Intro to Physiology Review Flashcards by Carolyn Ziebol

What is physiology?

study of the function of body parts
- how all the body parts work and carry out their life-sustinaining activities

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Biological membranes are made up of…

a. lipids (phospholipids, cholesterol, and glycolipids)
b. proteins

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Cell Membrane Structure

lipids of cell membrane form a phospholipid bilayer with the hydrophobic (water insoluble) ends of each lipid molecule face the interior of the membrane and the hydrophilic (water soluble) ends face outwards

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Integral membrane Proteins

they are embedded in the phospholipid bilayer of cell membrane and cannot be removed without disrupting it. They include channels, pumps, carriers and receptors

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Peripheral Proteins

they bind to the hydrophilic polar heads of the lipids or the integral proteins

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Passive Transport

ions being able to fuse across the membrane without any energy expenditure of the cell (ATP use)
1. Diffusion (simple or facilitated)
2. Osmosis

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Active Transport

ions have to be transported with the help of channels that require ATP expenditure to work
1. Primary Active Transport
2. Secondary Active Transport

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Vesicular Traffic & Plasma Membrane

travel of things in and out of the cell through membrane bound things
1. endocytosis
2. exocytosis

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Simple Diffusion

net movement of molecules (or ions) from a region of their high concentration to a region of their lower concentration
- occurs through the cell membrane by two pathways:
a. interstices of the lipid bilayer
b. through protein channels
- no interactions with carrier proteins
ex: O2, CO2

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“Gating of Channels”

protein channels can be gated and these are regulated by:
a. electrical signals (voltage-gated)
b. chemicals (ligand-gated)

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Factors Affecting Rate of Simple Diffusion

concentration gradient across membrane
surface area of membrane
solubility in the membrane or permeability (the more soluble the substance, the faster it will diffuse)
thickness of membrane (thicker membrane = slower rate of diffusion)
molecular weight of ion (not directly clinically important)

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Facilitated/Carrier Diffusion

movement of substances in combination with carrier protein without utilization of energy
- diffusion approches a maximum which is dependent on the saturation of the carrier proteins
- ex: transport of glucose and most amino acids

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Osmosis

diffusion of water across a semipermeable membrane or selectively permeable membrane
- water will diffuse from a region of higher water concentration to a. region of lower water concentration

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Isotonic Medium

no movement of fluid from ICF or ECF

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Hypertonic Solution

higher concentration of things outside cell and lower concentration of water so water moves out of cell into solution to balance it and therefore shrinking the cell

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Hypotonic Solution

lower concentration of things outside the cell than inside and higher concentration of water outside so fluid moves from ECF to ICF, expanding the cell and in some instances, bursting it

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Active Transport

net movement against a concentration gradient and requires energy to do so (ATP)

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Primary Active Transport

ATP is consumed directly by the transporting protein
- ex: Na/K-ATPase pump, calcium pump

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Secondary Active Transport

depends directly on ATP as a source of energy
- in co-transport, molecules move in the same direction
- for ex, movement of Na+ and glucose in renal tubules and gut
- in counter transport, molecules move in opposite direction for example, Na+ and Ca2+ in heart and muscle

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Characteristics of All Protein-Mediated Transport

a. Rate of Transport: transport faster than it would be by diffusion
b. Saturation Kinetics: transport rate increases directly with the rise of concentration, but once the transporters become saturated, transport rate is maximal
c. Chemical Specificity: substance must have a certain chemical structure that matches with the transporter
d. Competition for Carrier: substance of similar chemical structure may compete for the same transporter

Endocytosis

the movement of macromolecules from outside the cell to inside the cell by active invagination of plasma membrane

Phagocytosis

process by which solid bits of material are engulfed by cells (type of endocytosis)

Pinocytosis

uptake of molecules in the solution

Exocytosis

process by which macromolecules are packed in secretory vesicles and extruded from the cell
- requires both calcium and energy

Constitutive Secretion

vesicles are not coated with clathrin and are continuously fusing with the cell membrane and being released ex: release of proteins such as albumin

Regulated Exocytosis

vesicles are coated with clathrin, and a signal is required before the vesicle will fuse with the membrane

Intracellular Fluid (ICF)

fluid inside cells - takes up approx 2/3 of total body water

Extracellular Fluid (ECF)

fluid outside/around cells - takes up approx 1/3 of total body water

Interstitial Fluid (ISF)

outside cell and in between cells specifically - approx 2/3 of ECF

Vascular Fluid (VF)

type of ECF and is a mix of plasma + RBC, flows through veins, capillaries, etc. - approx 1/3 of ECF

ICF Components

- K+ - Mg - PO4 - Protein

ECF Components

- Na+ - Ca2+ - Cl2- - HCO3- - O2, CO2, glucose, fatty acids, amino acids

What happens in the case of loss of isotonic fluid?

the volume of the ECF and VF is reduced but the osmolarity does NOT change as isotonic fluid was lost and so osmolarity is NOT affected - since ECF osmolarity is unchanged, there is no change to ICF volume

What happens in the case of a loss of Hypotonic fluid (sweating, hypotonic urine)?

Loss of hypotonic fluid from ECF makes ECF hypertonic so ICF fluid will move to ECF to balance it out, shrinking the cells

What happens if you ingest salt tablets?

Salt tablets make ECF hypertonic so fluid goes from ICF to ECF

Isotonic Fluid gain will cause:

Increase in ECF volume but no change in osmolarity and no effect on ICF osmolarity or volume

Hypotonic fluid gain will cause:

Increase in ICF osmolarity as ECF becomes hypotonic, so then fluid flows into the ICF, increasing the osmolarity

Action Potential

a short lasting, reversible change in electrical potential occurring on the surface of an excitable cell, especially of a nerve or a muscle cell, that occurs when it is stimulated, resulting in the transmission of an electrical impulse

Resting Membrane Potential

-90 mv (in some cells) but USUALLY (-70mv)

Depolarization

+30mv

Threshold Potential

USUALLY -55mv

Voltage Changes During Action Potential

1st step: Depolarization: voltage gated Na channels open and there is influx of Na ions causing the resting membrane (-70mv usually) potential to become more positive 2nd step: Repolarization: voltage gated K channels open and there is efflux of K ions causing the membrane potential to return back to its resting state - all through cell there are Na+K+ pumps which keep pumping in K and Na out of the cell at a ratio of 2:3

Ungated Potassium Channels

these channels are always open, and unless the membrane potential reaches the potassium equilibrium potential - a potassium equilibrium is maintained through these Channels

Voltage-Gated Sodium Channel

these channels are closed under resting conditions. membrane stimulus/signal causes these channels to quickly open and close and cause the depolarization phase. once they close, they will not respond to a second stimulus until the cell almost completely repolarizes

Voltage-Gated Potassium Channels

these channels are closed under resting conditions. they require a stimulis/signal to open and are responsible for...slide cuts off

Absolute Refractory Period

the period during which no matter how strong the stimulus, it cannot induce a second action potential - this period is due to voltage inactivation of sodium channels

Relative Refractory Period

that period during which a greater than normal stimulus is required to induce a second action potential

Cell Diameter

the greater the cell diameter, the greater the conduction velocity