Which of the following must be true about the structures of axons and muscle cells in order for nerve impulses to stimulate muscle contraction?
a- Axons and muscle cells must both have structures that make and secrete the same small molecules.
b- axons and muscle cells must both have receptors that recognize the same small molecules.
c- Axons must have structures that make and secrete molecules, and muscle cells must have receptors that recognize these molecules.
d-Muscle cells must have structures that make and secrete molecules, and axons must have receptors that recognize these molecules.
c- Axons must have structures that make and secrete molecules, and muscle cells must have receptors that recognize these molecules.
The correct option is c: Axons must have structures that make and secrete molecules, and muscle cells must have receptors that recognize these molecules.
In order for nerve impulses to stimulate muscle contraction, there must be a communication between the axons (nerve cells) and the muscle cells. And for this communication to occur, certain conditions must be met.
Let's break down each answer option to determine which one is true:
a) Axons and muscle cells must both have structures that make and secrete the same small molecules.
This option suggests that both axons and muscle cells produce and release the same small molecules. However, this statement is not necessarily true because there are several ways in which nerve impulses can stimulate muscle contraction without relying on the secretion of small molecules.
b) Axons and muscle cells must both have receptors that recognize the same small molecules.
This option suggests that axons and muscle cells need to possess receptors that can identify and respond to the same small molecules. While receptors play a crucial role in cell communication, this statement is not entirely accurate in the context of nerve impulses stimulating muscle contraction. The transmission of nerve impulses to muscle cells primarily involves the release of specific neurotransmitters, rather than small molecules interacting with receptors.
c) Axons must have structures that make and secrete molecules, and muscle cells must have receptors that recognize these molecules.
This option combines elements from the previous two options. It correctly acknowledges that axons release molecules (neurotransmitters), and muscle cells have receptors that recognize these neurotransmitters. This recognition of the released neurotransmitters triggers a response in the muscle cells, leading to muscle contraction. Therefore, this option is correct and describes the necessary conditions for nerve impulses to stimulate muscle contraction.
d) Muscle cells must have structures that make and secrete molecules, and axons must have receptors that recognize these molecules.
This option suggests the opposite of what actually happens. Muscle cells do not typically release molecules that axon receptors recognize. Instead, axon terminals release neurotransmitters that muscle cell receptors recognize and respond to.
Therefore, the correct answer is option c: Axons must have structures that make and secrete molecules, and muscle cells must have receptors that recognize these molecules.