from in endotherms

Answer 6

Externally
- mammals absorb solar radiation directly, or indirectly by radiation, conduction or convection from their environment

Internally
- as by product of metabolic rate, respiration

Question 7

Outline the role of hypothalamus in thermoregulation

Answer 7

Thermoregulation centre in hypothalamus initiates switching on/off heat loss/ conservation mechanism
(Two centres: hot control + cold control)
Thermoreceptors (heat sensitive neurones) monitor temperature

Question 8

What is negative feedback

Answer 8

When a change occurs in body it responds in such a way as to reverse the direction of change

Question 9

Mechanism for negative feedback

Answer 9

1) sensory receptor detects change (stimulus)
2) an integrating centre receives input from sensors and coordinates the response
3) effector carry out corrective actions to bring about a response
4) returning conditions to normal is negative feedback

Question 10

Annotate diagram on the control of body temperature

Answer 10

See notes

Question 11

Advantages and disadvantages of being ectotherm (cold blooded)

Answer 11

ADV:
- less food needed
- greater proportion of food energy for growth
DISADV:
- less active in cooler temperatures as need to warm up before can be active

Question 12

Advantages and disadvantages of being an endotherm (warm blooded)

Answer 12

ADV:
- can be active in cooler conditions
- enzymes can work efficiently all the time
- can inhabit at cooler regions
DISADV:
- significant proportion of food intake used to generate heat
- less food energy available for growth

Question 13

Types of peptide hormones and steroid hormones

Answer 13

PEPTIDE
- adrenaline
- insulin
-glucagon

STEROID
- oestrogen
- Progesterone

Question 14

What is the normal blood concentration of glucose

Answer 14

90mg/100cm3

Question 15

Symptoms of too low sugar levels

Answer 15

Respiration slows which reduces formation of ATP
Stops cellular processes
Brain cells die leading to fainting then death

Question 16

Symptoms of glucose levels in blood being too high

Answer 16

The blood water potential drops leading to cells losing water causing organ damage and failure leading to death in serve cases

Question 17

What is the role of the pancreas

Answer 17

In exocrine system (enzymes)
- produces enzymes in pancreatic duct for digestion
In endocrine system (hormones)
- islets of langerhans secrete hormones insulin & glucagon directly to blood stream to regulate glucose levels

Question 18

What happens to glucose in muscle/adipose and liver tissue

Answer 18

In Muscle/adipose tissue
- increase uptake due to increase glucose channels
M —> glycogen. A —> Fat

In liver tissue
- increase uptake increased diffusion
Converted glycogen or respired

Question 19

Process of lowering blood glucose levels in muscle or adipose cells

Answer 19

1) insulin binds to receptors
2) binding causes chemical signal inside cell
3) chemical signal effects vesicle causing it to fuse with membrane and release glucose carrier proteins onto membrane
4) increase the number of glucose carrier proteins
5) facilitated diffusion of glucose into cell increases
6) enzymes activated to turn glucose —> glycogen (muscle cell) or fat (adipose cell)

Question 20

Annotate insulin effect on muscle/ adipose cell diagram

Answer 20

Include
- insulin binding to receptors
-vesicle with glucose carrier proteins
- glucose carrier proteins onto membrane
- enzymes with glucose Turing to fat or glycogen

Question 21

Process of lowering blood glucose levels in liver cells

Answer 21

1) insulin binds to receptors proteins
2) chemical signal activates enzyme - phosphorylase
3) this reacts glucose with phosphate (phosphorylises)
4) this maintains conc gradient increasing uptake of glucose by diffusion
5) other enzymes stimulated which causes glycolysis and glycogenesis to occur

Question 22

Outline glucagon’s role in increasing blood glucose levels

Answer 22

• activation of enzymes in the liver
  Which increases glycogen breakdown (glycogenolysis)
  Glucose synthesised from lactate and amino acids (gluconeogenesis)

Question 23

Def of glycogenolysis

Answer 23

The process of glycogen breakdown into glucose

Question 24

Def of gluconeogenesis

Answer 24

The process of glucose being synthesised from lactate and amino acids

Question 25

What is the role of adrenaline in increasing blood glucose levels

Answer 25

Adrenaline affects the liver
- uses a second messenger
- increases glycogen breakdown (glycogenolysis)
- also inhibits enzyme glycogen synthase preventing production on glycogen so more glucose available

Question 26

What is secondary messenger system

Answer 26

Used by many hormones
It works to use 1 hormone molecule
- to produce many cAMP molecules
- and large amounts of enzymes
To causes response

Question 27

Annotate summary of glucose control

Answer 27

See notes
Too low
1. Alpha cells detect fall, glucagon secretion, in liver glycogen breakdown and synthesis of glucose

Too high
Beta cells detect rise, insulin secretion, increased uptake of glucose by adipose cells, muscle cells and liver tissue

Question 28

Information of the 1 diabetes

Answer 28

1) T-cells attack beta cells in pancreas decreasing insulin secreted
2) liver doesn’t store glycogen
- cannot replace glucose quickly
- neurones can only respire glucose to levels falls = coma
3) cells don’t take up glucose after meal
- glucose can rise too high affecting brain cells
4) treated with insulin
- injected or digested if taken orally

Question 29

Info on type 2 diabetes

Answer 29

• associated with obesity/ unbalanced diets
• receptors stops responding to insulin
  Beta-cells produce more
  If beta cells become damaged type 1 diabetes can develop
• can’t be treated with insulin