Ch 12 Nervous Tissue

Place these events into the order in which they occur during a single action potential.

1. Local potential depolirizes mebrane 2. Threshold is reached 3. Depolarization 4. Repolarization 5. Hyperpolarization

Internodes

Between the nodes of Ranvier are myelin-covered segments of axon encircled by Schwann cells. Which term refers to these segments?

Neurons that have one axon and one dendrite, such as olfactory cells, certain neurons of the retina, and sensory neurons of the inner ear, are classified as which of the following?

Bipolar

Resting membrane potential

Both types of voltage-gated channels are closed. Both types of voltage-gated channels are closed.

axon collateral

Branch that originates from an axon

Repolarization begins

Choice, Voltage-gated Na+ channels inactivate; voltage-gated K+ channels remain open longer Voltage-gated Na+ channels inactivate; voltage-gated K+ channels remain open longer

axoplasm

Cytoplasm of the axon

Which are characteristics of local potentials?

Decremental Graded

During which part of the action potential do most voltage-gated sodium channels open?

Depolarization

List the fundamental physiological properties of neurons.

Excitability, conductivity, secretion

Schwann cells

In the PNS; form neurilemma around all PNS fibers and myelin around most of them; aid in regeneration of damaged nerve fibers.

satellite cells

In the PNS; surround somas of neurons in ganglia, provide electrical insulation, and regulate the chemical environment of neurons

anaxonic neuron

Neurons that have multiple dendrites but no axons, and which do not produce action potentials, are called ?

unipolar neuron

Neurons with a single process extending from the soma, such as the neurons that carry sensory signals to the spinal cord, are classified structurally as ______ neurons.

multipolar neuron

Neurons with numerous dendrites and a single axon are structurally classified as which of the following?

Which are names for the cell body of a neuron?

Neurosoma, Soma

Which are usually found inside the cell body (or soma) of a mature neuron?

Nucleus Mitochondria Rough endoplasmic reticulum

Which three factors contribute the most to the formation of the negative resting membrane potential?

Open leak channels in the plasma membrane allow K+ to diffuse across the membrane, down its concentration gradient. Outward K+ diffusion causes positive and negative charges to accumulate on either side of the membrane where they attract each other. There is a higher concentration of K+ in the intracellular fluid as compared to the extracellular fluid.

axolema

Plasma membrane of the axon

Which term is used to refer to a cell membrane across which there is a separation of electrical charge, so that one side is more positive and the other side is more negative?

Polarized

An electrical potential is a form of what type of energy?

Potential energy

Which are functions of astrocytes?

Regulate chemical composition of tissue fluid Convert blood glucose to lactate for neurons to use for fuel Secrete nerve growth factors Form blood-brain barrier

Which type of glial cell aids in regeneration of damaged peripheral nerve fibers by forming a regeneration tube to help reestablish the former connection?

Schwann cells

Carry signals to spinal cord and brain

Sensory (afferent) neurons do which of the following?

Neurons

Sensory, association and motor are the three classes of what?

Choose the characteristics of neuroglia.

They bind neurons together and provide a supportive scaffold. They protect the neurons and help them function.

Which statements are true about Schwann cells?

They form the myelin sheath in the PNS. They form the neurilemma. They assist in the regeneration of damaged nerve fibers.

At rest, K+ diffuses out of the cell through leak channels, resulting in a slight local accumulation of positive charge on the outside of the membrane (due to excess K+) and a slight local accumulation of negative charge on the inside of the membrane (due to decreased K+).

This describes the basis of the resting membrane potential

visceral motor

Together, the sympathetic and parasympathetic nervous systems make up the entirety of which division of the nervous system?

True or false: As long as there is an electrical potential across a cell membrane, we say that the membrane is polarized.

True

False

True or false: Damaged nerve fibers in the CNS regenerate very fast whereas damaged nerve fibers in the PNS never regenerate.

Which lists the structural categories of neurons?

Unipolar, bipolar, anaxonic, and multipolar

Depolarization begins

Voltage-gated Na+ channels open; voltage-gated K+ channels open more slowly

Central and peripheral nervous systems

What are the two major anatomical subdivisions of the nervous system?

To increase the speed of signal conduction in the axon

What is the primary function of the myelin sheath?

It is used to renew worn-out axoplasmic components in mature neurons. It works in a stop-and-go fashion.

Which describes slow axonal transport?

sympathetic

Which division inhibits digestion?

Presence of myelin Diameter of axon

Which factors influence the speed of nerve signal conduction?

Conductivity

Which fundamental physiological property of neurons allows them to send signals quickly over long distances?

Ependymal cells

Which glial cell produces and helps circulate cerebrospinal fluid?

Satellite cell

Which neuroglial cell is found in the peripheral nervous system?

axon terminal buttons

Which term applies to the small swellings at the distal end of the axon of a neuron that contain synaptic vesicles?

Nodes of Ranvier

Which term refers to the gaps between segments of myelin along an axon?

Neurilemma

Which term refers to the outermost layer of myelin, containing the nucleus and cytoplasm of the Schwann cell?

Axonal transport

Which term refers to the passage of proteins, organelles and other materials along an axon?

Sensory Divison (afferent)

Which terms refers to the part of the PNS that carries signals from various receptors to the CNS?

Sensory division

Which terms refers to the part of the PNS that carries signals from various receptors to the CNS?

Nervous system and endocrine system

Which two organ systems are primarily responsible for coordinating the other bodily systems so as to maintain homeostasis?

Interneuron

Which type of neuron lies entirely within the CNS and carries out the integrative function of the nervous system?

Fast axonal transport

Which type of transport is used to move mitochondria, synaptic vesicles, and small molecules such as glucose toward the distal end of an axon?

satellite

______ cells are glial cells in the peripheral nervous system that surround somas of neurons in the ganglia, provide electrical insulation, and regulate the chemical environment of neurons.

The refractory period in which no stimulus of any strength will trigger a new action potential is the ______ refractory period.

absolute

Movement away from the neuron cell body toward an axon ending is called ______ transport.

anterograde

Dendrites

are the processes of a neuron that usually receive signals from other neurons.

Which best describes an electrical potential?

A form of potential energy that can produce current

Which is most likely to be the resting membrane potential of a neuron?

-70 mV

List in chronological order the stages of regeneration of a nerve fiber.

1. Degeneration of the axon and myelin distal injury 2. Swelling of soma; dispersed of Nissl bodies 3. Sprouting of axon growth processes 4.growth process enters regeneration tube 5. Reestablishment of synaptic contact

axon hillock

A mound located on one side of the soma from which the axon originates

A negative membrane potential indicates which of the following?

A negative membrane potential indicates which of the following?

The all-or-none law of action potentials states which of the following?

A neuron will fire at maximum voltage if a stimulus depolarizes it to threshold.

biopolar neuron

A neuron with one axon and one dendrite is structurally classified as a

Which best describes signal conduction in unmyelinated axons?

A wave of depolarization opens more voltage-gated channels immediately distal to the action potential.

Which term describes all neurons that carry signals towards the CNS?

Afferent

Which are properties of action potentials?

All or none Nondecremental (signal maintains amplitude) Self-propagating

oligodendrocytes

In the CNS, myelin is produced by glial cells called

Ependymal cells

In the CNS; line cavities of the brain and spinal cord; secrete and circulate CSF

Microglia

In the CNS; phagocytize microorganisms, foreign matter, and dead nervous tissue

Electrical currents in neurons are due primarily to the flow of which of the following through gated channels?

Ions such as sodium and potassium

Which are true regarding the Na+-K+ pump?

It helps maintain the proper ion distribution across the membrane, compensating for ion leakage. It accounts for about 70% of the energy (ATP) required by the nervous system.

Which correctly describe axonal transport?

It involves transport of proteins within the axon (i.e. synaptic knob enzymes or proteins that maintain the axolemma). It is bidirectional (retrograde and anterograde transport).

Which of the following contributes to the development of the resting membrane potential in neurons?

K+ is more concentrated in the ICF than in the ECF.

afferent neurons

Neurons that convey information to the CNS (indicated by the arrow labeled A) are called sensory___________neurons

What creates electrical currents in neurons?

Movement of ions through channels

Which is true about a neuron with a large diameter, myelinated axon as compared to a neuron with a small diameter, unmyelinated axon?

Signal conduction will be faster

Why is sodium more concentrated in the ECF than in the ICF of most neurons?

Sodium is actively pumped out of the cell by transporter proteins.

Which division inhibits digestion?

Sympathetic

peripheral nervous system

Taken together, the sensory and motor subdivisions make up which of the following?

neurosoma, dendrites

The ______ (the cell body of a neuron) gives rise to branch-like processes called ______, which are the primary sites for receiving signals from other neurons.

central and peripheral

The brain and spinal cord are components of the ______ nervous system, while the nerves and ganglia are components of the ______ nervous system.

efferent

The motor division is also called the ______ division.

Which best describes an electrical current?

The movement of charged particles like ions

Ganglia

The plural form of ganglion is ______.

Which of the following statements are true about sodium?

The resting plasma membrane is much less permeable to Na+ than to K+. Na+ is about 12 times as concentrated in the ECF as in the ICF.

Somatic and Visceral

The sensory and motor divisions of the peripheral nervous system are further split into which two subdivisions?

Accelerating or decreasing heartbeat Stimulating smooth muscle Controlling gland secretion

The visceral motor division of the PNS is also called the autonomic division. Which of the following are functions of this division?

Which term refers to the flow of charged particles from one point to another?

current

The knotlike swelling in a nerve where neuron cell bodies are found is called a(n)

ganglion

The myelin sheath is composed mostly of which of the following?

lipids

Which term refers to decremental changes in electrical potential along a dendrite or the soma?

local potential

What are the effectors of motor neurons?

muscles and glands cells

motor or efferent neurons

neurons carry signals away from the CNS and they lead to effectors (muscle and gland cells).

Which ion has the greatest influence on the resting membrane potential of most neurons?

pottassium

glial cells

protect the neurons and help them function.

Afferent neurons are?

sensory neurons

What are the two divisions of the visceral motor division?

sympathetic and parasympathetic

An axon lacking a myelin sheath is said to be ______.

unmyelinated