BIOM PART TWO - Lecture 2 Flashcards
How is the pituitary connected to the hypothalamus?
Through the infundibulum (stalk)
What is the whole pituitary gland protected by?
Bone
What is the Anterior Pituitary/Adenohypophysis?
An endocrine gland
What is the Posterior/Neurophysis?
Extension of neural tissue
What does Dopamine (PIH) inhibit?
Secretion of prolactin
What does Prolactin releasing hormone do?
Stimulate the release of prolactin
What does Thyrotropin releasing hormone do?
Regulates secretion of thyroid stimulating hormone (TSH)
What does Corticotropin Releasing Hormone do?
Regulates secretion of adrenocorticotropin hormone (ACTH)
What does Somatostatin do?
Inhibit secretion of Growth Hormone (GH)
What does Growth Hormone Releasing Hormone do?
Stimulate secretion of GH
What does Gonadotropin-Releasing Hormone do?
Regulates secretion of gonadotropin-releasing hormones, luteinizing hormone (LH), and follicle stimulating hormone (FSH)
In the Hypothalamic - Pituitary Adrenal Cortex, what does the Hypothalamus secrete?
Corticotropin Releasing Hormone
What does CRH stimulate?
The pituitary gland to stimulate ACTH release
What does ACTH stimulate?
The Adrenal Gland to release Glucocorticoid
What is Cortisol?
A glucocorticoid - chronic stress hormone
Where does CRH synthesis and release come from?
The hypothalamic PVN
What is Central Stimulatory Control?
- Noradrenergic
- Stimulates pre-proCRH gene and protein expression (196AA)
- Processed top CRH (41 AA)
- Stimulates pulsatile release of CRH
What are the inhibitory influences?
Physiological levels of cortisol inhibit release of CRH (and possibly inhibit pre-prOCRH gene expression)
What type of cells is CRH produced from?
Parvocellular neuroendocrine cells within the PVN
Where is CRH released at?
The median eminence (base of the brain) from neurosecretory nerve terminals, into blood vessels in the hypothalamic pituitary portal system
What do blood vessels carry?
The CRH peptides to anterior lobe of the pituitary, where they stimulate corticotropes to secrete ACTH
What do the POMC peptide family release?
ACTH and MSH
What does ACTH regulate?
Adrenal Cortex function
What is MSH?
Melanocyte Stimulating Hormone (skin pigmentation in response to UV radiation)
What is End - B endorphin?
Analegesic roles in CNS
What is Enk: enkephalin?
Analgesic roles in fetus
What are MC3, 4, 5 - receptors?
For hypothermia, hypotension, feeding behaviour, and appetite
What are Convertases?
Enzymes that cleave POMC
(Different convertases give rise to different products)
What are the Adrenal Glands made up of?
2 embryologically distinct tissues that merged during development
What does the Adrenal Cortex secrete?
Secretes steroids (corticosteroids) such as Glucocorticoids, Mineralcorticoids, and Sex Steroids
What are Glucocorticoids controlled by?
Cortisol - Controlled by ACTH
What are Mineralocorticoids controlled by?
Aldosterone - controlled by renin - angiotensin system
What are Sex Steroids controlled by?
Testosterone - controlled by ACTH
What is the Adrenal Medulla?
Modified sympathetic ganglia, secretes catecholamines (epinephrine)
What does Cortisol protect against?
Hypoglycemia (low blood sugar)
What does Cortisol promote?
Gluconeogenesis (increase blood sugar)
What does Cortisol play a role in?
The immune system (suppresses immune system, regulates inflammatory response - glucocorticoids used clinically as anti-inflammatory agents)
What does Cortisol cause a breakdown of?
Skeletal muscle for glucogenesis
How can cortisol affect brain function?
Through memory, learning and mood
What is Cushing’s syndrome?
Primary hypercortisolism (high blood corticosteroids)
How can Cushing Syndrome be caused?
By taking high levels of glucocorticoid drugs, or diseases that result in excess cortisol ACTH, or CRH
What does Cushing syndrome cause?
Changes in carbohydrate and protein metabolism, hyperglycemia, hypertension and muscular weakness
What do metabolic problems give rise to?
Puffy appearance, CNS disorders (depression, decreased memory and learning)
What is Cushing DISEASE?
Secondary Hypercortisolism
What is Secondary Hyperthyroidism?
Pituitary-dependent, such as a tumour in the pituitary gland that produces large amounts of ACTH, causing adrenals to make excess cortisol
What do ACTH levels lower in?
Cushing’s Syndrome
How would you treat Cushing’s?
Surgically remove pituitary or adrenal gland (depending on source)
Medical Management of signs (insulin for diabetes, antihypertensives for BP)
What is Addison’s disease?
Primary Hypocortisolism (too low of cortisol)
What is Addison’s disease caused by?
Adrenal Insufficiency caused by genetic, autoimmune, destruction of adrenal cortex
How can Addison’s disease be acquired?
Due to Hugh-dose steroids given for >1 week (suppresses CRH and ACTH which suppresses adrenal gland)
What are the symptoms of Addison’s disease?
Hair loss, blurry vision, decreased appetite , depression
What is Adrenal Cortisol secretion?
Continuous, pulsatile, circadian release
What is Pituitary Pars Intermedia Dysfunction?
Impaired pituitary (hyperplasia and hypertrophy of pars intermedia)
What does PPID lead to?
Increased secretion of cortisol by adrenal glands resulting in high blood glucose and suppression of immune system
What are common signs of PPID?
Hypertrichosis (excessive hair growth)
Abnormal hair coat including patches of long hair on legs, wavy hair on neck
Muscle Atrophy
Excessive Sweating
Formation of Fat Pads on Top of Neck, tail head
Pot-Bellied Appearance
What is the Diagnosis of PPID?
Measure resting (basal) ACTH and fasting insulin
What is the Treatment for PPID?
Medication - Acts on pituitary gland to decrease circulating ACTH
Management - Exercise, Weightloss, Limit sugar in diet
What is the general overview of the Hypothalamus Pituitary Thyroid Axis?
The hypothalamus releases TRH which stimulates the Anterior Pituitary Gland to release TSH which acts on the Thyroid Gland to produce T3 and T4
Where is the Thyroid Gland?
Just below larnyx (voice box), on either side of the trachea (lateral to the first 3-8 tracheal rings)
What are the 2 lobes connected by?
Isthmus (fibrous in cows, and horse)
What is the Thyroid gland?
The largest purely endocrine gland
What do follicles of the Thyroid Gland do?
Take up iodide (I-) from the blood
What happens in the Colloid of the Thyroid Gland?
Thyroid Peroxidase Enzyme (TPO) help attach iodide to tyrosine residue in thyroglobulin
What is Thyroglobulin made by?
Follicular cells long peptide chain with lots of tyrosine side chains)
Found in Colloid
What is Iodide brought from blood into?
Follicular cells by sodium iodide transporter, then into colloid by transporter called pendrin
What does TPO remove?
A electron from iodide to produce iodine
What does Iodide bind?
Tyrosine residues in thyroglobulin, creating 2 outcomes
What are the two outcomes?
Attachment of 1 Iodine on a tyrosine ring produces MIT (monoiodotyrosine)
Attachment of 2 Iodines on a tyrosine ring produces DIT (diiodotyrosine)
What do enzymes in the colloid do?
Modify the structures of MIT and DIT, joining them together
What are the joined together molecules?
T3 (triiodothyronine) or T4 (tetraiodothyronine)
What are T3 and T4 still attached to?
The thyroglobulin backbone
What is Thyroglobulin taken back up by?
Follicular Cells and cut, separating T3 and T4 upon stimulation of TSH
Where are T3 and T4 secreted into?
Bloodstream (bound to carrier proteins)
What is 99% of Thyroid Hormones in Blood Circulation bound to?
Plasma carrier protein called thyroxine-binding globulin (TBG)
What are free fractions?
Only type of thyroid hormones biologically active (must lose carrier protein to elicit effects)
What is the pathway of Thyroxine?
T4 + protein carrier
T4 –> T3
T3 uses binding proteins to enter nucleus
Hormone-receptor complex binds DNA
New mRNA
Protein
Response
