BIOD 151: Module 6 - The Endocrine System

What two major hormones do the axons ending in the posterior pituitary store?

Antidiuretic hormone (ADH) and oxytocin

Posterior Pituitary

Connected to the hypothalamus by means of a stalk like structure. Hormones pass from the hypothalamus through axons that terminate here that store two major hormones: ADH and oxytocin.

Endocrine Glands

Ductless glands that secrete their contents directly into the bloodstream for distribution throughout the body.

What are the two types of glands?

Endocrine and exocrine glands

Positive Feedback System

Enhances or increases the amount of hormone that is regulated to maintain homeostasis.

Goiter

Enlarged thyroid gland that occurs when iodine is acting in the diet

Where is the pancreas located?

Long organ that lies transversely in the abdomen between the kidneys and near the duodenum of the small intestine.

Hypothyroidism

Low thyroid function

Oxytocin

Made in the hypothalamus and stored in the posterior pituitary. -Causes the uterus to contract through a positive feedback system. -Can be given artificially to help induce labor. -Also stimulates the release of milk from the mammary glands for nursing.

What does the adrenal cortex secrete a small amount of?

Male sex hormones and an even smaller amount of female sex hormones.

How are many hormones produced?

Many are proteins that are coded for by genes and synthesized within the cytoplasm at the ribosomes. Eventually, they are packaged into vesicles at the Golgi apparatus and are secreted at the plasma membrane.

How are most hormones controlled?

Negative feedback

Neurosecretory Cells

Neurons in the hypothalamus that both respond to neurotransmitters and produce the hormones that are stored in and released from the posterior pituitary.

Are mineralocorticoids under the control of the anterior pituitary?

No

Adrenal Cortex

Outer portion of the adrenal gland

What hormone causes the uterus to contract?

Oxytocin

Which hormone has a longer effect on the metabolism of the cell?

Steroid Because they can create new proteins for the cell.

Melanocyte Stimulating Hormone (MSH)

Stimulates melanocytes (cells found in the skin) to increase their synthesis of melanin.

What part of the adrenal gland is essential to life?

The cortex

What is the most significant mineralocorticoid?

Aldosterone

How does a goiter happen?

Because of the relationship between the thyroid and the anterior pituitary. When there is a low level of thyroxin in the blood, the anterior pituitary continues to produce TSH. The thyroid responds by increasing in size. However, the size increase is ineffective because active thyroxin cannot be produced without iodine.

Circadian Rhythm

Daily cycles

Cortisol favors metabolism of what?

Fatty acids rather than carbohydrates.

What primary endocrine organs are located within the brain?

Hypothalamus, pineal gland, and pituitary glands.

How goes GH impact changes on bones?

It promotes growth of the cartilaginous plates and causes osteoblasts to form new bone.

Where is the thyroid gland located?

Large gland located in the neck, where it attaches to the trachea just below the larynx.

What hormone stimulates the release of milk from mammary glands?

Oxytocin

What hormone is an example of being controlled through positive feedback?

Oxytocin - a hormone involved in childbirth that causes the uterus to contract. The action of the uterus contracting causes more oxytocin to be released. The positive feedback loop is stopped once the baby is born and the uterus no longer needs to contract, stopping the production of oxytocin.

What are the two main categories of hormones?

Peptide and steroid

Adrenocorticotropic Hormone (ACTH)

Stimulates the adrenal cortex to produce cortisol

What do all hormones have?

1. A specific organ/gland of origin 2. A specific target organ(s)/gland(s) 3. A specific action

What hormones does the anterior pituitary secrete, which then stimulate other organs and endocrine glands?

1. Growth hormone (GH) 2. Prolactin (PRL) 3. Melanocyte stimulating hormone (MSH) 4. Thyroid stimulating hormone (TSH) 5. Adrenocorticotropic hormone (ACTH) 6. Follicle stimulating hormone (FSH) 7. Luteinizing hormone (LH)

How does PTH increase the amount of calcium in the blood?

1. Stimulates the increased absorption of calcium from the intestines 2. Retains calcium through excreting phosphate at the kidneys. 3. Promotes the activity of osteoclasts to demineralize the bone, increasing the amount of calcium in the blood

What responses occur in the fight or flight reaction?

1. The blood glucose level and metabolic rate increase, as do breathing and heart rate 2. The blood vessels in the intestine contract, and those in the muscles dilate

Melanin

A dark pigment that is released when exposed to the sun.

Melatonin

A hormone manufactured by the pineal gland primarily at night that produces sleepiness.

Where is the thymus located?

A lobular gland that lies in the upper thoracic cavity in the anterior portion of the heart.

Aldosterone

A mineralocorticoid that regulates the level of sodium ions and potassium ions in the blood. Its primary target organ is the kidney, where it promotes renal absorption of sodium and renal excretion of potassium.

What hormone dilutes blood?

ADH

Homeostasis

AKA set-point; a range in which the body acts to maintain all its levels for function.

Growth Hormone (GH)

AKA somatotropic hormone Drastically affects physical appearance. 1. The amount of this hormone determines the height and bone structure of a person. 2. Causes cell growth, cell division, and protein synthesis. 3. Impacts changed on skeletal muscles, liver, and bones.

Antidiuretic Hormone (ADH)

AKA vasopressin Action is to dilute blood; stored in the axons ending in the posterior pituitary. Promotes the reabsorption of water from the collecting ducts, which receive urine produced by nephrons within the kidneys. As the blood becomes dilute, the hormone no longer is released until it is needed again.

How is iodine transported into the thyroid gland?

Actively; it can reach a concentration as much as 25 times greater than that of the blood

What does each adrenal gland consist of?

An inner portion called the medulla and and outer portion called the cortex

Hormone

An organic chemical produced by one set of cells that affects a different set of cells. Chemical messengers that influence the metabolism of the recipient cells, produced and utilized by the endocrine system.

What hormone is an example of being controlled through negative feedback?

Antidiuretic Hormone (ADH) - Its action is to dilute blood. Once the blood is dilute, the hypothalamus detects the dilute levels and shuts off the release of ADH.

What is the three-tiered relationship that exists in the endocrine system?

Between the hypothalamus, anterior pituitary, and other endocrine glands. The hypothalamus produces hormones that travel to the anterior pituitary and stimulate the anterior pituitary to produce specific hormones that control the thyroid, adrenal cortex, and gonads. In turn, these glands produce hormones that, through a negative feedback mechanism, regulate the secretion of the appropriate hypothalamic hormone.

How are hormones secreted?

By endocrine glands throughout the body.

Endocrine System

Coordinates the various activities of body parts along with the nervous system by utilizing hormones, chemical messengers, that are typically released directly into the bloodstream. Once in the bloodstream, hormones interact with cells throughout the body.

Of the various glucocorticoids, which hormone is responsible for the greatest amount of activity?

Cortisol

What hormone reduces inflammation?

Cortisol

Steroid Hormones

Derived from cholesterol by a series of metabolic reactions. Act more slowly because it takes more time to synthesize new proteins than to activate enzymes that are already present in the cell. Stored in fat droplets in the cell cytoplasm until their release at the plasma membrane. Can enter the cell and the nucleus freely instead of needing to interact with a cell-surface receptor. Have a more sustained effect on the metabolism of the cell because they can create new proteins for the cell

Peptide hormones

Derived from proteins, peptides, or catecholamines. Activate existing enzymes in the cell. Act relatively quickly but for a short period of time.

What are the two gonadotropic hormones?

Follicle stimulating hormone (FSH) and luteinizing hormone (LH)

Where are the parathyroid glands located?

Four glands embedded into the surface of the thyroid gland in the neck.

How can steroid hormones enter the cell and the nucleus?

Freely, instead of needing to interact with a cell-surface receptor. Once inside the nucleus, they bind to receptors, which create a hormone-receptor complex that activates specific genes that lead to protein synthesis.

What does the action of thyroxin do?

Generally increases the metabolic rate in all cells. The number of respiratory enzymes increases, as does oxygen intake.

What are the two major classes of hormones made by the adrenal cortex?

Glucocorticoids and mineralocorticoids

Exocrine Glands

Have ducts that secrete their contents into an epithelial surface Ex: salivary glands secrete salivary amylase into the mouth.

Adrenal Medulla

Inner portion of the adrenal gland Secretes epinephrine and norepinephrine into the bloodstream under conditions of stress.

Pituitary Gland

Lies just below the hypothalamus and is divided into two portions: posterior and anterior.

Pineal Gland

Located in the third ventricle of the brain at the midline Receives nerve impulses from the eyes by way of the optic tract. Produces the hormone melatonin, which is produced primarily at night.

Are goiters effective?

No, because active thyroxin cannot be produced without iodine.

How are the pineal gland and melatonin involved in circadian rhythms?

Normally a person grows sleepy at night when melatonin (produced by the pineal gland)levels are high, and a person awakens once daylight returns and melatonin levels are low.

Pituitary Dwarf

Occurs an individual if too little growth hormone is produced during childhood.

Pituitary Giant

Occurs an individual if too much growth hormone is produced during childhood.

Congenital Hypothyroidism

Occurs in individuals who have had low thyroid function since birth. People with this show reduced skeletal growth, sexual immaturity, and abnormal protein metabolism. The abnormal protein metabolism often leads to intellectual disability.

Acromegaly

Occurs on occasion when there is overproduction of growth hormone in the adult. Since only the feet, hands, and face (particularly the chin, nose, and eyebrow ridges) can respond, these portions of the body become overly large.

Tetany

Occurs when there is low blood calcium, which causes in increased excitability of the nerves, which fire spontaneous and without rest. The body shakes from continuous muscle contraction.

Negative Feedback

One way the body maintains homeostasis by means of "turning off" hormone production and keeping hormones within their proper range.

Which hormone acts more quickly?

Peptide [It takes more time to synthesize new proteins (Steroid) than to activate enzymes that are already present in the cell (Peptide).]

Parathyroid Hormone (PTH)

Produced by the parathyroid glands. Increased the calcium level in the blood and decreases the phosphate level.

Calcitonin

Produced by the thyroid gland; lowers the level of calcium in the blood and deposits calcium into bone. Also opposed the action of parathyroid hormone (PTH). (Makes bones weigh a ton)

T3 and T4

Produced by thyroid in response to TSH, contain iodine and increase metabolism throughout the body

Prolactin (PRL)

Produced in quantity only during pregnancy and childbirth/nursing. Causes the mammary glands in the breasts to develop and produce milk. Plays a role in carbohydrate and fat metabolism.

What is thyroxin necessary for?

Proper growth and development

Primary Endocrine Organs

Purpose is to secrete hormones that chemically regulate body functions. Hypothalamus, pituitary gland, pineal gland, thyroid gland, parathyroid glands, adrenal glands, and pancreas.

What does cortisol do in opposition to insulin?

Raises the blood glucose level

Secondary Endocrine Organs

Secrete hormones as a secondary function Heart, kidney, gonads (testes in males and ovaries in females), and thymus.

Cortisol

Secreted by the adrenal cortex under the control of the anterior pituitary hormone ACTH (adrenocorticotropic hormone) Promotes the hydrolysis of muscle protein to amino acids that enter the blood. Also counteracts the inflammatory responses that cause the body to experience pain and swelling.

Epinephrine

Secreted by the adrenal medulla; used as an emergency drug to simulate the body in patients in cardiac arrest.

What causes a disruption of sleep?

Shift work because it upsets the normal circadian rhythm. International travel, which results in jet lag because the body is still producing melatonin according to the body's "old" schedule.

At what pace does the endocrine system react to external and internal stimuli?

Slower than the nervous system It takes time for a hormone to travel through the circulatory system to its target organ.

Gonadotropic Hormones: FSH and LH

Stimulates the gonads (the testes in males and ovaries in females)

Thyroid Stimulating Hormone (TSH)

Stimulates the thyroid gland to produce T3 and T4

Where are the adrenal glands located?

Superiorly to each kidney

What are the two major hormones produced by the thyroid?

T3 and T4 (thyroxin)

Thyroxin

T4; secreted by the thyroid via negative feedback. An increased level exerts feedback control over the anterior pituitary, which ceases its production.

What happens when PTH is not produced in response to low blood calcium?

Tetany Results because calcium plays an important role in both nervous conduction and muscle contraction.

What happens when the blood vessels in the muscles dilate?

The increased circulation to the muscles causes them to have more stamina than usual.

What part of the adrenal gland can be removed?

The medulla

Hypothalamus

The portion of the brain that regulates the internal environment and homeostasis. Helps to control heart rate, body temperature, water balance, and the glandular secretions of the pituitary gland.

How is negative feedback like a thermostat?

The thermostat is set to a certain temperature, just like the body has a set-point of homeostasis. The heat turns off once the set-point has been reached, allowing the temperature to drop. The cycle happens again when the temperature drops too low.

What do epinephrine and norepinephrine do?

They bring about all the responses we associate with the "fight or flight" reaction.

How do cells react to a hormone?

They have specific receptors, which combine with the hormone in a lock and key manner. Therefore, certain cells respond to one hormone and not to another, depending on the cell's surface receptors.

Where is calcitonin produced?

Thyroid gland

Dilate

To expand

Why is the blood sodium particularly important?

To the maintenance of blood pressure, and the concentration of the ion indirectly regulates the section of aldosterone.

When does the parathyroid gland stop producing PTH?

Trough negative feedback when the blood calcium reaches the appropriate level.

What leads to an increased level of glucose?

When the liver converts amino acids to glucose in response to cortisol's promotion of the hydrolysis of muscle proteins to amino acids that enter the blood.