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4 Flashcards

1
Q

When does the size of the pituitary increase?

A

during pregnancy

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2
Q

what is the turkish saddle?

A

“Turkish saddle”, defines a superior depression of the. sphenoid bone where the pituitary gland sits. The sella turcica originally

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3
Q

how is the location of the optic chiasm and pituitary connected?

A

pituitary is located behind the optic chiasm

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4
Q

What are the components of the Hypothalamo-hypophyseal tract?

A

Hypothalamo-hypophyseal tract is derived from two different ectodermal components:

1) Oral part- Rathke’s pouch: outgrowth of the buccal cavity detaches itself and becomes the ANTERIOR pituitary
2) Neural part- The infundibulum develops from an outgrowth of the neuroectoderm from the floor of the third ventricle. It gives rise to the pituitary stalk, the median eminence and the POSTERIOR pituitary.

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5
Q

hypothalamus organized into discrete __

A

hypothalamus organized into discrete nuclei

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6
Q

What are the nuclei of the hypothalamus?

A

a group of similarly functioning neurones

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7
Q

Does anterior pituitary contain many blood vessels?

A

anterior pituitary is highly vascularized: capillary bed in anterior pituitary is connected to capillary bed in median eminence through portal veins

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8
Q

What is the median eminence

A

The median eminence is a part of the hypothalamus from which regulatory hormones are released. It is integral to the hypophyseal portal system, which connects the hypothalamus with the pituitary gland
The median eminence is the structure where secretions of the hypothalamus (releasing and inhibiting regulatory hormones, known as “hypophysiotropic hormones”) collect before entering the portal system emptying into the general circulation.

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9
Q

Where are releasing factors released to by the hypothalamus?

A

Releasing factors are secreted into median eminence that go to pituitary

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10
Q

What is the purpose of the retrograde flow?

A

Retrograde flow of blood allows for –ve feedback from pit. to hypothalamus
some black gets pushed back to hypothalamus so hypothalamic releasing factors can have an impact on the hypothalamus

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11
Q

What is a nerve plexus

A

A nerve plexus is a plexus (branching network) of intersecting nerves

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12
Q

The peptides released at the median eminence enter __

A

The peptides released at the median eminence enter the primary plexus capillaries

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13
Q

anterior vs posterior pituitary in terms of scretions

A

The anterior pituitary receives signalling molecules from the hypothalamus, and in response, synthesizes and secretes seven hormones. The posterior pituitary does not produce any hormones of its own; instead, it stores and secretes two hormones made in the hypothalamus.

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14
Q

Describe the blood supply of median eminence

A

Blood coming from the capillary plexus of the median eminence is carried into a capillary bed in the anterior pituitary by long portal veins.

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15
Q

__ are secreted into median eminence that go to __

A

Releasing factors are secreted into median eminence that go to pituitary

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16
Q

What and where is released by axon terminals of hypothalamic neurones

A

Axon terminals of hypothalamic neurons release hypophysiotropic hormones in the area of the median eminence

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17
Q

What is the blood vessel that carriers hypothalamic hormones to the anterior pituitary?

A

portal vein

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18
Q

What is the blood vessels that transport anterior pituitary hormones to the central blood flow?

A

The pituitary hormones enter the blood stream via the venous capillaries

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19
Q

Where can the receptors for hypothalamic releasing factors be found?

A

Primarily in pituitary, but can also be found through out the body
their role is unknown

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20
Q

what is posterior pituitary made up of?

A

Posterior pituitary is composed of the nerve ending (axons) of neurons whose cell bodies are located in the hypothalamus

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21
Q

How are hormones of posterior pituitary made/released?

A

the nerve ending of hypothalamic hormones that make up the posterior pituitary release hormones into circulation that go out directly to the general circulation
aka from posterior pituitary to circulation
- Hormones (oxytocin and vasopressin) are produced in the cell bodies, packaged into granules which migrate to the ends of the axons located in the posterior pituitary
- Stimulation of neurons in the hypothalamus triggers the release of the hormones from the axon tips located in the posterior pituitary
- The hormones are taken up by capillaries and enter the blood stream

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22
Q

neurotransmitters vs hormones

A

neurotransmitters go from one neurone to other, hormones go from neurones into circulation

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23
Q

What are the roles of SON and PVH

A

supra optic nucleus and paraventricular nucleus release oxytocin and vasopressin directly into the circulation in posterior pituitary

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24
Q

What are projection neurones?

A

projection neurones are neurones that connect one neurone to the other
hypothalamus has both projection and neurosecretory neruoens

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25
What are the 3 main classes of hypothalamic neurones? and their locations
Magnicellular Neuron-Location: SON, PVH Parvicellular Hyposeotropic Neurone. Location: PeVH, PVH, Arc Hyptohalamic Projection Neuron: PVH, LHA, Arc
26
describe Magnicellular Neuron
Magnocellular neurons (MCN) are neuroendocrine cells located in the hypothalamus; they are among the largest cells in the brain, major nuclei- supra optic (SON) nucleus and paraventricular nucleus (PVH) release oxytocin and vasopressin directly into the circulation these are peptide hormones-> stored in vessicles receive their names due to anatomical position these neurones are large compared to other neurones to in NS Kidney, uterus, Mammary gland
27
describe Parvicellular Hyposeotropic Neurone
Parvicellular neurones- produce releasing/trophic hormones; spread amongst various nuclei- located around the 3rd ventricle PVH, PeVH, arcuate nucleus (Arc) Smaller in size their granules are only observed in axonal endings Nerve endings go to the anterior pituitary-> trophic hormones are released by the associated nuclei using this neuron
28
describe Hyptohalamic Projection Neuron
hypothalamic projection neurones are neurones that connect one neurone to the other hypothalamus has both projection and neurosecretory neurones Location: PVH, LHA, Arc
29
Which cell's morphology does pituitary's morphology resemble? What does that mean?
morphology of pituitary cells resembles any of those, who produce a lot of proteins- a lot of ER thus pituitary cells are peptide producing cells
30
What are functions/structures of posterior vs anterior pituitary?
posterior pituitary- collection of axons-> releases hormones made in the hypothalamus anterior pituitary-> receiving inhibiting or stimulating factors from median eminence-> produces hormones itself
31
What are the 2 divisions found in paraventricular nucleus? WHat are the major hormones released by each?
Magnicellular- Oxytocin, vasopressin | Parvicellular- corticotropin releasing hormone (CRH), TRH, vasopressin
32
WHat are the major hormones released by arcuate nucleus (Arc)?
GnRH, GHRH, Melanocortins, prolactin, somatostatin
33
Where does hypothalamus receive signals from?
hypothalamus receives sensory inputs from: - the external environment (e.g., light, nociception, temperature, odorants) and - internal environment (e.g., blood pressure, blood osmolality, blood glucose and hormone levels)
34
Where does hypothalamus send signals to?
anterior pituitary gland, posterior pituitary gland, cerebral cortex, premotor and motor neurons in the brainstem and spinal cord, and parasympathetic and sympathetic preganglionic neurons
35
Define what are Circumventricular organs (CVOs)?
``` Circumventricular organs (CVOs) are structures in the brain characterized by their extensive and highly permeable capillaries, unlike those in the rest of the brain where there exists a blood–brain barrier (BBB) at the capillary level - Exposed to hormones, metabolites and toxins ```
36
Name Circumventricular organs (CVOs)
- organum vasculosum of the lamina terminalis (OVLT) - Subfornical organ (SFO) - Median eminence (ME) - Subcommissural organ (SCO) - Area postrema (AP)
37
Describe Supraoptic and paraventricular nuclei:
- Named after the location of the cell bodies of the neurons - Large neurons (120-200 nm diameter) - Neuron are specific, producing mainly oxytocin or vasopressin - The hormone granules are visible and can be observed traveling down the axons (8 mm/h) - axons end in the pituitary
38
describe Hypothalamic-hypophysiotropic nuclei
Hypothalamic-hypophysiotropic nuclei (PeVH, PVH, Arc) - Located near the wall of the third ventricle vSmaller neurons, hormone granules can only be observed in the axon terminal vNerves terminate in the external layer of the median eminence near the primary plexus
39
__ pituitary receives blood from media eminence
anterior
40
__ pituitary is the collection of hypothalamic nerve endings
posterior
41
What are the 5 types of cells in the anterior pituitary
- corticotroph - thyrotroph - gonadotroph - somatotroph - lactotroph
42
what are the products and targets of corticotroph
ACTH b-lipotropin Target: adrenal gland, adipocytes, melanocytes
43
what are the products and targets of thyrotroph
TSH Target: thyroid gland
44
what are the products and targets of gonadotroph
LH, FSH Target: gonads
45
what are the products and targets of somatotroph
GH | Target: all tissues. liver
46
what are the products and targets of lactotroph
PRL | Target: breast gonads
47
Name basophils and acidophils of the anterior pituitary + their products
Basophils: Thyrotropes →TSH Gonadotropes → LH or FSH Corticotropes→ACTH Acidophils: Somatotropes →GH Lactotropes→ PRL
48
Major functions of TRH
Stimulates the release fo TSH and PRL; | minor stimulation of FSH release
49
Major functions of GnRH
stimulates the release of LH and FSH
50
Major functions of GHRH
stimulates the release of GH
51
Major functions of SMS
inhibits the release of GH; also gastrin, VIP, glucagon, insulin, TSH and PRL
52
Major functions of CRH
stimulates the release of ACTH
53
Major functions of dopamine
inhibits the release of PRL
54
What is the half-life of hypothalamic hormones affecting the anterior pituitary. How is it related to the time of action?
releasing factors have Short half-life in circulation and fast action as they need to act before they decompose
55
What kind of hormones are the hormones of the anterior pituitary
peptide
56
How does feedback control happens in terms of hypothalamic hormones affecting the anterior pituitary
Some feedback control through modulation of receptor numbers | increased amount of releasing factor-> less receptors
57
What is the signalling method for the hypothalamic hormones affecting the anterior pituitary
Post-receptor intracellular signaling by G-proteins - Trophic hormones: Gs⍺ and Gq⍺ proteins. - Inhibitory hormones: Somatostatin and dopamine act via Gi⍺ and other mechanisms.
58
Gq⍺ leads to __
Gq leads to Ca+ release
59
Gs⍺ leads to __
GS leads to cyclic AMP and adenylyl cyclase
60
action of trophic hormones is dependent on the __
action of trophic hormones is dependent on the renewal of the stimulus
61
Why is the renewal of stimulus important in trophic hormone signalling?
when there’s high number of releasing factors, the number of receptors goes down and the signalling goes down in order to get more signalling, more stimulus should also occur- this is achieved by the short life and the fact that releasing factors are released in pulses
62
What is SCN?
The suprachiasmatic nucleus or nuclei (SCN) is a tiny region of the brain in the hypothalamus, situated directly above the optic chiasm. It is responsible for controlling circadian rhythms- circadian pacemaker (“clock”) that controls many physiological functions including pineal the proteins of SCN are expressed at certain times- have their own clock- this clock can be regulated by light and melatonin (external hormone to SCN)
63
What kind of receptors can be found in SCN? WHat are the consequences?
SCN has melatonin Receptors – light and melatonin can reset the clock (other minor factors such as temperature)
64
Apart from having melatonin receptors, how else is SCN and melatonin connected?
SCN can also regulate the production of melatonin
65
How fast does SCN affect the pineal gland, why?
this action of SCN on the pineal gland takes a lot of time- due to long neurones chains of projection neurones (one neurone leading to other and to the other)
66
How is adrenergic receptors connected with the pineal gland?
The adrenergic receptors are the mainstay receptors of pineal gland function. They form the bridge between the circadian controlled release of melatonin production of the pineal gland. which is in part controlled by SCN
67
what kind of receptor is adrenergic receptor?
g-protein
68
Which gland secretes melatonin/ When
pineal melatonin secretion is the highest during darkness, peaking at 12pm, when we are asleep goes down with the light, when we wake up
69
What is the precursor for melatonin
melatonin is made of tryptophan
70
How do humans sense the level of light
humans have no photoreceptors, but a direct nervous connection form SCN to the pineal gland photoreceptors within the retina can lead to SCN which than sends signals to the pineal gland
71
how do melatonin levels change with age?
decrease with age
72
Where are melatonin receptors found. What would that suggest?
not only in SCN, but also throughout the body | thus melatonin affect more than just the circadian rhythm in SCN
73
what are some of the melatonin's functions?
May entrain body’s biological rhythms to the dark-light cycle eg. Core body temperature - Induction of sleep - Depression of reproductive activity, inhibition of ovulation and semen production in some animals –questionable role in humans - Seasonal fluctuations may affect the timing of breeding, migration and hibernation in mammals
74
Adverse side effects of melatonin
- Daytime sleepiness and Hypothermia - Desensitization of melatonin receptors if doses too high - Possible adverse events in those with seizure disorders - Possible interaction with those taking coumadin/warfarin
75
Describe the structure of anterior pituitary hormones
anterior pituitary hormones are peptide hormones; can be made from one chain or 2 separate protein chains coming from 2 different genes
76
Name single peptide chain anterior pituitary hormones
single chain hormones are GH, prolactin and ACTH
77
Name 2 peptide chain anterior pituitary hormones and describe their structure
gonadotropins , LH and FSH are made of 2 protein chains of which alpha chain is common for all 3 each of these 3 have a specific beta chain alpha and beta chains are made from different genes
78
PVH's neurons
magnicellular neuron parvicellular hypophysiotropic neuron hypothalamic projection neuron
79
Arc's neurons
parvicellular hypophysiotropic neuron | hypothalamic projection neuron

kris Endocrinology (17 decks)

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