Chapter 11 Mastering A&P

the impulse would spread bidirectionally

Direct signaling involves the activation of G Proteins. Indirect signaling involves G Proteins. Direct signaling involves opening ion channels that affect the polarization of the membrane.

oligodendrocytes

hyperpolarization

ganglia

true

This allows for the efflux (diffusion out) of potassium ions, resulting in the repolarization of the cell.

nucleic acid

true Opening K+ or Cl- channels in a postsynaptic membrane, resulting in K+ efflux or Cl- influx, respectively, would induce hyperpolarization. As the membrane potential increases and is driven farther from the axon's threshold, the postsynaptic neuron becomes less and less likely to "fire," and larger depolarizing currents are required to induce an action potential (AP). Hyperpolarizing changes in potential are called inhibitory postsynaptic potentials (IPSPs).

Dendrites are the main receptive or input regions, providing an enormous surface area for receiving signals from other neurons.

active transport by the Na+-K+ pump Maintenance (and restoration) of the resting ion concentrations depends on the Na+-K+ pump. Once gated ion channels are closed, the combined action of the pump and ion leakage (particularly that of K+) establishes a resting membrane potential in a typical neuron of around âˆ'70 mV.

A neuron can have only one axon, but the axon may have occasional branches along its length. This is true; a neuron can have only one axon, but the axon may have occasional branches along its length.

generator potential

somatic nervous system The somatic nervous system is composed of somatic motor nerve fibers that conduct impulses from the central nervous system to skeletal muscles. It is often referred to as the voluntary nervous system because it allows us to consciously control our skeletal muscles.

The effect of a neurotransmitter is based on the properties of the receptor more than the neurotransmitter. This is true; also consider that in the neuromuscular junction, ACh receptors are excitatory, but in the heart muscle, ACh receptors are inhibitory.

voltage-gated channel

astrocytes

somatic nervous system

Na+ is used to repolarize the membrane. This is false. Initially, K+ leaves the cell through voltage-gated channels. As K+ leaves the cell, the inside of the cell becomes more negative, repolarizing the cell.

opening of voltage-gated Na+ channels The threshold value is the point at which voltage-sensitive Na+ channels open. This leads to the characteristic rapid depolarization phase of the action potential.

Release hormones into the bloodstream to communicate with other cells in the body. Hormones are released by endocrine organs. The nervous system does have some control over endocrine function, but the endocrine system is considered a separate signaling system

A single type of channel will open, permitting simultaneous flow of sodium and potassium.

sensory (afferent) division

excitatory postsynaptic potential An excitatory postsynaptic potential, a type of graded potential, occurs because of the influx of Na+ through chemically gated channels in the receptive region, or postsynaptic membrane, of a neuron. Graded potentials are generated by chemically gated channels, whereas action potentials are produced by voltage-gated channels.

motor fibers that conduct nerve impulses from the CNS to smooth muscle, cardiac muscle, and glands

astrocytes

acetylcholine

astrocytes Astrocytes are the most abundant and diversely functioning glial cells. Examples of their many functions include: anchoring neurons to capillaries, aiding in the exchanges between neurons and blood, guiding the migration of young neurons, and helping control the chemical environment around neurons.

frequency of action potentials

Touch stimulation of this sensory receptor will open the mechanically gated ion channels, but action potentials are still not initiated because propagation of an action potential requires the opening of voltage-gated Na+ channels. Propagation (spreading) of an action potential from the cell body to the axon hillock and eventually the axon terminals (synaptic knobs) requires the sequential opening of mechanically and voltage-gated ion channels. When the sequence is interrupted, the message cannot spread to the sensory regions of the central nervous system, causing numbness.

analyzes sensory information, stores information, makes decisions

association neuron

One EPSP fails to bring the cell to threshold. This statement is true, but summation considers the action of multiple synaptic potentials working on a cell simultaneously.

astrocytes

the myelin sheath

The neuron would be unable to repolarize. This is true; K+ is used to repolarize the membrane after Na+ rushes into the membrane.

it can have amplitudes of various sizes

the direction in which the nerve impulse travels relative to the central nervous system Functional classification groups neurons according to the direction in which the nerve impulse travels relative to the central nervous system. Based on this criterion, there are sensory neurons, motor neurons, and interneurons.

The dendrites provide a large surface area for connections from other neurons. Yes, because of the branching and extensive membrane surface area, there is a large amount of membrane dedicated to synapses with other neurons.

True

Na+ ions move into the axon; K+ ions move out.

Microglial cells are small and ovoid with relatively long "thorny" processes. Their processes touch nearby neurons, monitoring their health, and when they sense that certain neurons are injured or are in other trouble, the microglial cells migrate toward them. Where invading microorganisms or dead neurons are present, the microglial cells transform into a special type of macrophage that phagocytizes the microorganisms or neuronal debris.

sensory (afferent) division

True

They increase amplitude as they move away from the stimulus point.

movement and circulation of cerebrospinal fluid Yes, cilia are an indication that the cells they appear on are moving fluids past the surface of the cells.

parasympathetic division

voltage gated potassium channels

provide the defense for the CNS

ependymal cells

the sympathetic division of the autonomic nervous system The sympathetic division of the autonomic, or involuntary, nervous system consists of visceral motor nerve fibers that regulate the activity of smooth muscles, cardiac muscles, and glands. This division is responsible for generating actions required during activity.

One incoming axon triggers responses in ever-increasing numbers farther and farther along the circuit.

May be involved in complex, exacting types of mental processing.

Involved in control of rhythmic activities such as breathing.

Involved in activating fibers of a skeletal muscle such as the biceps muscle.

Different types of sensory input can have the same ultimate effect.

short distance depolarization

Schwann cells (also called neurolemmocytes) surround all nerve fibers in the PNS and form myelin sheaths around the larger fibers. Myelin protects and electrically insulates nerve fibers, and it increases the transmission speed of nerve impulses.

They are mitotic.