Lecture 1-3

Total Body water is what?

How much water is in the body

What percent is total body water of an animals body weight?

50-70%

What are the two components that make up total body water and what are their percentages?

Intracelular fluid- \~40%

Extracellular fluid- \~20%

What are the two components of extracellular fluid and their percentages?

Interstitial fluid\~16%

Plasma \~4%

What is the average blood volume?

70mL/kg of body weight

When measuring total body water, how many Liters equal a kg?

It’s a 1:1 ratio, 1kg=1L

What are the measurable AMOUNTS of solutes in fluid compartments?

Moles, equivalents, or osmoles

What is “equivalent” when measuring solutes in fluid compartments?

Amount of charged solute. Ex. CaCl2= 2nd Ca and 2 eq Cl

What is “osmole” when measuring solutes in fluid compartments?

Number of particles into which a solute dissociates in solution (NaCl= 2 osmoles in solution)

What unit do you measure CONCENTRATIONS in?

Mol/L or mmol/L, mEq/L, Osm/L or mOsm/L

What is osmolarity?

Osmolarity=osmoles/L

What is electroneutrality?

Each body fluid compartment must have the same concentration of cations and anions. Total charge has to be the same.

What are the major ions in extracellular fluid (ECF)?

Major cation= Na+

Major anions= Cl- and HCO3-

What are the major ions in intracelular fluid (ICF)?

Major cation = K+

Major anions = proteins & organic phosphates (These always have a negative charge)!!

What is total calcium?

Ionized calcium + being bound to a mineral or protein

What is ionized calcium?

Free calcium + active form

What is the osmolarity in ECF and ICF?

290-300 mOsm/L

How much Na+ is in ECF?

140 mEq/L

How much K+ s in ICF?

120 mEq/L

What is the plasma volume of a 6kg cat?

240mL or 24L

What pumps directly use ATP?

Na+/K+ ATPase pump

Ca2+/ATPase pump

What does the Na+/K+ ATPase pump do?

Ubiquinous in all cells, pumps Na out, pumps K into ICF creating charge separation and potential difference

What does the Ca2+/ATPase pump do?

Pumps Ca out of cells

Why are ion concentration differences important?

\-Allows nerve and muscle cells to have resting membrane potentials (due to K+ difference)

\-Upstroke of action potentials in nerve and muscle cells, and absorption of nutrients due to Na+ difference

\-Excitation-contraction coupling in muscle cells depends on Ca2+ difference

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What are the transporters for glucose? If they utilize the Na+ gradient, do they use energy directly?

amino acids, Ca2+, H+

No they don’t

What lipids compose the cell membrane?

Glycolipids, phospholipids, cholesterol

What are some lipid-soluble substances?

O2, fatty acids, steroid hormones

What do lipid soluble substances have low permeability to? Give examples.

Water soluble substances: glucose, ions, amino acids

What proteins help compose the cell membrane? Where are they located?

Transporters, enzymes, hormone receptors, antigens, ion+ water channels (train every hour at insane weights)

They spam the entire membrane

What does the phospholipid do for the cell membrane?

Create bi-layer

Simple diffusion:

Active or passive

Carrier-mediated?

Uses metabolic energy?

Dependent on Na+ gradient?

Passive;downhill

No

No

No

Facilitated diffusion:

Active or passive

Carrier-mediated?

Uses metabolic energy?

Dependent on Na+ gradient?

Passive;downhill

Yes

No

No

Primary Active Transport:

Active or passive

Carrier-mediated?

Uses metabolic energy?

Dependent on Na+ gradient?

Active;uphill

Yes

Yes;direct energy

No

Cotransport:

Active or passive

Carrier-mediated?

Uses metabolic energy?

Dependent on Na+ gradient?

Secondary active

Yes

Yes;indirect

Yes (solutes move in same direction as Na+ across cell membrane)

Countertransport:

Active or passive

Carrier-mediated?

Uses metabolic energy?

Dependent on Na+ gradient?

Secondary active

Yes

Yes;indirect

Yes (solutes more in opposite direction as Na+ across cell membrane)

What can occur down a gradient of high concentration to low concentration such as electrochemical gradients?

Simple or facilitated diffusion BUT you need carrier proteins to grab and move them

What con occur against an electrochemical gradient (low to high concentration)

Primary transport (direct energy)

Secondary transport (indirect energy)

Movement of solute depends on several factors. Name and explain them.

Concentration gradient – driving force

Partition coefficient – based on lipid solubility of solute

Diffusion coefficient – based on size of solute and viscosity of solution. Small solutes in a high viscous solution have the highest DC.

Thickness of membrane- the thicker the membrane, the lower the diffusion

Surface area – greater surface area = higher diffusion rate

What are the 3 out of 5 factors of solute movement are related to permeability?

Concentration gradient, partition coefficient, diffusion coefficient

What are the two additional consequences of charge on an ion that is diffusing?

1. A potential difference across a membrane will alter the rate of diffusion of a charged solute ( Diffusion of a positively-charged ion will slow down if diffusing into an area of positive charge)
2. A diffusion potential can be created when a charged solute diffuses down its concentration gradient

What happens in facilitated diffusion due to the limited number of carriers?

It will proceed faster at a relatively low, solute concentration

What are some examples of facilitated diffusion?

GLUT4 transporter in skeletal and adipose tissue

\-Transports glucose into cells

\-D-galactose also competes for binding

WHat are the three features of carrier-mediated transport?

Saturation, stereospecificity, competition

What does saturation do in carrier-mediate transport?

Carrier proteins have limited number of binding sites for solute. Therefore, the rate of transport increases at a higher rate at lower solute concentrations.

Stereospecificity

Binding sites for solute on carrier proteins are specific

Transporter for D-glucose, wont transport L-glucose

Competition in carrier mediated transport?

binding sites are specific, carriers may recognize and bind chemically-related solutes. Ex. D-glucose transporters may transport D-galactose .

Ca2+ ATPase pump

1 Ca out for every ATP used

2 Ca from ICF into endoplasmic reticulum for every ATP used

H+/K+ ATPase pump

Parietal cells of gastric mucosa - pumps H+ into lumen of stomach

Secondary active transport

Indirectly uses energy by utilizing the Na+ gradient to transport solutes against their concentration gradient

Uses counter transport or cotransport

Co-transport (symport)

All solutes transported in same Intestine & Renal tubule direction

Intestines & renal tubule: Na+/glucose co-transporter (SGLT 1), Na+/amino acid co-transporter, Na+/K+/2Cl- co-transporter in renal tubule

Counter-transport (antiport)

Solutes move in opposite directions – Na+ moves into cell and other solute moves out of cell

Can be either Ca2+/Na+ exchange OR Na+/H+ exchange

What is osmosis?

Flow of water across a semi-permeable membrane __due to differences in solute concentration__

Osmosis is NOT simply diffusion of water; it occurs because?

Pressure difference

If a container is equally divided but one side has more solute, which side will have osmotic pressure?

The side with more solute

Osmotic pressure is what?

Pulling pressure, caused by difference in solute concentration. The side with more solute will pull.

Hydrostatic pressure is what?

Pushing pressure or fluid pressure. It’s pressure exerted by stationary fluid. Ex. Moving of fluid against a membrane that deforms easily like plasma membrane usually does not have a lot of hydrostatic pressure

Why are osmotic and hydrostatic pressure important in cells and blood vessels?

They allow fluid exchange across capillaries

What is interstitial hydrostatic pressure?

Fluid pressure exerted between cells

What happens when blood hydrostatic pressure is exerted by fluid within the blood vessels?

BP will rise and blood vessels will favor fluid moving out

What is osmotic pressure (colloidal osmotic, or oncotic)?

Osmolarity determines how much fluid is pulled into a space such as blood vessels, high osmolarity=a lot of fluid pulled into blood vessels= BP increase

When a lot of fluid leaves the blood vessels due to low osmolarity, what can happen?

Tissue edema

Overall, the different pressures favor what?

Filtration out of capillaries and into tissues

Osmolarity concentrations express the osmotic strength of what?

Things like urine, plasma, and NaCl

what is the difference in osmolarity and osmolality?

Osmolarity and osmolality both measure the concentration of solute particles in a solution, but they differ in the units of measurement. Osmolarity is expressed in osmoles per liter (osmol/L), while osmolality is expressed in osmoles per kilogram (osmol/kg). Osmolarity takes into account the volume of the solvent (usually water), while osmolality takes into account the mass of the solvent.

What are the three osmotic balances?

Isosmotic, hyperosmotic, hypo-osmotic

Isosmotic

Properties have equal osmotic pressure

What happens to a normal cell placed in an isosmotic solution?

Nothing, the pressure is the same everywhere

Hyperosmotic

the osmotic pressure of the desired solution is higher than the surrounding

What happens to a normal cell placed in a hyperosmotic solution?

Fluid will move out of the cell and into the solution causing the cell to shrivel

Hypo-osmotic

Pressure of the desired solution is lower than the surrounding

What happens to a normal cell placed in a hypo-osmotic solution?

Fluid would move into the cell, cell will lyse (explode)

If a cell is placed into a 330mOsm/L, how is the solution described?

Hypertonic

What is tonicity?

Defined by the response of cells or tissues immersed in the solution

Isotonic

cells/tissues neither swell nor shrink when immersed in solution

Hypotonic

cells/tissues swell when immersed in solution

Hypertonic

cells/tissues shrink when immersed in solution

What is oncotic pressure?

Form of osmotic pressure specifically exerted by proteins, mostly albumin, within blood vessels

Decrease in blood oncotic pressure equals?

Edema

What is RMP?

Resting membrane potential, potential difference that exists across membranes in the period between action potentials

How is RMP established?

Diffusion potentials, defined as potential difference generated across a membrane when a charged ion diffuses down the concentration gradient

Can a diffusion potential be positive or negative?

Either depending on the charge of the ion moving down the gradient

What are diffusion potentials set by?

K leak channels maintained by the Na+/K+ ATPase pump

What is the RMP range?

\-70 to -80 mV

How does the Na+/K+ ATPase pump help RMP?

It maintains the K concentration gradient and __helps set the K diffusion potential__

What is equilibrium potential?

Diffusion potential that opposes the tendency for further diffusion of an ion down a concentration gradient

What is driving force?

difference between the measured membrane potential and the ion’s calculated equilibrium potential

Where do action potentials (AP) occur?

In all excitable cells. It’s rapid depolarization followed by repolarization

Depolarization

Membrane potential becomes less negative or even positive

Hyperpolarization

Membrane potential becomes more negative

Inward current

Depolarization occurs. Flow of positive charge into cell. Na+K rushes into cell to depolarize

Outward current

Repolarize, flow of positive charge out of cell

Threshold potential

membrane potential at which an AP is inevitable

Overshoot

portion of AP where membrane potential is positive

Undershoot

portion of AP where membrane potential is more negative than RMP

Refractory period

period during which another AP can’t be generated

Which ion is primarily responsible for resting membrane potential?

K+

When are excitable cells unable to produce normal action potentials?

During refractory periods

What is absolute refractory period (ARP)?

No stimulus can occur to cause another action potential, inactivation gate remains closed until the cell is repolarized

Relative Refractory Period (RRP)?

From end of ARP until through most of hyperpolarization, AP occurs with greater than normal depolarization

Refractory periods

A – at RMP

B – activated by signal • Voltage gated • Ligand gated

C – inactivated state • Time and return to RMP required to reset • Refractory to subsequent stimulus