Body Logistics Lecture 1

Question 1

Define homeostasis

Answer 1

The process whereby cells, tissues and organisms maintain the status quo.

Question 2

Explain negative and positive feedback loops

Answer 2

Stimulus —> sensor —> control centre —> effector
The above is the sequence for both feedback loops, but +ve is where the stimulus is exacerbated and -ve is when the effector brings the stimulus back to what it usually is.

Question 3

What is the normal range of core body temperature?

Answer 3

37 C +- 0.5C

Question 4

Describe the mechanism that occurs if the body temperature is too high

Answer 4

• The thermostat in the hypothalamus activates cooling mechanisms.
• Vasodilation of skin blood vessels, sweat glands secrete sweat, pilorelaxation (hairs lay flat).
• Body temp decreases (-ve feedback).

Question 5

Describe the mechanism that occurs if the body temperature is too low

Answer 5

-Stimulus is decreased body temp.
- Thermostat in hypothalamus activates warming mechanisms.
- Vasoconstriction of skin blood vessels, shivering, hairs on skin stand up, increasing metabolism.
- Body temp increases.

Question 6

What are the temperate ranges for hyperthermia?

Answer 6

> 38 FEVER pale, sweaty skin, cramps in stomach, arms and legs.

> 40 HEAT STROKE flushed dry skin, hot to the touch, strong bounding pulse.

> 40 HEAT EXHAUSTION unconsciousness, fitting, seizures, confusion, restless, headache, dizzy, uncomfortable.

Question 7

What are the temperature ranges for hypothermia?

Answer 7

32-35 MILD HYPOTHERMIA shivering, fatigue, slurred speech, confusion, forgetfulness, muscle stiffness.

28-32 SEVERE HYPOTHERMIA shivering stops, muscles become rigid, very slow and weak pulse, noticeable drowsiness.

<28 No vital signs, severe reduction in pulse, unconsciousness, dilated pupils, appearance of death. Not dead until warm (treated and warmed up).

Question 8

What is the normal range of pH values in humans?

Answer 8

Normal blood pH is 7.35-7.45.

<7 DEATH

7-7.35 ACIDOSIS

7.45-7.8 ALKALOSIS

> 7.8 DEATH

Cancer cells begin to form at 5.8.

Limits of human tissue survival are from 6.8 to 7.8.

Question 9

How does pH change with [H+]?

Answer 9

PH = -log10[H+]

An increase of pH by 0.3 means [H+] doubles.
A decrease of pH by 0.3 means [H+] halves.

Question 10

What are symptoms and causes of acidosis?

Answer 10

Headaches, confusion, tiredness, tremors, coma.

1. METABOLIC ACIDOSIS - due to increased production of metabolic acids e.g. lactic acid or inability to excrete acid via kidneys.
2. RESPIRATORY AIDOSIS - build up of C due to hypoventilation or as a response to metabolic alkalosis.

Question 11

What is the pH of stomach acid and why isn’t this too low?

Answer 11

1-2.5.
The stomach contains musucs which prevents it from damaging the stomach.

Question 12

How is heartburn treated?

Answer 12

Over-the-counter antacids which contain weak (basic) salts e.g. aluminium hydroxide, magnesium hydroxide and calcium salts. They neutralise the pH by binding to the free H+ ions that are present.

Question 13

What mechanisms control pH?

Answer 13

Lungs maintain the respiratory balance.
Kidneys maintain the metabolic balance.

Fig.1 on revision notability.

Question 14

Calculate how much water is in a ‘standard adult male’.

Answer 14

He is 70kg. 60% is water.

Therefore, 42 litres of water.

1/3 of this is extracellular fluid and 2/3 is intracellular fluid.

Of the extracellular water, 3/4 is interstitial water and 1/4 is circulating blood volume (plasma).

Fig.2 on revision notability.

Question 15

Calculate Total Body Water (TBW) in others.

Answer 15

Adult male Adult Female Infant

Normal 60% 50% 70%

Lean 70% 60% 80%

Obese 50% 42% 60%

Elderly typically have more fat

Question 16

Define Hypotonic, Isotonic and Hypertonic

Answer 16

Isotonic = Amount of water transported into cell is equal to amount of water transported out from cell.

Hypotonic = More water outside the cell, more solutes inside cell. The cells swell from osmosis.

Hypertonic = More water inside cell and solute conc is lower inside cell. Water is transported out of the cell by osmosis.

Question 17

Explain the concept of osmolality

Answer 17

Osmolality is the concentration of a solution expressed in total number of solute particles per kg (mOsm/kg).
High osmolality is when the conc is high.
Total osmolality is adding the concentrations together.
If some of the particles are chlorides, you have to include the Cl- ions too.

Normal range for oncotic pressure is 280-300mOsm/kg.

Question 18

What happens if there’s not enough or too much water?

Answer 18

NOT ENOUGH: Cells and tissues absorb water from interstitial space, then from each other. Then from organs as tissues die. Then organs die. Brain dies first.

TOO MUCH: Osmotic pressure is high. Cells absorb water and swell. Enzymes and proteins stop working. Cells swell until they burst.
Patients are given isotonic solutions. It has physiological saline with 0.9%NaCl.

Question 19

What is Odema?

Answer 19

Fluid retention.
Occurs when hydrostatic pressure is greater than osmotic pressure.
There is more water moving out of capillaries than in due to blood hydrostatic pressure. This can cause congestive heart failure, liver cirrhosis and renal disease.

Question 20

Define hydrostatic pressure, osmotic pressure and oncotic pressure

Answer 20

HYDROSTATIC PRESSURE = The force exerted by the fluid on the vessel wall (from the inside).

OSMOTIC PRESSURE = Force applied by the solute to prevent osmotic movement across the membrane.

ONCOTIC PRESURE = Colloid osmotic pressure. THE MORE PROTEINS SOMETHING HAS, THE HIGHER THE ONCOTIC PRESSURE.