Cellular physiology Flashcards
Name two hormones that use cGMP as a second messenger.
ANF (antrial natriuretic factor) and Nitric Oxide
Do secondary active transport proteins use ATP?
no, but ATP may be expended elsewhere in the cell to maintain concentration gradients that permit secondary active transport
How do electrical forces affect the rate of diffusion?
the slight negative charge on the inside of a cell membrane increases the rate of diffusion of positive species and reduces the rate of diffusion of negative species
Which active transport process consumes up to 40% of all ATP produced in the body and is a significant source of heat?
sodium-potassium ATPase (aka exchange pump)
ACh released through exocytosis diffuses across the synaptic cleft and causes a ________ depolarization which may or may not result in an action potential.
graded depolarization
T/F: ACh released into the synapse is quickly repackaged and reabsorbed into the synaptic knob so that it can be reused.
False. The ACh is broken down by acetylcholinesterase into choline and acetate. The choline is reabsorbed and used to synthesize de novo ACh.
The chemical gradient for potassium ions tends to drive them out of the cell, but this movement is opposed by the _______ gradient.
electrical
Name some important hormones that activate adenylate cyclase (ie: use the cAMP second messenger system). (10)
glucagon, epinephrine and norepinephrine (beta receptors), calcitonin, PTH, ADH, ACTH, FSH, LH, TSH
What triggers the release for neurotransmitters at the synaptic nob?
the arrival of the action potential
Name the key second messengers. (3)
cATP, cGTP, calcium ions
Which is faster: continuous or saltatory conduction of action potentials?
saltatory
Which type of intracellular connection results in a narrow passageway that lets small ions pass from cell to cell?
gap junction
As a result of the rapid depolarization caused by sodium channels opening, _________ channels open, causing a sudden movement of positive ions ________ of the cell.
voltage gated potassium channels; outside of the cell
What would happen to the resting membrane potential if the cell suddenly became freely permeable to sodium?
sodium would enter the cell until the equilibrium potential for sodium is reached (+66mV)
As a result of opening voltage gated sodium channels, sodium rushes ______ the cell, raising the membrane potential from -70mV to _____mV.
Into the cell, +30mV
In osmosis, water flows across a membrane toward a solution that has a _____concentration of solutes, because that is where the concentration of water is lowest.
higher
Name two places where ACh is always used as a neurotransmitter.
all neuron-to-neuron junctions in the PNS; All neuroeffector junctions of the sympathetic division of the ANS
How does temperature affect the rate of diffusion?
higher temperatures increase the rate of diffusion
A typical threshold for an action potential is between ______ mV and _____ mV.
-60mV and -55mV
Name six functional types of membrane proteins
anchors, identifiers, enzymes, receptors, carriers and channels
Name two important hormones that inhibit adenylate cyclase.
epinephrine and nonepinephrine (alpha 2 receptors).
Name the chief molecular component of the ‘intercellular’ cement that holds intermediate junctions together.
hyaluronic acid
Regarding polarization: Exitatory neurotransmitters cause ______ wheras inhibitory neurotransmitters cause ______.
depolarization (promote action potentials); Hyperpolarization (depress action potentials)
T/F: It is easier for a potassium ion to leave a cell than it is for a sodium ion to enter a cell
true
How does lymphatic blockage lead to edema?
increased fluid colloid osmotic pressure
Does active transport rely on the concentration gradient of the solute being transported?
no
What would happen to the resting membrane potential if the cell suddenly became freely permeable to potassium?
potassium would leave the cell until the equilibrium potential for potassium is reached. (-90mV)
Name four places where ACh may be used as a neurotransmitter.
all neuromuscular junctions involving skeletal muscle; many synapses inside the CNS; all neuron-to-neuron synapses in the PNS; all neuroeffector junctions of the parasympathetic division of the ANS
T/F: The fastest reflexes have just one synapse. As synapses increase, so does delay.
true
The electrical gradient for sodium tends to push them into the cell, and this enhanced by the ____ gradient.
chemical
Name some important hormones that activate phospholipase C (use calcium as a second messenger). (5)
epinephrine and non epinephrine (alpha 1 receptors), oxytocin, regulatory hormones of the hypothalamus, several elcosanoids.
What is required to activate protein kinases?
second messenger
What is the main way that a cell maintains its resting potential?
sodium-potassium exchange pump
Is ATP required for facilitated diffusion?
no
Type _____ fibers are smaller myelinated axons.
type B
Which form of endocytosis is the most specific?
receptor mediated endocytosis is the most selective process, bringing in only molecules that the cell specifically needs.
The extracellular fluid contains relatively ______ concentrations of sodium ions and chloride ions.
high
How many molecules of sodium and potassium enter/exit the cell in each cycle of the sodium-potassium exchange pump?
two potassium in, three sodium out
The depolarization of the synaptic knob causes the opening of _____ channels.
voltage gated calcium channels
Why is glucose added to sodium in oral rehydration formulas? What specific form of cellular transport is being exploited?
these proteins use the energy from a downhill sodium gradient to transport glucose across the apical membrane against an uphill glucose gradient. Therefore, these co-transporters are an example of secondary active transport.
T/F: The passive channels and active transporters ensure an equal distribution of positive and negative charges across the cell membrane.
false
Type ___ fibers are the smallest and slowest axons. Unlike the other two types they are not myelinated?
type C
Describe the tonicity of a solution that creates an osmotic force that pulls water out of a cell.
hypertonic
Type __ fibers are the largest and fastest axons.
type A
The resting potential primarily reflects the relatively high membrane permeability to ____ions.
potassium
T/F: Catecholamines, peptide hormones and eicosanoids do not exert their effects directly, but by acting as first messengers that cause the appearance of second messengers in the cytoplasm.
true
Describe the tonicity of a solution that does not generate an osmotic force in or out of a cell
isotonic
The cytosol contains relatively ______ concentrations of potassium ions and negatively charged proteins.
high
Do all cells maintain resting potentials?
yes. the range is between -10mV and -100mV
How does the size of the concentration gradient affect rate of diffusion?
the larger the concentration gradient, the faster the rate of diffusion
Which enzyme “turns off” the cAMP second messenger system?
phospodiesterase
What would happen to the resting membrane potential if the cell were freely permeable to sodium?
the membrane potential would become more positive (approach zero).
Which intracellular protein must second messenger calcium ions bind in order to have an effect on target enzymes?
calmodulin
Which type of intercellular connection uses a very thin proteoglycan layer reinforced by a network of intermediate filaments to lock two cells together?
desmosomes
What does osmolarity measure?
the number of moles of solute particles per unit volume of solution.
Many substances like iron and cholesterol are attached to transport proteins that are too large to pass through membrane pores. How do they enter the cell?
receptor mediated endocytosis.
What happens to neurons as pH rises? As pH falls?
they are facilitated: at pH near 7.8 , action potentials are spontaneously generated, producing deadly convulsions. As pH falls, neurons are inhibited. At pH 7.0 the nervous system all but shuts down
Is the sodium potassium-pump a form of active transport?
yes
T/F: The release of ACh causes the generation of an action potential across a synapse in an all-or-none fashion.
false
The sudden influx of calcium in the synaptic knob triggers ____ of vesicles and release of neurotransmitter.
exocytosis
The equilibrium potential for ___ is about -90mV.
potassium
How does distance affect diffusion?
longer distances require more time for diffusion to occur.
What effect does a 10% nasal salt solution have on the cells lining the nasal cavity?
nasal cell will shrink and release water, thus loosening mucus and relieving congestion.
T/F: The greater the degree of sustained depolarization at the axon hillock, the higher the frequency of action potential generation.
true
Which forms of endocytosis require ATP? (receptor-mediated, pinocytosis, phagocytosis)
all of them
Does active transport require ATP?
yes
Can facilitated diffusion move molecules against their concentration gradient?
no
What is required to activate protein kinases?
second messenger
Which have faster and more immediate effects- water soluble or lipid soluble hormones?
water soluble hormones can have immediate (seconds to minutes) effects in cells. Lipid soluble hormones have an effect by changing gene expression (hours to days)
T/F: Postsynaptic potentials may be summated in spatially, but not temporally.
false. both spatial and temporal summation are possible
The inside of a cell membrane has a slight ___ charge with respect to the outside.
negative
Where are desmosomes abundant? (2)
superficial skin layers, cardiac muscle tissue
Which type of intercellular connection involves partial fusion of the lipid portions of two cell membranes?
tight junction
Voltage gated sodium channels open at __mV, and voltage gated potassium channels open at __mV.
-60mV; +30mV
Why does facilitated transport proceed slower than diffusion?
carrier proteins are saturable.
Although acetylcholine typically has a ___effect on the postsynaptic membrane, it has a ___ effect when released at neuromuscular junctions in the heart.
depolarizing; inhibitory (hyperpolarizing)
Name the force that pushes water and dissolved solutes into tissues of the body.
hydrostatic pressure
Which channels open when voltage reaches the threshold for n action potential?
voltage gated sodium channels open first, causing rapid depolarization.
Is osmotic pressure a force that pushes water into a compartment, or is it a force that pushes water out of a compartment?
the osmotic pressure is a force that pushes water into a compartment.
T/F: Norepinephrine often has an exitatory depolarizing effect on post synaptic membranes that is similar to ACh
false. The exitatory, depolarizing effect of NE has a distinct mechanism from ACh.
Describe the tonicity of a solution that creates an osmotic force that pushes water into a cell.
hypotonic
How does molecular size affect rate of diffusion?
ions and smaller molecules like glucose diffuse much faster than larger molecules (like proteins).
Where are gap junctions most common? (2)
cardiac muscle and smooth muscle tissue
The equilibrium potential for ___ is about +66mV.
sodium
Osmosis is the diffusion of ___ through a semi-permeable membrane.
water
T/F: Continuous propagation cannot occur in a myelinated axon.
true
Where are tight junctions most common? (1)
near the exposed surfaces of cells lining the digestive tract, thus preventing stomach acids, enzymes etc from damaging underlying tissues.
Will lowering the resting membrane potential to -65mV produce an action potential?
no, the potential must be raised to at least -60mV, which is the threshold for most axons.
