![]() This post focuses on the latter, and explains why it is so significant for human movement. There are two main ways how muscle fibers are activated the size principle, and the all-or-none law. Dopamine – a CNS neurotransmitter, may be inhibitory or excitatory inhibitory – imp. Action potential: a brief reversal of electric polarization of the membrane of a nerve cell or muscle cell. Norepinephrine – in brain and ANS, has an excitatory, depolarizing effect on the postsynaptic membrane Dreaming, learning, emotions, sleeping, controls body temp. ![]() Released at neuromuscular junctions At many synapses in CNS At all neuron-to-neuron synapses in PNS At all neuromuscular and neuroglandular junctions within the parasympathetic division of the ANS Changes in cell polarization result in the signal being propagated down the length of the axon. Ans: The all-or-none law is associated with the stimulus causing changes in the neuron. Myelinated axons allows the action potential to travel faster Action potential travels only along the nodes Node to node – skips the internodes Faster and uses less energyġ1 General Properties Electrical – the Presynaptic & Postsynaptic membranes are locked together at gap junctions, start action potential more quickly Located int CNS & PNS but very rare Few areas of the brain, the eye & ciliary ganglia of the PNS Chemical – Presynaptic & Postsynaptic membranes do not touch, most abundant type Several types of neurotransmittersġ2 Cholinergic Synapses Release Acetylcholine (Ach) If a stimulus is strong enough, an action potential occurs and a neuron sends information down an axon away from the cell body and toward the synapse. Will open voltage-regulated sodium channels If less than -62 mV will produce a graded depolarization The action potential is independent of the relative strength of the depolarizing stimulus Like the pressure on the trigger of a gun: slight pressure gun does not fire, more pressure = gun firesĭepolarization to Threshold Activation of Sodium Channels & Rapid Depolarization (this is positive feedback) Inactivation of Sodium Channels & the Activation of Potassium Channels Return to Normal PermeabilityĪn action potential is propagated (moved) along an unmyelinated axon Action potential moves at the same speed along the entire length of the axon Moves at about 1 meter/second Similar to dominoes falling ![]() 1 Action Potential Action Potential The All-or-none PrincipleĢ All-or-None A threshold must be overcome (between -60 mV and - 55 mV)
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |