Problem 16 - Anatomy and Physiology of Animals

Question

Which of the following is an incorrect pairing? a. norepinephrine dilates the pupil b. epinephrine increases blood pressure c. acetylcholine decreases digestion d. norepinephrine increases heart rate

Step-by-Step Solution

Answer

Option c is incorrect; acetylcholine should increase digestion.

Step 1: Identify Pairings

First, identify what is being paired in each option. We need to pair the given neurotransmitter or hormone with its physiological effect: - a. norepinephrine with pupil dilation - b. epinephrine with increased blood pressure - c. acetylcholine with decreased digestion - d. norepinephrine with increased heart rate.

Step 2: Understand Functions of Each Chemical

Recall the physiological role of each neurotransmitter/hormone: - Norepinephrine typically causes pupil dilation and increased heart rate as part of the fight or flight response. - Epinephrine increases blood pressure and also plays a role in the fight or flight response. - Acetylcholine typically stimulates the parasympathetic nervous system, which promotes activities such as digestion.

Step 3: Evaluate Each Pairing

Evaluate each pairing based on the understanding of physiological roles: - a. Norepinephrine does indeed dilate the pupils. - b. Epinephrine does increase blood pressure. - c. Acetylcholine should increase digestion, not decrease it, as it activates the parasympathetic nervous system. - d. Norepinephrine does increase heart rate.

Step 4: Identify the Incorrect Pairing

From our evaluation, pairing c. acetylcholine decreases digestion is incorrect because acetylcholine typically increases digestive activities as part of the parasympathetic response.

Key Concepts

Physiological Effects

Understanding the physiological effects of neurotransmitters is crucial in neurobiology. Neurotransmitters are chemicals that transmit signals across the synapse from one neuron to another `target` neuron, muscle cell, or gland cell.
These transmissions can lead to various changes in the body, affecting organs, muscles, and the nervous system.
For example, some can increase heart rate, while others may calm the body down.

• Norepinephrine and epinephrine are both known to ramp up body functions during stress.
• Acetylcholine generally promotes resting body activities.

Each neurotransmitter has a unique role in maintaining our bodily functions.

Parasympathetic Nervous System

The parasympathetic nervous system is a component of the autonomic nervous system.
It helps to balance the body's systems and conserves energy by slowing down the heart rate and increasing digestive activities.
It promotes the 'rest and digest' functions.

• Acetylcholine is the primary neurotransmitter associated with the parasympathetic nervous system.
• It encourages digestion, salivation, and a reduced heart rate.

Essentially, it brings the body back to a state of calm and recovery after a stress event.

Fight or Flight Response

The fight or flight response is a physiological reaction that occurs in the presence of something terrifying, either mentally or physically.
This response prepares the body to either fight the threat or flee from it.

• This response is mainly driven by hormones like epinephrine and norepinephrine.
• It leads to increased heart rate, pupil dilation, and increased blood flow to muscles.

Such changes are all part of gearing up the body to face threats head-on.

Acetylcholine

Acetylcholine is the neurotransmitter that plays a vital role in triggering the parasympathetic nervous system.
It encourages peace-keeping actions in the body like reducing heart rate and stimulating digestion.

• It helps lower stress levels by calming down bodily functions.
• Hence, it is generally associated with rest and repair processes in the body.

Any disruption in acetylcholine levels can directly affect digestion and heart rate.

Norepinephrine

Norepinephrine is a key player in preparing the body for action.
Often associated with the fight or flight response, it increases heart rate and blood flow to muscles.

• It is crucial for stress responses and heightened alertness.
• It also leads to pupil dilation, allowing more light into the eyes.

Norepinephrine helps keep us alert and ready to respond in the face of danger.

Epinephrine

Epinephrine, also known as adrenaline, is another major hormone involved in the fight or flight response.
It works closely with norepinephrine to increase heart rate, blood pressure, and energy availability.

• It helps quickly prepare the body for rapid, intense activity.
• A spike in epinephrine levels is what causes the sudden rush of energy experienced during stressful situations.

Understanding the role of epinephrine is key to comprehending our body's rapid responses to stress.