Exam 1 - Hypothalamic-Pituitary Target Tissue Axis Flashcards

1
Q

What are the alternate names for the anterior and posterior pituitary? What types of tissue are they composed of and how do hormones reach these areas from the hypothalamus?

A

anterior pituitary - adenohypophysis, glandular tissue, conencted by the hypothalamic-hypophyseal portal system

posterior pituitary - neurohypophysis, neural tissue, connected by neurosecretory neurons

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2
Q

What structure connects the pituitary gland to the hypothalamus?

A

infundibular stalk (which contains nerves and blood vessels)

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3
Q

What types of cells compose the anterior pituitary and what hormones do they produce?

A

thyrotrophs - thyroid stimulating hormone

gonadotroph - luteinizing hormone and follicle stimulating hormone

corticitroph - adenocorticotropic hormone

somatotroph - growth hormone

lactotroph - prolactin

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4
Q

How are the 5 types of cells organized in the anterior pituitary?

A

they aggregate in certain regions but are interspersed among one another

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5
Q

All anterior pituitary hormones are —, some are ——, and they are organized into # ——- based on their structure.

A

peptides/proteins

glycosylated

3 families

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6
Q

What are the three families of AP hormones?

A

somatomammotropins, glycoproteins, and pro-opiomelanocortins (POMC)

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7
Q

What defines the somatomammotropins and what AP hormones are in this family?

A

protein hormones

GH (growth hormone) and PRL (prolactin)

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8
Q

What defines the glycoproteins and what AP hormones are in this family?

A

a and B protein subunits plus carbohydrate moieties
The a subunit is identical for all AP glycoproteins while the B subunit confers specificity
The carbohydrate moiety increases half life and biological activity.

FSH (follicle stimulating hormone) and LH (luteinizing hormone) and TSH (thyroid stimulating hormone)

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9
Q

What defines pro-opiomelanocortins (POMC) and what AP hormones are in this family?

A

all derived from POMC, a large precursor protein

ACTH (adrenocorticotropic hormone)

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10
Q

What does growth hormone (GH) do?

A

stimulates growth (via insulin-like growth factor IGF-1) and affects metabolism

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11
Q

What does prolactin (PRL) do?

A

stimulate milk synthesis and secretion during lactation

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12
Q

What does follicle stimulating hormone (FSH) do?

A

stimulate follicular growth and estrogen production in ovaries, as well as regulating spermatogenesis in the testes

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13
Q

What does luteinizing hormone (LH) do?

A

regulate estrogen and progesterone production in ovaries and luteinization of the follicle, as well as regulates testosterone production in the testes

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14
Q

What are LH and FSH collectively called?

A

gonadotropic hormones

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15
Q

What does thyroid stimulating hormone (TSH) do?

A

stimulate synthesis and secretion of thyroid hormones (T3 and T4) by the thyroid gland

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16
Q

What does adrenocorticotropic hormone (ACTH) do?

A

stimulate synthesis and secretion of cortisol and DHEA (a weak androgen) by the adrenal cortex

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17
Q

Describe the biosynthesis of hormones (locations in the cell)

A

synthesized in the endoplasmic reticulum

modified in the Golgi apparatus

stored in vesicles until needed

contents released from vesicles when cell is stimulated

18
Q

How is the output of the AP regulated by the hypothalamus?

A

in the hypothalamus, neurosecretory neurons secrete releasing and inhibiting hormones into the median eminence

They are carried to the AP by the portal vessels, where they alter the activity (both synthesis and secretion) of the cells in the AP

19
Q

What are the releasing hormones and what do they each control?

A

GHRH (growth hormone releasing hormone) - GH

TRH (thyrotropin releasing hormone) - TSH

GnRH (gonadotropin releasing hormone) - LH and FSH

CRH (corticotropin releasing hormone) - ACTH

20
Q

All releasing hormones are….

A

peptides

21
Q

What are the inhibiting hormones? Describe them and what they each control.

A

GHIH (growth hormone inhibiting hormone)
- peptide
- inhibit GH

PIH (prolactin inhibiting hormone/dopamine)
- catecholamine
- inhibit PRL (the only regulator of PRL)

22
Q

What AP hormone does not have an associated releasing hormone? How is it controlled?

A

PRL, only inhibited by PIH

23
Q

Where are all neurohormones created, transported, and stored? When are they released?

A

synthesized in the cell body
transported along the axon
stored in the axon terminal
released when the neuron is stimulated

24
Q

What is a hypothalamic nucleus?

A

a region of the hypothalamus containing cell bodies of neurons secreting a neurohormone

25
Q

What are the 5 hypothalamic nuclei we need to know?

A

paraventricular nucleus, preoptic area, supraoptic nucleus, arcuate nucleus, and ventromedial nucleus

26
Q

What is produced in the paraventricular nucleus?

A

TRH, CRH, OT, and ADH/VP

27
Q

What is the produced in the preoptic area?

A

GnRH

28
Q

What is produced in the supraoptic nucleus?

A

OT and ADH/VP

29
Q

What is produced in the arcuate nucleus?

A

GHRH, GnRH, GHIH, and PIH

30
Q

What is produced in the ventromedial nucleus?

A

GHRH and GHIH

31
Q

What hormones are produced in more than one area? Where are they each produced?

A

OT and ADH/VP - paraventricular and supraoptic

GnRH - preoptic and arcuate

GHRH and GHIH - ventromedial and arcuate

32
Q

Describe how the hypothalamus acts as a central integrator in the case of kisspeptin neurons.

A

info from many systems inside and outside the body send signals to the KiSS neurons
KiSS neurons send signals to the GnRH neurons in the arcuate nucleus of the hypothalamus, which then release GnRH
GnRH causes AP to release FSH and LH causing many effects.

33
Q

What are the 4 types of cellular communication, and give a brief description.

A

autocrine - hormone binds to receptors on the cell they were released from

paracrine - hormone binds to receptors on nearby cells (same tissue)

endocrine - hormone moves through the bloodstream and binds to receptors on a different tissue

neurocrine - hormones are released from an axon, move through the bloodstream, and bind to a receptor on a different tissue

34
Q

What is a tropic hormone?

A

primary function is to regulate hormone secretion of another endocrine gland (regulate release of another hormone)

35
Q

What is a non-tropic hormone?

A

primary effect is on non-endocrine target tissues (regulate some physiological function/response)

36
Q

What are negative and positive feedback loops?

A

negative - response of the target cell inhibits the initial stimulus , maintaining a system within tightly controlled limits

positive - response of target cell enhances the initial stimulus, driving the system away from equilibrium

37
Q

What is a long loop vs. a short loop vs. and ultra short loop?

A

long loop - hormone produced by the target tissue feeds back to the hypothalamus

short loop - tropic hormone produced by the AP feeds back to the hypothalamus

ultra short loop - tropic hormone produced by the AP feeds back to the AP

38
Q

What hormones are synthesized by the posterior pituitary? What hormones are released?

A

none are synthesized, but oxytocin (OT) and vasopressin (VP or ADH) are released

39
Q

How are hormones secreted by the posterior pituitary?

A

neurosecretory neuron cell bodies in the hypothalamus make neurohormones that are carried down axons to the posterior pituitary

the posterior pituitary stores the neurohormones until they are released

40
Q

What does oxytocin do?

A

stimulate smooth muscle contraction in breast myoepithelial cells during lactation for milk ejection and uterine myometrium during labor

41
Q

What does ADH/VP (antidiuretic hormone/vasopressin) do?

A

stimulates water reabsorption by the kidney and arteriole constriction

42
Q

What regulates output of the posterior pituitary?

A

neuroendocrine reflex (positive feedback loop)