Nervous System

The central nervous system (CNS) refers to the _____ and _____.

Brain; spinal cord

The peripheral nervous system (PNS) refers to the _____, _____, and _____ found _____.

Cranial nerves; spinal nerves; ganglia; outside of the CNS

Interneurons refer to _____ neurons located entirely within the _____.

Multi-polar; CNS

Sensory/_____ neurons refer to neurons that transmit impulses from _____ to the _____.

Afferent; sensory receptors; CNS

Motor/_____ neurons refer to neurons that transmit impulses from the _____ to _____.

Efferent; CNS; effectors

Nerves refer to a cable-like collection of _____ in the _____. They may be _____, meaning they contain both _____ and _____ fibers.

Axons; PNS; mixed; sensory; motor

Somatic motor nerves refer to nerves that stimulate _____.

Skeletal muscle

Autonomic motor nerves refer to nerves that stimulate _____, _____, and _____.

Smooth muscle; cardiac muscle; glandular secretion

A ganglion refers to a grouping of neuron _____ in the _____.

Cell bodies; PNS

A nucleus refers to a grouping of _____ in the _____.

Cell bodies; CNS

A tract refers to a grouping of _____ that interconnect regions within the _____.

Axons; CNS

The peripheral nervous system can be divided into the _____/_____ division and the _____/_____ division.

Sensory; afferent; motor; efferent

The sensory/afferent division of the _____ contains _____ and _____ sensory nerve fibers that conduct impulses from _____ to the _____.

Peripheral nervous system; somatic; visceral; receptors; CNS

The motor/efferent division of the _____ contains _____ nerve fibers that conduct impulses from the _____ to _____.

Peripheral nervous system; motor; CNS; effectors

The motor/efferent division of the _____ can be divided into the _____ nervous system and the _____ nervous system.

Peripheral nervous system; somatic; autonomic

The somatic nervous system of the _____/_____ division of the _____ contains _____ nerve fibers that conduct impulses from the _____ to _____.

Motor/efferent; peripheral nervous system; voluntary; CNS; skeletal muscle

The autonomic nervous system of the _____/_____ division of the _____ contains _____ nerve fibers that conduct impulses from the _____ to _____, _____, and _____.

Motor/efferent; peripheral nervous system; involuntary; CNS; cardiac muscle; smooth muscle; glands

The autonomic nervous system of the _____/_____ division of the _____ can be divided into the _____ division and _____ division.

Motor/efferent; peripheral nervous system; sympathetic; parasympathetic

The sympathetic division of the _____ mobilizes body systems during _____.

Autonomic nervous system; activity

The parasympathetic division of the _____ promotes house-keeping functions during _____.

Autonomic nervous system; rest

During the _____ response, sympathetic activity dominates. During the _____ response, parasympathetic activity dominates.

Fight-or-flight; rest-and-digest

The primary functions of the nervous system are _____, _____, and _____ in nature.

Sensory; integration; motor

The sensory function of the nervous system refers to how _____ detect external or internal _____ before relaying information to the _____ and _____ for _____.

Sensory receptors; stimuli; brain; spinal cord; integration

The integration function of the nervous system refers how the _____ analyzes _____ information before _____.

CNS; sensory; deciding the appropriate response

The motor function of the nervous system refers to how motor information is conveyed from the _____ to the _____ and _____ of the _____ to the appropriate _____ (_____ and _____).

CNS; cranial nerves; spinal nerves; PNS; effectors; muscles; glands

The nervous tissue is composed of two types of cells, neurons that _____ but generally cannot _____, and glial cells that _____ and _____ but cannot _____.

Conduct impulses; divide; support the neurons; divide; conduct impulses

Brain tumors typically originate from _____ because they are capable of _____.

Glial cells; dividing

Neurons represent the _____ and _____ units of the nervous system.

Structural; functional

General functions of a neuron include responding to chemical and physical _____, conducting _____ impulses, releasing _____ regulators, and enabling the perception of the _____, _____ and _____, and control over _____ and _____.

Stimuli; electrochemical; chemical; senses; learning; memory; muscles; glands

Neurons vary in size and shape, but they all have a _____, _____, and _____.

Cell body; dendrites; axons

The cell body of a neuron contains the _____ and _____. They cluster in groups called nuclei in the _____ and ganglia in the _____.

Nucleus; other organelles; nuclei; ganglia

The dendrites of a neuron are responsible for _____ and conducting _____ towards the _____. They help increase the _____ of a neuron.

Receiving impulses; graded potentials; cell body; surface area

The axon of a neuron conducts _____ away from the _____.

Action potentials; cell body

Within a neuron, dendrites are responsible for receiving the _____. The cell body is responsible for _____. The presynaptic axon terminal is responsible for releasing the _____ into the _____ via _____ towards the _____.

Input signal; integration; output signal; synaptic cleft; neurotransmitters; postsynaptic dendrite

A synapse refers to the region where an _____ communicates with a _____.

Axon terminal; post-synaptic target cell

The myelin sheath functions in _____, helping to increase the speed of conduction of _____.

Electrical insulation; action potentials

Myelin sheaths are found in both the CNS (where they are known as _____) and the PNS (where they are known as _____).

Schwann cell; oligodendrocyte

Nodes of Ranvier refer to _____.

Gaps in the myelin sheath

Myelin sheaths collectively make up _____.

White matter

Plasticity refers to the _____.

Ability to change throughout life

Repair refers to _____.

Generation after damage

Regeneration in the _____ occurs if the _____ is intact and the _____ remain active, as they help form the _____ that guides and stimulates regrowth of the _____.

PNS; cell body; Schwann cells; regeneration tube; axon

Little to no regeneration occurs in the _____ due to inhibitory proteins released by _____, the absence of _____, and _____ formation.

CNS; glial cells; growth-stimulating cues; scar tissue formation

The two main types of ion channels are _____/_____ channels, which are _____, and _____ channels, in which _____.

Leakage/ungated; always open; gated; part of the protein changes shape to open/close the channel

The three types of gated channels are _____, _____/_____, and _____ channels.

Mechanically-gated; chemically-gated/ligand-gated; voltage-gated

Mechanically-gated ion channels open or close in response to mechanical forces like _____, _____, _____, or _____.

Touch; pressure; stretching; vibration

Chemically-gated/ligand-gated ion channels open or close in response to the _____ (e.g. _____).

Binding of a specific ligand/chemical; neurotransmitters

Voltage-gated channels ion open and close in response to changes in _____/voltage.

Membrane potential

When gated ion channels open, they change membrane permeability, allowing ions to diffuse along their _____, causing changes in _____. This allows for _____ communication, and is common in _____ tissues like _____ and _____ tissue.

Electrochemical gradient; resting membrane potential; electrical; excitable; nervous; muscle

Voltage refers to an _____. Voltage is measured in _____ or _____.

Electrical potential difference between opposite charges that are separate from each other; volts; millivolts

Ion currents refer to the _____.

Flow of ions

Membrane potential refers to the _____/_____ that exists across the _____ of a cell.

Electrical potential difference/voltage; plasma membrane

The resting membrane potential of a neuron at rest is approximately _____, in which the cytoplasmic side of the membrane is _____ charged relative to the outside.

-70 mv; negatively

Resting membrane potential is determined by the _____, differences in _____, and the action of _____.

Unequal distribution of ions in the extracellular fluid and cytosol; plasma membrane permeability; Na+/K+ ATPases

The unequal distribution of ions in the extracellular fluid and cytosol contributes to resting membrane potential because the _____ of the cell has relatively more _____-charged protein _____.

Inside; negatively; anions

Differences in plasma membrane permeability contribute to resting membrane potential because the membrane is about 40x more permeable to _____ than _____ due to the presence of more appropriate _____. This causes more _____ to diffuse out than _____ that diffuses in, causing the inside of the cell to become more _____.

K+; Na+; leakage channels; K+; Na+; negative

The action of the Na+/K+ ATPase pump contributes to resting membrane potential because it helps maintain Na+ and K+ _____, removing more _____ than _____ that enters the cell.

Electrochemical gradients; Na+; K+

Changes in membrane potential are used as _____ to receive, integrate, and send information. This property is known as _____ or irritability.

Signals; excitability

Membrane potential changes when the _____ of ions across the membrane changes or the membrane _____ to ions changes.

Concentration; permeability

Changes in membrane potential produce two types of signals: _____ and _____.

Graded potentials; action potentials

Graded potentials refer to _____ signals operating over _____ distances.

Incoming; short

Action potentials refer to _____-distance signals that occur over _____ that always have the same _____.

Long; axon; strength

At rest, a neuron is considered polarized when the inside is more _____ than the outside.

Negative

Depolarization refers to when the inside of the membrane becomes _____ than resting membrane potential, moving towards _____. This is considered _____, and occurs when _____ ions _____ the cell (usually _____).

Less negative; 0; excitatory; positive; enter; Na+

Repolarization refers to when the inside of the membrane _____.

Returns to resting membrane potential

Hyperpolarization refers to when the inside of the membrane becomes _____ than resting membrane potential. This is considered _____, and occurs when either _____ ions _____ the cell (usually _____) or _____ ions _____ the cell (usually _____).

More negative; inhibitory; positive; leave; K+; negative; enter; Cl-

Graded potentials refer to _____ signals to the _____ or _____ of _____ strength. These are _____-lived, _____ changes in membrane potential triggered by a stimulus (_____) that opens _____-gated ion channels. This can result in _____ or _____ depending on which ion channels opens. The stronger the stimulus, the more voltage changes and the farther current flows. If strong enough, graded potentials can reach the _____/_____ to produce an _____. Although current can flow, it dissipates quickly and _____ due to _____ and _____, making graded potentials more suitable for _____-distance communication.

Incoming; dendrites; cell body; variable; short; localized; neurotransmitters; ligand; depolarization; hyperpolarization; trigger zone/axon hillock; action potential; decays; current leak; cytoplasmic resistance; short

_____, also known as nerve impulses, are the principal way that neurons send signals and are used as a means of _____-distance communication.

Action potentials; long

Action potentials only occur in _____ cells and the _____ of neurons.

Muscle; axons

Action potentials consist of a brief reversal of membrane potential that results in ~100 mV of change. For an axon to fire, _____ must reach a _____ voltage to trigger an action potential.

Depolarization; threshold

T/F: All depolarization events produce action potentials.

False, e.g. subtreshold stimuli

At threshold, the membrane is _____ by about 15-20 mV, permeability to _____ increases, _____ exceeds _____, and a _____ feedback cycle begins.

Depolarized; Na+; Na+ influx; K+ efflux; positive

Action potentials do not _____ over distance as _____ do.

Decay; graded potentials

Action potentials are considered _____, meaning they either happen completely or not at all.

All-or-none

Because action potentials are all-or-none, once _____ has been reached, an action potential will happen. The _____ of the stimulus does not affect the _____ or _____ of the action potential, as it will always reach _____.

Threshold; size; size; duration; +30 mV

The 4 stages of an action potential are _____, _____, _____, and _____.

Resting; depolarization; repolarization; hyperpolarization

The resting state refers to the _____ stage of an action potential. During the resting state, all _____ Na+ and K+ channels are closed. _____ channels remain open to maintain _____.

First; gated; leakage; resting membrane potential

Depolarization refers to the _____ stage of an action potential. The depolarization stage is characterized by the _____. During this stage, _____ that reach the _____ bring the membrane to _____ (_____). This results in the _____ of _____-gated _____ channels, causing _____ to _____ the cell and resulting in a large action potential _____, with the membrane polarity jumping to _____.

Second; opening of Na+ channels; graded potentials; trigger zone; threshold; -55 mV; opening; voltage; Na+; Na+; enter; spike; +30 mV

Repolarization refers to the _____ stage of an action potential. The depolarization stage is characterized by the _____ and _____. At _____, _____-gated _____ channels _____ via _____, causing membrane permeability to _____ to decrease to the resting state and the action potential spike to _____. At the same time, _____-gated _____ channels _____, causing _____ to _____ the cell _____ its electrochemical gradient. At this point, the membrane returns to _____ (_____).

Third; closing of Na+ channels; opening of K+ channels; +30 mV; voltage; Na+; close; inactivation gates; Na+; stop rising; voltage; K+; open; K+; leave; down; resting membrane potential; -70 mV

K+ channels are generally _____ to open.

Slow

Hyperpolarization refers to the _____ stage of an action potential. During this stage, some _____ remain _____, allowing excessive _____. This causes hyperpolarization of the membrane, which refers to a _____ from resting membrane potential to about _____. At this time, _____ then _____, and _____ reset, allowing the cell to return to _____ via _____.

Fourth; voltage-gated K+ channels; open; K+ efflux; decrease; -90 mV; voltage-gated K+ channels; close; voltage-gated Na+ channels; resting membrane potential; Na+/K+ pumps

T/F: All action potentials are alike, independent of stimulus intensity.

True

The CNS distinguishes between weak stimuli and strong stimuli via the of _____ impulses, measured in _____, i.e. a stronger stimulus will result in _____.

Frequency; action potentials per second; more frequent action potentials

Voltage-gated Na+ channels have 2 gates. In the resting state, the activation gate is _____ and the inactivation gate is _____. In the depolarizing stage, the activation gate is _____ and the inactivation gate is _____. In the repolarization stage, the activation gate is _____ and the inactivation gate is _____. At some point during the repolarization stage and the hyperpolarization stage, the gates reset.

Closed; open; open; open; open; closed

Action potentials can only increase in _____ to a certain point, as there is a _____ after an action potential when the neuron cannot become excited again.

Frequency; refractory period

During the absolute refractory period, _____. This represents the time from the _____ until the _____. The absolute refractory period helps ensure that each action potential is an _____ event, and enforces the _____ transmission of nerve impulses.

Another action potential cannot fire; opening of the voltage-gated Na+ channels; resetting of all channels; all-or-none; one-way

The relative refractory period follows the _____. During this period, most _____ have returned to their resting state, with some _____ still open. At this point, _____ is occurring, and the threshold for an action potential is _____, but a _____ stimulus can still result in another action potential.

Absolute refractory period; Na+ channels; K+ channels; hyperpolarization; elevated; strong

The relative refractory period refers to some of the _____ stage and the _____ stage.

Repolarization; hyperpolarization

Propagation refers to the _____. The _____ at one location serves as the _____ stimulus for the next region, causing a _____ charge to spread along adjacent sections of the axon via _____. _____ flow cannot happen because _____ channels are _____.

Transmission of an action potential down the length of an axon; action potential; depolarization; positive; local current flow; backward; Na+; inactivated

T/F: Once initiated, an action potential is self-propagating.

True

The rate of action potential propagation depends on two factors: axon _____ (as axons that are _____ have less _____ to _____) and the degree of _____.

Diameter; larger; resistance; local current flow; myelination

Continuous conduction refers to a relatively _____ type of conduction that occurs in _____ axons. In continuous conduction, action potentials are produced down the _____.

Slow; non-myelinated; entire length of the axon

Saltatory conduction refers to a relatively _____ type of conduction that occurs in _____ axons. _____ function to _____ the axon and prevent a _____. In this type of conduction, _____ are located at _____, and so action potentials are only generated at _____, but _____.

Fast; myelinated; myelin sheaths; insulate; leakage of charge; voltage-gated Na+ channels; myelin sheath gaps; myelin sheath gaps; signals jump from gap to gap

Multiple sclerosis (MS) is a type of _____ disease that primarily affects young adults. MS is characterized by the destruction of _____ in the _____ when the _____ attacks _____, resulting in hardened lesions known as _____. These result in the _____ and eventual _____ of _____.

Autoimmune; myelin sheaths; CNS; immune system; myelin; scleroses; slowing; ceasing; impulse conduction

A synapse is the region where an _____ meets a _____. In the CNS, synapses occur from _____ to _____. In the PNS, synapses occur from _____ to _____ or _____.

Axon terminal; target cell; neuron; neuron; neurons; muscles; glands

Presynaptic cells refer to neurons that conduct impulses _____ the synapse, i.e. _____ information.

Towards; sending

Postsynaptic cells refer to neurons that conduct impulses _____ the synapse, i.e. _____ information. In the PNS, postsynaptic cells may be _____, _____, or _____.

From; receiving; neurons; muscle cells; gland cells

T/F: Most cells function as both presynaptic and postsynaptic cells.

True

Electrical synapses refer to a relatively _____ common type of synapse in which cells are joined by _____ that span both membranes and allow _____ (and therefore _____) to pass from one cell to other. These signals can be _____, which helps synchronize the activity of a network of cells. Electrical synapses are found in the _____, _____, between some neurons of the _____, and between _____ cells.

Less; gap junctions; ions; electrical currents; bi-directional; cardiac muscle; smooth muscle; brain; glial

Chemical synapses are a relatively _____ common type of synapse that are specialized for the release and reception of chemical _____. The _____ of the presynaptic neuron contains _____ that are filled with _____, which are received by the _____ of the postsynaptic neuron. These are normally found on a _____ or the _____. The pre- and postsynaptic neuron are separated by a fluid-filled _____.

More; neurotransmitters; axon terminal; synaptic vesicles; neurotransmitters; receptor region; dendrite; cell body; synaptic cleft