University Biology Report: Heart Rate Structure and Function Study

This report provides an overview of heart rate, defining it as the number of heartbeats per minute and its role in ejecting blood. It details the normal heart rate ranges for adults and children. The report explores the functionality of cardiac muscles, emphasizing the collaborative action of the SA node, AV node, Purkinje fibers, and His bundle in the heart's conduction pathway. It explains the mechanism of the heart conduction system, including rapid depolarization, initial repolarization, plateau phase, and complete repolarization, and the role of action potentials. The report also highlights the influence of the SA node, AV node and Purkinje fibers in generating heart contractions, and the control exerted by the parasympathetic and sympathetic nervous systems. References to relevant literature are also included.

Heart rate- Structure and Function
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• The contraction of cardiac muscles
take place due to the generation of
electrical impulse that is known as
action potentials .
• Heart rate is completely dependent
on this action potential generation
and the pacemaker cells such as SA
node, AV node, purkinje fibres and
His bundle. SA node is the natural
pace maker of human body.
• The cells of SA nodes are generally
modified cardiomyocytes and they
are connected to the neighbouring
cells through gap junctions so that
they can depolarize the
cardiomyocytes locally (Sacha,
2014).
• Plateaue phase Is the following phase which
takes place in which membrane potential
slowly falls to -40 mv mainly due to opening of
L-type Ca+2 channels and inward rectifying K+
channels. During the third step inclusive of
repolarization, complete repolarization occurs
due to closing of Ca+2 channels as well as
opening of delayed outward rectifying K+
channels. In the final phase, resting membrane
potential is achieved as the membrane
potential becomes -90 mv (Clark 2015). This
contraction of cardiomyocytes is usually
transferred from one cell to another and
contraction take place. SA nodes can lead to
generation of contraction 100 beats/ min and
this contraction is usually controlled by
parasympathetic and sympathetic nervous
system. AV nodes can generate action potential
at the rate of 40-60 beats/ min and on the
other hand purkinje fibre can produce action
potentials at a rate of 30-40 beats/ min
( Khurana, 2018).
• Heart rate is defined as the number of heart beats per minute for the main purpose of
ejecting blood to the various portion of the body through arteries.
• In a resting condition, the heart rate of normal adults (age more than 10years), ranges
from 60 beats to 100 beats/ minute. In case of highly trained person, this rheart rate
while resting is within the range between 40-60 beats/ min. This normal range of heart
rate differs in case of children. In case of children of 1 to 2 years, this normal heart rate
ranges from 80 to 130 beats/ min. For 3 to 4 years children, this heart rate range is 80 to
120 beats/ min ( Hall , 2015).
• Heart rate is the functionality of cardiac muscles that involves a set of activities and this
function is the collaborative action of SA node (sinoatrial node), AV node (atrioventrical
node), Purkinje fibres and His bundle.
Introduction
The pathway for the heart conduction
causing heartbeat.
• There is rapid depolarisation in
the first step where the voltage
gated calcium channels open in
the cells resulting potential of
cells reaching to +20 mv to +30
mv ( Khurana, 2018). The next
step is followed by initial rapid
repolarization which is due to
closure of fast sodium channels as
well as opening of a few K+
channels ultimately causing
transient outward current
(McDuff, Gontarec & Picard,
2014).
Mechanism of heart
conduction system
References
Clark, A. J. (2015). Comparative physiology of the heart.
Cambridge University Press.
Hall, J. E. (2015). Pocket Companion to Guyton & Hall
Textbook of Medical Physiology E-Book. Elsevier Health
Sciences.
Khurana, I. (2018). Medical physiology for undergraduate
students-E-book. Elsevier Health Sciences.
McDuff, D., Gontarek, S., & Picard, R. (2014, August).
Remote measurement of cognitive stress via heart rate
variability. In 2014 36th Annual International Conference
of the IEEE Engineering in Medicine and Biology Society
(pp. 2957-2960). IEEE.
Sacha, J. (2014). Interaction between heart rate and heart
rate variability. Annals of Noninvasive Electrocardiology,
19(3), 207-216.