Homeostasis and the nervous system

• Living organisms must control the conditions of their internal environment for their cells to function properly, they need to be able to move around and carry out chemical reactions.
• Internal conditions of the body that may change:

  Temperature

  Water levels

  blood pressure

  Blood sugar levels

  Urea concentration

  Insulin levels
• Homeostasis is the maintenance of a constant internal environment despite changes in the external environment.
• Blood sugar levels must be controlled so the cells have enough glucose needed for respiration.
• Water levels in the body must be controlled so the cells don’t gain too little or too much water
• Why must the body be kept at 37 degrees?

  Because enzymes in the body work best a 37 degrees and high temperatures
• Homeostasis involves automatic control systems
• Automatic controls systems involve nervous responses and chemical responses.
• Automatic control systems: Receptors, coordination centres and effectors
• Receptors: cells that can detect changes in an organisms internal or external environment
• Changes that happened in the internal and external environments of our body are called stimuli.
• Coordination centres: receive and process information from the receptors
• Effectors receive information from coordination centres and respond to restore conditions back to optimum
• Effectors can be muscles and glands
• Effectors can be muscles, which respond by contracting to cause movement
• Effectors can also be glands, which respond by releasing hormones
• The brain is the region of the body where information from receptors, situated in various parts of the body, is processed.
• In a simple reflex arc, a relay neurone is connected to a motor neurone which carries the impulse to an effector organ.
• The junction between two neurones is called a synapse. It is a tiny gap between two neurones.
• The nervous system responds to change very rapidly, whereas the hormonal system responds slowly.
• A sensory neurone is connected by a synapse to a relay neurone, and a relay neurone is connected by a synapse to a motor neurone.
• Hormonal responses can last a long time, whereas nervous system responses are short lived.
• A stimulus, such as a bright light, is received by a receptor
• The nervous system:

  • the brain
  • Spinal cord
  • Neurones (nerve cells)
• The brain:

  • coordinates response of effectors
  • part of the CNS
• Spinal cord:

  -coordinates response of effectors
• Neurones:

  • carry electrical impulses (signals) between receptors, the central nervous system (CNS) and effectors.
• • At each junction of the reflex arc, there is a synapse.