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Cellular Control Systems Test

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Cellular Control Systems Test

Analyze each situation and use evidence from the supplied data. Choose or write the best scientific answer. Total: 27 marks.

Part A — Feedback and homeostasis

A county fair is running a physiology demonstration. Visitors’ body temperature and blood glucose are measured before and after different events.

1.At the fair, Aaliyah’s body temperature rises from 37.0°C to 38.0°C after a sprint. She begins sweating, and her skin blood vessels widen; her temperature then falls toward 37.0°C. Which feedback type is operating, and what feature of the response supports your choice?

2.During a fairground ride, a rider’s heart rate rises. Which description best explains how the sinoatrial (SA) node contributes to controlling the heartbeat?

It initiates electrical impulses that set the rhythm of each heartbeat.
It directly oxygenates the blood inside the heart.
It opens the heart valves by pulling on them.
It makes glucose enter muscle cells.

3.After drinking a sugary lemonade, Madison’s blood glucose rises. The pancreas releases insulin, body cells take up more glucose, and blood glucose falls. Identify the stimulus, control center, effector, and response in this loop.

4.Uterine contractions during childbirth stimulate oxytocin release, which strengthens contractions and leads to further oxytocin release. Is this positive or negative feedback? Explain why this loop does not simply restore a variable to a set point.

Part B — Gene expression and cell-cycle control

A student team at the fair compares gene expression and cell-cycle data from cultured cells. Use the information below to answer the questions.

Cell sample

DNA damage before G1 checkpoint

Observed outcome

Normal control

Detected

Cycle pauses; repair occurs before DNA replication

Checkpoint-defective sample

Detected

Cell enters S phase with damaged DNA and continues dividing

5.Put these cell-cycle stages in order, beginning just after cell division: G2, M phase, S phase, G1. State the key event that occurs during S phase.

6.Based on the checkpoint observations, explain how checkpoint failure can increase the risk of cancer. Include what happens to damaged DNA and why repeated cell division matters.

7.Select every component that commonly belongs in a physiological feedback loop.

Stimulus or change in a regulated variable
Receptor or sensor
Control center or integrator
Effector
Mitochondrion in every loop

8.A mutation changes one DNA base in a gene. Explain the usual flow of information from that gene to a protein, and describe one way the mutation could affect the protein.

Part C — Apply and evaluate

Use the evidence and concepts from the whole test to make precise scientific explanations.

9.A fair volunteer says, “Every feedback loop brings a body condition back to normal.” Is this statement accurate? Give one counterexample and explain the difference between that loop and a homeostatic negative feedback loop.

10.Draw a negative feedback loop for a rise in body temperature. Include the stimulus, receptor, control center, at least one effector, and the response. Add arrows to show the direction of information and the response.

11.Complete the cardiac conduction pathway and state the result of the final step: SA node → node → Bundle of His → Purkinje fibers → .