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Unit 8: Endocrine System

+Function

Coordinates and directs the activity of the body’s cells This is the same function of the nervous system

However: Nervous system: signals are specific and fast-acting Endocrine system: signals are wide-spread and long-lasting

+Physiology: How does it work?

Hormones: chemical messengers that are released into the bloodstream and transported throughout the body A given hormone only affects certain tissues or organs

Referred to as target cells or target organs

+Lock and Key Model

Only certain hormones will affect certain organs because of the presence of the right receptor

+Hormones

2 classes: Steroid hormones: comprised of fats Nonsteroid hormones: comprised of proteins or amino acids

+Steroid Hormones

Hormones can pass straight through the cell membrane Often derived from

cholesterol Lipid soluble

Let’s draw our own picture!

+Nonsteroid Hormones

Hormones interact with the cell’s plasma membrane and initiate a cascade of signals that will occur within the cells This is known as a second

messenger system Hormone = first messenger Cascade of messengers

and signals within the cell = second messenger

Let’s draw our own picture!

+What do hormones control?

Reproduction

Growth and development

Mobilizing body’s defenses

Maintaining chemical homeostasis

Cellular metabolism and energy balance

+How do hormones provide control?

Negative feedback Hormones secretion inhibits further hormone release

Example: Ovaries release a hormone called estrogen. When the ovaries release enough hormone to cause a

slight increase in concentration in the blood, the ovaries stop secreting hormone

Let’s draw a picture of this!

+Glands

There are many major endocrine glands in the body Examples:

Hypothalamus Pituitary Thyroid Parathyroid Thymus Adrenal gland Pancreas Ovary Testis Pineal Gland

+WS #1 Endocrine Glands of the Body

+Glands

The hypothalamus and pituitary glands are the head honchos of the endocrine system In charge of controlling the release of all other hormones

+Pituitary Gland

Controlled by the hypothalamus

Size of a grape

Sits on a bone called the sella turcica (Turkish saddle)

2 functional lobes Anterior pituitary

Glandular tissue Posterior pituitary

Nervous tissue

+Pituitary Gland: Anterior Lobe

The anterior portion secretes hormones called tropic hormones Stimulate target organs

Some are endocrine and some nonendocrine All tropic hormones are

Nonsteroid hormones Question: Where is the receptor located on the target

cell? On the plasma membrane!

+Tropic Hormones

+Let’s Make a Table!

Hormone from Anterior Pituitary

Abbreviation Target Organ

+Whiteboard practice!

+Pituitary and Hypothalamus relationship

Anterior pituitary is controlled by the hypothalamus The hypothalamus produces releasing and inhibiting

hormones that control the release of the tropic hormones into the bloodstream

+Hypothalamus Hormones

The releasing hormones are really easy to remember! If the anterior pituitary is secreting growth hormone (GH), it

was stimulated by growth hormone releasing hormone (GHRH) from the hypothalamus

+Releasing Hormones

Predict: What tropic hormones will be secreted when the pituitary is stimulated with the following hormones? Thyroid releasing hormone? (TRH)

TSH Corticotropin-releasing hormone? (CRH)

ACTH Gonadotropin-releasing hormone? (GnRH)

FSH/LH

+Putting it all together with negative feedback

All of the hormones we have talked about exhibit negative feedback

Releasing hormone tropic hormone hormone

That is, the release of the target organ’s hormone will REPRESS the release of the hypothalamus and pituitary hormones

+Let’s Draw a Picture!

+Whiteboard practice!

+Focus: Thyroid

1) hypothalamus secretes TRH

2) TRH stimulates the anterior pituitary to release TSH

3) TSH travels to target organ (thyroid)

4) Thyroid produces thyroid hormone

+Thyroid Hormone

Function: Increase a person’s basal metabolic rate (BMR) (speed up their metabolism) and increase heat production

Question: If thyroid hormone exhibits negative feedback of further thyroid hormone production, excess thyroid hormone would cause ____________ and ___________ to stop being released. TSH and TRH This is negative feedback at work, folks!

+Too Much? To Little?

Hyperthyroidism: excessive production of thyroid hormone Causes Graves’ disease

Symptoms: constant feeling of warmth (as a result of increased BMR), weight loss, nervousness, and enlarged thyroid gland (goiter)

Hypothyroidism: decreased production of thyroid hormone Symptoms: lower BMR (intolerance of cold), decreased

appetite, weight gain

+

+Focus: Adrenal Glands

1) hypothalamus releases CRH

2) CRH stimulates the anterior pituitary to release ACTH

3) ACTH travels to target organ (adrenal glands)

4) Adrenal glands produce cortisol

+Question

If there is a high concentration of cortisol in the blood, the hypothalamus will release _______________ CRH. A: more B: less

CRH ACTH Cortisol

+Cortisol

Function: promotes the breakdown of proteins and fats and helps the body adapt to stress Provide the body with fuel to break down materials in the

body Can also act as an immunosuppressive and anti-

inflammaory Can shrink organs in the immune system

Ie thymus gland

+Too Much? Too Little?

Hypercortisolism: excessive amount of cortisol Causes Cushing’s syndrome

Symptoms: personality changes, hypertension (high blood pressure), osteoporosis, and weight loss

Hyposecretion: decreased secretion of cortisol Symptoms: defective metabolism, mental confusion,

decreased ability to adapt to stress

+Focus: Gonads

1) hypothalamus releases GnRH

2) GnRH stimulates the anterior pituitary to release LH

3) LH travels to the gonads (ovaries and testes)

3) Gonads secrete sex hormones (estrogen and testosterone)

+Testosterone

Function: Secondary sex characteristics of males Increased body hair and deeper voice

+Too Much? Too Little?

Too much testosterone? Increased muscle mass Male pattern baldness Acne Premature sexual development

Decreased amount of testosterone? Abnormal sexual development Low sperm count

+Rule of Thumb

The more a gland is activated, the larger it gets Known as hypertrophy (an increase in size)

Think about a person lifting weights—the more you use that muscle, the bigger your muscles get!

If a gland is continually inhibitied, it will shrink in size Known as atrophy (shrinking in size)

+Predict:

Let’s say your glands are 100% normal and they are working properly. However, your target organs changed their “locks” AKA

their receptors Would they be responsive to hormones?

What would happen if a person with an XY chromosome was born with an insensitivity to testosterone?

+Androgen Insensitivity Syndrome

The receptors on the target cells for testosterone (for example, the ones in the gonads) are unresponsive to testosterone This would have occurred since birth—this is a congenital disease

The female set-up is default Without testosterone, you would end up looking like a female on

the outside

These individuals spend their whole lives thinking that (and looking like) they are female until puberty They would grow the secondary sex characteristics (breasts), but

menstruation would not occur This is usually the time when they diagnose this disease https://www.youtube.com/watch?v=JjI-RvkjujI