A rock climber grasps onto a ledge in the rock wall. How do the bones and muscles in his arm interact to allow him to hold on?

photo of a man climbing a rock wall
All of the muscles in his arm contract to hold his arm in position.
His arm muscles work in pairs so that one contracts while the other relaxes to hold his arm in position.
His arm muscles work independently of each other to hold his arm in position.
All of his arm muscles relax to hold his arm in position.

Muscles located in the walls of the small intestine help push digested material along. Muscles located in the walls of arteries help push blood along. Based on this information and your understanding of muscle types, which of the following statements is correct? (1 point)

Both sets of muscles are involuntary and smooth.
Both sets of muscles are voluntary and smooth.
Both sets of muscles are smooth, although one set is voluntary, and the other set is involuntary.
Both sets of muscles are voluntary, although one set is striated, and the other set is smooth.

Which of the following sets of words best fills in the blanks in the following sentence?

Despite their ______ structure, human bones are surprisingly _________.
solid; lightweight
compact; flexible
spongy; fragile

answers for now : 1D 2B 3A 4A

I did this lesson and the answers are 1:B, 2:A, 3:A (For some reason it's not written down here but the options for 3 were A: hollow; strong, B: solid; lightweight, C: compact; flexible, D: spongey; flexible. so its not on here but the actual answer is A)

m is right i got 100%

A rock climber grasps onto a ledge in the rock wall by using the interaction between the bones and muscles in his arm. The muscles in his arm contract to generate force and pull on the bones, allowing him to hold on. Here's a breakdown of how the bones and muscles interact in this scenario:

1. When the climber wants to grab onto the ledge, he sends a signal from his brain to the muscles in his arm, telling them to contract.
2. The muscles in his arm consist of pairs of antagonistic muscles. One muscle in the pair contracts while the other relaxes. This arrangement allows for controlled movement and stability.
3. As the contracting muscle shortens, it pulls on the tendons, which are attached to the bones.
4. The force generated by the contracting muscle is transmitted through the tendons to the bones in the arm, creating a solid grip on the rock ledge.
5. The bones in the arm provide a rigid structure, giving stability and support to the muscles and allowing them to exert force efficiently.

In summary, the muscles in the climber's arm work in pairs, with one muscle contracting while the other relaxes, to hold his arm in position. The contraction of muscles generates force, which is transmitted through tendons to the bones, providing a solid grip on the rock ledge.

Regarding the second question about the muscles in the small intestine and arteries, the correct statement is: Both sets of muscles are smooth, although one set is voluntary, and the other set is involuntary.

Muscles located in the walls of the small intestine and arteries are both smooth muscles. Smooth muscles are involuntary (not under conscious control) and contain spindle-shaped cells with a single nucleus. In the case of the small intestine, these smooth muscles help propel digested material along the digestive tract. In arteries, the smooth muscles help push blood along by contracting and relaxing.

Lastly, for the sentence "Despite their ______ structure, human bones are surprisingly _________.", the best set of words to fill in the blanks is "solid; lightweight". Human bones have a solid structure, providing strength and support to the body. However, despite their solid nature, human bones are surprisingly lightweight, thanks to their porous and trabecular internal structure, which contains marrow, air pockets, and collagen fibers. This combination of solid structure and lightweight nature allows for mobility while still providing protection and support.

1.A

2.?
3.B