Homeostasis and body fluids

Question 1

what happens when body gets too little water

Answer 1

dehydration

cell,tissue and organism death

plasmolysis

Question 2

what happens when the body gets too much water

Answer 2

toxicity

metabolic failure

cell,tissue,organ death

Question 3

describe the water compartments in the average male (70kg)

Answer 3

• 60% of 70kg is 42L (total body water)
• intracellular fluid is 2/3 of total body water - 2/3 x 42 = 28L
• extracellular fluid is 1/3 of total body water - 1/3 x 42 = 14L
• interstitial fluid volume is 3/4 of extracellular fluid - 3/4 x 14 =10.5L
• plasma volume is 1/4 of extracellular fluid - 1/4 x 14 =3.5L

the volume of blood for a 70Kg male is approx. 5L

Question 4

examples of positive feedback loops

Answer 4

oxytocin released during childbirth due to the increasing pressure of the head on the cervix.

regulation of blood clotting

Question 5

what is the difference between a negative feedback loop and a positive feedback loop

Answer 5

negative = the effector causes an effect to reduce the stimulus. stops when the effector ceases

positive = the effector causes an effect that increases the effect of the stimulus. stops when the stimulus ceases.

Question 6

what is extracellular fluid and what proportion of the body does it make up

Answer 6

water outside cells

1/3 of total body water

Question 7

what it intracellular fluid and what proportion of the body does it make up

Answer 7

water inside cells

2/3 of the total body water

Question 8

in elderly people, what percentage of their body is water

Answer 8

50% because they have larger adipose tissue content

Question 9

what percentage of the body is water in a baby

Answer 9

80%

Question 10

what percentage of the adult human body is water

Answer 10

60%

Question 11

one way to treat heartburn or other things caused by acids

Answer 11

over the counter antacids eg. aluminium hydroxide

this neutralises acid

antacids containing aluminium hydroxides are preferred as they are milder, longer lasting, fewer side effects , more soluble, can pass through easily.

Question 12

describe some acid problems that can occur with gastric juice

Answer 12

it can go into the oesophagus, causing severe issues

the stomach has a protective lining and if it gets damaged or lost then it can lead to gastric ulceration and perforation.

heartburn

Question 13

what is the ph of gastric juice in the stomach

Answer 13

1-2.5

Question 14

one way of treating acidosis

Answer 14

infusion of a bicarbonate solution can help increase blood pH

mechanical ventilation can be used for respiratory acidosis to remove the carbon dioxide.

Question 15

what are the 2 main causes of acidosis

Answer 15

1) metabolic acidosis

• due to increased production of metabolic acids (eg lactic acid)
• inability to excrete acid via kidneys
• controlled by kidneys

2) respiratory acidosis

• caused by excessive build of carbon dioxide due to hyperventilation

Question 16

what is alkalosis

Answer 16

increase in blood pH above 7.45

Question 17

what are the symptoms of acidosis

Answer 17

central:

• headache
• sleepiness
• confusion
• loss of consciousness
• coma

respiratory:

• shortness of breath
• coughing

heart:

• increased heart rate
• arrhythmia

gastric:

• nausea
• vomiting

muscular:

• seizures
• weakness

intestinal:

• diarrhoea

Question 18

what is acidosis

Answer 18

when the blood pH falls below 7.35

Question 19

what is the normal pH of blood

Answer 19

7.4

Question 20

what is homeostasis with respect to pH

Answer 20

the regulation of hydrogen ion concentration

acid-base balance

Question 21

what is a cause of pyrexia

how does that cause pyrexia?

Answer 21

infection

The infection causes the set point in the hypothalamus to increase to a higher temperature. this causes the body to initiate heat generation via shivering and increased metabolic rate to meat the set point which is at a higher temperature.

above 38.5oC = pyrexia (fever)

this increase in temperature is important becomes it is at these temperatures that the immune system works optimally.

Question 22

what is pyrexia

Answer 22

a fever

temp above 38.5 oC

Question 23

what is normal body temperature for humans

Answer 23

37oC +/- 0.5oC

Question 24

what are ways in which the body can cool down

Answer 24

sweating - water evaporates and since water has a high latent heat of vaporisation, the change is state from liquid to gas removes a lot of energy from the body, cooling it down.

vasodilation of arterioles near the skin, increasing blood pressure and increasing heat loss through skin

hairs in skin lay flat and surface of body cools

Question 25

describes ways in which body temperature can be increased

Answer 25

shivering of skeletal muscles

heat released through metabolic reactions and respiration

vasodilation of the arterioles, decreasing blood flow through them and reducing heat lost through skin

erection of hairs in the skin (piloerection)

Question 26

what is the function of the hypothalamus

Answer 26

measures the internal body temperature

location of the set point and its control

Question 27

name the 4 components needed for a homeostatic mechanism to work properly

Answer 27

stimulus/variable

sensor/receptor

a control centre

an effector

Question 28

what are 3 key factors that need to remain constant in the body?

Answer 28

ph

temperature

water

Question 29

Define the term homeostasis

Answer 29

physiological process

internal conditions of the body of a living organism, cell or tissue are maintained despite changes in factors both extrinsic and intrinsic.

state of dynamic equilibrium