For all questions choose the INCORRECT
answer

1) Integral membrane proteins:

a) Osmosis across the lipid bilayer membrane uses protein
channels that form open pores connecting the interstitial fluid
space with the intracellular fluid compartment

b) A decrease in membrane permeability to a hydrophilic cation
could be the result of decreasing the number of open voltage-gated
channel proteins

c) Uniport and symport carriers enable the diffusion of glucose
from the ECF to the ICF

d) Antiport transporters move substrates in opposite directions
with and without the expenditure of energy in the form of ATP

2) Synaptic transmission:

a) Ca++ binding to synaptotagamin is necessary for hormone
containing vesicles to alter their conformations to allow vesicle
fusion and exocytosis of arginine vasopressin from nerve
terminals

b) Electrical synaptic transmission does not require the opening
of voltage-gated Ca++ channels while chemical synaptic transmission
will not occur unless voltage-gated Ca++ channels are opened

c) !-bungarotoxin is an exogenous agonist that, acting as a
ligand, opens ion channels that are necessary and sufficient for
the generation of suprathreshold end-plate potentials

d) Neurotransmitters are 1st messenger molecules that bind to
integral proteins which function either as ligand-gated ion
channels or as G protein-coupled receptors that indirectly open ion
channels

3) SA

a) The SA nodal cell action potential(AP) is initiated, in part,
by an inward Na+ current, If, and differs from a muscle action
potential because the rising phase of the SA nodal cell AP is due
to opening of voltage-gated Ca++ channels

b) Epinephrine binding to “#receptors in SA nodal cell membranes
results in an increase in the slope of pacemaker potentials, an
increase in heart rate and an increase in cardiac contractility

c) ACh binding to muscarinic receptors in SA nodal cell
membranes decreases the slope of the graded potential generated by
the opening of ‘funny’ voltage-gated channels

d) The resting membrane potential in a ventricular muscle cell
is more negative than the resting membrane potential in a SA nodal
cell, in part, because ventricular cell membranes do not contain
voltage-gated, non-selective cation, HCN channels

4) Action potentials (APs):

a) Saltatory conduction of APs occurs because voltage-gated Na+
channels and voltage-gated K+ channels are not contiguously
inserted in the axonal membrane of myelinated fibers, but rather
are localized to nodes of Ranvier

b) During the relative refractory period, a suprathreshold
depolarizing stimulus can open a sufficient number of voltage-gated
Na+ channel activation gates to initiate the depolarization phase
of an AP

c) During the depolarization phase of the AP activation gates in
voltage-gated K+ channels are closed and simultaneously
inactivation gates in voltage-gated Na+ channels are open

d) During the initial period of the repolarization phase,
activation gates of Na+ channels and K+ channels are open, and the
permeability of the membrane to both ions is increasing

5) Orthostatic hypotension:

a) The precipitous drop in MAP due to gravitational forces on
blood is reversed, in part, by increasing heart rate due to
increased sympathetic cardiac nerve action potential activity

b) The transient decrease in cardiac output is the result of a
transient decrease in stroke volume

c) The reflex increase in MAP following orthostatic hypotension
is the result of an increase in cardiac output which is greater
than the decrease in peripheral resistance

d) The transient decrease in left ventricular end-diastolic
volume due to decreased venous return results in a decrease in
carotid sinus baroreceptor action potential discharge activity

6) Renal regulation of Na+ and H2O reabsorption:

a) If plasma osmolarity increased to 400 mOsm (normal is 300
mOsm), plasma levels of AVP would increase and aquaporin channel
density would increase in the apical membrane of collecting duct
cells

b) When the RAAS system is activated, H2O reabsorption via
transepithelial transport in proximal tubules increases if there is
a concomitant increase in plasma levels of AVP levels

c) Na+ reabsorption is an active process despite the fact that
the initial movement of Na+ from tubular fluid into tubular cells
is down a concentration gradient using either a carrier protein or
through an open porechannel

d) If an autoimmune disease destroyed AVP receptors in kidney
tubular membranes, urine output would increase, in part, because
collecting duct epithelial cells manifest a permanent decrease in
their permeability to H2O

7) Resting membrane potential (unless otherwise stated assume
the [ion] in, out given below apply and that the membrane is
selectively permeable to only Na+ and K+ ): [K+]in=150mM
[K+]out=5mM [Na+]in=5mM [Na+]out=150mM

a) If one doubled the intracellular concentration of Na+, the
resting membrane potential would be more negative

b) The equilibrium potential for K+ would be zero(0) if membrane
permeability increased in a cell selectively permeable to Na+

c) If the permeability to Na+ increased 10 fold, and the ratio
of PK / PNa remained constant, the resting membrane potential would
be less negative

d) In a cell permeable to Na+ and K+, the resting membrane
potential = 0 mv for a muscle fiber in rigor

8) Comparison of peptide, catecholamine and steroid
hormones:

a) Hydrophobic steroid hormones differ from lipophobic peptide
and catecholamine hormones in that for steroids to be transported
to distant physiological targets they must be bound to protein
carriers

b) Opening of voltage-gated Ca++ channels is necessary for the
release of peptide hormones but is not required for the release of
steroid hormones

c) The response times for the release of steroid hormones are
longer than the response times for the release of catecholamine and
peptide hormones because steroid hormones are synthesized on demand
while peptide and catecholamine hormones are released on demand

d) Peptide and catecholamine hormones bind to membrane receptors
which activate 2nd messenger pathways, while G-protein linked
responses to steroid hormones depend upon initial binding to
intracellular or nuclear receptors

9) Cellular signaling:

a) In direct gating of an ion channel the 1st messenger binds to
a receptor whose opening or closing generates hyperpolarizing or
depolarizing potentials that may elicit action potentials

b) The muscarinic receptor in SA nodal cell membranes is
G-protein coupled, binds ACh, increases K+ permeability, and upon
activation results in decreases in heart rate

c) Amplifier enzymes can be activated by !-subunits or
“$-subunits of G proteins in response to binding of 1st messenger
ligands to transmembrane receptors

d) If ACh opened a chemically-gated channel that increased PNa
and PK, systemic administration of an irreversible antagonist to
this receptor would cause muscle relaxation