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>
Answer:
The carrying capacity of a wildlife reserve is 570 individuals for a particular species of rodents. If the area of the reserve is extended, the carrying capacity is likely to Increase
During the summer, a fatal disease began killing individuals. The carrying
capacity of the reserve will therefore decrease
Explanation:
The carrying capacity of a habitat is the maximum number of individuals of a given species it can support without depleting the available resources. When the area of the reserve is extended, the carrying capacity increases because the available resources will also increase. A fatal disease would increase the carrying capacity since the number of wildlife would decrease.
Answer:
True
Explanation:
When the resting potential of the membrane is changed, the membrane becomes either more negative inside or less negative. This small deviation from the resting potential is called graded potential. A graded potential occurs when a stimulus triggers opening or closing of the mechanically gated or ligand-gated channels present in the plasma membrane.
For example, the presynaptic neuron releases neurotransmitters in response to a nerve impulse. The neurotransmitter binds to receptors present in the plasma membrane of the postsynaptic neuron and triggers the opening of the ion channels to allow the inflow of particular ions to flow. The flow of ions changes the voltage across the membrane. This change in membrane voltage is a postsynaptic potential and is a type of graded potential.
<span>The structure of a paramecium that holds a "reserve copy" of all the cell's genes is the micro nucleus.
</span>The micro nucelus is one of the <span>two kinds of </span>nuclei the paramecium has. The other is the<span> large ellipsoidal </span>nucleus<span> called a macronucleus. Every paramecium must have at least one small </span>nucleus<span> called a </span>micronucleus. The micronucleus is a storage site for the germline genetic material of the organism.
Answer:
C. Genetic material composed of nucleic acid
Explanation:
The information needed by every organism to perform life functions like reproduction, growth etc are held in the genetic material that the organism carries in its genome. Every genetic material of organisms is composed of nucleic acids, which are only two in nature i.e. Ribonucleic acid (RNA) and Deoxyribonucleic acid (DNA). This is a common feature of all organisms including bacteria and viruses that they contain genetic material which must be in form of a nucleic acid.
The viruses do not undergo a cell division, neither do they contain protein synthesis structures called Ribosomes because they do not have the ability to reproduce or perform any living process outside a living host cell. This means that they strictly depend on another organism's transcriptional, translational, replicational ability to survive.
