Which ONE of the following statements is TRUE? OA Cardiac myocyte contraction results primarily from an increased concentration of intracellular Na OB Prazosin is an agonist at a2 adrenergic receptors OC Veins can accommodate large volumes of blood but this causes a large increase in pressure OD The pulse pressure is the addition of systolic and diastolic pressure OE The primary integrating centre for baroreceptor refleves is the medullary cardiovascula

Which ONE of the following statements is TRUE? OA Cardiac myocyte contraction results primarily from an increased concentration of intracellular Na OB Prazosin is an agonist at a2 adrenergic receptors OC Veins can accommodate large volumes of blood but this causes a large increase in pressure OD The pulse pressure is the addition of systolic and diastolic pressure OE The primary integrating centre for baroreceptor refleves is the medullary cardiovascula

Human Physiology: From Cells to Systems (MindTap Course List)

9th Edition

ISBN:9781285866932

Author:Lauralee Sherwood

Publisher:Lauralee Sherwood

Chapter9: Cardiac Physiology

Section: Chapter Questions

Problem 1TAHL

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A person eats a plan that is an agonist to adrenergic receptors on contractile myocardial cells. Which of the following is NOT likely to happen if the adrenergic receptors on this persons conctractile myocardial cells get blocked. Contractile myocardial cells will depolarize more slowly slower uptake od Ca2+ by Ca2+ ATPase from sarcomeres less Ca2+ released from sarcoplasmic reticula following action potentials voltage gated Ca2+ channels get held open longer
The force of contraction can be changed by: can choose more than on e Group of answer choices - muscarinic ACh receptors. Activation of the receptors leads to decreased Ca2+ entry and increased K+ entry in ventricles. - Beta2 adrenergic receptors. Increasing cAMP leads to increases in PKA, which increases sarcoplasmic calcium by opening VG Ca+ channels for a longer time, opening SR Ca2+ channels, and increasing the rate of Ca2+ removed by SERCA pumps. - Beta1 adrenergic receptors. Increasing cAMP leads to increases in PKA, which increases sarcoplasmic calcium by opening VG Ca+ channels for a longer time, opening SR Ca2+ channels, and increasing the rate of Ca2+ removed by SERCA pumps. - Not by the parasympathetic NS. (at least, not the ventricles).
The heart cannot increase its contraction strength via recruitment because: Gap junctions allow free movement of ions between cells Cardiac action potentials are prolonged The cardiac muscle cell is in its refractory period O Plenty of calcium ions are released to allow full crossbridging during each contraction Heart muscle is always at optimum length
After exercising many of you saw an INCREASE in the amplitude of the pulse transducer suggesting vasodilation in the musculature AND an increase in heart rate. Which of the following combinations or regulatory factors explains this curious (but common) combination of physiological responses. Sympathetic NS increases vasodilation and increases heart rate Parasympathetic NS increases vasodilation and increases heart rate Parasympathetic NS increases vasodilation and sympathetic NS increases heart rate Local paracrine factors increase vasodilation and Frank-Starling effect increases heart rate Local paracrine factors increase vasodilation and Sympathetic NS increases heart rate
isovolumetric contraction isovolumetric relaxation ventricular filling ventricular ejection closed rises S1 drops depolarize S2 The first phase of the cardiac cycle is . This is when a lot of blood is in the atria, which causes atrial pressure to be higher than the ventricles. The atrioventricular valves open, and blood moves from the atria to the ventricles. At the end of this phase, the atria contract to maintain pressure and blood flow into the ventricles. As blood leaves the atria, the pressure in the atria As blood enters the ventricles, the pressure in the ventricles Towards the end of this phase, the pressure in the ventricles will exceed the pressure in the atria. At this point, the heart enters the second phase of the cardiac cycle: At this point, the AV valves shut, and we hear . The atria repolarize and the ventricles (due to the QRS complex of the ECG), causing ventricular contraction. Although contracting, it is not yet moving blood into the arteries. All 4 heart valves…
Caffeine lowers the heart rate by increasing rates of depolarization at the SA node True False Nicotine raises the heart rate because it stimulates the activity of the sympathetic neurons in medulla oblongata True False The Frank-Starling Law of the Heart states that the force of heart contraction is directly proportional to the initial length of the muscle fiber, within optimal limits of length True False If the sarcomeres stretched beyond the optimal length, the force of contraction would go down, but that can potentially happen only during open heart surgery when the heart is not constrained by the pericardium, lungs, ribs and diaphragm. True False It is the Na+ channel-driven spontaneous depolarization that is affected by sympathetic and parasympathetic inputs to speed up or slow down the firing rate of the SA node and other conductive cells. True False
Which of these conditions occurs in the repolarization phase of an action potential in pacemaker cells? A voltage-gated Ca2+ ion channels are open B voltage-gated K+ ion channels are open C voltage-gated Na+ ion channels are open D all of these
Cardiac pacemaker cells fıre an action potential similar to neurons. The influx of what ion is responsible for the prolonged depolarization after threshold has been reached in a cardiac muscle fiber? O C- O K+ O Mg+ O Ca 2+
Autorhythmic cells in the SA node intrinsically fire at a rate of - 90 action potentials per minute. During exercise, the heart ráte is increased primarily through modulation by: Increased sympathetic input and parasympathetic input Decreased sympathetic input and parasympathetic input The AV node O Decreased sympathetic input and increased parasympathetic input Increased sympathetic input and decreased parasympathetic input O O O OO
voltage-gated calcium channels voltage-gated sodium channels voltage-gated potassium channels stable not stable Unlike SA node cardiocytes, regular cardiocytes have a resting membrane potential that is Regular cardiocytes become stimulated when calcium and sodium pass from neighboring excited cardiocytes through gap junctions (see 1). This causes to open, resulting in the regular cardiocytes to sharply depolarize (see 2). At 3, these channels close, and open, resulting in both depolarization and sarcomere contraction. Also at 3, open, causing the cell to repolarize. The opposing forces, (depolarization and repolarization) of the two channels that are open simultaneously, results in a plateau (see 4). This plateau continues until voltage-gated calcium channels close. At 5, only remains open, resulting in the cell repolarizing.
In a cardiac auto-rhythmic cell what is the mechanism involved in the change in membrane potential Depolarization: Pna increases, Peak: Na channels close, Plateau: Calcium channels open & Potassium channels close, Repolarization Potassium flows in & Calcium flows out Depolarization: Pna increases, Peak: Na channels close, Plateau: Calcium channels close & Potassium channels open, Repolarization Potassium flows out & Calcium flows in Pacemaker: K+ and Na+ flow, Depolarization: Pca rises Repolarization: Pk rises, 4. If channels close Pacemaker: K+ and Na+ flow, Depolarization: Pca rises Repolarization: Pk rises Depolarization: P wave Repolarization: QRS Complex, Hyperpolarization: T wave O O
Describe the main theories for the termination of calcium sparks in the cardiac muscle excitation contraction-coupling process