6.3 Stress & Caffeine*

Adrenaline triggers a sympathetic response by increasing heart rate in response to stress. When the body perceives a stressful situation, the adrenal glands release adrenaline into the bloodstream. Adrenaline then binds to specific receptors on the heart, causing it to beat faster and stronger. This increased heart rate is part of the body's fight-or-flight response, preparing it to either confront the stressor or escape from it. By increasing heart rate, adrenaline ensures that the body receives more oxygen and nutrients to meet the increased demands during times of stress.

Adenosine is a molecule that accumulates in the brain as we use energy. It acts as a neurotransmitter and binds to specific receptors, causing drowsiness and promoting sleep. Therefore, as adenosine builds up, it signals to the brain that it needs rest and makes us feel tired. This explains why we feel more fatigued after a long day of physical or mental activity.

This person probably has high levels of cortisol. Cortisol is a hormone released by the adrenal glands in response to stress. High levels of cortisol can indicate chronic stress, anxiety, or an overactive adrenal gland. It can lead to symptoms such as weight gain, high blood pressure, and impaired immune function.

Caffeine blocks the receptors for adenosine. Adenosine is a hormone that promotes relaxation and drowsiness. By blocking its receptors, caffeine prevents adenosine from binding and exerting its effects, leading to increased alertness and reduced fatigue. This is why caffeine is commonly consumed to stay awake and improve focus.

Caffeine blocks adenosine from being received in the brain. Adenosine is a neurotransmitter that promotes sleep and relaxation. When caffeine is consumed, it binds to the adenosine receptors in the brain, preventing adenosine from binding to these receptors. As a result, the person feels more alert and awake.

When a person is under too much stress, their body does not have enough time to heal, rest, and digest. Stress activates the body's fight-or-flight response, which diverts resources away from these essential functions. Instead, the body focuses on immediate survival, such as increasing heart rate and blood pressure. This prolonged state of stress can lead to various health problems, including weakened immune system, digestive issues, and increased risk of chronic diseases. Therefore, it is important to manage stress levels and allow the body time to recover and perform these vital functions.

Adenosine is a molecule that is produced in the body as a byproduct of energy consumption. As we use energy, adenosine gradually accumulates in our system. This build-up of adenosine acts as a signal to the body that it needs to rest and recover. Therefore, the statement "adenosine builds up as we use energy" is true.

Cortisol is a hormone released in response to stress. It helps the body by providing extra energy to deal with the stressor. This energy boost allows the body to respond effectively to the stress, whether it's by fighting, fleeing, or taking necessary action. By increasing blood sugar levels and suppressing non-essential functions, cortisol helps the body stay alert and focused during stressful situations. Therefore, it can be said that cortisol triggered by stress is helpful because it gives the body the energy it needs to respond to the stressor.

Caffeine is a stimulant that blocks the receptors in the brain that receive adenosine, a neurotransmitter responsible for promoting sleep and relaxation. When these receptors are blocked, the brain does not receive the signal that it is tired, leading to a feeling of wakefulness and alertness. Therefore, the correct answer is that caffeine blocks the brain from receiving adenosine, making the person not tired.