Endocrine 2

Question 1

Thyroid Gland

Answer 1

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)

Question 2

T3 vs T4

Answer 2

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)

Question 3

Enlargement of thyroid (hypothyroidism)

Answer 3

Lack of iodine in diet=thyroid gland tries to make up for this storage by growing larger=goiter

Question 4

Hyper vs Hypothyroidism

Answer 4

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

Question 5

Graves’ disease –bulging eyes (hyperthyroidism)

Answer 5

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

Question 6

Hashimoto’s Thyroiditis (hypothyroidism)

Answer 6

Immune system attacks thyroid (autoimmune disease)=inflammation=leads to underactive thyroid gland

Question 7

Cretinism (hypothyroidism)

Answer 7

Congenital thyroid deficiency in children=decrease T3 & T4=mental retardation and short appearance

Question 8

Parathyroid glands

Answer 8

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

Question 9

Adrenal cortex

Answer 9

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

Question 10

Cortisol

Answer 10

• 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

Question 11

Cushing’s Syndrome

Answer 11

High level of cortisol=lead to obesity (especially in abdomen) and round face, make skin thinner (see redness)

Question 12

Adrenal Medulla

Answer 12

Produce catecholamines (E, NE) which mimic effects of sympathetic NS
Under direct control of sympathetic NS

Question 13

Pancreas

Answer 13

• Posterior to stomach
• Mixed gland: exocrine (produces pancreatic juice), endocrine (produces insulin, glucagon)
• Endocrine part containing pancreatic islets (islets of Langerhans)

Question 14

Alpha vs Beta cells

Answer 14

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

Question 15

Delta cells vs F cells

Answer 15

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

Question 16

Pineal Gland

Answer 16

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

Question 17

Acute Stress -Early Effects

NE & E

Answer 17

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

Question 18

Acute Stress -Early Effects

Vasopressin, E, CRH

Answer 18

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

Question 19

Acute Stress -Later Effects

Glucocorticoids (Cortisol)

Answer 19

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

Question 20

CRH acts as:

Answer 20

Neurohormone that stim ACTH secretion
NT (in other brain areas) stim SNS
Neuromodulator in amygdala and hippocampus responsible for memories of emotional changed events

Question 21

In animal experiencing severe wound and loses blood:

Answer 21

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

Question 22

Cytokines

2 goals

Answer 22

Cytokines travel in blood=>hypothalamus=>stim CRH neurosecretory cells=>inform CNS about invading stressor

1. Physiological responses of HPA axis (mobilization of energy stores) –to help animal fight infection
2. GCH (at high conc) –inhibit production of agents that cause inflammation

Question 23

Studies:
Removing pituitary gland from ordinary rats
High circulating CA levels –affect cytokine balance

Answer 23

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)

Question 24

Chronic Stress

Answer 24

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

Question 25

Stress can also lead to changes in other hormones (3)

Answer 25

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