1 Homeostasis Flashcards
Definition
Homeo is defined as sameness and stasis as standing still
Definition 2
The process whereby cells, tissues and organisms maintain the status quo
Disrupters
Changes a homeostatic parameter (running, on a hot day)
Detectors
Detect disruption
Control system and effectors
Bring it back into homeostatic range
Things needed for chemical reactions in cells
Correct pH Correct temp Sufficient glucose and O2 Volume and pressure Amino acids, fats, vitamins, minerals Correct amount of hormones Correct amount of water Correct amount of electrolytes (Na, K, Cl)
Cells produce
CO2
NH3
Negative feedback when hot
Vasodilation
Sweating
Pilorelaxation
Stretching out
Negative feedback when cold
Vasoconstriction
Shivering
Piloerection
Curling up
Negative feedback blood glucose
Blood glucose rises, detected by insulin-secreting cells of pancreas, pancreases secretes insulin, liver takes up glucose, blood glucose levels decrease, insulin release stops
Positive feedback
Output enhances or exaggerates original stimulus
Stops when initiator ceases
Positive feedback blood clotting
Break in blood vessel wall, clothing occurs as platelets adhere to site and release chemicals, released chemicals attract more platelets, clotting proceeds, newly forming clot grows, feedback cycle ends after clot seals break
Positive feedback childbirth
Baby pushes against cervix causing it to stretch, causes nerve impulses sent to brain, brain stimulates pituitary it release oxytocin, oxytocin causes uterus to contract
Negative feedback
When conditions change from ideal or set point and returns conditions to this set point
Stops when effector ceases
Core body temp
36.5-37.5 degrees
Older people have lower temp, athletes have even lower temp
Immune system works more effectively at higher temp
Increased body temp
Hypothalamus activates cooling mechanisms, skin blood vessels dilate, sweat glands activated, body temp decreases, thermostat shuts of cooling mechanisms
Decreased body temp
Hypothalamus activates warming mechanisms, skin blood vessels constrict, skeletal muscles activated (shivering), body temp increases, thermostat shuts off warming mechanisms
> 46.5 degrees
Heat exhaustion
Unconsciousness, fitting, confused, headache, dizzy
40.5-46.5 degrees
Heat stroke
Flushed dry skin, hot to the touch, strong pulse
37.5-40.5 degrees
Fever/pyrexia
Pale sweaty skin, cramps in stomach, arms, legs
36.5-37.5 degrees
Normal
32-36.5 degrees
Mild hypothermia
Shivering, fatigue, slurred speech, confusion
28-32 degrees
Severe hypothermia
Shivering stops, muscles become rigid, slow weak pulse, sever reduction in response levels
<28 degrees
No vital signs
Unconsciousness, dilated pupils, pulse undetectable, appearance of death
Not dead until warm and dead
Acid-base balance
Normal pH 7.35-7.45 2 major organs responsible for maintaining balance are lungs and kidneys pH 6.8 = disease symptoms begin pH 5.8 = cancer cells begin to form pH 3.5 = human body cannot sustain life
Acidosis
6.8-7.35 pH
Alkalosis
7.45-7.8 pH
[H+]
Change in [H+] by factor 2 causes pH change of 0.3
Buffer systems
Intracellular fluid (ICF) include phosphate and protein
(Haemoglobin, amino acid, plasma) buffer systems
Carbonic acid is important in blood for erythrocytes
Other cells use sodium phosphate buffering system
All systems regulate water
Antacids (Al(OH)3) neutralise acids
Blood gas analysis
Arterial blood gas analyses pH and gases
Shows metabolite values
Fluid balance
2.5l per day
Intake: metabolism, food, drinking
Output: faeces, skin, breathing, urine
Total body water
60% normal male 50% normal female 70% normal infant Higher % body fat, lower % water 2/3 is ICF, 1/3 is ECF 80% of ECF is interstitial, 20% is plasma
Isotonic
Same amount of water on both sides of plasma membrane
Hypertonic
Solute concentration inside cell lower than outside so water moves out (shrinks)
Hypotonic
Solute concentration inside cell higher than outside so water moves in (swells)
If not enough water in cells
Cells and tissues initially absorb water from interstitial space
Then absorb water from each other
Then as tissues die, water absorbed from organs
As organs die, water absorbed from brain, liver and lastly kidney and heart
Aquaporins
Control amount of after that moves in and out of cells
Integral membrane proteins
Different aquaporins have different affinities for water
Regulated by amount of glycerol in cell
If too much water
Osmotic pressure high
Cells absorb water and swell
Enzymes and proteins stop working as they can’t meet each other
Cells keep swelling until burst
Patient needs isotonic solutions, IV drips need saline concentrations (0.9% NaCl)
Dehydration
Water loss
Thirst/dryness, decrease in plasma volume, increase in osmolarity
Increase in ADH
Oliguria (less urine output)
Osmolality
Concentration of all solutes in a given weight of water
mOsm/kg
Oedema
Fluid retention Peripheral oedema Hydrostatic pressure>osmotic pressure Lymphatics blocked or damaged Presence of plasma proteins in interstitial space
