Neuron Synapses I.Anatomy of the Synapse II.Chemical Synapse III.EPSP & IPSP IV.Neurotransmitters

Neurons signal is One Way Communication between neurons at synapse AP converted to chemical signal, a ________________ Stimulation of neuron might lead to an AP Communication Between Neurons

The Neuron Synapse Junction between 2 neurons Ion Channels Presynaptic Neuron Postsynaptic Neuron Synaptic Cleft Secretory Vesicles w/ neurotransmitters

Release of Neurotransmitters Postsynaptic Neuron Presynaptic Neuron

The Neuron Synapse Each neuron has 1,000 – 10,000 axon terminals forming a synapse

The Neuron Synapse Types of Synapses : 1. Axon – Dendrite synapse 2. Axon – Muscle synapse 3. Axon – Gland synapse Each neuron has 1,000 – 10,000 axon terminals forming a 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 _________

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 Nerve Communication Across Synapses

Clinical Application: Botulinum toxin

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

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” EPSP’s & IPSP’s

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 Axon hillock

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.

Summation of EPSP’s & IPSP’s No summation Temporal summation Spatial summation Summation of EPSP and IPSP Membrane Potential (mV) E 1 & E 2 = EPSP ; I 1 = 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

Tyco’s overstretched bladder exploded Died 11 agonizing days later Moral of the Story: Listen to your EPSP’s!