49 Questions
What is the approximate number of neurons in the nervous system?
100 million
Which component of a neuron is responsible for conducting electrical signals away from the cell body?
Axon
What is the main function of glial cells in the nervous system?
Supporting and protecting neurons
How many basic components make up a synapse?
3
Which type of cell is responsible for myelinization in the nervous system?
Glial cells
What is the role of the pericarion in a neuron's function?
Containing the nucleus and organelles
In which location can glial cells be classified according to the text?
Central nervous system
What is the primary function of a synapse in neural communication?
Transmitting chemical signals
What is the main function of satellite cells in the ganglia of the Peripheral Nervous System?
Insulating, nourishing, and regulating the microenvironments of neurons
In which part of the nervous system do Schwann cells form myelin around a segment of one axon?
Peripheral Nervous System
Which type of cells differentiate from precursors in the neural crest?
Schwann cells
What is the primary function of the cerebellar cortex?
Maintenance of balance and equilibrium
Which component of the nervous system originates in the CNS and transmits impulses for processing to the effector organs?
Autonomic system
What are the major regions of the Central Nervous System (CNS)?
Cerebrum, Cerebellum, and Spinal cord
What is the function of the white matter in the Central Nervous System (CNS)?
Myelinated axons and myelin-producing oligodendrocytes
What is the primary role of Schwann cells in the Peripheral Nervous System?
Forming myelin around axons
Which of the following components is responsible for synthesizing myelin sheaths around axons in the CNS?
Oligodendrocytes
What is the specialized region for synapsis called at the end point of each branch of the terminal arborization?
Terminal button
Which cell type constitutes the major mechanism of immune defense in the CNS?
Microglia
What is the primary function of astrocytes in the CNS?
Supporting neuronal survival and activities
Which type of synapse ensures that transmission is unidirectional?
Axoaxonic inhibitory synapse
Which cell type lines the ventricles of the brain and central canal of the spinal cord?
Ependymal cells
What is present in axoplasm but essentially no polyribosomes or RER?
Polyribosomes
What are the components released by synapses that usually bind specific receptor proteins to either open or close ion channels or initiate second-messenger cascades?
Neurotransmitters
What is the function of the glomeruli in the cerebellum?
To provide synaptic connections between granule cells and axons entering the cerebellum
Which type of fibers are found in the cerebellar medulla?
Myelinated and unmyelinated afferent and efferent fibers
What is the function of the spinal cord's gray matter?
To process and integrate sensory and motor information
What is the structure of peripheral nerves in the PNS?
Most are mixed, containing motor, sensory, and sometimes autonomic fibers
What is the function of Myenteric (Auerbach's) plexus in the enteric nervous system?
To regulate smooth muscle contraction in the digestive tract
How do unmyelinated fibers differ from myelinated fibers?
Unmyelinated fibers have a single layer of Schwann cells around each axon, while myelinated fibers have multiple layers
What is the function of Neuroglial cells in the spinal cord?
To process and integrate sensory and motor information
Which part of the neuron is the principal signal reception and processing site?
Dendrites
What is the trophic center for the entire neuron?
Perikaryon
Which type of neuron has a single process that bifurcates close to the perikaryon?
Pseudounipolar neuron
Where are pseudounipolar neurons found?
Spinal ganglia
Which type of neurons do not produce action potentials but regulate electrical changes of adjacent neurons?
Anaxonic neurons
What is the function of sensory neurons?
Receiving stimuli from receptors throughout the body
Which type of motor nerves control the 'involuntary' activities of glands, cardiac muscle, and most smooth muscle?
Autonomic motor nerves
Which region of the neuron contains a generally spherical nucleus with intense synthetic activity?
Perikaryon
Glomeruli are the synaptic places between granule cells and axons entering the cerebellum.
True
The spinal cord extends from the upper border of atlas to the lower border of L1.
True
The spinal cord occupies the lower 2/3 of the vertebral canal.
False
The peripheral nerves contain only motor fibers.
False
Schwann cells form myelin around only a portion of one axon in the CNS.
False
The autonomic nervous system includes the enteric nervous system.
True
Afferent fibers in the cerebellar medulla are only myelinated.
False
The gray matter of the spinal cord contains primarily neurons and processes of neurons.
True
Most peripheral nerve fibers are arranged radially.
False
The spinal cord terminates in a thick filament of gray matter.
False
Study Notes
Neurons (Nerve Cells)
- Neurons are the functional units of the nervous system
- They consist of three main parts: the cell body (perikaryon), dendrites, and axon
- Cell body (perikaryon) contains the nucleus and most of the cell's organelles, serving as the synthetic or trophic center
- Dendrites are numerous, elongated processes extending from the perikaryon, specialized to receive stimuli from other neurons at unique sites called synapses
- Axon is a single long process ending at synapses, specialized to generate and conduct nerve impulses to other cells
- Axons may also receive information from other neurons, mainly modifying the transmission of action potentials to other neurons
Classification of Neurons
- Multipolar neurons: one axon and two or more dendrites (e.g., pyramidal neurons in the cerebral cortex and Purkinje cells in the cerebellar cortex)
- Bipolar neurons: one dendrite and one axon (e.g., in the retina, olfactory mucosa, and inner ear)
- Pseudounipolar neurons: a single process that bifurcates close to the perikaryon, with one branch extending to a peripheral ending and the other to the CNS (e.g., in spinal ganglia and some cranial ganglia)
- Anaxonic neurons: many dendrites but no true axon, regulating electrical changes of adjacent neurons (e.g., in the CNS and retina)
Functional Properties of Neurons
- Sensory neurons: receive stimuli from receptors throughout the body, sending information to the CNS
- Motor neurons: send impulses to effector organs (muscle fibers and glands)
- Interneurons: establish relationships among other neurons, forming complex functional networks or circuits (e.g., in the CNS and retina)
Structure of the Neuron
- Cell body (perikaryon): contains the nucleus and surrounding cytoplasm, acting as the trophic center
- Dendrites: short, branching processes that receive and integrate stimuli from other neurons
- Axon: a long, cylindrical process that generates and conducts nerve impulses to other cells
Synaptic Communication
- Synapses are sites where nerve impulses are transmitted from one neuron to another or from neurons to other effector cells
- Synaptic transmission involves the release of neurotransmitters from the presynaptic axon terminal, which bind to receptors on the postsynaptic cell membrane
- Excitatory synapses: open Na+ channels, causing depolarization
- Inhibitory synapses: open Cl− or other anion channels, causing hyperpolarization
Glial Cells
- Support neuronal survival and activities
- Ten times more abundant than neurons in the mammalian brain
- Types of glial cells:
- Oligodendrocytes: produce myelin sheaths around axons in the CNS
- Astrocytes: provide structural and metabolic support to neurons, communicating with each other through gap junctions
- Ependymal cells: line the ventricles and central canal, facilitating the movement of cerebrospinal fluid
- Microglia: immune cells that defend the CNS against pathogens
- Schwann cells: form myelin sheaths around axons in the PNS
- Satellite cells: provide trophic support to neurons in ganglia
Test your knowledge of neuron anatomy with this quiz. Explore the structure and terminology related to motor neurons, axon hillock, axolemma, axoplasm, and terminal arborization.
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