2. Control and Communication

• The brain is composed of several complex parts all working together in order to send and receive info from all around the body.
• The medulla is found at the top of the spinal cord and controls heart rate, breathing and peristalsis.
• The cerebrum is the large part of the brain and is responsible for conscious thoughts, memory and emotion.
• The cerebellum is found at the rear of the brain and controls balance and co-ordinated movement.
• Sensory receptors are found in all parts of the body.
• Sensory receptors often detect sensory stimuli from the environment and produce an electrical signal that is picked up by sensory neutrons and carried to the CNS.
• Neurons are carried to the CNS.
• Information passes along the neurons through electrical impulses.
• There are 3 forms of neurons

  1. Inter neuron
  2. Motor neuron
  3. Sensory neuron
• The sensory neutron carries info from the sensory receptors to the CNS.
• The inter neurons carries info between the sensory neurons and the motor neurons within the CNS.
• Motor neurons carry info from the CNS to the effectors (muscle or glands0
• The reflex arc (SIM)

  Sensory neuron> Inter neuron > Motor Neuron
• Reflex reactions are an involuntary response to a harmful stimulus. This protects the body from harm.
• Reflex responses have to be extremely fast, so they bypass the brain by only travelling through the spinal cord.
• There is a gap between each neuron that the electrical impulse has to cross in order to pass on its message.
• The gap between neurons is called the synapse.
• Information is carried across the synapse by chemicals called neurotransmitters.
• Hormones are chemical messengers that are found in the endocrine system.
• The endocrine system is made up of endocrine glands which release hormones into the bloodstream.
• The hormones travel to their target organs.
• Hormones are carried to all organs through the bloodstream but only affect their target organ.
• Target organs have cells with complementary receptor proteins for specific hormones.
• Homeostasis is the maintenance of constant internal environment.
• Your internal conditions have to be kept at certain levels

  For example

  • Blood glucose levels
  • Temperatures
  • Oxygen levels
  • Salt/ion levels
• Blood glucose regulation is controlled by two hormones, insulin and glucagon.
• If there is an increase in glucose concentration

  1. Increase in glucose concentration
  2. Pancreas release insulin in response
  3. Glucose taken into muscle and liver cells are stored as glycogen
  4. Decrease in glucose concentration
• If there is a decrease in glucose concentration

  1. Decrease in glucose concentration
  2. Pancreas release glucagon in response
  3. Liver cells break down glycogen and release the stored glucose
  4. Increase in glucose concentration
• Low blood sugar? Glucose is gone. I need glucagon!

  To turn glucose into glycogen you need insulin.