The endocrine system

• The endocrine system works alongside the nervous system to control vital functions in the body through the action of hormones.
• The endocrine system works much more slowly than the nervous system but has widespread and powerful effects.
• Glands are organs in the body that produce hormones.
• The major endocrine gland is the pituitary gland, located in the brain. it is called the 'master gland' because it controls the release of hormones from all the other endocrine glands in the body.
• Hormones are secreted in the bloodstream and affect any cell in the body that has a receptor for that particular hormone.
• Thyroxine, produced by the thyroid gland affects cells in the heart and also cells throughout the body which increase metabolic rates. This in turn affects growth rates.
• give one example of when the endocrine system and the ANS work together

  the fight or flight system.
• what happens when a stressor is perceived

  the hypothalamus triggers activity in the sympathetic branch of the ANS. the ANS changes from its normal resting state (the parasympathetic state) to the physiologically aroused sympathetic state. the stress hormone adrenaline is released from the adrenal medulla into the bloodstream.
• what does adrenaline trigger?

  physiological changes in target organs in the body and causes, e.g. increased heart rate, dilation of the pupils, decreased production of saliva. this is called the fight or flight response.
• what happens once the threat has passed?

  the parasympathetic nervous system returns the body to its resting state. this acts as a 'brake' and reduces the activities of the body that were increased by the actions of the sympathetic branch (sometimes referred to as the 'rest and digest' response).