Endocrine 2 Flashcards
Thyroid Gland
2 lobes lateral to trachea
Connected by isthmus
Produces T3, T4, calcitonin
Hypothalamus=>TRH (stim anterior pit)=>TSH (stim thyroid gland)=>T3, T4 (stim target organ)
T3 vs T4
First, iodine is added to the phenol ring resulting in monoiodotyrosine (if single site is iodinated) OR diiodotyrosine (if 2 sites iodinated)
The coupling of 2 diiodotyrosine forms T4 (4 iodides)
The coupling of monoiodotyrosine AND diiodotyrosine form T3 (3 iodides)
- Tyrosine + 1 iodine=monoiodotyrosine (MIT)
- Tyrosine + 2 iodine=diiodotyrosine (DIT)
- MIT + DIT = triiodothyronine (T3)
- DIT + DIT =thyroxine (T4)
T4 more abundant and longer-lasting than T3 (circulating hormone)
T3 is 4x more potent than T4 (cell-activating hormone)
Increase basal metabolic rate (BMR) and body temp (sodium pumps)
Increase CNS activity and muscular action (Na-K pump)
Enlargement of thyroid (hypothyroidism)
Lack of iodine in diet=thyroid gland tries to make up for this storage by growing larger=goiter
Hyper vs Hypothyroidism
Hyperthyroidism: effects of TH excess
• Weight loss, muscle tremors, excessive perspiration, nervousness and anxiety
Hypothyroidism: effects of TH deficiency
• Weight gain, muscle weakness, dry skin, fatigue
Graves’ disease –bulging eyes (hyperthyroidism)
Autoimmune disease=immune system attacks thyroid gland and the thyroid grows larger
• Immunoglobulins bind to thyrotropin receptors causing thyroid gland to grow and thyroid follicles increase synthesis of thyroid hormone
Hashimoto’s Thyroiditis (hypothyroidism)
Immune system attacks thyroid (autoimmune disease)=inflammation=leads to underactive thyroid gland
Cretinism (hypothyroidism)
Congenital thyroid deficiency in children=decrease T3 & T4=mental retardation and short appearance
Parathyroid glands
Implanted in posterior part of each lobe of thyroid gland
Secretes PTH: increases calcium and magnesium ions in blood and decrease phosphate ions in blood
Adrenal cortex
Produces cortisol, aldosterone and androgens
• consists of an inner medulla and outer cortex
• Medulla homologous to sympathetic ganglion, except that the postganglionic cells do not possess axons
• Cortex surrounding the medulla has 3 distinct layers each specialized to secrete diff category of hormones
Cortisol
• Secreted by adrenal cortex
• Influences metabolism
o Increase release of aa from muscle and fatty acids from adipose tissue
o Increase gluconeogenesis
o Decrease glucose utilization by cells
• Elevated levels of cortisol=less cartilage, bone, other connective tissue formation
• Anti-inflammatory effect, immunosuppressive
Cushing’s Syndrome
High level of cortisol=lead to obesity (especially in abdomen) and round face, make skin thinner (see redness)
Adrenal Medulla
Produce catecholamines (E, NE) which mimic effects of sympathetic NS Under direct control of sympathetic NS
Pancreas
- Posterior to stomach
- Mixed gland: exocrine (produces pancreatic juice), endocrine (produces insulin, glucagon)
- Endocrine part containing pancreatic islets (islets of Langerhans)
Alpha vs Beta cells
Alpha cells: Produce glucagon
• Increase breakdown of glycogen in muscles and liver
• Increase formation of glucose from fats
=>increase blood glucose
Beta cells: Produce insulin
• Increase movement of glucose from blood to most tissue cells
• Decrease breakdown of glycogen in muscle and liver
• Decrease formation of glucose from fat (fat storage)
=>decrease blood glucose
Delta cells vs F cells
Delta cells: produce somatostatin
o Serves to block secretion of both insulin and glucagon from adjacent cells
o Has neuroendocrine inhibitory effects
o Control flow of nutrients into and out of circulation (delay nutrient absorption by GI tract)
F cells, gamma cells, PP cells: secrete pancreatic polypeptide hormones
Causes satiety in:
o Brain=reduces appetite
o Digestive system=decreases rate at which food moves
Pineal Gland
Tiny pinecone small gland located near centre of brain b/w 2 hemispheres
• Gland large in children and begins to shrink at puberty
• Release melatonin: stim by darkness and inhibited by light
o Contributes to setting body’s biological clock
o Promotes sleepiness in small doses
o Might control onset of puberty
Acute Stress -Early Effects
NE & E
NE & E (from adrenal medulla/sympathetic nerve terminals) trigger increases in sympathetic responses:
Heart rate, respiration rates, BP, blood flow to skeletal muscles and heart, air flows to lungs and bronchial airways, skin blood vessels constricted, digestive functions supressed, E stim release of glucose into blood from liver/muscles, release fatty acids from lipid stores, inhibit insulin and stim glucagon secretion
Acute Stress -Early Effects
Vasopressin, E, CRH
Vasopressin, CRH (from hypothalamic neurosecretory cells) synergistically stim secretion of ACTH:
ACTH is co-secreted w B-endorphin from anterior pituitary
- promote POMC and increase analgesia and decrease pain perception
POMC: chopped by enzymes into several segments in adenohypophysis to produce diff hormones
- decreased activity in POMC cells = increased food intake and obesity
Acute Stress -Later Effects
Glucocorticoids (Cortisol)
Glucocorticoids (Cortisol) metabolic effects:
• Stim catabolism (breakdown) of pr in muscles and bones and stim liver to release aa to produce glucose
• Liver release newly formed glucose into blood
• Glucocorticoids oppose action of insulin
• Stim catabolism of fats –fatty acids used as alternative sort of energy
• Increase vasoconstriction stim by CA
• Inhibit secretion of gonadotropin (FSH/LH), TSH, GH
CRH acts as:
Neurohormone that stim ACTH secretion
NT (in other brain areas) stim SNS
Neuromodulator in amygdala and hippocampus responsible for memories of emotional changed events
In animal experiencing severe wound and loses blood:
Blood volume affects BP –BP ensures enough O2 and nutrients to brain and other essential organs
CA: increase BP by affecting heart and blood vessels
Vasopressin (pit. gland): increase water retention/reabsorption by nephrons
Aldosterone (adrenal cortex): increase sodium retention/reabsorption
These three=increase blood volume and BP
Cytokines
2 goals
Cytokines travel in blood=>hypothalamus=>stim CRH neurosecretory cells=>inform CNS about invading stressor
- Physiological responses of HPA axis (mobilization of energy stores) –to help animal fight infection
- GCH (at high conc) –inhibit production of agents that cause inflammation
Studies:
Removing pituitary gland from ordinary rats
High circulating CA levels –affect cytokine balance
Removing pituitary gland from ordinary rats (Lewis strain rats have impaired HPA axis and secrete little CRH)=respond excessively to stress=disrupt HPA=animal becomes susceptible to inflammation
Injecting GC into these animals –improve their resistance to inflammation
Fisher strain rats (respond excessively to stress) were highly resistant to inflammation b/c they secrete high levels of GCH
Patients w higher peak cytokine levels –neg impact neurologic outcome of injury (increase cognitive impairments)
Chronic Stress
Exposed to stressor for long periods or exposed repeatedly to stressors such as physiological stressors: Continuously constricted blood vessels, Retention of salt and fluid, Hypertension and cardiovascular maladies
• Prolonged exposure to GC =muscle wasting and bone thinning
• Suppression of immune system =susceptibility to infections/diseases
• Chronic activation of HPA axis=suppresses reproductive functions
• High levels of GC =atrophy of dendrites of neurons in hippocampus and hippocampus shrinkage=damage of part of brain important for memories/emotions
Stress can also lead to changes in other hormones (3)
Growth Hormone (GH): level increases during acute physical stress and repeated stressful situations
Prolactin: may increase in response to psychosocial stress in humans
Insulin: may decrease during stress
