Download - Unit 8: Endocrine System
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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
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+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