Wize University Physiology Textbook > Endocrine Physiology
Hormone Production Glands
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Pituitary Gland
- located in the brain
- works closely with the hypothalamus
- split into two parts:
- Anterior pituitary - makes 6 different peptide HORMONES
- Posterior pituitary - stores 2 different peptide NEUROHORMONES
Anterior Pituitary Makes:
- Adrenocorticotropic hormone (ACTH) - Target = Adrenal Gland
- Growth hormone (GH) - Target = Tissues
- Lutinizing hormone (LH) - Target = Gonads
- Thyroid stimulating hormone (TSH) - Target = Thyroid Gland
- Follicle-stimulating hormone (FSH) - Target = Gonads
- Prolactin - Target = Mammarian Glands
Posterior Pituitary Stores:
- oxytocin
- antidieretic hormone (ADH)
Watch Out!
Anterior MAKES. Posterior STORES hormones from the hypothalamus
commons.wikimedia.org
Hypothalamus-Pituitary-End Organ communication
- negative feedback loop
- basically, the end organ (ex. adrenal) produces a certain hormone (cortisol). That hormone is a negative feedback for hypothalamic and pituitary hormones (ex. CRH and ACTH) that will later go on to create the hormone from the end organ.
- big picture - the hormones all regulate themselves and the levels they need!
- both of the images below are showing the same thing, just in a different way visually - pick the one your brain understands the best to study from!
commons.wikimedia.org
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What is the difference between the anterior pituitary and the posterior pituitary? What hormones are they each associated with?
The anterior pituitary makes its own hormones. Its hormones affect different parts of the body including glands. These glands can produce other hormones that will affect certain organ systems. The anterior pituitary makes 6 different types of hormones:
- TSH
- ACTH
- FSH
- GH
- LH
- Prolactin
The posterior pituitary stores hormones created by the hypothalamus. These hormones, when released, stimulate glands in the body to release other hormones that will affect organ systems in the body. The posterior pituitary stores:
- oxytocin
- ADH
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The Thyroid Gland
- located in the neck
- the cells are set up in a circular pattern
- Follicle = circular area with cells surrounding the outside. This is where hormones are made
- Colloid = center of the follicle. This is where hormones are stored
Hormone Production
- made of tyrosine (amino acid) chains called thyroglobulin + iodine
- once in the follicles, tyrosine is built into thyroglobulin
- iodine is added to thyroglobulin in the colloid
- MIT = iodine + tyrosine
- DIT = iodines + tyrosine
- T3 = MIT + DIT
- T4 = DIT + DIT
3. T3 and T4 taken back into follicle cell
4. T3a nd T4 separated from large thyroglobulin chain by protein degradation
Hormone Functions
- in general = alter gene transcription
- metabolism
- nervous system effects
- cardiovascular effects
- muscular effects
- negative feedback for its own synthesis by effecting TRH and TSH production
Thyroid Disorders
- Hyperthyroidism - too much thyroid stimulation = too much T3 and T4 = high metabolism, high heart rate, anxiety
- Hypothyroidism - not enough T3 and T4 made = low metabolism, weight gain, tiredness, always cold.
Hope is 20 years old and thinks she has a medical problem. She started having anxiety and menstrual problems and a few months ago. Now, she's noticing that her thoughts are always racing and she can't sleep well at night. She's been trying to study for her physiology exam, but she's extremely tired and has a very hard time focusing.
Answer true or false for the following statements
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Adrenal Gland
- Located in close proximity to the kidneys
- cells are modified sympathetic neurons --> The gland is activated when the sympathetic nervous system is activated.
Made of two different parts:
- Adrenal Cortex
- sex hormones (androgens)
- cortisol (a type of glucocorticoids)
- aldosterone (a type of mineralocorticoids)
- Adrenal Medula
- epinephrine (a catacolamine hormone)
commons.wikimedia.org
Adrenal Medulla
Epinephrine
- fight or flight response hormone
- causes increased heart rate, brochodilation, intestinal relaxation, etc.
- Has diverse effects because it:
- has specific receptors
- the receptors have different affinity based on epinephrine concentration
Epinephrine Receptors
- epinephrine can cause vasoconstriction OR vasodilation depending on what type of receptor it binds to.
- Alpha receptor binding causes vasoconstriction as seen in the intestine
- Beta receptor binding causes vasodilation as seen in muscle cells
- each blood vessel has either an alpha or a beta receptor.
- At low concentrations, epinephrine is more effective on the beta receptors (causing vasodilation)
- At higher concentrations, epinephrine is more effective on alpha receptors (causing vasoconstriction)
commons.wikimedia.org
Adrenal Cortex
The medulla has 3 main layers that each produce different hormones
- zona reticularis - produces sex hormones
- zona fasciculata - produces cortisol
- zona glomerulosa - produces aldosterone
How are the layers different?
- the enzymes produced there
Androgens
- produced in zone reticularis (sex hormone precursor)
- plays a role in females and in child development
Aldosterone
- works on the kidneys
- causes sodium and water to be reabsorbed into the blood
- sitmulated by
- high [k+] in blood plasma
- ACTH hormone
- Angiotensin ll hormone
- inhibited by
- too much extracellular fluid/high osmolarity
Cortisol
- increases [glucose] by breaking down larger macromolecules
- reduces [Ca+]
- supresses immune system
- release process
- negative feedback
- stimulated by circadian rhythms or stress ––> hypothalamus (CRH) ––> pituitary (ACTH) ––> adrenal gland ––> cortisol release
- can be changed a bit to be used as an immunosuppressant drug
commons.wikimedia.org
Disorders Associated With The Adrenal Gland
- Cushings - too much cortisol
- Conns - too much aldosterone
- Addisons - too much steroid hormone secretion
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What are the three layers of the adrenal cortex and what do they produce? What makes them all different?
- zona reticularis - produces sex hormones
- zona fasciculata - produces cortisol
- zona glomerulosa - produces aldosterone
How are the layers different?
- the enzymes produced there are different. Each enzyme type makes the cells produce different hormones.