9.4 Evaluate Nutritional Strategies to Impact Hematological Wellness

The nervous system is a complex network that controls our body's functions. It's made up of the brain, spinal cord, and nerves, working together to process information and coordinate responses. This system is crucial for everything we do, from breathing to thinking.

Communication in the nervous system happens through electrical and chemical signals. Neurons transmit messages, while neurotransmitters carry information between cells. This intricate system helps maintain balance in our body, responding to changes and keeping us functioning properly.

Overview of the Nervous System

Structure and function of nervous system

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• Complex network of cells and tissues transmits signals throughout the body
  • Composed of brain, spinal cord, and vast network of nerves
• Primary function receives, processes, and transmits information to coordinate and regulate bodily functions
  • Sensory input receives and interprets sensory information from internal and external stimuli (touch, sight, sound)
  • Integration processes and analyzes sensory information in brain and spinal cord
  • Motor output sends signals to muscles, glands, and organs to initiate appropriate responses (muscle contraction, hormone release)
• Nervous system cells
  • Neurons specialized cells transmit electrical and chemical signals
    • Cell body (soma) contains nucleus and organelles
    • Dendrites branched extensions receive signals from other neurons
    • Axon long, thin extension transmits signals to other neurons or effector cells (muscles, glands)
  • Glial cells non-neuronal cells support and protect neurons
    • Astrocytes provide structural support, regulate neurotransmitter levels, and maintain blood-brain barrier
    • Oligodendrocytes (CNS) and Schwann cells (PNS) form myelin sheath around axons for insulation and faster signal transmission
    • Microglia immune cells protect against infection and clear cellular debris

Nervous system communication for homeostasis

• Communication within nervous system occurs through electrical and chemical signaling
  • Electrical signaling involves changes in membrane potential of neurons
    • Resting potential stable, negative membrane potential of neuron when not actively transmitting signals (around -70 mV)
    • Action potential rapid, transient change in membrane potential propagates along axon when threshold reached
  • Chemical signaling involves release of neurotransmitters at synapses between neurons
    • Neurotransmitters chemical messengers released by presynaptic neurons bind to receptors on postsynaptic neurons or effector cells (acetylcholine, dopamine, serotonin)
    • Synaptic transmission process by which neurotransmitters are released, cross synaptic cleft, and bind to receptors, causing excitation or inhibition of postsynaptic cell
• Nervous system maintains homeostasis by constantly monitoring and adjusting bodily functions
  • Feedback loops mechanisms allow nervous system to detect changes in body and initiate corrective actions
    • Negative feedback detects deviations from set point and initiates responses to return system to normal state (thermoregulation, blood pressure control)
    • Positive feedback amplifies change in body to achieve specific outcome (oxytocin release during childbirth)
  • Autonomic nervous system regulates involuntary functions such as heart rate, digestion, and respiration
    • Sympathetic division prepares body for "fight or flight" responses by increasing heart rate, blood pressure, and glucose release
    • Parasympathetic division promotes "rest and digest" functions by slowing heart rate, increasing digestion, and promoting relaxation

Nervous System Adaptability and Protection

• Neuroplasticity: The brain's ability to reorganize and form new neural connections throughout life
  • Allows for learning, memory formation, and recovery from brain injuries
• Neurotransmission: The process of communication between neurons through chemical signals
  • Enables rapid and precise information transfer throughout the nervous system
• Blood-brain barrier: A selective barrier that protects the brain from potentially harmful substances in the bloodstream
  • Regulates the passage of molecules between the blood and the central nervous system

Divisions of the Nervous System

Central vs peripheral nervous systems

• Nervous system divided into two main components: central nervous system (CNS) and peripheral nervous system (PNS)
• Central Nervous System (CNS)
  • Consists of brain and spinal cord
  • Role integrates and processes information, makes decisions, and coordinates bodily functions
  • Brain control center of nervous system
    • Cerebrum responsible for higher cognitive functions, sensory processing, and voluntary movement
    • Cerebellum coordinates balance, posture, and fine motor control
    • Brainstem regulates vital functions such as respiration, heart rate, and consciousness
  • Spinal cord bundle of nerves extends from brainstem and serves as conduit for signals between brain and body
    • Ascending tracts carry sensory information from body to brain
    • Descending tracts carry motor commands from brain to body
    • Spinal reflexes rapid, involuntary responses to stimuli occur without input from brain (knee-jerk reflex)
• Peripheral Nervous System (PNS)
  • Consists of nerves and ganglia outside brain and spinal cord
  • Role connects CNS to rest of body, transmitting sensory information and motor commands
  • Sensory (afferent) division carries sensory information from receptors in body to CNS
    • Somatic sensory detects touch, pressure, temperature, pain, and proprioception
    • Visceral sensory monitors internal organs and glands
  • Motor (efferent) division carries motor commands from CNS to muscles and glands
    • Somatic nervous system controls voluntary movements of skeletal muscles
    • Autonomic nervous system regulates involuntary functions of smooth muscles, cardiac muscle, and glands
      • Sympathetic division
      • Parasympathetic division