A&P Exam

• Functions of the Nervous System


  • Sensory input: Gathering information
  • Integration: Processing and interpreting sensory input
  • Motor output: Responding to integrated stimuli by activating effector organs
• Organization of the Nervous System

  • Central Nervous System (CNS): Brain and spinal cord
  • Peripheral Nervous System (PNS): Nerves outside the CNS
  • PNS branches into: Somatic Nervous System (voluntary control), Autonomic Nervous System (involuntary control)
  • Sympathetic Division: "Fight or flight" response
  • Parasympathetic Division: Rest and digest response
• Neuroglial Cells


  • Smaller than neurons, support cells
  • Found throughout the nervous system
  • Provide support, insulation, and nutrients to neurons
• Motor Neuron Structures


  • Dendrites: Receive signals
  • Cell body (soma): Contains nucleus
  • Axon: Sends signals
  • Axon terminals: Release neurotransmitters
• Anterograde


  Forward movement
• Retrograde


  Backward movement
• White matter


  Myelinated axons
• Gray matter


  Neuronal cell bodies
• Structural Classes of Neurons

  • Multipolar: Multiple dendrites, one axon (most common in CNS)
  • Bipolar: One dendrite, one axon (e.g., sensory neurons in retina)
  • Unipolar: Single process extends from cell body (e.g., sensory neurons in PNS)
• Functional Classes of Neurons

  • Sensory: Transmit sensory information to CNS
  • Motor: Carry signals from CNS to effectors
  • Interneurons: Process information within CNS
• Ion Channels


  • Leakage channels
  • Gated channels: Voltage-gated, ligand-gated, mechanically gated
• Electrochemical gradient


  Difference in ion concentration and charge across a membrane
• Voltmeter


  Measures electrical potential
• Resting membrane potential


  Electrical charge difference across a cell membrane
• Resting membrane potential is generated by ion concentration gradients, with higher Na+ and Cl- extracellularly and higher K+ intracellularly, maintained by the Na+/K+ pump
• Generating a Graded Potential

  1. Local change in membrane potential

  2. Stimulus causes ion channels to open

  3. Magnitude varies with stimulus strength
• Generating an Action Potential

  1. Rapid depolarization and repolarization

  2. Threshold reached, voltage-gated Na+ channels open

  3. Positive feedback loop
• Graded Potential


  Variable strength, decremental
• Action Potential


  All-or-nothing, non-decremental
• Stronger stimuli


  More frequent action potentials
• Refractory Periods


  • Absolute: No action potential possible
  • Relative: Action potential requires stronger stimulus
• Velocity of Action Potential

  • Diameter of axon and myelination affect speed
• Continuous vs. Saltatory Conduction

  • Continuous: Unmyelinated, slower conduction
  • Saltatory: Myelinated, faster conduction
• Multiple Sclerosis (MS)


  • Autoimmune disorder attacking myelin
  • Symptoms: Muscle weakness, fatigue, impaired coordination
  • Treatment: Medications to manage symptoms, physical therapy
• Axon Fiber Types


  • Type A: Largest diameter, myelinated, fastest (e.g., motor neurons)
  • Type B: Medium diameter, myelinated (e.g., autonomic neurons)
  • Type C: Smallest diameter, unmyelinated, slowest (e.g., sensory neurons)
• Neuronal Connections


  • Electrical synapses (less common)
  • Chemical synapses (more common)
• Synaptic Connections


  • Axodendritic: Axon to dendrite
  • Axosomatic: Axon to soma
• Activities in Synaptic Transmission

  1. Presynaptic: Neurotransmitter release

  2. Synapse: Neurotransmitter diffusion

  3. Postsynaptic: Receptor activation, potential change
• EPSP


  Excitatory postsynaptic potential
• IPSP


  Inhibitory postsynaptic potential
• Temporal summation


  Summation of signals over time
• Spatial summation


  Summation of signals from different sources
• The language of neurons is electrical impulses and chemical signals, classified by neurotransmitters and receptors
• Neurotransmitters


  • Acetylcholine (ACh)
  • Dopamine
  • Serotonin
  • Norepinephrine (NE)
  • Glutamate
  • GABA
  • Glycine
• Functions and Disorders of Neurotransmitters

  • ACh: Excitatory (muscle contraction), Alzheimer's
  • Dopamine: Pleasure, Parkinson's, schizophrenia
  • Serotonin: Mood regulation, depression
  • NE: Arousal, depression
  • Glutamate: Excitatory, epilepsy
  • GABA: Inhibitory, anxiety disorders
  • Glycine: Inhibitory, hyperekplexia
• Effects of Neurotransmitters


  • Excitatory: Increase postsynaptic potential
  • Inhibitory: Decrease postsynaptic potential
• Direct vs. Indirect Actions

  • Direct: Neurotransmitter binds directly to ion channel
  • Indirect: Neurotransmitter binds to receptor, activates second messenger
• Neural integration


  Processing and interpretation of multiple signals
• Neuronal pool


  Interconnected neurons performing a specific function
• Reflexes


  Involuntary responses involving sensory input, integration, and motor output