Endocrine System - Test 1

Follicle Cells

The follicle cells surround a cavity that holds a viscous colloid, a fluid containing a large quantity of dissolved proteins. The follicle cells synthesize a protein called thyroglobulin and secrete it into the colloid of the thyroid follicle. The thyroglobulin molecules contain amino acid tyrosine. The thyroglobulin is combined with iodide ions absorbed from the diet to form the thyroid hormones: T3 (tri-iodothyronine) & T4 (thyroxine). Thyroid hormones have several effects on the body. Between the follicles is a second population of endocrine cells called parafollicular cells, or C (clear) cells. Clear cells produce calcitonin (CT) which lowers blood calcium levels when they are high.

Neurohypophysis

The posterior lobe of the pituitary gland connected to the hypothalamus by the infundibulum; contains the axons of the hypothalamic neurons. Stores and secretes hormones synthesized in the hypothalamus: Antidiuretic hormone (ADH also known as vasopressin) Oxytocin (OXT)

The posterior pituitary is composed of neural tissue. 2 hormones are produced in the hypothalamus but stored in the posterior pituitary. Identify these hormones:

(ADH) Anti-diuretic Hormone & Oxytocin

Actions of Water Soluble Hormone

-Water-soluble hormones cannot diffuse through the cell membrane -these hormones must bind to a surface cell-membrane receptor -the receptor then initiates a secondary messenger within the cell -this activates proteins in the cells that carry out the changes specified by the hormone -receptor is on the inside of the cell -there is a 2nd messenger -after the 2nd messenger there are a series of chemical rxns to get to the nucleus

Actions of Lipid Soluble Hormone

-a steroid hormone directly initiates the production of proteins within target cell -steroid and thyroid hormones easily diffuse through the cell membrane -steroid hormone binds to it receptor in the cytosol, forming a receptor-hormone complex -receptor-hormone complex then enters the nucleus and binds to receptors already bound to DNA -transcription of the gene creates a messenger RNA that is translated into the desired protein within the cytoplasm -moves right into muscle and starts working

Non-polar (lipid soluble) Hormones

-lipid soluble -lipid hormones -steroids are a type of lipid hormone and are made from cholesterol -can get right through the cell membrane -most hormones made from lipids are called steroids, meaning its made from cholesterol -ex: Testosterone non-polar = hydrophobic

Polar (water soluble) Hormones

-water soluble -amino acid & protein hormones -travel easily and quickly -hormones made from proteins & amino acids -ex: Human Growth Hormone (HGH) polar = hydrophilic

Pituitary Gland - Hypophysis

1. Also known as the "master gland" is located within the sella turcica of the sphenoid bone. 2. Connected to the hypothalamus via the infundibulum and a network of capillaries called the hypophyseal portal system. Divided into two lobes: an anterior lobe and a posterior lobe. 3. Neurohypophysis - the posterior lobe of the pituitary gland connected to the hypothalamus by the infundibulum; contains the axons of the hypothalamic neurons. Stores and secretes hormones synthesized in the hypothalamus 4. Adenohypophysis - the anterior lobe of the pituitary gland connected to the hypothalamus by the hypophyseal portal system. Controlled by regulating hormones, called releasing hormones (RH) and inhibiting hormones (IH) from the hypothalamus

Structures of the Endocrine System

1. Thalamus 2. Pineal gland 3. Pituitary gland 4. Thyroid 5. Thymus 6. Adrenal 7. Pancreas 8. Ovaries 9.Testes

Hypothalamus

1. The hypothalamus provides the highest level of endocrine control. it integrates the activities of the nervous system and endocrine system. 2. Hypothalamus accomplishes this integration through three mechanisms

Adrenal hormone responsible for maintaining normal blood sodium levels

Aldosterone

Parathyroid Hormone (PTH) targets

Bones - activates osteoclasts causing calcium and phosphate ions to be released into the blood. Kidneys - promotes activation of vitamin D and increases calcium reabsorption in the kidney tubules. Intestine - increases calcium absorption from food.

Endocrine system and Nervous System are similar yet different: Homeostasis

Both share a common goal: to preserve homeostasis by coordinating and regulating the activities of other cells, tissues, organs, and systems.

Endocrine system and Nervous System are similar yet different: Feedback Control

Both systems are regulated primarily by negative feedback control.

Endocrine system and Nervous System are similar yet different: Chemical Messengers

Both systems rely on the release of chemical messengers that bind to specific receptors on their target cells. Both share many chemical messengers; when released into the bloodstream they are called hormones but when released into a synapse, they are called neurotransmitters.

Best description of a target cell

Cells with a specific receptor that respond to a hormone

During times of stress, elevated levels of _____ often occur.

Cortisol

If a patient was experiencing feeling cold and tired, and weight gain, would you expect their TSH level to be high or low?

High

Factors affecting target cell response.

Hormones must have receptors on their target tissue.

Releasing and Inhibiting hormones only found in the _____

Hypothalamus

What brain structure controls the pituitary gland?

Hypothalamus

Neural Regulation

Hypothalamus - posterior pituitary connection. Posterior Pituitary is neural tissue.

Thyroid Gland

Located in the neck just below the larynx and anterior to the trachea. Divided into a right and left lobe connected by a narrow isthmus. Regulated by TSH from the pituitary gland in negative feedback loop. (hormonal regulation) -secreted to make thyroid hormone The thyroid gland contains large numbers of thyroid follicles. -butterfly shaped gland in neck

The Endocrine Pancreas

Located posterior and inferior to the stomach. Has both and endocrine and exocrine abilities. Pancreatic Islets (also called Islets of Langerhans): endocrine cells that produce hormones. -Alpha Cells: produces glucagon -Beta Cells: produces insulin -Delta Cells: produce somatostatin which inhibits insulin and glucagon secretion and slows the rates of food absorption and enzyme secretion along the digestive tract. Acinar Cells: exocrine cells that produce enzymes and other digestive tract Insulin and glucagon work as antagonists to maintain homeostasis of blood sugar. (humoral regulation)

Thymus Gland

Located posterior to the sternum and between the lungs. Large in infant, increase in size until puberty and then shrinks as the individual continues to age. The major hormonal product of the thymus gland is thymosin which appears to be essential for the normal development of T lymphocytes and the immune response.

Adrenal Gland

Located retroperitoneal and superior to the kidney. Composed of 2 distinct regions: the Adrenal Cortex (outer) and Adrenal Medulla (inner). Adrenal Cortex produces steroid hormones from cholesterol (corticosteroids) and is divided into 3 regions. Adrenal medulla hormones within the body is under stress (neural regulation)

Gonadal Hormones

Ovaries: produce estrogen and progesterone. Testes: secrete testosterone Both of these hormones are regulated by FSH and LH (pituitary) and GnRH (hypothalamus).

Which hormone can induce labor?

Oxytocin

Humoral "in the blood" regulation

Pancreas secretions respond to blood sugar levels. Parathyroid and thyroid respond to blood calcium levels.

Hormones be divided into two groups:

Polar & Non-Polar

What are the two main categories of hormones based on their chemical structure?

Polar & Nonpolar

Nervous system control in the in _______ ______ release hormone

Posterior Pituitary

For any cell to respond to a hormone it must have a ______.

Receptor

Follicle stimulating hormone (FSH or gonadotropin) - and Luteinizing Hormone (LH)

Released in response to gonadotropin-releaseing hormone (GNRH) from the hypothalamus. Each of these target the testes and ovaries and regulate reproductive functions. -go to testes & ovaries -both target ovaries & testes

Parathyroid Gland

Small glands embedded in the posterior surfaces of the thyroid gland. Produce parathyroid hormone (PTH) which increases blood calcium levels when they are toon low. PTH and calcitonin work as antagonists to maintain homeostasis of blood calcium levels.

Thyroid hormones have several effects on the body.

Stimulates red blood cell production in the body: enhanced oxygen delivery. Stimulates the activity of other endocrine tissues. Accelerates the turnover of minerals in bone. Elevates rates of oxygen consumption and energy consumption in cells; increase basal metabolic rate. Increases heart rate and force of contraction resulting in increased blood pressure. Increases sensitivity to sympathetic stimulation. Maintains the normal sensitivity of respiratory centers to changes in oxygen and carbon dioxide concentrations in the blood.

Thyroid Hormones

T3 - Tri-iodothyronine and T4 - thyroxine Parafollicular Cells - Calcitonin -T3 = active hormone of thyroid

Adenohypophysis

The anterior lobe of the pituitary gland connected to the hypothalamus by the hypophyseal portal system. Controlled by regulating hormones, called releasing hormones (RH) and inhibiting hormones (IH) for the hypothalamus: Thyroid stimulating hormone (TSH) Adrenocorticotropic hormone (ACTH or corticotropin) Follicle stimulating hormone (FSH or gonadotropin) - and Luteinizing Hormone (LH) Growth Hormone (GH) Prolactin (PRL)

3 regions of Adrenal Cortex

Zona glomerulosa (outer): releases mineralocorticoids, principally aldosterone, which controls electrolyte balance in the kidneys. Zona fasciculate (middle): produces glucocorticoids such as cortisol and cortisone which influence metabolism of glucose, protein, and fat; controlled by ACTH. Zona reticularis (inner): produces androgens or adrenal sex hormones such as testosterone which influence masculinization.

Paracrine Communication

a cell targets adjacent cells

Autocrine

a cell targets itself

Three Integration Mechanisms from Hypothalamus

a. Contains autonomic centers that exert direct neural control of the endocrine cells of the adrenal medulla. When the sympathetic division is activated, this direct control allows the immediate stimulation of the adrenal gland. b. Hypothalamic neurons synthesize two hormones - ADH & Oxytocin - and transport them along axons within the infundibulum to the posterior lobe of the pituitary for storage and secretion. c. The hypothalamus secretes regulatory hormones that control the secretions of the anterior pituitary gland. These regulatory hormones, called releasing hormones (RH) and inhibiting hormones (IH), flow via a network of fenestrated capillaries called the hypophyseal portal system.

Hormones

chemical messengers released by endocrine cells/glands into blood stream to be transported throughout the body to regulate the metabolic functions and activities of other cells of the body -hormones keep a lot of body function in balance

The __________ of a hormone determines how it acts on a target cell.

chemical structure

Steroid hormones are synthesized from _____.

cholesterol

Hormones are regulated by _________.

feedback mechanisms & hormonal interactions -location of receptor depends on the hormone

Endocrinology

field of medicine that focuses on the treatment of endocrine system disorders

Follicles

hollow spheres lined by a simple cuboidal epithelium called the follicle cells

Hormone control in Anterior Pituitary releases _______

hormones -hormones control release of hormones here

Antidiuretic hormone (ADH also known as vasopressin)

increases water reabsorption within the renal tubules of the kidney. This results in a decrease in water loss from urine. -urine is very concentrated -stops urine -alcohol inhibits -made in hypothalamus and stored in the pituitary

The hypothalamus and pituitary gland control _____

most hormones in the body

When a chemical signal from a neuron is released into a synapse, it is called a _______. When it is released into the bloodstream, it is called a ______.

neurotransmitter hormone

Positive Feedback Systems

physiological response cause an increase in the release of the hormone; rarely used

Negative Feedback Systems

physiological response causes a decrease in the release of the hormone; most commonly used -how most hormone work

Gastrointestinal Tract

possesses cells that produce Secretin, Gastrin, CCK, GIP, VIP, Ghrelin, Galanin, Neuropeptide YS, and many more

Skin

produces cholecalciferol, the inactive form of vitamin D

Hormones can only influence organs that have _____ on their target tissue

receptors

Adipose Tissue

releases leptin following the uptake of glucose and lipids resulting in satiety

Kidney

secretes EPO for red blood cell production and rennin for activation of angiotensin II, a potent vasoconstrictor

Heart

secretes atrial natriuretic peptide (ANP) hat literally means "producing salty urine". ANP inhibits aldosterone release by by the adrenal cortex.

A key determinant of hormone function is whether or not it is __________.

soluble in water

Cortisol

stimulates growth

Growth Hormone (GH)

stimulates growth and in skeletal muscle and bone. Regulated by growth hormone-releasing hormone (GH-RH) and growth hormone-inhibiting hormone (GH-IH) (somatostatin) from the hypothalamus. -help the body grow -goes to a lot of target organs; most obvious is muscle and bone

Prolactin (PRL)

stimulates mammary gland development and the production of milk during pregnancy and during nursing. Regulated by several prolactin-releasing hormones and prolactin-inhibiting hormone (PIH). -stimulates breast milk production

Adrenocorticotropic hormone (ACTH or corticotropin)

stimulates the release of steroid hormones by the adrenal cortex. Released in response to corticotropin-releasing hormone (CRH) from the hypothalamus. -looking @ cortex

Oxytocin (OXT)

stimulates the smooth muscle contractions of the uterus which initiates child birth. After delivery, stimulates the ejection of milk. -milk release & child birth -timing of milk release

Thyroid stimulating hormone (TSH)

targets the thyroid gland; stimulates the thyroid to grow and increase its secretion of the thyroid hormones, T3 & T4. Released in response to thyrotropin-releasing hormone (TRH) from hypothalamus.

Direct Communication

via gap junctions; use ions, small solutes, and other lipid-soluble materials as chemical mediators; effects are usually limited to adjacent cells of the same type that are interconnected by connections -cells connected together

Neural Communication

via synaptic clefts; use neurotransmitters as chemical messenger, effects are limited to very specific areas - target cells must have appropriate receptors -one on one relationship

Endocrine Communication

via the bloodstream; use hormones as chemical mediators; effects are on target cells located at a distance -releases hormone into bloodstream & will travel until it reaches the target cell; target cell is far away

Calcitonin

works by increasing the amount of calcium excreted in urine and increasing the deposition of calcium in bone by stimulating osteoblast activity

Endocrine System

works with the nervous system to control and coordinate all the activities of the body and to maintain homeostasis -everything has to be in balance

Hormonal Regulation

A tropic hormone is a hormone that regulates another endocrine gland

Endocrine system and Nervous System are similar yet different: Endocrine Response

Endocrine system response is slower but longer lasting. -you want it to last a long time

Adrenal Medulla Hormones

Epinephrine (aka adrenaline) - (80%) elevates blood sugar, regulates body during stress or anger; raises blood pressure, heart beat, glycogen breakdown and increases all other sympathetic effects of nervous system. Norepinephrine (aka noradrenaline) - helps maintain blood pressure, and accounts for 20% of the hormones released by the medullary portion of the adrenal gland.

2 types of glands

Exocrine - has ducts Endocrine - no ducts; spits hormones into blood

Anterior Pituitary: Tropic action: 2 go to the gonads

Follicle stimulating hormone (FSH or gonadotropin) & Luteinizing Hormone (LH)

Anterior Pituitary: 2 hormones that have direct effect on body

Growth Hormone (GH) & Prolactin

Organs with secondary endocrine function

Heart Gastrointestinal Tract Kidney Adipose Tissue Skin

A patient has a low TSH level. They have a racing heart rate, can't sleep and are losing weight. What medical problem do you suspect?

Hypothyroid

Insulin and glucagon work as antagonists to maintain homeostasis of blood sugar. (humoral regulation)

Insulin lowers blood glucose levels by enhancing membrane transport of glucose into body cells, converting excess glucose to gylcogen for short term storage (glycogenesis) and into fat for long-term storage in adipocytes. Glucagon raises blood glucose levels by breaking down glycogen into glucose (glycogenolysis), synthesizes glucose from lactic acid and other non-carbohydrate molecules (gluconeogenesis), and releases glucose to the blood by liver cells.

Pineal Gland

Located in the epithalamus region of the brain. The major product is melatonin whose concentrations rise and fall in a diurnal cycle. Levels are the lowest during daylight hours and highest at night. Melatonin appears to maintain the basic circadian rhythms - daily changes in physiological processes that follow a regular day-night pattern.

Anterior Pituitary: Tropic action: 2 go to thyroid & adrenal gland

Thyroid Stimulating Hormone (TSH) & Adrenocorticotropic hormone (ACTH)

Which gland must have iodine for it to make its hormones?

Thyroid gland

A ______ hormone finds its receptors on the cells membrane, where a _____ hormone enters the cell of a target cell.

Water-soluble (polar) Lipid-soluble (nonpolar)

TSH and Thyroid Gland connection

When Thyroid gland doesn't make enough hormones TSH will increase. When Thyroid gland makes too much, TSH will decrease.