Problem 113 - Objective Biology for NEET

Question

Heartbeat is accelerated by (a) Sympathetic nerves and acetylcholine (b) Cranial nerves and adrenaline (c) Cranial nerves and acetylcholine (d) Sympathetic nerves and epinephrine

Step-by-Step Solution

Answer

The correct answer is (d) Sympathetic nerves and epinephrine.

Step 1: Analyzing the options

First consider the role of sympathetic and cranial nerves, along with the effects of acetylcholine, adrenaline, and epinephrine. This allows for the pooling of options that result in an acceleration of heartbeat.

Step 2: Selection of correct answer

Recall that the sympathetic nerves and epinephrine are both known to accelerate the heartbeat. Therefore, find the option where these two are paired together, which is option (d).

Key Concepts

Sympathetic Nervous System

The sympathetic nervous system (SNS) is a key part of the autonomic nervous system, which is the system in your body that controls involuntary actions, like heartbeat and digestion. The SNS is known as the "fight or flight" system because it kicks in during stressful situations or when you need extra energy. During these times, the SNS triggers several responses to help you either fight the threat or run away.

When the SNS is activated, it releases neurotransmitters that accelerate the heartbeat. This increase in heart rate ensures that your muscles and brain receive the oxygen needed to handle the situation at hand. In addition to increasing the heart rate, the SNS also widens (dilates) the pupils, inhibits unnecessary digestive activity, and redirects blood flow toward vital organs and muscles.

Overall, the SNS plays a crucial role in regulating how your body responds to challenges, by making adjustments to ensure peak efficiency during demanding scenarios.

Heart Rate Regulation

Heart rate regulation is the process by which the body adjusts the speed of the heartbeat according to the body's needs. It ensures that the circulatory system is supplying adequate oxygen-rich blood to all tissues.

The heart receives signals from both the sympathetic and parasympathetic nervous systems, which act as regulators. The sympathetic system increases heart rate, gearing your body up for more activity, while the parasympathetic system slows it down, helping to conserve energy during restful periods. Another important element of heart rate regulation is the presence of receptors on the heart, known as beta receptors. These interact with certain chemicals like hormones to control the pace of the heartbeat.

A balance between these systems is vital for maintaining cardiovascular health, as it allows the heart to adequately respond to physical demands without undue stress.

Epinephrine

Epinephrine, also known as adrenaline, is a hormone and neurotransmitter produced by the adrenal glands, located on top of the kidneys. It plays an essential role in the body's response to stress, often referred to as the "adrenaline rush."

This hormone is rapidly released into the bloodstream during stressful situations, leading to physiological changes such as increased heart rate, increased blood pressure, and expanded air passages in the lungs. These changes prepare the body for quick physical action and better aerobic performance, critical attributes in fight-or-flight situations.

Epinephrine also boosts the breakdown of glycogen to glucose, thus providing a quick energy source and further contributing to increased physical readiness. In summary, epinephrine is central to the body's ability to prepare itself rapidly for high-stress or high-energy activities.