Chapter 11

Assignment questions

Neurons communicate with other neurons and stimulate effector cells which includes both _____ and _____

Muscles and glands

Dendrites function

Receptive region, receives signals from other neurons

Cell body’s function

receptive and integrative region, main nutritional and metabolic area

Axon’s function

conductive region, generates an action potential and transmits signals to other neurons.

Signals from other neurons are received at junctions called _____, located primarily on the _____ and _______, the receptive and integrative regions of the neuron

Synapses. dendrites and cell body

The area where the axon emerges from the soma is called the _____. This is also the area where the outgoing signal called a/an ________ is generated

Axon hillock; Nerve impulse

What neuroglia type forms the myelin sheath in the PNS?

Schwann cells

Myelin is found around which part of the neuron

Axon

The tightly wound cell membrane around the axon forms the myelin sheath and acts as _______

An insulator

The gaps between the schwann cells, called the __________, are essential for the conduction of the action potential

Nodes of Ranvier

The most common structural classification of neurons in the CNS is called a/an _______ neuron.

Multipolar

Neurons have ____ axons

only one

Axons are _____ branched at their terminal end.

Frequently

Dendrites have ______ branch/branches

many

Channels can be classified as either gated or leak channels. A sodium channel that is always open would be classified as a/an ______ channel.

Leak

Sodium ions move _____ the neuron through ion channels

Into

The 4 types of neuroglia in the CNS

Astrocytes, microglia, ependymal, and oligodendrocytes

The 2 types of neuroglia in the PNS:

Satellite cells and Schwann cells

Excitable cells, like neurons, are more permeable to _____ than to ____ at rest.

more permeable to K+ than to Na+ at rest

What acts as a chemical force that pushes K+ out of the cell?

concentration gradients

What force potentially encourages K+ to move back into the cell?

Electrical gradient

In an excitable cell, also permeable to Na+, the electrochemical gradient would both tend to move Na+ _____ the cell.

into

What compensates for the movement (leakage) of Na+ and K+ ions?

Na-K pump

The action potential changes the membrane potential from ____ mV (resting) to ___mV and back again to the resting membrane potential

This results from a change in membrane permeability first to ____ and then to ____ due to the opening of what type of ion channels?

from -70mv to +30mV; first to Na+ and then to K+ due to voltage gated channels

What area of the neuron contains the trigger zone, where the action potential is generated

Axon hillock

What areas of the neuron generate signals that open these voltage-gated channels?

Dendrites and cell bodies

Opening of these channels causes the membrane to ______

Depolarize

If the membrane reaches the trigger point, _____, what electrical potential will be generated?

Threshold; action potential (nerve impulse)

What are the 2 processes that stop the potential from rising above +30mV

1) inactivation of sodium channels

2) activation of potassium channels

The opening of voltage-gated K+ channels causes the membrane to ____

Repolarize

Does K+ move into or out of the cell?

Out

If the membrane potential becomes more negative than -70mV, this is called ______

Hyperpolarization

After an action potential, the neuron cannot generate another action potential because _____ channels are inactive

This period is called the ________ period

Na+; absolute refractory

During the ______ period, the cell can generate another action potential but only if the membrane is ____ depolarized.

Relative refractory; more

Conduction velocity along the axon is increased by what 2 characteristics?

1) myelin sheath

2) axon diameter

Conduction along a myelinated axon is called _____ conduction

Saltatory

When many nerve impulses arrive in rapid succession at the synapse between a single stimulatory presynaptic neuron and a postsynaptic neuron, this is known as ____ summation

Temporal

When nerve impulses from several presynaptic neurons stimulate a single postsynaptic neuron at the same time is called _____ summation

Spatial

Order the sequence of events that happen at a synapse

1) Action potential reaches the axon terminal

2) Voltage- gated Ca+2 channels open allowing Ca+2 to rush into axon terminal

3) Ca+2 binds to synaptic vesicles, triggering exocytosis of neurotransmitter molecules

4) Neurotransmitter diffuses across synaptic cleft

5) Neurotransmitter binds to receptors on the postsynaptic membrane

6) Ion channels open creating a local potential on the postsynaptic membrane

What are 2 functions of the astrocytes?

Support and brace neurons, and regulate the chemical environment around neurons

Which of the following describes the nervous system sensory function?

Senses change in the environment

Which of the following is not a characteristic of neurons?

They:

Conduct impulses

Have extreme longevity

Are mitotic

They are mitotic

Oligodendrocytes are functionally similar to:

Schwann cells

A neuron that carries impulses away from the CNS to effector organs is an:

Efferent neuron

The resting membrane potential is generated by:

Differences in ionic makeup of ICF and ECF

& differences in permeability of the plasma membrane

At rest the plasma membrane of the neuron is more permeable to:

Potassium

When the interior of the cell becomes more negative, decreasing the change of producing a nerve impulse it is called:

Hyperpolarization

Which ion channel opens in response to a change in the membrane potential and participates in the generation and conduction of action potentials

Voltage- gated channels

Immediately after an action potential has peaked, which cellular gates open?

Potassium

Collections of nerve cell bodies in the central nervous system are called:

Nuclei

Saltatory conduction is made possible by:

Myelin sheath

What structure is specialized for release and reception of neurotransmitters?

Chemical synapse

What type of membrane potential is generated at the synapse on postsynaptic membrane?

Local potential

When a postsynaptic neuron is stimulated by a large number of terminals at the same time this results in:

Spatial summation

The time period when a neuron cannot respond to another stimulus is the:

Absolute refractory period