Infection & Homeostasis

Question 1

Mechanisms to produce or retain heat

Answer 1

Shivering
Vasoconstriction of blood vessels in skin
Increased metabolic reactions
Decrease in body SA:volume

Question 2

Mechanisms to lose heat

Answer 2

Sweating
Vasodilation of blood vessels in skin
Increase in body SA:volume

Question 3

How can behaviour change heat gain or loss?

Answer 3

Can change body SA:volume ratio of body to external environment to either increase of decrease rate of heat exchange.
Changing the environment.
Reducing temperature difference between body and surroundings.
Increasing or decreasing activity which is heat producing.

Question 4

How does sweat cool down the body?

Answer 4

Sweat glands secrete sweat under the control of the sympathetic NS. The sweat evaporated which absorbs heat, thus the body loses heat. Heat is needed for liquid -> gas, so it is taken from the skin = lowers body temperature.

Question 5

Vasodilation and vasoconstriction

Answer 5

Vasodilation: blood vessels in skin expand because smooth muscles relax and blood flow through them is increased.
Vasoconstriction: blood vessels in skin reduce in size as smooth muscles contract and blood flow is decreased.

Question 6

Shivering

Answer 6

Very rapid contraction and relaxation of skeletal muscles. Initiated by the hypothalamus. These contractions are not used in moving parts of the body so the heat generated by the metabolic reactions involved contributes to the internal heat of the body.

Question 7

Piloerection

Answer 7

Contraction of muscles that are attached to each hair. The rising of the hair serves as insulation as it retains heat.

Question 8

Liver

Answer 8

Stores glycogen, converts to glucose when required.

Question 9

Muscles

Answer 9

During muscular activity, glycogen -> lactate -> blood glucose in liver

Question 10

Gluconeogenesis

Answer 10

Conversion of lipids and amino acids into glucose in liver.

Question 11

Hypoglycaemia symptoms

Answer 11

Blurry vision, shakiness, increased heart rate, dizziness.

Question 12

Is a person with Type 1 diabetes or Type 2 diabetes more likely to suffer from
hypoglycaemia?

Answer 12

Type 1
Insulin injections may be too frequent/ contain too much insulin which would
cause cells to take up too much glucose, dropping the blood sugar level.

Question 13

Lymph

Answer 13

In lymph vessels, doesn’t contain RBCs or platelets, usually has a low protein concentration.

Question 14

Osmotic pressure

Answer 14

The movement of water through a semi-permeable creates a pressure or force due to a difference in concentration of solute on either side of the membrane. The greater the difference, the greater the pressure.

Question 15

How much filtrate and urine is produced each day by an average person? What happens to the filtrate?

Answer 15

Filtrate: 180L
Urine: 800-2000 mL/day
The filtrate is reabsorbed back into the body via the nephrons and collecting duct.

Question 16

What is urea? Where is it produced, why do we have to excrete it?

Answer 16

Urea is a nitrogenous waste formed in the liver. There the deamination of amino acids produces ammonia - a highly toxic substance. Carbon dioxide combines with it to form a less poisonous substance, urea, which is a soluble organic salt of small molecular size easily transported in the blood and eliminated via kidneys.

Question 17

Kidneys

Answer 17

Regulate the composition and volume of blood. Wastes are removed as urine. Wastes include excess water, nitrogenous substances from protein catabolism, hydrogen ions, inorganic ions.

Question 18

Aortic body, carotid body, respiratory centre

Answer 18

Aortic body: in aortic arch, is a chemoreceptor.
Carotid body: in carotid artery, is a chemoreceptor.
Respiratory centre: in medulla oblongata, has chemoreceptors for pH.

Question 19

CO2 and O2 transport

Answer 19

CO2 is transported in the plasma as dissolved bicarbonate ions.
O2 combines with haemoglobin in RBCs to form oxyhaemoglobin.

Question 20

Hyperventilation and diving

Answer 20

Hyperventilation: forced deep rapid breathing.
Greatly reduced CO2 level = takes a long time to build up to a level required to stimulate breathing.
While under water, O2 used up = unconscious.
When CO2 increase enough to stimulate breathing -> no conscious thought, breath, take in water, drown.
HYPERVENTILATION DOES NOT INCREASE BLOOD O2 LEVEL AS HAEMOGLOBIN IS ALMOST 100% SATURATED.

Question 20

Fluid circulation

Answer 20

At the arterial end of a capillary there is a mass flow of plasma and nutrients from the bloodstream into the tissue fluid - because BP is greater than OP.
At the venous end of a capillary there is a mass flow of tissue fluid and wastes from the tissues into the bloodstream - because OP is greater than BP.

Question 21

Hormones involved in heat

Answer 21

Adrenaline and thyroxine increase metabolic rate -> increases heat production.

Question 22

Inflammatory response

Answer 22

Dilation of blood vessels and increased permeability of capillaries, allowing plasma to leak into surrounding tissue and leucocytes to access the area more easily (RESULTS IN SWELLING, REDNESS, HEAT, PAIN). Swelling and pain reduces movement, helps confine pathogens to the area.

Question 23

Chemotaxis in inflammatory response

Answer 23

Phagocytes are attracted to affected area.

Question 24

Inflammatory response

Answer 24

Mechanical damage cause mast cells to be activated by complement proteins.
Mast cells secrete chemicals into tissue fluid.
Complement system proteins and some chemicals released by mast cells attract phagocytes.
Abnormal conditions stimulate pain receptors.
Phagocytes filled with bacteria, debris and dead cells, die. Forms pus.
Repair takes place.

Question 25

Histamine

Answer 25

Increases blood flow via vasodilation, making blood capillaries more permeable. More fluid moves through capillary walls into tissue.

Question 26

Heparin

Answer 26

Prevents clotting of the immediate area. Clot of the fluid forms around damaged area so pathogens can’t spread further.

Question 27

Inflammation purpose

Answer 27

Reduce the spread of any pathogens, destroy them and prevent entry of additional pathogens.
Remove damaged tissue and cell debris.
Being repair of damaged tissue.q

Question 28

Fever

Answer 28

Due to pyrogens, especially interleukin-1, which are predominantly produced by macrophages.
When the set point is at a higher level.

Question 29

Fever benefits

Answer 29

• Inhibits growth of some bacteria and viruses.
• Heat speeds up chemical reactions, which allows body cells to repair themselves more quickly during a disease.
• Inhibits viral replication by allowing interferons to operate faster.

Question 30

Lymphatic system

Answer 30

Collects some of the fluid that escapes from the blood capillaries and returns it to the circulatory system.

Question 31

Cell Replacement Therapy

Answer 31

1. Stem cells are isolated.
2. Stem cells are cultured.
3. Stem cells are differentiated into neural cells.
4. Neural cells are reintroduced into damaged areas of the brain.
   Early research of stem cells being introduced into the affected areas of the brain have showed promising results due to stem cells differentiating and replacing damaged cells.
   Highly controversial due to destruction of embryo cells.

Question 32

What organs secrete substances with a low pH and how does the low pH provide defence?

Answer 32

Stomach, vagina, skin.
Low pH = acidic. Acidity kills most microorganisms by rupturing the cell wall of affecting microorganisms.

Question 33

How do the various mucus provide defence?

Answer 33

Mucus that lines digestive track - protects from physical damage and chemical damage by providing a physical barrier, thus pathogens cannot move into internal environment. Pathogens get trapped and then removed.
Mucus that lines respiratory track - traps pathogens and is swept to the top of the trachea by cilia and swallowed, thus being destroyed in stomach by acids and enzymes.

Question 34

What cells recognise the pathogens as ‘no-self’ cells? What is their reaction to the detection of these invaders?

Answer 34

Macrophages - recognise pathogens by cell surface receptors that differ between the pathogen and the body cells. They engulf cells recognised as non-self.

Question 35

Explain the relationship between carbon dioxide concentration and blood pH.

Answer 35

CO2 combines with water to form carbonic acid, which as it is toxic, breaks down to form hydrogen ions and bicarbonate ions. CO2 is carried in blood as bicarbonate ions. Hydrogen ions determine blood pH.

Question 36

Beofre firefighters enter burning buildings, they will often unconsciously hyperventilate. Suggest how and why this may adversely affect them.

Answer 36

Hyperventilation greatly reduces the amount of carbon dioxide in the blood, but oxygen levels remain relatively unchanged.
Physical activity uses up oxygen before the urge to breath is triggered, which could cause them to run out of oxygen and blackout in the building.

Question 37

Describe the key ethical points researchers would have to be aware of prior to any animal testing taking place

Answer 37

Replacement of animals with other means wherever possible.
Reduction of number of animals used (in the experiment).
(Refinement of methodology to) minimise harm to the animals.