CHAPTER 11: Functional Organization of Nervous Tissue

Once stimulated, a single action potential ______.

travels only a short distance before stimulating another action potential

The entry of calcium into the synaptic knob triggers ______.

exocytosis of neurotransmitter

During an EPSP, an influx of ______ occurs.

sodium

Which of the following events is NOT a characteristic of an action potential?

As Na+ enter, the inside of the plasma membrane becomes more negative.

Which type of neuroglia helps promote and regulate synapse formation?

Astrocyte

Explain why Na+ has little effect on establishing the resting membrane potential?

At rest, the membrane is relatively impermeable to Na+ because there are few Na+ leak channels.

Which statement below best describes why Na+ is highly concentrated outside of neurons and K+ is concentrated within neurons?

Na+ and K+ are actively pumped across the membrane in opposite directions by Na+/K+ pumps utilizing ATP.

A period of time when a cell cannot respond again to an electrical stimulus is the __ refractory period.

absolute

Identify why the membrane becomes hyperpolarized following the repolarization phase of an action potential.

Voltage-gated K+ channels remain open for a short period of time after reaching RMP; allowing K+ to diffuse out of the cell.

The nervous system transfers information from one part of the body to another by using _____.

action potentials

Traveling waves of excitation moving down an axon are referred to as ______.

action potentials

Entry of ______ ions into the synaptic knob triggers exocytosis of neurotransmitters.

calcium

Large, negatively charged proteins inside the cell _____ readily diffuse across the neuron membrane.

cannot

Neurotransmitter receptors at the postsynaptic membrane act as ________-regulated ion gates.

chemical or ligand

The cells that are general support cells for neurone in the brain and spinal cord are ______ cells.

glial

When the voltage of a plasma membrane shifts from +35 mV towards 0 mV, the neuron is __________.

repolarizing

Arrange the events of synaptic transmission in correct sequence. (1) Na+ diffuses into the cell and cause a local potential (2) Neurotransmitter binds with receptor on postsynaptic cell (3) Neurotransmitter diffuses across the synaptic cleft (4) Membrane permeability to Na+ on postsynaptic cell increases (5) Action potential causes release of neurotransmitter

5, 3, 2, 4, 1

Ligand-gated ion channels bind ______ that have diffused across a synaptic cleft.

neurotransmitters

Synaptic vesicles within synaptic knobs contain chemicals called ________.

neurotransmitters

An action potential

occurs when the local potential reaches threshold level

Glial cells that form myelin sheaths within the CNS are the ________.

oligodendrocytes

The glial cells that form myelin sheaths in the brain and spinal cord are ______.

oligodendrocytes

When opposite charges are arranged on opposing sides of a membrane, the membrane is said to be ______.

polarized

The plasma membrane has opposite charges arranged across the membrane and is thus said to be ________.

polarized or polar

Inside excitable cells at rest, you'll find high concentrations of ______ ions and negatively charged proteins.

potassium

When considering permeability to sodium and potassium, neuronal plasma membranes have a higher permeability to ______.

potassium

The purpose of the absolute refractory period is to _____.

prevent action potentials from being generated in reverse direction

An unmyelinated axon will conduct action potentials more ______ than a myelinated axon.

slowly

The ion ______ is more concentrated in the extracellular fluid.

sodium

The junction between two neurons is a __________.

synapse

The small, membrane-bound organelles that are found in the presynaptic terminals and which contain neurotransmitters are called _____.

synaptic vesicles

The intracellular fluid is considered to be electrically neutral because ______.

there are the same number of positively and negatively charged ions.

In order for an action potential to occur, a minimum membrane potential called the ________ must be reached.

threshold

In order for local potentials to trigger an action potential, the membrane must reach a level called the ______.

threshold

In order for local potentials to trigger an action potential, the membrane must reach a level called the __________.

threshold??

The sciatic nerve is composed of the

tibial nerve and common fibular nerve

Axons contain

trigger zone

Identify the type of synapse that includes a presynaptic cell, synaptic cleft, and postsynaptic cell.

Chemical

Predict the effects on membrane potential if the membrane's permeability to Cl- increases.

Cl- would diffuse into the cell, causing a hyperpolarization.

Predict the effect of increasing a membrane's permeability to K+ on membrane potential.

K+ will diffuse out of the cell, causing a hyperpolarization.

The sodium-potassium pump is responsible for what portion of the resting membrane potential?

Less than 15mV

Frank has a microbial infection attacking his brain. Which cell type would you expect to proliferate and be most active during this time?

Microglia / microgilia cells

Select the item that best defines the soma of a neuron. 1. The myelin wrapper around an axon 2. The extension carrying information into a neuron cell body 3. The cell body of neuron 4. The extension carrying information out of a neuron cell body

The cell body of neuron

An increase in a membrane's permeability to Na+ will result in ________ of the membrane.

depolarization or depolarisation

When the resting membrane potential shifts to a more positive value, this is referred to as ________.

depolarization or depolarisation

When the neuron membrane becomes less negative than the resting membrane potential, it is said to be ______.

depolarized

When the neuron membrane becomes more positive than the resting membrane potential, it is said to be ______.

depolarized

Synapses in which gap junctions allow ions to diffuse quickly from cell to cell are called ______ synapses.

electrical

Synapses in which gap junctions allow ions to diffuse quickly from cell to cell are called __________ synapses.

electrical

Neuroglial cells that produce cerebrospinal fluid are ______.

ependymal cells

True or false: During the absolute refractory period a neuron will be re-stimulated if it reaches threshold.

false

Action potentials are conducted more rapidly when transmission is

from node to node on a myelinated axon.

The beginning of the axon is called the ________ segment.

initial

axillary nerve

innervates deltoid and teres minor

A negative membrane potential indicates that the area with a more negative charge is on the ______ of the membrane.

inside

Potassium ions and negatively charged proteins are more concentrated ______ the cell.

inside

Gaps or interruptions in the myelin sheath are called __________.

internodes

A change in resting membrane potential confined to a small area is called a/an __________ potential.

local

Correctly match the parts of a neuron with the correct description. Instructions 1. Soma 2. Nissl body 3. Collaterals 4. Presynaptic terminal 5. Axoplasm

1. Also known as the cell body 2. Rough endoplasmic reticulum of a neuron responsible for protein synthesis 3. Branches of an axon 4. Enlarged end of axon containing vesicles filled with neurotransmitters 5. Cytoplasm of an axon

Correctly pair the parts of a neuron with the correct description. 1. Cell Body 2. Axon 3. Dendrite 4. Nissl Body 5. Collaterals

1. Enlarged portion of a neuron that contains the nucleus and other organelles 2. Process of a neuron that transmits action potentials away from the cell body 3. Process of a neuron that receives stimuli and generates local potentials 4. Rough endoplasmic reticulum of a neuron responsible for protein synthesis 5. Branches of an axon

Click and drag on elements in order Indicate the correct order of events that occur during a single action potential.

1. Local potential decreases membrane potential 2. threshold is reached 3. Depolarization spike occurs 4. repolorization occurs 5. afterpotential occurs 6. resting membrane potential is re-established

Match the parts of a neuron with the appropriate description. 1. Axon 2. Dendrite 3. Collaterals 4. Presynaptic terminal 5. Axon hillock

1. Process of a neuron that transmits action potentials away from the cell body 2. Process of a neuron that transmits action potentials towards the cell body 3. Branches of an axon 4. Enlarged end of axon containing vesicles filled with neurotransmitters 5. Site where the axon originates

During an action potential, an increase in membrane permeability to Na+ leads to a(n) _______ followed by an increase in permeability to K+ that leads to a(n) ______ of the membrane and a slight afterhyperpolarization.

Blank 1: depolarization Blank 2: repolarization

Sodium is more concentrated in the _____ fluid than in the _____ fluid.

Blank 1: extracellular Blank 2: intracellular

Potassium has a much higher concentration in the _____ fluid than in the _____ fluid.

Blank 1: intracellular Blank 2: extracellular

When the membrane potential decreases, the inside of the membrane becomes _____ negative. This is called ______.

Blank 1: less Blank 2: depolarization

The plasma membrane is more permeable to _____ and chloride and much less permeable to _____.

Blank 1: potassium Blank 2: sodium

Select the components of the central nervous system. 1. Spinal cord and spinal nerves 2. Ganglia and nerves 3. Brain and spinal cord 4. Muscle and glands

Brain and spinal cord

True or false: Once achieved, a single action potential can travel the distance of the entire axon of the neuron.

False

When Na+ channels open, what happens to the Na+ ions?

Na+ diffuses into the cell.

Explain why Na+ ions diffuse into the neuron when the Na+ channels open.

Na+ is more concentrated outside the cell than inside; hence, the concentration gradient causes diffusion into the cell.

Predict the effect of increasing a membrane's permeability to Na+ on membrane potential.

Na+ will diffuse into the cell, causing a depolarization.

What is responsible for concentrating K+ inside and Na+ outside of neurons?

Na+-K+ pumps

What is the name of the gaps found between segments of myelin along an axon?

Nodes of Ranvier

Identify the functions of astrocytes. Select all that apply. 1. Regulation of synaptic activity 2. Promotion of the formation of synapses 3. Formation of myelin sheaths in the CNS 4. Synthesis of neurotransmitters 5. Production and circulation of cerebrospinal fluid

Regulation of synaptic activity Promotion of the formation of synapses Synthesis of neurotransmitters

The sodium-potassium pump moves the ions in which direction?

Sodium(Na+) out of the cell and potassium(K+) into the cell

Which term best describes the concentration gradients for sodium and potassium on an excitable cell?

Steep

What ensures the one-way propagation of action potentials along an axon?

The absolute refractory period

Explain the importance of the absolute refractory period in the propagation of action potentials.

The absolute refractory period ensures one-way propagation of action potentials.

Explain why the propagation of action potentials occurs in one direction.

The absolute refractory period prevents the generation of an action potential in the reverse direction.

In an action potential, what happens to potassium ions during repolarization?

They leave the cell.

After a nerve cell responds to a stimulus, the period of time when the cell cannot respond again, regardless of the strength of stimulus, is called the ________ refractory period.

absolute

Branched cytoplasmic extensions of the neuron that receive input and transmit signals toward the cell body are ________.

dendrites

Branched cytoplasmic extensions of the neuron that receive input and transmit signals toward the cell body are __________.

dendrites

The highly branched cytoplasmic extensions of a neuron cell body that are specialized to receive input and conduct signals toward the cell body are called ______.

dendrites

The speed of an action potential along myelinated axons is ______ the speed of an action potential along an unmyelinated axon.

faster than

Electrical synapses allow ions to diffuse quickly from cell to cell via ______.

gap junctions

A protein channel that opens or closes in response to a stimulus would be classified as a ______ channel.

gated

Some protein channels in a cellular membrane are able to open or close in response to stimuli; because of this characteristic, these channels are called ______ channels.

gated

An axon hillock transitions into the ______ segment of an axon.

initial

A neuron with one axon and multiple dendrites is called a ________ neuron.

multipolar

Action potentials (nerve messages) are able to travel faster along ______ axons.

myelinated

Action potentials are conducted more rapidly along ______ axons.

myelinated

If the area just inside the membrane of a cell is more negative than the outside, the resting membrane potential will have a ______ value.

negative

The category of cells of the nervous system that support and protect neurons are called _________ cells.

neuroglia, glia, or glial

The general class of cells in the nervous system that protect nerve cells and help in their functioning are called ________ cells.

neuroglial, glia, glial, or neuroglia

The intracellular fluid has essentially the same number of positive and negative charges and is therefore electrically ________.

neutral or balanced

During an action potential, repolarization is due to ________ ions leaving the cell.

potassium, K, or K+

The ion that is in a higher concentration in the intracellular fluid compared to the extracellular fluid is ________.

potassium, K, or K+

A cell is not stimulated but it does contain an electrical charge difference across its membrane. This charge difference is its ______.

resting membrane potential

A junction between a neuron and another cell is called a(n) ________.

synapse

True or false: There is a significant difference in concentration between the intracellular concentration of sodium and the extracellular concentration of sodium.

true

True or false: Three factors that generate the resting membrane potential include diffusion of ions across a membrane, a selectively permeable membrane, and the electrical attraction of oppositely charged ions.

true

What type of potential is irreversible?

Action potential

What type of potential is non-decremental?

Action potential

Which of the following situations occurs in electrically excitable cells?

Depolarization causes voltage-gated Na+ channels to open.

Hydrocephaly is a condition whereby cerebrospinal fluid (CSF) accumulates around the brain. Which supportive cells continue CSF production despite it backing up in the subarachnoid space?

Ependymal cells

On myelinated axons, small gaps exist between adjacent Schwann cells; these gaps are known as ________ of ________.

Nodes of Ranvier

The gaps found between Schwann cells forming the myelin are referred to as the ________ of ________.

Nodes of Ranvier

If five action potentials arrive at the same synapse in very close succession, which of the following would occur?

Temporal summation occurs.

Which factors contribute to the generation of the resting membrane potential? Select all that apply. 1. The movement of water across the membrane into a region of higher concentration of solute 2. The electrical attraction of cations and anions to each other 3. Selective permeability of the membrane, allowing some ions to pass more easily than others 4. Diffusion of ions down their concentration gradients through the membrane

The electrical attraction of cations and anions to each other Selective permeability of the membrane, allowing some ions to pass more easily than others Diffusion of ions down their concentration gradients through the membrane

Identify the statements that are true regarding the nature of the large proteins found within neurons. Select all that apply. 1. They are negatively charged. 2. They act as receptors to neurotransmitters. 3. They do not readily diffuse through the membrane. 4. They are synthesized inside the cell.

They are negatively charged. They do not readily diffuse through the membrane. They are synthesized inside the cell.

When a neurotransmitter binds to its receptor and increases the permeability of the postsynaptic membrane to Na+

an excitatory postsynaptic potential (EPSP) will result.

The function of acetylcholinesterase is to

breakdown acetylcholine in the synapse.

Synapses in which neurotransmitters are released are called ______ synapses.

chemical

An increase in a membrane's permeability to Cl- will result in ______ of the membrane.

hyperpolarization

An increase in a membrane's permeability to K+ will result in ______ of the membrane.

hyperpolarization

The slow closing of voltage-gated potassium channels is the cause of ______.

hyperpolarization

At rest, the neuron plasma membrane is relatively ______ to Na+; therefore, Na+ does not influence the resting membrane potential very much.

impermeable

During the absolute refractory period, the cell

is insensitive to further stimulation

A synapse is a ______.

junction between two cells

A hyperpolarizing local potential will make the neuron ______ likely to generate a nerve impulse.

less

An inhibitory local potential will make the neuron ______ likely to generate a nerve impulse.

less

A multipolar neuron has ______ dendrite(s).

many

Rapid removal or destruction of neurotransmitter in the synaptic cleft

may affect the ability of the postsynaptic membrane to generate action potentials.

The sodium-potassium pump plays a _____ role in maintaining resting membrane potential.

minor

An excitatory local potential will make the neuron ______ likely to generate a nerve impulse.

more

The role of the Na+-K+ pump in membrane potential regulation is that it ______.

reestablishes correct ion distribution, compensating for ion leakage

A period of time after a nerve cell has responded to a stimulus in which it cannot be re-excited by a threshold stimulus is called a(n) ______ period.

refractory

A nerve cell can only respond to an unusually strong stimulus during the ______ refractory period.

relative

After a nerve cell responds to a stimulus, the period of time when the cell cannot respond again except to an unusually strong stimulus is called the ________ refractory period.

relative

The difference in electrical charge across the plasma membrane in an unstimulated cell is called the ________ ________ potential.

resting membrane

Excitatory postsynaptic potentials are due to the entry of the electrolyte ________ through gated ion channels in the postsynaptic membrane.

sodium, Na, or Na+

The cell body of a neuron is also known as the _______.

soma, neurosoma, or perikaryon