Introduction to the Nervous System

Sep 10, 2024

Mindmap

Anatomy and Physiology: Introduction to the Nervous System

Instructor: Professor Mariah Evans

Course: BSC 2085

Overview

  • This lecture introduces the nervous system, part of a series covering both muscles and the nervous system for an upcoming test.
  • The nervous system is a fast-acting master controller, integrating electrical and chemical signals to respond rapidly and specifically to stimuli.

Main Functions of the Nervous System

  1. Sensory Input: Receiving stimuli.
  2. Integration: Processing and decision-making regarding stimuli.
  3. Motor Output: Response execution via effectors (skeletal muscle, smooth muscle, cardiac muscle, and glands).

Structure of the Nervous System

  • Central Nervous System (CNS): Composed of the brain and spinal cord.
  • Peripheral Nervous System (PNS): Pathways to/from the CNS, including cranial nerves (12 pairs) and spinal nerves (31 pairs).
    • Sensory (Afferent) Pathways: Carrying signals to the CNS.
    • Motor (Efferent) Pathways: Carrying commands from the CNS to effectors.
    • Somatic Nervous System: Controls voluntary actions in skeletal muscle.
    • Autonomic Nervous System: Controls involuntary actions in smooth muscle, cardiac muscle, and glands.
      • Sympathetic Division: Activates fight or flight responses.
      • Parasympathetic Division: Oversees rest and digest processes.

Neuronal Structure

  • Neurons (Nerve Cells): Composed of a cell body (soma), dendrites, and usually a single axon.
    • Dendrites: Receive signals.
    • Axons: Transmit output signals to effectors or other neurons.
    • Myelination: Increases speed of impulse transmission.

Types of Neurons

  • Multipolar: Multiple dendrites, one axon.
  • Bipolar: One dendrite, one axon.
  • Unipolar: A single process extending in both directions.

Supporting Cells (Neuroglia)

  • CNS Supporting Cells:
    • Astrocytes: Most abundant, anchor neurons to capillaries.
    • Microglia: Phagocytic, clean debris.
    • Ependymal Cells: Line cavities, involved in circulation of cerebrospinal fluid.
    • Oligodendrocytes: Myelinate CNS axons.
  • PNS Supporting Cells:
    • Satellite Cells: Surround neuron cell bodies in the PNS.
    • Schwann Cells: Myelinate PNS axons, aiding in rapid signal transmission.

Neuron Functionality

  • Polarization: Resting state; inside negative relative to outside.
  • Depolarization: Positive influx, leading to action potential (excitation).
  • Repolarization: Return to resting state.
  • Hyperpolarization: More negative, causing inhibition.

Action Potentials

  • Travel long distances without losing strength.
  • Involve opening of voltage-gated ion channels.
  • Speed influenced by axon diameter and myelination.

Synapses

  • Chemical Synapses: Neurotransmitter release for communication.
  • Electrical Synapses: Less common, direct ion flow.
  • Excitatory/Inhibitory Postsynaptic Potentials (EPSPs/IPSPs): Determine neuron firing.

Neurotransmitters

  • Acetylcholine: Excitatory in skeletal muscle, inhibitory in cardiac muscle.
  • Dopamine, Epinephrine (Adrenaline), Serotonin: Various roles in mood, excitement.
  • Glutamate: Generally excitatory.
  • GABA (Gamma-Aminobutyric Acid): Generally inhibitory.

Summary

  • The nervous system is integral for rapid response and controls numerous body functions through intricate pathways and neurotransmitter actions.
  • Detailed knowledge of neuronal mechanisms, neurotransmitters, and their effects is crucial for understanding nervous system physiology.

This introduction sets the stage for detailed exploration of central and peripheral nervous systems in subsequent lectures.