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1H06 Anatomy & Physiology 1H06: Membrane Potentials.docx

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McMaster University
Health Sciences
Alexander Ball

Membrane Potentials Neurons communicate using: 1. Graded potentials (short-distance communication) 2. Action potentials (long-distance communication within body) a. Action potential in muscle fiber is muscle action potential b. When action potential occurs in nerve cell, it is called nerve action potential. What happens when you touch a pen? 1. Graded potential builds in sensory receptor in fingertips 2. Graded potential triggers axon to form nerve action potential, travels into CNS, causing release of neurotransmitter at synapse with an interneuron. 3. Neurotransmitter stimulates interneuron to form graded potential in its dendrites and cell body 4. Axon of interneuron forms nerve action potential, which travels along axon, resulting in neurotransmitter release at next synapse with another interneuron. 5. This occurs repeatedly until interneurons in cerebral cortex are activated, then perception occurs and you can feel the pen. Ion Channels  Ions travel down electrochemical gradient  Positively charged cations move toward negatively charged area, and vice versa 4 types of ion channels: (pg. 461) 1. Leak channels a. Randomly alternate between open and closed positions b. Many more K+ leak channels than Na+ channels, so membrane’s permeability to K+ is larger than permeability to Na+ 2. Ligand-gated channel a. Opens and closes in response to binding of ligand (chemical) stimulus b. Neurotransmitters, hormones, particular ions can open and close them 3. Mechanically gated channel a. Opens or closes in response to mechanical stimulation in form of vibration b. Force distorts channel from resting position, opening the gate 4. Voltage-gated channel a. Opens in response to a change in membra
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