Answer:
Explanation:
The protons and neutrons huddle together in the nucleus, or center, of the atom, while the electrons spin around the nucleus. ... An element is a pure substance that is made from one single type of atom. For example, gold is an element that is made up of gold atoms. Oxygen is an element made up of oxygen atoms.
Answer:
The rock cycle is a constant transformation of rocks between the three rock types of igneous, sedimentary, and metamorphic. If the sediments are buried behind other layers of sediment, they can lithify and form sedimentary rock. When rocks melt, magma is formed. Rocks form deep below the Earth, move and sometimes change, rise to the surface, and eventually return to their original location.
Answer:
The correct answer is serous glands.
Explanation:
The serous glands comprise serous acini, an array of serous cells, which discharge serous fluid isotonic with the plasma of the blood that constitutes enzymes like alpha-amylase. They are most predominant in the lacrimal and the parotid gland, however, are also found in the submandibular gland, and to some extent in the sublingual gland.
Ch.5: Synaptic Activity
<span>Introduction<span>Otto Loewi studied the heart of the frog, which-like our own hearts- is supplied by two different peripheral nerves. One, the sympathetic nerve, excites the heart and makes it beat more rapidly; the other , the vagus, shows the heart. The problem was to discover the mechanism by which the effects of nerve impulses in either of these nerves are communicated to the heart muscle. Many believed that the electrical nerve impulse spread from the nerve to the muscle as an electrical wave; Loewi thought otherwise.Loewi tested two isolated frog hearts, one with the sympathetic and vagus nerves intact, the other with the nerves removed. A small tube containing salt water was placed in the heart with the nerves attached. When he stimulated the vagus nerve, the heartbeat slowed, as expected. Then he took salt solution that had been in the stimulated heart and placed it inside the heart without nerves. It too immediately slowed- exactly as if its own (missing) vagus nerve had been stimulated.He repeated the same procedure, stimulating the sympathetic nerve instead. The effect was again as if the nerve of the denervated heart itself were stimulated: the denervated heart began beating faster. These results could not be explained electrically; the nerves must have secreted chemicals into the salt solution that directly affect the muscles of the denervated heart.In one simple experiment, Loewi had demonstrated three important findings: (1) that communication at the gap between nerve and heart muscle was chemical, (2) that each nerve released a different transmitter substance, and (3) that it was the characteristics of the different transmitter substances that caused the increase or decrease in heart rate. This was the first direct experimental evidence of the action of chemical neurotransmitters.<span>Like the junction between nerve and heart muscle that Loewi studied, nerve cells communicate with each other at special junctions called synapses. </span></span></span><span><span> thanks and i hope this helps you.....
</span></span>