You experience a rapid increase in heart rate your musecles tense, and your breathing becomes shallow These changes in your physiology are most likely mediated by

Options

A. Neurotransmitters
B. Hormones
C. Target cells
D. Receptors

Answer

To solve the question regarding the physiological changes you experience, let's break it down step by step:

### Step-by-Step Solution:

1. **Identify the Physiological Changes**: The question states that there is a rapid increase in heart rate, muscle tension, and shallow breathing. These changes are typically associated with a stress response or a fight-or-flight reaction.

2. **Understand the Mechanism**: These physiological responses are primarily controlled by the autonomic nervous system, particularly the sympathetic division, which prepares the body for rapid action in stressful situations.

3. **Consider the Options**:
- **Neurotransmitters**: These are chemical messengers that transmit signals between nerve cells. They play a significant role in regulating heart rate and muscle tension.
- **Hormones**: These are also chemical messengers but are secreted by endocrine glands and can have longer-lasting effects on various body functions.
- **Target Cells**: These are not a mediator; they are the cells that respond to signals from neurotransmitters or hormones.
- **Receptors**: These are proteins on target cells that receive signals but do not mediate the changes themselves.

4. **Determine the Most Likely Mediator**: Given that the question describes immediate physiological changes (like increased heart rate and muscle tension), the most likely mediator is neurotransmitters. They act quickly to transmit signals in response to stress.

5. **Conclusion**: The physiological changes described in the question are most likely mediated by neurotransmitters, as they facilitate rapid communication between nerve cells and target organs such as the heart and muscles.

### Final Answer:
The physiological changes are most likely mediated by **neurotransmitters**.

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