SSM Heart - Aina Aqilah

BM21110064
SSM Assignment
At the apex of the heart, the AV bundle branches off into a network of myofibers called
Purkinje fibers. They trigger contraction waves through both ventricles simultaneously.
Parasympathetic and sympathetic neural components innervate the heart. For example,
stimulation in parasympathetic division (vagus nerve) will slow our heartbeat whereas
stimulation in sympathetic nerves accelerates the activity of pacemakers. Angina pectoris is a
condition where partially occluded coronary arteries cause oxygen deprivation and make us feel
discomfort.
Other than that, compared to skeletal muscle fibers, cardiac muscle fibers are shorter and
less circular in the transverse section. It also exhibits branching thus giving each cardiac muscle
fiber a “ stair-step” appearance. A typical cardiac muscle fiber is 50–100 μm long with a
diameter of about 14 μm. They usually present with one centrally located nucleus but some
have two nuclei. Cardiac muscle fibers are connected by intercalated discs, an irregular
transverse thickening of the sarcolemma. It contains desmosomes, which holds the fibers
together and gap junction which allows muscle action potentials to conduct between its fibers
and allow the entire myocardium of atria or ventricles to contract as a single unit.
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