School of Nursing Bioscience 1 (401002) Report: Heart & Vitamin B12

This report, prepared for a Bioscience 1 course, examines two key topics: the cardiac conduction system and Vitamin B12. The first section details the components of the heart's conduction pathway, including the sinoatrial node, atrioventricular node, bundle of His, bundle branches, and Purkinje fibers, explaining their roles in generating and transmitting electrical signals to coordinate heart contractions. It also discusses the normal heart rate and the influence of age. The second section focuses on Vitamin B12, including its food sources (beef, liver, chicken, eggs, milk, yogurt, and cheese), its functions in the body (red blood cell production, nervous system and brain function, DNA regulation, and metabolism), and the consequences of its deficiency, such as birth defects in pregnant women (neural tube defects, spontaneous abortions, and preterm delivery) and anemia and fatigue in non-pregnant individuals. The report also identifies vegans as a group at risk for B12 deficiency. The report concludes with a list of cited references.

Running head: BIOSCIENCE 1
BIOSCIENCE
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BIOSCIENCE 2
Components and conduction pathway of the cardiac conduction system of the heart
and how it’s related to contraction of the heart chambers
Atrioventricular node, otherwise abbreviated as AVN, the Sino atrial node abbreviated as
SA, purkinje fibers, the bundles of His and finally the left and right bundle branches, together
constituted what is known as the conduction pathway system of the heart.
An electrical signal is normally generated by the sinoatrial node which is small mass that
is found in the upper chamber of the heart. In a normal heart, it is the Sino arterial node that
serves as the natural pacemaker of the heart. These nodal cells normally manifest in a
spontaneous manner thus depolarizing the heart and creating a normal heart rhythm.
Furthermore, it is documented that the cardiac depolarization produced by the SA is well
modulated by both the sympathetic and the parasympathetic efferent innervation. According to
studies, the Sino atrial node produce the electrical stimulus on a regular basis between 60 and
100 times each minute under normal circumstances (Kennedy et al., 2016). This in return
activates the atria. The stimulus then travels through the conduction system and this makes it
possible for the left ventricles of the heart to pump out blood to other parts of the body.
Normally, they are the upper atria that are stimulated first and they contract for a very short
period of time before the ventricles contract.
The generated electrical signal from the SA moves to the AV node. In the AV node, the
impulse slow down for a moment before progressing down the conduction pathway through the
bundle of His, down via bundle branches through the purkinje fibers causing contraction in the
left ventricles. Study indicate that at a normal pace or rest, the heart is able to contract between
60 and 100 times as the electrical impulse travels through the heart (Van Weerd & Christoffels,
2016). However, the difference in the rate of contraction according to a recent study, results

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indicate that it depends on an age of an individual with statistics indicating that it would be low
in aged individuals and relatively high in young and energetic individuals. Furthermore, the
results show that each single contraction of the ventricles is equivalent to a single heartbeat. One
interesting fact about the conduction system is that the atria normally contract in a fraction of a
second before the ventricles. This makes it possible for the blood to flow into ventricles before
they contract.
Vitamin B12
Food sources
The most common sources of Vitamin B12 beef, liver, and chicken.Others include eggs,
low fat milk, yoghurt and cheese (Smith, Warren, & Refsum, 2018).
Functions of vitamin B12 in the body
It is used in production of Red blood cells and the normal functioning of the nervous
system and the brain (Moll & Davis, 2017). Furthermore, it regulates DNA and facilitates
metabolism in every single cell.
Possible consequences to the body in vitamin B12 deficiency in both pregnant and
non-pregnant individuals
Among pregnant women, deficiency of vitamin B12 leads to birth defects such as the
neural tube defects. Furthermore, it may lead to spontaneous abortions. In some cases, there has
been preterm delivery though further evaluation is to be done (Moll & Davis, 2017). Among
individuals who are not pregnant, vitamin B12 deficiency leads to anemia due to low RBCs and
fatigue due to impaired cellular metabolism.

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Group of people at risk of becoming deficient in vitamin B12 and why
Vegans are those people who feed on vegetables alone and they are at risk since their only
option or source of vitamin B12 is fortified breakfast (Smith, Warren, & Refsum, 2018).
References

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Kennedy, A., Finlay, D. D., Guldenring, D., Bond, R., Moran, K., & McLaughlin, J. (2016).
The Cardiac Conduction System. Critical Care Nursing Clinics of North America,
28(3), 269-279. doi:10.1016/j.cnc.2016.04.001
Moll, R., & Davis, B. (2017). Iron, vitamin B 12 and folate. Medicine, 45(4), 198-203.
doi:10.1016/j.mpmed.2017.01.007
Smith, A. D., Warren, M. J., & Refsum, H. (2018). Vitamin B12. Advances in Food and
Nutrition Research, 215-279. doi:10.1016/bs.afnr.2017.11.005
Van Weerd, J. H., & Christoffels, V. M. (2016). The formation and function of the cardiac
conduction system. Development, 143(2), 197-210. doi:10.1242/dev.124883