(P) Lec 4: Nervous Tissue Flashcards
What are the three divisions of the Nervous System?
CNS, PNS, and Autonomic Nervous System
CNS is divided into which two main parts?
Brain and Spinal Cord
What are under PNS?
Cranial Nerves and Spinal Nerves
What are the two divisions of Autonomic Nervous System?
Sympathetic and Parasympathetic
How many cranial nerves do we have?
12
How many spinal nerves do we have?
31
What are the two types of cells in the CNS?
Neurons and Glial Cells
This type of cell in CNS has numerous long processes
Neurons
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
What are the three main parts of a neuron?
Cell body
Dendrite
Axon
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
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
These are unique sites that are specialized to receive stimuli from other neurons
Synapses
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
The neuron’s cell body is also referred to as?
Perikaryon or the Soma
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
What are the organelles inside the perikaryon?
Nucleus, Golgi Apparatus, Rough Endoplasmic Reticulum with Ribosomes
RER with ribosomes are otherwise known as?
Nissl Substance
Organelle in perikaryon
Spherical or oval and is large, pale-staining, and centrally located
Nucleus
Part of perikaryon
Contains Nissl granules which are basophilic
Cytoplasm
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
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
Axon’s plasma membrane is known as?
Axolemma
The axolemma has contents called?
Axoplasm
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?
- Sensory (Afferent)
- Motor (Efferent)
- 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?
6
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
