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Basic Physiology of Nerve and Muscle
Learning objectives:
- To gain an understanding of basic physiology of nerves and muscle
- To understand what a membrane potential is and what makes it happen
- To understand what an action potential is, and how it comes about
- To get a basic idea of how electrical signals in neurons and muscle fibers trigger other events
What makes neurons and muscle cells unique from other cells in the body is the way they process and generate electrical and chemical signals. This difference should not be understated - it separates the animal kingdom from all other life. Without this fundamental feature of neurons and muscle cells, we would not be able to think, move, or feel. Consciousness would be impossible.
The entire nervous system is made up of neurons. An understanding of what individual neurons do is crucial to understanding how neuroanatomical structures give rise to neurological function. This chapter provides an introduction to the workings of nerve and muscle cells.
There are 6 major concepts to take away from this chapter. The first is that Cells are Batteries. They generate an electrical potential (voltage) across the cell membrane. For most cells, this is identical to the DC current generated by a battery.
In the second section of this chapter, we explore the origin of the cell membrane potential.
Nerve cells (neurons) and muscle cells (muscle fibers) are specialized cells whose cell membrane potential can change. These changes contribute to the basic functioning of these cells. Nerve cell processes can carry electical signals similar to how wires do.
When the cell membrane of neurons or muscle fibers is depolarized enough, they propagate a nondecremental wave of electrical polarization called an action potential. Neurons use these action potentials to quickly transmit information across distance. Muscle fiber action potentials result in a mechanical contraction of the fiber, resulting in the production of force and motion.
Neurons can use electrical potentials to send signals from one part of the neuron to another, but to communicate with other neurons (or muscle cells or other target cells), they usually use chemical signals. These chemical signals are transmitted across specialized connections between cells called synapses.
Terminology:
By the end of this section, make certain that you understand what each of these terms mean, and can apply them appropriately. If applicable, make sure you can find each item on a whole brain, brain section, or image of a brain.
- Resting Membrane Potential
- Permeability
- Resistance
- Voltage Gating
- Ligand Gating
- Nersnt Equation
- Goldman Equation
- Ion Pump
- Na+/K+ ATPase
- Neuron
- Axon
- Dendrite
- Soma
- Myelin
- Conduction Velocity
- Temporal Summation
- Spatial Summation
- IPSP
- EPSP
- Action Potential
- All-or-None
- Nondecremental
- Voltage-gated Na+ channel
- Nodes of Ranvier
- Absolute Refractory Period
- Relative Refractory Period
- Myelin
- Saltatory conduction
- Actin
- Myosin
- Sarcomere
- Sarcoplasmic Reticulum
- Reuptake
- Synapse
- Neuromuscular Junction
- Presynaptic
- Postsynaptic
- Terminal bouton
- Synaptic cleft
- Acetylcholine
- Neurotransmitter
- Gap junctions
- Motor unit
Section 1: Cells are Batteries
Section 2: Why Are Cells Batteries?
Section 4: The Neuron Action Potential
Section 5: Muscle Fiber Action Potential
Section 6: Synapses and the Neuromuscular Junction (NMJ)
If you have any questions regarding this section, please ask them in the Neuroanatomy User Forum, or in the comments section at the bottom of this page.
