Neural Signaling

Introduction

• Lecture on neural signaling, focusing on the structure and function of the nervous system.
• More detail available for higher-level (HL) students.
• Importance of using resources like teachme.org for study and IB exam preparation.

Nervous System Overview

• Systems of the Body: Each with unique functions (e.g., cardiovascular, immune, digestive, respiratory).
• Nervous System: Composed of nerves (neurons), responsible for emotions, muscle control, sensation, and memory.
• Neurons: Specialized cells that carry electrical impulses across the body.

Components of the Nervous System

• Central Nervous System (CNS): Brain and spinal cord. Central to the body's midline.
• Peripheral Nervous System (PNS): Nerves extending from the CNS to the rest of the body.
  • Motor Neurons: Carry signals from CNS to muscles.
  • Sensory Neurons: Carry signals from sensory receptors to CNS.

Neuron Structure

• Cell Body: Contains nucleus, cytoplasm, and organelles.
• Dendrites: Receive electrical impulses from other neurons.
• Axon: Long fiber that transmits impulses, covered by myelin sheath (formed by Schwann cells).
• Terminal Branches and Buttons: Sends impulses to the next neuron.

Action Potential

• Resting Potential: Inside of neuron is negatively charged due to sodium-potassium pump (3 Na+ out, 2 K+ in).
• Depolarization: Sodium channels open, allowing Na+ into cell, creating positive charge inside.
• Repolarization: Potassium channels open, K+ exits cell, restoring negative charge inside.
• Sodium-Potassium Pump: Resets resting potential by restoring original ion distribution.

Synaptic Transmission

• Synapse: Space between neurons where neurotransmitters facilitate signal transmission.
• Neurotransmitters: Chemicals like acetylcholine released from presynaptic neuron, binding to postsynaptic receptors.
• Calcium Channels: Trigger neurotransmitter release into synaptic cleft.
• Enzymes: Breakdown neurotransmitters for recycling to prevent continuous firing.

Factors Affecting Impulse Speed

• Myelin Sheath: Insulates axon, allowing faster signal transmission via saltatory conduction.
• Axon Diameter: Larger diameter results in faster impulse conduction.

Correlation in Data Analysis

• Positive Correlation: As one variable increases, so does the other.
• Negative Correlation: As one variable increases, the other decreases.
• Correlation Coefficient (r): Quantifies strength and direction of a correlation (-1 to 1).

Key Concepts and Vocabulary

• Neuron vs Nerve: Neuron is a single cell; a nerve is a bundle of neurons.
• Membrane Potential: Charge difference across a membrane.
• Repolarization and Depolarization: Processes restoring and disrupting charge balance, respectively.

Conclusion

• Understanding neural signaling is crucial for comprehending how the nervous system controls various body functions.
• Reinforce learning through practice questions and case-based scenarios.

Practice Questions

1. Where do sensory neurons send signals to and from?
   • Answer: From sensory receptors in the PNS to the CNS.
2. Which neuron structure receives an electrical impulse from another neuron?
   • Answer: Dendrites.
3. By what means are neurotransmitters released into the synaptic cleft?
   • Answer: Exocytosis.