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Physiology > Physiology Block 3 Week 14 07 Intro to Pituitary > Flashcards

Physiology Block 3 Week 14 07 Intro to Pituitary Flashcards

1
Q

Classic Hormone Groups

A

Tyrosine Derivatives
Steroids
Peptides/proteins

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2
Q

The class of hormone determines the mechanism of?

A

Synthesis and Secretion

Transport in the plasma compartment (protein binding)

Mechanisms and speed of onset of action (membrane receptors vs intracellular receptors)

Metabolism (half-life and metabolic clearance rate)

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3
Q

What are hormones?

A

Chemicals that are released through ductless glands and affect somewhere

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4
Q

Thyroid Hormones

% bound to plasma proteins
Half-life
Clearance

A

VERY high % binding to plasma proteins (99.95%)

Biologically active

VERY long half-lives
–Only free (dissolved) hormone can bind to receptor

LOW metabolic clearance

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5
Q

Steroid Hormones

% bound to plasma proteins
Half-life
Clearance

A

HIGH % binding to plasma proteins (94%)

LONG Half-life

Low Metabolic Clearance

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6
Q

Peptide and Protein Hormones

% bound to plasma proteins
Half-life
Clearance

A

ONLY circulate free form

SHORT Half-life

HIGH metabolic clearance

Exception = insulin-like growth factors

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7
Q

Endocrine Rhythms

A

Circadian
Ultradian
Stimulus-Induced
Seasonal

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8
Q

Circadian Endocrine Rhythm

A

Around the 24 hour clock

Test testosterone at morning when should be the highest

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9
Q

Ultradian Endocrine Rhythm

A

High frequency and Regular Bursts

Pulsatility of Luteinizing Hormone

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10
Q

Stimulus-Induced Endocrine Rhythm

A

Ex. Breast feeding is stimulus for increased prolactin

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11
Q

Seasonal Endocrine Rhythms

A

Ex. Vitamin D

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12
Q

Negative Feedback of Glucagon and Glucose

A

Glucagon is to prevent hypoglycemia

The alpha cells of the endocrine pancreas (produces glucagon) have glucose sensors that detect a decrease in EC glucose

  • ->increases glucagon release
  • ->stimulates hepatic gluconeogenesis and glycogenolysis
  • ->increased release of glucose form the liver restores blood glucose

Increased blood glucose inhibits alpha cells from producing glucagon

Parallel to Insulin

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13
Q

Negative Feedback of Insulin and Glucose

A

Insulin prevents hyperglycemia

An increase in blood glucose is sensed by the beta-cells of the endocrine pancreas

  • ->increases insulin release
  • ->insulin inhibits glucose release from the liver

Parallel to Glucagon

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14
Q

G-Protein Coupled Receptors Mechanism

A

Hormone activates the receptor

Inactive alpha, beta, and gamma G protein complex associates with the receptor and is activated
–exchanges GDP for GTP

Alpha unit dissociates and interacts with membrane-bound target proteins (Adenylyl cyclase)

Generation of second messengers!

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15
Q

G-Protein coupled generation of second messengers

A

FAST–Epi or ACTH

Cyclic adenosine monophasphate (cAMP) released in exchange for ATP

cAMP activates cAMP dependent Protein Kinase (PKA)

Phosphorylates proteins leading to a cellular response

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16
Q

G-Protein coupled to PLC, IP3, DAG second messenger system

A

Peptide hormone binds to receptor

Activates G-protein

Activates Phospholipase C

Splits PIP2 into DAG and IP3

IP3 exerts function on endoplasmic reticulum

  • release of Ca2+ leads to cellular response
  • release of inactive enzyme

DAG moves into cytoplasm and activates Protein Kinase C (PKC)

Phosphorylates inactive enzyme leading to cellular response

17
Q

Lipophilic Hormones

A

SLOW–Cortisol

Steroids with intracellular receptors in target cells

Hormone binds to receptor in cytoplasm or in nucleus

Hormone-Receptor complex binds to hormone response element (promoter) on DNA
–Either activates or inhibits gene transcription, formation of mRNA, and protein synthesis

18
Q

Mechanism of action of Thyroid Hormones

A

Nuclear Receptor

Thyroxine (T4) secreted from thyroid gland

Activated to T3 (by monodeiodinase) in cytosol and binds intracellular receptor, which binds promotoer
–allows a target tissue to regulate how much thyroid hormone action to which it is exposed

Ex. Heart can express the enzyme to convert T4 to T3

Ex. Inhibitors to prevent conversion as well

19
Q

Pituitary Gland

A

Anterior Pituitary:

  • Pars distalis
  • Adenohypophysis

Pars Intermedia

Posterior Pituitary
-produces anti-diuretic hormone (vasopressin) and oxytocin

Hangs off base of brain by hypophysial stalk (infundibulum)

Neurons with cell bodies in the hypothalamus synthesize releasing or inhibitory (hypophysioTROPIC) factors and release them from short axons that terminate on capillaries in the median eminence

Forms portal veins that drain onto the anterior pituitary carrying hypophysiotropic factors

These factors stimulate or inhibit the release of anterior pituitary hormones that exit the pituitary via veins that drain into the petrosal sinuses and then jugular veins

20
Q

Classes of Anterior Pituitary Hormones

A

Glycoproteins
Growth Hormone/Prolactin
POMC

21
Q

Gylcoproteins

A

Anterior Pituitary Hormone

TSH, FSH, LH–stimulate synthesis

Identical alpha subunits
Beta subunit conveys receptor binding specificity

22
Q

Growth Hormones/Prolactin

A

Anterior Pituitary Hormone

Promotes growth in stature and mass
Milk secretion

Amino Acid sequence homology

23
Q

POMC

A

Anterior Pituitary Hormone

POMC gene produces a peptide (POMC) that is post-translationally modified to ACTH

Promotes synthesis and secretion of adrenal cortical hormones

24
Q

Hypophysiotropic Hormones

A

Hypothalamic releasing or inhibiting hormones

Corticotropin Releasing Hormone
Gonadotropin Releasing Hormone
Growth Hormone Releasing Hormone
****Somatotropin Releasing-Inhibiting Factor (inhibits GH secretion)
Prolactin Stimulating Factor
***Prolactin Inhibiting Factor--Dopamine
Thyrotropin Releasing Hormone
25
Q

Anterior Pituitary

A

Master gland

Controls:

  • thyroid function (TSH)
  • pre-pubertal growth
  • adrenal cortex (ACTH)–release of adrenocortical hormones, gonadotropins (FSH and LH), and prolactin
26
Q

Pituitary Descending Stimulation

A

Input to hypothalamus (environmental factors) increases or dec hypophysiotropic factor release

Hyopphysiotropic factor stimulates anterior pituitary to produce a tropic hormone

Stimulates a target gland to produce a final factor

27
Q

Pituitary Control Feedback Loops

A

Long-Loop:
Target gland produces Target Gland Hormone
-serves as negative feedback on pituitary or hypothalamus

Ex. Cortisol increases and will shut off ACTH release

Short-Loop:
Pituitary hormone (tropic hormone) serves as negative feedback on hypothalamus
28
Q

Trophic Effect

A

SLOW–growth effect over days and weeks

Nurturing/growth promoting effect

If ACTH high for a long time, stimulates adrenal growth and hypertrophy

If Low ACTH leads to adrenal atrophy

29
Q

Tropic Effect

A

FAST–Immediate response

Acute stimulatory effects

ACTH stimulates cortisol release within minutes

30
Q

Which of the following has the longest half-life?

Growth Hormone
Arginine Vasopressin
Testosterone
Angiotensin 2

A

Testosterone

Steroid Hormone, binds plasma protein

31
Q

Want increase in Prolactin

A

Pregnancy, pituitary gets big, lots of prolactin produced

Dopamine inhibits prolactin–want to dec dopamine

Suckling inhibits the nerves in the hypothalamus that make dopamine
Dopamine goes down, releasing lactotroph, allowing prolactin to inc

32
Q

Hypopituitarism

A

Too little pituitary function (anterior)

33
Q

How do you treat a pituitary tumor?

A

Pituitary tumors express receptors for hyphysiotropic hormone that controls it

Give dopamine agonist–shrinks the tumor

34
Q

Which of the following will lead to a decrease in prolactin secretion?

Dopamine Agonist
Dopamine Antagonist
Post-Partum Nursing
Pregnancy

A

Dopamine Agonist turns on dopamine, inhibiting lactotroph release of prolactin

Physiology (20 decks)

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