Question

body systems during exercise
passage:
scientists studied how different body systems respond during exercise. they monitored three participants during a 30 - minute exercise session on a stationary bicycle, measuring various physiological responses.
study 1: multiple system responses researchers tracked changes in different body systems during the exercise period.
table 1: physiological changes during exercise

time (min)	heart rate (bpm)	breathing rate (breathes/min)	skin temperature (°c)	muscle activity*
10	125	22	33	increased
20	155	28	34	high
30	165	32	35	high

*muscle activity measured through electrical signals
study 2: immune system response the scientists monitored immune system components before and after exercise.
table 2: immune system components

component	before exercise	during exercise	1 hour after
inflammatory response	none	mild	moderate
mucus production	normal	increased	normal

figure 1: integration of body systems during exercise
image: levels of organization during exercise: cells (muscle cells) → tissues (muscle tissue) → organs (heart) → systems (circulatory); nervous system connected to muscular, respiratory, circulatory, integumentary

1. which sequence reflects how the nervous system controls exercise response?

• brain (voluntary) → skeletal muscles → involuntary responses → homeostasis
• spinal cord → brain → muscles → circulation
• brainstem → involuntary responses → voluntary movement → homeostasis
• sensory neurons → brain → motor neurons → muscles

Explanation:

To determine the correct sequence of how the nervous system controls exercise response, we analyze each option:

• Option 1: The sequence "Brain (voluntary) → skeletal muscles → involuntary responses → homeostasis" is incorrect. Involuntary responses (like heart rate, breathing rate changes) are regulated by the brainstem and other autonomic nervous system components, and the order here is not accurate for the nervous system's control during exercise.
• Option 2: "Spinal cord → brain → muscles → circulation" is incorrect. The brain (not the spinal cord first) initiates voluntary movement, and circulation is a result of multiple systems, not a direct step in the nervous system's control of muscle movement.
• Option 3: "Brainstem → involuntary responses → voluntary movement → homeostasis" is incorrect. Voluntary movement (like moving the legs during cycling) is initiated by the cerebral cortex (not the brainstem), while the brainstem controls involuntary responses. So the order of voluntary movement after involuntary responses is wrong.
• Option 4: "Sensory neurons → brain → motor neurons → muscles" is correct. During exercise, sensory neurons detect stimuli (e.g., muscle stretch, body position), send signals to the brain (for processing), the brain then sends signals via motor neurons to muscles, causing them to contract and produce movement. This follows the typical sensory - integration - motor output pathway of the nervous system.

Answer:

D. Sensory neurons → brain → motor neurons → muscles