PNS 2/24

Overview of the Nervous System

• The nervous system is a complex network that allows communication throughout the body, facilitating responses to external stimuli.

Membrane Potential and Nerve Signals

• Membrane Potential: Refers to the electrical charge across a cell membrane due to differences in ion concentrations. This electrical potential is crucial for the generation of nerve signals (action potentials).

• Action Potentials: Rapid rises and falls in voltage across a neuron's membrane that transmit signals along nerves.

Anatomy of the Nerve Cell

• Neurons: The basic building blocks of the nervous system, consisting of:

  • Dendrites: Receive signals from other neurons.

  • Cell Body (Soma): Contains the nucleus and integrates incoming signals.

  • Axon: Transmits electrical impulses away from the cell body to other neurons or muscles.

  • Axon Terminals: Release neurotransmitters into the synaptic cleft to communicate with other neurons.

Synaptic Transmission

• Neurotransmitters: Chemicals that transmit signals across a synapse from one neuron to another, influencing various physiological responses.

• Synapse: The junction where communication occurs between neurons. It includes:

  • Presynaptic Neuron: Releases neurotransmitters.

  • Synaptic Cleft: Space between neurons.

  • Postsynaptic Neuron: Receives neurotransmitters, leading to either excitation or inhibition of the signal.

Integration into Larger Networks

• Sensory inputs and autonomic activities are integrated, demonstrating how signals from different sources work together to produce coordinated responses.

• Example: Pupil Response: The process of the pupil dilating or constricting in response to light involves:

  • Photoreceptors: Detect changes in light intensity.

  • Brain Stem: Processes the sensory information.

  • Autonomic Pathways: Adjust pupil size through muscular responses in the iris.

Conclusion

• Understanding these intricate pathways highlights the complexity of body functions. In every moment, multiple systems work together to respond to external stimuli, reflecting the interconnected nature of body physiology.