Mod 5 - Ch 10 Flashcards
what is the endocrine system composed of?
endocrine glands and specialised endocrine cells
- both secrete chemical messengers called hormones
how do hormones get to their target tissues or effectors?
through the bloodstream and at their target tissues, hormones stimulate a specific response
what do chemical messengers (hormones) do?
allow cells to communicate with each other to regulate body activities
what is a gland
an organ consisting of epithelial cells that specialise in secretion, which is the controlled release of chemicals from a cell
autocrine chemical messengers
stimulate the cell that originally secreted it
Example: those secreted by white blood cells during an infection
paracrine chemical messenger
Act locally on neighbouring cells
Example: histamine, released by certain WBC during allergic reactions - histamine stimulates vasodilation in nearby blood vessels
neurotransmitters
secreted by neurons that activate an adjacent cell
- secreted into a synaptic cleft, rather than into the bloodstream
endocrine chemical messengers
secreted into the bloodstream by certain glands and cells to their target cells
functions of the endocrine system
- regulation of metabolism
- controls the rate of nutrient utilisation and energy production - control of food intake and digestion
- regulates the level of satiation (fullness) and the breakdown of food - modulation of tissue development
- influences the development of tissue - regulation of ion levels
- monitors pH, and Na, K, and Ca2+ concentrations in the blood - Control of water balance
- controls solute concentration of the blood and membrane permeability - regulation of cardiovascular functions
- helps regulate the heart rate and blood pressure and prepare body for physical activity - control of blood glucose and other nutrients
- regulates levels of glucose and nutrients in the blood - control of reproductive functions
- controls development and functions - stimulation of uterine contractions and milk release
- modulation of immune system function
- help control the production of immune cells
2 different types of hormone chemical categories
- lipid-soluble hormones
- water-soluble hormones
lipid-soluble hormones
non polar, include steroid hormones, thyroid hormones, and fatty acid hormones
- travel in the bloodstream bound to binding proteins
water-soluble hormones
polar molecules, include protein hormones, peptide hormones, and most amino acid hormones
- dissolve into blood
- delivered to their target w/out attaching to a binding protein (large ones but small ones do attach to binding proteins to avoid being filtered out of the blood)
- short life-span b/c they are rapidly broken down by enzymes w/in the bloodstream
modifications made to hormone molecules that help protect them from being destroyed (3)
- having a carbohydrate attached to them
- having a terminal end protected from protease activity
- having binding proteins. Bound hormones circulate in the plasma longer than free water-soluble hormones do
3 types of stimuli regulate hormone release
- humoral
- neural
- hormonal
humoral stimuli
molecules and ions in the bloodstream can directly stimulate the release of some hormones
- cells that secrete these hormones have receptors for certain substances in the blood
neural stimuli
neuron controls the release of a hormone from a gland, the AP stimulates the release of the neurotransmitter that stimulates the hormone secretion
example: epinephrine and norepinephrine increase heart rate, and increase blood flow through the exercising muscles, when exercising stops the neural stimulation declines and the secretion of these hormones decrease
hormonal stimuli
occurs when a hormone is secreted and stimulates the secretion of other hormones
- tropic hormones stimulate the secretion of another hormone
- neurons in the hypothalamus release stimulatory hormones, called releasing hormones. Releasing hormone travel in the blood to the anterior pituitary gland
- releasing hormones stimulate the release of hormones from the anterior pituitary that travel in the blood to their target endocrine cell
- the target endocrine cell secretes its hormone into the blood, where it travels to its target and produces a response
inhibition of hormone release by humoral stimuli
when a hormones release is sensitive to the presence of a humoral stimulus, there exists a companion hormone whose release is inhibited by the same humoral stimulus
- usually the companion hormone’s effects oppose those of the secreted hormone and counteract the secreted hormones action
Example: if blood pressure goes up aldosterone is secreted but once blood pressure is at good level, ANH is secreted to balance out the aldosterone
inhibition of hormone release by neural stimuli
Neurons inhibit targets just as often as they stimulate targets. If the neurotransmitter is inhibitory, the target endocrine gland does not secrete its hormone
inhibition of hormone release by hormonal stimuli
some hormones prevent the secretion of other hormones, which is a common mode of hormone regulation
Example: hormones from the hypothalamus that prevent the secretion of tropic hormones from the anterior pituitary gland are called inhibiting hormones
two mechanisms to maintain hormone levels in the blood
- negative feedback
- positive feedback
negative feedback for regulation of hormone levels in the blood
self limiting system: hormones secretion is inhibited by the hormone itself once blood levels have reached a certain point and there is adequate hormone to activate the target cell
Example: thyroid hormones inhibit the secretion of their releasing hormone from the hypothalamus and their tropic hormone from the anterior pituitary
Steps:
1. anterior pituitary gland secretes a tropic hormone, which travels in the blood to the target endocrine cell
2. the hormone from the target endocrine cell travels to its target
3. the hormone from the target endocrine cell also has a negative-feedback effect on the anterior pituitary and hypothalamus, which decreases secretion of the tropic hormone
positive feedback for regulation of hormone levels in the blood
self propagating system: some hormones, when stimulated by a tropic hormone, promote the synthesis and secretion of the tropic hormone in addition to stimulating their target cell, in turn this stimulates further secretion of the original hormone
Example: prolonged estrogen stimulation promotes a release of the anterior pituitary hormone responsible for stimulating ovulation
Steps:
1. anterior pituitary gland secretes a tropic hormone, which travels in the blood to the target endocrine cell
2. the hormone from the target endocrine cell travels to its target
3. the hormone from the target endocrine cell also has a positive-feedback effect on the anterior pituitary, which increases the secretion of the tropic hormone
receptors
hormones exert their actions by binding to target cell proteins called receptors
- binds on the receptor site
- specificity: tendency for each type of hormone to bind to one type of receptor
