Choose one answer below that completes the sentence so that it makes a true statement: Positive feedback: A. is the way the body maintains homeostasis B. is a response that opposes a stimulus C. is a response that maintains a dynamic state of equilibrium D. is a response that enhances a stimulus

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Question 13: Choose one answer below that completes the sentence so that it makes a true statement: Positive feedback:

Positive feedback mechanisms amplify an initial stimulus, moving the system further away from the set point. Homeostasis is primarily maintained by negative feedback.

• A. is the way the body maintains homeostasis - Incorrect, this describes negative feedback.
• B. is a response that opposes a stimulus - Incorrect, this describes negative feedback.
• C. is a response that maintains a dynamic state of equilibrium - Incorrect, this describes homeostasis.
• D. is a response that enhances a stimulus - Correct, positive feedback amplifies the original stimulus.

The correct option is D.

• D. is a response that enhances a stimulus

Question 14: The hypothalamus and core thermoreceptors notice if body temp too low. The hypothalamus signals smooth muscle vessels to vasoconstrict and skeletal muscle to shiver. This activity causes body temp to rise, which is again noticed by hypothalamus & core thermoreceptors, so the hypothalamus turns off these heat gain mechanisms. In this scenario, which of the following statements is correct?

This scenario describes a negative feedback loop, where the body's response (increased temperature) counteracts the initial stimulus (low temperature) to return to a set point.

• A. The scenario describes positive feedback in action. - Incorrect, it describes negative feedback.
• B. The core thermoreceptors are the effector organs. - Incorrect, thermoreceptors are receptors (sensors).
• C. The hypothalamus is the control centre. - Correct, the hypothalamus integrates information and coordinates the response.
• D. Skeletal muscle is the efferent pathway to the effector organ. - Incorrect, skeletal muscle is an effector organ; the efferent pathway consists of the nerves leading to it.

The correct option is C.

• C. The hypothalamus is the control centre.

Question 15: Some of the body's homeostatic responses rely on "negative feedback". Which of the following happens in negative feedback?

Negative feedback is a regulatory mechanism where the body's response counteracts or opposes the initial change or stimulus, bringing the physiological variable back towards its set point.

• A. The body ignores changes in a physiological variable that are directed towards the set point for that variable. - Incorrect.
• B. The body ignores changes in a physiological variable that are directed away from the set point for that variable. - Incorrect.
• C. The body's response acts to oppose the change in the physiological variable. - Correct.
• D. The body's response acts to enhance the change in the physiological variable. - Incorrect, this describes positive feedback.

The correct option is C.

• C. The body's response acts to oppose the change in the physiological variable.

Question 16: Long-term potentiation (LTP) is mainly associated with:

Long-term potentiation (LTP) is a persistent strengthening of synapses based on recent patterns of activity. It is a key cellular mechanism underlying learning and memory.

• A. Muscle contraction - Incorrect.
• B. Learning and memory - Correct.
• C. CSF production - Incorrect.
• D. Reflex inhibition - Incorrect.

The correct option is B.

• B. Learning and memory

Question 17: What is the resulting effect of renin being released by the kidney?

Renin is an enzyme released by the kidneys. Its primary role is to initiate the renin-angiotensin-aldosterone system (RAAS) by converting angiotensinogen into angiotensin I. Angiotensin I is then converted to angiotensin II, which has various effects on blood pressure and fluid balance.

• A. Angiotensin II is formed - Correct, renin initiates the cascade that leads to the formation of angiotensin II.
• B. aldosterone is released - Incorrect, aldosterone release is stimulated by angiotensin II, which is a subsequent step.
• C. macula densa sends paracrine message to afferent arterioles. - Incorrect, the macula densa detects changes that trigger renin release, it's not a result of renin release.
• D. efferent arterioles are constricted. - Incorrect, this is an effect of angiotensin II, not a direct result of renin itself.

The correct option is A.

• A. Angiotensin II is formed

Question 18: The filtrate that is formed in the kidney contains all of the following except one. Which one?

Glomerular filtrate is formed by the filtration of blood plasma in the renal corpuscle. It contains water, small solutes like ions, glucose, amino acids, and metabolic wastes. Large molecules like plasma proteins and blood cells are typically retained in the blood and do not pass into the filtrate.

• A. metabolic wastes - Correct, these are filtered (e.g., urea).
• B. glucose - Correct, glucose is filtered and then mostly reabsorbed.
• C. plasma proteins - Incorrect, large plasma proteins are generally not filtered.
• D. amino acids - Correct, amino acids are filtered and then mostly reabsorbed.

The correct option is C.

• C. plasma proteins