Introduction to the Nervous System and Nervous tissue
Learning Objectives
11.1 Explain the organization of the nervous system.
11.2 Describe the components of nervous tissue.
11.3 Identify the structures of a typical neuron.
11.4 Describe the different types of neurons and neuroglia.
11.5 Explain resting membrane potential and the major events of an action potential.
11.6 Differentiate between electrical and chemical synapses and identify the components of each.
Big picture: Nervous System
Summary of the structural and functional divisions of the nervous system
Major Types of Nervous Tissue
Nervous tissue
Glial tissueNeuron Multipolar
Bipolar Pseudounipolar
Peripheral nervous system: Schwann cells Satellite cells
Central nervous system: Astrocytes
Microglial cells Ependymal cells
Oligodendrocytes
Multipolar neuron: most common type
Dendrites (receptive regions)
Cell body (biosynthetic center and receptive region)
Axon (impulse-generating and –conducting region)
Neurons: generate the message (Nerve impulse = Action Potential)
3 basic features: 1. Cell body: nucleus and organelles
1. Nissl bodies: RER and free ribosomes 2. Microtubules and neurofilaments 3. Golgi, mitochondria + other standard cell
organelles
2. Dendrite: message receivers transmitting to cell body 1. Cannot generate an action potential
3. Axon: exits cell body to conduct messages 1. Generates action potential at the axon hillock 2. Plasma membrane: axolemma 3. Terminal branches: telodendria ending in axon
terminals
1. dendrite
2. Golgi body
3. axon from other neuron
4. nucleus
5. Nissl body (rough ER)
6. axon hillock
7. myelin sheath
8. nucleus of Schwann cell
9. node of Ranvier
10. mitochondrion
11. axon fiber
1. axon from other neuron
2. dendrite
3. Nissl body (rough ER)
4. nucleus
5. nucleolus
6. Golgi body
7. mitochondrion
8. axon hillock
9. axon fiber
10. node of Ranvier
11. nucleus of Schwann cell
12. myelin sheath
Video: neuron structure and function
https://mediaplayer.pearsoncmg.com/assets/secs-ipweb-nervous1- anat-rev
Can you name these neuron organelles and structures?
Multipolar neurons and their various processes.
–large nucleus and dense nucleolus, both of which are characteristic of neurons.
–Darkly staining Nissl bodies, composed of rough endoplasmic reticulum and free ribosomes.
–Small nuclei belong to the various neuroglial cells which, along with their processes and processes of the neurons, compose the neuropil, the matted appearing substance of gray matter.
http://kobiljak.msu.edu/cai/histology/Hist17_06.htm
Neuroglia Central nervous system (CNS)
The brain and spinal cord
• Astrocytes • Many arms anchor neurons and blood
vessels in place • Form the blood-brain barrier
• Microglial cells • Convert to macrophages (clean-up)
• Ependymal cells • Line the ventricles and central spinal canal;
circulate CSF
• Oligodendrocytes • One cell with many arms myelinating sites
on multiple neurons
Peripheral nervous system (PNS)
Cranial and spinal nerves
• Schwann cells • Myelinating cell
• One cell, one site on one axon
• Satellite cells • Similar function to astrocytes
© 2016 Pearson Education, Inc.
© 2013 Pearson Education, Inc.
Capillary
Neuron
Astrocyte
Astrocytes are the most abundant CNS neuroglia.
© 2013 Pearson Education, Inc.
Neuron
Microglial cell
Microglial cells are defensive cells in the CNS.
© 2013 Pearson Education, Inc.
Fluid-filled cavity Cilia
Ependymal cells
Brain or spinal cord tissue
Ependymal cells line cerebrospinal fluid–filled cavities.
© 2013 Pearson Education, Inc.
Myelin sheath
Process of oligodendrocyte
Nerve fibers
Oligodendrocytes have processes that form myelin
sheaths around CNS nerve fibers.
Model: oligodendrocyte
Name these glia of the Central Nervous System.
http://histologyguide.org/slideview/MHS-240-spinal- cord/06-slide-1.html?x=0&y=0&z=-1&page=1
© 2019 Pearson Education, Inc.
© 2019 Pearson Education, Inc.
Model: Schwann cell
The Big Picture of Action Potentials.
Label the following: – Axon – Axon terminals – Dendrite – Direction of action potential – Local potential – Voltage gated Na+ channel
© 2019 Pearson Education, Inc.
Number the events of the action potential from 1 to 5 in the order that they occur.
___ The axolemma returns to resting membrane potential.
___ An unstimulated neuron has a negative resting membrane potential.
___ Na+ channels inactivate and voltage-gated K+ channels activate, allowing K+ to flow out of the axon, and repolarization begins.
___ Local potentials accumulate to depolarize the membrane at the axon hillock
___ Voltage gated Na+ channels open and Na+ enters the axon, causing a depolarization in this section of the axon.
The structures of electrical and chemical synapses
© 2019 Pearson Education, Inc.
Model: Chemical synapse
© 2019 Pearson Education, Inc.
Big Picture: Chemical synaptic transmission
Creates the local potential
© 2016 Pearson Education, Inc.
Interactive Physiology video: Events at the synapse
https://mediaplayer.pearsoncmg.com/assets/secs-ipweb-events-at-the- synapse
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