Nervous and endocrine systems

• The Central Nervous System is comprised of the Brain and the Spinal cord.
• The Peripheral Nervous System is comprised of the Autonomic nervous system and the Somatic nervous system.
• The PNS relays messages from the environment to the CNS via sensory neurones, then from the CNS to effectors via motor neurones.
• The Autonomic nervous system is responsible for involuntary bodily functions such as heart and breathing rates.
• The Somatic nervous system is responsible for voluntary bodily movements such as contraction of skeletal muscles.
• The Autonomic nervous system is further divided into the sympathetic and parasympathetic nervous systems. These work antagonistically.
• The sympathetic nervous system is responsible for producing the physiological arousal (adrenaline) necessary for fight or flight. It increases heart and breathing rate, inhibits digestion and saliva production.
• The parasympathetic nervous system is involved in production of Noradrenaline to restore the body to its natural state after fight or flight. This decreases heart and breathing rate and resumes digestion.
• How are hormones transported to target cells in the endocrine system?

  Hormones are secreted into the bloodstream and transported to target cells.
• What is the main function of the endocrine system?

  It is the main chemical messenger system of the body.
• Which gland is considered the 'master' gland of the endocrine system?

  The pituitary gland.
• What hormone does the thyroid gland release and what is its effect?

  The thyroid releases thyroxine, which increases heart rate and growth rate.
• What hormone is released by the adrenal gland during the fight or flight response?

  Adrenaline.
• What are the steps involved in the fight or flight response?

  1. Body senses a stressor (e.g., sound of a speeding car).
  2. Information sent to the hypothalamus via sensory receptors and neurons.
  3. Adrenaline released from adrenal medulla and transported to effectors.
  4. Results in physiological changes: rectum contraction, inhibited saliva production, increased breathing rate.
  5. Adaptive purpose: enables escape from stressor to increase survival likelihood.
• What happens once the stressor is no longer a threat?

  The hypothalamus triggers less activity in the sympathetic branch and more in the parasympathetic branch.
• What is the rest and digest response associated with?

  It is associated with the parasympathetic branch of the ANS.
• How does the endocrine system contribute to the fight or flight response?

  It releases hormones like adrenaline that prepare the body for immediate action.
• The pancreas produces insulin and glucagon, which decrease and increase blood glucose levels respectively.
• The testicles produce testosterone, which increases sex drive, sperm production and muscular strength.
• The ovaries produce oestrogen and progesterone. These hormones regulate the development and function of the uterus. Also stimulates egg production.