To review:
Whether the following statements are true or false. Also, rectify the false statements.
a. The rapid depolarization phase of the contractile cell action potential is due to the opening of voltage-gated potassium ion channels.
b. Pacemaker cells lack a distinct plateau phase.
c. The plateau phase in contractile cells is due to the influx of calcium ions through calcium ion channels.
d. The repolarization of the contractile cell is due to the potassium ions rushing into the cell through potassium ion channels.
e. Open sodium ion channels cause hyperpolarization in pacemaker cells, which triggers the HCN channels to open and begins a new action potential.
Introduction:
The action potentials are generated in the myocardium or the heart muscles due to the opening of Na+ (sodium ion) channels. The Na+ are positively-charged and are present in a lower concentration inside the cells as compared to the outside. When the Na+ channels open, the Na+ rush inside the cells due to the concentration gradient. This makes the inner membrane of the cell temporarily positive. This phase is called the depolarized phase. After a few seconds, the Na+ channels close and the K+ (potassium ion) channels open. The K+ are present in ahigher concentration inside the cells as compared to outside. Hence, the K+ move out of the cells and the inner cell membrane again becomes negative. This stage is called the repolarized state of the cell.
Want to see the full answer?
Check out a sample textbook solutionChapter 17 Solutions
Human Anatomy & Physiology (2nd Edition)
- Which of the following statements about Ca2+ handling in cardiac contractile cells is FALSE? a. One Ca2+ spark is sufficient to cause cross bridge cycling b. When Ca2+ ions flow out of the sarcoplasmic reticulum and into the cytosol, they create a Ca2+ spark c. Ca2+ released from the SR provides ~80% of the Ca2+ needed for muscle contraction d. Summed Ca2+ sparks from different RyR channels create a Ca2+ signal sufficient to cause cross bridge cycling e. Ca2+ sparks can be visualised using biochemical methodsarrow_forwardThe pacemaker cardiac muscle cells rely on ______________ for their action potentials. a. Na+ leak channels and fast voltage-gated Na+ channels b. Ca+2 leak channels and slow voltage-gated Ca+2 channels c. Na+ leak channels and fast voltage-gated Ca+2 channels d. Ca+2 leak channels and fast voltage-gated Ca+2 channelsarrow_forwardSelect the correct one, Which of the following would not increase Cardiac Output? A. increase blood epinephrine concentration B. Increase Atrial Preload C. Increase Cardiac sarcoplasmic calcium concentration D. Increase Arterial Afterloadaarrow_forward
- a calcium channel blocker or an antagonist drug will produce a. vasoconstriction b. increase in blood pressure c. increase in total peripheral resistance d. reduction in cardiac muscle contractilityarrow_forwardIn the image above, the dotted line represents a normal pacemaker potential. Describe the steps involved in a pacemaker potential. What would happen for the pacemaker potential to shift to A? B? A,arrow_forwardAction potentials are spread rapidly between cardiac muscle cells by a. sarcomeres. b. intercalated discs. c. chemical neurotransmitters. d. the fibrous skeleton.arrow_forward
- The ramp potential of pacemaker cells is caused by the opening of the: The ramp potential of pacemaker cells is caused by the opening of the: A. HCN channels B. voltage-gated sodium channels C. voltage-gated calcium channels D. voltage-gated potassium channelsarrow_forwardDescribe why a doctor would give a patient that is diagnosed with acute myocardial infarction the treatment of tissue plasminogen activator(tPA)? What will it do?arrow_forwardAll of the following are correct about the isovolumetric contraction, except ____________. A. This phase of the cardiac cycle begins with the appearance of the QRS complex of the ECG, which represents atrial repolarization and ventricular depolarization B. It represents the time period between the closure of the AV valves and the opening of the aortic and pulmonic valves, ventricular pressure rises rapidly without a change in ventricular volume C. The rate of pressure increase in the ventricles is determined by the rate of contraction of the muscle fibers, which is determine by mechanisms governing excitation-contraction coupling D. Ventricular chamber geometry changes considerably as the heart becomes more spheroid in shape; circumference increases and atrial base-to-apex length increasesarrow_forward
- why are cardiac muscle cells affected by hyperkalemia? A. All choices below are correct B. Resting membrane potential becomes less negative C. Voltage across the cardiac muscle cell cannot be maintained D. The cardiac muscle cell cannot respond to a nerve stimulusarrow_forwardWhich of the following would not increase Cardiac Output? A. increase blood epinephrine concentration B. Increase Atrial Preload C. Increase Cardiac sarcoplasmic calcium concentration D. Increase Arterial Afterloadarrow_forwardUnlike skeletal muscle, cardiac muscle doesn’t undergo tetany. Explain how this is achieved and why is this necessary?arrow_forward
- Human Anatomy & Physiology (11th Edition)BiologyISBN:9780134580999Author:Elaine N. Marieb, Katja N. HoehnPublisher:PEARSONBiology 2eBiologyISBN:9781947172517Author:Matthew Douglas, Jung Choi, Mary Ann ClarkPublisher:OpenStaxAnatomy & PhysiologyBiologyISBN:9781259398629Author:McKinley, Michael P., O'loughlin, Valerie Dean, Bidle, Theresa StouterPublisher:Mcgraw Hill Education,
- Molecular Biology of the Cell (Sixth Edition)BiologyISBN:9780815344322Author:Bruce Alberts, Alexander D. Johnson, Julian Lewis, David Morgan, Martin Raff, Keith Roberts, Peter WalterPublisher:W. W. Norton & CompanyLaboratory Manual For Human Anatomy & PhysiologyBiologyISBN:9781260159363Author:Martin, Terry R., Prentice-craver, CynthiaPublisher:McGraw-Hill Publishing Co.Inquiry Into Life (16th Edition)BiologyISBN:9781260231700Author:Sylvia S. Mader, Michael WindelspechtPublisher:McGraw Hill Education