BIOL 251 - Ch 12

myelinated

Axons surrounded by a myelin sheath produced either by Schwann cells in the PNS or by oligodendrocytes in the CNS are said to be ____.

sensory and motor

The PNS is divided into ____ and ____ divisions

2 kg 3%

the nervous system is one of the smallest and yet the most complex of the 11 body systems - mass = - total percentage of body weight =

cytoplasm neuronal lysosomes

Aging neurons also contain lipofuscin - a pigment that occurs as clumps of yellowish brown granules in the ____ - Lipofuscin is a product of ____ ____ that accumulates as the neuron ages, but does not seem to harm the neuron.

axon collaterals

Along the length of an axon, side branches called ____ ____ may branch off, typically at a right angle to the axon.

ions rapidly; constant strength

An action potential - an electrical signal that propagates (travels) along the surface of the membrane of a neuron - It begins and travels due to the movement of ____ (such as sodium and potassium) between interstitial fluid and the inside of a neuron through specific ion channels in its plasma membrane - Once begun, a nerve impulse travels ____ and at a ____ ____

mitochondria, microtubules, and neurofibrils

An axon contains (3)

CNS or PNS function

Both neurons and neuroglia differ structurally depending on whether they are located in the ____ or the ____. These differences in structure correlate with the differences in _____ of the central nervous system and the peripheral nervous system

controlled conditions

Both the nervous and endocrine systems have the same objective: - to keep ____ ____ within limits that maintain life.

1. nerves 2. sensory receptors

Components of the PNS include (2)

1. chemical messengers 2. short, tapering and highly branched

Dendrites 1. The plasma membranes of dendrites (and cell bodies) contain numerous receptor sites for binding ____ ____ from other cells. 2. Dendrites usually are ____, ____, and ____ ____ 3. In many neurons the dendrites form a tree-shaped array of processes extending from the cell body

path; region

Each nerve follows a defined ____ and serves a specific ____ of the body

trigger zone

In most neurons, nerve impulses arise at the junction of the axon hillock and the initial segment, an area called the ____ ____, from which they travel along the axon to their destination.

sensory and motor neurons motor neurons multipolar

Interneurons or association neurons - mainly located within the CNS between ____ and ____ neurons - Interneurons integrate (process) incoming sensory information from sensory neurons and then elicit a motor response by activating the appropriate ____ ____. - Most interneurons are ____ in structure.

electrical excitability

Like muscle cells, neurons possess ____ ____ the ability to respond to a stimulus and convert it into an action potential.

phagocytes cellular debris microbes; nervous tissue

Microglial cells or Microglia - These neuroglia are small cells with slender processes that give off numerous spine-like projections. - Microglial cells or microglia function as ____. - They remove ____ ____ formed during normal development of the nervous system and phagocytize ____ and damaged ____ ____.

cell body dendrites axon

Most neurons have three parts: (3)

dendrites; axon brain spinal chord motor neurons

Multipolar neurons - usually have several ____ and one ____ - Most neurons in the ____ and ____ ____ are of this type, as well as all ____ ____

0.5 to 130

Nerve impulses travel these great distances at speeds ranging from ____ to ____ meters per second

1. smaller 2. 25 3. support, nourish, protect 4. interstitial fluid 5. divide

Neuroglia 1. ____ cells 2. greatly outnumber neurons—perhaps by as much as ____ times 3. Neuroglia ____, ____, and ____ neurons 4. maintain the ____ ____ that bathes them 5. Unlike neurons, neuroglia continue to ____ throughout an individual's lifetime

cellular components damaged axons

Newly synthesized proteins produced by Nissl bodies are used to - replace ____ ____, as material for growth of neurons - regenerate ____ ____ in the PNS.

smaller; processes myelin sheath

Oligodendrocytes - These resemble astrocytes but are ____ and contain fewer ____. - Processes of oligodendrocytes are responsible for forming and maintaining the ____ ____ around CNS axons.

ganglia neuronal cell bodies; interstitial fluid

Satellite Cells - These flat cells surround the cell bodies of neurons of PNS ____ - Besides providing structural support, satellite cells regulate the exchanges of materials between ____ ____ ____ and ____ ____.

trophic chemicals harmful agents rabies; herpes; polio

Substances that enter the neuron at the axon terminals are also moved to the cell body by fast retrograde transport. - These substances include ____ ____ such as nerve growth factor and ____ ____ such as tetanus toxin and the viruses that cause ____, ____ and ____

single axon

The ____ ____ of a neuron propagates nerve impulses toward another neuron, a muscle fiber, or a gland cell.

ribosomes

The ____ are the sites of protein synthesis.

effectors somatic; autonomic

The motor or efferent division of the PNS - conveys output from the CNS to ____ (muscles and glands) - further subdivided into a ____ nervous system and an ____ nervous system

insulates; nerve impulse conduction

The myelin sheath - electrically ____ the axon of a neuron - increases the speed of ____ ____ ____.

voluntary

The nervous system initiates all ____ movements

initial segment

The part of the axon closest to the axon hillock is the ____ ____

blood capillaries neurons the pia mater

The processes of astrocytes make contact with... (3)

sensory receptors somatic; special

The sensory or afferent division of the PNS - conveys input into the CNS from ____ ____ in the body - provides the CNS with sensory information about the ____ senses (tactile, thermal, pain, and proprioceptive sensations) and ____ senses (smell, taste, vision, hearing, and equilibrium).

100 million

The spinal cord contains about ____ ____ neurons.

synaptic end bulbs varicosities

The tips of some axon terminals swell into bulb-shaped structures called ____ ____ ____; others exhibit a string of swollen bumps called ____

Schwann cells (in the PNS) oligodendrocytes (in the CNS).

Two types of neuroglia produce myelin sheaths: (2)

nerve

a bundle of hundreds to thousands of axons plus associated connective tissue and blood vessels that lies outside the brain and spinal cord.

nerve fiber

a general term for any neuronal process (extension) that emerges from the cell body of a neuron

microtubules

assist in moving materials between the cell body and axon

neurology

deals with normal functioning and disorders of the nervous system.

histologist shape; appearance

some neurons are named for the ____ who first described them or for an aspect of their ____ or ____

Dendrites

the receiving or input portions of a neuron

brain

the part of the CNS that is located in the skull and contains about 85 billion neurons.

5; 135 axon; short

Neurons - the neurons cell bodies range in diameter from ____ micrometers up to ____ μm - The pattern of dendritic branching is varied and distinctive for neurons in different parts of the nervous system. - A few small neurons lack an ____, and many others have very ____ axons.

neurotransmitter

A ____ is a molecule released from a synaptic vesicle that excites or inhibits another neuron, muscle fiber, or gland cell.

stimulus

A ____ is any change in the environment that is strong enough to initiate an action potential

synaptic vesicles

Both synaptic end bulbs and varicosities contain many tiny membrane-enclosed sacs called ____ ____ that store a chemical called a neurotransmitter

direction

Functionally, neurons are classified according to the ____ in which the nerve impulse (action potential) is conveyed with respect to the CNS

astrocytes oligodendrocytes microglial ependymal cells

Neuroglia of the CNS can be classified on the basis of size, cytoplasmic processes, and intracellular organization into four types: (4)

Schwann cells satellite cells

Neuroglia of the PNS completely surround axons and cell bodies. The two types of glial cells in the PNS are ____ ____ and ____ ____

glue smaller; 5 to 25 action potentials; multiply and divide

Neuroglia or glia - make up about half the volume of the CNS. - Their name derives from the idea of early histologists that they were the "____" that held nervous tissue together. - ____ than neurons, and they are ____ to ____ times more numerous. - In contrast to neurons, glia do not generate or propagate ____ ____, and they can ____ and ____ in the mature nervous system

1. PNS 2. myelin sheath 4. 20 5. axon regeneration

Schwann Cells 1. These cells encircle PNS axons 2. they form the ____ ____ around axons. 3. each Schwann cell myelinates a single axon 4. A single Schwann cell can also enclose as many as ____ or more unmyelinated axons 5. Schwann cells participate in ____ ____, which is more easily accomplished in the PNS than in the CNS

skeletal muscles voluntary

The somatic nervous system - conveys output from the CNS to ____ ____ only - Because its motor responses can be consciously controlled, the action of this part of the PNS is ____.

12 31

____ pairs of cranial nerves emerge from the brain and ____ pairs of spinal nerves emerge from the spinal cord.

The excitable characteristic of nervous tissue

allows for the generation of nerve impulses (action potentials) that provide communication with and regulation of most body organs.

effectors contract; secrete

nervous system - motor function - Once sensory information is integrated, the nervous system may elicit an appropriate motor response by activating ____ (muscles and glands) through cranial and spinal nerves) - Stimulation of the effectors causes muscles to ____ and glands to ____

1. brain 2. spinal chord

The central nervous system (CNS) consists of... (2)

CNS

Most signals that stimulate muscles to contract and glands to secrete originate in the ____.

axon

An ____ is a long, thin, cylindrical projection that often joins to the cell body at a cone-shaped elevation called the axon hillock

rough endoplasmic reticulum

Because ____ ____ ____ is not present, protein synthesis does not occur in the axon.

dendrite; axon retina; inner ear; olfactory

Bipolar neurons - have one main ____ and one ____ - They are found in the ____ of the eye, the ____ ____, and the ____ area of the brain.

effectors; PNS multipolar

Motor neurons or efferent neurons - convey action potentials away from the CNS to ____ (muscles and glands) in the ____ through cranial or spinal nerves - Motor neurons are ____ in structure.

2. ventricles; central canal 3. cerebrospinal fluid 4. Blood cerebrospinal fluid barrier

Ependymal Cells 1. cuboidal to columnar cells arranged in a single layer that possess microvilli and cilia. 2. These cells line the ____ of the brain and ____ ____ of the spinal cord 3. Produce, possibly monitor, and assist in the circulation of ____ ____ 4. form the ____ ____ ____

retrograde

Fast axonal transport that occurs in a ____ (backward) direction moves membrane vesicles and other cellular materials from the axon terminals to the cell body to be degraded or recycled.

anterograde

Fast axonal transport that occurs in an ____ (forward) direction moves organelles and synaptic vesicles from the cell body to the axon terminals.

gliomas CNS; PNS

In cases of injury or disease, neuroglia multiply to fill in the spaces formerly occupied by neurons. - Brain tumors derived from glia, called ____ tend to be highly malignant and to grow rapidly. - Of the six types of neuroglia, four—astrocytes, oligodendrocytes, microglia, and ependymal cells—are found only in the ____. The remaining two types—Schwann cells and satellite cells—are present in the ____.

parasympathetic sympathetic

In general, the ____ nervous system takes care of "rest-and-digest" activities the ____ nervous system helps support exercise or emergency actions—the so-called "fight-or-flight" responses.

multiple dendrites single axon

Most neurons have two kinds of processes: (2)

1. processing networks 2. brain; spinal chord 4. miotic division

Neurons 1. Form the complex ____ ____ within the brain and spinal cord 2. connect all regions of the body to the ____ and ____ ____ 3, provide most of the unique functions of the nervous system, such as sensing, thinking, remembering, controlling muscle activity, and regulating glandular secretions. 4. As a result of their specialization, most neurons have lost the ability to undergo ____ ____.

sensory receptors cranial or spinal nerves unipolar

Sensory neurons or afferent neurons - either contain ____ ____ at their distal ends (dendrites) or are located just after sensory receptors that are separate cells. - Once an appropriate stimulus activates a sensory receptor, the sensory neuron forms an action potential in its axon and the action potential is conveyed into the CNS through ____ or ____ ____. - Most sensory neurons are ____ in structure.

short distance longest

Some neurons are tiny and propagate impulses over a ____ ____ (less than 1 mm) within the CNS. Others are the ____ cells in the body

processes

Structurally, neurons are classified according to the number of ____ extending from the cell body

1. sympathetic nervous system 2. parasympathetic nervous system.

The ANS is comprised of two main branches (2)

sensory thoughts; emotions; memories

The CNS - processes many different kinds of incoming ____ information - also the source of ____, ____, and ____.

smooth muscle; cardiac muscles; glands involuntary

The autonomic nervous system - conveys output from the CNS to ____ ____, ____ ____, and _____ - Because its motor responses are not normally under conscious control, the action of the ANS is ____.

terminals telodendria

The axon and its collaterals end by... - dividing into many fine processes called axon ____ or axon ____

axoplasm axolemma

The cytoplasm of an axon, called ____, is surrounded by a plasma membrane known as the ____

neurofibrils microtubules

The cytoskeleton includes... (2)

Nissl bodies mitochondria other organelles

The dendrite's cytoplasm contains: (3)

1. support neurons 2. BBB 3. growth, migration, interconnection 4. chemical environment 5. learning and memory

The functions of astrocytes include the following: 1. Contain microfilaments that give them considerable strength, which enables them to ____ ____. 2. Processes of astrocytes wrapped around blood capillaries isolate neurons of the CNS from various potentially harmful substances in blood. In effect, the endothelial cells create a ____ ____ ____, which restricts the movement of substances between the blood and interstitial fluid of the CNS. 3. In the embryo, astrocytes secrete chemicals that appear to regulate the ____, ____, and ____ among neurons in the brain. 4.Astrocytes help to maintain the appropriate ____ ____ for the generation of nerve impulses. 5. Astrocytes may also play a role in ____ and ____ by influencing the formation of neural synapses

smells speech remember body movements internal organs sensory; integrative; motor

The nervous system carries out a complex array of tasks - allows us to sense various ____ - produce ____ - ____ past events - provides signals that control ____ ____ - regulates the operation of ____ ____ These diverse activities can be grouped into three basic functions: ____ (input), ____ (process), and ____ (output).

perceptions behaviors memories

The nervous system is responsible for our (3)

nerve impulses releasing hormones

The nervous system regulates body activities by responding rapidly using ____ ____ the endocrine system responds by ____ ____

foramen magnum vertebral column

The spinal cord is connected to the brain through the ____ ____ of the occipital bone and is encircled by the bones of the ____ ____.

Protoplasmic Fibrous

There are two types of astrocytes - ____ astrocytes: have many short branching processes and are found in gray matter - ____ astrocytes: have many long unbranched processes and are located mainly in white matter

Astrocytes

These star-shaped cells have many processes and are the largest and most numerous of the neuroglia.

the central nervous system peripheral nervous system

This intricate network of billions of neurons and even more neuroglia is organized into two main subdivisions: (2)

fused pseudounipolar sensory receptors junction synaptic end bulbs ganglia; cranial nerves

Unipolar neurons - have dendrites and one axon that are ____ together to form a continuous process that emerges from the cell body - called ____ neurons because they begin in the embryo as bipolar neurons. During development, the dendrites and axon fuse together and become a single process. - The dendrites of most unipolar neurons function as ____ ____ that detect a sensory stimulus such as touch, pressure, pain, or thermal stimuli. - The trigger zone for nerve impulses in a unipolar neuron is at the ____ of the dendrites and axon - The impulses then propagate toward the ____ ____ ____. - The cell bodies of most unipolar neurons are located in the ____ of spinal and ____ ____.

effectors

____ receive innervation from both branches of the ANS - usually the two branches have opposing actions. (For example, neurons of the sympathetic nervous system increase heart rate, and neurons of the parasympathetic nervous system slow it down.)

neurologist

a physician who diagnoses and treats disorders of the nervous system.

ganglion

collection of neuron cell bodies outside the CNS

neurofibrils

composed of bundles of intermediate filaments that provide the cell shape and support

The peripheral nervous system (PNS)

consists of all nervous tissue outside the CNS

ANS GI tract smooth muscle; glands ANS

enteric nervous system - third branch of the ____ - an extensive network of over 100 million neurons confined to the wall of the ____ ____ - helps regulate the activity of the ____ ____ and ____ of the GI tract - Although the ENS can function independently, it communicates with and is regulated by the other branches of the ____.

integration

nervous system integrative function - The nervous system processes sensory information by analyzing it and making decisions for appropriate responses—an activity known as ____.

internal stimuli; external stimuli cranial; spinal

nervous system sensory function - Sensory receptors detect ____ ____, such as an increase in blood pressure, or ____ ____ (for example, a raindrop landing on your arm). - This sensory information is then carried into the brain and spinal cord through ____ and ____ nerves.

- neurons - neuroglia

nervous tissue comprises two types of cells— (2) - These cells combine in a variety of ways in different regions of the nervous system

perikaryon; soma nucleus; cytoplasm ribosomes; Nissl bodies

neuron cell body - also known as the ____ or ____ - contains a ____ surrounded by ____ that includes typical cellular organelles such as lysosomes, mitochondria, and a Golgi complex. - Neuronal cell bodies also contain free ____ and prominent clusters of rough endoplasmic reticulum, termed ____ ____

sensory receptor

refers to a structure of the nervous system that monitors changes in the external or internal environment. - Examples include touch receptors in the skin, photoreceptors in the eye, and olfactory (smell) receptors in the nose.

synapse

the site of communication between two neurons or between a neuron and an effector cell

cell body; axon terminals microtubules; cytoskeletom

two types of transport systems carry materials from the cell body to the axon terminals and back. 1. The slower system, which moves materials about 1-5 mm per day, is called slow axonal transport. It conveys axoplasm in one direction only—from the ____ ____ toward the ____ ____ - Slow axonal transport supplies new axoplasm to developing or regenerating axons and replenishes axoplasm in growing and mature axons. 2. Fast axonal transport, which is capable of moving materials a distance of 200-400 mm per day, uses proteins that function as "motors" to move materials along the surfaces of ____ of the neuron's ____. - Fast axonal transport moves materials in both directions—away from and toward the cell body.