Homeostasis Flashcards
What is meant by ‘homeostasis’? Describe it.
Homeostasis means ‘similar condition’. Basically keeping conditions optimal in the body.
What are our bodies constantly doing?
monitoring their internal state, responding to disruptions in a constant effort to maintain optimum ‘similar conditions’
Define tissue
a group of cells that share the same characteristics or specialisation ie work together to carry out a particular function.
Define system
group of organs working together to perform a specific function
Define organ
Collections of tissues that are usually of different types that synchronise to perform a specific function.
Define reflex
An action or movement that is not controlled by conscious thought (doesn’t go through conscious brain)
Homeostasis mechanisms are represented by reflexes .
What is the equation of life? and describe it
nutrients + O2 = energy (ATP) + CO2 + waste
02 breaks down nutrients like fats/lipids
supply and demand is important. If the demand for O2 goes up then the supply of substrates to produce energy also goes up to meet demand.
what is N.F.C? What are characteristics of it?
Negative feedback control (most common type)
Aim: to restore internal environment to optimal conditions.
Characteristics: 1. Oscillation around the set point- a range where variation of set point is okay. 2. Cannot prevent variable from causing disturbance but once it has happened it can restore regulated variable.
Process: Receptors detect disturbance in regulated variable and feed info into to integrating centre in the brain. Info is compared with reference level. Any difference between actual and reference level generates another signal which is fed to effector mechanism. Produces a response to correct original change.
Define an insensible loss
Water loss. Not aware but it’s happening all the time i.e skin and breath ie evapouration etc
What is P.F.C
Positive feedback control. This moves a system further away from target of equilibrium. When the product of a reaction leads to an incease in that reaction occuring. Initial disturbance sets off a train of events that lead to even greater disturbance.
What are feed forward systems
With these you can to some extent predict and prevent the change from happening. Additional receptors permit system to anticipate change and activate cahange earlier. (forward- think looking into future- predicting it)
Why is water balance crucial?
Crucial as if it is messed up, every other homeostatic process is messed up. Have to lose however much water we put into our bodies to keep a balance.
Discuss plasma. Composition?
Plasma is the fluid component of blood. It’s capillary walls are thin enough to allow movement of nutrients into I.S.F. Plasma proteins are too large to cross the capillary wall so the I.S.F is devoid of plasma protein.
Composition- 95% water, 5% is ions, nurients, plasma proteins etc
What happens if homeostasis doesn’t work effectively?
May not allow for normal functioning of the body. K+ conc increases outwith the normal range outside of the cell then there is a loss of concentration gradient between the E.C.F and I.C.F and this disrupts nerve and muscle function.
glucose and homeostasis
When muscle and liver cells cannot take up Glucose from the blood, the body fools itself into thinking it is starving. The liver releases glucose ino the blood stream from its stores. Which further increases b.g.c. This leads to uncontrolled hyperglycaemia which can ultimately cause death.
Where is water in our body?
Water in our body is split into 3 compartments. Intracellular fluid, interstitial fluid and plasma. Water can move freely between the 3 compartments and osmosis determines where the water will go.
What is the ratio of E.C.F to I.C.F (total water conc.) in the body?
1/3 E.C.F 2/3 I.C.F
What does the kidney determine?
urinary losses and regulates output of water
Describe drug delivery and water concentration link
A lipid soluble drug will be stored in fat. A water soluble drug stays in E.C.F in the blood and fluid around cells. If drug stays in blood then this causes H20 to move into the plasma to retain equilibrium and then plasma volume increases.
Ion movement within across the 3 compartments- discuss
Ions pass freely through the capillary wall but not the cell membrane. So they move between plasma and I.S.F within the E.C.F. Nutrients like O2 and CO2 also move freely across the cell membrane.
Electrical gradient- how do they occur? Link to the concentration gradient?
- They occur due to charged particles.
- These particles go down their electrical gradients.
- concentration gradient and electrical gradient may go in the same or different direction.
- If working in opposite ways then ions go down the biggest gradient. This doesn’t require energy UNLESS they’re moving against the gradient
What is exocytosis?
-Membrane-bound secretory vesicles are transported to the cell membrane.
-The membrane diffuses with the cell membrane.
-The membrane surrounding substances disintegrates + substance is pushed out of cell.
ie release of neurotransmitters or hormones.
What is endocytosis?
- Form of bulk transport- cell transports molecules into the cell by engulfing them.
- Energy using process
- Used often with cell signalling
- uncontrolled cell division occurs when endocytosis is disrupted
Describe diffusion in general.
- Important process of movement across membrane.
- depending on the permeability- molecules will diffuse through the membrane to reach equilibrium
- Move from a high conc to a low conc down the conc gradient
- Molecules constantly moving back and forth- high chance molecules bump against membrane again and move back BUT the net flux is from a high to a low concentration.
- Bigger the conc gradient- bigger the movement.
Diffusion through lipid bilayer- discuss
Molecules need to be small, lypophilic (hydrophobic) and uncharged
O2 and N2 small uncharged and lipophilic rapid movement
CO2 and urea small uncharged lipophobic relatively easy movement
Glucose- large uncharged lipophobic- more slowly
ions- small charged - extremely slow
What are aquaporins?
Aquaporins are channel proteins that H20 moves through. They are always open (pore) hence why there is no barrier to water movement.
Transport channels- ligand-gated?
When a chemical like neurotransmitter/ hormone binds to binding site they open/close
What is facilitated transport?
Natural movement process. Down their electrochemical gradient.
What is active transport?
molecules moving through transport proteins against their electrochemical gradient requiring energy in form of ATP
Describe in detail the Na+/K+ pump
It’s a repetitive cycle
the affinities of Na+ and K+ change
will not accept Na+ into the cell
the unequal movement of Na+ and K+ creates an equal gradient- cellular processes use this gradient
3 Na+ from ICF bind phosphate group phosphyorylates ATPase causing conformational change. 3Na+ out 2 K+ from E.C.F bind phosphate is released. Another conformational change and the 2K+ are released into the I.C.F
Enzyme proteins
Can be intra or extra cellular
catalyse chemical reactions on cell membrane
What is a peripheral protein?
Only in the hydrophilic part of phospholipid bilayer
What is an integral protein?
span the length of the membrane. Have hydrophobic and hydrophilic parts
Describe Osmosis meaning
Osmosis is the net movement of H20 from regions with high H20 conc to low H20 concentration.
Define osmolarity
TOTAL NO. OF PARTICLES IN SOLUTION
Measures concentration of biological solutions in units of ‘osmoles’. It ONLY describes the no. of particles in solution nothing about the nature of the particles
Define tonicity
TOTAL NO. OF NON-PENETRATING PARTICLES
It’s more important as it determines cell volume
osmotic pressure?
To make the volumes equal again and try oppose an increase in volume the pressure required is called the O.P
How does homeostasis work effectively?
Na/K+ pump mechanism
How come intracellular proteins and organic anions (-ve ions) stay inside the cell?
Cell membranes are effecitvely impermeable to them.
How come ions like Na+, K+ and Cl- cross the lipid bilayer much faster than predicted rate?
due to transporter proteins on membrane.
Transport proteins- voltage-gated
Electrical signal causes conformational change. In muscle and nerve cells. Alterations in membrane electrical potential
How do you determine cell volume?
Volume of a cell at any time is dependent on the concentration of non-penetrating solutes on either side of the membrane.
What is H20 conc. inversely related to?
the conc. of solute as the more solute particles there are in solution, the more they displace H20 molecules which lowers the H20 concentration
define hypo-osmotic
a solution with fewer total solute particles.
define hyper- osmotic
solution with greater no of total solute particles
T or F: does the no. of particles inside the cell= the no. particles outside the cell
True but the composition of particles ie penetrating/ non-penetrating/ ion species differ vastly
isosmotic
a solution with the same total no. of solute particles as E.C.F (plasma) or having the same osmotic pressure
