Anatomy and Physiology 2.1

Endocrine Glands

Secrete Directly into the blood stream

Exocrine Glands

Secrete to the outside of the body. (digestive tract, sweat glands)

The Endocrine System

Regulates the long term processes of the body

Nervous System

Regulates short term processes

What are the four types of intercellular communication

1. Direct-through gap junctions

2. Paracrine-locally through extracellular fluid

3. Endocrine-through the blood stream

4. Synaptic-Through synapses using the nervous system

Target Cells

The target of a hormone, contains protein receptors

What are the three functions of hormones?

1. Stimulate synthesis of enzymes

2. Increase/decrease the rate of synthesis for an Amino Acid or protein

3. Turn on/off enzymes or membrane channels

Amino Acid Derivatives

Hormones made from modifying amino acids like tyrosine and tryptophan

Peptide Hormones

Short chains of amino acids or glycoproteins

Glycoprotein

An amino acid that has carbs attached to it located on the outside of the cell for recognition purposes

Lipid Derivatives

Hormones made from fats similar to cholesterol. (Eicosanoids, steroids)

Eicosanoids

Leukotrienes, prostaglandins, and thromboxanes. Most are paracrine factors and not hormones. Derived from either Omega 3 or Omega 6 fatty acids.

Leukotrienes

Responsible for the allergy response

Prostaglandins

Responsible for the inflammatory response

Thromboxanes

Responsible for making platelets sticky in order to form clots.

Omega-6 Fatty Acid

Common in the U.S diet, vegetable oils, linocleic, harvested for eicosanoids

Omeg-3 Fatty Acid

Docosahexaenoic, fatty fish like salmon, harvested for eicosanoids.

What is the function of phospholipase and COX I and II

Help to form the eicosanoids

NSAID

Non-steroid Anti-inflammatory drugs, block COX I and II to halt the production of eicosanoids thus preventing an inflammatory response.

Can most hormones cross the plasma membrane?

No, only lipid derived hormones can diffuse through the plasma membrane.

How do hormones get the desired reaction from their target cells?

Through second messengers

What is a second messenger?

The second messenger is what causes the response within a cell using a G-protein.

What are some common second messengers?

Cyclic AMP

Cyclic GMP

Calcium Ions

Humoral stimuli

Change in composition of extracellular fluid that can cause hormone response.

Hormonal stimuli

Arrival or removal of a specific hormone that causes a response

Neural stimuli

Neurons can trigger a hormonal response.

What is the Hypothalamus role in the endocrine system.

The hypothalamus is the main control center of the endocrine system.

How does the hypothalamus control the endocrine system.

1. Secretes regulatory hormones that stimulates the anterior pituitary

2. Manufactures and secretes hormones through the anterior pituitary

3. Controls the release of adrenal hormones neurologically

Pituitary gland (hypophysis)

Hangs inferior to the hypothalamus in the Sella turcica. Is responsible for 9 hormones.

Pars Intermedia

In the middle of the anterior and posterior pituitary (part of the anterior) and in control of melanocyte stimulating hormone

Capillary bed

Where arteries and veins meet up in the thinnest and smallest blood vessels. Where hormones can leave the blood stream.

Why does the anterior pituitary have two capillary beds?

It is a portal system that captures hormones from the hypothalamus in one bed and then stimulates and receives production of hormones in the other bed.

Portal system

When their is more than one capillary bed in within a system.

Releasing Hormones (hypothalamus regulatory)

Stimulate creation of one or more hormones in the anterior pituitary gland

Inhibiting Hormones (regulatory hypothalamus)

Prevent synthesis and secretion of hormones from the anterior pituitary gland.

How many adenohypophysis hormones are there?

7

What are the hypothalamus regulatory horomones?

Thyrotropin, Corticotropin, and Gonadotropin

Thyrotropin

Causes production of thyroid stimulating hormone

Corticotropin

Causes production of adrenocorticotropic hormone

Gonadotropin Releasing Hormone

Causes production of either follicle stimulating hormone or luteinizing hormone depending on pulse frequency

Thyroid Stimulating Hormone

released in response to TRH and acts on the thyroid to produce T3 and T4

Adrenocorticotropic Hormone

Released in response to CRH, acts on the adrenal cortex to stimulate the release of glucocorticoids (cortisol).

Prolactin

Released in response to pregnancy hormones and suckling, and acts on mammary glands to produce milk.

Growth Hormone

released in response to Growth hormone releasing hormone, acts on the liver to stimulate the release of hormones that cause many cells in the body to synthesize proteins and grow.

Somatomedins and insulin like growth factors

Released by the liver in response to growth hormone

Is there a different role of growth hormone between children and adults?

Yes, it stimulates growth in children and is responsible for maintenance in adults.

Follicle stimulating Hormone

Released in response to GnRH, acts on cells in gonads to cause maturation of germ cells

Luteinizing Hormone

Released in response to GnRH, acts on cells in the gonads to cause ovulation in females and testosterone production in males.

Melanocyte Stimulating Hormone

Secreted from pars intermedia in fetal development, young children, and some pregnant women.

What is the other source of stimulation to melanocytes besides the pituitary

Sun exposure

Posterior Pituitary lobe Neurohypophysis

Produces and secretes ADH and Oxytocin

Anti-diuretic hormone

Released in response to increased osmolarity, concentration, and pressure of blood, acts on cells of kidneys and vasculature to retain water in kidneys and raise blood pressure.

Diabetes Insipidus

Inability to produce ADH

Oxytocin

Released in response to pregnancy, breastfeeding, and being close to loved one, acts on uterus to cause contractions, mammary glands to produce milk, and brain to warm feelings.

Pineal Gland

Lies in the epithalamus and secretes melatonin

Melatonin

A.A derived horomone that slows reproduction, regulates circadian rhythms, and protects from free radicals in the brain.

Thyroid Gland

Lies anterior and inferior to the thyroid cartilage, and consists of two lobes connected by an isthmus. T3, T4, and calcitonin

Follicle Cells

Spherical structures of simple cuboidal epithelium that produce T3 and T4

Colloid

A pool of thyroglobulin that stores T3 and T4

T4 (Thyroxine) (tetraiodothyronine)

Contains 4 iodine hormones and controls calorigenic effect, heart rate, and O2 consumption.

Thyroglobulin

A molecule that is secreted into the colloid by the follicle cells. It is basically T3 and T4 that just needs a little digesting.

T3 (Triiodothyronine

Contains three iodine ions and controls calorigenic effect.

Thyroid Hormone Production

Tyrosine and Iodide ions, thyroglobulin produced by follicle cells through transcription and translation.

Where and how are Iodine ions taken up

On the basal surface through the Na+/I- symporter

Thyroid Peroxidase

Binds iodine to tyrosine molecules in thyroglobulin to produce T3 and T4

How is T3 and T4 separated from thyroglobulin

Thyroglobulin is taken up by follicle cells where it is ingested by a lysosome ingested by a lysosome to form T3 and T4.

How does most of T3 and T4 circulate through the blood stream

They are bound to plasma protein carriers

Thyroid Binding Globulins (TBG)

The plasma protein that 75% of T3 and T4 bind to for transport

Thyroid Stimulating Hormones

Activates key enzymes in follicular cells to stimulate production and secretion of T3 and T4

Thyroid Hormones

Act on almost all cells in the body and don’t use secondary messengers.

Hypothyroidism

Caused by an inadequate amount of iodine

What is the main source of iodine in the U.S diet.

Iodized salt

Hashimoto’s Thyroiditis

The body produces antibodies against follicular cells

What is the purpose of radioactive iodine, and what can be done to protect against it?

It can be used to highlight the thyroid gland for medical imaging. Potassium Iodide can be taken to protect against a radioactive fallout.

C Cells (Clear) (Parafollicular cells)

Produce Calcitonin

Calcitonin

Released in response to increased Ca in the blood. Reduces osteoclast activity. Increases osteoblast activity, and stimulates Ca extraction by the kidneys.

Does calcitonin have the same effect on adults as children?

Yes, but in a different way. Calcitonin cannot cause osteoblast to increase activity in adults like it can in children. (More calcium will be peed out instead)

Parathyroid Hormone

Increases Osteoclasts, inhibits osteoblasts, enhances absorption of Ca at kidneys, and stimulates formation/secretion of calcitriol at kidneys.

Suprarenal Cortex

Yellow in color (lipids and cholesterol) and manufactures steroid hormones like cortisol, aldosterone, and testosterone.

Suprarenal medulla

Controlled by sympathetic division of autonomic nervous system and produces epinephrine (75-80%) and norepinephrine (20-25%).

Zona Glomerulosa (Cortex superior layer)

Mineralocorticoids like Aldosterone

Aldosterone

Increases sodium conservation at kidneys, sweat glands, salivary glands, and pancreas. Stimulated from drop in blood Na+, volume, or pressure. Or a rise in K+

Zona Fasciculata (middle layer)

Glucocorticoids (cortisol)

Cortisol

Secreted in response to CRH and ACTH. Has an anti-inflammatory effect on immune system, stimulates gluconeogenesis, and glycogen production. Releases fatty acids.

Long Term Effects of Cortisol

Inhibits immune function, bone formation, and muscle weakness.

Where are the receptors for Cortisol

The receptors are inside the cell. Cortisol diffuses through the plasma membrane. (Steroid Hormone)

Zona Reticularis (Deepest layer)

Responsible for androgens

Testosterone

An androgen that are sources of testosterone for females. Muscle mass, blood cell formation, and libido.

Is adrenal testosterone important in males?

No they get most of their testosterone from the gonads.

Epinephrine/norepinephrine

A.A (tyrosine) derived hormones released in low levels until neural stimuli causes a release in large levels (fight or flight response)

What are the effects of flight or flight response?

Increased heart rate, blood pressure, blood flow to skeletal muscles, and dilation of airways. Stimulation of breakdown of glycogen and stored fats.

How do epinephrine and norepinephrine cause different affects throughout the body?

There are two receptors for these hormones. Alpha and Beta adrenergic (G-Protein) receptors.

Does the pancreas have endocrine or exocrine cells?

Both

Pancreatic Islets

Endocrine cells that produce glucagon and insulin through alpha and beta cells.

Alpha Cells

Produce Glucagon

Beta Cells

Produce Insulin

Delta and F Cells

Produce hormones that decrease alpha and beta cell function.

What is the normal blood glucose level?

70/110 mg/dl

Glucagon

Increases blood glucose levels by breaking down glycogen in muscles and liver and triglycerides in adipose. Stimulates gluconeogenesis.

Insulin

Drops blood glucose by accelerating glucose uptake and utilization. Stimulates glycogen formation, A.A absorption, and triglyceride formation.