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Midterm #1


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T/F, solutions inside and outside a cell exhange water by osmosis
Where is [K] higher?
-inside an animal cell
Where is [Na] higher?
-outside the cell
Where is [Cl] higher?
-outside the cell
What does the second law of thermodynamics state?
-an isolated system can change in only certain, limited ways.
What is the proper definition of equilibrium?
-the state toward wich a system moves, internally, when it has no inputs or oujtputs of energy or matter. Eventually reaches a stable manner
What is simple diffusion?
-the transport that arises from the molecular agitation that exists in all systems above absolute zero and from the simple statistical tendency for such agitation to carry more molecules out of regions of relatively high concntration than into such regions
What is homeostasis?
-internal constancy and the physiological regulatory systems that automatically make adjustments to maintain it
What does homeostasis involve?
1) Negative Feedback

2) Positive Feedback

3) Feedforward
What is negative feedback?
-acts to reduce the difference between a desired setpoint and the actual value within a controlled and narrowed range.
What is feed forward?
-consequences of a behavior are anticipated
-actions taken in advane to limit effect (eg: migration, hibernation, rats drinking before eating, Pavlov's dogs)
What is positive feedback?
-it is used to amplify the effect (ie: increases the differenece between the actual value and the set point)

-beneficial to...
a)rapidly move a process towards an extreme
b)maintain momentum of response
What are some properties water that make them important to biology/physiology? 13 of them.
1)composed of 1O and 2H
2)very polar because of unequal charge distribution
3)forms hydrogen bonds with polar molecules
4)universal solvent-high dielectric constant
5)dissolves electrolytes and nonelectrolytes
6)undergoes ionization; forms hydration sphere
7)electrolyte solutions conduct electric current
8)less dense as a solid than a liquid
9)has a high specific heat and heat capactiy
10)has high latent heat of vaporization
11)has high surface tension and surface energy
12)has a low viscosity
What is a hydration sphere?
-a hydration sphere is the insulation boundary that water makes around an ion.

**the hydration sphere is larger around small ions because smaller ions would have a larger strength/surface area ratio**
Define solution.
-a homogeneous mixture of 2 or more substances which are molecularily dispersed
Define suspension.
-the shit that falls out of solution due to gravity. The anti-solution
What is a mole?
-the counting unit for 6.02E23 particles
What is molarity?
-the # of moles/L
What is molality?
-the # of moles/Kg
Define osmolarity.
-a unit to describe osmotic pressure

**a solution has an osmotic pressure of 1 osmolar if it has the same osmotic pressure as a 1-M solution of ideal nonelectrolyte**
What are 3 major solutes in bodily fluids?
1)Inorganic ions (non carbons)

2)Ionic organic solutes (carbon containing solutes)

3)Nonionic organic solutes
What are 2 functions of extracellular fluid?
1)acts as a buffer (pH, temp, ionic, nutrient, gas, etc.) between cell and external environment.

2)provides optimum conditions for cellular activities
What are osmoconformers?
-maintains osmotic concentration of extracellular fluids similar to environment
What are osmoregulators?
-maintains osmotic concentration of extracellular fluids different from environment
-requires energy and physiology
What are ionoregulators?
-maintains extracellular concentration of specific ions at a level different from the environment
What does the intracellular fluid consist of in most animals?
1)a lower total inorganic ion concentration

2)mostly K instead of Na

3)numerous organic solutes
What is it about crab eating frogs (Rana cancrivorn) that allows it to live in seawater rather than freshwater?
-can live in marine water because internal fluids have high concentration of urea
-this brings their bodily fluids closer to that of seawater
Why is K more abundant inside the cell than Na is?
-Na has a higher charge density than K
-K can exist in the cell because it has a smaller hydration sphere, therefor taking up less free water than Na would
-if Na were inside the cell, majority of water would be bound and physiological activities would not function normally
How do lipid solutes(hydrophobic) move through a cell membrane?
-they dissolve in the lipid interior of a cell membrane
-then they move from an area of high concentration to an area of low concentration(like normal)
-then they move out
How do inorganic ions(hydrophilic) move through a cell membrane?
-they can't dissolve and move through the hydrophobic tails so they've gotta do something else...
-they move through via ion channels
What are ion channels?
-ion channels are gated channels that can open and close
-they are highly selective
What are the 7 categories of gated ion channels?
1)Ungated/Leak channels: forever open

2)Voltage gated channels: they open and close in response to changes in the voltage difference across a membrane, important in the generation of nerve impulses

3)Chemically Sensitive Gated Channels: respond to chemical stimuli (ie:hormones) to open channels

4)Mechanical or Energy Sensitive Channels: responds to mechanical deformation of membrane or other energy forms (eg: protons)

5)Stretch gated channels: open or close in response o stretching or pulling forces that alter the physical tension on a membrane

6)Phosphorylation gated channels: open or close to whether the channel proteins are phosphorylated

7)Ligand gated channels: ligand binding results in a change in conformation of the receptor protein

**Note, the first 4 are the ones learned in class. Know those, be aware of the others**
What 6 factors influence the rate of diffusion?
1)Concentration gradient
2)Charge (repulsion and attraction)
3)Volume and visocity of medium
4)Mass/Size of particle (smaller is faster, hydration sphere)
5)Chemical structure
What theory would you use to describe diffusion?
-you would use the Kinetic theory. Just think about it... Shit
What is the diffusion coefficient?
-an empirical measurement for each molecule which incorporates the influence of charge, size and chemical structure on diffusion rate.

**SI = sq. m/sec**
What is Ficks first law? What is it used for?
***J = -DA[C/X]***

*Where: J=quantity/time
D=diffusion coefficient
A=area of diffusion
C=concentration difference
X=distance between solutions

-used to calculate the rate of diffusion
-'ve just means that diffusion is occurring from high to low
What is the atmosphere composed of?
-N2 78%
-O2 21%
-CO2 0.03%
-Ar 0.94%
-others 0.082%
What is the ratio between atm and mmHg?
1atm = 760mmHg
What 4 laws govern the behavior of gases?
1)Universal/Ideal gas law

2)Boyles law: Volume

3)Dalton's law: Partial Pressure

4)Henry's law
What 2 functions must any aerobic organism be able to perform?
1)supply it's cell with dissolved oxygen

2)disposeof CO2 produced during metabolism
What 5 factors influence the solubility of gases in water?
1)partial pressure

2)atmospheric pressure

3)dissolved solutes


5)nature of the solvent
What is gas tension?
-term used to describe the amount of gas dissolved in liquid
How is partial pressure related to Henry's Law?
-the molarity of a dissolved gas in a liquid is directly prportional to the partial pressure of that gas

*** Vg/Vl = (Bunsens' Coefficient)Pg ***

Bunsens' Solubility Coefficient: describes the solubility of gases in water. Equals the volume of gas at STP, which will dissolve in a unit volume of solvent when the Pg of the gas is 1 atm
What are the conditions at STP?
Pressure = 1atm = 760mmHg

Temp = 0C
What is hemoglobin for?
-it is for the transport of oxygen
-the solubility of oxygen is low, therefor it wouldn't be able to dissolve into the blood and thus cannot be dilivered throughout the system.

-on the other hand, the solubility of CO2 is high and can dissolve, therefore it doesn't need a vehicle such as hemoglobin to be delivered
What happens to the volume and the partial pressure of a gas as you increase in altitude?
-volume of gas will increase
-partial pressure of each gas will decrease
What happens to the volume and the partial pressure of a gas as water depth increases?
-volume of gas will decrease
-partial pressure will increase
What effect do dissolved ionic solid solutes have on the solubility of gases?
-ionic solid solutes decrease the amount of dissolved gases
-according to Kinetic Theory, gases move so randomly, solids sit there, gases hit the solids and bounce off... Simple as that

**Amount of dissolved gas is not influenced by other gases. This is because gas particles are too small therefor the probability of collision is minimal**
What effect does temperature have on the solubility of gases?
-solubility of gases in water is inversely proportional to temp
(ie: high in cold temp, low in high temp)

**Again, use Kinetic theory to explain**
What is the Partitient coefficient (K)?
-is a ratio of solubility of gas in another liquid relative to it's solubility in water
(ie: for N, K=5.2 therefore N is 5.2 times more soluble in solvent X than it is in water)
What does Graham's Law state?
-says that at a constant temperature and pressure, the rate of movement of a gas through a vaccuum is inversely proportional to the square root of it's mass

*[Rate of Movement] = [1/(sq.rt. Mass]*
Define an Arrhenius acid and base.
-Acid: is an ionic compound which produces an excess of H ions in a water solution

-Base: is an ionic compound that produces an excess of OH ions in a water solution
What is a salt?
-an ionic compound that is made up of any cation other than H and any anion other than OH
What is a buffer?
-a solution of ionic compounds which resists a change in pH more effectively than would be expected following the addition of base or acid

-usually composed of a weak acid/base and it's salt
What are major buffer systems in biological fluids based on? 3 things.
-bicarbonate anions (HCO3)
-phosphate anions
-anionic proteins
What are constitutive properties of solutions?
-are properties that depend on chemical and molecular properties of the solutes and or solvent
What are colligative properties of solutions?
-physical properites of a solution that depends only on the amount/concentration of dissolved solute, not on the kind of solute
What are the 4 kinds of effects of colligative properties?
1)lowering of vapor pressure

2)increasing boiling point

3)decreases the freezing point


**All dissolved solutes contribute to teh colligative properties**
What is a colloid?
-is a general term for most matter organized into particles ranging in size from 1 to about 100nm in diameter (relatively large)
-includes: high molecular proteins, nucleic acid, phospholipids, etc
-are irregularily shaped particles
-biologically important ones are hydrated
-most colloids exist as suspension, NOT a true solution. Electronic attractions keep them together, easy to centrigue, can generate pellets
What is osmotic pressure?
-the mechanical pressure required to prevent the movement of wter across a semipermeable membrane

**a 1 osmolar solution will have an osmotic pressure of about 22.4atm at 0C**
What is the Van't Hoff equation? What is it used for?
pi = CRT
*Where pi=osmotic pressure
R=universal gas constant
T=absolute temerature

-used to determine osmotic pressure
What is the tensile solvent hypothesis?
-a hypothesis that is used to explain osmosis
-based on the second law of thermodynamics
-solutes decrease the cohesive forces holding water molecules together, reducing the internal tension and therefore increasing entropy
-more water is free to move on sides with more solute
-this water passes through the membrane

**tensile solvent hypothesis is only one of many hypothesis used to explain osmosis**
Whats the difference between intrinsic and extrinsic proteins?
-intrinsic proteins go through the lipid bilayer

-extrinsic proteins do not go through the lipid bilayer
What are the 3 main general functions of the cell membrane?
1)Compartmentalize and isolation

2)Reception and transduction of information

3)Generation and conduction of bioelectricity

**These functions are determined by the chemistry and ultrastructure of the cell membrane**
Define and organelles in a capillary and explain their functions.
1)Endothelial cells: acts as the bouncer, only on cell layer thick, lets blood in/out through clefts or through the cell itself. These cells have a nucleus

2)Cleft: space between Endothelial cells. Acts like a strainer, allowing properly sized shit through

3)Basement membrane: A super duper thin protein layer that serves just to keep everything else together. Very permeable, if it can pass endothelium cells, it can pass the basement membrane
What determines the movement of fluids across a capillary?
1) Mechanical fluid pressure

2) Colloid osmotic pressure
What is colloid osmotic pressure?
-the osmotic pressure exerted by water because of dissolved proteins and colloids in blood or interstitial fluid
What are the major colloidial proteins found in human plasma(100ml)?
-Albumen: 4.5g
-Globulus: 2.5g
-Fibringes: 0.3g

**for a total of 7.3g/100ml**
What are the 3 forces that influence fluid flow within a capillary?
1)Blood pressure
2)negative interstitial fluid pressure
3)Interstitial/Plasma colloidal osmotic pressure (COP)
What pressures do blood pressure, neg. pressure and COP contribute to the arterial side of the capillary?
-Blood pressure = 25mmHg out
-neg. pressure = 6.3mmHg out
-COP = 5.0mmHg out
-COP = 28mmHg in

**Net outward movement = 8.3mmHg out**
What pressures do blood pressure, neg. pressure and COP contribute to the venous side of the capillary?
-Blood pressure = 10mmHg out
-neg. pressure = 6.3mmHg out
-COP = 5.0mmHg out
-COP = 28mmHg in

**net inward movement on venous
side = 6.7mmHg**
What is the overall net outward movement in a capillary?
-1.6mmHg out
What is the purpose of lymph vessels?
-on average, the human capillary leaks about 1.7ml of fluid/min
-this interstitial fluid then becomes lymph fluid
-lymph fluid is collected by the lymph vessles and are returned to the venous system

**think about why people with high blood pressure are susceptible to swelling**
What are passive exchange mechanisms?
-potential engergy of electrochemical gradients provide the energy to move across the membrane

-molecules will move with the gradient (ie: [hi]->[lo] or [+'ve]->[-'ve])
What are active exchange mechanisms?
-the require energy from ATP to move substances against the electrochemicl gradient (ie: [lo]->[hi] or [-'ve]->[+'ve])
What are membrane ion channels?
-they are composed of intrinsic protein molecules which traverse the lipid bilayer
-forms an aqueous pathway for the transmembrane movement of specific molecules (ie: ions that are charged and have hydration spheres)
How do membrane ion channels allow selectivity? 3 reasons.
1)Size specific: acts like a strainer

2)Ionic charge: inner walls are charged and can therefor attract wanted ions while repelling unwanted ions

3)Other chemical characteristics: we didn't go into depth about this
What 2 factors affect the rate of Passive Transport?
1)concentration gradient

What is facilitated diffusion?
-it is a form of passive diffusion but involves 'carrier proteins' to move molecules through the membrane
Give 2 examples of facilitated diffusion in humans.
1)Glucose moves cell to cell by fac. diff. Insulin opens gates so that glucose can move from blood to cell be fac. diff. **Glucose concentration on inside of cell is always lower than outside becuase it always gets phosporolated upon entry**

2)The chloride shift in RBC's. BandIII is the carriers protein that moves HCO3 out while bringing Cl in. This is also done done fac. diff.
What's the difference between simple and facilitated diffusion?
-facilitated diffusion is saturable (ie: will plateau). The carrier proteins are rate limiting because they can all be 'busy' at any given time.

-if graphing a rate of transport vs. concentration of substance, fac. diff. would be a logarithmic curve, simple diff would be a positive, linear graph
What is active transport?
-transport that uses a saturable carrier protein pump
-can move substances against the gradient
-ATP is used to phsphorylate carrier proteins and releases energy, ultimately alters protein chape
-causes a conformational change in carrier protein to transer substrate to the other side
What is primary active transport?
-the energy for primary active transport is derived directly from ATP

(ex: Na-K pump 3Na out : 2K in)
**you know the relative inside/outside concentration gradients. These obviously go against the flow**
What is secondary active transport?
-energy for transpor is derived indirectly
-energy is from the concentration gradient set up by primary active transport
-often transports 2 substances at once b/c carrier protein has binding site for 2 molecules
-one moves down the conc. grad, the other moves against the conc. grad (counter transport)
-both omve in the same direction, despite conc. grad (co-transport)
What is current?
-the flow of charged particles
What is potential?
-the difference in electrical charge between 2 regions
What 3 ways do all living cells create transmembrane potentials?
1)Electrongenic Na-K pump: -5 to -10mV

2)Donnan equilibrium: -5mV

3)Diffusion equilibrium potentials:
What are the 3 types of membrane potentials in cells?
1)Resting membrane potential: all cells have insides which are -'ve to the exterior

2)Graded potentials: found in dendrites of neurons. small transient change in membrane potential

3)Action potentials: found in axons and muscle membranes. causes a large, transient change in membrane potential. It is ALL or NOTHING
Define 'polarized'.
-potential DOES NOT = 0
Define 'depolarized'.
-potential = 0

***caused by injecting +'ve current***
Define 'repolarization'.
-occurs when potential returns to resting state
Define 'hyperpolarization'.
-occurs when potential decreases past resting

***caused by injecting -'ve current***
Define 'resistance'.
-the ability to resis flow of current
-the inverse of conductance (g)
-measured in Ohm's
Define 'capacitance'.
-the ability to store electrical charge
-measured in farads (F)
List some specialized areas on a neuron.
-axon hillock: spike initiation
-axon terminal: synaptic boutons
-cell body and dendrites: reception/integration
-axon and terminal: impulse conduction (action potentials)
Why does measured potential decrease as you increase distance away from original stimulus?
-Membrane resistance (Rm)
-Axonal resistance (Ri)
-Ions leak out of the cell as well
What is the length constant? Denoted by the greek symbol lambda.
-the length constant is the point at which the measured potential is approx 37% that of the original source.
-it is a distance value

***length constant = sq.rt.(Rm/Ri)***
What is Ohm's Law?
V = IR
What is capacitive current(Ic)?
-term current is used 'loosely'
-charge accumulates on the outside of the membrane, thus effecting the charge on the inside.
-ions won't flow through the membrane, rather, their charge effects the ions on the other side, either repelling or attracting
-Capacitor seperates the charge
What is resistive current (Ir)?
-the tendency for ion channels to resist ion flow through it's channels

***Im = Ic +Ir***

***Ir is the biggest contributor***
In terms of potential, what is the difference between resistive and capacitive current?
-resistive current is instant, that is, any change in current results in an immediate and similar change to potential

-capacitive current takes time to charge, potential may not reach a max until some time after the current is applied.
What is tau? Denoted by that little 't' looking thing.
-tau is the time constant used to describe the time it takes to reach 63% of the final voltage

***tau = Rm X Cm***
What happens when you measure the potential caused by the membrane current (Im)?
-the potential graph looks like a tidal wave travelling to the left
What is the Nernst Equation?
-it describes E for a single ion (ie: how the ion contributes to resting potential)

***E = 58 log([ion out]/[ion in])***
What's the point of Na/K pumps?
-pumps 3Na out and 2K in to maintain proper resting potential
-membrane between in and out of cell is rather impermeable to prevent leakage, therefor pump is needed to move ions since ions can't simply diffuse to where they need to be.
What is the Goldman Equation?
-like the Nernst except it factors in multiple ions at one time

**E = 58 log((Pk[K]o/Pk[K]i)+
We know that Permeability is proportional to Potential. How can we change permeability so that we can control potential?
-open more channels (more Na, becomes depolarized. More K, becomes hyperpolarized)

-or close channels
What's the purpose of action potentials?
-they are needed to transfer info over big distances
-they are fast(1ms) reversals of Vm (-65mV to +40mV)
-it's an all or nothing mechanism (if threshold is reached). Therefore will not dissapate with time and distance like a graded potential would
-self propagating (up to 100m/s)
Whats the difference between graded potentials and action potentials?
-graded potentials are potentials beneath the threshold

-action potentials are potentials above the threshold
What mechanisms are responsible for maintaining the cells resting potential?
-the Na/K pump and the Donnan equilibrium.

***keeps the inside relatively -'ve to the outside***
Describe the steps that occur during an action potential. approx 7.
1)Current is applied and Na channels open:
-PNa increases, Na moves in fast because of the concentration gradient
-Depolarizes(increase in positive charge quickly)
-therefore you see that huge voltage jump from -'ve to +'ve

2)Vm approaches E(Na) but not past

3)Na channels inactivate(close)
-PNa decreases

4)At the same time, gated K channles open
-some K leaves the cell, therefor some +'ve charge leaves
-Pk increases and causes repolarization
-Vm approaches E(K)

5)Gated K channels stay open longer than Na channels
-therefor we get really close to E(K), hyperpolarization

6)Na channels are reactivated, but stay closed

7)Gated K channels close
-resting Vm is restored
What does action potential propagation rely on?
-passive local current (electrotonic)
-spread (cable properties)
-regenerative conduction (voltage gated ion channels)
How does action potential propagation work?
-Na influx creates a local current
-the current spreads in both directions from locus of action potential
-creates a capacitive current.

-capacitive current changes the charge distribution across the membrane
-neg charge builds up on inner membrane surface
-pos charge builds up on outer membrane surface
-this depolarization causes a stimulus 4-5X greater then the threshold
-adjacent Na channels open and cycle repeats.
-the presence of a refractory period ensures unidirectional propagation

**SIZ has a slightly lower threshold b/c more channels**
**Once SIZ starts, it won't stop. ALL OR NOTHING!!!***
What cable properties would you manipulate to increase the conduction velocity (CV)?
1)Increase the length constant, lambda:
increases the distance of local current spread in a given time period.
Done by increasing diameter or Rm

2)Decrease the time constant, tau:
decreases the time for Vm in adjacent regions to reach threshold (ie: AP is generated in less time over a given distance)
Done by increasing # of Na channels

3)Increase the temperature:
Channel kinetics increase with temperature so things happen faster. Increase T, decreases tau = faster CV
What effect do myelin sheaths have on conduction velocity?
-the presence of myelin sheaths increases conduction velocity.

-with myeline sheaths, there are no voltage gated channels in the internodes. Therefore AP's can only occur at the nodes - called Saltatory conduction (jumping from node to node)
**Jumping is faster than running!!!**

-Myelin sheaths increase Rm and thus, increase the length constant, increasing CV.
**prevents leaks therefor length constant is larger, can reach greater distances b/c doesn't waste**

-Decreases Cm b/c myelin is thick therefore charge of one ion has little to no effect on other ions.
**Won't cause ion sticking**
Define 'presynaptic' nerve.
-neuron that sends info
Define 'postsynaptic' nerve.
-neuron or effector(neuron, muscle, endocrine, etc.) that recieves info
Define 'synapse'.
-specialized region of contact between presynapse and postsynapse

**important for transmission and integration**
What are the 2 types of synapses?
1) Electrical

2) Chemical
What are the processes involved in Electrical Synapses?
-involves the direct contact of cytoplasm between pre and post synaptic cells
-pores between cells formed by gap junctions made bup of connexons
-allows current from presynaptic cell to spread directly to postsynaptic cell
-therefor the transfer of current is very fast between cells
-can also transfer AP very quickly, therefore is very useful in fast responses (ie:crayfish tail flick)
-but it isn't very flexible (no modulation/integration... excitatory only
-relatively rare because you can't control it
What are the processes involved with chemical synapses?
-transmits info through a chemical messenger, the neurotransmitter
-released from presynaptic cell via voltage dependant enocytosis
-AP opens Ca++ channels
-Ca++ induces the fusion of neurotransmitter vesicles with the membrane where the neurotransmitters are then released
-Neurotransmitters can influence the postsynaptic cell in 2 ways
1)Ionotropic receptors: opens ion channels, postsynaptic cell depolarizes, has a direct effect
2)Metabotrophic receptors: Activates intracellular messengers, has an indirect effect
-synapses changes postsynaptic Vm
-can have Excitatory post synaptic potentials (EPSP's) or Inhibitory post synaptic potentials (IPSP's). Depends on the post synaptic receptors
-get AP's from EPSP's
What is integration?
-the temporal and spatial summation of PSP's

-get AP's from EPSP's NOT from IPSP's
What 3 points on the neuron can the stimulus be applied?
1)Axosomatic: on the body/soma

2)Axodendritic: on dendrite

3)Axoaxonic: on the axon, presynaptic modulation
What would you do to cause a Excitatory Post Synaptic Potential (ESPS)?
-stimulate an inward I(Na)
-block an outward I(K)
-block an inward I(Cl)
**transmitters- ACh, Glutamate**
What would you do to cause a Inhibitory Post Synaptic Potential (ISPS)?
-stimulate an outward I(K)
-stimlulate an inward I(Cl)
**Transmitters: gamma-aminobutyric acid (GABA), glycine
What are synaptic vesicles?
-neurotransmitters are synthesized in the soma or terminal and are packed into synaptic vesicles
-transported to axon terminals (the active zone for release)
-seminal vesicles are recycled to prevent expansion of membrane
What 2 ways are neurotransmitters released?
1)Classical Endocytosis of Synaptic Vesicle:
-slower, but has a higher rate of release because Synaptic Vesicle opens wider

2)Kiss and Run of Synaptic Vesical:
-faster, but has a lower rate of release because Synaptic Vesicle has a narrower opening
What are the 2 main stages to neurotransmitter release?

What 5 stages are invloved?
1)Mobilization: vesicle moves from storage area to active zone

2)Docking: vesicle irreversibly attaches to presynaptic membrane

Stages are:
1)Targeting: vesicle moves to the active zone and attaches reveribly

2)Docking: the interaction of v-SNARE and t-SNARE proteins docks the vexicle irreversibly

3)Ca++ Entry: Ca++ enters with depolarization and binds to synaptotagmin

4)Fusion: Ca++ boud synaptotagmin triggers membrane fusion and exocytosis

5)Endocytosis: vesicle gets recycled
Explain the physiochemical causes of the bends and how the disease can be prevented.
-compressed air boosts partial press so that lungs don't collapse at depths
-N2 gets boosted really high (0.8atm to 5atm-10atm)
-if the person surfaces too quickly, partial pressure of dissolved N2 in the blood and other tissues may be many atm's, exceeding the hydrostatic pressure.
-solubility of N2 is suddenly reduced, causing bubbles in blood and tissue causing pain

-prevent by going slow so that N2 can leave at slower rate, therefor won't case bubbles
-use He/O2 mixture because He is not too soluble and it's small so it diffuses out faster

***Remember: Boyles Law = Volume
Dalton's Law = Partial Pressure
Henry's Law = Vgas = (Vliquid)(alpha)(Pgas) for expansion***
What are the 2 types of physiologically produced antifreezes?
1)Colligative antifreezes: increase total concentration of solutes, therefore lower freezing point

2)Noncolligative antifreezes: molecules bind to ice crystals by H-bonds and supress it's growth by blocking out water molecules, thus stops freezing
How does bicarbonate(HCO3) help buffer the red blood cell?
-CO2 + H2O = H2CO3 = H + HCO3
-carbonic anhydrase combines CO2 and H2O
-HCO3 gets pumped out the cell while simultaneously bringing Cl in to balance charges
-remaining H is paired with hemoglobin which buffers and protects the cell from excess [H]

**Note: [CO2] is proportional to [H]
Hyperventilation = lo[CO2] = lo[H] = hi pH... respiratory alkalosis
Hypoventilation = hi[CO2] = hi[H] = hi pH... respiratory acidosis***
What is a Donnan Equilibrium?
-When a membrane is permeable to more than one sort of ion, an electrical gradient produced by diffusion of any one ion will affect the equilibrium involving diffusion of multiple ions (and water) then tends to develope

***There are permeable ions and nonpermeable ions involved... think about attraction and repulsion***
How does water, a polar molecule, get through the cell membrane?
-aquaporins... but not all cells have these so...
-they are small and have lots of KE
-it is by chance that they fit through the tails of the lipid bilayer.
-water just shoots for the gap and busts through
What is negative interstitial fluid pressure?
-lymphatic draws water out and creates -'ve pressure... Water fills the negative pressure area therefore water moves out.
What are the pressures in a kidney?
-the glomerulus lies within the Bowmans capsule. All pressures are for those found in the glomerulus:
-blood pressure: +6.7kPa
-COP: -3.5kPa
-Capsular fluid hydrostat pres: -1.9kPa
-net pressure favoring filtration: +1.3kPa
What is a refractory period?
-a period in which no stimulus can activate another AP
-due to sodium inactivation

-ensures unidirectional movemetn
What is spatial summation?
-the summation of post synaptic potentials that result from presynaptic AP's at different synapses onto the same post synaptic cell
What is temporal summation?
-the summation of synaptic potentials in response to repeated post synaptic potentials at the same synapsis
What is a chemical synapse?
-the most common type of synapse
-slower than elextrical but more flexible
-can be excitatory or inhibitory
-post synaptic cell often recieves many synapses
-can have summation/integration
-overall effect is to change Vm of postsynaptic cell
What are the 2 ways that neurotransmitters can influence the postsynaptic cell?
-Neurotransmitters can influence the postsynaptic cell in 2 ways
1)Ionotropic receptors: opens ion channels, postsynaptic cell depolarizes, has a direct effect
2)Metabotrophic receptors: Activates intracellular messengers, has an indirect effect

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