Podcast
Questions and Answers
Which of the following correctly describes the main roles of the nervous system?
Which of the following correctly describes the main roles of the nervous system?
The Peripheral Nervous System (PNS) includes the brain and spinal cord.
The Peripheral Nervous System (PNS) includes the brain and spinal cord.
False
What are the two primary types of cells that make up nervous tissue?
What are the two primary types of cells that make up nervous tissue?
Neurons and Neuroglia
The ___________ are the most abundant neuralgia in the CNS.
The ___________ are the most abundant neuralgia in the CNS.
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Which type of neuron is characterized by having one short process that splits into peripheral and central processes?
Which type of neuron is characterized by having one short process that splits into peripheral and central processes?
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The somatic nervous system controls involuntary actions.
The somatic nervous system controls involuntary actions.
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In the Central Nervous System (CNS), what do cell bodies make up?
In the Central Nervous System (CNS), what do cell bodies make up?
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The ___________ cells in the PNS are also known as neurolemmocytes.
The ___________ cells in the PNS are also known as neurolemmocytes.
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Match the following types of neurons with their descriptions:
Match the following types of neurons with their descriptions:
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The ___________ nervous system is also referred to as the involuntary nervous system.
The ___________ nervous system is also referred to as the involuntary nervous system.
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Study Notes
Nervous System Overview
- The nervous system is the primary system controlling and coordinating the body
- It constantly monitors and processes sensory information from inside and outside the body
Nervous System Divisions
- Central Nervous System (CNS): Includes the brain and spinal cord.
- Peripheral Nervous System (PNS): Includes all parts outside the CNS, including nerves and sensory receptors
Nervous Tissue Cell Types
- Neurons: Handle communication and send signals.
- Neuroglia: Support and protect neurons
Neuroglia (Glial Cells)
- Also called "nerve glue"
- CNS: Astrocytes, oligodendrocytes, microglial cells, ependymal cells
- PNS: Schwann cells (neurolemmocytes), satellite cells
Functions of Neuroglia
- Support and protect fragile neurons
- Act as phagocytes (cleaning up waste and debris)
- Produce myelin for neuron extensions (oligodendrocytes in CNS, Schwann cells in PNS)
- Help with exchanges between capillaries and neurons
- Control the chemical surroundings of neurons (astrocytes)
Neuron Structure
- Cell body: Biosynthetic center, receives signals
- Dendrites: Receive signals from other neurons
- Axons: Send signals to other neurons or effector organs
Neurons (Nerve Cells)
- The basic functional units of nervous tissue.
- Specialized to send messages (nerve impulses) throughout the body.
Neuron Cell Body
- Contains the nucleus and other organelles needed for neuron function.
- Part of the receptive region, receives signals
Neuron Cell Body Structure
- Nucleus
- Neurofibrils: Cytoskeletal elements that support and aid transport within the neuron
- Chromatophilic substance: Clusters of rough endoplasmic reticulum, involved in making proteins.
Neuron Processes
- Dendrites: Receive signals
- Axons: Carry signals away from cell bodies
- Axon terminals: Endings of axons containing neurotransmitters.
Axon Terminals and Synapses
- Endings of axons
- Contain vesicles containing neurotransmitters for transmitting signals
- Connect with other neurons or effector cells at junctions called synapses
Myelin and Myelinated Fibers
- Many long nerve fibers covered by a fatty material called myelin
- A myelin sheath is made by Schwann cells, where they wrap tightly around the axon to form it in the PNS.
Discontinuous Myelin Sheath
- The myelin sheath isn't one continuous layer
- There are gaps called myelin sheath gaps or nodes of Ranvier between Schwann cells
Neuron Types
- Multipolar - multiple processes extending from cell body
- Bipolar - two processes extending from from cell body
- Unipolar (pseudounipolar) - single process extending from cell body
Classification by Function
- Sensory (Afferent): Carry signals toward the CNS
- Motor (Efferent): Carry signals away from the CNS
- Interneurons: Connect sensory and motor neurons
Structure of a Nerve
Endoneurium: Surrounds individual axons. Perineurium: Surrounds bundles of axons (fascicles). Epineurium: Encloses all fascicles, forming the nerve covering.
Cranial Nerves
- 12 pairs connected to the brain, primarily serving the head and neck
- Olfactory, optic, oculomotor, trochlear, trigeminal, abducens, facial, vestibulocochlear, glossopharyngeal, vagus, accessory, hypoglossal*
Spinal Cord Anatomy
- Encased within the vertebral canal and extends from the foramen magnum to the L1-L2 vertebra
- Protected by the meninges (dura mater, arachnoid mater, pia mater)
- Contains sensory and motor tracts.
Spinal Cord Damage
- Damage leads to loss of motor and sensory function in areas below the injury.
Spinal Cord Damage Consequences
- Paraplegia: Paralysis of both legs
- Quadriplegia: Paralysis of all four limbs
Spinal Nerves
- 31 pairs of mixed nerves that exit the spinal cord
- Divided into dorsal and ventral rami, forming nerve plexuses (networks of nerves)
- Each nerve supplies specific body regions (e.g., arms, legs)
Nerve Plexuses
- Networks of nerves formed by ventral rami
- Each plexus provides nerves for specific limb regions
- Cervical, Brachial, Lumbar, Sacral*
Reflexes
- Rapid, automatic, involuntary motor responses to stimuli
- Inborn or learned
- Involve sensory neurons, integration centers, motor neurons, and effectors
Autonomic Nervous System (ANS)
- Controls involuntary bodily functions:
- Smooth muscles, cardiac muscles, glands*
- Divided into sympathetic and parasympathetic divisions
Sympathetic Division & Parasympathetic Division
- Sympathetic division: "fight or flight"
- Prepares the body to respond to stressful or emergency situations*
- Parasympathetic division: "rest and digest"
- Promotes homeostasis and a relaxed state*
Aging and the Nervous System
- The sympathetic nervous system may become less efficient with age
- This can lead to orthostatic hypotension, a drop in blood pressure upon standing up because of decreased vasoconstriction.
Five Reflex Arc Components
- Receptor: Site of stimulus
- Sensory neuron: Carries impulses to the CNS
- Integration center: Processes information (monosynaptic or polysynaptic)
- Motor neuron: Carries impulses from the CNS
- Effector: Muscle fiber or gland that responds
Types of Reflexes
- Autonomic Reflexes (involuntary): Ex. Digestion, blood pressure, defecation
- Somatic Reflexes (voluntary): Ex. Stretch reflex, crossed extensor reflex, etc
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Description
Test your understanding of the nervous system, including its divisions and the different types of nervous tissue cells. This quiz covers the Central and Peripheral Nervous Systems, as well as the functions and importance of neurons and glial cells.
