Nerve Tissue

Question 1

Nerve Tissue - Composition

Answer 1

Nerve tissue is composed of cells (neurons) that are specialized for conveying information, as well as support cells (called glial cells)

Question 2

Neurons: Neuron doctrine

Answer 2

Neuron doctrine: released in 1891; stated that individual neurons are the signaling elements of the nervous system

Question 3

Neurons: How many are there in the human body?

Answer 3

There are over 100 billion neurons in the human body of varying size and shape

Question 4

Neurons: Function

What is the function of Neurons?

Answer 4

Neurons receive, process, and transmit signals using electrical and chemical mechanisms

Question 5

Neurons: Function

What do electrical signals typically convey?

Answer 5

Electrical signals typically convey information rapidly from one part of a neuron to another

Question 6

Neurons: Function

What do chemical signals typically convey?

Answer 6

Chemical signals typically carry information between one part of a neuron and a part of a second neuron or effector cell (muscle cells, glandular cells, and cardiac cells)

Question 7

Regions of the neuron

Why are neurons structured into regions?

Answer 7

So that organelles can be distributed in a pattern that supports neuronal function

Question 8

Neuron Regions: Cell body

Answer 8

AKA Perikaryon

Contains the nucleus and surrounding cytoplasm

Does NOT include the cell processes

Question 9

Neuron Regions: Cell Body - Structure

Nucleus

Answer 9

Large and spherical in shape

Euchromatic (this means that this part of the cell body is pale staining, which indicates that it is active in RNA synthesis) with a prominent nucleolus

Question 10

Neuron Regions: Cell Body - Structure

Cytoplasm

Answer 10

Abundant rough endoplasmic reticulum (RER and NIssl Substance) and polysomes

Well developed golgi apparatus (post office of the cell)

Numerous mitochondria

Has a well developed cytoskeleton (most distinguishing feature)

Question 11

Neuron Regions: Cell Body - Function

Answer 11

Trophic (of or retaliating to nutrition) center of the cell

Receptive to stimuli

Question 12

Neuron Regions: Dendrites

Answer 12

Elongated processes emanating from the cell body

Most neurons have numerous dendrites

Question 13

Neuron Regions: Dendrites

Structure

Answer 13

Short, tapered, and highly branched

Cytoplasm has organelles similar to the cell body except there are no golgi complexes

Dendritic spines are specializations that are located at some synapses

Question 14

Neuron Regions: Dendrites

Function

Answer 14

Receptive to Stimuli

Transmit signals towards the cell body

Question 15

Neuron Regions: Axons

Answer 15

Elongated processes emanating from the cell body

Most Neurons have only one axon

Question 16

Neuron Regions: Axons

Structure

Answer 16

Long, cylindrical (no tapering), and not highly branched

Cytoplasm has organelles similar to the cell body excet there is no RER or polysomes

Question 17

Neuron Regions: Axons

Structure - Axon Hillock

Answer 17

Pyramid shaped region where the axon emanates from the cell body

Devoid of Nissl Substance (appears lighter in a stain)

Question 18

Neuron Regions: Axons

Structure - Terminal Arborization

Answer 18

Branched distal portion of the axon

Question 19

Neuron Regions: Axons

Function

Answer 19

Generate and conduct signals

Receptive to stimuli

Question 20

Neuron Regions: Presynaptic Terminal

Answer 20

aka Terminal Bouton or Terminal Bud

Dilated termination of the axon on another cell at the chemical synapse

This region has NO myelin sheath

Question 21

Neuron Regions: Presynaptic Terminal

Structure - Cytoplasm

Answer 21

Organelles are similar to the cell body except there are more mitochondria and there are small, spherical, membrane bounded synaptic vesicles containing neurotransmitters

Question 22

Neuron Regions: Presynaptic Terminal

Structure - Active Zones

Answer 22

Regions along the presynaptic membrane concentrated with voltage-gated calcium channels and synaptic vessicles

Question 23

Neuron Regions: Presynaptic Terminal

Function

Answer 23

Signal transmission to another cell

Question 24

Neuron Molecular Transport systems

Composition and Function

Answer 24

They are composed of the well developed cytoskeleton of the neuron and are responsible for the transport of substances between the cell body and the axon and its terminals.

They can transport substances at slow (.2 - 4 mm/day), intermediate, and fast (20 - 400 mm/day) speeds

Question 25

Neuron Molecular Transport systems Anterograde

Answer 25

Carries material (i.e. organelles, macromolecules) from the cell body to the periphery

Question 26

Neuron Molecular Transport systems Retrograde

Answer 26

Carries material (i.e. toxins, viruses) from the periphery to the cell body. That's how AIDS travles

Question 27

Neuron Categories: Motor (Efferent) Neurons Function

Answer 27

Control effector organs (i.e. muscles, glands)

Question 28

Neuron Categories (Based on Functional Roles): Motor (Efferent) Neurons General Somatic Efferent (GSE)

Answer 28

Motor Innervation to skeletal muscles deirved from myotomes

Question 29

Neuron Categories (Based on Functional Roles): Motor (Efferent) Neurons General Visceral Efferent (GVE)

Answer 29

Motor innervation to smooth muscle, cardiac muscle, and glands

Question 30

Neuron Categories (Based on Functional Roles): Motor (Efferent) Neurons Special Visceral Efferent (SVE)

Answer 30

Motor innervation to skeletal muscles derived from pharyngeal arches

Question 31

Neuron Categories (Based on Functional Roles): Sensory (Afferent) Neurons Function

Answer 31

Receive sensory stimuli through specialized nerve endings called receptors

Question 32

Neuron Categories (Based on Functional Roles): Sensory (Afferent) Neurons General Somatic Afferent (GSA)

Answer 32

Sensory input from structures associated with the body wall and extremities

Question 33

Neuron Categories (Based on Functional Roles): Sensory (Afferent) Neurons General Visceral Afferent (GVA)

Answer 33

Sensory input from the viscera, including smooth muscle, cardiac muscle, and glands

Question 34

Neuron Categories (Based on Functional Roles): Sensory (Afferent) Neurons Special Somatic Afferent (SSA)

Answer 34

Sensory input from structures associated with the senses of vision, hearing, and balance

Question 35

Neuron Categories (Based on Functional Roles): Sensory (Afferent) Neurons Special Visceral Afferent (SVA)

Answer 35

Sensory input from structures associated with the senses of smell and taste

Question 36

Neuron Categories (Based on Functional Roles): Interneurons

Answer 36

Connect other neurons Most numerous

Question 37

Neuron Categories (Based on Functional Roles): Interneurons Local

Answer 37

All processes confined in a small area

Question 38

Neuron Categories (Based on Functional Roles): Interneurons Projection

Answer 38

Long axons connecting different areas

Question 39

Neuron Categories (Based on Size and Shape of neuronal Processes): Multipolar

Answer 39

The cell body has multiple dendrites and only one axon These are the most common. Motor and interneurons are multipolar Example: Alphamotor Neurons

Question 40

Neuron Categories (Based on Size and Shape of neuronal Processes): Bipolar

Answer 40

There is one dendrite and one axon These neurons are sensory This is the developmental stage of most neurons Example: Special sense organs (ie retina, olfactory epithelium, vestibular system, etc.)

Question 41

Neuron Categories (Based on Size and Shape of neuronal Processes): Pseudounipolar

Answer 41

These neurons have a single process that is close to the cell body and divides into 2 branches: a central and a peripheral axon. These cells don't have dendrites. These neurons are sensory Example: dorsal root ganglia - The peripheral axon goes from the input to the cell body and the central axon goes form the cell body to the spinal cord

Question 42

Glial Cells: Overview How many are there as compared to neurons? What do they look like?

Answer 42

10 times more abundant in the mamillian brain than neurons; they vary greatly in size and shape

Question 43

Glial Cells: Function

Answer 43

They surround and support the neurons. They do not participate directly in synaptic interactions and electrical signaling.

Question 44

Glial Cells: Macroglia Astrocytes (Types, function, location)

Answer 44

Astrocytes are the most common form of macroglia Types: Protoplasmic, Fibrous Function: Structural support, iconic homeostasis, neurotransmitter uptake, repair process, blood brain barrier, secrete growth factors Location: CNS

Question 45

Glial Cells: Macroglia Radial glial astrocytes

Answer 45

Function: Guide migrating neurons and direct outgrowth of axons (help guide axons to their target cells) Location: Developing CNS

Question 46

Glial Cells: Macroglia Oligodendrocytes (Function, Location)

Answer 46

Function: Myelin production - they are capable of myelinating several internodes on several axon in the CNS; oligodendrocytes that do not produce myelin are called SATELLITE CELLS and are associated with neuronal cell bodies. Location: CNS

Question 47

Glial Cells: Macroglia Schwann Cels (Function, Location)

Answer 47

``` Function: Myelin production - they are capable of myelinateding only one internode on one axon in the PNS Ensheath axons (with or without myelin) Schwann cells that do not ensheath axons are called SATELLITE CELLS and are associated with neuronal cell bodies. ``` Location: PNS

Question 48

Glial Cells: Microglia

Answer 48

Function: Macrophagic activity Location: CNS

Question 49

Glial Cells: Ependymal cells

Answer 49

Function: Line cavities (cavities are called ventricles) Location: CNS **these are sometimes considered epithelial cells

Question 50

Myelin Sheath: Structure

Answer 50

Segmented, multilamellar, lipid rich, wrapping of axons

Question 51

Myelin Sheath: Structure What types of cells form the myelin sheath?

Answer 51

Formed by the plasma membranes of oligodendrocytes in the CNS and Schwann cells in the PNS

Question 52

Myelin Sheath: Structure Internode

Answer 52

A single segment of myelin sheath on an axon

Question 53

Myelin Sheath: Structure Node of Ranvier

Answer 53

An interval at which the axon is not covered by a myelin sheath; located between internodes.

Question 54

Myelin Sheath: Function

Answer 54

Provides electrical insulation. Increases the speed of impulse conduction by saltatation, a method whereby the action potential jumps (or saltates) from node to node