Homeostasis, pH, core body temperature and bodily fluids

Question 1

Define homeostasis

Answer 1

The process whereby cells. tissues and organism maintain the status quo

Question 2

Explain negative and positive feedback loops

Answer 2

Feedback loops are cycles, they are made up of —

• Receptors which monitor,
• Control systems which evaluate,
• Effectors which create changes

Negative feedback loops reverse changes in controlled conditions, end when effector ceases.

Positive feedback loops strengthen changes in controlled conditions until initiator ceases.

Question 3

Normal body temperature range

Answer 3

36.5-37.5

Question 4

What happens when core body temp is low

Answer 4

Hypothalamus detects low core body temp,

Skeletal muscles begin shivering to generate heat,

Peripheral arterioles going towards skin contract restricting blood flow, reducing heat loss from skin,

Piloerection: Arrector pili contract causing hair on skin to stand up to trap warmer air

Curling up: reduces surface area.

Question 5

What happens when core body temp is high

Answer 5

Hypothalamus detects high core body temp,

Sudorific glands secrete sweat which removes heat when water evaporates.

Vasodilation: Arterioles going towards dilate to increase blood flow to skin to increase heat loss.

Pilorelaxation: Arrector pili relax causing hair on arms to lay down and trap less warm air.

Stretching out: increase surface area

Question 6

What needs to be maintained in the bodies internal environment.

Answer 6

Concentration of 
-O2
-CO2, 
-salt 
-electrolytes(Na,K,Ca)
-Nutrients
-Waste products,
pH
Temperature,
volume and pressure of water/fluids

Question 7

Normal pH range

Answer 7

7.35-7.45

Question 8

What maintains acid base balance

Answer 8

Lungs-respiratory balance

Kidneys-metabolic balance

Question 9

What happens if gastric acid gets in the oesophagus and why?

Answer 9

Oesophagitis-inflammation of lining of oesophagus
stricture-narrowing of the urethra restricting urine
Oesophagus has no goblet cells that secrete mucus to protect itself from stomach acid pH(1.5 to 3.5)

Question 10

What happens if stomach loses its mucus lining?

Answer 10

Gastric ulceration and perforation

Question 11

What does pH 5.8 indicate?

Answer 11

Cancer

Question 12

What happens if pH changes by 0.3?

Answer 12

[H+] changes by a factor of 2

Question 13

What do the intracellular buffer systems include?

Answer 13

Sodium Phosphate buffering system regulates intracellular pH and transport systems

Protein buffer systems- Haemoglobin(RBC only),
-amino acid buffers

Question 14

What do the extracellular buffer systems include?

Answer 14

Carbonic acid-bicarbonate used in blood pH regulatory using erythrocytes as an intermediary (removes CO2)

Plasma protein buffers

Amino acid buffers

Question 15

Do all the buffer systems regulate water?

Answer 15

Yes

Question 16

Calcium’s relevance to buffer systems?

Answer 16

Its alkali so it raises pH

Question 17

Clinical relevance of buffer systems

Answer 17

Antacids neutralise acid

Solubility is a factor (dont wanna mess with osmolality so insoluble is best eg aluminium hydoxide)

Question 18

How do we find imbalances?

Answer 18

Arterial blood gas analysis

Question 19

Too much water equals?

Answer 19

toxicity, metabolic failure (everything too diluted) and cell, tissue and organism death
Because:
-osmotic pressures too high,
-cells absorb water and swell till they burst,
-enzymes and proteins stop working.

Question 20

Too little water equals?

Answer 20

Dehydration, cell, tissue and organism death

Question 21

How much water is required?

Answer 21

2.5L

Question 22

Avg water to everything else constitution of the avg male

Answer 22

1avg male=0.4 solids + 0.6 fluids
0.6fluid=2/3intracellular fluid+1/3extracellular fluid
1/3extracellular fluid=0.75 interstitial fluid+ 0.25plasma

Question 23

What happens when there is not enough water

Answer 23

Cells/tissues absorb water from interstitial spaces
From each other
Once tissues dead water absorbed from organs
Once they’re water is absorbed from brain, liver, kidney and heart.

Question 24

Causes, symptoms and result of dehydration

Answer 24

Hot humid weather, excessive sweating, vomiting, diarrhoea and burns.
Thirst, dryness, water loss, osmolarity then ADH increase, oliguria(urine output is below 400ml/day )
Plasma volume decrease

Question 25

Isotonic

Answer 25

Water potential is same on both sides of membrane

Question 26

Hypotonic

Answer 26

Water potential is more negative in cell water moves in

Question 27

Hypertonic

Answer 27

Water potential in cell is less negative so water moves out

Question 28

Does water move through membrane,

Answer 28

Yes by diffusion

Question 29

What do the integral protein aquaporins do?

Answer 29

Allow bulk flow of water, some have different affinities to water control speed, this allows discrete water flow,
Regulated by the amount of glycerol in cells.

Question 30

What do IV drips need?

Answer 30

Physiological saline concentrations (0.9% NaCl)

Question 31

Osmolarity

Answer 31

mol/L, solute particles per litter depends on temp and pressure

Question 32

Osmolality

Answer 32

osmol/L, solute particles per kg, does not depend on temp and pressure

Question 33

Calculate osmolality

Answer 33

Glucose or urea is just millimoles present, ionic solutes need to be doubled if only 1 part is mentioned

Question 34

Oedema

Answer 34

Fluid retention, peripheral oedema is swelling of ankles.

Caused by hydrostatic pressure>osmotic pressure leading to fluid build up in interstitial spaces.

Question 35

What does oedema occur in

Answer 35

Congestive heart failure
liver cirrhosis
renal disease.

Question 36

Factors affecting movement of fluid from capillaries?

Answer 36

Capillary filtration pressure-fluid moves out of capillaries
Capillary colloidal osmotic pressure-fluid moves in capillaries
Tissue hydrostatic pressure- fluid moves into capillaries
Interstitial fluid pressure- fluid moves out of capillaries
Lymph channels- fluid moves out of capillaries and into channel
Presence of plasma proteins in the interstitial space
Lymphatics are blocked or damaged

Question 37

Examples of positive feed back

Answer 37

Blood clotting:
-break/tear of blood vessel
-platelets adhere to site and release chemicals
attracting more platelets.
-carries on till bleeding stops or out of platelets

Baby pushing against cervix:

• cervix stretches
• stretching sends nerve impulse to brain
• brain stimulates pituitary to secrete oxytocin
• oxytocin causes uterus to contract
• baby pushes cervix again and cycle repeats till baby pushed out

Question 38

Outline what happens when glucose level increase

Answer 38

Blood glucose increase detected by insulin secreting cells of pancreas
Pancreas secretes insulin
Insulin causes liver and most body cells to take up glucose and store as glycogen

Question 39

Out of norm body temps

Answer 39

46c+ heat exhaustion- unconsciousness, fitting, seizures, confused, restless, headache, dizzy, uncomfortable
40c heat stroke flushed dry skin, hot to the touch, strong bounding pulse
36c mild hypothermia-shivering, fatigue, slurred speech, confusion, forgetfulness, muscle stiffness
32c severe hypothermia- shivering stops, muscles become rigid, very slow, weak pulse noticeable drowsiness, severe reduction in response levels
28c No vital signs- unconsciousness, dilated pupils, pulse undetectable, appearance of death, cyanosis-blue skin