the endocrine system

• The endocrine system - one of the body’s major information systems that instructs glands to release hormones directly into the bloodstream. These hormones are carried towards target organs in the body
• Gland - an organ in the body that synthesises substances such as hormones
• Hormone - chemical substances that are secreted into the bloodstream and only affect target organs
• Hormones are produced in large quantities but disappear quickly. Their effects are very powerful/long lasting
• The endocrine system acts much more slowly than the central nervous system but has very widespread and powerful effects
• The pituitary gland is sometimes known as the master gland because the hormones released, control and stimulate the release of hormones from other glands in the endocrine system
• the pituitary gland is divided into the anterior (front) and posterior (back) lobes which release different hormones
• Oxytocin (often referred to as the love hormone) is released from the posterior lobe of the pituitary gland. It’s responsible for uterus contractions during birth
• Adrenocortical trophic hormone (ACTH) is released from the anterior lobe of the pituitary gland and stimulates the adrenal cortex and the release of cortisol during the stress response
• Melatonin is the main hormone released from the pineal gland, which is responsible for important biological rhythms, including the sleep-wake cycle
• The thyroid gland releases thyroxine which is responsible for regulating metabolism
• The adrenal gland is separated into two parts, the adrenal medulla and the adrenal cortex
• The adrenal medulla is responsible for releasing adrenaline and noradrenaline, which are involved in the fight or flight response
• The adrenal cortex releases cortisol, which stimulates the release of glucose to provide the body with energy while suppressing the immune system
• In males, the testes release androgens, which include the hormone testosterone
• testosterone is responsible for the development of male sex characteristics during puberty and promoting muscle growth
• In females, the ovaries release oestrogen which controls the regulation of the female reproductive system, including the menstrual cycle and pregnancy
• the fight or flight response is a physiological response to a threat that is triggered by the sympathetic nervous system
• outline the fight or flight response: Adrenaline is released from adrenal glands. This triggers the autonomic system so it switches from parasympathetic to sympathetic responses. This creates the physiological arousal necessary for the fight or flight response which occurs when a stressor is perceived
• Characteristics of the fight or flight response are increased heart rate so more blood is directed to the muscles, transporting oxygen and dilated pupils.
• thyroxine affects cells in the heart to increase heart rate and also in the body to increase metabolic rates. This in turn affects growth rates