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sinoatrial node
A pacemaker is nothing but a specialized mass of muscle tissue present in the wall of the heart. It initiates the heart beat.
There are three types of tissue that make up the heart which are collectively known as cardiac tissue. These three tissues are myocardium, endocardiu, and pericardium.
The heart is comprised of specialized cardiac muscle fibers.
The sinoatrial node is impulse generating tissue in the (R) atrium of the heart. It is the natural pacemaker of the heart.
Adrenaline accelerates the rate of the heart beat by acting to excite the sinoatrial primary pacemaker of the heart.
Heart has cardiac tissue. It is striated like skeletal muscle, but is under control of the autonomic nervous system.
Buchman's Bundle
The heart is made of muscle, connective, epithelium, and nervous tissue.
The endocardiumconsists of epithelium and connective tissue that contains many elastic and collagenousfibers. It also contains blood vessels and some specialized cardiac muscle fibers called purkinjefibers.
It ia a specialized bit of heart tissue that controls the heartbeat.
The sinoatrial node is considered the pacemaker of the heart.