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

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Neuron Synapses I. Anatomy of the Synapse II.Chemical Synapse III.EPSP & IPSP IV.Neurotransmitters
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Page 1: Neuron Synapses I.Anatomy of the Synapse II.Chemical Synapse III.EPSP & IPSP IV.Neurotransmitters.

Neuron Synapses

I. Anatomy of the Synapse

II. Chemical Synapse

III. EPSP & IPSP

IV. Neurotransmitters

Page 2: 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

Page 3: Neuron Synapses I.Anatomy of the Synapse II.Chemical Synapse III.EPSP & IPSP IV.Neurotransmitters.

The Neuron Synapse

Junction between 2 neurons

Ion Channels

Presynaptic Neuron

PostsynapticNeuron

Synaptic Cleft

Secretory Vesicles w/ neurotransmitters

Page 4: Neuron Synapses I.Anatomy of the Synapse II.Chemical Synapse III.EPSP & IPSP IV.Neurotransmitters.

Release of Neurotransmitters

Postsynaptic Neuron

Presynaptic Neuron

Page 5: Neuron Synapses I.Anatomy of the Synapse II.Chemical Synapse III.EPSP & IPSP IV.Neurotransmitters.

The Neuron Synapse

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

Page 6: Neuron Synapses I.Anatomy of the Synapse II.Chemical Synapse III.EPSP & IPSP IV.Neurotransmitters.

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

Page 7: Neuron Synapses I.Anatomy of the Synapse II.Chemical Synapse III.EPSP & IPSP IV.Neurotransmitters.

Neuron Synapses

I. Anatomy of the Synapse

II. Chemical Synapse

III. EPSP & IPSP

IV. Neurotransmitters

Page 8: Neuron Synapses I.Anatomy of the Synapse II.Chemical Synapse III.EPSP & IPSP IV.Neurotransmitters.

Nerve Communication Across Synapses

AP must reach axon terminal

Page 9: Neuron Synapses I.Anatomy of the Synapse II.Chemical Synapse III.EPSP & IPSP IV.Neurotransmitters.

Nerve Communication Across Synapses

1. AP opens voltage-gated _________ channels. _________ enters axon terminal

Page 10: Neuron Synapses I.Anatomy of the Synapse II.Chemical Synapse III.EPSP & IPSP IV.Neurotransmitters.

Nerve Communication Across Synapses

2. Synaptic vesicles fuse with _________ membrane

Page 11: Neuron Synapses I.Anatomy of the Synapse II.Chemical Synapse III.EPSP & IPSP IV.Neurotransmitters.

Nerve Communication Across Synapses

3. Neurotransmitter release into synaptic _________

Page 12: Neuron Synapses I.Anatomy of the Synapse II.Chemical Synapse III.EPSP & IPSP IV.Neurotransmitters.

4. Neurotransmitters bind to chemically-gated ionchannels

Nerve Communication Across Synapses

Page 13: Neuron Synapses I.Anatomy of the Synapse II.Chemical Synapse III.EPSP & IPSP IV.Neurotransmitters.

5. Ions (Na+ or K+) enter/leave postsynaptic neuron through chemically-gated ion channel

Nerve Communication Across Synapses

Page 14: Neuron Synapses I.Anatomy of the Synapse II.Chemical Synapse III.EPSP & IPSP IV.Neurotransmitters.

6. Neurotransmitter effect terminated

1. Removal by _____________

2. Diffusion

Nerve Communication Across Synapses

Page 15: Neuron Synapses I.Anatomy of the Synapse II.Chemical Synapse III.EPSP & IPSP IV.Neurotransmitters.

Clinical Application: Botulinum toxin

Page 16: Neuron Synapses I.Anatomy of the Synapse II.Chemical Synapse III.EPSP & IPSP IV.Neurotransmitters.

Clinical Application: VX Nerve Gas

Page 17: Neuron Synapses I.Anatomy of the Synapse II.Chemical Synapse III.EPSP & IPSP IV.Neurotransmitters.

Clinical Application: VX Nerve Gas

Page 18: Neuron Synapses I.Anatomy of the Synapse II.Chemical Synapse III.EPSP & IPSP IV.Neurotransmitters.

Neuron Synapses

I. Anatomy of the Synapse

II. Chemical Synapse

III. EPSP & IPSP

IV. Neurotransmitters

Page 19: Neuron Synapses I.Anatomy of the Synapse II.Chemical Synapse III.EPSP & IPSP IV.Neurotransmitters.

Function of Neurotransmitters

• Effect may be fast or slow

Page 20: Neuron Synapses I.Anatomy of the Synapse II.Chemical Synapse III.EPSP & IPSP IV.Neurotransmitters.

Function of Neurotransmitters

• Effect may be fast or slow

• Can excite or inhibit AP in ___________ neuron

Page 21: Neuron Synapses I.Anatomy of the Synapse II.Chemical Synapse III.EPSP & IPSP IV.Neurotransmitters.

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

Page 22: Neuron Synapses I.Anatomy of the Synapse II.Chemical Synapse III.EPSP & IPSP IV.Neurotransmitters.

Excitatory Postsynaptic Potential (EPSP)

• Neurotransmitter causes small depolarization

Page 23: Neuron Synapses I.Anatomy of the Synapse II.Chemical Synapse III.EPSP & IPSP IV.Neurotransmitters.

Excitatory Postsynaptic Potential (EPSP)

• Neurotransmitter causes small depolarization

• Na+ enters postsynaptic neuron and/or K+ leaves postsynaptic neuron Self-defeating?

Page 24: Neuron Synapses I.Anatomy of the Synapse II.Chemical Synapse III.EPSP & IPSP IV.Neurotransmitters.

Inhibitory Postsynaptic Potential (IPSP)

• Neurotransmitter causes small hyperpolarization

Page 25: Neuron Synapses I.Anatomy of the Synapse II.Chemical Synapse III.EPSP & IPSP IV.Neurotransmitters.

Inhibitory Postsynaptic Potential (IPSP)

• Neurotransmitter causes small hyperpolarization

• K+ leaves postsynaptic neuron

Page 26: Neuron Synapses I.Anatomy of the Synapse II.Chemical Synapse III.EPSP & IPSP IV.Neurotransmitters.

• Produce graded potential in post-synaptic membrane

EPSP’s & IPSP’s

Page 27: Neuron Synapses I.Anatomy of the Synapse II.Chemical Synapse III.EPSP & IPSP IV.Neurotransmitters.

• Produce graded potential in post-synaptic membrane

• Cause slight change in membrane potential (~1 mV)

EPSP’s & IPSP’s

Page 28: Neuron Synapses I.Anatomy of the Synapse II.Chemical Synapse III.EPSP & IPSP IV.Neurotransmitters.

• Produce graded potential in post-synaptic membrane

• Cause slight change in membrane potential (~1 mV)

• Axon Hillock keeps “running account”

EPSP’s & IPSP’s

Page 29: Neuron Synapses I.Anatomy of the Synapse II.Chemical Synapse III.EPSP & IPSP IV.Neurotransmitters.

1) AP initiated at axon hillock (voltage-gated channels)

Axon hillock

Page 30: Neuron Synapses I.Anatomy of the Synapse II.Chemical Synapse III.EPSP & IPSP IV.Neurotransmitters.

1) AP initiated at axon hillock (voltage-gated channels)

2) IPSPs can prevent axon hillock from reaching threshold

Axon hillock

Page 31: Neuron Synapses I.Anatomy of the Synapse II.Chemical Synapse III.EPSP & IPSP IV.Neurotransmitters.

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

Page 32: Neuron Synapses I.Anatomy of the Synapse II.Chemical Synapse III.EPSP & IPSP IV.Neurotransmitters.

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.

Page 33: Neuron Synapses I.Anatomy of the Synapse II.Chemical Synapse III.EPSP & IPSP IV.Neurotransmitters.

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.

Page 34: Neuron Synapses I.Anatomy of the Synapse II.Chemical Synapse III.EPSP & IPSP IV.Neurotransmitters.

Summation of EPSP’s & IPSP’s

No summation Temporal summation

Spatialsummation

Summation ofEPSP and IPSP

Me

mbr

an

e P

ote

ntia

l (m

V)

E1 & E2 = EPSP ; I1 = IPSP

Page 35: Neuron Synapses I.Anatomy of the Synapse II.Chemical Synapse III.EPSP & IPSP IV.Neurotransmitters.

Spatial & Temporal Summation Analogy

EPSP is student popping bubblegum

AP is professor getting annoyed

Page 36: Neuron Synapses I.Anatomy of the Synapse II.Chemical Synapse III.EPSP & IPSP IV.Neurotransmitters.

Spatial & Temporal Summation Analogy

EPSP is student popping bubblegum

AP is professor getting annoyed

Temporal Summation:How frequently one student pops a bubble

Page 37: Neuron Synapses I.Anatomy of the Synapse II.Chemical Synapse III.EPSP & IPSP IV.Neurotransmitters.

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

Page 38: Neuron Synapses I.Anatomy of the Synapse II.Chemical Synapse III.EPSP & IPSP IV.Neurotransmitters.

EPSP’s, IPSP’s & Your Bladder

Page 39: Neuron Synapses I.Anatomy of the Synapse II.Chemical Synapse III.EPSP & IPSP IV.Neurotransmitters.

EPSP’s & the Lesson of Tyco Brahe

Page 40: Neuron Synapses I.Anatomy of the Synapse II.Chemical Synapse III.EPSP & IPSP IV.Neurotransmitters.

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!


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