Histology: Nervous System

Front 1

nodes of ranvier

Back 1

speeds up transmission, hopping from spot to spot

Front 2

What is the basic structural and functional unit of the nervous system?

Back 2

Neurons- electrically excitable cells that can be highly polarized and are able to communicate signals long distances with action potentials.

Front 3

Describe the structure of a neuron.

Back 3

A neuron has a main cell body with processes calls axons and dendrites.

Front 4

What are synapses?

Back 4

Cell junctions specialized for transmitting signals from other neurons.

Front 5

What is the 2nd major component of nervous tissue?

Back 5

Glial cells. These are cells that separate neurons from one another. Glial cells surround neurons and provide metabolic and physiological support for neuronal functions.

Front 6

Is nervous tissue cellular or mostly acellular?

Back 6

Very cellular with neurons and glia comprising most of tissue. Very little intercellular space or ECM

Front 7

What is the relationshp b/w nervous tissue and the nervous system.

Back 7

Nervous tissue is the "parenchyma" (supporting tissue) of the entire nervous system, which is a main organ system of the body.

Front 8

In addition to glial cells and neurons, what else makes up the nervous system?

Back 8

The nervous system also contains stroma components, like CT cells and matrix, epithelial and muscle cells. These non neuronal cells are mainly found in blood vessels, blood and lymph, meninges and CT sheaths.

Front 9

Describe the 2 parts of the nervous system.

Back 9

Central nervous system is the brain and spinal cord. The peripheral nervous system is comprised of axons that extend out from CNS, ganglia and other various neuronal processes.

Front 10

What are ganglia?

Back 10

Clusters of nerve cell bodies found in the PNS.

Front 11

Name 3 types of neuronal cell bodies.

Back 11

bipolar, pseudo-unipolar and multipolar.

Front 12

Desrcibe a pseudounipolar cell body.

Back 12

A globular neuronal body with a single bifurcated process, e.g., sensory neurons in the dorsal root ganglia.

Front 13

Describe a bipolar cell body.

Back 13

A cell body with spindle shaped processes at each end, e.g., neurons of acoustic ganglia, olfactory neurons and some retinal neurons.

Front 14

Describe a multipolar cell body.

Back 14

A cell body with multiple processes. Most common nerve cell type.

Front 15

What is a nissl body and where is it found?

Back 15

granular ER, found in cytoplasm of neuron.

Front 16

What are lipofuscin granules?

Back 16

Pigment granules that accumulate in neurons with age.

Front 17

Where are microtubules and neurofilaments found in neurons?

Back 17

In the axons and dendrites.

Front 18

What is the role of the dendrite?

Back 18

Dendrites are processes that get stimuli and then transmit signals toward the cell body. THey have a stem that branches in a brush like manner not far from cell body.

Front 19

What is a dendritic spine?

Back 19

Spines on some dendrites which are the sites of synaptic contact.

Front 20

What is the role of an axon?

Back 20

Axon is a single cell process that conducts impulses away from the cell body. It is longer and thinner than a dendrite. THese are smooth and don't usually branch near the cell body.

Front 21

Where does one find the axon hillock?

Back 21

This is the conical projection in the cell body from which the axon extends.

Front 22

What are collateral branches?

Back 22

Axon branching at their ends (also called terminal arborizations).

Front 23

What is the role of myelin and where is it found?

Back 23

Myelin wraps some axons forming a sheath and increases conductivity of signals. Myelin is made by glial cells.

Front 24

WHere are synapses?

Back 24

These communication sites are found between end of an axon and a cell body or dendrite if another neuron.

Front 25

What is the terminal buoton?

Back 25

The bulbous expansion at the axon terminal that contains synaptic vesicles.

Front 26

Describe a synaptic region.

Back 26

On one cell- a terminal buton with synaptic vesicles. On the other cell, a post-synaptic membrane. Cells are separated by a synaptic cleft into which neurotransmitter is released.

Front 27

Describe neurotransmitter release.

Back 27

Following depolarization of a membrane of the axon terminal, a synaptic vesicle containing neurotransmitter is released into the synaptic cleft for uptake by the postsynaptic membrane.

Front 28

What is a neurotransmitter?

Back 28

A chemical signal.

Front 29

What is neuroglia and name 4 main types.

Back 29

Nerve glue originating from ectoderm that serves as support cells of the nervous system. They have lots of branching and require special stain to visualize structure. Astrocytes, Oligodendroglia, Microglia and Schwann cells.

Front 30

Describe Astrocytes.

Back 30

Star shaped glia with branching parts. Protoplasmic astros are in gray matter of CNS, while fibrous astros are thinner and found in white matter. Astros transport material b/w neurons, blood vessesl, give rigidity to CNS, Regulate amounts of EC space around neurons, store energy as glycogen, secrete growth factors, act as phagocytes and prevent neurons for contacting ea other.

Front 31

What are most brain tumors?

Back 31

Astrocyte gliomas.

Front 32

Describe oligodendrocytes?

Back 32

Common glial cells. More abundant in white matter where they make myelin sheaths of axons. In gray matter, they surround cell bodies.

Front 33

Describe microglia.

Back 33

Small, dense, elongated cells with processes covered with thorny projections. THey are muigratory and phagocytic.

Front 34

What are Schwann cells?

Back 34

Glial cells of PNS. They develop in embryo from neural crest cells. SOme make myelin sheaths around axons in PN, some are phagocytic and some act as sattellite cells in PNS ganglia. Some function in nerve regeneration.

Front 35

What is gray matter?

Back 35

In CNS, Gray matter is mostly nerve cell bodies, glial cells and unmyelinated processes. Gray matter makes cortex of brain and central horns of spinal cord.

Front 36

What is white matter?

Back 36

White matter is rich in myelinated nerve fibers and is located mostly in central area of brainand around periphery of spinal cord.

Front 37

If a slide is stained for myelin, what happens to the appearance of the gray and white matter?

Back 37

Gray matter looks light and white matter looks dark, e.g., colorations are reversed.

Front 38

What are nuclei in nervous tissue?

Back 38

Aggregates of neuronal cell bodies forming islands of gray matter embedded in white matter.

Front 39

What are laminae?

Back 39

Distinct layers or sheets of nerve bodies found in the cortex or cerebellum.

Front 40

What are sattelite cells?

Back 40

Abundant small glial cells that surround the cell body of each ganglion nerve cell. They originate from the neural crest.

Front 41

What are ganglia?

Back 41

Neuronal cell body groups outside of CNS.

Front 42

What is the capsule?

Back 42

Connective tissue that surrounds the ganglia outside the CNS.

Front 43

DEscribe the dorsal root ganglia.

Back 43

THese contain the cell bodies of pseudounipolar sensory neurons that carry impules away from the PNS to the CNS.

Front 44

Describe the autonomic ganglia.

Back 44

Found as enlargements of sympathetic trunks or collecton of nerve cell bodies in visceral organs. Have neurons with unmyelinated postganglionic axons.

Front 45

What are ependymal cells?

Back 45

Cells derived from neural tube that develop into an epithelium lining of brain ventricles (cavities) and central canal of spinal cord.

Front 46

Where is cerebrospinal fluid found?

Back 46

Cerebrospinal fluid is found in the brain ventricles (cavities).

Front 47

What are meninges?

Back 47

Fibrous connective tissue-like coverings of CNS.

Front 48

What are 3 layers of meninges?

Back 48

Dura mater (tough mother), arachnoid layer (spider-web like) and pia mater (tender mother).

Front 49

What is a choroid plexus?

Back 49

Folds of ependyma (choroidal villi) extending into ventricles of brain. Plexus has blood vessels and is coverd by cuboidal epithelium that secretes CSF.

Front 50

What is a blood-CSF barrier?

Back 50

IN the choroid plexus, the zonula occludens b/w epis creates a barrier.

Front 51

Describe the blood brain barrier.

Back 51

Capillaries in the brain have limited permeability that limits exchange of large molecules from the blood to CNS. Barrier is due to zonula occludens b/w cap. endothelial cells and also due to glial cells. This barrier prevents metabolites in blood from entering brain freely.

Front 52

What is function of brain capillary endothelial cells?

Back 52

Along with choroid plexus, their function is to allow transport of essential metabolites in blood across BBB.

Front 53

Describe Peripheral nerves.

Back 53

These nerves are composed of fibers which mostly pass through dorsal or ventral roots of the spinal cord. Fibers are surrounded by folds of Schwann cells.

Front 54

When is a PNS neuron said to be myelinated?

Back 54

When the Shwann cell folds are tightly wrapped and include myelin. If Schwann cell only hugs fiber, the axon is not myelinated.

Front 55

WHat is a nerve fiber?

Back 55

An axon or dendrite with its surrounding Schwann cell, regardless of whether or not myelin is present.

Front 56

What are nodes of ranvier?

Back 56

Interjucntions of adjacent Schwann cells that creates an interruption of the myelin sheath. These allow for nerve signals to move more quickly.

Front 57

What is the internode?

Back 57

The length of 1 Schwann cell between 2 nodes of ranvier.

Front 58

What is the significance of the Schmidt-Lanterman cleft.

Back 58

These occasional gaps in myeline membrane wrapping have no known purpose.

Front 59

What are fascicles?

Back 59

Archaec word for bundles of peripheral nerve fibers

Front 60

What is endoneurium?

Back 60

Enclosure surrounding individual Schwann cells and their enclosed axons.

Front 61

What is perineurium?

Back 61

Surrounds fasicles of nerve fibers in a nerve.

Front 62

What is epineurium?

Back 62

Ensheaths groups of fiber bundles.

Front 63

Describe Meissner's corpuscle.

Back 63

Mulitlaminar stacks of Schwann cells surrounding the terminus of an axon that are found in the papillary layer of the dermis.

Front 64

Describe Pacinian corpuscle.

Back 64

Unmyelinated nerve endings surrounded by concentric layers of fibroblasts found in the deeper layers of the dermis. Looks like a sliced onion in tranverse section.

Front 65

What are muscle spindles?

Back 65

A complex of skeletal muscle fibers and nerve endings encapsulated in CT that monitor muscle activity.

Front 66

Describe olfactory cells.

Back 66

Bipolar neurons with processes intruding through olfactory epithelium to get chemical stimuli via cila on their apical surfaces.

Front 67

What is the role of chemoreceptor?

Back 67

To function in taste and smell reception.

Front 68

Describe taste buds.

Back 68

Specialized non-neuronal sensory cells which transduce stimuli into electrical impulses that are passed onto neurons.

Front 69

Describe myenteric plexus of Auerbach.

Back 69

Provides intrinsic parasympathetic motor innervation to intestine. Clumps of parasympathetic nerves between layers of smooth muscle. A type of autonomic ganglia.