Nervous System and Neural Communication

Essential Question of Human Behavior

  • Question: To what extent is human behavior a result of electrical signals between neurons versus chemical messages from the endocrine system?

Overview of the Nervous System

  • Definition: The nervous system is a network of billions of cells in your brain and your body.
  • Functions of the Nervous System:
    1. Receives sensory information - Achieved through sensory neurons.
    2. Processes sensory information - Conducted by motor neurons.
    3. Responds to information - Involves muscle response based on processed information.

Divisions of the Nervous System

  • Central Nervous System (CNS):
    • Composed of nerve cells in the brain and spinal cord.
    • Purpose: Organizes and evaluates information.
  • Peripheral Nervous System (PNS):
    • Composed of nerve cells outside of the brain and spinal cord.
    • Purpose: Intercepts signals from the CNS.
    • Collaboration: The CNS and PNS work together to facilitate communication throughout the body.

Basic Units of the Nervous System

  • Nerve Cells/Neurons:
    • Function: Allow you to think and act.

Structure of Neurons

  • Four Parts of a Neuron:
    1. Dendrites:
      • Characteristics: Short, branchlike structures.
      • Function: Receive signals from other neurons.
    2. Cell Body:
      • Function: Collects information and sends signals to the axon.
    3. Axon:
      • Function: Carries information between the brain and other locations in the body.
    4. Terminal Buttons:
      • Function: Release chemical signals from neurons into the synapse.

Synaptic Communication

  • Synapse:
    • Communication occurs between neurons at this junction.
    • Chemical Messages: Neurotransmitters cross the tiny gap and bind to dendrites of receiving neurons.

Phases of Neural Communication

  • Three Phases of Neural Communication:
    1. Transmission Phase:
      • Process: Electrical signals travel along the axon; neurotransmitters are released into the synapse.
    2. Reception Phase:
      • Process: Dendrites receive the signals sent by neurotransmitters.
    3. Integration Phase:
      • Process: Neurons access and integrate the information received.

Membrane Properties of Neurons

  • Neuron Membrane:
    • Definition: A semipermeable barrier that separates the inside of a neuron from the outside environment.
    • Function: Allows some substances to move through while controlling ion movement.

Action Potential and Resting State

  • Action Potential:
    • Description: Neurons receive stimulating signals from other neurons; the inside of the neurons becomes positively charged.
    • Process: When sufficiently stimulated, it triggers action potential.
  • Refractory Period:
    • Description: The time during which a neuron returns to its resting state after firing an action potential.

Role of Myelin Sheath

  • Function of Myelin Sheath:
    • Insulates some axons to allow faster movement of electrical signals along the axon.

Multiple Sclerosis (MS)

  • Effects of MS on Neural Communication:
    • Slows down or stops communication between neurons due to deterioration of myelin sheath.
  • Symptoms of MS:
    • Loss of senses, numbness, tingling, balance issues, and more.

Phases of Neurotransmission

  • Transmission Phase:
    • Action potential prompts the release of neurotransmitters.
  • Reception Phase:
    • Neurotransmitters travel across the synapse and bind to receiving neurons.
  • Integration Phase:
    • Postsynaptic neuron processes incoming signals.
  • Excitatory vs. Inhibitory Signals:
    • Excitatory: Signals excite the neuron, increasing the likelihood of action potential.
    • Inhibitory: Signals decrease the likelihood of an action potential.
  • Lock and Key Analogy:
    • Each receptor is like a lock that can only be influenced by a specific type of neurotransmitter (the key).

Neurotransmitter Functions

NeurotransmitterFunctionExample in Action
AcetylcholineControls muscles, attention, memory, learning, and sleepMuscle contraction
NorepinephrineArousal and alertnessNoticing what’s happening around you
SerotoninEmotional state, impulse control, dreaming, food cravingsRegulating mood and appetite
DopamineReward and motivationEating when hungry
GABA and GlutamateInhibition of action potentials, anxiety reductionLearning and memory (e.g., Xanax for anxiety, glutamate for school learning)
EndorphinsPain reductionNot realizing pain immediately after an injury

Peripheral Nervous System Subdivisions

  • Somatic Nervous System:
    • Function: Voluntary control of skeletal muscles.
  • Autonomic Nervous System:
    • Function: Involuntary control of organs, glands, and cardiac muscles.

Autonomic Nervous System Subdivisions

  • Sympathetic Nervous System:
    • Function: Initiates the fight or flight response, preparing the body for stress.
  • Parasympathetic Nervous System:
    • Function: Conserves energy and restores the body after stress.

Real-World Application of Autonomic Response

  • Example Situation: Near car crash.
    • Response: The body triggers a flight or fight response, increasing heart rate and adrenaline levels, indicating sympathetic nervous system activation.

Endocrine System Overview

  • Definition: A communication network that influences many body functions, mental activity, and behavior.
  • Function: Works alongside the nervous system to regulate psychological activity through the release of hormones from endocrine glands.
  • Hormones:
    • Definition: Chemicals released into the bloodstream by endocrine glands.
  • Travel Mechanism: Hormones travel throughout the body via the bloodstream from their point of release.