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Questions and Answers
Which part of the neuron is the receptive area that contains the nucleus?
Which part of the neuron is the receptive area that contains the nucleus?
Dendrites carry impulses away from the cell body.
Dendrites carry impulses away from the cell body.
False
Name the two main types of cells that compose nervous tissue.
Name the two main types of cells that compose nervous tissue.
Neurons and Neuroglia
A _______ neuron has one axon and one dendrite.
A _______ neuron has one axon and one dendrite.
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Which structure is NOT a component found in the cytoplasm of a neuron?
Which structure is NOT a component found in the cytoplasm of a neuron?
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Match the neuron classification with its description:
Match the neuron classification with its description:
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Neuroglia are known as nerve cells.
Neuroglia are known as nerve cells.
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What term is used for age-related pigment that represents undigested material in neurons?
What term is used for age-related pigment that represents undigested material in neurons?
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What type of synapse is characterized by the release of neurotransmitters?
What type of synapse is characterized by the release of neurotransmitters?
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Anaxonic neurons produce action potentials.
Anaxonic neurons produce action potentials.
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What are the three components that make up a chemical synapse?
What are the three components that make up a chemical synapse?
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The peripheral nervous system (PNS) is formed mainly of __________, __________, and __________.
The peripheral nervous system (PNS) is formed mainly of __________, __________, and __________.
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Which cells are responsible for the formation of the myelin sheath in the peripheral nervous system?
Which cells are responsible for the formation of the myelin sheath in the peripheral nervous system?
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Match the types of synapses to their descriptions.
Match the types of synapses to their descriptions.
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Myelinated nerve fibers are enclosed by a layer of myelin called the myelin sheath.
Myelinated nerve fibers are enclosed by a layer of myelin called the myelin sheath.
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The outermost covering of a whole nerve is known as the __________.
The outermost covering of a whole nerve is known as the __________.
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Study Notes
Nervous Tissue Overview
- Nervous tissue comprises two main cell types: neurons and neuroglia.
- Neurons are the functional units of the nervous system, responsible for transmitting signals.
- Neuroglia (glial cells) provide support and protection to neurons.
Neuron Structure
- The neuron's structure involves a cell body (soma/perikaryon) and cell processes (neurites).
- The cell body contains the nucleus and cytoplasm, with specialized components like Nissl granules, neurofibrils, and specific pigments such as lipofuscin and melanin.
- Neurites include dendrites, receiving impulses, and axons, carrying impulses away from the cell body.
Neuron Classification
- Neurons are classified according to the number of processes extending from the cell body.
- Unipolar neurons have a single process that divides into two branches.
- Bipolar neurons have one axon and one dendrite.
- Multipolar neurons have one axon and many dendrites.
- Anaxonic neurons have numerous dendrites but lack a distinct axon.
Synapse
- Synapses are specialized junctions connecting neurons.
- Chemical synapses involve neurotransmitter release, creating a delay in signal transmission.
- Electrical synapses do not involve neurotransmitters, allowing rapid signal transmission through direct ion channels.
Chemical Synapse Structure
- Chemical synapses consist of a presynaptic side (neuron), a postsynaptic side (neuron or effector cell), and a synaptic cleft, the gap between the two sides.
- The presynaptic side contains synaptic vesicles with neurotransmitters.
- The postsynaptic side has receptors for neurotransmitters.
Synapse Classification
- Axodendritic: axon to dendrite
- Axosomatic: axon to cell body
- Axoaxonic: axon to axon
Peripheral Nervous System (PNS)
- The PNS comprises nerves, ganglia, and nerve endings.
- Ganglia are ovoid structures containing neuronal cell bodies and surrounding glial cells, encased in a connective tissue capsule.
- Spinal ganglia, and sympathetic ganglia are examples.
Peripheral Nerve Structure
- Peripheral nerves are bundles of nerve fibers held together by connective tissue.
- Fascicles, groups of fibers, are enveloped by perineurium.
- Individual nerve fibers are enclosed in endoneurium.
- The entire nerve is surrounded by epineurium.
Myelinated and Unmyelinated Nerve Fibers
- Myelinated axons are surrounded by a myelin sheath, a fatty insulating layer that speeds up signal transmission.
- Schwann cells in the PNS and oligodendrocytes in the CNS form the myelin sheath.
- Nodes of Ranvier are gaps in the myelin sheath, where signal transmission "jumps" between them, a process called saltatory conduction.
Myelin Sheath Formation
- Myelin sheath is formed through invagination of the axon into Schwann cell / oligodendrocyte.
- The subsequent rotation of the cell around the axon forms multiple layers of the myelin sheath.
- Each Schwann cell provides the myelin sheath for a short segment of the axon.
Ganglia: Types and Features
- Ganglia come in different types, each categorized by features like shape, size, arrangement of cells, presence of satellite cells, and the presence of a capsule.
- Typical features include CT capsules, blood vessels, cells, shaped and arranged differently, and numbers of satellite cells.
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