Chapter 2- Communication And The Nervous System

Question 1

What are neurons?

Answer 1

Neurons are specialized cells that convey sensory information into the brain; carry out the operations involved in thought, feeling, and action; and transmit commands out into the body to control muscles and organs.

Question 2

What is the most prominent part of the neuron?

Answer 2

The Soma, or cell body.

Question 3

What is a nerve cell?

Answer 3

A neuron.

Question 4

What type of neuron carries commands to the muscles and organs?

Answer 4

Motor neurons

Question 5

What are extensions that branch out from the cell body to receive information from other neurons?

Answer 5

Dendrites.

Question 6

What extends like a tail from the cell body and carries information to other locations?

Answer 6

Axons

Question 7

Branches at the end of axon culminate in swellings called end bulbs or —-? These contain —- which do what?

Answer 7

Terminals. The terminals contain NEUROTRANSMITTERS which the neuron releases to communicate with a muscle or an organ or the next neuron in a chain.

Question 8

Describe the basic structure of nerve cells?

Answer 8

Neurons contain a cell body or soma. The soma is filled with a watery liquid called cytoplasm and many organelles. The largest organelle is the nucleus which contains the cell’s chromosomes. Other organelles are responsible for converting nutrients into fuel, creating proteins, and removing waste materials. Neuron specialized structures and functions include dendrites, which are extensions that branch out from the cell body to receive information from other neurons. Axons are a tail like like structure that juts out from the cell body for carrying information to other locations. Branches at the end of axons culminate in swellings called terminals. Terminals contain chemical neurotransmitters which the neuron releases to communicate with a muscle or an organ or the next neuron in a chain.

Question 9

What is a motor neuron?

Answer 9

It carries commands to the muscles and organs.

Question 10

These neurons carry information from the body and from the outside world into the brain and spinal cord?

Answer 10

Sensory neurons

Question 11

What are interneurons?

Answer 11

They connect one neuron to another in the same part of the brain or spinal cord. They are also the most numerous neurons.

Question 12

What are the 3 major types of neurons? Outline their function, form and location, as well as a description of each.

Answer 12

The 3 types of major neurons are motor, sensory and interneurons. Motor neurons conduct messages from the brain and spinal cord to muscles and organs. Sensory neurons carry information from the body and world to the brain and spinal cord. Interneurons carry information between neurons in the same area. Motor neurons are multipolar throughout the nervous system. Sensory neurons are unipolar- outside the brain, and bipolar-outside the brain and spinal cord. Interneurons are, like motor neurons multipolar, and throughout the brain and spinal cord. Finally, motor neurons involve axons, dendrites extending in several directions from the cell body. Sensory neurons involve a single short stalk from the cell body dividing into two branches. Axon and dendritic processes are on opposite sides of the cell body. Interneurons have a short axon or no axon.

Question 13

When there is a difference in electrical charge between the inside and the outside of the cell, this is called — ?

Answer 13

Polarization

Question 14

What is a nerve cell’s resting potential?

Answer 14

A way to measure a neuron’s voltage exists. The difference in charge between the inside and outside of the membrane of a neuron at rest is called the resting potential. Neither the inside of the neuron nor the outside has a voltage, because a voltage is a difference and is meaningful only in comparison with another
location. The voltage is negative from -40 to -80 millivolts and is typically -70mV. The resting potential is due to the unequal distribution of electrical charges on the two sides of the membrane. The charges come from ions, atoms that are charged because they have lost or gained one or more electrons. The inside of the neuron has more negative ions than positive ions, while the ions on the outside are mostly positive, allowing for a negative resting potential. The resting potential also stores the energy to power the action potential. The voltage across the resting neuron membrane is stored energy.

Question 15

Explain ion distribution in neurons?

Answer 15

Due to the force of diffusion, ions move through the membrane to the side where they’re less concentrated. As a result of electrostatic pressure, ions move away from the side that is similarly charged and are attracted to the side that is oppositely charged.

Question 16

What happens to the few ions that do make it through?

Answer 16

They are returned by the sodium-potassium pump which consists of large protein molecules that move sodium ions through the cell membrane to the outside and potassium ions back inside.

Question 17

What is the action potential?

Answer 17

An abrupt depolarization of the membrane that allows the neuron to communicate over long distances. If the local potential exceeds the threshold for activating that neuron, 10 mV, it causes the normally closed sodium channels in that area to open, triggering an action potential.

Question 18

What is the difference between local potential and action potential?

Answer 18

Local potential is a graded potential, it varies in magnitude with the strength of the stimulus that produced it. The action potential is ungraded, operating according to the all or none law- it occurs at full strength or not at all. The action potential is also nondecremental, it travels down the axon without any decrease in size, propagated anew and at full strength at each successive point along the way, allowing the neuron to conduct information over long distances. It can’t carry intensity information.

Question 19

What is the absolute refractory period?

Answer 19

A brief time during which it cannot fire again, this occurs because the sodium channels cannot reopen.

Question 20

During which period can the neuron be fired again, but only by a stronger than threshold stimulus?

Answer 20

The relative refractory period.

Question 21

What are glial cells?

Answer 21

Non-neural cells that provide a number of supporting functions to neurons. Can increase the conduction speed of neurons.

Question 22

Glial cells produce —– a fatty tissue that wraps around the Axon to insulate it from the surrounding fluid and from other neurons. — is produced in brain and spinal cord by a type of glial cell called oligodendrocytes and in the rest of the nervous system By Shwann cells.

Answer 22

Myelin

Question 23

The gaps in the myelin sheath are called?

Answer 23

Nodes of Ranvier

Question 24

The graded potential triggers triggers an action potential; action potentials jump from node to node in a form of transmission called?

Answer 24

Saltatory conduction