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79 Cards in this Set

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WHAT IS ANOTHER NAME FOR A TIGHT JUNCTION?
ZONULA OCCLUDENS
Proteins that span the entire cell membrane
Integral proteins
Membrane proteins that include Ion channels and Transport proteins
Integral proteins
Membrane proteins that are located on either the intracellular or extracellular side of the cell
Peripheral proteins
Membrane proteins that include Hormone receptors
Peripheral proteins
Zonula occludens alternate name
Tight junction
Attachments between cells that may be an intercellular pathway for solutes, depending on size, charge, and characteristics of the particular things I'm asking about
Tight jxn (Zonula occludens)
What are integral membrane proteins?
Anchored to and embedded in the cell membrane via hydrophobic interactions. They may span the cell membrane
Are attachments between cells that permit intercellular communication
-Example: permit current flow and electrical coupling between Myocardial cells
Gap junctions
Q: What is the definition of osmolarity?
A: The number of osmotically active particles in a solution.
What are peripheral membrane proteins?
Loosely attached to the cell membrane via electrostatic interactions
WHAT IS SERCA?
SARCOPLASMIC RETICULUM AND ER [CA2+] ATP-ASE PUMP

([CA2+] UPHILL)
What is the reflection coefficient (sigma)?
a number between zero and one that describes the ease with which a solute permeates a membrane
1: solute is impermeable
0: solute is completely permeable
Q: What is the definition of the reflection coefficient?
A: A number between zero and one that describes the easy with which a solute permeates a membrane. σ = 1 = impermeable. σ = 0 = solute is completely permeable.
define permeability
the probability of a channel being open
What is simple diffusion?
Only form of transport that is not carrier-mediated
Occurs down an electrochemical gradient
Does not require energy
COLLOIDOSMOTIC PRESSURE / ONCOTIC PRESSURE
PRESSURE DUE TO PRESENCE OF PROTEINS (EG PLASMA PROTEINS)
The flow of water across a semipermeable membrane from a solution with low solute concentration to a solution with high solute concentration
Osmosis
What is "permeability?"
It describes the ease with which a solute diffuses through a membrane. It depends upon the characteristics of the solute and the membrane
REFLECTION COEFFICIENT
EASE WITH WHICH A SOLUTE PERMEATES A MEMBRANE

(1 = IMPERMEABLE, 0 = COMPLETELY PERMEABLE)
Q: What is accommodation in nerve action potentials?
A: Occurs when cell membrane is held at a depolarized level for extended periods, such that the threshold is passed without firing an action potential. Closes the inactivation gates of the Na+ channel. Demonstrated in hyperkalemia.
Define resting membrane potential
the intracellular potentail relative to the extracellular potential.

e.g. -70mV = 70mV, cell negativeg
Define inward current
postive charge flowing into the cell
What is accommodation?
cell membrane is held at depolarized level even with the threshold potential is passed.
e.g. hyperkalemia: skeletal muscle membranes are depolarized by high serum K+
What are proteoglycans?
Proteoglycans are a major component of the animal extracellular matrix, the 'filler' substance existing between cells in an organism. Here they form large complexes, both to other proteoglycans, to hyaluronan and to fibrous matrix proteins (such as collagen). They are also involved in binding cations (such as sodium, potassium and calcium) and water, and also regulating the movement of molecules through the matrix.
What is Lambert-Eaton myasthenic syndrome?
patients have antibodies against Ca channels in motor nerve terminals --> less Ca enters nerve termianl and patients have musclar weakness and diminished stretch reflexes
ACCOMMODATION
CELL MEMBRANE HELD IN DEPOLARIZED STATE ABOVE THRESHOLD, BUT DOES NOT FIRE OFF AN AP -> B/C [NA+] INACTIVATION GATE CLOSED BY DEPOLARIZATION
What is myasthenia gravis
antibodies to the ACh receptor
- skeletal muscle weakness and fatigue
- decreases the size of the EPP
- can be treated by AChE inhibitors
Define threshold
inward Na current exceeds outward K current
WHAT IS MYASTHENIA GRAVIS? TX?
AUTOIMMUNE AGAINST ACH RECEPTOR -> FEWER RECEPTORS -> SMALLER EPP + MORE DIFFICULT TO GENERATE AP -> SKELETAL MUSCLE WEAKNESS + FATIGUE

(TX W/ ACHESTERASE INHIBITORS -> PROLONGS ACH EFFECT AT MUSCLE END PLATE + SLOWS DOWN DEGRADATION)
What is osmolarity?
The concentration of osmotically active particles in a solution
What is osmosis?
The flow of water across a semipermeable membrane from low solute concentration to high solute concentration.
What is osmotic pressure?
The extent to which a compartment attracts water into it by having a high solute concentration. Note that this osmolarity is for osmotically active particles only.
WHAT IS PHEOCHROMOCYTOMA?
ADRENAL MEDULLA TUMOR -> SECRETES CATECHOLAMINES + INCREASED VMA IN URINE
What is colloid osmotic pressure?
Also known as oncotic pressure
It is the osmotic pressure generated by proteins
What is the reflection coefficient?
A number between 0 and 1 that describes the ease with which a solute permeates a membrane
WHAT IS PARKINSON'S DISEASE?
DEGENERATION OF DOPAMINERGIC NEURONS USING D2 RECEPTORS
What is a diffusion potential?
The potential difference generated across a membrane because of a concentration difference of an ion. This type of potential can only be generated if the membrane is permeable to the ion
T TUBULE
1) CARRY DEPOLARIZATION FROM SARCOLEMMAL MEMBRANE TO CELL INTERIOR
2) FOUND AT A-I BAND JUNCTION
DIHYDROPYRIDINE RECEPTOR
VOLTAGE-SENSITIVE PROTEIN IN T TUBULES THAT CHANGES CONFORMATION WHEN DEPOLARIZED -> OPENS RYANODINE RECEPTORS IN SARCOPLASMIC RETICULUM
What is an equilibrium potential?
The diffusion potential that exactly balances (opposes) the tendency for diffusion caused by a concentration difference
What is electrochemical equilibrium?
The chemical and electrical driving forces acting upon an ion are equal and opposite, so there is no net diffusion of the ion
What is troponin?
the regulatory protein that allows cross-bridge fomration when it binds to Ca2+
What is the Nernst equation used for?
Calculation of the equilibrium potential at a given concentration difference for a permeable ion across a cell membrane. It tells us what potential would balance the tendency for diffusion, or the potential at which the ion would be at electrochemical equilibrium
Define isometric contraction
length is held constant. No muscle shortening
ISOMETRIC CONTRACTIONS
MUSCLE LENGTH FIXED (AKA PRELOAD) -> CONTRACTION STIMULATED -> TENSION MEASURED

(NO SHORTENING)
What is the resting membrane potential?
The overall membrane potential that is established by diffusion potentials resulting from concentration gradients of all permeant ions. By convention, it is expressed as the intracellular potential relative to the outside, so -70 mV means 70 mV, cell negative
Isotonic contraction
Load is held constant. Shortening of muscle
ISOTONIC CONTRACTIONS
LOAD FIXED (AKA AFTERLOAD) -> CONTRACTION STIMULATED -> SHORTENING MEASURED
FORCE-VELOCITY RELATIONSHIP
MEASURES VELOCITY OF SHORTENING DURING ISOTONIC CONTRACTIONS AGAINST DIFFERENT LOADS -> VELOCITY OF SHORTENING DECREASES AS AFTERLOAD INCREASES
What is depolarization?
When the membrane becomes less negative (the cell interior becomes less negative)
What is hyperpolarization?
When the membrane becomes more negative (the cell interior becomes more negative)
What is inward current?
The flow of positive charge INTO the cell, depolarizing the membrane potential
What is outward current?
The flow of positive charge OUT of the cell, hyperpolarizing the membrane potential
What is an action potential?
A property of excitable cells that consists of a rapid depolarization (upstroke) followed by repolarization of the membrane. Action potentials are propagating
What is an action potential threshold?
The membrane potential at which the action potential is inevitable, and the net inward current becomes greater than the net outward current
What is the "overshoot" of an action potential?
The brief portion at the peak of the action potential where the membrane potential becomes positive
What is the absolute refractory period?
The period during which another action potential cannot be elicited, no matter how large the stimulus. This is because the inactivation gates on the Na channels are still closed
What is the relative refractory period?
The period during which an action potential can be elicited, but only if it is larger than the usual inward current. This is because the K conductance is higher than at rest, so as Em approaches Ek, it moves farther away from threshold
What is accommodation (in the context of action potential propagation)?
Occurs when a cell membrane is held at a depolarized level such that threshold is passed without firing an action potential
Occurs because depolarization closes the inactivation gates on the Na channels
Accommodation is demonstrated in hyperkalemia, where skeletal muscle is depolarized by high serum K concentrations. This closes the Na channels
What is the neuromuscular junction?
The synapse between the axons of motor neurons and skeletal muscle. The neurotransmitter, ACh, binds to postsynaptic nicotinic receptors
What is the end plate potential in the postsynaptic membrane?
The contents of one synaptic vesicle (1 quantum) produce a miniature end plate potential (MEPP), the smallest possible depolarization
MEPPs summate to produce a full-fledged EPP, which is NOT an action but simply a depolarization (not to threshold) of the muscle end plate
What is a one-to-one synapse?
A action in the presynaptic element (the motor nerve) produces an action in the postsynaptic element (the muscle)
This type of synapse is found at the neuromuscular junction
What is a many-to-one synapse?
An action in a single presynaptic cell cannot produce an action potential in the postsynaptic cell by itself
Many cells synapse on the postsynaptic cell to depolarize it to threshold
Presynaptic input may be excitatory or inhibitory
What is an excitatory postsynaptic potential (EPSP)?
These are inputs that depolarize the postsynaptic cell and bring it closer to threshold
They are caused by the opening of channels that are permeable to Na and K, similar to ACh channels
They depolarize to a value about halfway between Ena and Ek
What is an inhibitory postsynaptic potential (IPSP)?
These are inputs that hyperpolarize the postsynaptic cell, moving it away from threshold
They are caused by the opening of Cl channels, so the Em approaches Ecl
What is spatial summation of synapses?
Two excitatory inputs arrive at a postsynaptic neuron at the same time, and together they produce greater depolarization
What is temporal summation of synapses?
Two excitatory inputs arrive at a postsynaptic neuron in rapid succession
Because the resulting depolarizations overlap in time, they are added in a stepwise fashion
What is facilitation (in the context of the synapse)?
Also known as augmentation and post-tetanic potentiation
This occurs after tetanic stimulation of the presynaptic neuron
Depolarization of the postsynaptic neuron is greater than expected, because greater-than-normal amounts of neurotransmitter are released due to accumulation of Ca in the presynaptic terminal
Long-term potentiation (memory) involves new protein synthesis
What defines a sarcomere?
You count Z line to Z line
What are T tubules?
They are an extensive tubular network open to the extracellular space that carry depolarization from the sarcolemma to the cell interior. They are found at the junction of A and I bands, and contain a voltage-sensitive dehydropyridine receptor that undergoes a conformational change upon depolarization
What is the sarcoplasmic reticulum?
Internal tubular structure that stores and releases Ca for excitation-contraction coupling
Terminal cisternae make contact with the T tubules in a triad
Membrane has a Ca-ATPase that transports Ca into the SR
Contains Ca loosely bound to calsequestrine
Releases Ca into the cell interior through the ryanodine receptor
What are isometric muscle contractions?
Contractions at a fixed length. The length (preload) is fixed, the muscle is stimulated to contract, and the developed tension is measured. There is no muscle shortening.
What are isotonic muscle contractions?
The load against which the muscle contracts (afterload) is fixed, the muscle is stimulated to contract, and shortening of the muscle is measured.
What is the length-tension relationship of muscle?
Measures tension during isometric contractions when the muscle is set to fixed lengths (preloads)
What is passive muscle tension?
The tension developed by stretching the muscle to different lengths
What is total muscle tension?
The tension developed when the muscle is stimulated to contract at different lengths
What is active muscle tension?
The difference between total and passive tension, representing the active force developed from muscle contraction
Active tension is proportional to the number of cross-bridges formed
What is the force-velocity relationship of muscle?
Measures the velocity of shortening of isotonic contractions when the muscle is challenged with different afterloads
The velocity of shortening decreases as the afterload increases