Nervous System and Nervous tissue1

Nervous System and Nervous tissue: Explain the organization of the nervous system. Describe the components of nervous tissue…

Nervous System and Nervous tissue

BIOL 2401L Lab Exercise 12

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

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.

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Neuron

Microglial cell

Microglial cells are defensive cells in the CNS.

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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

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

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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

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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

https://mediaplayer.pearsoncmg.com/assets/secs-ipweb-events-at-the-synapse

Video: nerve impulses (PhysioEx)

https://mediaplayer.pearsoncmg.com/assets/wet-lab-nerve-impulses

https://mediaplayer.pearsoncmg.com/assets/wet-lab-nerve-impulses