gland and hormone

• A gland is an organ that releases or secretes a substance. This means that cells in the gland make a chemical which leaves the cells through the cell membrane. The chemical then travels somewhere else in the body where it carries out its function.
• two types of gland:

  1. endocrine gland 

  2. exocrine glands
• exocrine glands secrete their products through a tube called duct. for example salivary glands in your mouth secrete saliva down salivary ducts , and tear glands secrete tears through ducts that lead to the surface of the eye
• Endocrine glands have no duct, and so are called ductless glands. instead their products,the hormones are secreted into the blood vessels that pass through the gland
• hormones only affect particular tissues or organs if the cells of that tissue or organ have special chemical receptors for the particular hormone. For example, the insulin hormone affects the cells of the liver which have insulin receptors.
• endocrine system: 

  • works by hormone transmitted into the bloodstream
  • hormones travel more slowly and generally take longer to act
  • response is usually long lasting
  • hormones can have widespread effect on different organs (although they only act on particular tissue/organ with the correct receptors)
  •  works by chemical signals 
  • control growth, development and digestion
  • organs are physically connected
• Nervous system:

  • works with chemical and electrical signals
  • control thought movement and emotion
  • impulses can travel very fast and usually have an instant effect
  • response are usually short lived
  • organs are not physically connected
  • impulses act on individual cells such as muscle fibers and have a very localized effect
  • works by impulses transmitted into nerve cells (although chemicals are used in the synapses)
• pituitary gland : stimulate the development of male and female sex organ and stimulate the skeletal growth

  • hormone: 

  follicle stimulating hormone: stimulate the egg development in female and sperm production in male

  Luteinising hormone : stimulate the egg release (ovulation) in female and testosterone production in male

  antidiuretic hormone: controls the water content in blood
• hypothalamus: regulates the activity of other gland and produces hormone that control hunger, heart rate and body temperature
• thyroid: regulate the level of phosphorus and calcium in blood and increase/control the metabolic rate (how fast chemical reaction take place in cells)
• parathyroid: maintain the level of phosphorus and calcium in blood
• pancreas: lowers the blood sugar level by producing a hormone called insulin that stimulates the liver cells to take up the glucose and enter the liver to convert it and store it as glycogen.

  raises the blood sugar level by stimulating the liver to produce more glucose to the blood (glucagon)
• adrenal: increase heart and breathing rate, raises blood pressure to prepare our body for physical activity
• testes: control the development of male secondary sexual characteristic (testosterone)
• ovary: control the development of female secondary sexual characteristic (estrogen) and regulate the menstrual cycle (progesterone)
• when our body is preparing for physical action, the muscle needs a good supply of oxygen and glucose for respiration. in order to that:

  1. the breathing rate increases and breath becomes more deeper taking more oxygen into the body
  2. the heart beats faster, sending more blood to the muscles, so they receive more glucose and oxygen for respiration
  3. blood is diverted away from the intestine to the muscles
• how the adrenaline prepare our body for physical activity:when our body is preparing for physical action, the muscle needs a good supply of oxygen and glucose for respiration. in order to that:

  1. In the liver, stored carbohydrate (glycogen) is converted into glucose and released into the blood. The muscle cells absorb more glucose and use it for respiration 
  2. the pupil dilate, increasing visual sensitivity to movement 
  3. body hair stands upright, making the animal look larger to the enemy
  4. mental awareness is increased, so reactions are faster
• after we had a meal or after the adrenaline raises the blood sugar level, the blood sugar level increases. After we had a meal, the sugars from the carbohydrate pass into the blood and insulin is produced to stimulate the liver cells to take up the glucose to the liver through the hepatic portal vein. And in the liver, the glucose is converted and stored as a long subunit of glucose called glycogen. The blood leaving the liver has a lower concentration of glucose then when it enters the liver by this, the blood sugar level will be kept constant.