mr. wright 2011 chapter 11:. section 11.1 the endocrine system the body has two systems designed...
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THE ENDOCRINE SYSTEM
Mr. Wright 2011
Chapter 11:
IntroductionSection 11.1
The Endocrine System
The body has two systems designed for communication:The Nervous SystemThe Endocrine System
Allows the body to change to different situations.
The Endocrine System
Made up of glands. Glands secrete hormones. Hormones enter the bloodstream and
are carried to specific target cells.
Local Hormones
Some hormones never enter the bloodstream… they stay in the same area and are called local hormones.Paracrine – affect neighboring cellsAutocrine – affect the secreting cells
themselves.
Exocrine Glands
Exocrine glands secrete things outside the body.Example: Sweat
General Characteristics
Section 11.2
Comparing Nervous & Endocrine
Nervous System Endocrine System
Involved in communication.
Releases neurotransmitters into synapses.
Very precise. Very brief.
Involved in communication.
Releases hormones into bloodstream
Very precise. Can be brief or very long.
Things the Endocrine System Controls… The endocrine system regulates many
metabolic processes.Rates of chemical reactions.Transport across membranes.Regulate water and electrolyte balances.ReproductionDevelopmentGrowth
Glands of the Endocrine System
Hormone ActionSection 11.3
Hormones
There are 3 main types of hormones:SteroidsNonsteroidsProstalandins
Steroid Hormones
Steroid hormones are made or rings of carbon and hydrogen atoms.
They are insoluble in water, but are soluble in lipids (fats) like cell membranes. Thus, they can enter and exit cells easily.
Nonsteroid Hormones
Nonsteroid hormones cannot enter cells. Instead, they combine with receptors in
the cell membrane.
Prostaglandins
Prostaglandins are special lipids synthesized from fatty acids in the cell membrane.
Produced in the liver, kidneys, heart, lungs, brain, and several endocrine glands.
Prostaglandins
Produce many diverse effects.Relax/Contract smooth (involuntary)
muscles.Stop production of stomach acid.Influence movements of salt and water in
the kidney.Regulates blood pressure.Stimulates other hormones.
Control of Hormonal Secretions
Section 11.4
Hormonal Secretions
As hormone levels increase in the blood, hormone secretion decreases.The more there is, the less we need.The opposite of this statement is true as
well.
Hormonal Secretions
Hormonal secretion is controlled by negative feedback.Negative feedback – the mechanism is
controlled by an imbalance that corrects it.
Examples of Negative Feedback
The hypothalamus stimulates the pituitary gland to secrete hormones.
The pituitary gland secrets hormones which stimulate the ovaries to secrete hormones needed for puberty.
If the ovary hormone levels in the blood are too high, the hypothalamus stops stimulation.
Examples of Negative Feedback
When blood sugar levels are high, the pancreas secretes insulin.
Blood sugar levels decrease.
Once blood sugar levels are low enough, pancreas stops secreting insulin.
Conclusion
As a result of negative feedback, hormone levels in the blood remain relatively stable, with only slight changes.
The Pituitary GlandSection 11.5
Structure The pituitary gland is
found hanging beneath the brain.
Very small. Attached to the brain
by a small stalk called the infundibulum.
2 halves:AnteriorPosterior
Function
Controlled mostly by the brain. Releasing hormones – hormones the
brain (hypothalamus) secretes to signal the pituitary to release its hormones.
Each releasing hormone acts on a specific part of the pituitary.
Hormones - Anterior
Human Growth Hormone (HGH)Stimulates cells to increase in size and
divide more frequently.HGH is released when there are low protein
or sugar levels in the blood.Disorders:
Hormones - Anterior
Prolactin (PRL)Pro- = with, for-lactin = milkStimulates milk production
in females.PRL is found in males.
○ Excess PRL in males decreases the amount of male sex hormones.
Hormones - Anterior
Thyroid-Stimulating Hormone (TSH)Controls the secretion of hormones by the
thyroid.
Adrenocorticotropic Hormone (ACTH)Controls the secretion of hormones by the
adrenal gland.
Hormones - Anterior
Follicle-Stimulating Hormone (FSH)Stimulates the gonads.Gonads – reproductive organs
○ Testes in males○ Ovaries in females
Remember what follicles are?
Hormones - Posterior
Antidiuretic Hormone (ADH)Decreases urine formation.Does this by lowering the amount of water
secreted by the kidneys.Stimulated by fluid levels in the body.
Hormones - Posterior Oxytocin (OT)
Stimulates uterine contractions during childbirth.
Contracts smooth muscles in the uterus.
Stimulated by stretching of uterine and vaginal tissues.
Thyroid GlandSection 11.6
Structure
Consists of two lobes connected by the isthmus.
Just below the larynx and in front of the trachea.
Thyroid Hormones
Thyroxine (T4)Regulates the metabolism of sugars, lipids,
and proteins.Determines how many calories you need to
consume to live.
Thyroid Hormones
Triiodothyronine (T3)Same function as Thyroxine, though this is 5
times more potent.Both are stimulated by iodine levels in the
body.This iodine comes from food.
Thyroid Hormones
CalcitoninIncreases calcium and phosphate
concentrations in the blood.Does this by regulating
osteoclast/osteoblast activity and the kidneys.
Thyroid Problems
CretinismCaused by not having enough thyroid
activity (hypothyroidism).Symptoms:
○ Stunted Growth○ Abnormal Bones○ Mental Retardation○ Sluggishness
Thyroid Problems
GoitersToo much thyroid activity (hyperthyroidism)
leads to a swelling of the tissues behind it.This causes a large bulge in the neck called
a goiter.
Parathyroid GlandsSection 11.7
Structure
You have four. They are very small. Found on the posterior thyroid. Covered in CT.
Parathyroid Hormone
Parathyroid Hormone (PTH)Increases blood calcium levels
and decreases blood phosphate levels.
Similar to calcitonin.
Adrenal GlandsSection 11.8
Structure
Located superior to the kidneys… sits on top of them like a cap.
Made up primarily of epithelial cells and blood vessels.
2 parts:Adrenal medulla – centerAdrenal cortex - outsides
Hormones – Adrenal Medulla Epinephrine and Norepinephrine
Similar in structure and function.Epinephrine is actually made from
norepinephrine.Several effects:
○ Increases heart rate.○ Elevates blood pressure.○ Increases blood sugar.○ Addictive
ADRENALINE!!!
Disorders - Adrenaline
People who have too much adrenaline produced will suffer from high blood pressure, high blood sugar levels, increased heart rate, etc… hypertension.
Disorders - Adrenaline
Those who do not have enough adrenaline produced may be lackadaisacal and/or unexcitable – hypotension.
Hormones – Adrenal Cortex Aldosterone
Helps regulate the concentration of minerals. (Na and K)
Does this by increasing water retention.
Hormones – Adrenal Cortex Cortisol
Increases glucose levels in the blood.
Very similar to T3 and T4.
Hormones – Adrenal Cortex The adrenal cortex also produces some
sex hormones. This is not the primary source of these
hormones, however, so we will talk about them more once we get to the gonads next week.
The PancreasSection 11.9
Structure
Long, flattened organ behind the stomach.
Connected to the small intestine by a small duct.
Structure
Has two functions:Digestive (Will discuss later)Endocrine
The endocrine cells are arranged into special groups called islets of Langerhans.Alpha cellsBeta cells
Hormones - Pancreas
GlucagonRaises blood sugar concentration.
○ More effective than epinephrin/norepinephrinReleased by alpha cells.
Hormones - Pancreas
InsulinLowers blood sugar concentration.Direct opposite to glucagon.Released by beta cells.Often released after eating.
Disorder - Diabetes
Caused by an insulin deficiency. Blood sugar levels rise. The kidneys will excrete excess sugars
into urine, which also causes more water to be added.Leads to dehydration and extreme thirst.
Disorder - Diabetes
Insulin also helps glucose move into cells, which means this isn’t happening anymore.
Cells will break down proteins instead, causing tissues to disappear and leading to weight loss.
Type 1 Diabetes
Autoimmune disease – the body’s immune system destroys its own beta cells.
Also called juvenile diabetes. Treated via insulin injections.
Type 2 Diabetes Develops in people over age 40. Milder symptoms. Generally seen in overweight people. Beta cells work, but body cells lose sensitivity
to insulin so injections don’t work. Treated via diet changes, exercise, etc.
Other Endocrine Glands
Section 11.10
The Pineal Gland
Small structure located deep between the cerebral hemispheres.
Hormones – Pineal Gland
MelatoninReleased in response of light amounts
outside of the body.○ More is released in the dark.
Responsible for your “biological clock”○ Circadian rhythm○ Determines daily sleep cycle, but also puberty
and menstrual cycle.
Thymus Gland
Found posterior to the sternum, in between the lungs.
Large in children but shrinks with age.
Hormones - Thymus
ThymosinsProduce white blood cells.Also determines the type of each white
blood cell.Will discuss more when we get to immune
system.
Reproductive Glands
Include the ovaries, placenta, and testes.
Will be discussed in much more detail when we get to that chapter.
Hormones - Gonads
FemalesEstrogenProgesterone
MalesTestosterone
Will discuss in more detail later.
Stress and HealthSection 11.11
Stress
When the body senses danger, it triggers physiological responses designed to take care of it.Includes an increase in certain hormones.
This condition is called stress. Anything that causes it is called a
stressor.
Types of Stress
Physical – temperature, oxygen levels, infection, injury, etc.
Psychological – thoughts, feelings, sense of loss, unpleasant social interactions
Doesn’t have to be a negative thing, either. Can be friendly contact, feelings of joy, sexual arousal, etc.
Responses to Stress
Controlled by the hypothalamus of the brain.“Fight or Flight”
Things your body does:Raise blood sugar levelsIncrease heart rate, blood pressure,
breathing rateExcess blood to musclesIncreases epinephrine levels
Stress Drawbacks
These reactions can cause:High blood pressureUlcer formationLower WBC count/increased risk of
infection.