Question

match each identified muscle or organ to whether it engages in voluntary contractions, involuntary contractions, or both.
rectus abdominals (front of abdomen)
heart
biceps (upper arm)
uterus
stomach

Explanation:

• Rectus abdominis (front of abdomen): Voluntary. Skeletal muscles like rectus abdominis are under conscious control. You can choose to contract them (e.g., when doing sit - ups).
• Heart: Involuntary. The heart is made of cardiac muscle, which contracts without conscious control to pump blood.
• Biceps (upper arm): Voluntary. Biceps are skeletal muscles. You can consciously decide to contract them (e.g., when lifting an object).
• Uterus: Involuntary. During pregnancy (especially during labor) and menstruation, the uterus contracts without conscious control.
• Stomach: Involuntary. The smooth muscle in the stomach contracts to mix food and move it along the digestive tract without conscious thought.

Answer:

• rectus abdominis (front of abdomen): voluntary
• heart: involuntary
• biceps (upper arm): voluntary
• uterus: involuntary
• stomach: involuntary