Electrical signals Sodium ions Potassium ions Generate an action potential at the axon hillock Travels down the axon to the terminal – regenerating the action potential in each portion of the membrane

synapse

neurotransmitters Chemical signals released by presynaptic neurons Bind to receptors on postsynaptic neuron or effector cells Stimulate or inhibit them 50+ different molecules have been identified Classified chemically and functionally

Other examples Histamine GABA Glutamate Glycine Endorphins

Postsynaptic membrane receptor Receive neurotransmitter Specialized to open/close ion channels Produces graded local change to membrane potential/voltage according to amount of NTM released and time it sticks around

Types of synapses Where the axon synapses with the postsynaptic cell Graded potentials dissipate in strength as spread – most effective type of synapse?

Effects Excitatory Synapses Depolarization (more +) of postsynaptic membrane Channels allow Na+ and K+ ions to diffuse simultaneously Local graded depolarization = EXCITATORY POSTSYNAPTIC POTENTIAL (EPSP) Helps trigger an action potential Inhibitory Synapses Induce hyperpolarization (more -) of postsynaptic membrane More permeable to K+, Cl- or both Less likely to “fire” an action potential, or requires a larger depolarizing current INHIBITORY POSTSYNAPTIC POTENTIAL (IPSP)

Neural integration Reflects sum of all incoming neural information received Both stimulatory and inhibitory inputs Axon hillock keeps a running account of all the signals it receives

modeling Seekers: must find the right message Neuron chain, standing hand to hand – once stimulated, must pass the message from one person to the next until reaches axon hillock. Axon hillock: keeps a running total of the charge

Problem solve: how do you get your message to “win”? Must adhere to the same rules…but can alter everything else

Summation: add together to influence activity of post-synaptic neuron temporal 1 or more presynaptic neurons transmit impulses in rapid-fire order Quick succession, before signal dissipates spatial Postsynaptic neuron stimulated by a large number of terminals from same or different neurons at the same time Large number of receptors bind neurotransmitters