The Endocrine System Flashcards
what is the endocrine system?
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a network of glands throughout the body that manufactures and secretes chemical messengers known as hormones
works closely with the nervous system to control the body’s physiological processes
uses blood cells to deliver hormones to target sites in the body
key features of the endocrine system
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endocrine glands
hormones
pituitary gland
adrenal gland
reproductive organs (testes and ovaries)
endocrine glands
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endocrine glands are special groups of cells that produce and secrete hormones, which are chemical substances that regulate the activity of cells and organs in the body
3 major endocrine glands; pituitary gland, adrenal glands and reproductive organs
each gland secretes different hormones which regulates the activity of various organs and tissues in the body
regulated by feedback
EXAMPLE = the hypothalamus sends a signal to the pituitary gland in the form of a releasing hormone, this causes the pituitary gland to secrete a stimulating hormone in the bloodstream, which signals to the target gland to secrete its hormone
as levels of this hormone rises, the hypothalamus shuts down secretion of the releasing hormone and the pituitary gland shuts down secretion of the stimulating hormone, this slows down the secretion of the target gland’s hormone and results in a stable concentration of hormones in the bloodstream
hormones
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chemicals messengers that travel through the bloodstream and regulate the activity of cells and organs in the body, thus influencing many processes such as mood and the stress response
they are carried to target sites via the bloodstream
stimulate a particular part of the body
come into contact with most cells in the body but each hormone usually only affects a limit number of cells called target cells
target cells respond to a particular hormone because they have receptors for that hormone, meaning that cells that do not have that specific receptor are not directly influenced by that hormone
when enough receptor sites are stimulated by hormones, a physiological reaction occurs in the target cell
the levels of hormones released and the timing of hormone release is critical for normal functioning — too much or too little at the wrong time can result in dysfunction of bodily systems (for example, too much cortisol can lead to Cushing’s syndrome which involves high blood pressure and depression)
pituitary gland
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known as the master gland
produces hormones that influence the release of hormones from other glands and regulates many of the body’s functions
controlled by the hypothalamus, a region of the brain located above the pituitary gland which receives information from many sources about the basic functions of the body and uses this information to help regulate the functions by controlling the pituitary gland
hormones produced by the pituitary gland travel in the bloodstream to specific target sites and either directly cause changes in physiological processes or stimulate other glands to produce other hormones
high levels of hormones produced by other glands can stop the hypothalamus and pituitary gland releasing more of their own hormones — this is known as negative feedback and prevents hormone levels rising too high
hormones produced by the pituitary gland
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the pituitary gland has 2 main parts — the anterior pituitary and the posterior pituitary
each of which releases different hormones that target different parts of the body and affect different glands or cells
the anterior pituitary releases ACTH (adrenocorticotrophic hormone) as a response to stress, ACTH stimulates the adrenal glands to produce cortisol
the anterior pituitary also produces hormones important in the control of reproductive functioning and sexual characteristics —such as the luteinising hormone (LH) and follicle stimulating hormone (FSH) which stimulates the ovaries to produce oestrogen and progesterone and stimulates the testes to produce testosterone and sperm
the posterior pituitary releases oxytocin which stimulates the contraction of the uterus during childbirth and is important for mother infant bonding
recent research using mice hasfound that oxytocin is indispensable for healthy maintenance and repair, but it also declines with age
adrenal glands
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the two adrenal glands are on top of the kidneys
each gland is made up of 2 distinct parts — the outer part is called the adrenal cortex and the inner region is called the adrenal medulla
the cortex and medulla have very different functions — for example, the hormones released by the cortex are necessary for life whereas the hormones released by the medulla are not
hormones produced by the adrenal glands
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the adrenal cortex produces cortisol which regulates and supports numerous important bodily functions including cardiovascular and anti-inflammatory functions
cortisol production increases in response to stress because if cortisol levels are too low then the individual has low blood pressure, poor immune function and an inability to deal with stress
the adrenal cortex also produces aldosterone which is responsible for maintaining blood volume and blood pressure
the adrenal medulla releases adrenaline and noradrenaline which prepares the body for fight or flight
adrenaline helps the body respond to stressful situations by increasing heart rate and blood flow to get more oxygen to the muscles and brain, it also helps with the conversion of glycogen to glucose to provide energy
noradrenaline constricts the blood vessels which causes blood pressure to increase
reproductive organs: ovaries
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the 2 ovaries are part of the female reproductive system
they are responsible for the production of eggs as well as the hormones oestrogen and progesterone
progesterone is particularly important in the post ovulation phase of the menstrual cycle and has been found to be associated with heightened sensitivity to social cues that indicate social opportunity as well as threat (important for pregnancy)
progesterone also prepares the womb for pregnancy
reproductive organs: testes
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testes are male reproductive glands that produce the hormone testosterone
testosterone causes the development of male characteristics such as facial hair, a deep voice and growth spurts that take place during puberty
it also plays a role in sex drive and sperm production
the production of testosterone is controlled by the hypothalamus and pituitary gland — the hypothalamus instructs the pituitary gland in how much testosterone to produce and the pituitary gland passes this message to the testes
not exclusively a male hormone, women have it too but in smaller amounts
