<span>A. the current hypothesis of the evolutionary relationships between organisms.</span>
Answer:
The heart valves
Explanation:
The heart valves prevent blood from flowing in the wrong direction in the heart. The valves are held in the proper place because of the chordae tendinae.
If the stimulus frequency is so high that the relaxation phase disappears completely, contractions become continuous in a process called complete tetanus.
What is tetanic contraction?
- When the motor neuron that innervates a skeletal muscle generates action potentials at an extremely rapid rate, a persistent muscular contraction known as a tetanic contraction is induced.
- A motor unit has experienced its motor neuron's maximum stimulation during this state, which lasts for a while. This happens when several impulses with a high enough frequency excite the motor unit of a muscle.
- Every trigger results in a twitch. A slow enough stimulus delivery will cause the muscular tension to release between each succeeding twitch. High frequency stimulation will cause the twitches to overlap, which will cause tetanic contraction.
Learn more about the Nervous system with the help of the following link:
brainly.com/question/3239081
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You need carbon dioxide and oxygen because you need oxygen to breath and plants depend on carbon dioxide without it we would have plants and without plants we wouldn’t have food.
<span>A stimulus is the reaction of something in a given environment.</span>
