Neurons are the cells of the nervous system and are found in the brain, spinal cord, and other nerves. The nervous system is responsible for sensory reception of signals outside the body, motor stimulation, and processing. Neurons come in many forms and create complex structures containing dendrites, axons, a myelin sheath, and various terminals, nodes, vesicles, and synapses. Signaling occurs via electric charges distributed over action potentials which are transmitted and maintained by sodium, calcium, and potassium ions. Neurons at rest have potentials of -70 mV. This lecture includes the steps of action potentials as well as Saltatory conduction, propagation of the signal, the role of synapses and neurotransmitters, and inhibition vs. excitation. Neurotransmitters include norepinephrine (noradrenaline) and epinephrine (adrenaline), dopamine, serotonin, and endorphins.
Action potentials are electrical changes along a neuron’s membrane that get a signal across the cell
Sodium and potassium are the main players in the electrical wave (it’s an all-or-none activity)
Action potential steps: threshold reached, depolarization, repolarization, hyperpolarization, and then back to resting potential
Saltatory conduction involves the electrical signaling jumping over myelin sheaths
Neurotransmitters get the signal across a synapse from the presynaptic neuron to its effector (typically a postsynaptic neuron)
Neurotransmitters have an excitatory or inhibitory effect on neurons or effected tissues
Examples of neurotransmitters: norepinephrine, dopamine, serotonin, and endorphins
Did you know…
Q: How many synapses are in the human body?
A: A LOT. In the brain alone, there are approximately 100 billion neurons and each of them has the capability to make thousands or 10s of thousands of connections with neighboring cells, so the number is probably in the 100s of trillions or more (if you include the brain, spinal cord, and peripheral nervous system.) The 100 trillion synapses of the brain go a long way…even though computers currently have the ability to be faster than the human brain, they don’t even come close to matching the storing power or complexity of the human brain.
Nervous System Part I: Neurons
Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.
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