Lecture 13- Endocrine System II Flashcards
Simple Endocrine Pathway
Endocrine cells respond directly to stimulus
-> Secrete hormone
Hormone travels via bloodstream
-> Interacts with target cells
-> Physiological response
Simple Neuroendocrine Pathway
Stimulus received by sensory neuron
Stimulates neurosecretory cells
-> Secrete neurohormones
Travel via bloodstream
-> Interacts with target cells
-> Physiological response
Hypothalamus
Key regulatory structure
Part of brain- neuroendocrine
Links nervous and endocrine systems
Connected to pituitary gland by portal vessels
How is the hypothalamus connected to the pituitary gland?
Portal vessels
What are the hormones released into pituitary portal vessels?
Releasing hormones (RH) & Inhibiting hormones (IH). Directly bathes anterior pituitary (AP). Stimulates or inhibits release of specific hormones from AP.
Where are the releasing hormones (RH) and inhibiting hormones (IH) sent from/to?
Sent from the hypothalamus, to the anterior pituitary (AP)
What TYPE of hormones are in the posterior pituitary?
Posterior Pituitary NEUROHORMONES
What hormones are located in the posterior pituitary? How do they get there/where are they produced?
Antidiuretic hormone (ADH) and Oxytocin are located in the posterior pituitary. They are secreted by neurosecretory cells in the hypothalamus. Axons extend into posterior pituitary (PP). These hormones are then stored in vesicles until needed.
Where are posterior pituitary hormones stored?
Stored in vesicles until needed
What are the pituitary hormones in the posterior pituitary? What are their functions?
Stores and secretes:
1. Antidiuretic hormone (ADH)- Water conservation (kidneys)
2. Oxytocin- milk, contractions, care, bonding
What are Anterior Pituitary hormones controlled by?
AP= Endocrine gland- hormones released into blood
Every AP hormone controlled by at least 1 RH (Releasing hormone)
Some also controlled by an IH (Inhibiting hormone)
What is the Hormone Cascade Pathway?
Term for sets of hormones from hypothalamus, AP, target endocrine gland, and response in target tissue
Hypothalamus -> AP -> other gland -> target tissue -> response
What are the functions of a healthy thyroid? (at homeostasis)
Stimulate cellular metabolism in virtually all cells
Maintain normal blood pressure, heart rate, muscle tone
Regulate digestive, reproductive functions
What is a tropic hormone?
A hormone produced in one gland that stimulates another gland to produce its own hormones.
The hypothalamus releases thyrotropin-releasing hormone (TRH) that stimulates the anterior pituitary to produce thyroid-stimulating hormone (TSH)
Thyroid hormone drops below normal range- steps
Hypothalamus secretes thyrotropin-releasing hormone (TRH)
Stimulates anterior pituitary (AP)
Anterior pituitary secretes thyroid-stimulating hormone (TSH, sometimes called thyrotropin)
Stimulates thyroid
Thyroid secretes thyroid hormone
Thyroid Gland (location, what does it secrete)
2 lobes, ventral surface of trachea in neck
Secretes 2 hormones (both called thyroid hormone)
Both derived from tyrosine and iodine
T3, 3 iodine
T4, 4 iodine
Is thyroid regulation positive or negative feedback?
Negative feedback. When TH is at normal levels, TSH and TRH are suppressed.
Full steps Thyroid regulation
- Stimulus- low TH
- Hypothalamus secretes TRH= thyrotropin-releasing hormone
- AP secretes TSH= thyroid stimulating hormone
- TSH circulates in body
- TSH stimulates thyroid
- TH released, circulates
- Response
Negative feedback: TH at normal levels -> TSH and TRH suppressed
Hypothyroidism
Symptoms
Causes
Hormones
Hypothyroidism- too little thyroid hormone
Symptoms: weight gain and lethargy, slower metabolism, intolerance to cold
Goiter- lump in neck
Can be caused by iodine deficiency
Unable to make T3/T4 (Thyroid hormones)-> levels drop
Anterior pituitary secretes lots of TSH-> thyroid gland grows abnormally (no longer a problem due to iodized salt)
Hyperthyroidism
Symptoms
Causes
Hormones
Hyperthyroidism- too much thyroid hormone
Symptoms: high body temp, profuse sweating, weight loss, irritability, high blood pressure
Most common- Grave’s disease
Autoimmune
Antibodies bind TSH receptors
-> hyper secretion of thyroid hormone (TSH is constantly released)
Parathyroid
4 glands located in connective tissue surrounding thyroid
Secrete parathyroid hormone (PTH)
Controls blood Ca2+ levels
Purpose of parathyroid hormone
Controls blood Ca2+ levels
Low Blood Ca2+
- Parathyroid responds to stimulus
- Parathyroid hormone (PTH) released
- Bone releases Ca2+
- Kidneys reabsorb Ca2+
- Liver produces vitamin D -> helps absorb Ca2+ from intestines
- Raises blood Ca2+
High Blood Ca2+
Thyroid secretes calcitonin
In bone- inhibits Ca2+ removal
In kidneys- increases Ca2+ excretion through urine
Calcitonin is _________ to the parathyroid hormone
Antagonistic
The parathyroid deals with blood Ca2+ levels only if they are too ________
Low
The thyroid deals with blood Ca2+ levels if they are too _______
High
Adrenal glands structure + basic function
Small glands on top of each kidney
2 parts:
Central- adrenal medulla
Outer- adrenal cortex
Function as distinct glands
Both regulate metabolism, respond to stress
Adrenal Medulla
Neuroendocrine gland
Alarm reaction- fight-or-flight- reaction to short-term stress
Continuously secretes epinephrine, norepinephrine in small amounts
During stress, how is the adrenal medulla activated?
Hypothalamus activates adrenal medulla via nerve impulse
Adrenal medulla releases epinephrine, norepinephrine
When the adrenal medulla is activated, what are symptoms of the release of epinephrine and norepinephrine on the body?
-> More blood to brain, muscles, heart
-> Glycogen breakdown to glucose
-> Increase metabolic rate (up to 100%)
-> Increase O2 delivery- higher heart rate, stroke volume, breathing rate
Adrenal Cortex
Responds to chronic stress
Responds to endocrine signal rather than nervous
Stress-> hypothalamus secretes corticotropin-releasing factor (CRF)
-> AP releases ACTH (adrenocorticotropic hormone)
ACTH (from AP)
Stimulates adrenal cortex to produce corticosteroids
2 main types
Both steroid hormones synthesized from cholesterol
Glucocoticoids and Mineralicorticoids
Glucocorticoids
Promote glucose formation from non-carb sources (e.g. proteins)
Act on skeletal muscle- cause breakdown of muscle proteins
-> Glucose released into blood
Increased blood glucose under stress
Ensures adequate food for stressed cells
High levels- can suppress immune components
-> anti-inflammatory, used to treat arthritis, allergies
Mineralocorticoids
Regulate mineral metabolism
Maintain salt and water balance
Aldosterone- principle mineralocorticoid
Regulates H2O/Na+ balance in blood
Glucocorticoids and mineralocorticoids are secreted by the ______________.
Adrenal cortex
True or False: The anterior pituitary is a gland, whereas the posterior pituitary is nervous tissue
TRUE
______________ is an autoimmune disease that frequently results in hyperthyroidism.
Graves disease