Homeostasis MCQs - MCQtimes.com

Which of the following is a correct definition of “negative feedback”?

The process by which the body maintains homeostasis

A mechanism in which the body’s response opposes the stimulus

A mechanism whereby the body responds to a stimulus by acting to enhance the stimulus

The dynamic equilibrium maintained by an integrating centre which causes an effector to respond to the stimulus received by the receptor

When an action is taken to cause the stimulus to be reduced, the feedback is termed “negative”.

Author: rikazzz Comment

Homeostasis

During the delivery of a baby, the baby’s head is pushing against the cervix causing the cervix wall to stretch. This stretching causes nerve impulses to be sent to the hypothalamus which directs the posterior pituitary to release oxytocin in the blood. Oxytocin stimulates the uterus to contract which pushes the baby’s head deeper into the cervix, stretching it further. This situation is a description of which of the following?

Negative feedback

Positive feedback

Homeostasis

An afferent pathway to an integrating centre

The stimulus (cervical stretching) causes the integrating centre (the hypothalamus) to respond by enhancing the stimulus – releasing oxytocin so that the uterus contracts. Enhancing the stimulus is an example of positive feedback. The feedback stops when the cervix is no longer being stretched, that is, when the baby is delivered.

Author: rikazzz Comment

Homeostasis

Choose one answer below that completes the sentence so that it makes a true statement. Positive feedback:

Is the way the body maintains homeostasis

Is a response that opposes a stimulus

Is a response that maintains a dynamic state of equilibrium

Is a response that enhances a stimulus

“Positive” feedback will reinforce the stimulus, making it greater or more insistent.

Author: rikazzz Comment

Homeostasis

When peripheral chemoreceptors detect an increase in the concentration of dissolved carbon dioxide in arterial blood above 45 mmHg (the upper limit of normal), which of the following homeostatic responses would occur?

Respiratory rate increases so that more carbon dioxide may be exhaled.

Respiratory rate decreases so that less carbon dioxide may be exhaled.

Respiratory rate increases so that less carbon dioxide may be exhaled.

Respiratory rate decreases so that more carbon dioxide may be exhaled.

The homeostatic response opposes the stimulus, so if blood pCO2 is rising, the response must produce a decrease in pCO2. If respiratory rate increases, the increase in lung ventilation will blow off more CO2 (not less). This will lead to a decrease in the gas dissolved in arterial blood and a restoration of the healthy dissolved carbon dioxide concentration.

Author: rikazzz Comment

Homeostasis

Which of the following is an example of negative feedback?

The uterine contractions during childbirth push the baby’s head against the cervix which stimulates the uterus to contract.

The release by platelets that aggregate at the site of a blood vessel injury, of compounds that promote platelet aggregation.

As resting membrane potential rises, voltage-gated ion channels open which allow ions to enter the axon which causes further rise in the membrane potential and more ion channels to open.

As blood sugar level rises, insulin is released which promotes the absorp-tion of glucose from the blood by liver, muscle and fat cells.

In this choice the response to rising glucose is the release of insulin, which promotes a decrease in blood glucose by causing it to be absorbed from the blood. That is, the response is to oppose the change that initiated the response. This is termed “negative” feedback. The other three choices are examples of positive feedback.

Author: rikazzz Comment

Homeostasis

What causes the body to maintain a relatively constant internal environment?

Positive feedback

Homeostasis

Reflexes

pH buffers

Homeostasis matches the definition in the question.

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Homeostasis

Homeostasis relies on feedback to achieve its aims. “Negative” feedback refers to which situation below? The body’s response:

Travels from the effector to the integrating centre via the afferent pathway

Opposes the stressful stimulus

Is to decrease the set point

Enhances the stressful stimulus

“Negative” refers to the opposing nature of the response.

Author: rikazzz Comment

Homeostasis

Select the example below that describes an example of positive feedback.

The hypothalamus, noticing that body temperature is falling, initiates the muscular contractions we know as shivering.

The macula densa of the nephron notices an increase in the sodium ion concentration in the filtrate and signals the afferent arteriole to constrict.

The contractions of the uterus force the head of the foetus against the cervix which causes the uterus to contract more forcefully.

The stretch receptors of the carotid sinus notice that the wall of the carotid artery is more stretched. This information is sent to the brain which then causes the heart rate to decrease.

Examples of positive feedback in human physiology are rare. The contractions of childbirth is one. The other three describe negative feedback.

Author: rikazzz Comment

Homeostasis

What does the term “homeostasis” refer to?

The chemical processes that take place in the organelles of the cells

The body’s tendency to maintain a relatively constant internal environment

The body’s use of energy to produce chemical substances and parts for growth

Any body response that opposes the stimulus that initiated the response

This is the best definition of homeostasis. Choice D refers to negative feedback.

Author: rikazzz Comment

Homeostasis

Which of the following is a correct definition of “positive feedback”?

The process by which the body maintains homeostasis

A mechanism in which the body’s response to a stimulus opposes the stimulus

A mechanism whereby the body responds to a stimulus by acting to enhance the stimulus

The dynamic equilibrium maintained by an integrating centre which causes an effector to respond to the stimulus received by the receptor

When the stimulus is enhanced, the feedback is termed “positive”.

Author: rikazzz Comment