40 Questions
What is the main function of neuroglial cells or glia cells?
Supporting, protecting, and nourishing neurons
What is the term for the structural and functional unit of the nervous tissue?
Neurons or nerve cells
What is the term for the part of the neuron that receives stimuli from other neurons?
Dendrite
What is the term for the type of neuron that has many dendrites but no true axon?
Anaxonic neurons
What is the term for the type of neuron that receives sensory stimuli?
Sensory neuron
What is the term for the part of the cell body that contains the nucleus and surrounding cytoplasm?
Perikaryon
What is the term for the clusters of RER plus free polyribosomes found in the cytoplasm of the cell body?
Nissl body
What is the term for the single long process that generates and conducts nerve impulses to other cells?
Axon
What is the main function of the myelin sheath?
To facilitate the formation of action potentials along the axolemma
What is characteristic of unmyelinated nerve fibers?
They are enveloped within simple clefts of the Schwann cells
What is unique about the structure of dendrites?
They are the initial processing sites for synaptic signals
What is the function of nerves?
To establish communication between the CNS and sense organs and effectors
What is unique about mixed nerves?
They contain both myelinated and unmyelinated fibers
What is the function of the axon hillock?
It is the region where the nerve impulse is initiated
Which organelles are typically absent in axons?
Cisternae of RER
What is the function of free nerve endings?
To respond to temperature and pain
What surrounds the actual nerve endings in encapsulated nerve endings?
A special connective tissue capsule
What is the purpose of endocytosis in neurons?
To take up macromolecules, viruses, and toxins
Where are nodes of Ranvier located?
Between adjacent Schwann cells on an axon
What is the purpose of the axon?
To transmit nerve impulses
Which type of synapse uses a chemical mediator?
Chemical synapse
What is the function of Meissner's corpuscle?
Reception of light touch
What is the term for the gaps between adjacent Schwann cells on an axon?
Nodal gaps
Where are lamellar corpuscles typically found?
In deep skin, joint capsules, and ligaments
What is the purpose of the synaptic cleft?
To provide a gap between the pre- and postsynaptic membranes
What happens when the nerve impulse reaches the presynaptic terminal?
The neurotransmitter is released by exocytosis
What is the function of muscular spindles?
Detection of changes in muscle length
What is the function of a motor neuron?
To supply motor fibers to muscles and glands
What is the structure of a motor end plate?
Terminal dilating as a plate-like mass
What is the role of synaptic vesicles in the motor end plate?
To release acetylcholine
What is the result of the binding of acetylcholine to receptors on the sarcolemma?
Action potential in the sarcolemma
What is the final result of the signal transmission at the motor end plate?
Sliding filament mechanism of muscle contraction
What is the result of calcium channels opening in the process of neurotransmission?
Calcium influx into the cytoplasm
What is the main function of astrocytes in the CNS?
Structural and metabolic support of neurons
What type of astrocyte is found in the white matter of the CNS?
Fibrous astrocyte
What is the function of oligodendrocytes in the CNS?
Myelination of axons
What is the function of microglia in the CNS?
Protection of the CNS from infectious agents
What is the function of ependymal cells in the CNS?
Production and circulation of cerebrospinal fluid
What is the function of Schwann cells in the PNS?
Myelination of axons
What is the function of satellite cells in the PNS?
Electrical insulation of PNS cell bodies
Study Notes
Characteristics of Nervous Tissue
- Made up of two types of cells: nerve cells (neurons) and neuroglial cells (glia)
- Neurons:
- Structural and functional unit of nervous tissue
- Responsible for reception, transmission, and processing of stimuli
- Release neurotransmitters or other molecules
- Neuroglial cells:
- Support, protect, and nourish neurons
- Form neural network and circuits with neurons via synapses
Structure of Neurons
- Three main parts:
- Cell body (perikaryon or soma): trophic center with nucleus and surrounding cytoplasm
- Dendrites: numerous elongated processes receiving stimuli from other neurons
- Axon: single long process generating and conducting nerve impulses to other cells
Types of Neurons
- Classified based on number of processes:
- Anaxonic neurons: multiple dendrites, no true axon
- Bipolar neurons: one dendrite and one axon
- Unipolar or pseudounipolar neurons: single process dividing into two
- Multipolar neurons: multiple dendrites and one axon
- Classified based on functional roles:
- Sensory neurons (afferent): receive sensory stimuli
- Motor neurons (efferent): send impulses to effector organs
- Interneurons: establish relationships among other neurons
Neuron Structure
- Perikaryon:
- Large, spherical, and pale-staining nucleus
- Coarse or fine basophilic particles (Nissl bodies) and microtubules
- Neurofilaments and neurofibrils
- Dendrites:
- Short and thick, devoid of Golgi complex
- Dendritic spines: initial processing sites for synaptic signals
- Axon:
- Single process, usually long and thin with uniform diameter
- Axon hillock: conical region
- Axolemma and axoplasm
- Branches: terminal arborization and collaterals
- Organelles: few polyribosomes or cisternae of RER
Nerve Impulse Transmission
- Electrochemical process initiated at the axon hillock
- Wave of membrane depolarization via voltage-gated Na+ and K+ channels
- Transmission is unidirectional at synapses
Synapses
- Chemical synapse: uses a chemical mediator (neurotransmitter)
- Electrical synapse: permits direct flow of electrical current
- Structure:
- Presynaptic axon terminal (terminal bouton) with mitochondria and synaptic vesicles
- Synaptic cleft: extracellular space between pre- and postsynaptic membranes
- Postsynaptic cell membrane with receptors for neurotransmitters and ion channels
Neuroglial Cells
- Astrocytes:
- Most numerous glial cells
- Large, radiating processes with bundles of intermediate filaments (GFAP)
- Function: structural and metabolic support of neurons, especially at synapses
- Oligodendrocytes:
- Fewer processes
- Function: myelinate and insulate CNS axons
- Microglia:
- Small cells with mobile processes
- Function: protect CNS by engulfing infectious agents and other harmful substances
- Ependymal cells:
- Low columnar epithelial cells with cilia and processes
- Function: assist in production and circulation of cerebrospinal fluid
- Schwann cells:
- Surround and insulate PNS axons
- Form myelin around segments of one axon
- Satellite cells:
- Form a layer around PNS neuron cell bodies
- Function: electrically insulate PNS cell bodies and regulate nutrient and waste exchange
Peripheral Nerves
- Bundles of nerve fibers (axons) individually surrounded by Schwann cells and connective tissue
- Myelinated and unmyelinated nerve fibers
Nerve Endings
- Free nerve endings:
- Devoid of myelin sheath
- Distribute in skin, cornea, hair follicle, and CT
- Responsible for temperature and pain
- Encapsulated nerve endings:
- Special connective tissue capsule surrounds the actual nerve endings
- Tactile corpuscles, lamellar corpuscles, and muscular spindles
Motor Nerve Endings
- Terminal structure of the axon of motor neuron
- Supply muscular tissue and glands
- Form effectors with muscle fibers
This quiz covers the general characteristics of nervous tissue, including its composition, function, and structure. It delves into the roles of neurons and neuroglial cells, and how they interact to form neural networks and circuits.
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