Control and communication

• The Nervous System consists of the Central Nervous Sytstem (CNS) and other nerves. The CNS consists of the brain and the spinal cord
• Cerebrum controls conscious thoughts , memory and imagination

  Medulla controls the rate o breathing and the heartbeat

  Cerebellum controls balance and movement

  
• Nerves are made of nerve cells called neurons

  Neurons carry signals by electrical impulses.

  There are three types of neurons

  • Sensory- passes information from the sense to the CNS
  • Inter- located in the CNS and processes the information from the senses that require the response
  • Motor- enable the response to the effector ( muscle or gland)

  
• Gaps between neurons are called synapses

  The electrical impulse is unable to cross these gaps. The signal is transferred across the synapse by chemicals

  
• Stimuli is a change in the environment that causes a response in the body. The Nervous System allows the body to detect this stimuli.

  There are two main types of responses within our body

  1. Voluntary- we control how our body reacts
  2. Involuntary- our body reacts automatically without us thinking about it
• Voluntary response

  1. receptors in our sense organs detect changes in the environment- stimuli
  2. an electrical impulse is sent to the CNS by the sensory neuron
  3. information arrives at the CNS and information is processed by the inter neuron
  4. if the body need to perform a physical activity the CNS sends a message to the muscles or gland by the motor neuron
  5. the motor neuron then sends the signal to the effector which carries out a response
• Involuntary response or a reflex action is rapid to protect the body from harm

  
• The endocrine glands release hormone into the bloodstream.

  Hormone are chemical messengers that transfer information from one part of the body to another. Target tissues have receptors which are complementary to hormones
• Insulin is a hormone that is produced by the pancreas and is responsible for regulating blood glucose levels.

  Glucagon is a hormone that is produced in the pancreas and it increases the blood glucose levels
• An increases of blood glucose leads to the following action

  1. the pancreas responds by releasing insulin to the bloodstream
  2. receptors in the liver detect the insulin
  3. in response, the liver converts the excess glucose into glycogen
  4. the blood glucose levels fall and regulate to back to normal
• A decrease of blood glucose leads to the following action

  1. the pancreas responds by releasing glucagon
  2. receptors in the liver detect the glucagon
  3. in response, the stored glycogen is converted back into glucose
  4. the blood glucose levels rise and regulate back to normal