Lecture 1 Flashcards
What is homeostasis?
A constant internal environment, in which conditions must be carefully maintained. Cells can only survive jn a narrow range on conditions.
Physiology definition
The study of how the body functions
What are the two systems that control all other body systems together ?
The nervous system and the endocrine system.
The nervous system and endocrine system either
A)________
Or
b)________
A) maintain homeostasis
B) permit departures from homeostasis in uncontrolled manner. Like pregnant and growth.
Describe feedback mechanisms
A response to changes in the system. The set point of a variable are the range of variable values that do not elicit a response. Variables are monitored by receptors.
Describe the pathway for a feedback mechanisms :
Stimulus (sensory info) –> Receptor> control center (CnS) –> effector (output) –> Response
Describe Negative feedback
The most common mechanism of homeostatic control.
The OUTPUT functions to reduce the INPUT and moves variable back to set point.
Give an example of negative feedback using body temperature as a variable
Set point: 36 - 37.8 c
Patient has temp of 40 deg. c.
Temp detected by cells of hypothalamus (imput)
Sweat glands activated. (Effector) smooth muscles of vessels then relax. Result»_space; increased heat loss and decrease in body temp.
What is positive feedback and give an example
Less common feedback mechanism,
The output intensifies the input and the original stimulus increases.
Eg: uterine contractions during labour.
Increased contractions (input)
Sends message to posterior pituitary
Oxytocin is released
Oxytocin increases the contractions (output)
______ soluable vitamins can easily cross the phospholipid bilayer
Fat
There are several types of membrane proteins, what are they ?
Transport (channel, carrier), enzyme, receptor proteins, anchoring proteins
Transport proteins ( channels): describe
Form a pore in a cell membrane
Allow movement of WATER and ions
MAY be gated so they may leak since they are always open
Describe carrier proteins (which are transport proteins)
Carrier proteins bind to solutes and shuttle them across the membrane
Used for both facilitated diffusion AND ACTIVE TRANSPORT
Describe receptor proteins
These bind very specific extracellular molecules called ligands.
Eg: hormones and neurotransmitter
Give an example of a receptor protein interacting with insulin.
Insulin binds to receptor on skeletal muscle. This triggers movement of more glucose transporters onto cell membrane to increase glucose movement from blood into cell.
Define enzymes
Give an example of an enzyme on surface of muscle cell
Enzymes control reactions taking place on the inner or outer membrane surface
Example acetylcholinesterase on post synaptic neurons
And Na+ K+ ATPase pump in all cells
Describe 3 ways in which anchoring or joining proteins are used
I) ANCHOR cell membrane to cytoskeleton OR adjacent cells
Ii) junctional proteins
III) extracellular fibers (usually glycoproteins)
What can membrane carbohydrates be joined with? What are their names and function?
Glycoproteins and glycolipids
Function in cell recognition
What are the different methods of passive diffusion ?
Simple diffusion
Facilitated diffusion
Osmosis
Describe simple diffusion:
What type of molecules are normally involved with simple diffusion ?
Movement of SOLUTES across the membrane.
Simple diffusion always moves from an area of high concentration to low.
Involves small lipid soluable molecules such as oxygen and carbon dioxide. Ions may also cross the membrane through protein channels (charge indicates hydrophilic)
Describe facilitated diffusion
Movement of charged or water soluable molecules down their concentration gradient using CARRIER PROTEINS.
Describe osmosis
This is the movement of solvent (water) rather than the movement of solute.
If there is a semipermeable membrane water will move from the area with low concentration to an area that has high concentration.
The cell membrane is permeable to water because of a channel protein called
Aquaporin
Or through the lipid bilayer
______ is the desired method of transport
Diffusion , because no energy is required
What is osmotic pressure
This is the pressure that must be applied in order to prevent the movement of water across a membrane.
If there is a solution with pure water on both sides of a membrane what is he osmotic pressure equal to ?
0
If there is a solution of pure water on one side of a membrane and a concentration of 10% Na+Cl- on the other there will_____
Be a higher osmotic pressure associated with the membrane system.
High solute concentration means ____ osmotic pressure.
High
Define tonicity
Describes the behaviour of a cell immersed in solution. The tonicity is dependant on the concentration of solutes present and the permeability of the membrane to solutes.
What is a hypotonic solution
The solution is less concentrated than the cells interior
Water moves into the cell
Cell will swell and potentially burst
What is hemolysis
When a red blood cell bursts
Can happen when placed in water
Hypertonic solutions :
The cell exterior is more concentrated than it’s interior
The cell shrivels
Ex: RBC placed in 10% Na+Cl-
How can brain swelling be decreased (edema)?
A 10% glucose solution injection.
Because sucrose is not permeable to membrane, water must move to high concentration.
Explain how sweating will lead to feeling of thirst.
When the body loses fluid via swear the blood becomes concentrated. This concentration within the blood will pull water from the surrounding tissues into the blood
Response is thirst, and decreasing H20 excretion at the kidney level
What is a hydrostatic pressure ?
Pressure of fluid pressing against a surface
Example
Cell membrane, blood vessel wall = blood pressure
What is filtration ?
When fluid flows out of blood.
What is absorption?
When fluid flows into blood.
What is the difference between osmotic pressure and hydrostatic pressure ?
Hydrostatic pressure is the pressure of fluid on both sides of a membrane
Osmotic pressure is a tendency of water to move into a more concentrated solution.
The direction of fluid movement in capillaries is determined by balance of
A)
B)
A) hydrostatic pressure
B) osmotic pressure due to presence of large non-diffusable proteins
Net filtration pressure formula
(bhp + Isfop) - (ishp + bop)
What is active transport ?
An active process. Movement of material via active transport uses ATP supply. Movement of solutes against the concentration gradient.
Solutes move from low concentration to high concentration.
True or false. Active transport makes the use of protein carriers ?
True
There is primary active transport an secondary, which is called a pump ? Example ?
Primary. ATP breakdown is apart of the transport process
Eg; Na+ K+ ATPase
What is secondary active transport ?
Co-transport (use of ATP is indirect)
Eg glucose entry into the small intestine
What are the steps in secondary active transport
1) primary active transport via Na+ K+ ATPase pump stores energy by creating concentration gradient for sodium entry into the cell
2) Na+ diffuses back across membrane through a membrane cotransporter protein
It drives glucose against it’s concentration gradient into cell.
What is vesicular transport ?
Includes movement of a vesicle in or out of a cell. A vesicle is a substance surrounded by a membrane within a cell.
Endocytosis - exocytosis
What is Endocytosis ?
Movement into cell
I) phagocytosis - large items moving into cell, like bacteria ; cell eating
II) pinocytosis- fluids into cell , cell drinking
What is Exocytosis ?
Movement of vesicle out of cell , can contain hormones, enzymes, nT
Fuse at cell membrane and opens to release contents to ECF
Requires calcium
