Primary spermatocytes, spermatids
Most of the water reaching the collecting ducts is not reabsorbed
The vacuole i believe is the answer
Answer:
At the beginning you start out with a lot of energy and stamina but as you progress, maybe five minutes in, you start to get out of breath. While breathing harder, you are trying to intake more oxygen and at the 10 minute mark you can feel your muscles burning a little bit and tire out more. At this point you are gasping for oxygen because your muscles are deprived of oxygen and you body makes lactic acids which you muscles can use instead of oxygen. By the end of it you are very tired.
Explanation:
Hope this helps! I am not sure how scientific of an explanation you wanted.
The conduction of nerve impulses relies upon the movement of positively-charged ions across the nerve cell membrane. The entry of sodium into the cell produces a wave of positive charge that travels down the length of an axon. Then chemicals called neurotransmitters are secreted out of the end of the axon onto the next nerve in the series (the postsynpatic nerve). This narrow space in between neurons is called the synapse. These neurotransmiiters released by the presynaptic nerve bind to receptors on the postsynaptic nerve. The binding of these receptors opens up channels in this second nerve's membrane that allow sodium ions to enter the nerve cell and initiate another wave of positive charge, and so on... The nerve signal can only move as fast as these ions and neurotransmitters can diffuse to generate this process.
<span>As a professional athlete repeats a given activity many times over, the nerve cells "upregulate" their receptors, meaning that they produce additional receptors to put in the membrane. This is just a natural reaction to the nerve being repeatedly stimulated in the same way over and over. When neurotransmitter is secreted from the presynaptic neuron, there are more receptors on the postsynaptic neuron for it to bind, more channels open up, more ions enter in a shorter time and build up positive charge to create the impulse faster, and so the overall effect is faster. </span>
<span>Additionally, there are sheaths of fatty tissue (called myelin) that insulate the charge in the neuron and allow it to be conducted faster. As people age, these sheaths can start to degrade, making the nerve cell more "leaky" and causing the impulse to be conducted more slowly. </span>
