Biology: The Endocrine System: Hormones and Feedback Loops Worksheet

Question 1

Define the endocrine system and explain how it differs from the nervous system in the way it sends messages through the body.

Accepted Answer

The endocrine system is a group of glands that release hormones into the bloodstream to regulate body functions. It usually sends slower, longer-lasting chemical messages, while the nervous system sends faster electrical and chemical signals through neurons.

Question 2

A diagram shows the hypothalamus, pituitary gland, thyroid gland, adrenal glands, pancreas, ovaries, and testes. Choose three of these glands and describe one hormone each gland produces or helps control.

Accepted Answer

The pituitary gland produces or releases several hormones, such as growth hormone, which helps regulate body growth. The thyroid gland produces thyroxine, which helps regulate metabolism. The pancreas produces insulin, which lowers blood glucose levels by helping cells take in glucose.

Question 3

Explain why hormones are sometimes called chemical messengers.

Accepted Answer

Hormones are called chemical messengers because they are molecules released by endocrine glands that travel through the bloodstream and carry signals to target cells. Target cells respond only if they have the correct receptors for that hormone.

Question 4

Blood glucose rises after a student eats a large meal. Describe the role of insulin in bringing blood glucose back toward normal.

Accepted Answer

After blood glucose rises, the pancreas releases insulin. Insulin causes body cells to take in more glucose and causes the liver and muscles to store glucose as glycogen, which lowers blood glucose back toward the normal range.

Question 5

Blood glucose drops when a person has not eaten for several hours. Describe the role of glucagon in bringing blood glucose back toward normal.

Accepted Answer

When blood glucose drops, the pancreas releases glucagon. Glucagon signals the liver to break down glycogen and release glucose into the blood, which raises blood glucose back toward the normal range.

Question 6

The graph shows blood glucose level over time. At point A, blood glucose rises above normal after a meal. At point B, blood glucose returns to normal. Identify the hormone most responsible for the change from A to B and explain the feedback loop involved.

Accepted Answer

Insulin is the hormone most responsible for the change from A to B. This is a negative feedback loop because the rise in blood glucose triggers insulin release, and insulin reduces blood glucose, reversing the original change.

Question 7

Explain the difference between negative feedback and positive feedback in hormone regulation.

Accepted Answer

Negative feedback reduces or reverses a change to bring a variable back toward a set point, which helps maintain homeostasis. Positive feedback increases or amplifies a change, moving the process farther from the starting condition until a specific event ends the loop.

Question 8

During childbirth, pressure on the cervix causes release of oxytocin. Oxytocin increases uterine contractions, which causes more pressure on the cervix and more oxytocin release. Identify this as positive or negative feedback and explain your choice.

Accepted Answer

This is positive feedback because the hormone response strengthens the original stimulus. More cervical pressure causes more oxytocin release, and more oxytocin causes stronger contractions until the baby is delivered.

Question 9

The hypothalamus releases TRH, which signals the pituitary gland to release TSH. TSH signals the thyroid gland to release thyroid hormones. When thyroid hormone levels are high, they reduce TRH and TSH release. Explain why this is an example of negative feedback.

Accepted Answer

This is negative feedback because high thyroid hormone levels inhibit the earlier steps in the pathway. By reducing TRH and TSH release, the body lowers stimulation of the thyroid gland and prevents thyroid hormone levels from rising too high.

Question 10

A patient has symptoms of high metabolism, including weight loss, sweating, and rapid heartbeat. Lab results show high thyroid hormone and very low TSH. Use feedback loop reasoning to explain why TSH is low.

Accepted Answer

TSH is low because high thyroid hormone levels send negative feedback signals to the pituitary gland and hypothalamus. This feedback reduces TSH release in an attempt to decrease stimulation of the thyroid gland.

Question 11

Compare steroid hormones and peptide hormones in terms of how they interact with target cells.

Accepted Answer

Steroid hormones are lipid-soluble, so they can pass through the cell membrane and bind to receptors inside the cell, often affecting gene expression. Peptide hormones are not lipid-soluble, so they usually bind to receptors on the cell membrane and trigger signal pathways inside the cell.

Question 12

A stress response pathway begins when the brain detects danger. The hypothalamus and pituitary gland signal the adrenal glands, which release cortisol. Cortisol helps increase blood glucose and affects metabolism. High cortisol can reduce further signaling from the hypothalamus and pituitary. Describe the stimulus, hormone response, and feedback type in this pathway.

Accepted Answer

The stimulus is the detection of stress or danger by the brain. The hormone response includes signaling from the hypothalamus and pituitary gland that causes the adrenal glands to release cortisol. The feedback type is negative feedback because high cortisol reduces further signaling from the hypothalamus and pituitary.

Biology: The Endocrine System: Hormones and Feedback Loops

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