Lecture 2: Principles of Homeostasis Flashcards
What does ECF stand for?
Extracellular Fluid
What is the homeostatic benefit of being a multi-cellular organism?
Cells specialise and combine to make tissues and organ systems, allowing for control of a stable internal environment.
How much of our body water is contained in ICF?
2/3
What does ICF stand for?
Intracellular Fluid
How much of our body water is contained in ECF?
1/3
How much of the ECF is ISF?
approx. 4/5
What does ISF stand for?
Interstitial Fluid
How much of the ECF is plasma?
approx. 1/5
What is the definition of ‘Homeostasis’?
The maintenance of relatively constant conditions in the internal environment (ECF) in the face of external (or internal) change.
What is the K+ concentration in the ECF?
3.5-5mmol/L
What is the glucose concentration in the ECF?
Fasting = 3.5-6mmol/L Non-Fasting = 3.5-8mmol/L
What is the Ca++ concentration in the ECF?
2.2-2.6mmol/L
What is the Na+ concentration in the ECF?
135-145mmol/L
What is the role of Sodium in the ECF?
Action potential generation and ECF volume control, affecting blood pressure (BP).
What is the role of Calcium in the ECF?
Structural component of bone and teeth, involved in neurotransmission, muscle contraction, essential for blood clotting, regulates enzyme function.
What is the role of glucose in the ECF?
To produce ATP.
What are the effects of acidosis?
Decreased neural function, decreased consciousness.
What are the effects of alkalosis?
Over-excitable nerves and muscles, leading to ‘pins and needles’, muscle spasms and convulsions.
What is the optimal core body temperature?
36-37.5 ° C
What happens when the core body temperature is too high?
Proteins denature.
What happens when the core body temperature is too low?
Chemical reactions slow down, preventing normal cell function. As nerve cells cease to function properly, the body can no longer thermoregulate, temperatures decrease, and the cycle continues… ☠
_________ is the random movement apart of particles, which is rapid over a short distance, for example, between cells and capillaries.
DIFFUSION is the random movement apart of particles, which is rapid over a short distance, for example, between cells and capillaries.
Is energy required for simple diffusion? Why?
No. Because it is a passive mode of transport, molecules travel down the concentration gradient with no extra energy required.
Can all substances diffuse through the lipid bilayer?
No, only some substances can.
What are membrane channels?
They are channels through the cell membrane which allow for the movement of (often specific) molecules through them. They can often open and close.
Which type of membrane channel opens/closes spontaneously?
Leak Channels
What are ligand gated channels?
Membrane channels which open/close in response to a change.
What are voltage gated channels?
Membrane channels which open/close in response to membrane potential.
What is another name for Carrier Mediated Passive Transport?
Facilitated Diffusion.
How does Carrier Mediated Passive Transport work?
Proteins within the cell membrane bind to molecules outside the cell, change their shape and then release them into the cell.
What is it called when energy from ATP hydrolysis is used to move substances against the concentration gradient?
Primary Active Transport
The sodium - potassium pump is an example of what type of transport?
Primary Active Transport
3Na⁺ out, 2K⁺ in
Active transport maintains _____ _________.
Active transport maintains IONIC GRADIENTS.
What is exocytosis?
A process by which the contents of a cell vacuole are released to the exterior through fusion of the vacuole membrane with the cell membrane.
What is endocytosis?
The taking in of matter by a living cell by invagination of its membrane to form a vacuole.
What is osmosis?
The net movement of water across a membrane DOWN its own concentration gradient (towards the higher solute concentration).
What causes osmotic pressure?
Differences in solute concentration, due to fluid shifts.
What is osmolarity?
The total number of solute particles per liter of solution.
What is tonicity?
The effect a solution has on a cell. Eg., hypertonic, hypotonic, isotonic.
What is the osmolalirity of the ECF and ICF?
275-300mosmol/L
What is the pH of the ECF?
7.35-7.45
