Nervous System and Muscular System Overview

I. General Overview of the Nervous System

  • Functions: Communication, control, coordination of body activities.

  • Cell types: Neurons and neuroglia.

  • Divisions: Central Nervous System (CNS) and Peripheral Nervous System (PNS).

  • Pathways: Afferent (sensory) and efferent (motor).

  • Definitions: Neuron (nerve cell), nerve fiber (axon), nerve (bundle of fibers).

II. Neurons and Neuroglia

  • Structure: Dendrites, cell body, axon, axon hillock, synaptic knob.

  • Myelination: Myelin, neurilemma, nodes of Ranvier, Schwann cells.

  • Types: Myelinated (faster) vs unmyelinated (slower) axons; white matter (myelinated) vs gray matter (unmyelinated).

  • Multiple sclerosis: Caused by immune attack on myelin, symptoms include motor dysfunction.

  • Types of neurons: Sensory, interneurons, motor neurons; six types of neuroglia with diverse functions.

  • Regeneration: Peripheral axon can regenerate if the neurilemma is intact.

III. Membrane Potential and Action Potentials

  • Polarized cell membrane: Charge difference across membrane.

  • Sodium/potassium pump maintains resting potential; typical = −70-70 mV.

  • Gated ion channels influence membrane potential.

  • Graded potential vs action potential: Localized change vs active electrical impulse.

  • Threshold potential initiates action potential.

  • Events: Depolarization, repolarization, hyperpolarization, refractory periods (important for impulse propagation).

IV. Synaptic Transmission

  • Synapse: Junction between neurons for signal transmission.

  • Neurotransmitters: Excitatory (EPSP) vs inhibitory (IPSP); effect varies based on type.

  • Summation: Process of adding EPSPs/IPSPs for net effect, occurs at integration sites.

V. Neurotransmitters and Drug Effects

  • Function of neurotransmitters: Chemical signals for communication.

  • Drugs: Cocaine and nicotine affect neurotransmitter release and action.

  • Agonists (activate receptors) vs antagonists (block receptors).

  • Imbalances: Parkinson's (dopamine deficiency) and schizophrenia (dopamine and serotonin dysregulation).

VI. Neural Integration and Processing

  • Neuronal pools: Networks of neurons for impulse processing.

  • Facilitation increases action potential likelihood.

  • Convergence (multiple inputs) and divergence (single input to multiple outputs) in pathways.