Problem 167 - Objective Biology for NEET

Question

Assertion: Repeated activation of skeletal muscle can lead to fatigue Reason: Accumulation of lactic acid occur due to anaerobic respiration

Step-by-Step Solution

Answer

Yes, the assertion and reason are connected. The fatigue that results from the repeated activation of skeletal muscle can indeed be attributed to the accumulation of lactic acid, which is a byproduct of the anaerobic respiration taking place in the muscles.

Step 1: Understand the Assertion

The Assertion is: 'Repeated activation of skeletal muscle can lead to fatigue'. Skeletal muscle is responsible for voluntary movements. When skeletal muscles are continually activated, such as during exercise, they can become fatigued and less able to contracts. This fatigue can cause a feeling of exhaustion or weariness.

Step 2: Understand the Reason

The Reason is: 'Accumulation of lactic acid occur due to anaerobic respiration'. When muscles are used to their limit, they switch from aerobic respiration to anaerobic respiration to rapidly generate energy. Anaerobic respiration, however, produces lactic acid as a by-product, which can buildup in the muscle cells.

Step 3: Connect the Assertion and Reason

The accumulation of lactic acid in muscle cells due to anaerobic respiration can lead to a decrease in muscle pH, which can interfere with the ability of the muscles to contract, leading to fatigue. Therefore, the fatigue felt with repeated muscle activation can be linked to the accumulation of lactic acid due to anaerobic respiration.

Key Concepts

Skeletal Muscle

Skeletal muscles are the powerhouses of movement in our bodies. They control voluntary movements, allowing us to walk, run, and lift objects. These muscles attach to bones through tendons, creating a strong linkage that aids in movement.

• Function: They work consciously under our control to perform physical activities.
• Structure: Composed of long fibers, these muscles appear striated under a microscope.

A single skeletal muscle fiber can contract repeatedly during activities like exercise. However, this repetitive action can lead to muscle fatigue, especially when the action is intense or prolonged.
Muscle fatigue involves a decline in the muscle's power to generate force. It occurs when the muscles are not able to keep up with the energy demands needed for contraction.

Anaerobic Respiration

When our muscles work harder and faster than oxygen can be delivered to them, they switch from aerobic to anaerobic respiration. This shift is vital for quick energy needs when oxygen levels are low.

• Occurs when there is a lack of oxygen during strenuous activities.
• Works efficiently for a short duration.

Aerobic respiration is the normal way muscles generate energy by breaking down glucose with oxygen. However, in situations like sprinting, anaerobic respiration takes over to supply rapid energy.
This type of respiration breaks down glucose without oxygen and yields energy quickly, but it's less efficient and can't be sustained for long compared to its aerobic counterpart.

Lactic Acid Buildup

Lactic acid is a by-product of anaerobic respiration occurring in muscle cells during intense activity. As muscles rely on anaerobic respiration for quick energy bursts, lactic acid accumulates.

• Formation: The transformation of glucose into energy via anaerobic pathways results in lactic acid.
• Effect: Increased lactic acid lowers pH, making muscles acidic, reducing efficiency.

The buildup of lactic acid in muscle fibers is often associated with a burning sensation and is a key factor in muscle fatigue, hindering proper contractions.
Managing and mitigating lactic acid buildup can involve pacing during exercise, endurance training, and ensuring proper recovery to help muscles efficiently clear lactic acid from their system.