Nervous

Neurons and Their Structure

  • Neurons are the basic cells that transfer information in the nervous system.

  • Structure of Neurons:

    • Cell Body: Contains nucleus and organelles; surrounded by cytoplasm with many branches called dendrites, which receive signals from other neurons.

    • Axon: Long structure that transmits signals away from the cell body; can branch into synaptic terminals that connect to other neurons at synapses.

Organization of the Nervous System

  • Neurons are organized into nerves and larger systems for efficient information processing.

  • Nervous System Components:

    • Central Nervous System (CNS): Composed of the brain and spinal cord.

    • Peripheral Nervous System (PNS): Includes sensory receptors, motor systems, and autonomic nervous system.

Processing and Interpretation of Information

  • The nervous system processes and interprets information through organized networks of neurons, primarily in the brain.

  • Information Processing Steps:

    • Sensory Input: Sensory neurons gather information from the external environment or internal body conditions.

    • Integration: Interneurons connect and interpret the sensory input within the CNS.

    • Motor Output: Motor neurons trigger responses in muscles, organs, and glands.

Electrical Impulse Transmission in Neurons

  • Neurons communicate through electrical impulses that are generated by changes in membrane potential.

  • Resting Membrane Potential vs. Action Potential:

    • Resting Membrane Potential: The stable voltage difference across the neuron membrane when not transmitting signals.

    • Action Potential: Rapid change in membrane potential that occurs when a neuron sends a signal.

Mechanism of Impulse Transmission

  • Neurons receive, transmit, and send impulses using ion channels and neurotransmitters.

  • Ion Channels: Located in the neuron membrane, they allow the movement of ions (like Na+ and K+) in and out of the cell, generating electrical signals.

    • Gated Ion Channels: Open or close in response to stimuli, which can either depolarize (increase positivity) or hyperpolarize (increase negativity) the membrane potential.

Neurotransmitters

  • Chemical signaling molecules that transmit signals between neurons via synapses.

  • Different types of neurotransmitters include:

    • Glutamate: Involved in long-term memory formation.

    • Dopamine and Serotonin (amines): Affect mood, attention, and learning; specifically relevant to conditions like Parkinson’s disease.

    • Endorphins (peptides): Modulate pain perception and have effects on respiration and urine output.

Specialized Functions in the Nervous System

  • Glial Cells: Support neurons by providing nourishment, insulation, and regulation of extracellular fluid around neurons.

  • Reflex Actions: Spinal cord can produce involuntary responses to stimuli without involving the brain.

Peripheral Nervous System Components

  • Motor System: Controls voluntary and involuntary muscle movements.

  • Autonomic Nervous System: Regulates involuntary functions of smooth muscles, cardiac muscles, and glands in the body.

  • Sympathetic and Parasympathetic Systems:

    • Sympathetic: Prepares body for fight-or-flight response.

    • Parasympathetic: Promotes rest and maintenance of bodily functions.