Histology Final-Nervous System

Front 1

Anatomic Divisions of the Nervous System?

Back 1

Central and Peripheral

Front 2

Functional Divisions of the Nervous System?

Back 2

Somatic and Autonomic

Front 3

2 Principal Nerve cell types?

Back 3

neurons and glia

Front 4

glia function?

Back 4

provide physical and functional support

Front 5

Neuron properties?

Back 5

-neurons are specialized
1. irritability: initiation of an impulse in response to a stimulus

2. conductivity: neurons transmit impulse from one location to another

Front 6

Neuronal cell body location?

Back 6

most neuronal cell bodies are in or near the CNS

Front 7

synapses?

Back 7

-specialized cell-to-cell contacts

-impulse transmitted through synapse from one cell to the next

Front 8

Neuron basic cell structure?

Back 8

consists of a cell body, usually with various processes coming off of it.

Front 9

Neuronal Process types?

Back 9

-2 basic types

1. dendrites: specialized to receive info

2. axons: specialized to transmit info

Front 10

Neurons are?

Back 10

the structural and functional unit of the central nervous system.

Front 11

Nervous system function depends on?

Back 11

integration of information.

Front 12

Nervous system activity involves?

Back 12

the activity of many neurons with many potential interconnections via synapses

Front 13

Simplest Pattern of Neuron interconnection is?

Back 13

Reflex Arc

Front 14

Describe the 2 Neuron Reflex Arc.

Back 14

- i.e. knee jerk
-afferent (incoming)
-efferent (outgoing)

Front 15

Afferent portion of 2 neuron relfex arc?

Back 15

-incoming
-sensory neuron with dendrites in the patellar tendon, cell body in the dorsal root ganglion, axon terminating in the spinal cord

Front 16

Efferent portion of 2 neuron relfex arc?

Back 16

-outgoing
-motor neuron has dendrites and cell body in the spinal cord with axon terminating in the thigh muscle

Front 17

Describe the 3 neuron reflex arc.

Back 17

-pain withdrawl
-has an interneuron between sensory and motor neurons in spinal cord
-provides connections within the CNS

Front 18

Do reflex arcs technically exist?

Back 18

Reflex arcs as described do not exist; any input into the CNS results in widespread activity.

Front 19

Basic CNS model?

Back 19

-Inflow of activity to CNS
-Modification and Integration of info
-Outflow of activity to effector cell

Front 20

Neuron Size

Back 20

-neurons vary greatly in size
-cell body 4-150 um in size

Front 21

Describe axon processes.

Back 21

almost always is a single process

Front 22

Describe dendrite processes.

Back 22

are usually multiple

Front 23

Overall neuron structure can be?

Back 23

unipolar, bipolar, or multipolar

Front 24

Describe unipolar neuron structure.

Back 24

single bifurcating process

Front 25

Describe bipolar neuron structure.

Back 25

2 processes; axon and dendrite

Front 26

Describe multipolar neuron structure.

Back 26

numerous processes and shapes (most abundant)

Front 27

Most abundant neuronal structure is?

Back 27

multipolar

Front 28

Describe the neuronal cell body.

Back 28

-"perikaryon"
-contains:
1.nucleus; usually with a single prominent nucleolus
2. cytoplasmic organelles include nissl bodies (free ribosomes and RER)

Front 29

Describe cytoskeletal fibers in the nervous system.

Back 29

-present both within the cell body as well as in axonal and dendritic processes
-types include neurofilaments (intermediate filaments) and microtubules.

Front 30

axon hillock?

Back 30

a conical region where the axon originates from the cell body

Front 31

What inclusions are present within neuronal cytoplasm?

Back 31

-fat droplets (common)
-glycogen (embryonic)
-various pigment granules

Front 32

Describe dendrite number in unipolar and bipolar cells.

Back 32

-have only 1 dendrite.
-atypical in structure
-resembles an axon

Front 33

Describe dendrite number in multipolar cells.

Back 33

-dendrites leave the cell body like branches of a tree
-dendrites are thicker where they leave the nerve cell body and become more slender and branching

Front 34

Dendrite branching in multipolar cells enables what?

Back 34

branching enables dendrites to receive and integrate a large number of axon terminals.

Front 35

Describe the neuropil?

Back 35

-made mostly of dendrites.
-are fibrous processes of dendrites, axons, and astrocytes in the CNS.

Front 36

Axon characteristics?

Back 36

-most neurons have only 1, few have no axon.
-a cylindrical process
-constant diameter for any one neuron, but varies in diameter from one neuron to the next.

Front 37

Types of neurons by length of axonal process?

Back 37

Golgi Type I and Golgi Type II

Front 38

Describe Golgi Type I Neurons

Back 38

-very long axons
-cell body in grey matter of CNS
-axons contribute to peripheral nerves
-form main fiber tracts in CNS

Front 39

Describe Golgi Type II Neurons

Back 39

-stellate neurons
-short axons
-numerous in cerebral and cerebellar cortices and in the retina
-vary in size and shape

Front 40

Types of neurons by the number of processes from the cell body?

Back 40

Unipolar, Pseudounipolar, Bipolar, Multipolar, and Perkinje Cells

Front 41

Unipolar Neuron Characteristics.

Back 41

-true unipolar cells have only one axon
-few in adult, mostly embryonic

Front 42

Pseudounipolar Neuron Characteristics.

Back 42

-originally are bipolar
-during development, the axon and dendrite fuse, leaving the cell body and the same site and the run together before separating
-found in spinal and cranial ganglia

Front 43

Pseudounipolar Neuron Location

Back 43

-found in spinal and cranial ganglia

Front 44

Bipolar Neuron Characteristics.

Back 44

-have axon and dendrite at opposite poles
-found in olfactory epithelium, retina, and sensory ganglia.

Front 45

Bipolar Neuron Location

Back 45

-found in olfactory epithelium, retina, and sensory ganglia.

Front 46

Multipolar Neuron Characteristics.

Back 46

-most common type
-vary in shape depending on the arrangement of many dendrites
-branching is extensive but planar

Front 47

Nuclei vs. Ganglia?

Back 47

-are both clusters of neuronal cell bodies
-inside the CNS=nuclei
-outside the CNS=ganglia

Front 48

Describe Nerve Fibers.

Back 48

-axon
-is enclosed in a sheath
-two types, unmyelinated and myelinated.

Front 49

Two types of Nerve Fibers?

Back 49

Myelinated and Unmyelinated.

Front 50

Describe Unmyelinated Nerve Fibers.

Back 50

-CNS, unmyelinated sheath=partial covering

-PNS, unmyelinated sheath=neurolemma=Schwann Cell Plasma Membrane=no myelin

Front 51

Myelin?

Back 51

-white matter formed by a series of lamellae
-found in the lamellae of Schwann Cell/Oligodendrocyte Plasma Membrane

Front 52

Schwann Cell/Oligodendrocyte Plasma Membrane Composition?

Back 52

-mostly lipid, also protein component
-modified plasma membrane

Front 53

Node Characteristics.

Back 53

-myelin sheath is an incomplete cylinder around the axon, is interrupted at regular intervals.
-these Gaps are Nodes of Ranvier
-gaps are where axonal membrane is exposed to extracellular space
-a single Schwann cell covers the area between nodes

Front 54

Covers the area between nodes?

Back 54

-a single Schwann Cell

Front 55

Wrap myelinated fibers in the CNS?

Back 55

Oligodendrocytes.

Front 56

Schwann Cell Characteristics

Back 56

-envelop all axons of peripheral nerves
-cover the axon from point of attachment to spinal cord almost to their termination
-are necessary for regeneration following injury
-form channels for regrowth

Front 57

Peripheral Nerve Characteristics

Back 57

-composed of many nerve fibers held together by CT
-CT is layered as the epineurium, perineurium, and endoneurium.
-blood to peripheral nerves is rich and runs through CT

Front 58

Synapse Characteristics

Back 58

-site of junction of neurons
-axon terminals: endbulbs, endfeet, or bouton terminaux
-axons terminate on nerve cell body, dendrites, or axons of another neuron.
-axon terminals contain numerous mitochondria and synaptic vesicles.

Front 59

Axons terminate where?

Back 59

on nerve cell body, dendrites, or axons of another neuron.

Front 60

Axon terminals contain?

Back 60

numerous mitochondria and synaptic vesicles.

Front 61

Types of Neuroglia?

Back 61

Astrocytes, Oligodendrocytes, Schwann Cells, Ependymal Cells, Microglia

Front 62

Neuroglia Characteristics.

Back 62

-all are supporting cells
-some form myelin
-some are phagocytic
-generally provide supportive framework for neurons

Front 63

Astrocyte Characteristics.

Back 63

-star-shaped
-numerous branching processes
-Two types: Protoplasmic Astrocytes and Fibrous Astrocytes

Front 64

Describe Protoplasmic Astrocytes.

Back 64

-mossy cells
-have many branching processes
-found in grey matter

Front 65

Describe Fibrous Astrocytes.

Back 65

-spider cells
-have longer, more slender processes
-found mostly in white matter
-control the ionic and chemical environment of neurons
-have processes that line the surface of the CNS, separating it from other tissues.

Front 66

Two types of astrocytes?

Back 66

Fibrous and Proteoplasmic.

Front 67

Oligodendrocyte Characteristics.

Back 67

-found in the CNS
-produce a myelin sheath
-one oligodendrocyte can wrap around the axons of several neurons

Front 68

Schwann Cell Characteristics

Back 68

-are in the PNS
-produce a myelin sheath or simply enclose a nerve fiber
-one Schwann cell myelinates one nerve fiber

Front 69

Microglia Characteristics.

Back 69

-the body of the cell is fibroblast-like with many processes
-distributed throughout grey and white matter
-phagocytic cells involved in inflammation and repair processes
-when activated, they retract thier processes and resemble macrophages

Front 70

Microglia behavior when activated?

Back 70

when activated, they retract thier processes and resemble macrophages

Front 71

Ependymal Cell Characteristics.

Back 71

-are epithelial cells
-the CNS develops as a hollow tube (ectoderm becomes neuroectoderm, the forms tube)
-tube persists in ventricles of the brain and central canal of the spinal cord.
-epedymal cell line these cavities
-retain their epithelial characteristics present in the embryo.

Front 72

Blood Brain Barrier Characteristics

Back 72

-principle component is occluding junctions between endothelial cells of capillaries that serve as neural tissue
-end feet of glial cells wrap the capillaries; these also contribute to low permeability
-astrocyte cell processes coveer almost 99% of brain capillary surface area

Front 73

Principle component of the Blood Brain Barrier?

Back 73

principle component is occluding junctions between endothelial cells of capillaries that serve as neural tissue

Front 74

Contribute to low permeability of Blood Brain Barrier?

Back 74

end feet of glial cells wrap the capillaries; these also contribute to low permeability

Front 75

Neural Tissue in the CNS is protected by?

Back 75

Bone

Front 76

Membranes of the CNS?

Back 76

-are within a bony case=meninges
- dura mater is outermost
-Subdural Space
-arachnoid membrane is in the middle
-subarachnoid space
-Pia Mater is innermost membrane

Front 77

Dura Mater Characteristics.

Back 77

-fibrous, tough, continuous with the periosteum of the underside of the skull
-actually in two layers, endosteal layer and fibrous layer
-inner surface has a lining of simple squamos mesothelium derived from the mesenchyme
-portion that surrounds the spinal cord is spearated from the periosteum of the vertebrae by the epidural space

Front 78

Describe the Endosteal Layer of the Dura Mater.

Back 78

-dense CT containing many blood vessels and nerves
-in contact with the inner surface of the bone
-is the periosteum of the skull

Front 79

Describe the Fibrous Layer of the Dura Mater.

Back 79

-dense fibrous tissue
-inner portion of the dura mater
-has a lining of simple squamos mesothelium derived from the mesenchyme

Front 80

Describe the epidural space.

Back 80

-separates the periosteum of the vertebrae in the spinal cord from the dura mater
-contains: venous channels, loose CT, adipose tissue

Front 81

Describe the Arachnoid Membrane

Back 81

-lines the dura mater
-covers brain surface without penetrating into folds
-delicate, unvascularized CT composed of fine collagenous and some elastic fibers.
-surface is lined with simple squamos epithelium that can become phagocytic

Front 82

Describe the subarachnoid space.

Back 82

-separates the pia mater and the arachnoid membrane
-penetrated by many trabeculae that connect the arachnoid with the pia mater
-contains numerous blood vessels

Front 83

Describe the Pia Mater.

Back 83

-a delicate membrane closely associated with the surface of the brain
-extends into the folds in the brain surface
-highly vascularized
-can be described in two layers, the intima pia and the epipial layer.

Front 84

Describe the intima pia.

Back 84

-innermost layer of the pia mater
-fine reticular and elastic fibers
-closely follows the surface of the brain, adhering to it
-penetrates into the brain as a covering of larger blood vessels

Front 85

Describe the epipial layer

Back 85

-outermost layer of the pia mater
-composed of a network of collagenous fibers
-continuous with tissues of the arachnoid

Front 86

Describe the Choriod Plexus

Back 86

-produces CSF and is highly vascularized
-consists of infoldings of the pia mater
-covered by a simple cuboidal epithelium derived from ependymal cells
-extensive in the lateral ventricle and lines the roof of the 3rd and 4th ventricles

Front 87

The 4th ventricle of the brain communicates with?

Back 87

the subarachnoid space

Front 88

All ventricles of the brain are continuous with?

Back 88

`the central canal of the spinal cord.

Front 89

Describe CSF.

Back 89

-produced by the choriod plexus
-clear, colorless fluid which is mostly water with small amounts of proteins, ions, and organic substances

Front 90

Where is CSF found?

Back 90

-CSF is found in the CNS in ventricles of the brain and the central canal of the spinal cord as well as in the pia arachnoid membranes including the subarachnoid space.

Front 91

CSF Function?

Back 91

functions to act as a shock absorber and is important metabolically to the neural tissue.

Front 92

Describe Neuronal Organization.

Back 92

most neurons aggregate to form populations, usually of similar neurons.

Front 93

3 Common Neuron Aggregate Types?

Back 93

1. Ganglia of the PNS
2. Cellular Groups in the CNS (nuclei)
3. Cortical Formations of the CNS

Front 94

Describe Ganglia of the PNS

Back 94

are sensory ganglia associated with cranial and spinal nerves as well as ganglia of the autonomic nervous system

Front 95

2 Primary Neuronal Cell Types found in nuclear center?

Back 95

1. Principal Cells
2. Interneurons

Front 96

Describe Principal Cells.

Back 96

-emit efferent axons that connect the cell mass with other parts of the CNS
-have longer axons and are usually the largest cells in the mass (Golgi Type I)

Front 97

Describe Interneurons

Back 97

-smaller than the principal cell
-Golgi Type II

Front 98

Numerous, Long, and Wider processes usually correlate with?

Back 98

Larger neuronal cell bodies.

Front 99

Cerebellum Function?

Back 99

function is related to coordination of movement of striated (skeletal) muscle

Front 100

Cerebellum General Anatomy?

Back 100

-right and left hemispheres and a central region divided into lobules.
-has grey matter at the surface and white matter located centrally.

Front 101

3 Layers of the Cerebellum?

Back 101

1. Outer Molecular Layer: mostly fibers with a few small nerve cells
2. Central Layer:single row of purkinje cell bodies
3. Inner Granular Layer: many small neuronal cell bodies

Front 102

Describe the Molecular Layer of the Cerebellum.

Back 102

-consists of a few nerve cells and many non-myelinated fibers
-fibers are mostly purkinje cell dendrites
-nerve cells are stellate

Front 103

Describe the Central Layer of the Cerebellum.

Back 103

-Purkinje cell bodies with dendrites that project into the molecular layer
-Purkinje cell axons project through the granular layer to terminate in deep nuclei of the cerebellum or in other parts of the cortex

Front 104

Describe the Inner Granular Layer of the Cerebellum.

Back 104

-neurons of the granular layer are small with few dendrites and a non myelinated axon that runs into the molecular layer

Front 105

Describe the Cerebrum.

Back 105

-cerebral gray matter is located at the surface as cerebral cortex and deeper as ganglia or nuclei
-ridges=gyri
-folds=depressions=sulci
-the cerebral cortex is organized into 6 layers.

Front 106

Describe the outermost layer of the cerebral cortex.

Back 106

composed mostly of fibers from cells of deeper layers

Front 107

Describe the inner 5 layers of the cerebral cortex.

Back 107

-beneath the molecular layer
-each has a predominant (1 or 2) neuronal cell type (by shape) with different types in each layer
-the different layers blend with each other and all contain neuroglia and a neuropil

Front 108

Describe Neuropil of the Cerebral Cortex.

Back 108

neuronal cells in unmyelinated nerve cell fibers and processes of neuroglia.

Front 109

Describe the thickness of the different layers of the cerebral cortex.

Back 109

thickness varies in different regions of the cerebral cortex and is related to the particular function of the different regions.

Front 110

Describe the white matter of the cerebral cortex.

Back 110

underlies cerebral cortex and consists of bundles of myelinated fibers passing in all directions.

Front 111

3 Primary Myelinated Fiber Types in the Cerebral Cortex:

Back 111

1. Association Fibers
2. Commissural Fibers
3. Projection Fibers

Front 112

Describe Association Fibers.

Back 112

connect different areas of one hemisphere in the cerebral cortex

Front 113

Describe Commissural FIbers.

Back 113

connect areas of the cerebral cortex in one hemisphere with areas of the cerebral cortex in another hemisphere

Front 114

Describe Projection Fibers.

Back 114

connect areas of the cortex with lower centers of the CNS.