Hormones Flashcards
Feedback regulation and coordination with the nervous system are common in
endocrine signaling.
What is the endocrine system and what does it regulate?
chemical signaling by hormones- it is one of the two basic systems for communication and regulation in the animal body.
What is a simple endocrine pathway? What is negative feedback?
Endocrine cells respond directly to an internal or environmental stimulus by secreting a particular hormone. Hormone travels in the bloodstream to target cells where it interacts with specific receptors- physiological response.
Negative- response reduces the initial stimulus
What is a simple neuroendocrine pathway? What is positive feedback?
The stimulus is received by a sensory neuron, which stimulates a neurosecretory cell. Then secretes a neurohormone, which diffuses into the bloodstream and travels to target cells.
Positive- reinforces a stimulus, leading to an even greater response
Why are insulin and glucagon considered to be an antagonistic hormone pair?
They are opposing each other. When blood glucose is high insulin is released and when it is low, glucagon is released
What do insulin and glucagon regulate?
Blood glucose level
Insulin and glucagon- What types of pathways are these? What type of feedback is involved in each?
Simple endocrine pathway - negative feedback
How is insulin doing its job of lowering blood glucose levels?
the secretion of insulin triggers the uptake of glucose from the blood into body cells, decreasing the blood glucose concentration
What’s the deal with the liver and glycogen in the presence of insulin?
Rising levels of insulin promote biosynthesis of glycogen from glucose entering the liver in the hepatic portal vein
How is glucagon doing it’s job of raising blood glucose levels?
The secretion of glucagon promotes the release of glucose into the blood from energy stores increasing the blood glucose concentration
What’s the deal with the liver and glycogen in the presence of glucagon?
When blood in the hepatic portal vein has a much lower glucose concentration, glucagon stimulates the liver to break down glycogen, convert amino acids and glycerol to glucose, and release glucose into the blood
What causes diabetes mellitus?
a deficiency of insulin or a decreased response to insulin in target tissues
What happens with regard to glucose?
Blood glucose levels rise, but cells are unable to take up enough glucose to meet metabolic needs - thus fat becomes the main substrate for cellular respiration
What can happen when fat becomes the main substrate for cellular respiration? What happens in the kidneys?
acidic metabolites formed during fat breakdown accumulate in the blood, threatening life by lowering blood pH and depleting sodium and potassium ions from the body;
The level of glucose in the blood may exceed the capacity of the kidneys to reabsorb the nutrient. glucose that remains in the kidney filtrate is excreted
What kind of disease is type 1 diabetes (insulin-dependent diabetes)?
An autoimmune disorder in which the immune system destroys the beta cells of the pancreas- destroying the person’s ability to produce insulin
When does type 1 diabetes usually show up?
During childhood
What is type 2 diabetes (non-insulin-dependent diabetes)?
A failure of target cells to respond normally to insulin
What significantly increases the risk of type 2 diabetes?
excess body weight and lack of exercise
When does type 2 diabetes usually show up?
After age 40
The hypothalamus plays a central role in integrating the
endocrine and nervous systems.
What exactly is the hypothalamus doing?
receives information from nerves throughout the body and, in response, initiates endocrine signaling appropriate to environmental conditions
Where does the hypothalamus receive signals from?
Nerves throughout the body
Where does the hypothalamus send signals to?
the pituitary gland
Is the posterior pituitary an endocrine gland unto itself?
It is an extension of the hypothalamus
Where do posterior pituitary hormones come from?
the Hypothalamus
Is the anterior pituitary an endocrine gland unto itself?
Yes, it synthesizes and secretes hormones in response to hormones from the hypothalamus
Where do anterior pituitary hormones come from?
the anterior pituitary gland
Where are the posterior pituitary hormones oxytocin and antidiuretic hormone (ADH) being synthesized? Where are they being stored?
the hypothalamus; the posterior pituitary gland
How do oxytocin and ADH get from the hypothalamus to the posterior pituitary?
travel within the long axons of the neurosecretory cells
What stimulates oxytocin and ADH release from the posterior pituitary?
nerve impulses transmitted by the hypothalamus
What does oxytocin do?
multiple function related to reproduction; in female mammals it controls milk secretion and regulate uterine contractions during biting; also influences behaviors related to maternal care, pair bonding, and sexual activity
What does ADH do?
regulates kidney function; it increases water retention in kidneys, helping maintain normal blood osmolarity; also role in social behavior
Where are the anterior pituitary hormones being synthesized?
in the anterior pituitary gland
How is secretion of the anterior pituitary hormones regulated?
by hormones secreted by the hypothalamus
What is a hormone cascade in general? Look at thyroid hormone secretion regulation
Signals to the brain stimulate the hypothalamus to secrete a hormone that stimulates or inhibits release of an anterior pituitary hormone. This acts on another endocrine organ, stimulating secretion of another hormone, which exerts effects on specific target
What is hypothyroidism?
the secretion of too little thyroid hormone, can cause weight gain, lethargy, and intolerance to cold
What is hyperthyroidism?
can lead to high body temperature, profuse sweating, weight loss, irritability, and high blood pressure
What are thyroid hormones?
a pair of very similar hormones derived from the amino acid tyrosine. Triiodothyronine contain 3 iodine atoms where, thyroxine contains 4
What does dietary iodine have to do with anything?
Thyroid hormone production requires iodine
What does normal thyroid function lead to in humans and other vertebrates?
normal functioning of bone-forming cells, and branching of nerve cells during embryonic development of the brain
What are tropic hormones?
hormones that redirect signals from the hypothalamus to other endocrine glands
What are nontropic hormones?
hormones that affect the signal directly
Why are FSH, LH, TSH, and ACTH tropic hormones?
Because they convey signals from the hypothalamus to another gland
Why are MSH and prolactin nontropic hormones?
Because one gland directly simulates something
Why is GH both tropic and nontropic?
because it directly stimulates but also triggers other endocrine glands
What’s the deal with the liver and insulin-like growth factors (IGFs)?
They circulate in the blood and directly stimulate bone and cartilage growth
What is the result of hypersecretion of GH in humans?
leads to gigantism if during childhood; leads to bony growth in the face, hands and feet if during adult (acromegaly)
What is the result of hyposecretion of GH in humans?
in childhood retards long-bone growth and can lead to pituitary dwarfism
What is the common role of thyroxine across many evolutionary lineages?
regulates metabolism
What is the role of
thyroxine in frogs?
Stimulating tail reposition during metamorphosis
Tell me about the diverse functions of prolactin.What does it do in mammals? What does it do in birds? What does it do in amphibians? What does it do in freshwater fishes? What does this suggest about prolactin from an evolutionary point of view?
mammals- stimulates mammary gland growth and milk synthesis
birds- regulates fat metabolism and reproduction
amphibians- delays metamorphosis
Freshwater fish- regulates salt and water balance
Suggests that prolactin is an ancient hormone with functions that have diversified during the evolution of vertebrate groups
What are the diverse functions of melanocyte-stimulating hormone (MSH)? What does it do in amphibians, fishes, and reptiles? What does it do in humans?
amphibians, fishes and reptiles- regulates skin color by controlling pigment distribution in skin cells called melanocytes
humans- hunger and metabolism in addition to skin coloration
How might the specialized action of MSH that has evolved in the mammalian brain prove to be of medical importance? What is cachexia?
Many patients with late-stage cancer, AIDS, tuberculosis, and certain aging disorders suffer from a devastating wasting condition call cachexia- characterized by weight loss, muscle atrophy and loss of appetite.The blockage of brain receptors for MSH prevented cachexia
