Homeostasis, pH, core body temperature and bodily fluids Flashcards
Define homeostasis
The process whereby cells. tissues and organism maintain the status quo
Explain negative and positive feedback loops
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.
Normal body temperature range
36.5-37.5
What happens when core body temp is low
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.
What happens when core body temp is high
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
What needs to be maintained in the bodies internal environment.
Concentration of -O2 -CO2, -salt -electrolytes(Na,K,Ca) -Nutrients -Waste products, pH Temperature, volume and pressure of water/fluids
Normal pH range
7.35-7.45
What maintains acid base balance
Lungs-respiratory balance
Kidneys-metabolic balance
What happens if gastric acid gets in the oesophagus and why?
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)
What happens if stomach loses its mucus lining?
Gastric ulceration and perforation
What does pH 5.8 indicate?
Cancer
What happens if pH changes by 0.3?
[H+] changes by a factor of 2
What do the intracellular buffer systems include?
Sodium Phosphate buffering system regulates intracellular pH and transport systems
Protein buffer systems- Haemoglobin(RBC only),
-amino acid buffers
What do the extracellular buffer systems include?
Carbonic acid-bicarbonate used in blood pH regulatory using erythrocytes as an intermediary (removes CO2)
Plasma protein buffers
Amino acid buffers
Do all the buffer systems regulate water?
Yes
Calcium’s relevance to buffer systems?
Its alkali so it raises pH
Clinical relevance of buffer systems
Antacids neutralise acid
Solubility is a factor (dont wanna mess with osmolality so insoluble is best eg aluminium hydoxide)
How do we find imbalances?
Arterial blood gas analysis
Too much water equals?
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.
Too little water equals?
Dehydration, cell, tissue and organism death
How much water is required?
2.5L
Avg water to everything else constitution of the avg male
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
What happens when there is not enough water
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.
Causes, symptoms and result of dehydration
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
Isotonic
Water potential is same on both sides of membrane
Hypotonic
Water potential is more negative in cell water moves in
Hypertonic
Water potential in cell is less negative so water moves out
Does water move through membrane,
Yes by diffusion
What do the integral protein aquaporins do?
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.
What do IV drips need?
Physiological saline concentrations (0.9% NaCl)
Osmolarity
mol/L, solute particles per litter depends on temp and pressure
Osmolality
osmol/L, solute particles per kg, does not depend on temp and pressure
Calculate osmolality
Glucose or urea is just millimoles present, ionic solutes need to be doubled if only 1 part is mentioned
Oedema
Fluid retention, peripheral oedema is swelling of ankles.
Caused by hydrostatic pressure>osmotic pressure leading to fluid build up in interstitial spaces.
What does oedema occur in
Congestive heart failure
liver cirrhosis
renal disease.
Factors affecting movement of fluid from capillaries?
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
Examples of positive feed back
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
Outline what happens when glucose level increase
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
Out of norm body temps
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
