Physiology Flashcards
Define homeostasis.
Cells and tissues have to keep a state of equilibrium within a set range.
What is the range?
What the body perceives to be normal.
Name the 3 types of communication.
Autocrine cell to cell.
Paracrine cell to tissue.
Endocrine cell to the whole body.
What are the steps to a negative feedback loop?
- Sensor detects and measures a parameter.
- Internal set point acts as a comparator.
- Output signal changes paramater back to set point
- Ouptut activates effector.
What happens in more complex loops?
Can have synergistic and antagonistic loops, as well as multiple loops for one parameter if it’s very important.
What do adaptation and acclimatisation mean?
Where the range for a parameter changes due to exposure to an extreme for a long time.
What causes homeostasis?
Change in a stimulus. Chemical, electrical or mechanical.
What makes up body fluid?
Extracellular fluid - interstitial and plasma. Intracellular fluid. Urine, vaginal and seminal fluid etc.
What is a solvent?
What is a solute?
A solvent is fluid in the body.
A solute is dissolved substances in water.
What is the distribution of bodily fluids?
42 litres in total, 26 is intracellular, 13 of interstitial and 3 of plasma. 5 litres of blood in total.
What is blood plasma?
Blood consists of plasma and cells. Cells do not dissolve so only plasma classed as bodily fluid.
Name some electrolytes in body fluid.
Name some non-electrolytes in body fluid.
Ca2+, K+, Cl-, proteins and organic ions.
Glucose, phospholipids, cholesterol and urea.
Roles of fluid in the body?
Transport, site of reactions, lubrication, cushioning and regulation of temp by sweating.
What are electrolytes needed for?
Cell signalling, action potentials, acid-base balance, muscle contraction and osmosis.
What happens if there is disruption to body fluids?
Dehydration if too little water. Hyponatraemia - too much water which dilutes electrolytes, oedema from too much water, swelling from a vascular compartment in interstitial space.
Describe the symptoms of mild dehydration.
Less than 3 litres. Dry lips, dark urine and thirst.
Describe the symptoms of severe dehydration.
More than 7 litres. Loss of skin turgor, sunken eyeballs, confusion, decreased capillary refill and postural drop in bp.
Why are the young and elderly more vulnerable to dehydration?
Young - immature kidneys, higher SA:V ration, metabolism is higher.
Elderly - less water in bodies, decreased kidney function, many medications are diuretics.
What is diffusion?
Passive movement of molecules from an area of high conc to an area of lower conc.
What is osmosis?
Movement of a solvent through a membrane impermeable to solutes.
What is osmolarity?
It is the number of moles in 1 litre of water. It is dependent on temperature, so higher osmolarity lowers the freezing point.
What is osmolality?
It is the number of moles in 1 kg of water. Independent of temperature.
What is osmotic pressure?
The pressure required to stop the flow of solvent through membrane it is proportional to osmotic strength.
What is oncotic pressure?
Exerted by proteins.
When does fluid move?
Moves due to hydrostatic pressure in the capillary and in the tissue, oncotic pressure in the capillary and interstitium.
What is net filtration pressure?
(Capillary hydrostatic pressure - tissue interstitial pressure) - (capillary oncotic pressure - tissue interstitial pressure)
What is tonicity?
What happens in isotonic, hypertonic and hypotonic solutions.
Effect when you have 2 solutions.
Isotonic solution - no net movement
Hypertonic - net movement out of cells
Hypotonic - net movement into cell
