endocrine system

• The endocrine system allows different parts of our body to communicate with each other.
• The endocrine system consists of a series of glands throughout the body.

  • The glands all secrete hormones.
• Hormones are small chemical molecules that are passed into the blood and then spread throughout the body in the bloodstream.

  • This allows the hormones to come into contact with a wide range of tissues.

  Some of these tissues will have receptors that are specific to the hormone, so the hormone molecules can act as signals to trigger certain changes inside the cells.
• The pituitary gland (sometimes called the 'master' gland) produces multiple different hormones.

  • Some of which:

  Tell the body what to do.

  Tell other glands to release their hormones.
• In the neck, we have the thyroid gland which produces the hormone 'thyroxine'.

  • Thyroxine regulates the rate of our metabolism and plays an important role in growth and development.
• If the pituitary gland detects low levels of thyroxine, it will release 'thyroid stimulating hormone' (TSH).

  • This stimulates the thyroid to release more thyroxine.

  This will bring the level of thyroxine back up to normal.

  • This is called negative feedback.
• Above our kidneys, we have adrenal glands that produce adrenaline.

  • Adrenaline is normally released during a 'fight-or-flight' response when we are startled or scared.

  It prepares us to do things like run, which increases our heart rate and gets our blood pumping faster.
• Just in front of the kidneys, we have the pancreas.

  • The pancreas produces the hormone insulin.

  Insulin helps us to regulate our blood glucose concentrations.

  • The pancreas secretes insulin and glucagon.
• The testes are only found in males - they have two main jobs:

  • Producing the hormone 'testosterone' (puberty).
  • Producing the male gametes 'sperm' for reproduction.
• The endocrine system relies on hormones that are secreted from glands and transported in the bloodstream.

  • Whereas the nervous system relies on electrical impulses which are transferred along nerve cells.
• In the endocrine system hormones spread more slowly and their effects last longer.

  • Whereas, in the nervous system, nerve impulses are sent very fast and the effects do not last very long.
• In the endocrine system, hormones act more generally - they spread through the entire body so they interact with loads of different cells.

  • In contrast, in the nervous system, nerve impulses are sent to one specific area, such as the particular muscle that we need to move our arm.

  This is why we often describe the nervous system as being 'precise'.
• The ovaries are only found in females - their main role is:

  • Producing oestrogen (puberty/menstrual cycle).
  • Holding the female gametes 'egg' cells.