Professor Long's Lecture on Anatomy and Physiology

Introduction

• Professor: Professor Long
• Context: Part of a series of online lectures due to coronavirus shutdown
• Audience: A&P 1 students (Biology 2401 or Human Anatomy & Physiology 1)
• Focus: Nervous System Lecture #6

Previous Topics in Series

• Flowchart of Nervous System: CNS, PNS, afferent/efferent, somatic/autonomic
• Sympathetic and Parasympathetic nervous systems
• Neuron morphology and shapes
• Ion channels, resting membrane potential, graded potentials
• Action potentials, summation (spatial & temporal), propagation, velocity, myelination

Current Focus: Synaptic Activity

• Synaptic activity at neuromuscular and neuro-neuronal junctions
• Key Components:
  • Axon terminals (T-loded end) and synaptic knobs
  • Synaptic cleft: gap between pre-synaptic and post-synaptic membranes
  • Neurotransmitter release and binding

Synaptic Transmission Steps

1. Action Potential Arrival:

   • Triggers voltage-gated calcium channels to open
   • Calcium ions (higher outside concentration) enter the neuron by diffusion

2. Neurotransmitter Release:

   • Calcium influx causes synaptic vesicles to fuse with presynaptic membrane
   • Neurotransmitter crosses the synaptic cleft

3. Neurotransmitter Binding:

   • Binds to receptors on post-synaptic membrane
   • Opens ion channels (chemically gated) affecting membrane potential

4. Signal Termination:

   • Calcium channels close, calcium actively pumped out
   • Neurotransmitter broken down by enzymes in the synaptic cleft

Synapses and Neurotransmitters

• Presynaptic Neuron: Releases a specific neurotransmitter
• Postsynaptic Membrane: Can have multiple receptor types for different neurotransmitters

Neurotransmitters Discussed

1. Acetylcholine:

   • Excitatory in skeletal muscle; inhibits in cardiac muscle
   • Related Enzyme: Acetylcholinesterase

2. Norepinephrine/Epinephrine (Adrenaline):

   • Excitatory for nervous system, skeletal and cardiac muscle

3. Dopamine:

   • Inhibitory in motor systems (prevents involuntary movements)
   • Excitatory in mood centers; associated with reward and pleasure
   • Related Enzyme: Monoamine oxidase (MAO)

4. Monoamines (Dopaminergic Synapses):

   • Includes serotonin (5-HT) and GABA
   • Involved in mood regulation, inhibitory in motor systems

Pharmaceutical and Drug Interactions

• Monoamine Oxidase Inhibitors (MAOIs):

  • Prevents breakdown of neurotransmitters, used for mood disorders

• Drugs Impacting Synapses:

  • Can block calcium channels, vesicle release, or neurotransmitter binding
  • Can mimic neurotransmitters or inhibit their breakdown (e.g., esterase inhibitors)

• Effects of Drug Abuse:

  • Down-regulation of receptors (e.g., from cocaine, methamphetamine use)
  • Potential permanent damage to mood regulation and synaptic function

Conclusion

• Understanding Synapses:

  • Key concepts: neurotransmitter types, synaptic transmission steps, drug effects
  • Broader implications for pharmacology and treatment of neurological conditions

• Next Steps: Preparation for Video #7 in the series

Note: Some specific drug effects and neurotransmitter interactions were discussed but not detailed for examination.