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Anatomy & Physiology: Nervous System Fundamentals

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  • Functions of the nervous system

    Sensory input: gathers information from sensory receptors.
    Integration: processes and interprets sensory input.
    Motor output: activates muscles and glands to respond.

  • Central nervous system (CNS)

    Includes the brain and spinal cord; acts as the integrating and control center interpreting sensory input and dictating motor output.

  • Peripheral nervous system (PNS)

    All nervous system parts outside the CNS, mainly nerves and ganglia; links the body to the CNS.

  • Neuroglia

    Supporting cells of the nervous system that maintain and protect neurons; include astrocytes, microglia, ependymal cells, oligodendrocytes in CNS, and Schwann and satellite cells in PNS.

  • Neuron characteristics

    Excitable cells with extreme longevity, amitotic nature, and high metabolic rate; specialized for conducting nerve impulses.

  • Resting membrane potential

    Voltage difference across a resting neuron's membrane, typically around −70 mV, caused by ion concentration differences and membrane permeability.

  • Graded potentials

    Short-lived, localized changes in membrane potential that vary in strength and occur in dendrites or cell bodies.

  • Action potentials

    Brief, long-distance electrical signals generated in axons, involving depolarization and repolarization phases.

  • Myelin sheath function

    Insulates axons to protect nerve fibers and increase the speed of nerve impulse transmission.

  • Schwann cells vs. oligodendrocytes

    Schwann cells myelinate axons in the PNS; oligodendrocytes myelinate axons in the CNS.

  • Types of neurons by structure

    Multipolar (most common, many dendrites, one axon), bipolar (one dendrite, one axon), unipolar (single process dividing into two branches).

  • Types of neurons by function

    Sensory (afferent) neurons transmit impulses to CNS; motor (efferent) neurons transmit impulses from CNS; interneurons connect neurons within CNS.

  • Ohm's Law in neurons

    Current (I) = Voltage (V) / Resistance (R); voltage drives ion flow across membranes, resistance opposes it.

  • Ion channels types

    Leakage (always open), chemically gated (open with neurotransmitter), voltage-gated (open with membrane potential changes), mechanically gated (open with physical deformation).

  • Synapse

    Junction between two neurons where signals are transmitted chemically or electrically.

  • Chemical synapse transmission steps

    Action potential arrives → Ca2+ channels open → neurotransmitter released → neurotransmitter binds postsynaptic receptors → ion channels open → postsynaptic potential generated.

  • Excitatory postsynaptic potential (EPSP)

    Depolarizes postsynaptic membrane, increasing likelihood of action potential generation.

  • Inhibitory postsynaptic potential (IPSP)

    Hyperpolarizes postsynaptic membrane, decreasing likelihood of action potential generation.

  • Neurotransmitter effect depends on

    The type of receptor it binds to, which determines whether the effect is excitatory or inhibitory.

  • Acetylcholine (ACh)

    Neurotransmitter released at neuromuscular junctions and autonomic neurons; excitatory in skeletal muscle, inhibitory in cardiac muscle.

  • Biogenic amines

    Include dopamine, norepinephrine, epinephrine, serotonin, and histamine; involved in emotional behavior and biological clock regulation.

  • Action potential propagation

    Self-propagating wave of depolarization along the axon, moving in one direction due to refractory periods.

  • Saltatory conduction

    Fast action potential propagation in myelinated axons where impulses jump between nodes of Ranvier.

  • Absolute refractory period

    Time during which a neuron cannot fire another action potential because Na+ channels are inactivated.

  • Relative refractory period

    Period following absolute refractory period when a stronger-than-normal stimulus can trigger an action potential.

  • Neuronal pools

    Groups of neurons that integrate incoming information and forward it to other destinations.

  • Neural processing types

    Serial processing: single pathway, predictable response.
    Parallel processing: multiple pathways, simultaneous processing.

  • Neuromodulators

    Chemicals that modify synaptic transmission strength without directly causing EPSPs or IPSPs, e.g., nitric oxide and adenosine.