Basic Endocrine Stuff
What is a hormone?
A secreted molecule that circulates in the body via blood vessel and stimulates specific cells.
The three major chemical classes of hormones.
polypeptides, steroids, amines
What is the initial stimulus in the secretin pathway?
Low pH in duodenum.
Where does oxytocin get released from?
The posterior pituitary whenever the hypothalamus says so
what is progesterone involved with in the human body?
Preparing and maintaining a fetus.
Describe what happens in a negative feedback loop.
the response reduces the initial stimulus.
ex. increase in PH throughout the intestine will turn off the release of secretin.
The water soluble hormones include:
Polypeptides and some polar(hydrophilic) amines
The end response of the secretin pathway?
bicarbonate release
The end response of this specific oxytocin pathway is...
milk release from the mammary glands.
How does the pineal gland affect our biological rhythm?
It secretes melatonin which is associated with reproduction and daily activity levels. It also has an impact on sleep cycles.
Give an example of a positive feedback loop.
in mammals, oxytocin causes the release of milk, which then encourages greater suckling from offspring that stimulates the release of even more oxytocin
The lipid soluble hormones include:
hydrophobic molecules like steroids and non polar amines
Explain the process of stimulus response during a simple endocrine pathway? Basically what does this pathway entail.
endocrine cells secrete a particular hormone based on a stimulus, the hormone circulates with the blood, interacts with specific receptors, and signal transduction within the target cell brings about a physiological response.
How is a neuroendocrine pathway different?
The stimulus is instead received by a sensory neuron which stimulates a neurosecretory cell that secretes a neurohormone. The rest is the same.
Why is thyroid regulation described as a hormone cascade?
If thyroid hormone is low:
hypothalamus secretes thyrotropin releasing hormone (TRH) --> causes anterior pituitary to secrete thyroid stimulating hormone (TSH) ---> TSH triggers release of thyroid hormone from thyroid gland.
4 general roles for endocrine signaling in the human body include:
maintaining homeostasis
mediating responses to stimuli
regulating growth and development
triggering changes to sexual maturity and reproduction
What is the difference between water soluble and lipid soluble hormones as it relates to signal reception?
Lipid soluble hormones can cross the cell membrane and bind directly to receptors in the cell cytoplasm. Water soluble hormones must use cell surface receptors, usually GPCRs.
What is the difference between the adrenal medulla and the adrenal cortex.
The medulla activates the fight or flight response and is triggered in immediate stress situations.
The cortex is for more long-term stressors like low blood sugar, dehydration, and decreased blood volume.
The hypothalamus. For oxytocin, the suckling of the infant stimulates the nervous system which generate nerve impulses in the hypothalamus to tell the posterior pituitary to release more oxytocin.
How does growth hormone work?
It is secreted from anterior pituitary gland with tropic(endocrine) and non-tropic (direct to target cell) effects. It causes the liver to release insulin like growth factors which directly stimulate bone and cartilage growth.
Explain the difference between the anterior and posterior pituitary. Also list the main hormones that each releases.
Posterior pituitary: stores and secretes hormones from the hypothalamus (ADH and Oxytocin)
Anterior Pituitary: makes and releases hormones under regulation of the hypothalamus (FSH, LH, TSH, ACTH, Prolactin, MSH, GH)
How does the solubility of a hormone affect its overall transport pathway?
Water soluble: hormones are secreted by exocytosis, travel freely in bloodstream, and bind to cell-surface receptors
Lipid soluble: hormones diffuse across cell membrane, travel in blood bound to transport proteins, diffuse through target cell membrane, and bind to receptors in cytoplasm of nucleus.
*Technically neuroendocrine*
Describe the steps of the pathway that activates a stress response when a person hiking in a national park sees a Grizzly Bear from 10 feet away.
The visual information is interpreted in the brain, hypothalamus gets that nerve info and sends a signal down the spine to the adrenal gland (atop kidneys). Since this is fight or flight, the adrenal medulla will secrete epinephrine and norepinephrine triggering glycogen breakdown, increased blood glucose, blood pressure, heart rate, breathing. Also boosts alertness and redirects blood flow to essential areas.
In what way are the hypothalamus and pituitary glands related within the endocrine system?
The hypothalamus controls all endocrine signaling and pituitary is the second step which helps by secreting specific hormones and stimulating hormones.
Explain the process of blood calcium control and the interaction of parathyroid hormone and calcitonin.
When calcium is low, PTH releases calcium from the bones and stimulates adsorption of calcium in the kidneys, also promoted vitamin D production.
When calcium is high, calcitonin stimulates deposition into the bones and excretion by the kidneys.