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79 Cards in this Set

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  • Back
Diffusion Equation
J = -PA (C1-C2)
Inhibitors of Na/K/ATPase
inhibits the H/K/ATPase pump
Example of secondary active transport, cotransport
Na-glucose cotransporter
- found in the luminal membrane of intestinal mucosa
- found in the renal proximal tubule
Example of secondary active transport, coutertransport/exhchange
Na-Ca countertransport
Equation for osmolarity
Osmolarity = g x C
- g = number of particles in solution (osm/mol)
- C = concentrastion (mol/L)
- Osmolarity (osm/L)
Van't Hoff's Law
pi = g x C x RT

- R = 0.082L atm/mol K
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
What is the effective osmotic pressure?
osmotic pressure x reflection coefficient
define permeability
the probability of a channel being open
Nernst Equation
E = -2.3RT/zF log[C_i]/[C_e]

C_i = intracellular concentration
C_e = extracellular concentration
What is the valude of 2.3RT/zF at 37 degrees Celcius (assuming z= 1)
E for Na
65mV (inside of cell positive at equilibrium)
E for Ca
120 mV (inside of cell is positive at equilibrium)
E for K
-85mV (inside of cell is negative at equilibrium)
E for Cl
-85 mV (insde of cell is negative at equilibrium)
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 can block voltage-sensitive Na channels and prevent action potentials?
What current causes depolarization?
inward Na current
What current causes repolarization?
outward K current
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 catalyzes the formation of ACh from acetyl coenzymeA (CoA) and choline?
Choline acetyltransferase
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
Where does ACh bind on the nicotinic receptor? What happens after it binds?
Binds to the alpha- subunit --> conformational changge --> central core increases channel conductance to K and Na.
What does Botulinus Toxin do?
Bockes release of ACh from presynaptic terminals
What does Curare do?
Competes with ACh for receptors on motor end plate.
Is a type of alpha toxin, since it binds to the alpha subunit on the nicotinic receptor
What does Neostigmine do?
Inhibits acetylcholinesterase
What does Hemicholinium do?
Blocks reuptake of choline into presynaptic terminal
What is a miniature end plate potential (MEPP)?
the smallest possible EPP, resulting fromt he contents from one synaptic vesicle
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
List the excitatory neurotransmitters
Ach, norepi, epi, dopamine, glutamate, serotonin
List the inhibitory neurotransmitters
GABA, glycine
Where does NorEpi bind?
the alpha and beta receptors on the postsynaptic membrane
how is Norepi removed from the synapse?
-metabolized by monoamine oxidase (MAO) and catechol-O-methyltrasferase (COMT)
What are the metabolites from Norepi metabolism?
What happens during pheochromocytoma?
it is a tumor of the adrenal medulla --> secretion of catecholamines --> increased urinary secretion of VMA (vanillylmandelic acid)
Where is Dopamine primarily found?
Where is Dopamine secreted?
hypothalamus. Inhibits prolactin secretion.
in this context, it is called prolactin-inhibiting factor (PIF)
How is dopamine metabolized?
by MAO
and COMT
What do D1 receptors activate?
adenylate cyclase via Gs protein
What do D2 receptors do?
inhibit adenylate cyclase via Gi protein
What happens in parkinsons?
degeneration of dopaminergic neurons that use the D2 receptor --> increase activation of adenylate cyclase via Gi protein
What happens in schizophrenia?
increased levels of D2 receptors --> increased inhibition of adenylate cyclase via Gi protein
Where is seratonin found?
How is seratonin formed?
from tryptophan
What is serotonin converted to, and where?
to melatonin by the pineal gland
What is histamine formed from?
Where is histamine found?
What are the four subtypes of glutamate receptors?
3 are inootropic receptors (ligand gated ion channels; e.g. NMDA)
1 is a metabotropic receptor (coupled to ion channels)
How is GABA synthesized?
from glutamate by glutamate decarboxylase
Note: GABA is inhibitory while glutamate is excitatory
What are the two GABA receptors?
GABA_A: increases Cl conductance
(site of action for benzodiasepines and barbiturates)
GABA_B: increases K+ conductance
Where is glycine found?
spinal cord and brain stem
What does glycine do?
increases Cl conductance
Where is NO found?
inhibitory neurotransmitter fond in GI tract, blood vessels, and CNS
How is NO synthesized?
Synthesized in presynaptic nerve terminals
NO synthase converts arginine to citrulline and NO
Notes on NO
In the body, nitric oxide (the 'endothelium-derived relaxing factor', or 'EDRF') is synthesized from arginine and oxygen by various nitric oxide synthase (NOS) enzymes and by sequential reduction of inorganic nitrate. The endothelium (inner lining) of blood vessels use nitric oxide to signal the surrounding smooth muscle to relax, thus dilating the artery and increasing blood flow. The production of nitric oxide is noted to be increased in high-altitude populations for this effect, which helps to avoid hypoxia in thin air. Nitric oxide is a key biological messenger, playing a role in a variety of biological process. These include blood vessel dilatation, neurotransmission, modulation of the hair cycle, and penile erections. "Nitro" powerful vasodilators such as nitroglycerin are converted to nitric oxide. Similarly, as the name implies, the vasodilating antihypertensive agent Minoxidil is a nitric oxide agonist [1]. Nitric oxide also plays a role in the modulation of hair growth and hair loss. Thus, Minoxidil is also a hair growth stimulator.

Nitric oxide is also generated by macrophages and neutrophils as part of the human immune response. Nitric oxide is toxic to bacteria and other human pathogens. Many bacterial pathogens have evolved mechanisms for nitric oxide resistance.[2]

Nitric oxide can contribute to reperfusion injury when excessive nitric oxide produced during reperfusion (following a period of ischemia) reacts with superoxide to produce the damaging free radical peroxynitrite. Inhaled nitric oxide has been shown to help survival and recovery from paraquat poisoning, which produces lung tissue damaging superoxide and hinders NOS metabolism.
What is NO's role in signal transduction?
signal transduction of guanyl cyclase in tissues such as vascular smooth muscle
Describe the structure of a muscle fiber
- bundle of myofibrils surrounded by the SR and invaginated by T tubules
Describe the muscle thick filament
- Found in the A band
- contain myosin
Describe the muscle thin filament
- anchored at the Z lines
- found in the I bands
- contain actin, tropomyosin, and troponin
What is troponin?
the regulatory protein that allows cross-bridge fomration when it binds to Ca2+
What are the three proteins in Troponin?
- Troponin T: attaches the torponin complex to tropomyosin
- Troponin I: inhibits the interaction fo actin and myosin
- Troponin C: Ca-binding protein that allows actin to bind to myosin whne bound to Ca2+
Where are the t-tubules located?
the junctions of A Bands and I Bands
How are T tubules regulated?
have a voltage sensitive protein called the dihydropyridine receptor. Depolarization causes a confromational change in the receptor.
Describe the protein found in T tubules
DHPR: Dihydorpyridine receptor. It interacts with the ryanodine receptor (RYR). When Ca is released from the terminal cisternae fo the SR, a conformational change takes place at the DHRP and this opens the RYR, releasing Ca into the myoplasm
What two other proteins are found near the RYR?
1. Triadin: involved in RYR interaction with DHPR
2. Calsequestrin: low-affinitiy Ca binding protein taht allows Ca to be stored at high concnetration --> makes a concentration gradient that facilitates the efflux fo Ca from the SR into the myoplasm when the RYR opens
Define isometric contraction
length is held constant. No muscle shortening
Isotonic contraction
Load is held constant. Shortening of muscle
Why doesn't smooth muscle appear striated?
it's thick and thin filaments are not arranged in sarcomeres.
What innervates arterial smooth muscle?
Contrast contraction regulation in skeletal and smooth muscle
Skeletal m: increase in intracellular Ca affects actin
Smooth m: increase in intracellular Ca affects myosin
where do you find multi-unit smooth muscle?
iris, ciliary muscle of the lens, and vas deferens
where do you find unitary smooth muscle?
uterus, GI tract, ureter, and bladder
What is found in skeletal muscle but not in smooth muscle?
What is an ineffective osmole?
Urea. It is really small and has a reflection coefficient close to zero (completely permeable)
in skeletal muscle, what occurs before depolarization of the T tubules?
depolarization of the sarcolemmal membrane