A&P - Chapter 15: Endocrine System

Endocrine System

A means of body system control and regulation (after the NS), composed of glands which secrete chemical signals into the circulatory system.

Functions of Endocrine System

1) Metabolism and tissue maturation

2) Ion regulation

3) Water balance

4) Immune system regulation

5) Heart rate and blood pressure control

6) Blood glucose and other nutrient levels

7) Reproductive system control and development

8) Uterine contractions and milk release

Hormone

Chemical messenger or ligand.

Hormone Qualities

1) Produced in small amounts by relatively few cells.

2) Secreted

3) Transported around the body via circulatory system.

4) Acts on target tissues only.

5) Can be lipid-soluble or water-soluble.

receptors

Hormones bind to specific _________ that only target cells have.

Amplitude-Modulated

The strength of the response is regulated by the level of hormone, this is called ___________________ signaling.

negative feedback

________________ usually controls how and when hormones are secreted. Ex.) When blood glucose levels fall, less insulin is produced. When blood glucose levels increase, insulin production increases.

Ways Hormone Secretion is Regulated

A) Direct response to current blood hormone levels.

B) Nervous system stimulation.

C) Stimulation from other hormones.

blood

Some hormones travel freely in the _______.

transport

Some hormones require __________(binding) proteins to travel throughout the body. Hormones with binding proteins tend to last longer in blood.

How Hormone Levels Decrease

1) They reach target tissue and leave bloodstream.

2) They are excreted, typically via the kidneys and urine, or the liver and bile.

receptor site

Each receptor is a protein or glycoprotein. The portion that actually attaches to the hormone is called the ___________ or binding site.

shape, chemistry

A receptor’s _____ and __________ determine what hormones can attach to it.

specificity

The receptors show ____________, meaning they can only bind specific hormones. A few hormones can bind to multiple receptors but that is unusual.

receptors

Just like changing the level of hormone changes the strength of response, changing the amount of ___________ also works.

Up-regulation

Increase of receptors available.

Down-regulation

Decrease of receptors available.

mimic

Many pharmaceutical drugs target the binding sites of receptors as a way to block or ______ hormone effects.

Agonist

Drug which activates receptor.

Antagonist

Drug which blocks receptor.

Membrane-bound

Receptors stuck in cell membrane with binding site on outside of cell.

Nuclear

Receptors near nucleus and DNA of cell. Affects the cell’s DNA and it’s production of proteins, and can only bind to lipid-soluble hormones (to sneak through cell membrane).

Types of Membrane-Bound Receptors

1) Ionotropic

2) Metabotropic

Ionotropic

Receptor and a channel are the same structure.

Metabotropic

Receptor is separate from channel or whatever structure is responding.

Pituitary Gland

(Hypophysis) Gland inferior to hypothalamus, connected via bridge-like infundibulum. It produces nine major hormones.

Hypothalamus

Portion of brain regulating release of pituitary hormones, receives other hormones, most sensory information, and is sensitive to emotions (all of these affect hormone levels).

Sections of Pituitary Gland

1) Anterior

2) Posterior

True

T or F: The two major sections of the pituitary gland develop from entirely different portions of a human but come together to form one structure.

Neurohypophysis

(Posterior Pituitary) Forms in the brain.

Adenohypophysis

(Anterior Pituitary) Grows from the roof of the mouth but separates later.

infundibulum

The hypothalamus and pituitary glands are connected via ____________, inside, there is a network of blood vessels called the hypothalamohypophyseal portal system.

hypothalamohypophyseal

Network of blood vessels carries hormones from the hypothalamus directly to the anterior pituitary.

Releasing Hormones

Encourage release of another hormone.

Inhibiting Hormones

Discourage release of another hormone.

neurosecretory neurons

There is no portal system between the hypothalamus and posterior pituitary gland. Instead, __________________ reach from the hypothalamus through the infundibulum to a capillary bed in the posterior pituitary and directly release hormones there.

Posterior Pituitary Hormones

1) Antidiuretic Hormone

2) Oxytocin

Antidiuretic Hormone

(Vasopressin) Increases reabsorption of water from urine in kidneys, and in large amounts can constrict blood vessels.

Oxytocin

Causes contractions of the uterus in birth, and milk “let-down” in breasts of lactating women. Causes contractions of the uterus in non-pregnant women (cramps) and promotes movement of sperm cells inside a uterus or uterine tubes. Plays a role in social behavior such as feeling of attachment and maternal behavior and also inhibits memory, decreases of stress, suppresses appetite, and raises pain threshold.

Anterior Pituitary Hormones

1) Growth hormone (GH or HGH)

2) Thyroid-stimulating hormone (TSH)

3) Adrenocorticotropic hormone (ACTH)

4) Melanocyte-stimulating hormone (MSH)

5) Luteinizing Hormone (LH)

6) Follicle-STimulating Hormone (FSH)

7) Prolactin

Growth Hormone

Stimulates growth of most human tissue, affects epiphyseal plates and therefore someone’s height, encourages lipolysis.

Lipolysis

Breakdown of fats for energy.

liver

GH encourages glucose synthesis in the ______. This makes more energy and higher blood sugar levels.

somatomedins

GH also encourages production of ________________ in the liver which causes bone and cartilage growth.

circadian rhythm

Most people’s GH levels rise and fall with _____________ (day and night cycle), peaks during sleep.

Hypothalamus Releases

1) Growth Hormone-releasing hormone, encourages GH synthesis.

2) Growth Hormone-inhibiting hormone, discourages GH synthesis.

stress

Low blood glucose levels and _______ encourages release of GHRH. High blood glucose levels encourage release of GHIH.

Thyroid Gland

The gland around the trachea and esophagus, is inferior to the larynx, is one of the largest endocrine glands, and is very vascular & appears red.

isthmus

The thyroid gland has two lobes, right and left, connected by a narrow strip called the _______.

Follicles

Spheres with a layer of simple cuboidal epithelium called follicle cells.

tissue

Thyroid ______ contains many follicles.

Thyroglobulin

Follicle cells are filled with _____________, protein which stores thyroid hormones.

C Cells

(Parafollicular cells) Found between follicles, produce and secrete calcitonin.

Calcitonin

____________ plays a not yet understood role in lowering blood Ca+2 levels.

T3

(Triiodothyronine) 10% of secretions. Affect most human cells and encourage more metabolism, leading to more breakdown of sugars, fats, and proteins for energy. As well as more body heat and more mitochondria activity.

T4

(Tetraiodothyronine or Thyroxine) 90% of secretions. Affect most human cells and encourage more metabolism, leading to more breakdown of sugars, fats, and proteins for energy. As well as more body heat and more mitochondria activity.

iodine

The 3 and 4 (in T3 & T4) refer to the number of ______ atoms. Iodized salt exists so people can get enough iodine in their diet.

TSH

_____ from the anterior pituitary gland encourages the follicle cells to take in iodide.

TBG

T3 and T4 bind to other proteins when released into blood, mostly _____ from the liver. 20-30% to other random blood proteins like albumin.

cold

Being _____ stimulates more release of T3 and T4.

False

T or F: Hypothalamus can release TRH which encourages the thyroid to release T3 and T4, therefore encouraging the pituitary gland to release TSH.

Hypothyroidism

Reduced or no secretion of T3 and T4, could be a TSH deficiency or an iodide deficiency.

Hyperthyroidism

Abnormal increase of T3 and T4.

Goiter

Caused by increase in follicle cell size.

Adrenal Glands

(Suprarenal Glands) There are two of them, one above each kidney. It is split into two main sections, the medulla (inner) and cortex (outer).

Cortex Layers

1) Zona Glomerulosa

2) Zona Fasciculata

3) Zona Reticularis

Hormones of Adrenal Medulla

1) Epinephrine (Adrenaline) (80%)

2) Norepinephrine (20%)

Hormones of Adrenal Cortex

1) Mineralocorticoids

2) Glucocorticoids

3) Androgens

fight or flight

Epinephrine and Norepinephrine are the hormones that prepare the body for “________________”.

Effects of E and NE

1) Increased release of glucose sugar from liver for energy

2) Increased release of fat from fat cells for energy

3) Increased heart rate

4) Increased blood flow to heart and skeletal muscles

5) Increased metabolism in skeletal muscle, cardiac, and nervous tissues

Mineralocorticoids

Steroid hormone, more than one type but the main one is aldosterone. It increases the reabsorption of Na+ from urine in kidneys, increases blood Na+ levels, and increases blood water levels and blood pressure.

Glucocorticoids

Steroid hormone, more than one type but the main one is cortisol. It increases metabolism of protein and fat, increases liver production and release of glucose, increases blood sugar levels, and reduces inflammation and local immune response.

Androgens

Stimulate development of secondary male characteristics, most are converted to testosterone, small amounts are produced by both females and males. In males, the effecst is hardly noticeable because the tests produce a lot of it.

Corticopin

The hypothalamus produces _________ releasing hormone in response to stress and low blood glucose levels, which encourages the anterior pituitary gland to release adrenocorticotropic hormone. This encourages the adrenal cortex to release cortisol.

Pancreas

Both an exocrine and endocrine gland, produces pancreatic juice which travels through a duct system similar to the small intestine (exocrine function). It also has between 500,000 - 1 Mil. islets of Langerhans or pancreatic islets which secrete hormones (exocrine function).

Pancreatic Islets

Dispersed throughout pancreas and each is connected to the ANS and also to multiple capillaries.

Alpha Cells

Produce glucagon.

Beta Cells

Produce insulin

Insulin

This hormone targets the liver, adipose tissue, skeletal muscles, and the satiety center of the hypothalamus. Causes more glucose and amino acid transport proteins to be placed in cells, leading to less glucose in blood, more use of glucose as cell’s energy, and more storage of glucose within liver as glycogen and within adipose cells as fat.

Satiety Center

Regulates appetite.

brain

Most of the _______ does not react to insulin.

ketone bodies

When insulin is low, the reverse effects happen. The liver will also release ______________ for energy.

Glucagon

Hormone that targets the liver, causes stored glycogen to be converted back to glucose and increases blood glucose levels.

Beta

_____ cells respond directly to current blood glucose levels for insulin production, and can also be stimulated or suppressed by ANS in response to digestive process or exercise.

Alpha

______ cells respond directly to current blood glucose levels for glucagon production.

amino acids

Both alpha cells and beta cells also respond to the presence of ___________ in blood.

Diabetes Mellitus

A disorder involving insulin that causes high blood glucose levels. Has two types.

Type One Diabetes

Insulin-dependent diabetes mellitus (IDDM). Makes up about 5-10% of cases and is an autoimmune problem. It is heritable.

Type Two Diabetes

Non Insulin-dependent diabetes mellitus (NIDDM). Makes up about 90-95% of cases and is a problem of insulin resistance. Is influenced by genetics, but much more by lifestyle choices of diet and exercise.

Autoimmune

Person’s own immune system is attacking the islets of Langerhans, no insulin is produced.

Insulin Resistance

Cells are losing receptors to bind insulin hormone or enzymes between receptor and transport protein are messed up.

gestational

4% if women who give birth will temporarily experience ___________ diabetes because of hormone changes.

Hyperglycemia

Abnormally high blood glucose levels, is the primary symptom tested for when looking for diabetes mellitus.

untreated

People with ___________ diabetes also have polyuria and polydipsia.

Polyuria

Increased urine volume.

Polydipsia

Increased feeling of thirst.

Insulin Shock

Occurs when there is too much insulin in blood. Can occur after a patient injects insulin, or can cause disorientation, sweating, fast heart rate, or a coma.

Testosterone

Produced by testes, causes growth and development of male reproductive structures, muscle enlargement, body hair growth, voice changes, and male sexual drive.

Estrogen, progesterone

Produced by ovaries, causes development and function of female reproductive structures, enlargement of breasts, female distribution of fat, and menstrual cucle.

Pineal Gland

“Pinecone-shaped” gland that produces melatonin.