Quiz 3 Endocrine Flashcards by Carley Hernandez

Hormones

Blood-borne chemical messengers that affect target cells anatomically distant from the secreting cell

Regulates: Growth and development
Metabolism
Sexual function
Reproduction
Mood stability

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Hormones are classified by

Action - the effect they have (insulin lowers glucose)

Source - Anterior or posterior pituitary

Chemical structure

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Hormones are categorized by chemical composition

Steroids - androgens glucocorticoids, thyroid (lipids)

Proteins/polypeptides - Insulin, growth hormone (water)

Amines/amino acids - epinephrine (water)

Fatty acid derivatives - prostaglandins

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Water soluble hormones

Bind to cell surface receptors

Peptides (small proteins) majority of endocrine hormones

Easily transported in the bloodstream

ACTH FSH LH, Growth Hormone, TSH PTH

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Lipid Soluble Hormones

Carried in circulation by transport proteins (globulin) poorly soluble

Activate intracellular receptors

Thyroid hormones (T3, T4) with iodine attached

Steroids - derived from cholesterol

Hormone detaches at the site of the target cell

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Mechanism of Water Hormones with Cell Membrane Receptors

Hormones exert their action by binding to target cell receptor proteins

Water-soluble hormones have a hormone-binding site located on the external portion of a specific cell surface receptor

Once binding takes place, receptor protein conveys a signal to the interior of the cell to produce a response

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Amplification of Hormone Activity

Why you can have a very small amount of circulating protein and it can cause a tremendous effect on the body.

Progressively larger numbers of chemical reactions occur at each step, resulting in the activation of numerous G proteins

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Mechanisms of Lipid Hormone Action

Steroid (lipid) hormones diffuse easily through the lipid bilayer of the cell membrane; cell membrane carriers transport thyroid hormones

Thyroid and steroid receptors located in the cytoplasm or in the nucleus of the target cell

Once inside the cell lipid hormones have to go through gene expression to have the effect amplified.

Lipid acts slower than water-soluble bc of the multiple steps and gene expression that has to take place before amplification can take place.

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Hormone Synthesis - Water soluble

Peptide hormones are contained within the bilayer of the vesicles and stored until a trigger results in the exocytosis of the hormone into the extracellular space

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Hormone Synthesis - Lipid Soluble

Steroid (Lipid) Hormones are formed on-demand from cholesterol that is stored in the cell or retrieved from the circulating lipoproteins.

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Hormone Synthesis - Thyroid Hormone

Thyroid hormones (lipid-soluble) are formed on demand but are trapped attached to thyroglobulin and sit and wait until they are told its time to be released by the hypothalamus or anterior pituitary

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Factors affecting hormone secretions

Feeding-fasting cycle

Light dark cycle

Sleep-wake cycle

24 hour (circadian cycle)

Longer cycles (28-day menstrual cycle)

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Anterior pituitary gland hormones are regulated

by the hypothalamus

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When do you measure cortisol for testing

First thing in the morning when its at the highest

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Explain Negative feedback control

The body says it need so much of a hormone the body reacts to it and it sends a signal back to the anterior pituitary and hypothalamus that fx at a good level.

If we don’t need as much hormones it will send a message back that to the anterior pituitary to slow down production

If deficient in hormone sends signal to anterior pituitary and hypothalamus that we need more

How we keep hormone level fx and at level we want

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Hormone Metabolism/Excretion

Water Soluble

Lipid Soluble

Water-soluble hormones - Finds their way out in urine

Lipid- soluble hormones are bound to plasma proteins and stored in adipose tissue so they remain in circulation for longer periods of time

Metabolized by kidney and liver; degraded by target cell after binding to receptors

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Half life of a hormone

Duration of hormone activity in circulation expressed in minutes, hours, or days

its the time for a hormone to reach one half of its original concentration in the blood and is influenced by the rate uptake by cells, degradation, and excretion

Lipids usually have a longer half life

Heavier people with more adipose tissue may hold onto hormones a lot longer than someone with no adipose tissue

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Pharmacologic Hormone Concentrations

Physiologic hormone concentrations

Physiologic hormones are extremely low due to amplification

Pharmacologic levels are much higher

Tissue response to pharmacologic hormone concentrations may be significantly different from physiologic levels

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Regulation of Receptor Responses

What determines the ability of a cell to respond to a particular hormone

Cell response to a hormone depends on the presence of specific receptors on very specific cells

for that hormone on the cell called the target cells

A cell can change how it wants to respond to a hormone by changing the # of receptors or an affinity for the hormones

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Affinity

The degree of “tightness” or the hormone receptor bond or the inclination of the hormone to remain bound to the receptor

i.e. Old key locks you put key in a jiggle it around present-day locks have a high affinity with tight locks only fitting the intended key

When you have a high affinity you don’t need as much of the hormone you can use a very small amount

Specificity

The “fit” of a hormone into a receptor binding pocket

Cross specificity

One receptor site will respond to two or more different hormones.

May occur between hormones

Example is growth hormone and prolactin both can bind to a prolactin receptor so if growth hormone take up all the receptors their won’t be any for prolactin

Down regulation

Cells have been exposed to a high concentration of a hormone so the body to protect itself decreased the # of receptor sites available, so it doesn’t have excessive activity

example: insulin receptors

Chronic high glucose levels so the body is putting out a lot of insulin trying to fix the level so the body shuts down insulin receptor cells. This is how insulin resistance occurs

Up regulation

low level of hormone then we need more of it so the body increases the # of receptors to it

Ex: Oxytocin (labor and delivery)

Hormone Permissiveness

the hormone’s ability to increase the number of receptors for other hormones creates a chain of events

Hypothalamic-Pituitary Axis

Hypothalamus secretes releasing and inhibiting hormones and it regulates what the pituitary gland does. It connects the nervous and endocrine systems

Pituitary gland what does it do and where is it located

The pituitary gland is located at the base of the brain and controls hormones.

Anterior and Posterior pituitary gland

Posterior gland is connected to the hypothalamus by the pituitary stalk

When the hypothalamus wants to communicate with the Anterior pituitary it has to put hormones out into the system for pituitary gland to receive b/c there is not a direct connection

Functions as a intermediary between the hypothalamus and the target organs

Hormones secreted by the

ANTERIOR PITUITARY

Somoatotropes secrete GH

Gonadotropes secrete LH/FSH

Thyrotropes secrete ACTH

Lactropes secrete prolactin (PRL)

Hormones secreted by the

POSTERIOR PITUITARY

ADH (vasopressin)

Oxytocin

Functions of the Pancreas

Exocrine secretions for digestion
Endocrine functions

Islet of Langerhans

Types of cells

Alpha cells – secrete glucagon
- Glucagon (opposite of insulin) tells the liver to break down glycogen stores into glucose - raises sugar
Beta cells – secrete insulin and amylin
- Insulin works with amylin to control glucose
Delta cells – secrete somatostatin and gastrin
- Somatostatin inhibits growth hormone
- Gastrin stimulates the stomach to release gastric acid

Glycolysis

Breakdown of glucose for energy

Glycogenesis

Excess circulating glucose is converted into glycogen and

stored in the liver and muscle cells

Opposite of Glycogenolysis

Glycogenolysis

Breakdown of glycogen into glucose for energy

Opposite of Glycogenesis

Gluconeogenesis

No sugar in system and glycogen used up so the body gets sugar from other non sugar substances

Where do we get energy how is it metabolized

Energy requirements are met by glucose and fats

Glucose is produced from glucose stores or glycogen in liver primarily it is coming from the bloodstream from the GI tract and liver

Explain Glucose Metabolism

Glucose is stimulus for insulin release from vesicles. Insulin then binds to its receptor on insulin-sensitive cells (not all cells do this) and it triggers glucose uptake

Insulin needs access to insulin receptor cells to allow it to function

What are Incretins and what is their function?

Incretins are released after a meal to stimulate insulin release and inhibit glucagon release

Incretins slow gastric emptying and decrease appetite

Dipeptidyl Peptidase 4 (DPP-4) causes breakdown of the Incretins

There is a new diabetic med that inhibits the breakdown of DPP-4 allowing the incretins to work and natural glucose metabolism

What happens after you eat in relation to glucose metabolism

Glucose ingested food causes a brief rise in insulin release (first phase).
Continued glucose causes increased insulin secretion (second phase)
Ingestion of nutrients stimulates release of glucose–dependent insulinotropic polypeptide (GIP) and glucagon-like peptide 1 (GLP-1) from cells in the gut.(Incretins stimulates insulin release and inhibits glucagon to lower sugar)
Effect on blood glucose known as incretin effect

Thyroid Gland follicles

Thyroxine – T4
Triiodothyronine – T3
Thyrocalcitonin – Calcitonin (regulates calcium levels)

What does the thyroid gland do

Controls growth and metabolism. Hypothalamus releases thyrotropin-releasing hormone (TRH) which stimulates anterior pituitary to release thyroid-stimulating hormone (TSH) which stimulates the thyroid to release T3 and T4

Only 10% of T3 is produced in the thyroid - T4 converts to T3 in body tissues

Iodine needed to synthesize the T3 and T4

Thyroid hormones are bound to thyroglobulin (protein) until they are released

How does the hypothalamus function in relation to the thyroid

Hypothalamus releases thyrotropin-releasing hormone (TRH) which stimulates anterior pituitary to release thyroid-stimulating hormone (TSH) which stimulates the thyroid to release T3 and T4
Only 10% of T3 is produced in thyroid – T4 converts to T3 in body tissues
Iodine needed to synthesize the T3 and T4
Thyroid hormones are bound to thyroglobulin (protein) until they are released

Parathyroid Gland

4 glands
Located behind the thyroid glands
Secrete parathyroid hormone (PTH)

_{<strong>•PTH – regulates calcium</strong>}

Can cause calcium release from bones when serum calcium levels are low (makes bones weak)
Can increase calcium absorption from the GI tract and in the renal system
PTH stimulates Vitamin D which is needed for calcium GI absorption

Adrenal Gland

Located on top of each kidney

Has inner medulla and outer cortex
Hypothalamus regulates function

The Adrenal Glands

Medulla Produces

Epinephrine

Norepinephrine

Adrenal Gland

Cortex Produces

Salt sugar and sex tells you what comes out of the

Adrenal Cortex

Mineralocorticoids - Aldosterone (salt and water)
Glucocorticoids – Cortisol (sugar)
Gnadocorticoids - Androgens and Estrogens (sex)

Steroid Hormones

MINERALCORTICOIDS

ALDOSTERONE

Maintain normal salt and water balance by promoting sodium retention and potassium excretion at the distal renal tubules
Aldosterone secretion regulated primarily by the renin-angiotensin system associated with the juxtaglomerular cells of the kidney
Released in response to low blood pressure, reduced renal perfusion and a high serum potassium level

STEROID HORMONES

GLUCOCORTICOIDS

Primary effect on glucose metabolism

Oppose the effects of insulin and raise blood glucose levels by decreasing glucose uptake by many body cells (decreased glycogenesis) and increasing glucose synthesis in the liver from glycogen and amino acid and glycerol substrates in fat stores (glycogenolysis, gluconeogenesis)

Adrenocorticotropic Hormone (ACTH)

Produced by corticotropes in the anterior pituitary in response to hypothalamic corticotropin-releasing hormone (CRH)

Binds to receptors on cells in the adrenal cortex and stimulates the production of cortisol and adrenal androgens

CRH and ACTH have a significant diurnal pattern, with a peak on wakening in the morning and a valley in the evening.

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Quiz 3 Endocrine Flashcards

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