Term
| What is paracrine release? |
|
Definition
| Release of a single molecule or hormone within a single tissue (not at a synapse) which acts on other cells within the same tissue |
|
|
Term
| What is autocrine release? |
|
Definition
| When a signaling molecule is released by a cell and acts back on the same cell. |
|
|
Term
| What is endocrine release? |
|
Definition
| Release of hormones into the blood stream that then acts on faraway targets in the body. |
|
|
Term
| What are the major functions of hormones? |
|
Definition
• Regulate ion/water balance
• Contribute to the response to external stress
• Initiate steps in growth and development
• Regulate process of reproduction
• Regulate the digestion, use and storage of nutrients
• Regulate the release of other hormones |
|
|
Term
| Which gland responds primarily in stress responses? |
|
Definition
|
|
Term
| True or false: The heart can function as an endocrine organ as well as a cardiovascular pump. |
|
Definition
| True - the heart has a mixed function as an endocrine organ as well as the pump. |
|
|
Term
| Which organ controls the body rhythms entrained by light stimulation? Also, what is the name of this rhythm cycle? |
|
Definition
The pituitary gland.
The rhythm cycle that it controls is the circadian rhythm. |
|
|
Term
| Which organ controls the release of hormones from the anterior pituitary gland? |
|
Definition
| The hypothalamus releases hormones that stimulate the anterior pituitary. |
|
|
Term
| What are the kinds of hormones released by the hypothalamus? |
|
Definition
| Releasing hormones or inhibitory hormones. |
|
|
Term
| What are the hormones which the anterior pituitary releases? What are their functions? |
|
Definition
Thyroid-stimulating hormones - causes the secretion of T3 and T4 from the thyroid.
Adrenocorticotropic hormone - stimulates cortisol secretion from the zona fasiculta and zona reticularis of the adrenal cortex
Growth hormone - essential but not solely responsible for growth.
FSH (follicle stimulating hormone) - effects the females ovarian follicles… stimulates follicular growth/development + stimulates estrogen secretion. |
|
|
Term
| What are the hormones that the posterior pituitary releases? |
|
Definition
Vasopressin - increases h2o absorption in the kidney tubules (distal tubule)
Oxytocin - increases contractility of the uterus and is the primary hormone involved in the "let down reflex" (milk ejection from the breasts) |
|
|
Term
| What hormone is released from the pineal gland? What does it target and what is its function |
|
Definition
Melatonin --> effects the brain and the anterior pituitary, immune system, possibly others.
Entrains the bodies biological rhythm (circadium rhythms) inhibits gonadotropins, acts as antioxidant and enhances immunity. |
|
|
Term
| What are the hormones which the anterior pituitary releases? What are their functions? |
|
Definition
Thyroid-stimulating hormones - causes the secretion of T3 and T4 from the thyroid.
Adrenocorticotropic hormone - stimulates cortisol secretion from the zona fasiculta and zona reticularis of the adrenal cortex
Growth hormone - essential but not solely responsible for growth.
FSH (follicle stimulating hormone) - effects the females ovarian follicles… stimulates follicular growth/development + stimulates estrogen secretion. |
|
|
Term
| What are the hormones that the posterior pituitary releases? |
|
Definition
Vasopressin - increases h2o absorption in the kidney tubules (distal tubule)
Oxytocin - increases contractility of the uterus and is the primary hormone involved in the "let down reflex" (milk ejection from the breasts) |
|
|
Term
| What hormone is released from the pineal gland? What does it target and what is its function |
|
Definition
Melatonin --> effects the brain and the anterior pituitary, immune system, possibly others.
Entrains the bodies biological rhythm (circadium rhythms) inhibits gonadotropins, acts as antioxidant and enhances immunity. |
|
|
Term
| What is leutenizing hormone? Where is it released from and what does it do? |
|
Definition
| Targets the ovarian follicle and corpus luteum in order to stimulate ovulation, corpus luteum development and estrogen/progesterone secretion. |
|
|
Term
| Where does tetraiodothyronine (t4 or thyroxine) come from? |
|
Definition
| It is secreted by the thyroid gland follicular cells and increases metabolic rate. |
|
|
Term
| What does aldosterone do? |
|
Definition
| Increases sodium reabsorption and potassium secretion in the kidneys. |
|
|
Term
| Epinephrine and norepinephrine are produced where? What do they do |
|
Definition
In the adrenal medulla
Function as part of the sympathetic nervous system |
|
|
Term
| Through what actions do hormones act? |
|
Definition
1) Alters channel permeabilities
2) Acts through secondary messenger systems (major)
3) Activates specific genes to cause formation of new proteins (slow) |
|
|
Term
| Describe the hormonal response. |
|
Definition
1) Endocrine gland synthesizes and releases hormones
2) The hormones come into contact with their target cell and bind to receptors on the cell surface which can have a few different effects
1. Altering of channel permeabilities
2. Activation of secondary messenger systems (major function)
3. Activation of gene transcription for formation of new proteins (slow)
3) Physiological response |
|
|
Term
| Describe the mechanism behind the parathyroid hormones receptors function. |
|
Definition
The parathyroid hormone receptor is a g-protein coupled receptor.
When activated, its alpha unit activates adenylyl cyclase which increases the concentration of cAMP.
The increase in cAMP causes the activation of PKA (protein kinase A) which then phosphorylates (?) |
|
|
Term
| Describe the mechanism behind the receptors function for arganine vasopressin. |
|
Definition
The arganine vasopressin receptor is a g-protein coupled receptor.
The alpha sub unit than binds to PLC, which then breaks down (?) into IP3 and DAG.
IP3 leads to the release of calcium from intracellular stores
DAG leads to the activation of protein kinase C |
|
|
Term
True or false:
Thyrotropin-releasing hormone acts through a g-protein coupled receptor to activated PLA2 which leads to modulation of arachidonic acid metabolism |
|
Definition
|
|
Term
| True or false: the receptor for arganine vasopressin is an ionic channel which opens when Vasopressin binds to it |
|
Definition
False.
It is a g-protein coupled receptor that leads to the activation of PLC by the alpha unit which increases the production of IP3 and DAG. |
|
|
Term
| Which hormones lead to the activation of tyrosine kinase? |
|
Definition
| Growth hormone and insulin |
|
|
Term
| True or false --> parathyroid receptor's mechanism acts through the activation of adenylyl cyclase which activates PKA |
|
Definition
|
|
Term
| How are hormone levels controlled? |
|
Definition
| Through tightly regulated feedback loops. |
|
|
Term
| What regulates the release of both ACTH and CRH? |
|
Definition
| Cortisol acts as the regulator ---> high concentrations inhibit the release of CRH from the hypothalamus and ACTH from the anterior pituitary. |
|
|
Term
| Where is CRH released from? |
|
Definition
|
|
Term
| Where is ACTH released from? |
|
Definition
|
|
Term
| Describe a simple feedback loop for hormonal regulation. |
|
Definition
| Sensor regulates the release of a hormone. That hormone then acts on a target tissue and causes the production and release of some sort of metabolite or signalling molecule. The increased concentration of this metabolite/signalling molecule will act on the sensor and will cause it to respond. |
|
|
Term
| Describe the hormonal regulation of cortisol. What type of regulation is this? |
|
Definition
It is hierarchical regulation.
The cerebral cortex sends a signal to the hypothalamus, which then releases CRH. This CRH then stimulates the anterior pituitary to release ACTH. ACTH then acts on the adrenal cortex to release cortisol which acts on the target tissues.
Cortisol functions as an inhibitor for the release of CRH from the hypothalamus as well as ACTH from the adrenal cortex. |
|
|
Term
| What cell releases insulin? |
|
Definition
| The beta cells in a pancreatic islet (of langerhans) |
|
|
Term
| True or false: lipophilic molecules can freely move through the blood stream to act on target tissues |
|
Definition
| False. Lipophilic molecules must first be bound to plasma proteins before it can be transported to target tissues. |
|
|
Term
| How can lipophilic molecules travel through the blood stream? |
|
Definition
| They become bound to plasma proteins (albumin, ) which facilitates their movement through blood plasma. |
|
|
Term
| Steroids are formed from what precursor molecule? |
|
Definition
|
|
Term
| What type of hormone is vasopressin? |
|
Definition
| Peptide hormone composed of specific amino acids. |
|
|
Term
| Where are peptide hormones synthesized? Name one. |
|
Definition
Synthesized within the rough endoplasmic reticulum, then is packaged within the golgi complex.
Vasopressin is a peptide hormone synthesized in this manner |
|
|
Term
| How are peptide hormones transferred within the blood? |
|
Definition
| Freely, not bound to proteins. |
|
|
Term
| Where can peptide hormones be found? |
|
Definition
All hormones of the:
Hypothalamus
Anterior pituitary
Posterior pituitary
Pancreas
Parathyroid gland
Gastrointestinal tract
Kidneys
Liver
Thyroid C cells (produce T3 and T4)
Heart |
|
|
Term
| What are the types of amine hormones? |
|
Definition
| Catecholamines and thyroid hormones |
|
|
Term
| Catecholamines are synthesized from what precursor molecule |
|
Definition
| Catecholamines are tyrosine derivatives |
|
|
Term
| Where are catecholamines synthesized and stored? |
|
Definition
Synthesized: cytoplasm
Stored: chromaffin granules and some binding proteins |
|
|
Term
| How are catecholamines transported within circulation? |
|
Definition
| Half-bound to plasma proteins. |
|
|
Term
| In what organs can we find concentrations of catecholamines? |
|
Definition
| Only within the adrenal medulla |
|
|
Term
| What is catecholamines mechanism of action? |
|
Definition
| Mechanism is through the activation of a secondary messenger that alters the activity of preexisting proteins to produce the desired effect |
|
|
Term
| Amines are produced from what molecule? |
|
Definition
Catecholamines = tyrosine derivatives
Thyroid hormones = iodinated tyrosine derivative |
|
|
Term
| Are thyroid hormones lipophillic or hydrophillic? |
|
Definition
|
|
Term
| What is catecholamines mechanism of action? |
|
Definition
| Mechanism is through the activation of a secondary messenger that alters the activity of preexisting proteins to produce the desired effect |
|
|
Term
| Amines are produced from what molecule? |
|
Definition
Catecholamines = tyrosine derivatives
Thyroid hormones = iodinated tyrosine derivative |
|
|
Term
| Are thyroid hormones lipophillic or hydrophillic? |
|
Definition
|
|
Term
| How are thyroid hormones transported in the blood? |
|
Definition
| Because they're lipophillic molecules, they're mostly transported by being attached to other proteins. |
|
|
Term
|
Definition
|
|
Term
| Where are peptide hormones synthesized? |
|
Definition
| In the endoplasmic reticulum. |
|
|
Term
| Describe the synthesis of peptide hormones. |
|
Definition
Synthesized as part of larger precursor peptides. (preprohormone)
Signal sequence @ N-terminus leads to insertion into ER.
The signal sequence gets cleaved off to reveal a precursor, the prohormone
The prohormone is then cleaved to reveal the hormone molecules by endoproteases. Different ones cleave @ different sites to form different hormones. |
|
|
Term
| What is a peptide with the signalling sequence still attached called? Also, on which end would the signalling sequence be on? |
|
Definition
Signalling sequence is on the N-terminus.
Preprohormone. |
|
|
Term
| What is a peptide called once the signalling sequence has been cleaved off it's N-terminus? |
|
Definition
|
|
Term
| Which is cleaved to reveal the hormone molecule, the preprohormone or the prohormone? |
|
Definition
|
|
Term
| True or false: hormones are packaged into vesicles at the cis-golgi and endocytosis of those vesicles occurs at the trans-golgi |
|
Definition
|
|
Term
| Describe the synthesis of catelcholines. What enzymes are involved? |
|
Definition
Precursor molecule: tyrosine.
Occurs in the cytosol:
1) Tyrosine is converted into DOPA by the enzyme tyrosine hydroxylase
2) DOPA is then converted, by dopa-decarboxylase, into Dopamine
Occurs in the chromaffin cells:
1) Dopamine is converted by dopamine B-carboxylase into norepinephrine
Transported to the cytosol:
1) Norepinephrine is converted by phenethanolamine N-methyltransferase into epinephrine. |
|
|
Term
| Where are steroid hormones released from? |
|
Definition
|
|
Term
| What is the intermediate between cholesterol and aldosterone? |
|
Definition
| Cholesterol --> progesterone --> aldosterone |
|
|
Term
| What is the intermediate between cholesterol and estrone? |
|
Definition
Cholesterol --> Progesterone --> Estrone
Cholesterol --> intermediates --> esterone |
|
|
Term
| What types of hormones are bound to plasma proteins? Give an example of some |
|
Definition
Lipophilic molecules are typically bound to plasma proteins.
Example: T3 and T4 from the thyroid gland |
|
|
Term
| Why is there an increase in plasma binding proteins during pregnancy? |
|
Definition
| Because there's an increase in blood flow. This will send cause a feedback response in the body that stimulates the body to synthesize more and to synthesize more of the hormones that bind to it. |
|
|
Term
| What are the general types of endocrine disorders? |
|
Definition
Where there can be too much or too little hormone activity.
Too little activity = hyposecretion
- Increased removal from blood
- Abnormal tissue responsiveness to hormone
○ Lack of target cells/receptors
○ Lack of essential enzyme essential to target-cell process
Too much activity = hypersecretion
- Increased biologically free hormones (reduced plasma proteins)
- Decreased removal of hormone from blood
○ Decreased inactivation
○ Decreased excretion |
|
|
Term
| How can you quantify the amount of hormones in the blood? |
|
Definition
1) Radioimmunoassay
1. Displacement curve
**radioimmunoassay can also be used to quantify the # of hormone receptors in a tissue + the affinity of the hormone-receptor interaction |
|
|
Term
| What type of tissue is the posterior pituiatary made up of? |
|
Definition
| Its made up of mostly axon terminals -- this is because it is made up of nerve endings that originate from the hypothalamus |
|
|
Term
| What is the neurohypophysis? |
|
Definition
| The posterior pituitary. It is called this because it is an extension of the hypothalamus |
|
|
Term
| Describe the neuronal connection between the anterior/posterior pituitary gland and the hypothalamus |
|
Definition
Paraventricular nucleus and supraoptic nucleus have axons that lead down through the hypothalamic posterior pituitary stalk and terminates into the posterior pituitary.
Action potentials fired in the cell bodies located in the neurosecretory neurons of the hypothalamus travel down the axons that terminate in the posterior pituitary where they release vasopressin and oxytocin (or calcium). |
|
|
Term
| What type of cells make up the anterior pituitary? |
|
Definition
| A glandular epithelial tissue. |
|
|
Term
|
Definition
|
|
Term
| How is the release of hormones from the anterior pituitary stimulated? |
|
Definition
| Hyperphysotropic releasing hormones act on the hypophys (pituitary tissue) and cause the release of other hormones. |
|
|
Term
| What are the different types of hormone-releasing cells found in the anterior pituitary gland? |
|
Definition
Somatotrophs --> release growth hormone
Corticotrophs --> release adrenocorticotropic hormone (ACTH)
Thyrotrophs --> release thyroid stimulating hormone (TSH)
Lactotrophs --> release prolactin (PRL)
Gonadotrophs --> release leureinzing hormone (LH) and follicle-stimulating hormone (FSH) |
|
|
Term
| What type of hormones are released from the anterior pituitary? |
|
Definition
|
|
Term
| In the peptide hormones that are composed of a beta and alpha sub unit, which is the most important for its actions? |
|
Definition
| Determined by the different beta sub units |
|
|
Term
| What does the anterior pituitary regulate? |
|
Definition
| Regulates reproduction, growth, energy response, and the stress response. Most are tropic. |
|
|
Term
| Laron dwarfism is caused by what? |
|
Definition
| It is caused by abnormal GH receptors. |
|
|
Term
| Individuals with laron syndrome seem to have a lower occurrence of what major disease? |
|
Definition
|
|
Term
| What does an excess of GH during adulthood do? |
|
Definition
It causes a condition known as acromegaly which occurs after the bones have fused which is marked by a thickening of the bones of the hand, feet, and face.
Also the enlargement of certain organs such as the heart and liver. |
|
|
Term
| If you cut the pituitary stalk, what will happen to the hormonal release in the anterior pituitary? |
|
Definition
| If you cut the pituitary stock most of the hormones would then decrease in secretion. However, prolactin secretion increases. |
|
|
Term
| Describe the release of cortisol. |
|
Definition
Stress causes the stimulation of small-bodies neurons in the paraventricular nucleus of the hypothalamus, causing them to secrete CRH.
CRH binds to GPCR on the corticotroph membrane, triggering an adenylyl cyclase/cAMP/PKA leading to the release of preformed ACTH.
ACTH then binds to the receptors on the adrenal cortex triggering AC/cAMP/PKA response causing the conversion from cholesterol ---> prognenolone --> cortisol |
|
|
Term
| What are the activators for GH and the inhibitors of GH secretion? |
|
Definition
| GHRH activates the release of GH from somatotrophs from the anterior pituitary. Both act through G-protein receptors that regulate adenylyl cyclase and cAMP levels if somatotrophs. |
|
|
Term
| Where are the hormones AVP and oxytocin synthesized? |
|
Definition
| In the supraoptic nuclei and paraventricular nuclei. |
|
|
Term
| Which type of receptor is key in controlling emotions and cognition? |
|
Definition
|
|
Term
| Terratoma is associated with what? |
|
Definition
| Associated with an autoimmunity to NMDA receptors. |
|
|
Term
|
Definition
It is the primary hormone regulating water balance in the body.
It has a vasoconstrictive effect in large doses (causes increase in blood pressure ) |
|
|
Term
| Where are the cell bodies that innervate the posterior pituitary |
|
Definition
| Found in the supraoptic nucleus and the paraventricular nucleus. They send their axons down the pituitary stalk and terminate in the posterior pituitary. |
|
|
Term
| What does osmolality mean? |
|
Definition
| Refers to the total concentration of solute molecules expressed per kg of water. |
|
|
Term
| What does osmolarity mean? |
|
Definition
| Refers to the total concentration of solute expressed per L of water. |
|
|
Term
| How do animals maintain their osmolality? |
|
Definition
Through the excretion and reabsorption of water and sodium.
Hypotonic: increase feelings of thirst, increase release of vasopressin (increase in urine production).
Increase sodium appetite, decrease sodium excretion.
Hypertonic: increase feelings of thirst, increase release of vasopressin (decrease in urine production).
Decrease sodium appetite, increase sodium excretion |
|
|
Term
| If you remove the posterior pituitary gland, what happens to osmolality regulation? |
|
Definition
| The release of vasopressin is halted. |
|
|
Term
| What type of secretory cells are responsible for the release of vasopressin? |
|
Definition
Magnocellular neurosecretory cells
Also responsible for the release of oxytocin. |
|
|
Term
| True or false: OVLT and SFO have excitatory inputs on magnocellular secretory cells. What is OVLT and SFO |
|
Definition
|
|
Term
| True or false: magnocellular neurosecretory cells release both oxytocin and vasopressin |
|
Definition
| False. They release only one or the other. |
|
|
Term
| Vasopressin is synthesized as part of what larger peptide? |
|
Definition
|
|
Term
| What is the name of the axons in the pituitary stalk? |
|
Definition
|
|
Term
| Neurophysin I is associated with what? |
|
Definition
|
|
Term
| Neurophysin II is associated with what? |
|
Definition
|
|
Term
| What is the osmotic threshold? |
|
Definition
| Above the threshold gives an increase in vasopressin which causes a decrease in the production of urine. |
|
|
Term
In the instance of a volume expansion we can expect vasopressin release to
a) Decrease
b) Increase
c) Not change
d) None of the above |
|
Definition
| We expect vasopressin release to decrease |
|
|
Term
| Increase/decrease in firing in MNC depends on input from what? |
|
Definition
Changes in plasma volume: Baroreceptors
Changes in osmolality: depends on cells that are sensitive to osmolality in the OVLT and SFO.
Increase in temperature increases the firing rate of MNCs
Stimulation of the nipples can cause rapid firing and initiate the letdown reflex. |
|
|
Term
|
Definition
| Organum vasculosum laminae terminalis |
|
|
Term
What does the mechanism by which the MNC's detect changes in external osmolality depend on?
How can they do this? |
|
Definition
Depends on osmotically-evoked change in cell volume.
This is due to the fact that they lack the usual mechanism for compensatory changes in cell volume. (Ie the osmosensitive TRPV1 channels are not there) |
|
|
Term
| How do osmosensitive cells work? |
|
Definition
During hypotonicity, cells will expand and swell. Because they possess stretch sensitive channels which are inactivated when stretched, expansion will close them.
This causes the cell to become less excitable.
During hypertonicity, cells will shrink. This will cause an increase in the opening of these stretch receptor cells and will tend to move ions out of the cell.
The channels are TRPV1 channels |
|
|
Term
| What does it mean if you see a decrease in conductance? |
|
Definition
| G is the reverse of resistance. If you see an increase in conductance than there's a decrease in resistance through the opening of channels. |
|
|
Term
| True or false: MNC's are temperature sensitive |
|
Definition
| MNC's are temperature sensitive and osmotically sensitive. The temperature dependency is part of a anticipation mechanism for increase in osmolarity. |
|
|
Term
| Where are the receptors that initiate or decrease the thirst response. |
|
Definition
Increase:
Dryness in mouth/throat
Increase plasma osmolarity
Decrease in blood volume
Decrease:
Monitoring of water intake by GI tract |
|
|
Term
| Where does vasopressin act in the nephron? |
|
Definition
• Cortical collecting duct
• Outer medullary collecting duct
• Inner medullary collecting duct |
|
|
Term
| In the nephron, AQP2 channels are found in the highest concentration in which sections? |
|
Definition
| Found in the colleting ducts (cortical, outer medullary, inner medullary collecting ducts) |
|
|
Term
| In the nephron, AQP1 channels are found in the which sections of the tubule? |
|
Definition
| High concentration in the proximal tubules and thin descending limb |
|
|
Term
| Describe the vasopressin mechanism at the cellular level in the nephron cells. |
|
Definition
Vasopressin binds to V2 receptors on the epithelial cells of the collecting ducts.
This activates a G-protein which acts on adenylyl cyclase (cAMP increase)
cAMP activates PKA which phosphorylates a number of proteins (w/ different effects)
1) Causes exocytotic fusion of vesicles that contain AQPII bind with lumen surface membrane.
2) Sustained levels of vasopressin cause the binding of cAMP to "cyclic amp response element binding protein" or CREB. This bites to a specific site on DNA "CRE site" which regulates the production of specific proteins, including AQP2 |
|
|
Term
| What is diabetes insipidus? |
|
Definition
There's urine production but does not have glucose in it.
Distinguished by its large production of very dilute urine. |
|
|
Term
| What is central or neurogenic diabetes insipidus? |
|
Definition
| Results from failure of vasopressin secretion but can still respond to it. |
|
|
Term
| What is nephrogenic diabetes insipidus? |
|
Definition
| Theres an inability for the kidneys to respond normally to vasopressin. |
|
|
Term
| What is the medicinal alternate of vasopressin? |
|
Definition
|
|
Term
| Increased injestion of alcohol causes a decrease in what? |
|
Definition
| Causes a decrease in the release of vasopressin. |
|
|
Term
| What is the hormone involve in the let down response? |
|
Definition
|
|
Term
| Which hormone is responsible for the secretion of milk. |
|
Definition
|
|
Term
| Describe the oxytocin effects in the let down effect |
|
Definition
| Triggers the contraction of the myoepithelial cells surrounding the alveoli in the lactating breast, resulting in the ejection of milk. |
|
|
Term
| How are the lactotrophs stimulated? |
|
Definition
| Through the inhibition of dopamine release from the acruate nucleus. This decrease of dopamine removes the inhibition dopamine usually exhibits on lactotrophs in the anterior pituitary, leading to prolactin release. |
|
|
Term
|
Definition
Environmental cues that entrain our biological rhythms to earths 24 hour clock.
Most important cure is light… others are temperature, sound, humidity, social interactions and availability of food. |
|
|
Term
| Around which nucleus is the internal clock centered around |
|
Definition
| Around the supraciasmatic nucleus (SCN) of the hypothalamus |
|
|
Term
| Where are the suprachiasmatic nucleus (SCN) and what is its function? |
|
Definition
| Resides within the hypothalamus. It's functions are to set circadium rhythms. |
|
|
Term
|
Definition
Clock genes are proteins that inhibit further transcription.
Primarily from two families:
Period (per1, per2, per3) and cryptochrome (cry1, and cry2) |
|
|
Term
| What does the entrainment of the SCN through light depend on? |
|
Definition
| Depends on the ganglion cells of the retina using a different photopigment called melanopsin |
|
|
Term
|
Definition
The photopigment within the ganglion cells of the retina that are involved in the light-based entrainment of the SCN.
Light detected by these photoreceptors is sent to the SCN via the retinohypothalamic tract |
|
|
Term
| What neurohormone is SCN's primary synchronizing molecule |
|
Definition
|
|
Term
| How does the SCN control metabolic and endocrine rhythms in two ways: |
|
Definition
Connections in the brain controlling sleep/wakefulness
- Control of sleep dependent hormones (prolactin and GH)
Connections to neuroendocrine systems / autonomic nervous system
Can drive these independently of sleep |
|
|
Term
| What molecules are expressed by the SCN? |
|
Definition
GABA (their primary signalling molecule)
AVP or VIP (vasoactive intestinal peptide)
**disruption of VIP causes a disruption in circadium rhythms. |
|
|
Term
| True or false: the peak of release for growth hormone occurs around midday. |
|
Definition
False.
The peak release of GH occurs during the sleep cycle. |
|
|
Term
| During the day, when is the peak release of ACTH |
|
Definition
| During the early morning hours … occurs in brief bursts |
|
|
Term
| The suprachiasmatic nucleus |
|
Definition
| Controls out internal clock |
|
|
Term
| With relation to gene transcription, circadian day is associated with what? Circadian night is associated with what? |
|
Definition
Circadian day: marked by high levels of mRNA and low protein levels
Circadian night: marked by high nuclear protein levels associated with attenuated gene expression. |
|
|
Term
|
Definition
| It is the specific pathway by which the pigment malanopsin sends its signal to the SCN's for light-entrainment of the circadian rhythms. |
|
|
Term
| This hormone is thought to be important in setting the sleep pattern in circadian rhythms. |
|
Definition
|
|
Term
|
Definition
Releases aldosterone
Found in the outermost layer of the adrenal gland |
|
|
Term
|
Definition
Releases glucocorticoids (cortisol) and androgens (DHEA and androstenedione)
Found in the second layer of the adrenal gland, between zona flomerulosa and zona reticularis |
|
|
Term
|
Definition
| Releases glucocorticoids and androgens. Found between the zona fasciculata and the adrenal medulla |
|
|
Term
|
Definition
Releases adrenalin and noradrenalin
Found in the innermost layer of the adrenal gland. |
|
|
Term
| The adrenal cortex is associated with the release of what types of hormones? |
|
Definition
| Corticosteroids (mineralcorticoids and glucocorticoids) and androgens |
|
|
Term
|
Definition
| Heat shock protein --> receptors for glucocorticoids are associated with these proteins. |
|
|
Term
| Describe the transcriptional modification through glucocorticoids. |
|
Definition
Glucocorticoids are lipophilic molecules, so they diffuse readily through membranes.
Glucocorticoid receptors are bound to shuttle proteins called HSP90 (heat-shock-protein 90kDa) which dissociates with the binding of the glucocorticoid.
The receptor then binds to sites on the DNA called "glucocorticoid response elements (GRE)" upon which the receptors dimerize, initiating the transcription of that gene into mRNA. |
|
|
Term
| Describe the transcriptional modification through thyroid hormones |
|
Definition
Thyroid hormones are lipophilic molecules that diffuse directly through the cellular, then the nucleus membrane.
In the nucleus they bind to the thyroid hormone receptor (THR) which then binds to the DNA strand.
However, a dimer with the retinoid X receptor must form before the transcription (by RNA polymerase II) can be activated. |
|
|
Term
| What is the intermediate between most hormones and cholesterol |
|
Definition
|
|
Term
| What is the rate limiting step in the formation of adrenal steroids? |
|
Definition
| Removal of the cholesterol side chain. Forms prognenolone |
|
|
Term
| What kind of steroid is aldosterone? |
|
Definition
|
|
Term
| What type of steroid is cortisol? |
|
Definition
| It is a primary glucocorticoid |
|
|
Term
| What is 17-alpha hydroxylase and where is it found? |
|
Definition
An enzyme that is found expressed in the fasciculata and reticularis layers.
It is involved in the pathways that convert cholesterol --> prognenolone --> DHEA and the pathway that converts cholesterol --> prognenolone --> cortisol. |
|
|
Term
| Which adrenal hormone does not start being produced until 7-8 years old |
|
Definition
|
|
Term
|
Definition
| Found only in the cells of the zona glomerulosa |
|
|
Term
| What is 21-hydroxylase and where is it found? |
|
Definition
| Enzyme necessary for the production of aldosterone and cortisol. |
|
|
Term
| What would happen if there were a mutation in the gene that encodes from 21-hydroxylase. |
|
Definition
| A mutation in 21-hydroxylase would cause an increase in ACTH and an overproduction of DHEA. |
|
|
Term
| Where is CRH synthesized, what is it and what does it do? |
|
Definition
CRH = corticotropin releasing hormone.
Small-bodied neurons of the hypothalamus secrete CRH which reaches the corticotrophs in the anterior pituitary through long portal veins. It stimulates the release of ACTH.
ACTH stimulates the conversion of cholesterol into pregnenolone which is then converted into other steroid hormones |
|
|
Term
| What is ACTH and what does it do? |
|
Definition
| It is a hormone released by the anterior pituitary. It stimulates the synthesis of adrenal hormones and has a trophic effect in the two inner zones of the adrenal cortex. |
|
|
Term
| Cortisol has effects which counteract the effects of what hormone? |
|
Definition
|
|
Term
| Chronic treatment with glucocorticoids can cause a deficiency in what? |
|
Definition
ACTH
Causes the atrophy of the two inner zones of the adrenal cortex |
|
|
Term
| True of false: 90% of circulating cortisol is bound to albumin. |
|
Definition
| False. 90% is bound to corticosteroid-binding globulin and 7% is bound to albumin. |
|
|
Term
| What is the pharmacological role of glucocorticoids? |
|
Definition
| They are anti-inflammatory and immunosuppressive. |
|
|
Term
| In which situations is cortisol important for? |
|
Definition
| Cortisol is involved in the breakdown of fatty acids, amino acids, and glycogen. Therefore it increases blood concentration levels of the three nutrient types. |
|
|
Term
|
Definition
| Main function is as regulatory of sodium and potassium secretion. It causes a decrease in sodium secretion and an increases potassium excretion. |
|
|
Term
| What are the regulators of aldosterone |
|
Definition
Primarily angiotension II.
Also blood potassium levels
ACTH has a weak effect |
|
|
Term
| What is primary hyperaldosteronism? |
|
Definition
| It is when there is a tumor involving the cells that release aldosterone. Causes an increase in potassium and sodium levels which can lead to hypertension. |
|
|
Term
| What is secondary hyperaldosteronism? |
|
Definition
| Where there's a problem with the tissue or hormone that's regulating the release of aldosterone (like inappropriate levels of Renin or Angiotensin II) |
|
|
Term
| What is cushings syndrom? |
|
Definition
Caused when theirs is an excessive concentration of cortisol
Can be due to an excess of either hormones regulating cortisol (ACTH and CRH)
You end up with a protein shortage and abnormal fat distribution around the face and neck. |
|
|
Term
| What can addisons disease be caused by |
|
Definition
| By micororganisms or by autoimmunity to the adrenal gland |
|
|
Term
| Which cells are model cells for studying endocrinology |
|
Definition
Chromaffin cells.
This is because they are large and round and act like a nueron because their main goal to is to secrete epinephrine |
|
|
Term
| What are the endocrine cells of the adrenal medulla called? |
|
Definition
|
|
Term
| What are chromaffin cells |
|
Definition
| They are modified sympathetic post-ganglionic neurons that release catecholamines which is primarily determined by the release of ACh from the splanchnic nerve |
|
|
Term
| What type of receptor is found on chromaffin cells that interacts with ACh. |
|
Definition
| N2 type nicotinic receptors |
|
|
Term
| The synthesis of catecholamines is regulated by what? |
|
Definition
| By sympathetic stimulation and by the release of ACTH and cortisol. |
|
|
Term
| Catecholamines are made from what precursor? |
|
Definition
|
|
Term
| Describe the enzymes that are involved in the synthesis of catecholamines |
|
Definition
Precursor: (1st) Tyrosine.
Tyrosine --- tyrosine hydroxylase ---> dihydroxyphenylalanine
Dihydroxyphenylalanine ---amino acid decarboxylase --> dopamine
Dopamine ---dopamine-beta-hydroxylase---> norepinephrine
Norepinephrine ---phenylethanolamine---> epinephrine |
|
|
Term
| Describe the cellular based synthesis of catecholamines |
|
Definition
Tyrosine precursor in cytoplasm of chromaffin cell is converted by tyrosine hydroxylase to DOPA which is then converted to dopamine by amino acid decarboxylase.
The dopamine is then taken up into the chromaffin granule in exchange for hydrogen ions (VMAT1). (H+ ions are pumped in by an HATPase)
Dopamine beta hydroxylase (found within the granule) converts dopamine into norepinephrine.
NE then leaves the chromaffin granule and is converted to epinephrine by phenylethanolamine.
Epinephrine is then re-taken up into the cell and from there it is secreted.
**chromogranin is the hormone-binding protein that enables high concentration of adrenalin in the granules. |
|
|
Term
| True or false: the adrenal medulla is activated as part of the parasympathetic response |
|
Definition
| False. It is activated as part of the sympathetic response. |
|
|
Term
|
Definition
| A rare neuroendocrine tumour of the chromaffin cells characterized by sympathetic hyperactivity. This is because chromaffin cells proliferate and release high concentrations of E and NE |
|
|
Term
| Where is the thyroid gland located? |
|
Definition
| Found in the neck, just below the pharyngeal prominance (the adams apple) on both sides of the trachea. |
|
|
Term
| Describe the cellular structure of the thyroid gland. |
|
Definition
| Composed of follicular cells that make up structures surrounding a fluid filled space called the colloid. |
|
|
Term
| Where are follicular cells found, what do they do? |
|
Definition
Follicular cells are found in the thyroid glands.
The thyroid gland is made up of many follicles, which are made up of follicular cells that surround a fluid filled space called the colloid.
The follicular cells are responsible for trapping iodide (then is converted into iodine) and the colloid is the place which thyroid hormones are synthesized. |
|
|
Term
| Thyroid hormones are synthesized from what precursor hormone |
|
Definition
|
|
Term
| What's the difference between T3 and T4? |
|
Definition
The difference is the number of iodine molecules attached there.
T4 = 4 iodine molecules (two on the inner and two on the outer ring)
T3 = 3 iodine molecules (two on the inner ring, one on the outer ring)
Reverse T3 = 3 iodine molecules (one in the inner ring, two on the outer ring) |
|
|
Term
| Which is the more active version, T3 or T4. |
|
Definition
| T3 is the more active version. |
|
|
Term
| Describe the steps in thyroid-hormone synthesis. |
|
Definition
1) Iodide is taken up into follicular cells through a co-transporter (Na+ and Iodide)
1. TSH increases the activity of the protransporter
2) Iodide is then transported into the colloid by pendrin, where it is then converted into iodine
1. A protein thyroglobulin must be transported into the colloid by exocytotic fusion - but it has many tyrosine molecules attached to it.
3) Iodination step --> iodine is added to tyrosine molecules
4) Conjucation step --> the ring from one tyrosine molecule is chemically attached to that of another (two DIT = T4, 1 MIT and 1 DIT = T3)
5) Is taken back up into the follicular cells by endocytosis. Then merges with lysosomes where proteolysis break down the thyroglobulin into T3's, T4's as well as MITs and DIT's.
6) T3 and T4 then diffuse out of the lysosendosome and go into the blood stream
**TSH is involved in increasing the activity of these steps as well as has a trophic effect. |
|
|
Term
| Where is T4 turned into T3. |
|
Definition
| In the circulation but primarily in the liver and kidneys. |
|
|
Term
| Describe the hypothalamic-pituitary-thyroid axis |
|
Definition
1) Small bodied neurons in the arcuate nucleus and median eminence of the hypothalamus secrete TRH.
2) TRH reaches the thyrotrophs in the anterior pituitary through the long portal veins.
1. TRH binds to G-protein coupled receptor on the thyrotroph membrane thus triggering DAG/IP3 pathway, leading to protein phosphorylation and raising internal calcium concentrations.
3) This stimulates the thyrotrophs to synthesize and release thyrotropin (TSH) which binds to receptors on the basolateral membrane of thyroid follicular cells, thereby stimulating G-alpha-s
4) G-alpha-s in turn activates activates adenylyl cyclase which raises cAMP.
5) TSH stimulates certain step in the synthesis and release of T4 and T3.
**somatostatin and dopamine-released by hypothalamic neurons- inhibit TSH release and thus can influence the set point at which TSH is released in response to a given amount of T3 in the pituitary. |
|
|
Term
| What is the enzyme that converts t4 into t3 |
|
Definition
5'/3'-monodeiodinase or 5/3-monodeiodinase
**5'/3' works on the outer ring (makes reverse T3)
5/3 works on the inner ring (makes T3) |
|
|
Term
| What is the action called that converts T4 to T3 |
|
Definition
|
|
Term
| Thyroxin-binding globulin |
|
Definition
| Protein that T3 and T4 are bound to in the blood. |
|
|
Term
| The thyroid hormone receptor protein dimerizes with what other protein in order to activate the synthesis of mRNA |
|
Definition
|
|
Term
| Describe the action of thyroid hormones on target cells |
|
Definition
Free T4 and T3 enter target cells.
Once inside the cell, 5'/3'-monodeisodinase converts much of the T4 into T3 (until levels of both are about equal)
Thyrodein receptors bind to nuclear DNA at TRE (thyroid response elements) in the promoter region of genes regulated by thyroid hormones.
Forms a heterodimer with retinoid x receptor. |
|
|
Term
If a child has a thyroid deficiency, what parameter will not "catch up"?
a) Bone age
b) Height age
c) Mental age
d) None of the above |
|
Definition
|
|
Term
|
Definition
| It is due to the trophic effects of TSH on thyroid tissue. This is because there is not enough iodine around to be able to produce T3 or T4 |
|
|
Term
|
Definition
Tiredness,
Weight gain,
Cold intolerance
Goitre
Mental slowness
Dry thin hair
Bradycardia |
|
|
Term
|
Definition
Weight loss
Increased appetite
Irritability
Tremor
Heat intolerance
Hyperkinesis
Tachycardia . Atrial fibrilation
Goiter
Exepothalamos |
|
|
Term
| What underlies graves disease |
|
Definition
Similar to hyperthyroidism but caused by an autoimmune disease which binds to a receptor and STIMULATES it into production of T3 and T4.
Leads to a decrease in TSH production, yet you still have a goiter. |
|
|
