su14_-_physiology_exam_1_20141210195301 Flashcards
What are often referred to as “excitable cells”? Why?
neurons (single nerve cells) and most muscle cells because their physiologic functions rely critically on electrical events in their plasma (surface) membrane
What are the 3 mechanisms of electrical events?
- mechanism of cell-to-cell (intercellular) communication2. mechanism for sensing environmental changes (light, sound, temperature, etc.)3. mechanism for triggering intracellular events
An electrical event that acts in cell-to-cell communication ____ (is/is not) very rapid, allows for ____, and allows for ____.
- is very rapid- allows precise timing of signals between cells- allows complex patterns of communication between cells
What is an example of an electrical event that acts to sense environmental changes?
stimuli from the environment affect receptors (ex. rods and cones of the retina) and cause electrical events to occur in the receptor cells
Electrical events in cells can trigger intracellular changes which ____ (are/are not) rapid or can ____.
- are rapid- accumulate over time
What is an example of an electrical event that triggers intracellular events that is rapid?
rapid changes in [Ca +2] in hear and skeletal muscle cells
What is an example of an electrical event that triggers intracellular changes that can accumulate over time?
changes in hippocampal cells involved in learning (memory formation)
What is the definition of excitation?
activation to initiate an event
What are the 3 compartments that are important for excitation in cells?
- extracellular fluid (interstitial fluid)2. intracellular fluid (cytosol)3. cell membrane
What is found in the extracellular fluid (interstitial fluid)? What is it similar to in respect to the ionic composition? What is in high concentration?
- primarily ions, proteins, and other molecules- similar to plasma with respect to ionic composition- high NaCl concentration
What is found in the intracellular fluid (cytosol)? What is in high concentration?
- ions, much higher concentration of proteins, and other molecules- predominant salt in cells is KCl
Describe the composition of the cell membrane.
phospholipid bilayer and proteins; about equal amounts of protein and lipid and a small (approx 5%) amount of carbohydrates (for cell recognition)
What is the definition of permeability?
an index of the ability of the ion to cross the membrane
Changes in permeability that are ____ and ____ are essential to excitation in cells.
- ion-specific- exquisitely timed
What are the 5 types of movements across membranes?
- simple diffusion2. mediated transport3. osmosis4. endocytosis5. exocytosis
What is the definition of simple diffusion?
random diffusion, diffusion down an electrical gradient or a concentration gradient (organic molecules or ions)
____ (polar/non-polar) organic molecuels diffuse rapidly through the membrane which is 50% lipid because their solubility in lipid is ____ (high/low). Energy ____ (is/is not) required.
- non-polar- high- is not
In simple diffusion, ions cross membranes through ____ which are proteins, often composed of several subunits and generally ion-specific (ex. K or Na channels).
channels
What are some examples (4) of non-polar substances?
oxygen, carbon dioxide, fatty acids, steroid hormones
What is the definition of flux?
amount of substance crossing a surface per unit of time
The diffusion of a substance between two compartments is always ____ (bidirectional/unidirectional).
bidirectional
What is the definition of net flux? When the net flux = 0, what is the system called?
- difference between the two unidirectional fluxes- in a state of “diffusion equilibrium”
What is the definition of mediated transport?
ligand binds to a transporter in the membrane, the transporter undergoes a conformational change, and the ligand is released on the other side of the membrane
What are the 2 types of mediated transport?
- facilitated diffusion2. active transport