Nervous System Organization Quiz

Nervous System Organization

• The central nervous system (CNS) is comprised of the brain and spinal cord, processing and coordinating information.
• The peripheral nervous system (PNS) carries signals to and from the CNS.
• The afferent division of the PNS carries sensory input from receptors to the CNS.
• The efferent division of the PNS carries motor output from the CNS to effectors.
  • The somatic nervous system (SNS) controls voluntary movements of skeletal muscles.
  • The autonomic nervous system (ANS) controls involuntary functions like smooth muscle, cardiac muscle and glands.
    • The sympathetic division is responsible for "fight-or-flight" responses.
    • The parasympathetic division is responsible for "rest-and-digest" responses.
• The enteric nervous system (ENS) is a network of neurons in the gastrointestinal tract.

Glial Cells

• In the CNS:
  • Astrocytes maintain the blood-brain barrier, support structure, and regulate ion and neurotransmitter concentrations.
  • Oligodendrocytes myelinate CNS axons, increasing signal transmission speed.
  • Microglia act as immune cells, removing debris and pathogens.
  • Ependymal cells are a source of neural stem cells.
• In the PNS:
  • Schwann cells myelinate PNS axons, aiding in repair after injury.
  • Satellite cells surround neuronal cell bodies in ganglia, providing support and nutrient exchange.

Graded and Action Potentials

• Graded potentials are input signals that occur in dendrites and cell bodies, initiated by stimuli and can be summed.
• They are usually depolarizing or hyperpolarizing.
• Action potentials are regenerating conduction signals that travel through the axon, triggered by above-threshold graded potentials.
• They are all-or-none phenomena.

Action Potential Changes

• Resting phase: Resting membrane potential (approximately -70 mV) is maintained by the Na+/K+ pump and leak channels.
• Depolarization: Voltage-gated Na+ channels open, causing Na+ influx and a more positive membrane potential.
• Repolarization: Voltage-gated Na+ channels close, and voltage-gated K+ channels open, leading to K+ efflux and a return to resting potential.
• Hyperpolarization: K+ channels close slowly, resulting in an overshoot below resting potential before stabilizing.

Refractory Periods

• Absolute refractory period: No new action potential can be triggered due to inactivated Na+ channels.
• Relative refractory period: A stronger-than-normal stimulus can trigger a new action potential, as some Na+ channels are returning to their resting state, and K+ channels remain open.

Synaptic Communication

• Ionotropic receptors are ligand-gated ion channels mediating fast synaptic transmission. (e.g., AMPA receptors)
• Metabotropic receptors are G-protein-coupled receptors mediating slower, longer-lasting effects.
• Neurotransmitters are chemical messengers.
• Neuromodulators affect neurotransmitter release or receptor sensitivity.
• Fast synaptic potentials are brief changes in membrane potential due to ion flow.
  • Excitatory postsynaptic potentials (EPSPs) depolarize the membrane.
  • Inhibitory postsynaptic potentials (IPSPs) hyperpolarize the membrane.
• Slow synaptic potentials are longer-lasting changes mediated by second messengers.

Long-Term Potentiation (LTP)

• LTP is a strengthening of synaptic transmission through mechanisms involving AMPA and NMDA receptors.
• Initial signal involves glutamate binding to both AMPA and NMDA receptors.
• AMPA activation triggers Na+ influx, causing depolarization.
• NMDA activation, following depolarization, removes Mg2+ block and allows Ca2+ influx, leading to intracellular signaling and enhanced glutamate release.
• Result: Enhanced synaptic transmission, related to learning and memory.

Test your knowledge on the organization of the nervous system, including the structures and functions of the central and peripheral nervous systems, afferent and efferent divisions, and various nervous systems. This quiz also covers the roles of glial cells in the CNS. Challenge yourself and learn more about how our bodies process information!