Divisions of the nervous system

• The human nervous system consists of neurons that detect information from the environment, process it, and direct the body to take action via muscles and/or glands
• The nervous system is split into the Central Nervous System (CNS) and the Peripheral Nervous System (PNS)
• The CNS consists of the brain (center of conscious and most unconscious processing) and the spinal cord (receives and transmits information)
• The PNS connects the brain and spinal cord to the rest of the body and the external environment
• The PNS is divided into the Somatic Nervous System (SNS) and the Autonomic Nervous System (ANS)
• SNS:

  • Connects the CNS with the senses
  • Composed of sensory nerve pathways bringing information to the CNS from sensory receptors
  • Composed of motor nerve pathways controlling bodily movement by carrying instructions towards muscles
• ANS:

  • Controls bodily arousal, body temperature, homeostasis, heart rate, and blood pressure
  • Composed of the sympathetic and parasympathetic nervous systems
  • Sympathetic ANS prepares the body for fight or flight
  • Parasympathetic ANS returns the body to its normal state after the fight or flight response
• The Endocrine system consists of glands that release hormones into the bloodstream to send messages to other parts of the body
• Hypothalamus is connected to the pituitary gland and regulates the release of hormones
• Pituitary gland is known as the master gland and controls the release of hormones from other glands
• The fight or flight response is a hard-wired response to increase survival chances in life-threatening situations
• Research suggests females may adopt a 'tend and befriend' response in stressful situations
• Modern-day stressors can repeatedly activate the fight or flight response, leading to negative health consequences
• Adrenaline increases blood supply to the brain and muscles, prepares the body for action, and causes increased perspiration
• The endocrine system and the autonomic nervous system (ANS) work together in the fight or flight response
• When a stressor is perceived, the hypothalamus activates the adrenal medulla, which is part of the ANS
• The adrenal medulla secretes the hormone adrenaline, which prepares the body for a fight or flight response
• Adrenaline creates physiological changes in the body:

  • Decreases digestion by constricting blood vessels leading to the digestive system
  • Increases sweating to cool the body
  • Increases pulse and blood pressure
• Adrenaline leads to the arousal of the sympathetic nervous system and reduced activity in the parasympathetic nervous system
• Once the 'threat' is over, the parasympathetic branch takes control and brings the body back into a balanced state