Endocrine System

• Works alongside nervous system to control vital functions in the body through action of hormones. Works slower than nervous system (seconds rather than milliseconds), but widespread and powerful effects.
• Glands are organs that produce hormones. Key endocrine gland is the pituitary gland, located in the brain. Called 'master gland' because it controls the release of hormones from all other glands.
• Hormones are secreted in bloodstream and affect any cell that has a receptor for that hormone. For ex, thyroxine affects cells in the heart and also cells throughout the body which increase metabolism.
• Endocrine system and nervous system work together, for ex flight/fight response. Often endocrine system and ANS work parallel, for ex during a stressful event:

  -Stressor perceived by hypothalamus, activates pituitary.

  -Sympathetic nervous system aroused.

  -Adrenaline released from adrenal medulla into bloodstream. Delivers aroused state, causing changes in body, e.g increased heart rate, dilation of pupils, decreased saliva. Fight/flight response.

  -Immediate and automatic.

  -Parasympathetic nervous system takes over after threat passed. Returns body to resting state. Acts as a 'brake'.
• Sympathetic state: Parasympathetic state:

  -Increases heart rate -Decreases heart rate

  -Increases breathing rate -Decreases breathing rate

  -Dilates pupils -Constricts pupils

  -Inhibits digestion -Stimulates digestion

  -Inhibits saliva production -Stimulates saliva production

  -Contracts rectum -Relaxes rectum