The answer is a simple radial nervous system.
Echinoderms do not have brains. Around their mouth, they have central rings from which nerves radially run into arms and along the body. Movement is controlled by the branches of those radial nerves.
Answer:
1. Signaling molecule
2. Signaling receptors
Explanation:
Hormones, growth factors, neurotransmitters, etc. serve the function of signaling molecules for cells. These molecules are released by one cell and bind to the receptors present on/in the target cells to elicit the desired response. Thereby, the signaling molecules serve in cell-cell communication.
For example, insulin hormone synthesized and released from beta cells of pancreas binds to its cell surface receptors present on the surfaces of liver cells and muscle cells to stimulate the uptake of the glucose from the blood.
Likewise, neurotransmitters released from the presynaptic neuron bind to receptors present on the membrane of postsynaptic neuron and serve to carry the nerve impulse to the postsynaptic neuron.
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The biggest difference between the two is that the nervous system uses electrical impulses to send signals through neurons, whereas the hormonal system uses chemical messengers transported into blood plasma to target cells.
Transmission by the nervous system is short-lived but quick, whereas transmission by the hormonal system is long-lasting but takes much longer. Hene, communication is faster when using the nervous system.
In the nervous system, responses are localised - whereas in the hormonal system, they are widespread. Responses are often permanent in the hormonal system, but temporary and reversible in the nervous system.
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Answer:
The molecule that would be affected by 'limited nitrogen' is the myofibrillar proteins in muscle. Explanation: The myofibrils of the muscle have a number of protein molecules.
