Hypertrophy | What is hypertrophy? | Mechanism of muscle hypertrophy | How does hypertrophy happen?

What is Hypertrophy?

Understanding Hypertrophy

• Hypertrophy refers to the increase in the size of cells, leading to an overall increase in the size of an organ. A common example is muscle growth, such as increased bicep size from gym workouts.

• Importantly, hypertrophy does not involve a net increase in cell number; rather, existing cells become larger and stronger.

Types of Hypertrophy

• There are two main types of hypertrophy:

• Physiological Hypertrophy: This occurs due to normal stress or increased demand on muscles (e.g., lifting heavier weights).

• Pathological Hypertrophy: An example includes left ventricular hypertrophy caused by hypertension, where heart muscle thickens and can lead to health issues.

Factors Influencing Physiological Hypertrophy

• Key factors that induce physiological hypertrophy include:

• Increased functional demand (e.g., lifting heavier weights).

• Hormonal stimulation from growth hormones and steroids.

• Malpractice in sports involving hormone injections for enhanced muscle growth.

Chemical and Mechanical Signals

• Various signals can induce hypertrophy:

• Chemical Signals: Insulin-like growth factor (IGF), myostatin, androgens play significant roles.

• Mechanical Signals: Muscle stretching sensed by integrin receptors leads to protein synthesis and muscle enlargement.

Pathological vs. Physiological Examples

Pathological Hypertrophy Explained

• Left ventricular hypertrophy serves as a key example of pathological hypertrophy. The heart's cavity decreases as cardiomyocytes enlarge, reducing blood capacity which is detrimental to health.

Mechanisms Behind Cardiac Hypertrophy

• Several mechanisms contribute to cardiac hypertrophy:

• Growth factors like IGF-1 are crucial for muscle development.

• Agonists such as alpha adrenergic hormones and angiotensin relate to blood pressure regulation.

Biological Responses Induced by Cardiac Changes

• Cardiac changes trigger various biological responses including:

• Synthesis of contractile proteins.

• Activation of specific embryonic genes like alpha actin.

• Replacement of myosin heavy chain isoforms with more energetically efficient variants.

Conclusion on Hypertrophic Processes

Summary Insights

• In summary, hypertrophy involves an increase in cell size without new cell formation. It can be classified into physiological or pathological types with distinct examples provided throughout the discussion.

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