Answer:
Tidal power, solar power, energy, wind power, biofuel, and hydrogen are six alternative energy sources.
Answer: A) Tactile cells anchor the skin to the underlying structures of the body.
Explanation:
Tactile cells are present over the surface layer of the skin on the epidermis and dermis. These cells are distinguished from the cells that lie in the underlying organs. These cells will help in determining the touch stimuli.
Answer:
The digestive system helps break down complex meals into the constituent parts the body can use: carbohydrates, proteins, fats, vitamins and minerals.
Digestion is important for breaking down food into nutrients, which the body uses for energy, growth, and cell repair. Food and drink must be changed into smaller molecules of nutrients before the blood absorbs them and carries them to cells throughout the body.
Explanation:
They need it to grow healthy
(1) The varying number of muscle fibers that contract
<span>In most muscles, the number of muscle fibers in different motor units ranges from a few to hundreds. The nervous system can thus regulate the strength of contraction in a muscle by determining how many motor units are activated at a given instant and by selecting large or small motor unties to activate. </span>
some muscles are almost always partially contracted. In such muscles, the nervous system my alternate activation among the motor units, reducing the length of time any one set of fibers is contracted. Prolonged contraction can result in muscle fatigue due to the depletion of ATP and dissipation of ion gradients required for normal electrical signals.ing.
<span>(2) varying the rate at which muscle fibers are stimulated </span>
<span>single action potential produces a twitch lasting about 100 msec or less. If a second action potential arrives before the muscle fiber has completely relaxed, the two twitches add together, resulting in greater tension. Further summation occurs as the rate of stimulation increases. When the rate is so high that the muscle fiber cannot relax at all between stimuli, the twitches fuse into one smooth, sustained contraction called tetanus.</span>
