Valley Cell Physiology Flashcards
All of the following statements are true of the lipid bilayer EXCEPT:
a. It has cholesterol as one of its components
b. It contains only saturated fatty acids
c. It is comprised mostly of phospholipids
d. It provides an environment in which proteins can function
b.
Characteristics of the lipid bilayer 50% (volume) lipid by composition:
- phospholipids (most abundant)
- glycolipids
- cholesterol
50% (volume) protein by composition:
- channels
- receptors
- enzymes
Provides a structure/skeleton for proteins to function within.
Competitive antagonists attach to receptors and:
a. irreversibly alter them
b. mimic agonists
c. uncouple receptors from G proteins
d. prevent attachment of agonist
d.
Competitive Antagonists Attach to receptors and prevent attachment of agonist.
Lock and Key Analogy: The key fits in the lock, but doesn’t unlock it. But it continues to block the keyhole so that the correct key (agonists) cannot fit into the lock to open it.
Which substance on the list below LEAST penetrates the lipid bilayer?
a. Sodium ions(Na+)
b. Sodium pentothal
c. Caron dioxide
d. Halothane
a.
Substances that can penetrate the lipid bilayer Hydrophobic molecules (i.e. intravenous and inhalation anesthetics)
Small uncharged polar molecules (i.e. water, carbon dioxide)
note Ions are the LEAST likely to penetrate the lipid bilayer. Large uncharged polar molecules do not readily cross the lipid bilayer.
Neurotransmitter is released from the nerve terminal by a process known as:
a. exocytosis
b. endocytosis
c. pinocytosis
d. receptor-mediated endocytosis
a.
Neurotransmitters are released from the nerve terminals by what process? Neurotransmitters are released via exocytosis.
ALMOST ALL NEUROTRANSMITTERS RELY ON CALCIUM-DEPENDENT EXOCYTOSIS
An increase in myocardial contractility caused by dobutamine involves which signal transduction system?
G PROTEIN—-ENZYME—-SECOND MESSENGER
a. G1—-Guanylate cyclase—-cGMP
b. Gi—-Adenylate cyclease—-cAMP
c. Gs—-Guanylate cyclase—-cGMP
d. Gs—-Adenylate cyclase—-cAMP
d.
Cardiac contractility involves what type of signal transduction system? G-coupled protein receptors
A first messenger such as a beta-1 agonist (dobutamine) will attach to the membrane bound, stimulatory G-protein. The GCP will relay information to an enzyme (adenylate cyclase), which when stimulated will create the second messenger (cAMP) with the use of ATP. The cAMP will trigger the intracellular events.
The sodium-potassium pump is stimulated by
a. insuline
b. epinephrine
c. both
d. neither
c.
What stimulates the sodium-potassium pump? The sodium-potassium ATPase pump is stimulated by:
- insulin: this is why you can give insulin to hyperkalemic patients, to drive the K+ into the cells using the S-P pump
- Beta-2 adrenergic receptor agonists: this explains why beta-adrenergic receptor agonists such as ritodrine and terbutaline can promote hypokalemia
What ions move in what direction during depolarization and repolarization of the nerve?
DEPOLARIZATION—–REPOLARIZATION
a. Na+ out—–K+ in
b. Na+ in—–K+ out
c. K+ in—–Na+ out
d. K+ out—–Na+ in
b.
Ion movement across the membrane during depolarization and depolarization of a nerve. Depolarization: There is an INWARD diffusion of sodium ions (Na+) that takes the RMP to the TP
Repolarization: The voltage-gated potassium channels are open (because the membrane potential is positive ~ +20mV), this allows a rapid OUTWARD flow of potassium that takes the membrane potential back to RMP.
Which electrolyte disturbance causes the resting cell to hypo-polarize(depolarize)?
a. Hyponatremia
b. Hypernatremia
c. Hypokalemia
d. Hyperkalemia
d.
Which electrolyte disturbance causes the resting cell to hypo polarize (depolarize)? Hyperkalemia - thus the occurrence of cardiac dysrhythmias.
When the sodium channel is in the inactivated state, the neuron is:
a. hyper-polarized
b. repolarized
c. absolutely refractory
d. relatively refractory
c.
When the sodium channel is in the inactivated state, the neuron is…? In the absolutely refractory state.
Voltage-gated sodium channels close when the full amplitude of the depolarization is achieved. They remain inactive/closed until approx. -60 mV, or the start of the relative refractory period.
The Na+/K+ pump transports sodium and potassium ions against concentration gradients at what ratio?
NA+/K+
a. 3 in/2 out
b. 2 out/3 in
c. 3 out2 in
d. 2 in/3 out
c.
The sodium-potassium pump transports NA+ and K+ against concentration gradients at what ratio? 3 sodium out
2 potassium in
The 5-HT3 receptor is antagonized by ondansetron(Zofran). What type of receptor is the serotonergic 5-HT3 receptor?
a. metabotropic
b. ionotropic
c. G-protein coupled
d. enzyme-linked transmembrane
b.
Zofran antagonizes the 5-HT3 receptor
5-HT3 receptors are ionotropic.
- ionotropic: the signaling molecule itself controls the opening and closing of an ion channel - ligand-gated ion channel
- metabotropic: the signaling molecule doesn’t open an ion channel, but signals a protein in the cell (usually G-coupled protein) to signal an enzyme to create a second messenger which then elicits a cellular response.
The ion channel that governs resting membrane potential of most excitable tissue is the:
a. voltage-gated rectifying potassium channel
b. “leaky” potassium channel
c. fast, voltage gated sodium channel
d. ligand-gated potassium channel
b.
potassium leak channel
remember that sodium leak channels are more “leaky” than potassium leak channels, but that the potassium leak channels have more effect on the RMP.
