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+20 A Membrane -20 potential (mV) -40 Threshold -60 -80 0.8 1.6 Time (s) AV node threshold voltage-gated calcium channels SA node stable leaky voltage-gated potassium channels gap junctions calcium The heart beat is initiated by a patch of specialized cardiocytes called the These cells are unique because they lack a resting membrane potential. Instead, at arrow A, the membrane potential is increasing because there are sodium channels allowing the cardiocytes to slowly accumulate positive charges. The horizontal dashed line at -40mV is called When the membrane potential reaches -40mV open, resulting in an action potential (arrow B). The channels also serve to stimulate sarcomere contraction in the cardiocytes. Neighboring cells are also stimulated as the ions spread through atrial cells through .At about + 10mv, those channels close, and open. This causes the caridocytes to lose positive charges (arrow C), and repolarize. These channels close at -60mV (the resting membrane potential). The SA node cardiocytes do not stay at the resting membrane potential for long, however, as they repeat the slow depolarization at arrow A, beginning another cycle.

+20 A Membrane -20 potential (mV) -40 Threshold -60 -80 0.8 1.6 Time (s) AV node threshold voltage-gated calcium channels SA node stable leaky voltage-gated potassium channels gap junctions calcium The heart beat is initiated by a patch of specialized cardiocytes called the These cells are unique because they lack a resting membrane potential. Instead, at arrow A, the membrane potential is increasing because there are sodium channels allowing the cardiocytes to slowly accumulate positive charges. The horizontal dashed line at -40mV is called When the membrane potential reaches -40mV open, resulting in an action potential (arrow B). The channels also serve to stimulate sarcomere contraction in the cardiocytes. Neighboring cells are also stimulated as the ions spread through atrial cells through .At about + 10mv, those channels close, and open. This causes the caridocytes to lose positive charges (arrow C), and repolarize. These channels close at -60mV (the resting membrane potential). The SA node cardiocytes do not stay at the resting membrane potential for long, however, as they repeat the slow depolarization at arrow A, beginning another cycle.

Human Anatomy & Physiology (11th Edition)
Human Anatomy & Physiology (11th Edition)
11th Edition
ISBN:9780134580999
Author:Elaine N. Marieb, Katja N. Hoehn
Publisher:Elaine N. Marieb, Katja N. Hoehn
Chapter1: The Human Body: An Orientation
Section: Chapter Questions
Problem 1RQ: The correct sequence of levels forming the structural hierarchy is A. (a) organ, organ system,...
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+20 A Membrane -20 potential (mV) -40 Threshold -60 -80 0.8 1.6 Time (s) AV node threshold voltage-gated calcium channels SA node stable leaky voltage-gated potassium channels gap junctions calcium The heart beat is initiated by a patch of specialized cardiocytes called the These cells are unique because they lack a resting membrane potential. Instead, at arrow A, the membrane potential is increasing because there are sodium channels allowing the cardiocytes to slowly accumulate positive charges. The horizontal dashed line at -40mV is called When the membrane potential reaches -40mv open, resulting in an action potential (arrow B). The channels also serve to stimulate sarcomere contraction in the cardiocytes. Neighboring cells are also stimulated as the ions spread through atrial cells through . At about + 10mv, those channels close, and open. This causes the caridocytes to lose positive charges (arrow C), and repolarize. These channels close at -60mV (the resting membrane potential). The SA node cardiocytes do not stay at the resting membrane potential for long, however, as they repeat the slow depolarization at arrow A, beginning another cycle.
Transcribed Image Text:+20 A Membrane -20 potential (mV) -40 Threshold -60 -80 0.8 1.6 Time (s) AV node threshold voltage-gated calcium channels SA node stable leaky voltage-gated potassium channels gap junctions calcium The heart beat is initiated by a patch of specialized cardiocytes called the These cells are unique because they lack a resting membrane potential. Instead, at arrow A, the membrane potential is increasing because there are sodium channels allowing the cardiocytes to slowly accumulate positive charges. The horizontal dashed line at -40mV is called When the membrane potential reaches -40mv open, resulting in an action potential (arrow B). The channels also serve to stimulate sarcomere contraction in the cardiocytes. Neighboring cells are also stimulated as the ions spread through atrial cells through . At about + 10mv, those channels close, and open. This causes the caridocytes to lose positive charges (arrow C), and repolarize. These channels close at -60mV (the resting membrane potential). The SA node cardiocytes do not stay at the resting membrane potential for long, however, as they repeat the slow depolarization at arrow A, beginning another cycle.
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