Problem 170 - Objective Biology for NEET

Question

Assertion: Human heart is myogenic. Reason: Normal activities of heart are regulated intrinsically by specialized muscle.

Step-by-Step Solution

Answer

Yes, the assertion and reason are correct. The human heart is myogenic because its regular activity is intrinsically regulated by specialized muscle tissue.

Step 1: Understanding The Terms

Understand the assertion and the reason given. In this case, a Myogenic heart is a heart that originates from the muscle tissue (hence the term myocardium), which is able to rhythmically contract and relax without receiving any external electrical signal. Intrinsic regulation means that the regulation of activity originates from within the organ or system.

Step 2: Identifying the Relationship

Identify how the assertion and reason are related. Here, the fact that a myogenic heart is regulated by specialized muscle cells means that the pace or rhythm of the heart's contractions are determined from within the heart itself, i.e. intrinsically.

Step 3: Forming the Conclusion

Drawing the link between the two statements, it can be concluded that the reason - heart's activities being regulated intrinsically, supports the assertion that human heart is myogenic. Since human heart's rhythmic activity is controlled by specialized muscular tissue within the heart, it demonstrates its myogenic characteristic.

Key Concepts

Myogenic Heart

The human heart is fascinating because it works without any external cues to initiate its beating. This automatic function is described as myogenic, which means originating within the muscle tissue itself (from the Greek word 'myo' meaning muscle and 'genic' meaning produced by or from). The heart muscle, known as the myocardium, possesses the remarkable ability to generate its own electrical impulses. This unique property ensures the heart continues to beat rhythmically, even without direct signals from the brain or nervous system.
This self-initiated contraction of the heart muscle means that it can sustain a steady heartbeat. If you were to isolate the heart from the body, it would still continue to beat, driven by its intrinsic mechanisms. By generating electrical signals on its own, the heart stands as a guardian of life, controlling blood circulation and ensuring that nutrients and oxygen are effectively transported throughout the body.

Intrinsic Regulation

Intrinsic regulation in the heart refers to its self-governing ability to control the heartbeat rhythm without any external intervention. Within the heart, certain cells can spontaneously give rise to electrical impulses. These impulses trigger the muscle cells to contract, creating the heartbeat we rely on.
The term 'intrinsic' signifies that these controlling mechanisms are embedded within the heart itself. This inbuilt system ensures that our heart adapts to differing bodily demands. For example:

• When you exercise, various changes in the body trigger the heart to beat faster.
• When resting, it slows down naturally.

The heart's intrinsic regulation allows it to synchronize its activity with the body's needs without waiting for signals from outside. Thus, no matter what, these self-generated impulses keep the heart working efficiently.

Specialized Muscle Cells

At the core of the heart's ability to self-regulate are specialized muscle cells known as pacemaker cells. These cells are crucial for maintaining the heart's rhythm and function. Found predominantly in the sinoatrial (SA) node of the heart, these cells initiate the generation of electrical impulses.
Pacemaker cells have a distinct property: they can depolarize automatically at a regular pace, leading to the initiation of heartbeats. These electrical pulses then spread through the heart muscle, prompting the entire heart to contract in a coordinated fashion. Key features of these specialized muscle cells include:

• Automaticity: The natural ability to trigger beats without external stimuli.
• Rhythmicity: Consistently producing impulses to maintain a steady rhythm.

These features enable the heart to maintain its pace consistently, orchestrating a perfect harmony without missing a beat. It's thanks to these specialized muscle cells that our heart reliably keeps time on its own.