Intro To Body Log

Question 1

Negative feedback

Answer 1

Idea that a stimulus that shifts the bodies internal environment causes the body to try and “get the body back to normal”

E.g. body temperature exceeds 37 —> sensed by nerve cells in skin and brain —> targets temperature regulatory centre in the brain —> stimualtes glands throughout the body

Glands secrete sweat which cools body down, therefore negatively feedbacking on exceeding body temp

Question 2

Positive feedback

Answer 2

In positive feedback systems, the output enhances or exaggerates the original stimulus e.g. regulation of blood clotting

Question 3

Core body temperature

Answer 3

The normal human body temperature range is typically stated as 36.5–37.5 °C

The normal human body temperature range is stated as 37 ± 0.5 °C (source NHS)

But core temperature fluctuates throughout the day and shows a circadian rhythm

Older people have lower body temperature

Athletic people in a hot environment can have a very low body temp

Women during menstrual cycle fluctuate between 1 degree

Core temperature is the torso and head where the vital organs are, and the hypothalamus controls the body temperature

Question 4

What happens when core body temperature is outside normal range

Answer 4

36-37 = normal 
38-40 = fever with achy bone 
41-45 = heat stroke - strong bounding pulse 
46+ = heat exhaustion - unconsciousness, dizzy, seizures 

36-32 = mild hypothermia - shivering, fatigue, confusion 
31-28 = severe hypothermia - shivering stops, muscles become rigid, weak pulse 
27> = no vital signs - unconscious, dilated pupils, pulse undetectable - appearance of death - not dead until warm and dead

Question 5

Acid base balance

Answer 5

Human body must be maintained in very narrow range of acid-base balance

Normal pH is 7.35-7.45 - normal cellular metabolism occurs in this range

2 major organs responsible for maintaining acid base balance are - lungs/respiratory balance, the kidneys/metabolic balance

Gastric pH is normally between 1.5 and 3.5. Therefore very acid. If gastric acid gets into the oesophagus can cause severe problems (oesophagitis, stricture).

If the stomach loses its protection (mucus) can lead to gastric ulceration and perforation.

Question 6

Buffering systems in the body

Answer 6

Carbonic acid – Bicarbonate IMPORTANT in blood Uses Erythrocytes as an intermediary

Other cells use a Sodium Phosphate buffering system to regulate intracellular pH and transport systems

All systems also regulate water levels in the cells
e.g. antacids neutralise acids by virtue of their alkalinity, But also their solubility is a factor – aluminium hydroxide is MILDLY alkaline, but because it is insoluble is a good neutraliser.

Question 7

Fluid balance

Answer 7

Cells, tissues, organs all need the right amount of water

Not enough – dehydration and cell, tissue, organism death

Too much – toxicity, metabolic failure and cell, tissue, organism death

Fluid needs to be tightly controlled through discrete intake and output mechanisms

Key controller is water distribution around the body

Approximately 2.5 Litres of fluid is needed each day to maintain
a healthy adult

Question 8

How much water is in each compartment

Answer 8

70 kg male x (60/100%) = 42kg (Litres) = Total Body water

Intracellular Fluid Volume is 2/3 of total body water = 2/3 x 42L = 28 Litres

Extracellular Fluid Volume is 1/3 of total body water = 1/3 x 42L = 14 Litres

Interstitial Fluid Volume is 80% of ECF volume = (80/100%) x 14L = 11.2 Litres

Plasma volume is 20% of ECF volume = (20/100%) x 14L = 2.8 Litres

But, in practice numbers are rounded up and down, so:

ICF volume = 11 litres and plasma = 3 litres

Question 9

Tonicity

Answer 9

Iso = the same amount of water on both sides of the plasma membrane

Hyper = less water inside the cell or solute conc outside the cell is higher so water rushes out of cells

Hypo = less water outside the cell or solute conc inside the cell is higher so water rushes in

The movement of water is always down its concentration gradient by diffusion – process is called osmosis

Question 10

Oedema

Answer 10

Oedema is fluid retention.

It used to be called ‘dropsy’.

Peripheral oedema is commonly called ‘swollen ankles’ or ‘ankle
swelling’, resulting from the retention of fluid.

Hydrostatic pressure>osmotic/oncotic pressure - causing more water to be driven outwards in the interstitial spaces - plus presence of plasma proteins seen in the interstitial space (e.g. albumin)

This occurs in congestive heart failure and liver cirrhosis