cardiac

Examples of cardiac in the following topics:

• Cardiac Cycle

  • The cardiac cycle describes the phases of contraction and relaxation of the heart that drive blood flow throughout the body.
  • The cardiac cycle is the term used to describe the relaxation and contraction that occur as a heart works to pump blood through the body.
  • Heart rate is a term used to describe the frequency of the cardiac cycle.
  • Every single "beat" of the heart includes three major stages: Atrial systole, ventricular systole and complete cardiac diastole.
  • Blood pressure is a regulated variable that is directly related to blood volume, based on cardiac output during the cardiac cycle.

• Types of Muscle Tissue

  • The function of muscles is movement, but the types of movement elicited differ between skeletal, cardiac, and smooth muscle.
  • There are three kinds of muscle tissue: skeletal, smooth, and cardiac.
  • Cardiac muscle is found in the walls of the heart.
  • Although cardiac muscle is involuntary in nature, it is structurally different from smooth muscle.
  • Cardiac muscle is striated, similar to skeletal muscle, but beats involuntarily.

• Microscopic Anatomy

  • Cardiac muscle appears striated due to the presence of sarcomeres, the highly organized basic functional unit of muscle tissue.
  • Cardiac muscle, like skeletal muscle, appears striated due to the organization of muscle tissue into sarcomeres.
  • While similar to skeletal muscle, cardiac muscle is different in a few ways.
  • Cardiac muscles are composed of tubular cardiomyocytes, or, cardiac muscle cells.
  • A sarcomere is the basic unit of muscle tissue in both cardiac and skeletal muscle.

• Mechanism and Contraction Events of Cardiac Muscle Fibers

  • Cardiac muscle fibers undergo coordinated contraction via calcium-induced calcium release, conducted through the intercalated discs.
  • In cardiac, skeletal, and some smooth muscle tissue, contraction occurs through a phenomenon known as excitation contraction coupling (ECC).
  • Similarly to skeletal muscle, the influx of sodium ions causes an initial depolarization, however in cardiac muscle, the influx of calcium ions sustains the depolarization so that it lasts longer.
  • The actual mechanical contraction response in cardiac muscle occurs via the sliding filament model of contraction.
  • Calcium in the cytoplasm then binds to cardiac troponin-C, which moves the troponin complex away from the actin binding site.

• Anatomy of the Heart

  • The heart is a muscular organ responsible for pumping blood through the blood vessels using rhythmic contractions of cardiac muscle.
  • The heart has its own self-sustaining conduction system that sends nervous  impulses to cardiac tissue.
  • The middle layer of the heart is called the myocardium, and contains specialized cardiac muscle tissue responsible for contraction.
  • Cardiac tissue is permanent tissue that does not heal or regenerate when damaged.
  • The position of valves ensures proper directional flow of blood through the cardiac interior.

• Role of the Cardiovascular Center

  • The cardiovascular centre  forms part of the autonomic nervous system and is responsible for regulation of cardiac output.
  • The cardioaccelerator centres stimulate cardiac function by regulating heart rate and stroke volume via sympathetic stimulation from the cardiac accelerator nerve.
  • The cardioinhibitor centres slow cardiac function by decreasing heart rate and stroke volume via parasympathetic stimulation from the vagus nerve.
  • Changes in diameter affect peripheral resistance, pressure, and flow, which affect cardiac output.

• Muscle Tissues and Nervous Tissues

  • There are three types of muscle in animal bodies: smooth, skeletal, and cardiac.
  • Smooth muscle tissue is also called non-striated as it lacks the banded appearance of skeletal and cardiac muscle .
  • Cardiac muscle is found only in the heart.
  • An added feature to cardiac muscle cells is a line that extends along the end of the cell as it abuts the next cardiac cell in the row.
  • Cardiac muscle tissue also has intercalated discs, specialized regions running along the plasma membrane that join adjacent cardiac muscle cells and assist in passing an electrical impulse from cell to cell.

• Blood Pressure

  • The systolic pressure is defined as the peak pressure in the arteries during the cardiac cycle; the diastolic pressure is the lowest pressure at the resting phase of the cardiac cycle.
  • Throughout the cardiac cycle, the blood continues to empty into the arterioles at a relatively even rate.
  • The body regulates blood pressure by changes in response to the cardiac output and stroke volume.
  • Cardiac output is the volume of blood pumped by the heart in one minute.
  • Therefore, cardiac output can be increased by increasing heart rate, as when exercising.

• Structure and Function of the Muscular System

  • Cardiac muscle tissue is found only in the heart where cardiac contractions pump blood throughout the body and maintain blood pressure.
  • As with skeletal muscle cardiac muscle is striated, however it is not consciously controlled and so is involuntary.
  • Cardiac muscle can be further differentiated from skeletal muscle by the presence of intercalated discs which control the synchronized contraction of cardiac tissues.
  • Cardiac myocytes are shorter than skeletal equivalents and contain only one or two centrally located nuclei.
  • Visible striations in skeletal and cardiac muscle are visible, differentiating them from the more randomised appearance of smooth muscle.

• Characteristics of Muscle Tissue

  • The three types of muscle tissue are skeletal, smooth, and cardiac.
  • Cardiac muscle is also an involuntary muscle but is more akin in structure to skeletal muscle, and is found only in the heart.
  • Cardiac and skeletal muscle are both striated in appearance, while smooth muscle is not.
  • Both cardiac and smooth muscle are involuntary while skeletal muscle is voluntary.
  • Differentiate among the structure and location of skeletal, smooth, and cardiac muscles