Lab 2 PhysioEx Notes Flashcards
the heart’s ability to trigger its own contractions is called …
autorhythmicity
autorhythmicity occurs because the plasma membrane in cardiac pacemaker muscle cells has reduced permeability to … ions but still allows … and … ions to slowly leak into cells
potassium;
sodium; calcium
this leakage of sodium and calcium ions causes the muscles to slowly depolarize until the action potential … is reached and … channels open, allowing … entry from the extracellular fluid.
threshold; L-type calcium;
Ca2+
the spontaneous depolarization-repolarization events occur in a regular and continuous manner in cardiac pacemaker muscle cells, leading to … in the majority of cardiac muscle
cardiac action potentials
There are five main phases of membrane polarization in a cardiac action potential:
phase 0 is similar … in the neuronal action potential. depolarization causes voltage-gated sodium channels in the cell membrane to open, increasing the flow of… ions into the cell and increasing the membrane potential.
🙄depolarization; sodium
There are five main phases of membrane polarization in a cardiac action potential:
in phase 1, the open sodium channels begin to inactivate, decreasing the flow of sodium ions into the cell and causing the membrane potential to fall slightly. at the same time, … close and … channels open. the subsequent decrease in the flow of potassium out of the cell and increase in the flow of calcium into the cell act to … the membrane and curb the fall in membrane potential caused by the inactivation of sodium channels
voltage-gated potassium channels;
voltage-gated calcium;
depolarize
There are five main phases of membrane polarization in a cardiac action potential:
in phase 2, known as the …, the membrane remains in a depolarized state. potassium channels stay closed, and… (…-type) calcium channels stay open. this plateau lasts about … s, or … ms
plateau phase;
long-lasting; L-type;
0.2; 200
There are five main phases of membrane polarization in a cardiac action potential:
in phase 3, the membrane potential gradually falls to more negative values when a second set of … that began opening in phases 1 and 2 allows significant amounts of … to flow out of the cell. the falling membrane potential causes … to close, reducing the flow of calcium into the cell and repolarizing the membrane until the resting potential is reached.
potassium channels;
potassium;
calcium channels
There are five main phases of membrane polarization in a cardiac action potential:
in phase 4, the … is again established in cardiac muscle cells and is maintained until the next depolarization arrives from neighboring cardiac … cells
the total cardiac action potential lasts …-… ms
resting membrane potential;
pacemaker;
250-300
recall that … occurs when a skeletal muscle is stimulated with such frequency that muscle twitches overlap and result in a stronger contraction than a single muscle twitch. when the stimulations are frequent enough, the muscle reaches a state of …, during which the individual muscle twitches cannot be distinguished
wave summation;
fused tetanus
tetanus occurs in skeletal muscle because skeletal muscle has a relatively short … - a period during which action potentials cannot be generated no matter how strong the stimulus
absolute refractory period
unlike skeletal muscle, cardiac muscle has a relatively … refractory period and is thus incapable of … In fact, cardiac muscle is incapable of reacting to any stimulus before approximately the middle of phase … and will not respond to a normal cardiac stimulus before phase …
long;
wave summation;
3;
4
the period of time between the beginning of the cardiac action potential and the approximate middle of phase 3 is the …
the period of time between the absolute refractory period and phase 4 is the …
absolute refractory period;
relative refractory period
the total refractory period of cardiac muscle is …-… milliseconds - almost as long as the contraction of the cardiac muscle
200; 250
phase 2 of the cardiac action potential, when the calcium channels remain open and potassium channels are closed, is called the …
plateau phase
which of the following is true of the cardiac action potential? the cardiac action potential is … than the skeletal muscle action potential
longer
the main anatomical difference between the frog heart and the human heart is that the frog heart has a …
single, fused ventricle
which of the following statements about the contractile activity is true?
the smaller waves represent the …
contraction of the atria
during which portion of the cardiac muscle contraction is it possible to induce an extrasystole?
during …
relaxation
the amplitude of the ventricular systole did not change with the more frequent stimulation because a new contraction could not begin until the …
relaxation phase
which of the following do you think contribute to the inability of cardiac muscle to be tetanized? the … of the cardiac action potential
long refractory period
given the function of the heart, why is it important that cardiac muscle cannot reach tetanus? the ventricles must … and … with each beat to pump blood
contract; relax fully
an extrasystole corresponds to an extra …
ventricular contraction
at rest both the sympathetic and parasympathetic NS are working but the … branch is more active
parasympathetic
stimulation of the sympathetic nervous system increases the … and … of contraction of the heart
rate; force
stimulation of the the parasympathetic nervous system … the heart rate without directly changing the force of contraction. the … nerve (cranial nerve …) carries the signal to the heart.
decreases; vagus; X;
if stimulation of the vagus nerve (…) is excessive, the heart will …
vagal stimulation;
stop beating
A short time after the heart stops beating due to excessive vagal stimulation, the ventricles will begin to beat again. the resumption of the heartbeat is referred to as … and can be the result of … or initiation of a rhythm by the …
vagal escape;
sympathetic reflexes;
Purkinje fibers
the … is a cluster of autorhythmic cardiac cells found in the right atrial wall in the human heart. it has the fastest rate of spontaneous depolarization, and for that reason, it determines the heart rate and is therefore referred to as the heart’s ….
sinoatrial node (SA node); pacemaker
in the absence of parasympathetic stimulation, sympathetic stimulation, and hormonal controls, the SA node generates action potentials … times per min
100
the branch of the autonomic nervous system that dominates during exercise is the …
sympathetic branch
vagal escape probably involves …
sympathetic reflexes
humans are …, which means that the human body maintains an internal body temp within the 35.8-38.2 degrees C range even though the external temp is changing
homeothermic
when the external temperature is elevated, the hypothalamus is signaled to activate … mechanisms, such as … and …, to maintain the body’s internal temperature
heat-releasing;
sweating; vasodilation
during extreme external temperature conditions, the body might not be able to maintain homeostasis and either … (elevated body temperature) or … (low body temperature) could result
hyperthermia; hypothermia
the frog is a .. animal. its internal body temp changes depending on the temp of its external enviro bc it lacks internal homeostatic regulatory mechanisms
poikilothermic
ringer’s solution, aka …, consists of essential electrolytes (…, …, …., …, and ….) in a physiological solution and is required to keep the isolated, intact heart viable
ringer's irrigation; chloride; sodium; potassium; calcium; magnesium
the electrolytes in a ringer’s solution are required to provide for
autorhymicity
the general name for the process that maintains the internal body temperature in humans is …
homeostasis
what effect do you think a fever of 104 degrees F would have on heart rate? … in heart rate
increase