Transcript Slides
Neuron Synapses I. Anatomy of the Synapse II. Chemical Synapse III. EPSP & IPSP IV. Neurotransmitters Communication Between Neurons • Neurons signal is One Way • Communication between neurons at synapse • AP converted to chemical signal, a ________________ • Stimulation of neuron might lead to an AP The Neuron Synapse Junction between 2 neurons Secretory Vesicles w/ neurotransmitters Presynaptic Neuron Synaptic Cleft Postsynaptic Neuron Ion Channels Release of Neurotransmitters Presynaptic Neuron Postsynaptic Neuron The Neuron Synapse Each neuron has 1,000 – 10,000 axon terminals forming a synapse The Neuron Synapse Each neuron has 1,000 – 10,000 axon terminals forming a synapse Types of Synapses: 1. Axon – Dendrite synapse 2. Axon – Muscle synapse 3. Axon – Gland synapse Neuron Synapses I. Anatomy of the Synapse II. Chemical Synapse III. EPSP & IPSP IV. Neurotransmitters Nerve Communication Across Synapses AP must reach axon terminal Nerve Communication Across Synapses 1. AP opens voltage-gated _________ channels. _________ enters axon terminal Nerve Communication Across Synapses 2. Synaptic vesicles fuse with _________ membrane Nerve Communication Across Synapses 3. Neurotransmitter release into synaptic _________ Nerve Communication Across Synapses 4. Neurotransmitters bind to chemically-gated ion channels Nerve Communication Across Synapses 5. Ions (Na+ or K+) enter/leave postsynaptic neuron through chemically-gated ion channel Nerve Communication Across Synapses 6. Neurotransmitter effect terminated 1. Removal by _____________ 2. Diffusion Clinical Application: Botulinum toxin Clinical Application: VX Nerve Gas Clinical Application: VX Nerve Gas Neuron Synapses I. Anatomy of the Synapse II. Chemical Synapse III. EPSP & IPSP IV. Neurotransmitters Function of Neurotransmitters • Effect may be fast or slow Function of Neurotransmitters • Effect may be fast or slow • Can excite or inhibit AP in ___________ neuron Function of Neurotransmitters • Effect may be fast or slow • Can excite or inhibit AP in ___________ neuron • Determined by neurotransmitter interaction with receptor on postsynaptic membrane Excitatory Postsynaptic Potential (EPSP) • Neurotransmitter causes small depolarization Excitatory Postsynaptic Potential (EPSP) • Neurotransmitter causes small depolarization • Na+ enters postsynaptic neuron and/or K+ leaves postsynaptic neuron Self-defeating? Inhibitory Postsynaptic Potential (IPSP) • Neurotransmitter causes small hyperpolarization Inhibitory Postsynaptic Potential (IPSP) • Neurotransmitter causes small hyperpolarization • K+ leaves postsynaptic neuron EPSP’s & IPSP’s • Produce graded potential in post-synaptic membrane EPSP’s & IPSP’s • Produce graded potential in post-synaptic membrane • Cause slight change in membrane potential (~1 mV) EPSP’s & IPSP’s • Produce graded potential in post-synaptic membrane • Cause slight change in membrane potential (~1 mV) • Axon Hillock keeps “running account” Axon hillock 1) AP initiated at axon hillock (voltage-gated channels) Axon hillock 1) AP initiated at axon hillock (voltage-gated channels) 2) IPSPs can prevent axon hillock from reaching threshold Axon hillock 1) AP initiated at axon hillock (voltage-gated channels) 2) IPSPs can prevent axon hillock from reaching threshold 3) Multiple EPSPs are required to reach threshold Summation of Graded Potentials Can Trigger Action Potential EPSP’s Reach Threshold Via: Temporal Summation occurs when a single synapse is activated repeatedly over a short time period. Summation of Graded Potentials Can Trigger Action Potential EPSP’s Reach Threshold Via: Temporal Summation occurs when a single synapse is activated repeatedly over a short time period. Spatial Summation occurs when multiple synapses are activated at the same time. Membrane Potential (mV) Summation of EPSP’s & IPSP’s No summation Temporal summation Spatial summation Summation of EPSP and IPSP E1 & E2 = EPSP ; I1 = IPSP Spatial & Temporal Summation Analogy EPSP is student popping bubblegum AP is professor getting annoyed Spatial & Temporal Summation Analogy EPSP is student popping bubblegum AP is professor getting annoyed Temporal Summation: How frequently one student pops a bubble Spatial & Temporal Summation Analogy EPSP is student popping bubblegum AP is professor getting annoyed Temporal Summation: How frequently one student pops a bubble Spatial Summation: Every student in front row popping bubbles EPSP’s, IPSP’s & Your Bladder EPSP’s & the Lesson of Tyco Brahe EPSP’s & the Lesson of Tyco Brahe Tyco’s overstretched bladder exploded Died 11 agonizing days later Moral of the Story: Listen to your EPSP’s!