5-feb-2014 physiology

Question 0

What is the approximate magnitude of the resting membrane potential

Answer 0

-70 to -90

Question 1

What is the polarity of the resting potential in nerve and muscle

Answer 1

Negative

Question 2

What would be the polarity of the resting member potential if the membrane were selectively permeable to only Cl-

Answer 2

Negative

Question 3

what are the forces acting on an ion which affect the directional Net flux for an ion across the member

Answer 3

Chemical and electrical potential energy gradients

Question 4

Is it true that when an ion is an equilibrium across the cell membrane there is no net movement of ions between the intracellular and extracellular fluid. does this mean that there is no Ion moving across the membrane or does this mean that the influx (movement into the cell) of the ions equals efflux (moving out of cell)

Answer 4

Influx = Efflux at equilibrium

Question 5

What are the conditions required for the generation of the diffusion potential across the cell membrane

Answer 5

Ion concentration gradient

Question 6

Potential membrane was measured it -60mV, potassium equilibrium potential was calculated -90mV, isotope study shows that the membrane potential is permeable to potassium.
True or false: the intracellular potassium concentration is greater than the extracellular potassium concentration?

Answer 6

True

Question 7

What determines the maximum frequency with which action potentials can be elicited

Answer 7

The duration of the absolute refractory.

Question 8

What affect would an increase in duration of the action potential have on the duration of the absolute refractory period

Answer 8

Increase

Question 9

What would the effect of an increase extracellular potassium concentration on the ability of the nerve to produce an action potential (consider the effect of Ko on membrane potential)?

Answer 9

Decreased ability to produce an action potential due to the inactivation of the sodium system with the membrane depolarization produced by the increase K outside

Question 10

Defined the threshold potential

Answer 10

Threshold potential might be defined as the membrane potential at which sufficient sodium channels are in the active state to allow self-sustaining feedback between sodium influx and membrane depolarization to occur

Question 11

Patient has myotonia characterized by muscle stiffness students and impaired relaxation after muscle contraction. examination shows the patient has difficulty releasing her grip after shaking hands with the physician and has difficulty in opening the eyelids after gene encoding the sodium channel protein and skeletal muscle sodium channels and other tissues are unaffected. The patients skeletal muscle are hyperexcitable whereas the contractile mechanism and excitation contraction coupling are normal.
what defect in sodium channel function might be responsible for hyperexcitability of the patients skeletal muscle?

Answer 11

The most likely defective sodium channels and most cells which could explain the hyperexcitability and prolonged contraction is a decrease inefficacy. Alpha subunit sticks out of cytoplasm

Question 12

What would be record from a single sodium channel look like from a patient with myotonia characterized by muscle stiffness and impaired relaxation after contraction, compared to that of a normal individual

Answer 12

Recording from single sodium channels in muscles of affected patients would show prolonged opening times compared to those from single sodium channels from normal individuals

Question 13

Phase 0 of an action potential represents

Answer 13

Depolarization (Na+ enters the cell)

Question 14

Phase 1 of an action potential represents

Answer 14

Early repolarization (potassium flows out of the cell)

Question 15

Phase 2 of the action potential represents

Answer 15

Phase 2 represents the plateau with increased calcium conductance, increase slow sodium conductance, and a decrease in potassium conductance.

Question 16

Phase 3 represents

Answer 16

Repolarization (potassium moves outside)

Question 17

Protein filaments compose each myofibril of myosin and what

Answer 17

Actin (thick filaments)

Question 18

The contractile unit of a muscle fiber is called a sarcomere which is measured from these two lines

Answer 18

Z line to z line

Question 19

The a band represents

Answer 19

The a band is the only portion of the sarcomere which has an overlap of both actin and myosin. The a band also contains the H band and m line. The a band does not change in length.

Question 20

The I band is composed mainly of

Answer 20

Actin filaments (thin filaments)

Question 21

The H band primarily contains

Answer 21

Thick filaments, the only portion of the Sarcomere that contains just myosin filaments

Question 22

The online is the only portion of the sarcomere that does not change. True or false?

Answer 22

False, the a band does not change post contraction

Question 23

Smooth muscle contraction needs this to be released from hormones or neurotransmitters resulting calcium to be released from SR, increasing the calcium concentration.

Answer 23

Ip3

Question 24

For smooth muscle contraction after the increase calcium concentration, Ca binds to calmodulin, resulting in...

Answer 24

Increase of myosin light chain kinase

Question 25

For smooth muscle contraction, after dephosphorylation of myosin light chains, an increase in myosin ATPase results in

Answer 25

Myosin-P + Actin

Question 26

Smooth muscle contraction finally needs MyosinP + Actin, which activates

Answer 26

Cross bridge cycling resulting in tension

Question 27

In cardiac muscle the action potential is caused by opening of two types of channels

Answer 27

The fast sodium channels as those in skeletal muscle and slow calcium channels

Question 28

The interval of time in which a normal cardiac impulse cannot re excited and already excited area of cardiac muscle is defined as this.

Answer 28

Refractory period

Question 29

The period in cardiac muscle described when the muscles are more difficult than normal to excite, but nevertheless can be excited by very strong excitatory signal, is called the this is this

Answer 29

Relative refractory period

Question 30

The degree of tension on the muscle when it begins to contract is referred to as

Answer 30

Preload

Question 31

The load against which the muscle exerts its contractile force is referred to as the

Answer 31

Afterload. The afterload of the ventricle is the pressure in the artery leading from the ventricle.

Question 32

Basically the Frank starling mechanism means that the greater the heart muscle is stretched during filling the greater is the force...

Answer 32

Greater is the force of contraction and the greater the quantity of blood pumped into the aorta.

Question 33

This drug blocks cholinergic activity at effector organs but does not affect the nicotinic action of acetylcholine on the postganglionic neurons or on skeletal muscle

Answer 33

Atropine

Question 34

Drugs that cause autonomic effects by stimulating postganglionic neurons are called

Answer 34

Nicotinic

Question 35

A 40-year-old man presents to his primary care physician two months history of intermittent abdominal pain, pain is a burning, dull ache which sometimes awakes patient at night and is relieved by food, drinking milk, and PO omeprazole. PE reveals apparently healthy man, no distress, with the only abdominal finding of mild epigastric tenderness on palpation. give the name of the transport mechanism involved in this patient's problem.

Answer 35

Problem with primary active transport (proton pump) producing hypersecretion of acid

Question 36

Dihydropyridine (DHP) receptor In a membrane of T tubules, role as voltage sensor mechanically coupled to calcium released channel - ryanodine receptor .....

Answer 36

Block by DHP calcium channel blockers

Question 37

``` Ryanodine receptor (Ca+ release channel) In a membrane terminal cisternae, Ca+ release channel, opened by conformational change in... ```

Answer 37

DHP receptor (skeletal)