The nervous system and the endocrine system

• Effectors are muscles and glands.
• The somatic nervous system connects the central nervous system and the senses.
• The endocrine system secretes hormones into the bloodstream which are required to regulate many bodily functions such as metabolism, growth or reproduction.
• The fight-or-flight response is triggered by a perceived threat or stressful situation e.g. a car approaching suddenly. It causes adrenaline to be released which causes physiological changes like increased heart rate.
• The parasympathetic nervous system is responsible for the 'rest and digest' response. It restores normal physiological processes when the threat has passed such as slowing down breathing and heart rate.
• A perceived stress/threat activates the sympathomedullary pathway, leading to the release of adrenaline. This leads to an increase in heart rate and breathing rate. Also, the digestive system is "shut-down" as blood flow to the digestive organs is redirected to the muscles.
• Adrenaline is released from the adrenal medulla in response to activation of the sympathomedullary pathway. It prepares the body for action - a fight-or-flight response.
• Adrenaline causes physiological changes in the body such as:

  • increase heart and breathing rate
  • increase the rate of blood flow and raise blood pressure
  • directs blood flow away from the digestive system, kidneys and the skin
  • increase blood supply to skeletal muscle for physical action
  • increases respiration
• The nervous system is divided into the central and peripheral nervous systems.
• The Central nervous system (CNS) comprises the brain and spinal cord.
• The peripheral nervous system is further divided into the somatic nervous system and the autonomic nervous system (ANS).
• The somatic nervous system consists of sensory and motor neurons to carry sensory and motor information to and from the central nervous system (CNS) and also enables reflex actions.
• The autonomic nervous system (ANS) acts largely unconsciously/involuntarily. It is divided into the sympathetic nervous system (SNS) and the parasympathetic nervous system (PNS).
• The sympathetic nervous system (SNS) prepares us for fight-or-flight response, which is activated during stressful or threatening situations.

  • It increases heart rate, dilates pupils and inhibits non-essential processes like digestion.
• Give two differences between the autonomic nervous system and the somatic nervous system (2)

  • the autonomic nervous system is involuntary whereas the somatic nervous system is under conscious control.
  • ANS controls smooth muscles and glands whereas the SNS controls skeletal muscles.
• Identify two components of the peripheral nervous system, and explain two differences in their organisation and/or functions (4)

  • the SNS has sensory and motor pathways, while the ANS is purely motor
  • the ANS controls internal organs and glands of the body while the SNS controls skeletal muscle, movement etc
• Briefly explain one function of the endocrine system (2)

  • To secrete the hormones which are required to regulate many bodily functions.
  • To provide a chemical system of communication via the bloodstream.
• The endocrine system helps to regulate the activity of cells and organs in the body.
• The thyroid gland produces thyroxine, which increases heart rate and metabolic rates.
• The pineal gland produces melatonin, which may help regulate the wake-sleep cycle.
• The anterior pituitary gland secretes Luteinizing hormone (LH) & Follicle-stimulating hormone (FSH), which stimulate ovaries to produce oestrogen & progesterone.
• The anterior pituitary gland secretes LH & FSH, which stimulate the testes to produce testosterone & sperm.
• The pancreas secretes insulin and glucagon, which help regulate blood sugar levels.
• The adrenal cortex releases cortisol, a hormone involved in the stress response. Cortisol helps regulate metabolism, blood pressure and immune responses during stress.

  • It provides the body with energy by increasing glucose availability.
• The hypothalamus connects the endocrine system and the nervous system.
• The pituitary gland is known as the 'master gland', it releases hormones that influence other glands.

  • for example, it releases ACTH to stimulate the adrenal glands.