Cellular physiology

Question 1

Name two hormones that use cGMP as a second messenger.

Answer 1

ANF (antrial natriuretic factor) and Nitric Oxide

Question 2

Do secondary active transport proteins use ATP?

Answer 2

no, but ATP may be expended elsewhere in the cell to maintain concentration gradients that permit secondary active transport

Question 3

How do electrical forces affect the rate of diffusion?

Answer 3

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

Question 4

Which active transport process consumes up to 40% of all ATP produced in the body and is a significant source of heat?

Answer 4

sodium-potassium ATPase (aka exchange pump)

Question 5

ACh released through exocytosis diffuses across the synaptic cleft and causes a ________ depolarization which may or may not result in an action potential.

Answer 5

graded depolarization

Question 6

T/F: ACh released into the synapse is quickly repackaged and reabsorbed into the synaptic knob so that it can be reused.

Answer 6

False. The ACh is broken down by acetylcholinesterase into choline and acetate. The choline is reabsorbed and used to synthesize de novo ACh.

Question 7

The chemical gradient for potassium ions tends to drive them out of the cell, but this movement is opposed by the _______ gradient.

Answer 7

electrical

Question 8

Name some important hormones that activate adenylate cyclase (ie: use the cAMP second messenger system). (10)

Answer 8

glucagon, epinephrine and norepinephrine (beta receptors), calcitonin, PTH, ADH, ACTH, FSH, LH, TSH

Question 9

What triggers the release for neurotransmitters at the synaptic nob?

Answer 9

the arrival of the action potential

Question 10

Name the key second messengers. (3)

Answer 10

cATP, cGTP, calcium ions

Question 11

Which is faster: continuous or saltatory conduction of action potentials?

Answer 11

saltatory

Question 12

Which type of intracellular connection results in a narrow passageway that lets small ions pass from cell to cell?

Answer 12

gap junction

Question 13

As a result of the rapid depolarization caused by sodium channels opening, _________ channels open, causing a sudden movement of positive ions ________ of the cell.

Answer 13

voltage gated potassium channels; outside of the cell

Question 14

What would happen to the resting membrane potential if the cell suddenly became freely permeable to sodium?

Answer 14

sodium would enter the cell until the equilibrium potential for sodium is reached (+66mV)

Question 15

As a result of opening voltage gated sodium channels, sodium rushes ______ the cell, raising the membrane potential from -70mV to _____mV.

Answer 15

Into the cell, +30mV

Question 16

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.

Answer 16

higher

Question 17

Name two places where ACh is always used as a neurotransmitter.

Answer 17

all neuron-to-neuron junctions in the PNS; All neuroeffector junctions of the sympathetic division of the ANS

Question 18

How does temperature affect the rate of diffusion?

Answer 18

higher temperatures increase the rate of diffusion

Question 19

A typical threshold for an action potential is between ______ mV and _____ mV.

Answer 19

-60mV and -55mV

Question 20

Name six functional types of membrane proteins

Answer 20

anchors, identifiers, enzymes, receptors, carriers and channels

Question 21

Name two important hormones that inhibit adenylate cyclase.

Answer 21

epinephrine and nonepinephrine (alpha 2 receptors).

Question 22

Name the chief molecular component of the ‘intercellular’ cement that holds intermediate junctions together.

Answer 22

hyaluronic acid

Question 23

Regarding polarization: Exitatory neurotransmitters cause ______ wheras inhibitory neurotransmitters cause ______.

Answer 23

depolarization (promote action potentials); Hyperpolarization (depress action potentials)

Question 24

T/F: It is easier for a potassium ion to leave a cell than it is for a sodium ion to enter a cell

Answer 24

true

Question 25

How does lymphatic blockage lead to edema?

Answer 25

increased fluid colloid osmotic pressure

Question 26

Does active transport rely on the concentration gradient of the solute being transported?

Answer 26

no

Question 27

What would happen to the resting membrane potential if the cell suddenly became freely permeable to potassium?

Answer 27

potassium would leave the cell until the equilibrium potential for potassium is reached. (-90mV)

Question 28

Name four places where ACh may be used as a neurotransmitter.

Answer 28

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

Question 29

T/F: The fastest reflexes have just one synapse. As synapses increase, so does delay.

Answer 29

true

Question 30

The electrical gradient for sodium tends to push them into the cell, and this enhanced by the ____ gradient.

Answer 30

chemical

Question 31

Name some important hormones that activate phospholipase C (use calcium as a second messenger). (5)

Answer 31

epinephrine and non epinephrine (alpha 1 receptors), oxytocin, regulatory hormones of the hypothalamus, several elcosanoids.

Question 32

What is required to activate protein kinases?

Answer 32

second messenger

Question 33

What is the main way that a cell maintains its resting potential?

Answer 33

sodium-potassium exchange pump

Question 34

Is ATP required for facilitated diffusion?

Answer 34

no

Question 35

Type _____ fibers are smaller myelinated axons.

Answer 35

type B

Question 36

Which form of endocytosis is the most specific?

Answer 36

receptor mediated endocytosis is the most selective process, bringing in only molecules that the cell specifically needs.

Question 37

The extracellular fluid contains relatively ______ concentrations of sodium ions and chloride ions.

Answer 37

high

Question 38

How many molecules of sodium and potassium enter/exit the cell in each cycle of the sodium-potassium exchange pump?

Answer 38

two potassium in, three sodium out

Question 39

The depolarization of the synaptic knob causes the opening of _____ channels.

Answer 39

voltage gated calcium channels

Question 40

Why is glucose added to sodium in oral rehydration formulas? What specific form of cellular transport is being exploited?

Answer 40

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.

Question 41

T/F: The passive channels and active transporters ensure an equal distribution of positive and negative charges across the cell membrane.

Answer 41

false

Question 42

Type ___ fibers are the smallest and slowest axons. Unlike the other two types they are not myelinated?

Answer 42

type C

Question 43

Describe the tonicity of a solution that creates an osmotic force that pulls water out of a cell.

Answer 43

hypertonic

Question 44

Type __ fibers are the largest and fastest axons.

Answer 44

type A

Question 45

The resting potential primarily reflects the relatively high membrane permeability to ____ions.

Answer 45

potassium

Question 46

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.

Answer 46

true

Question 47

Describe the tonicity of a solution that does not generate an osmotic force in or out of a cell

Answer 47

isotonic

Question 48

The cytosol contains relatively ______ concentrations of potassium ions and negatively charged proteins.

Answer 48

high

Question 49

Do all cells maintain resting potentials?

Answer 49

yes. the range is between -10mV and -100mV

Question 50

How does the size of the concentration gradient affect rate of diffusion?

Answer 50

the larger the concentration gradient, the faster the rate of diffusion

Question 51

Which enzyme "turns off" the cAMP second messenger system?

Answer 51

phospodiesterase

Question 52

What would happen to the resting membrane potential if the cell were freely permeable to sodium?

Answer 52

the membrane potential would become more positive (approach zero).

Question 53

Which intracellular protein must second messenger calcium ions bind in order to have an effect on target enzymes?

Answer 53

calmodulin

Question 54

Which type of intercellular connection uses a very thin proteoglycan layer reinforced by a network of intermediate filaments to lock two cells together?

Answer 54

desmosomes

Question 55

What does osmolarity measure?

Answer 55

the number of moles of solute particles per unit volume of solution.

Question 56

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?

Answer 56

receptor mediated endocytosis.

Question 57

What happens to neurons as pH rises? As pH falls?

Answer 57

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

Question 58

Is the sodium potassium-pump a form of active transport?

Answer 58

yes

Question 59

T/F: The release of ACh causes the generation of an action potential across a synapse in an all-or-none fashion.

Answer 59

false

Question 60

The sudden influx of calcium in the synaptic knob triggers ____ of vesicles and release of neurotransmitter.

Answer 60

exocytosis

Question 61

The equilibrium potential for ___ is about -90mV.

Answer 61

potassium

Question 62

How does distance affect diffusion?

Answer 62

longer distances require more time for diffusion to occur.

Question 63

What effect does a 10% nasal salt solution have on the cells lining the nasal cavity?

Answer 63

nasal cell will shrink and release water, thus loosening mucus and relieving congestion.

Question 64

T/F: The greater the degree of sustained depolarization at the axon hillock, the higher the frequency of action potential generation.

Answer 64

true

Question 65

Which forms of endocytosis require ATP? (receptor-mediated, pinocytosis, phagocytosis)

Answer 65

all of them

Question 66

Does active transport require ATP?

Answer 66

yes

Question 67

Can facilitated diffusion move molecules against their concentration gradient?

Answer 67

no

Question 68

What is required to activate protein kinases?

Answer 68

second messenger

Question 69

Which have faster and more immediate effects- water soluble or lipid soluble hormones?

Answer 69

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)

Question 70

T/F: Postsynaptic potentials may be summated in spatially, but not temporally.

Answer 70

false. both spatial and temporal summation are possible

Question 71

The inside of a cell membrane has a slight ___ charge with respect to the outside.

Answer 71

negative

Question 72

Where are desmosomes abundant? (2)

Answer 72

superficial skin layers, cardiac muscle tissue

Question 73

Which type of intercellular connection involves partial fusion of the lipid portions of two cell membranes?

Answer 73

tight junction

Question 74

Voltage gated sodium channels open at __mV, and voltage gated potassium channels open at __mV.

Answer 74

-60mV; +30mV

Question 75

Why does facilitated transport proceed slower than diffusion?

Answer 75

carrier proteins are saturable.

Question 76

Although acetylcholine typically has a ___effect on the postsynaptic membrane, it has a ___ effect when released at neuromuscular junctions in the heart.

Answer 76

depolarizing; inhibitory (hyperpolarizing)

Question 77

Name the force that pushes water and dissolved solutes into tissues of the body.

Answer 77

hydrostatic pressure

Question 78

Which channels open when voltage reaches the threshold for n action potential?

Answer 78

voltage gated sodium channels open first, causing rapid depolarization.

Question 79

Is osmotic pressure a force that pushes water into a compartment, or is it a force that pushes water out of a compartment?

Answer 79

the osmotic pressure is a force that pushes water into a compartment.

Question 80

T/F: Norepinephrine often has an exitatory depolarizing effect on post synaptic membranes that is similar to ACh

Answer 80

false. The exitatory, depolarizing effect of NE has a distinct mechanism from ACh.

Question 81

Describe the tonicity of a solution that creates an osmotic force that pushes water into a cell.

Answer 81

hypotonic

Question 82

How does molecular size affect rate of diffusion?

Answer 82

ions and smaller molecules like glucose diffuse much faster than larger molecules (like proteins).

Question 83

Where are gap junctions most common? (2)

Answer 83

cardiac muscle and smooth muscle tissue

Question 84

The equilibrium potential for ___ is about +66mV.

Answer 84

sodium

Question 85

Osmosis is the diffusion of ___ through a semi-permeable membrane.

Answer 85

water

Question 86

T/F: Continuous propagation cannot occur in a myelinated axon.

Answer 86

true

Question 87

Where are tight junctions most common? (1)

Answer 87

near the exposed surfaces of cells lining the digestive tract, thus preventing stomach acids, enzymes etc from damaging underlying tissues.

Question 88

Will lowering the resting membrane potential to -65mV produce an action potential?

Answer 88

no, the potential must be raised to at least -60mV, which is the threshold for most axons.