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Questions and Answers
What type of cells ensheath PNS axons with myelin?
What type of cells ensheath PNS axons with myelin?
Which statement best describes the role of oligodendrocytes in the CNS?
Which statement best describes the role of oligodendrocytes in the CNS?
What happens to myelin in Multiple Sclerosis?
What happens to myelin in Multiple Sclerosis?
What are the gaps in the myelin sheath called?
What are the gaps in the myelin sheath called?
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Which structure shields every axon in the PNS from extraceullar fluid?
Which structure shields every axon in the PNS from extraceullar fluid?
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What is the primary function of the central nervous system (CNS)?
What is the primary function of the central nervous system (CNS)?
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Which structure of a neuron is responsible for receiving input?
Which structure of a neuron is responsible for receiving input?
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What is the function of the axon hillock in a neuron?
What is the function of the axon hillock in a neuron?
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Which of the following best describes the function of neurofibrils?
Which of the following best describes the function of neurofibrils?
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Which component of the nervous system is mainly responsible for muscle contraction and gland secretion as a response to information?
Which component of the nervous system is mainly responsible for muscle contraction and gland secretion as a response to information?
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What forms the fatty myelin sheaths around axons in the peripheral nervous system?
What forms the fatty myelin sheaths around axons in the peripheral nervous system?
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What distinguishes gray matter from white matter in the nervous system?
What distinguishes gray matter from white matter in the nervous system?
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Study Notes
Nervous System - Part 1: Basic Structure & Function
- The nervous system is a communicator and control system
- The central nervous system (CNS) includes the brain and spinal cord
- The peripheral nervous system (PNS) includes peripheral nerves connecting the CNS to other body parts
Functions of CNS and PNS
- Sensory function: Detects stimuli inside and outside the body via sensory receptors in the PNS; sensory impulses/signals are sent to the CNS to create sensations, memories, and thoughts
- Integration function: Processes and evaluates sensory information. The CNS takes sensory impulses & creates sensations, memories, and thoughts.
- Motor function: Responds to information by sending impulses from the CNS through the PNS to effectors (muscles and glands) to cause a response
- Sensory input: Sensory nerves detect stimuli and send information from receptors to the CNS
- Motor output: Motor nerves send information from the CNS to effectors
Neuron Structure
- Neurons are nerve cells that vary in shape and size but generally have the following components:
- Soma (cell body): large nucleus with a prominent nucleolus
- Neurofibrils: bundles of neurofilaments (proteins) that extend into axons and dendrites, providing tensile strength and forming the cytoskeleton
- Nissl bodies: darkly staining membranous packets containing clusters of rough ER and free ribosomes; give gray matter its color
- Dendrites: variable number of branches from the soma, function in receiving input and transferring it to the cell body; abundant surface area for receiving information.
- Axon hillock: slightly elevated region off the soma that gives rise to the axon
- Axons: one long, cylindrical process off the soma, conducts action potentials and releases neurotransmitters at synaptic knobs
Neuron Structure (continued)
- Axon terminals and synaptic knobs: many fine extensions at the end of an axon, each extension ending in a synaptic knob close to another cell; separated by a space/cleft.
Matching
- Soma- Main body of the neuron
- Neurofibrils – structure that provides strength to neuron
- Nissl bodies – Structures that give gray matter its color
- Dendrites-Finger-like extensions off soma
- Axon hillock-Connects axon to soma
- Axon – Long branch extending away from soma
Axons - Myelinated
- Fatty, lipid-rich sheaths around axons insulate them.
- Formed by Schwann cells (PNS, aka neurolemmocytes): elongated, flat cells that ensheath PNS axons with myelin; allows for faster action potential propagation
- Oligodendrocytes (CNS): Large cells with slender extensions; wrap around axons of neurons forming myelin sheath
Axons - Unmyelinated
- No myelin sheath; axons not insulated from ECF.
- Still protected by a Schwann cell, but not wrapped (neurilemma)
Axons - Neurilemma
- Every axon in the PNS is shielded from ECF by Schwann cells, whether myelinated or not
- Portions of the Schwann cell with the nucleus and most of the cytoplasm comprise the neurilemma sheath
- One Schwann cell can wrap around ~15 axons
Axons - Nodes of Ranvier
- Gaps in the myelin sheath between Schwann cells/oligodendrocytes
- Help speed up nerve signal transmission
Clinical Application - Multiple Sclerosis
- Autoimmune disease: Immune system attacks myelin in the CNS
- Scleroses (plaques) form in myelin
- Symptoms include impaired coordination
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Description
Explore the fundamental components of the nervous system in this quiz. Learn about the roles of the central and peripheral nervous systems, including sensory, integration, and motor functions. Test your knowledge on how the nervous system communicates and controls bodily functions.
