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.

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. 

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.

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3 years ago

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Among vertebrates, the unique feature of lampreys and hagfish is the ________. among vertebrates, the unique feature of lampreys

marshall27 [118]

The correct answer is absence of jaws.
Lampreys and hagfish are in the class Agnatha, they are jaw-less fish. The members of the agantha class are probably the earliest vertebrates. Scientists have found fossils of agnathan species from the late Cambrian period that occurred 500 million years ago.

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3 years ago

An ice fisherman has fallen through the ice. In response to the cold water, sensors in the man's skin send a "cold" signal to th

Svet_ta [14]

Answer:

Hypothalamus

Explanation:

The hypothalamus is a part of the brain which possesses temperature receptor cells that detect changes in the man’s temperature, thereby sending signals in the form of electrical nerve impulses to the man’s muscles and nervous system, which in turn respond in counteracting the drop in the normal temperature of the body.

Once the muscle cells of this man receive these signals, they produce heat through thermogenesis by shivering when the muscle cells begin to contract. This is one of the mechanisms by which thermoregulation is achieved as controlled by the hypothalamus in the brain of the man.

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3 years ago

a german measles rubella epidemic during the years 1963 to 1965 resulted in approximately 30,000 babies being born with birth de

Juli2301 [7.4K]

Answer:

In babies born with congenital defects during the German measles rubella epidemic the specific cause of these birth defects was most likely the development of rubella virus infections in embryos.

Explanation:

Options for this question are:

1. The development of rubella virus infections in embryos. 

2. The failure of zygotes infected with rubella to develop

3. Mutations in the nerve cells of pregnant females at the time of the rubella epidemic .

4. An increase in the amount of time needed for healthy embryonic development.

Rubella is a viral infection caused by a virus of the genus Rubivirus, considered highly teratogenic during the phases of pregnancy where the embryo and the fetus are developing, that is, before 20 weeks of gestation.

The virus is transferred to the embryo or fetus by the mother's blood, acquiring the disease, which can cause abortions or visible malformations at birth, which is called Congenital Rubella Syndrome (CRB).

CRB is responsible for producing cardiovascular, renal, neurological malformations, loss of vision or hearing, problems that German children born during the epidemic probably had.

Learn more:

Congenytal rubella brainly.com/question/2107536

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3 years ago