Lecture 7 Flashcards
(16 cards)
What amino acid is utilized to make norepinephrine and epinephrine? Where does this occur in the body, and where in the cell?
What other signaling molecule is made through the conversion of tyrosine to norepinephrine/epinephrine?
Write out the pathway with which tyrosine is converted to epinephrine and norepinephrine. What purpose may the secretory vesicle/granule serve with regards to epinephrine/norepinephrine?
Tyrosine is the beginning! The other signaling molecule is made through the tyrosine to norepinephrine/epinephrine is dopamine.
Tyrosine –> dihydroxyphenylalanine (DOPA) –> Dopamine –> dopamine in the secretory granule –> norepinephrine –> norepinephrine leaves the cell –> epinephrine
Both are coordinated to ATP in a crystalline form and held in the secretory granule until they are ready to be released
When is epinephrine important and why?
low levels of glucose - body will release epinephrine (hormone) as well as lower levels of norepinephrine (neurohormone)
Epinephrine binds to beta-adrenergic receptors on liver cells which signal for an increase in glycogen breakdown
1) What is dopamine and norepinephrine secreted by?
2) Norepinephrine is secreted by both what?
3) Epinephrine is synthesized and secreted only by what cells?
4) All of the catecholamines can act as _______, but dopamine and norepinephrine are also ______.
5) DOPA is not secreted in the body, but it can be administered as a drug to increased what? (for Parkinson’s disease)
1) neurons
2) neurons, chromaffin cells
3) chromaffin
4) neurohormones, neurotransmitters
5) Dopamine secretion
Why isn’t dopamine secreted by chromaffin cells?
It’s a neurotransmitter so it’s only secreted by neurons.
How does the injection of DOPA into Parkinson’s patients allow them to find relief from their shakiness?
Dopamine is a neurotransmitter which helps control smooth muscle contraction. By injecting DOPA, it will have a more prolonged effect than just dopamine.
What catecholamines experience reuptake (where neurotransmitters are reabsorbed by the presynaptic neuron from which they were secreted?)
Dopamine and norepinephrine (NEUROTRANSMITTERS)
What enzymes that act on circulating catecholamines in order to break them down, and what is produced as a result of these enzymes acting on the catecholamine?
monoamine oxidase and catechol-o-methyl transferase
either enzyme (in the liver) can act first, but BOTH must act. This leads to vanillylmandelic acid (VMA).
How is the fight or flight response mediated, and what are the effects that occur as a result of the fight or flight response becoming activated?
Input from the brain and sympathetic trunk will come together and neurons in the adrenal medulla will help signal the release of epinephrine/norepinephrine.
- increase blood pressure to better oxygenate tissues
- increase cardiac output for more oxygen
- increase BMR
- intestinal inhibition (stops processes that aren’t essential for immediate survival)
What are the two major classes of catecholamine receptors? What similarities do these receptors share, and what is the main difference between the two?
alpha-adrenergic and beta-adrenergic receptors that are differentiated by the relative binding affinities for epinephrine and norepinephrine
They are all g-protein linked, but produce different responses
Compare and contrast the subclasses of alpha and beta-adrenergic receptors.
alpha-1 responds to epinephrine better, while alpha-2 responds to norepinephrine better.
Alpha-1 works with the IP3/DAG pathway (Ca++). Alpha-2 works with cAMP, but decreases the amount of cAMP.
Beta-1 binds to epinephrine or norepinephrine. Beta-2 binds to epinephrine. Beta-1 Is found in the heart and Beta-2 is throughout the rest of the body.
What structures is the pineal gland derived from and what is its purpose?
The synthesis and secretion of serotonin and melatonin is regulated by light: serotonin secreted during daylight, melatonin secreted in response to darkness. Response to light by eyes (to pineal gland) regulates this (circadian rhythm)
Explain each circadian situation. What does it mean and why does it make sense?
1) melatonin increases at 9 pm and peaks at 4 am
2) Core body temperature decreases when melatonin increases
3) Triacylglycerol has about the same curve pattern as melatonin
4) Alertness starts to drop at 9 pm and is the worst at 7 am
5) Reaction time is best at 8 am
1) Melatonin is secreted in response to darkness
2) Body temperature starts to drop because a lot of things shut down when asleep
3) Body needs to obtain energy so triacylglycerol concentration increases
4) Tired = less alert and cognitive abilities suck
5) Tired = less likely to have good reaction time to things
What are neurohormones and how do they work? How are they different from neurotransmitters? What endocrine glands use neurohormones?
Neurohormones are hormones that are released from neurons. Secretory neuron receives the signal and carries out action potentials to release the neurohormone into the blood and it will bind to the target cell. They cover longer distances than neurotransmitters because they are released into the bloodstream. The endocrine glands that can signal through neurohormones are the posterior pituitary and the adrenal medulla
What are the two anatomic sections of the adrenal gland and what are they derived from/composed of?
outer cortex and inner medulla
The adrenal medulla contains the chromaffin cells (responsible for the production and secretion of epinephrine and norepinephrine
What are the two hormones that are secreted by the chromaffin cells of the adrenal medulla, and what class of compounds do these hormones fall under? How are these two hormones released by your body?
Epinephrine and norepinephrine (catecholamines)
Norepinephrine: neurotransmitter but it doesn’t act like one when it’s secreted by the chromaffin cells. It circulates the blood and acts as a neurohormone
Are the effects of norepinephrine different from epinephrine when it binds to a target receptor and exerts its effect?
Epinephrine is always a hormone, but never a neurotransmitter. Norepinephrine can be either (secreted from chromaffin cells = neurohormone, secreted from brain = neurotransmitter)
