THE NERVOUS AND ENDOCRINE SYSTEM

• • The Nervous System

  Components: The nervous system consists of the central nervous system (CNS), which includes the brain and the spinal cord, and the peripheral nervous system (PNS).
• • Function:
  • CNS: Processes information and coordinates activity.
  • PNS: Relays messages between the environment and the CNS using sensory neurons, and from the CNS to effectors using motor neurons.
• Subdivisions of the PNS:

  1. Autonomic Nervous System (ANS): Controls involuntary vital functions like heart rate and breathing.
  2. Somatic Nervous System: Receives sensory information and stimulates effectors via motor neurones.
• Subdivisions of the ANS:

  1. Sympathetic Nervous System: Increases heart rate, breathing rate, causes vasoconstriction, and pupil dilation.
  2. Parasympathetic Nervous System: Decreases heart rate, breathing rate, causes vasodilation, and pupil constriction.
• The Endocrine System

  • Function: Acts as the main chemical messenger system, using hormones released into the bloodstream by glands to regulate various bodily functions.
• Key Glands and Hormones:

  1. Pituitary Gland: Known as the 'master' gland, it controls the release of hormones from other glands.
  2. Thyroid Gland: Releases thyroxine, which increases heart rate and promotes growth.
  3. Adrenal Gland: Releases adrenaline, which triggers the fight or flight response by increasing activity in the sympathetic branch of the ANS.
• The Fight or Flight Response

  1. Detection of a Stressor: The body detects a stressor (e.g., a loud noise) through sensory receptors.
• FIGHT OR FLIGHT RESPONSE

  2. Signal Transmission: Information is sent via sensory neurons to the hypothalamus in the brain.
• FIGHT OR FLIGHT RESPONSE

  3. Activation of Sympathetic Branch: The hypothalamus triggers the sympathetic branch of the ANS.
• FIGHT OR FLIGHT RESPONSE

  4. Release of Adrenaline: Adrenaline is released from the adrenal medulla and transported via the bloodstream to target effectors.
• FIGHT OR FLIGHT RESPONSE

  5. Physiological Changes: The body undergoes changes such as increased heart and breathing rates, inhibited saliva production, and contraction of the rectum to sustain the fight or flight response.
• FIGHT OR FLIGHT RESPONSE

  6. Deactivation: Once the stressor is no longer a threat, the hypothalamus reduces sympathetic activity and increases parasympathetic activity, promoting the rest and digest response.
• Summary of Responses

  • Sympathetic Activation:

  1. Heart Rate: Increases
  2. Breathing Rate: Increases
  3. Vasoconstriction: Increases
  4. Pupil Dilation: Increases
  5. Saliva Production: Inhibited
  6. Rectum: Contracts
• summary of responses

  • Parasympathetic Activation:

  1. Heart Rate: Decreases
  2. Breathing Rate: Decreases
  3. Vasodilation: Increases
  4. Pupil Constriction: Increases
  5. Saliva Production: Stimulated
  6. Rectum: Relaxes
• The intricate coordination between the nervous system and the endocrine system ensures that the body can respond effectively to stressors and return to a state of rest once the threat has passed.