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Body Responses to Stress

  • Calming Response:
    • After initial stress (like seeing a threat), the body performs calming actions (e.g., go to the restrooms).
Physiological Changes in Stress Response

  • Increased Heart Rate:

    • Direct correlation with blood pressure.
    • As heart rate increases, blood pressure rises.

  • Respiration Changes:

    • Speeds up (increased rate of respiration).

  • Airway Changes:

    • Airways dilate to allow more oxygen intake, termed bronchodilation.
    • Increased oxygen is necessary for muscles during stress responses (e.g., escaping predators).

  • Blood Glucose Levels:

    • Increase in blood glucose for energy supply to muscles.
Role of Epinephrine (Adrenaline)
  • Adrenaline Rush:
    • Results in heightened response capabilities (e.g., running faster than usual).
    • Intensifies body’s response to stress.
Return to Homeostasis
  • Parasympathetic Division:
    • Also known as the “rest and digest” system.
    • Brings body back to its normal resting state (restoration of digestive functions, urinary functions).
    • Distinction: Does not simply reverse sympathetic actions—returns body to baseline (e.g., heart rate return to 70 bpm from 120 bpm).

Neuron Functions in the Nervous System

  • Types of Neurons:
    • Sensory Neurons: Carry information from peripheral body (external/internal sensory input) to central nervous system (CNS).
    • Motor Neurons: Transmit commands from CNS to effectors (muscles & glands).
    • Interneurons: Neurons that communicate within the CNS; process information received from sensory inputs and trigger motor responses.
Functional Divisions of the Nervous System

  • Afferent:

    • Direction: Towards the CNS; related to sensory functions.

  • Efferent:

    • Direction: Away from the CNS; related to motor commands.
Receptor Types
  • Exteroceptors: Detect external environmental stimuli (e.g. touch, temperature, pain).
  • Proprioceptors: Detect body position and movement.
  • Interoceptors: Monitor internal body environment (e.g., blood glucose levels).

Levels of Control: Afferent vs Efferent

  • Somatic Sensory: Afferent pathway related to external stimuli.
  • Visceral Sensory: Related to internal organ signals, predominantly via interoceptors.
  • Somatic Motor: Efferent pathway, commanding skeletal muscles.
  • Visceral Motor: Commands internal organs; part of autonomic nervous system.

Nervous System Structural Considerations

Anatomy of Neurons
  • Unipolar Neurons: Often found in sensory pathways with cell bodies positioned outside the CNS.
  • Ganglia: Groups of cell bodies found in the peripheral nervous system (PNS).
  • Nuclei: Groups of cell bodies found in the CNS.
Glial Cells in Nervous System
  • Epidermal Cells: Line the central canal of the spinal cord; involved in CSF production.
  • Astrocytes: Provide structural support, maintain blood-brain barrier, regulate nutrient levels, and form scar tissue in the CNS.
  • Oligodendrocytes: Produce myelin sheaths in the CNS to increase action potential conduction speed.
  • Microglia: Immune defense within the CNS, ingesting waste and pathogens.
Peripheral Nervous System Glial Cells
  • Satellite Cells: Support and regulate the environment around PNS neurons.
  • Schwann Cells: Produce myelin sheaths around axons in PNS; facilitate nerve regeneration.