Chapter 7

Proposed functions of astrocytes

1. Absorption of K+ from the extracellular fluid 2. Uptake of glucose from the blood 3. Release of lactate

Steps of neurotransmitter

1. Action potential causes a change in the membrane potential of the terminal buoton. 2. Voltage gated Ca++ channels open. 3. Ca++ binds to sensor proteins in the cytoplasm. 4. Ca++ -protein ccomplex stimulates exocytosis.

Events of an excitatory synaptic transmission

1. Action potential reaches the terminal bouton 2. Voltage gated Ca++ channel open 3. Ca2+ enters causing the release of an excitatory neurotransmitter 4. Neurotransmitter binds to ligand-gated channel on the postsynaptic membrane causing it to open 5. Na+ enters the postsynaptic cell causing a depolarization

Events of the action potential.

1. Initial segment of axon reaches threshold 2. Voltage regulated sodium channels open 3. Na+ enters the cell causing depolarization 4. Membrane potential becomes +30mV 5. Na+ channels become inactivated 6. Membrane permeability to sodium declines

Spatial summation within the nervous system

1. It occurs when signals from several presynaptic neurons summate within one postsynaptic neuron. 2. It is due to convergence of neural pathways.

Events regarding K+ and the generation of the action potential

1. Threshold is reached. 2. K+ voltage gated channels open. 3. Repolarization starts. 4. K+ inactivation begins 5. Hyperpolarization

Events of the action potential.

1. Threshold is reached. 2. Na+ channels open fully & Na+ enters cell. 3. Na+ channels inactivated. 4. K+ channels open fully and K+ leaves the cells. 5. K + channels inactivated.

Acetylcholine (ACh)

1. is a neurotransmitter 2. is excitatory 3. is inhibitory

The myelin sheath that covers some axons:

1. is formed by oligodendrocytes in the CNS 2. is formed by Schwann cells in the PNS 3. increases the speed of impulse conduction

The neurilemma

1. is made up of Schwann cells 2. surrounds axons of the PNS

neurotransmitter

A _____ is a chemical that is release from a presynaptic cell in response to a stimulus which then causes a change in the membrane potential of a postsynaptic cell.

a nerve

A collection of axons wrapped together in the peripheral nervous system is called:

inhibits the activity of receptor proteins

A drug that is classifies as an antagonist:

depolarization

A positive change in the membrane potential of the cell

action potential

A propagated change in the membrane potential of a neuron due to the opening and closing of voltage gated channels is called a(n) _____ _____.

nerve

A(n) ______ is a cable like collection of axons in the peripheral nervous system.

neurotransmitter

Acetylcholine (ACh) is a _____ that can be either excitatory or inhibitory depending upon the binding cell.

antagonistic

Altropine, a drug frequently prescribed to heart patients, is classified as an _____ substance because it inhibits the activity of muscarinic receptors.

all or none

An action potential is either generated to its maximum amplitude or not produced at all. This is referred to as its ________ property.

end plate potentials

At the neuromuscular junction, the excitatory postsynaptic potential produced by acetylcholine in skeletal muscle fibers are also called _____ _____ ____.

same

Because the action potential is conducted without decrement, the AP produced at the last region of the axon has the _____ amplitude as that produced at the first region.

The axon has high internal resistence

Conduction based on a neuron's cable properties is poor because:

1. called salutatory conduction 2. is faster than in an unmyelinated axon 3. continues without decrement

Conduction od action potential in a myelinated axon is:

agonists

Drugs that bind to an thereby activate receptor proteins are called ____.

antagonists

Drugs that bind to and thereby reduce the activity of receptor proteins are called _____.

1. Na+ to enter the postsynaptic cell 2. an EPSP

During excitatory synaptic transmission, neurotransmitters from the presynaptic cell bind to ligand gated channels on the postsynaptic cell causing:

+30mV

During the generation of an action potential, the neuron goes from the resting potential of -70mV to a high of _____ during the maximum point of sodium ion entry.

hyperpolarization

If a stimulation causes the inside of a cell to become more negative than its resting potential, the cell has undergone _____.

temporal

In _____ summation, successively rapid bursts of activity of a single presynaptic axon cause corresponding burst of neurotransmitter release resulting in successive waves of EPSPs in the postsynaptic neuron that summate as they travel to the initial segment of the axon.

nodes of Ranvier

In myelinated axons, action potentials occur only at the _____ ___ _____.

axon collaterals

Many axons produce more than one branch, each of these ______ ______ then can synapse with many other neurons.

faster

Myelinated axons conduct impulses ____ than unmyelinated axons.

Spinal nerves & Cranial nerves

Structure that are part of the peripheral nervous system

blood-brain barrier

The _____ restricts the movement f molecules from the blood to the interstitial spaces in the brain.

astrocytes

The ______ of the central nervous system regulate the external environment around the neurons.

Na+

The absolute refractory period of an axon segment is dependent upon the length of time it takes a sufficient number of ____ channels to reset.

Schwann cells

The cells responsible for forming the myelin sheaths around axons in the peripheral nervous system are called _____.

electrical gradient

The combined electrical and concentration gradient that drives the movement of ions into and out of cells is known as the:

1. is slower than a myelinated neuron 2. is conduct without decrement

The conduction of an action potential in an unmyelinated axon:

The axon hillock of a neuron

The expanded part of the axon next to the cell body

Ranvier

The nodes of ____ are gaps in the myelin sheath surrounding axons.

1. cell body or soma 2. dendrites 3. axon (not neuroglia or synaptic cleft)

The regions or parts of the neuron include:

Nerve signal transmission

The signal travels from the presynaptic cell to the postsynaptic cell.

axon

The structure(s) responsible for conduction impulses called action potentials away from the cell body is (are) called _____.

Gap junctions

What are connexin protein channels that allow the movement of molecules between adjacent cells called?

1. sensory neurons 2. efferent neurons 3. autonomic motor neurons

What are functional classifications of neurons?

bipolar neurons & pseudounipolar neurons

What are structural classifications of neurons?

Central and peripheral

What are the 2 division of the nervous system?

White matter

What are the areas of the CNS that contain a high proportion of axons called?

Nodes of Ranvier

What are the gaps in the myelin sheath?

1. Astrocytes 2. Oligodendrocytes 3. Microglia

What cell types are neuroglial cells located within the central nervous system?

1. an excitable cell 2. an irritable cell

What is a cell that can change its membrane potential in response to stimulation classified as?

Cholinergic

What is a neuron classified as if it uses acetylcholine as its neurotransmitter?

It returns to its resting potential.

What is happening when a cell undergoes repolarization?

Action potential

What is it called when there is a change in the membrane potential that is propagated or regenerated down the length of an axon?

Spatial summation occurs when synaptic potentials that originate in different locations summate within a single neuron.

What is spatial summation in neurons?

Synapse

What is the functional connection between a neuron and an effector celled?

cell body

What is the part of the neuron that contains the nucleus and is responsible for the production of most of the cell's macromolecules?

The resting membrane potential

What is the potential difference in voltage across the membrane of a resting cell called?

synaptic cleft

What is the space between the presynaptic cell and the postsynaptic cell called?

1. Neuromuscular junction 2. Myoneural junction

What is the specialized name for the synapse between a neuron and a muscle cell?

Brain & Spinal cord

What structures are part of the central nervous system?

Synaptic vesicles

What structures store the neurotransmitter molecules in the presynaptic neuron endings?

Oligodendrocytes

What type of cells form the myeline sheaths around axons of the central nervous system?

repolarization

When a cell returns to its resting potential, the cell is undergoing _____.

convergence

When a number of different axons synapse on a single postsynaptic neuron, it allows this neuron to integrate the input of the group of presynaptic neurons, this is called _____ of neural pathways.

divergence

When a single neuron has collateral axonal branches that synapse with a number of different neurons, this is called _____ of neural pathways.

depolarized

When a stimulation causes positive charges to flow into the cell and the membrane potential of the cell becomes more positive, the cell has ______.

more

When ion channels are open, the plasma membrane is _____ permeable than when the channels are closed.

1. Schwann cells 2. Satellite cells

Which cell types are neuroglial cells located within the peripheral nervous system?

Electrically

_____ coupled cells pass impulses from one cell to the next with out interruption through gap junctions.

Gap

_____ junctions are water filled channels of connexin proteins through which ions can pass from one cell to another.

Catecholamines

______ are subclass of monoamines derived from tyrosine that include dopamine, norepinephrine and epinephrine.

Dendrites

______ are thin branching processes that extend from the cytoplasm of the cell body.