(P) Lec 4: Nervous Tissue Flashcards by Denica Shealtiel Enage

What are the three divisions of the Nervous System?

CNS, PNS, and Autonomic Nervous System

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CNS is divided into which two main parts?

Brain and Spinal Cord

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What are under PNS?

Cranial Nerves and Spinal Nerves

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What are the two divisions of Autonomic Nervous System?

Sympathetic and Parasympathetic

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How many cranial nerves do we have?

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How many spinal nerves do we have?

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What are the two types of cells in the CNS?

Neurons and Glial Cells

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This type of cell in CNS has numerous long processes

Neurons

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These are cells in the CNS that have short processes and they:
* Support and protect neurons
* Participate in many neural activities, neural nutrition, and defense of cells in the CNS

Glial cells

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What are the three main parts of a neuron?

Cell body
Dendrite
Axon

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Part of neuron which:

■ Contains the nucleus and most of the cell’s organelles
■ Serves as the synthetic or trophic center for the entire nerve cell

Cell body

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Part of the neuron which:

■ Numerous elongated processes extending from the perikaryon
■ Specialized to receive stimuli from other neurons at unique sites called SYNAPSES

Dendrites

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These are unique sites that are specialized to receive stimuli from other neurons

Synapses

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Part of the neuron which:

■ Single long process ending at synapses specialized to generate and conduct nerve impulses to the other cells
■ In charge with the transmission or ‘sending away’ of electrical impulses to be received by other neurons

Axon

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The neuron’s cell body is also referred to as?

Perikaryon or the Soma

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Part of the neuron

○ It is the tropic center or the nutritive center, as well as the genetic center of the neuron.
○ It is also the part that encloses the nucleus and other organelles necessary to maintain and repair the neuron.

Perikaryon/Soma/Cell body

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What are the organelles inside the perikaryon?

Nucleus, Golgi Apparatus, Rough Endoplasmic Reticulum with Ribosomes

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RER with ribosomes are otherwise known as?

Nissl Substance

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Organelle in perikaryon

Spherical or oval and is large, pale-staining, and centrally located

Nucleus

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Part of perikaryon

Contains Nissl granules which are basophilic

Cytoplasm

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Part of neuron

○ Receives and carry information towards the cell body
○ Are usually multiple
○ Are relatively short
○ Are often branched
○ Have receptors for neurotransmitters
○ Conduct local potentials

Dendrites

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Part of neuron

○ Carries information to another neuron or muscle cell
○ Are typically longer than dendrites
○ May have collateral branches
○ Are covered by NEURILEMMA made up of SCHWANN CELLS

Axon

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Axon’s plasma membrane is known as?

Axolemma

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The axolemma has contents called?

Axoplasm

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Axon originates in which part?

Axon Hillock

The neurolemma of axons are made up of what?

Schwann cells

What are the classifications of neurons according to function?

1. Sensory (Afferent) 2. Motor (Efferent) 3. Inter-neurons

Classification of neurons according to function They receive stimuli from receptors throughout the body. ○ They are involved in the transmission of sensory stimuli from the environment or within the body ○ Impulse is transmitted to the CNS

Sensory (Afferent)

Classification of neurons according to function They send impulses to effector organs such as muscle fibers and glands. ○ They transmit impulses from the CNS to the effector organs (skeletal muscle) or from other efferent neurons that ultimately supply the effectors (smooth muscles, cardiac muscles, and glands)

Motor (Efferent)

Two types of motor neurons

Somatic motor nerves Autonomic motor nerves

Classification of neurons according to function ○ Associated neurons that transmit impulses from one part of the CNS to another ○ Their processes do not leave the CNS.

Inter-neurons

What are the classifications of neurons according to the number of processes?

Multipolar Neurons Bipolar Neurons Unipolar Neurons Anaxonic Neurons

Classification of neurons according to number of processes ○ have one axon and two or more dendrites ○ They have more than two processes; there is a single axon and multiple dendrites

Multipolar Neurons

Classification of neurons according to number of processes ○ have one dendrite and one axon ○ They have two processes separated by the cell body

Bipolar Neurons

Classification of neurons according to number of processes ○ Also referred to as pseudounipolar neurons ○ They have a single process that bifurcates close to the perikaryon, with the longer branch extending to a peripheral ending and the other toward the CNS ○ They have a single elongated process, with the cell body situated off to the side

Unipolar Neurons

Classification of neurons according to number of processes ○ They have many dendrites but have no true axon ○ They have more than two processes, but axons cannot be distinguished from dendrites.

Anaxonic Neurons

What are the classifications of neurons according to structure?

Pseudounipolar Bipolar Multipolar

Classification of neurons according to structure Examples of this are cerebro-spinal ganglia or sensory ganglia located at the dorsal root of the spinal cord

Pseudounipolar

Classification of neurons according to structure Examples of this are retina, spiral and vestibular ganglia of the inner ear, and olfactory mucosa

Bipolar

Classification of neurons according to structure motor neurons of the CNS and peripheral autonomic ganglia

Multipolar

This is a structure that permits a neuron or nerve cell to pass an electrical or chemical signal to another neuron or to the target effector cell.

Synapse

This is a contact area of one axon with the dendrites or perikaryon of another that passes polarity

Synapse

This involves: ■ Telodendron Membrane (Presynaptic Membrane) ■ Synaptic Cleft ■ Postsynaptic Membrane

Synapse

Neuroglial cells are otherwise known as?

Glial cells

These cells support the neuronal survival and activities

Neuroglial cells

Neuroglial cells are how many times more abundant than neurons?

10 times

How many types of neuroglial cells are there?

What are the glial cells found in the CNS?

■ Astrocytes ■ Microglia ■ Oligodendrocytes ■ Ependymal Cells

What are the glial cells found in the PNS?

■ Satellite Cells ■ Schwann cells.

T or F: Glial cells synapse with other cells

False

CNS Glial Cell: → the largest, most important in the CNS → the nucleus is spherical, centrally located, and pale-staining → processes have expanded pedicles at their ends

Astrocyte

Type of Astrocyte: Found in the gray matter; abundant in granular cytoplasm and processes have many branches but are shorter and relatively thick

Protoplasmic

Type of Astrocyte: Found in the white matter; cytoplasm shows fibrillar material and processes are long, slender, and smooth that branch infrequently

Fibrous

CNS Glial Cell: → are smaller; nuclei are round, small, and dense → cytoplasm is electron dense → processes are less numerous and shorter → found in both gray and white matter → precursor of myelin sheaths

Oligodendrocytes

CNS Glial Cell: → cell bodies are smaller, denser, and elongated; are cigar-shaped → nuclei are made up of condensed chromatin and has an elongated shape → processes have a thorny appearance → found in both gray and white matter (are phagocytic) → originates from the mesenchyme while others are derived from the ectoderm → lines the cavities where CSF flows but does not produce CSF itself

Microglia

CNS Glial Cell: → supporting cells that line the central canal of the spinal cord and ventricular cavities of the brain → cells are squamous cuboidal/columnar-shaped with wide bases → surfaces are provided with cilia during embryonic life → nuclei are elongated, round, or oval in shape

Ependymal Cells

CNS: → has an outer cortex of gray matter and an inner medulla of white matter → the parenchyma of the cortex is the Pyramidal Cells of Betz

Cerebrum

CNS: → an outer gray matter of cortex and inner cerebellar medulla → has three layers: 1. Molecular layer 2. Purkinje cell layer 3. Granular layer → the white medulla is composed of myelinated nerve fibers and glial cells

Cerebellum

CNS: → has an inner core of gray matter - anterior/ventral horns and posterior/dorsal horns are joined at the center by a thin gray matter (central commissure) surrounding the central canal - neurons are found in the gray matter including the neuroglial cells → has an outer core or white matter composed of myelinated nerve fibers and neuroglial cells

Spinal Cord

Meninges: → contains dense connective tissue → outermost layer

Dura Mater

Meninges: → a delicate impermeable membrane made up of loose connective tissue devoid of blood vessels → cobweb-like appearance

Arachnoid Mater

Meninges: → contains loose connective tissue → innermost layer

Pia Mater

Meninges: - space between the arachnoid and pia mater

Sub-arachnoid space

Peripheral nerves can be myelinated or unmyelinated as they can ONLY be lined by what cell type?

Schwann Cells (myelination is derived form here)

A bimolecular lipoprotein complex that is interrupted at the Nodes of Ranvier

Myelin Sheath

Coverings of Peripheral Nerves: → outermost connective tissue sheet covering all bundles of fibers in a nerve

Epineurium

Coverings of Peripheral Nerves: → middle connective tissue sheet covering individual bundles of fibers

Perineurium

Coverings of Peripheral Nerves: → innermost sheet covering the individual axons of each fiber in a bundle

Endoneurium

These are: → aggregations of nerve cell bodies outside the CNS → ovoid structures encapsulated with dense connective tissue and associated with nerves

Ganglia

These are: → found at the dorsal roots of all spinal nerves and some cranial nerves → are sensory in nature → nerve cells are of the pseudounipolar type → surrounded by a capsule of dense connective tissue

Cranio-Spinal Ganglia

These are: - Large, oval or spheroidal-shaped - Nuclei are large, rounded, and centrally-located - Lined by cellular fibrous connective tissue elements - Inner aspect of this investment consists of flattened cells closely applied to the plasma membrane of the neuron - Satellite cells or inner capsule cells

Ganglion Cells

Other name for cranio-spinal ganglia

Dorsal Root Ganglia/Sensory Ganglia

Location of sympathetic ganglia

T12 and L2 or L3

Location of parasympathetic ganglia

S2 - S4

Type of Ganglia: - Neurons are the multipolar type - Are oval-shaped structures - Nuclei are eccentrically located, large, and oval-shaped - Nissl’s substance may be distributed throughout the cytoplasm or confined to the perinuclear zone or peripheral cytoplasm - Lipofuscin granules are more frequent - Surrounded by a layer of satellite cells but less numerous

Autonomic Ganglia