Which statement is true regarding cardiac tissue? This intriguing question delves into the specialized characteristics and functions of cardiac tissue, a unique type of muscle that orchestrates the rhythmic contractions of our hearts. Join us on an enlightening journey as we explore the intricate workings of this vital tissue, unraveling its electrical and contractile properties, regulatory mechanisms, and potential pathologies.
Cardiac tissue stands out from other muscle types due to its remarkable structural and functional adaptations, enabling it to fulfill its crucial role in maintaining a steady heartbeat. Specialized cell types within cardiac tissue, such as cardiomyocytes and pacemaker cells, play distinct roles in electrical conduction and coordinated contractions.
These cells are interconnected by intercalated discs, which facilitate rapid and synchronized electrical impulses, ensuring the efficient and rhythmic pumping action of the heart.
Characteristics of Cardiac Tissue
Cardiac tissue is a specialized muscle tissue that forms the heart. It has unique structural and functional features that distinguish it from other muscle types, including:
- Striated appearance:Cardiac tissue is made up of elongated cells called cardiomyocytes that are arranged in parallel rows, giving it a striated appearance under a microscope.
- Branched cells:Cardiomyocytes are branched, allowing them to connect to multiple neighboring cells.
- Intercalated discs:Cardiomyocytes are connected by specialized structures called intercalated discs, which allow for the rapid and coordinated spread of electrical impulses and mechanical forces throughout the heart.
Specialized Cell Types
Cardiac tissue contains three specialized cell types:
- Contractile cardiomyocytes:These cells are responsible for the contraction of the heart.
- Conducting cardiomyocytes:These cells are responsible for the electrical conduction of impulses through the heart.
- Secretory cardiomyocytes:These cells secrete hormones that regulate heart function.
Electrical Properties of Cardiac Tissue
Cardiac tissue has unique electrical properties that enable it to function as a pump.
Resting Membrane Potential
Cardiac cells have a resting membrane potential of about -85 mV. This is due to the high concentration of potassium ions inside the cells and the low concentration of sodium ions outside the cells.
Action Potential
When a cardiac cell is stimulated, it undergoes an action potential. The action potential of cardiac cells is characterized by:
- A long plateau phase, which allows for sustained contraction.
- A refractory period, which prevents the cell from being re-excited too quickly.
Refractory Period
The refractory period is the period of time after an action potential during which a cell cannot be re-excited. This is important for preventing arrhythmias.
Contractile Properties of Cardiac Tissue: Which Statement Is True Regarding Cardiac Tissue
Cardiac tissue has unique contractile properties that enable it to pump blood throughout the body.
Molecular Basis of Muscle Contraction
Muscle contraction in cardiac tissue is based on the sliding filament theory. This theory states that muscle contraction occurs when the thin filaments (actin) slide over the thick filaments (myosin) in a ratchet-like manner.
Frank-Starling Mechanism
The Frank-Starling mechanism is a phenomenon in which the force of contraction of cardiac tissue increases as the volume of blood in the heart increases. This mechanism helps to ensure that the heart can pump more blood when the body needs it.
Factors Influencing Cardiac Contractions
The force and duration of cardiac contractions are influenced by a number of factors, including:
- Heart rate
- Preload (the amount of blood in the heart before it contracts)
- Afterload (the amount of pressure against which the heart must pump)
- Contractility (the inherent ability of the heart to contract)
Regulation of Cardiac Tissue
Cardiac tissue is regulated by a number of mechanisms, including:
Autonomic Nervous System
The autonomic nervous system regulates heart rate and contractility. The sympathetic nervous system increases heart rate and contractility, while the parasympathetic nervous system decreases heart rate and contractility.
Hormonal Regulation
A number of hormones regulate cardiac tissue, including catecholamines, thyroid hormones, and steroids. Catecholamines increase heart rate and contractility, while thyroid hormones increase the metabolic rate of cardiac tissue.
Intrinsic Mechanisms
Cardiac tissue also has a number of intrinsic mechanisms that regulate its activity, including the Bainbridge reflex and the Bezold-Jarisch reflex.
Pathology of Cardiac Tissue
Cardiac tissue can be damaged by a number of diseases and conditions, including:
Myocardial Infarction
Myocardial infarction is a heart attack. It occurs when blood flow to a part of the heart is blocked, causing damage to the cardiac tissue.
Cardiomyopathies
Cardiomyopathies are diseases of the heart muscle. They can be caused by a variety of factors, including genetic defects, infections, and toxins.
Cardiac Arrhythmias, Which statement is true regarding cardiac tissue
Cardiac arrhythmias are abnormal heart rhythms. They can be caused by a number of factors, including damage to the cardiac tissue, electrolyte imbalances, and hormonal disorders.
Answers to Common Questions
What is the resting membrane potential of cardiac cells?
Around -85 to -95 millivolts, more negative than most other excitable cells.
What is the refractory period in cardiac tissue?
A period after an action potential during which the tissue is less responsive to further stimulation, preventing high-frequency contractions and arrhythmias.
What is the Frank-Starling mechanism?
The ability of the heart to increase its output in response to increased venous return, within physiological limits.
