[Chapter 32] Endocrine Control Flashcards
Animal hormones
Cell products secreted from endocrine glands, endocrine cells, and a few neurons. In most cases, bloodstream circulates hormones to target cells
Neurotransmitters
Secreted by neurons into the tiny synaptic cleft between a neuron and a target cell
Local signaling molecules
Secreted by many cell types into extracellular fluid and broken down quickly; molecules only persist long enough to affect nearby tissues
Pheromones
Signals that diffuse through water or air to target cells in other individuals of the same species. Help integrate social behaviour (ex: female moth releases sex pheromone and attracts mate) Many vertabraes have vomeronasal organ in nose that responds to pheromones
When was the word hormone first used, what is its origin, and who coined it?
Early 1900s by physiologists W Bayliss and E Starling, from Greek word ‘hormon’, meaning ‘to set in motion’
List the sources vertebrate hormones are (generally) secreted from
pituitary gland adrenal gland (2) pancreatic islets (numerous cell clusters) thyroid gland parathyroid gland (4 in humans) pineal gland thymus gland gonads (2) endocrine cells of the hypothalamus, stomach, small intestine, liver, kidneys, heart, placenta, skin, adipose tissue, and other organs
Endocrine system
All sources of hormones in the animal body, linked structurally and functionally with the nervous system in intercellular communication
How is the nervous system and the endocrine system linked?
Share a few structures, issue a few of the same signals, most organs accept and respond to signals from both.
In all animals, signaling molecules do what?
Integrate cell activities. each tupe of signal acts on all cells that have receptors for it. targeted cells may alter their activities in response.
Hypothalamus (part of the brain)
Produces, secretes six releasing and inhibiting hormones (act on different endocrine cells in anterior lobe of pituitary)
Produces ADH (conserves water) and oxytocin (roles in childbirth, milk secretion).
Pituitary gland, anterior lobe
ACTH, TSH, FSH, and LH (stimulate the secretion of other hormones), prolactine (affects mammary gland development), growth hormone (affects overall growth)
Pituitary gland, posterior lobe
Stores, secretes two hypothalamic hormones: ADH and oxytocin
Adrenal gland (one pair) Cortex
Cortisol (affects glucose metabolism) and aldosterone (conserves sodium)
Adrenal gland (one pair) Medulla
Epinephrine and norepinephrine (these hormones interact, in conert with the supathetic nervous system, to help adjust organ activities, especially during times of excitment or stress)
Ovaries (one pair of female gonads)
Estrogens and progesterone (maintain primary sex organs, influence secondary sexual traits)
Testes (one pair of male gonads)
Testosterone (develops and maintains primary sex organs, influences secondary sexual traits)
Pineal gland
Melatonin (affects biological clocks, overall level of activity, reproductive cycles)
Thyroid gland
Thyroid hormone (affects growth and development, metabolism), calcitonin (lowers blood level of calcium)
Parathyroid glands (four)
Parathyroid hormone (increases blood level of calcium)
Thymus gland
Thymosins (roles in white blood cell functioning)
Pancreatic islets
Insulin (lowers blood level of glucouse), glucagon (raises blood level of glucose)
Hormones induce changes in service of programs of…
Growth, maintenance, and reproduction
Three steps of cell communication
Signal Reception (signal activates target cell receptor), signal transduction (transduced to a molecular form that acts in the receiving cell), cellular response (cell may make a functional response)
What do enzymes do?
Make hormones from a variety of sources
Steroid hormones are derived from?
Cholesterol
ex: testosterone and other androgens, estrogens, progesterone, aldosterone, cortisol
Amine hormones are?
Modified amino acids
ex: melatonin, epinephrine, thyroid hormone
Peptide hormones are?
Short chains of amino acids
ex: glucagon, oxytocin, antidiuretic hormone, calcitonin, parathyoid hormone
Protein hormones are?
Longer chains of amino acids
ex: growth hormone, insulin, prolactin, follicle-stimulating hormone, luteinizing hormone
Signal response requires?
Functional receptors
Second messenger
A molecule that is formed in response to an external signal and causes more cellular changes
What kind of things influence hormone action?
Type/state of target receptors, interventions by other hormones, feedback mechanisms, environmental cues, etc
More specifically…
1. Cells need the right receptors for specific hormones
2. Different hormones often interact. Binding of one hormone may block, enhance, or have no effect on the cell’s response to other hormones
3. Concentration of particular hormone in tissue. More hormone molecules in the interstitial fluid around target cell, more likely to bind with receptors
4. Target cell’s metabolic and nutritional state
5. Specific environmental cues like temperature, day length, etc
How do hormone molecules interact with receptors on/in target cells?
they reversibly bind
How do steroid and thyroid hormones bind to change gene expression?
With receptors insider the cell
How do steroid and thyroid hormones bind without changing gene expression?
With receptors at the cell surface, triggers fast responses
How do peptide and protein hormones bind?
to membrane receptors. often, second messenger in cytoplasm relays signal to cell’s interior
Hypothalamus
Forebrain region, has neurons that secrete hormones
Pituitary gland
Attached by a stalk of tissue to the hypothalamus. in humans, no bigger than a pea.
Posterior lobe of pituitary gland
stores and secretes hormones from hypothalamus
Anterior lobe of pituitary gland
Makes own hormones, signals from hypothalamus control their release
How do the hypothalamus and the pituitary gland work together?
Interacts as a master control center, integrating much of the activity of the endocrine and nervous systems
Releasers
Call for the secretion of hormones by target cells
Inhibiters
discourage target cell secretions
ACTH
stimulates the release of cortisol from a pair of adrenal glands
TSH
stimulates the release of thyroid hormones from the thyroid gland
FSH and LH
affect gamete formation in the reproductive organs and other aspects of sexual reproduction
GH
growth hormone, has targets in most tissues. triggers secretions from liver cells that promote growth of bone and soft tissues in the young, influences metabolism in adults
PRL
initiates and maintains milk production in mammary glands after other hormones prime the tissues
Thyroid Gland
Anterior base of the beck, secretes calcitonin and thyroid hormone, which is a ix of two amines
Thyroid hormone
Central to metabolism and development
How is the thyroid gland controled?
By the anterior pituitary and hypothalamus, through negative feedback loops
Parathyroid glands
Four of them on the posterior surface of the thyroid, secrete PTH. Main control over the calcium in blood
PTH
parathyroid hormone, stimulates the breakdown of bone, decreases calcium loss in urine, and activates the vitamin D needed to absorb calcium from food.
Vitamin D and PTH
PTH activates vitamin D needed to absorb calcium from food, thus, PTH increases blood calcium. Vitamin D deficiency lowers calcium level in blood, which leads to oversecretion of PTH and bone breakdown
Adrenal Glands
Humans have a pair of adrenal glands, one on top of each kidney.
Adrenal cortex
Outermost part of adrenal glands, releases steroid hormones
Aldosterone
Controls sodium and water reabsorption in the kidneys, released by adrenal glands
Cortisol
Released by adrenal glands, affects metabolism and immune responses, maintains blood level of glucose, induces liver cells to break down their store of glycogen, supresses uptake of glucose by other cells. induces adipose cells to degrade other fats, and skeletal muscles to degrade proteins, makes immune responses wind down. controled by negative feedback loop
When and by what is the cortisol feedback loop overridden?
The nervous system overrides it during times of injury, illness, anxiety. this leads to very high levels of cortisol
Adrenal medulla
Inner part of adrenal gland, secretes norepinephrine and epinephrine during times of stress, excitement, or danger.
Norepinephrine and epinephrine
Same effects on targets that sumpathetic nerves do, bring about fight-or-flight response
Long term elevation of cortisol levels?
Disrupts production and release of other hormones, suppress immune function, impair memory. impact can be seen in people with Cushing syndrome
Pancreas
in abdominal cavity behind the stomach, has exocrine (scretes digestive enzymes into duct to small intestine) and endocrine functions (clusters called pancreatic islets, contains three types of hormone-secreting cells)
Alpha cells
Secrete the peptide hormone glucagon. between meals, all cells take up glucose from blood. When glucose level falls below set point, alpha cells secrete glucagon, which binds cells int he liver and causes activation of enzymes that break glycogen into glucose subunits. Raises level of glucose in the blood
Beta cells
Most abundant cells in pancreatic islets, secrete insulin, the only hormone that causes target cells to take up and store glucose. Releases insulin after stimulated by higher blood level of glucose
Delta cells
Secretes somatostatin, helps control digestion and nutrient absorbtion. Can inhibit the secretion of insulin and glucagon
Diabetes mellitus
Metabolic disorder in which cells do not take up glucose as they should, in result, sugar accumulates in blood and urine. This encourages growth of pathogenic bacteria, damages small blood ells in kidneys, permanent kidney failure. Uncontrolled diabetes also damages blood vessels and nerves, especially in arms, hands, legs, and feet
Type I Diabetes
Develops after the body has mounted an autoimmune response against is insulin-secreting beta cells. Most dangerous type of diabetes short term. In absence of glucose, the body uses fats and proteins as energy sources. Two outcomes are weight loss and ketone accumulation in the blood and urine. Can interfere with brain funtion, extreme causes may lead to coma or death
Type II Diabetes
More common form of disorder. Insulin levels are normal or high but target cells do not respond to the hormone as they should and blood sugar levels remain high. If glucose lvels are not lowered, pancreatic beta cells continue to receive continual stimulation and they will eventually falter
Hypoglycemia
Blood glucose level falls low enough to disrupt normal body functions. Rare insulin-secreting tumours can cause it, but usually after insulin-dependent diabetic miscalculates and injects too much insulin to balance food intake. Results in insulin shock, brain stalls as its fuel dwindles. Can be lethal, but injection of glucagon reverses condition
Gonads
Male = testes, females = ovaries. produces gametes and secrete sex hormones, including estrogens and androgens
Puberty
Post-embyronic stage of development when the reproductive organs and structures mature
Estrogen in males
Develops sperm
Testosterone in females
Affects libido
Pineal Gland
Depp inside the vertabrate brain. Secretes melatonin, which serves as part of internal timing (biological clock, rate of secretion varies depending on amount of light brain is responding to.
Thymus gland
Lies beneath breastbone, secretes hormones that help infection-fighting white blood cells (T cells) to mature, grows until person reaches puberty, when the surge in sex hormones causes it to shrink and its secretions decline
How did vertabrates evolve so many diverse hormones and hormone receptors?
Molecular evidence points to gene duplications and subsequent divergences through mutations
Ecdysone
Steroid hormone, controls molting in nematodes and arthropods, influences by environmental cues
