Nakamura Human Physiology Lecture 10 Flashcards
(14 cards)
Thyroid gland
-Regulation of Basal Metabolic Rate by Thyroid Hormones
•Regulation of plasma Ca2+ levels by calcitonin and parathyroid hormone
-Thyroid gland located just below the larynx
-2 thyroid glands
-4 parathyroid glands (behind thyroid glands)
-secrete parathyroid hormone
•inside thyroid gland are Thyroid follicles that secrete thyroxine
•Parafollicular cells of thyroid secrete calcitonin
Regulation of thyroid hormone secretion
Hypothalamus (thyrotropin releasing hormone) TRH
Anterior pituitary (thyroid stimulating hormone) TSH
Thyroid (either results in growth of thyroid or thyroxine which goes back to anterior pituitary (negative feedback) inhibits responsiveness to TRH)
Diagram of production and secretion of thyroid hormones
Made in colloid of thyroid follicle
Iodide and perioxidase and H2O2 to iodine + thyroglobulin to monoiodotryosine (MIT) Diiodtryosine (DIT) to either
MIT+ and DIT to T3
Or
DIT+ and DIT to T4
Both bound to thyroglobulin
Production and secretion of thyroid hormones
•Follicular cells synthesize and secrete thyroglobulin into the colloid.
•I- (iodide: the negative ion of iodine) actively transported into the follicle and secreted into the colloid.
•Forming triiodothyronine (T3) or tetraiodothyronine (T4, thyroxine)
-3 iodine so for T3 or 4 for T4
•10-50X more T4 released but T3 is the biologically active form
Mechanism of thyroid hormone action
-Thyroxine (T4) is released into the blood
-binds to thyroxine-binding globulin for transport
●T4 crosses the cell membrane where it is converted to T3
-then carried to the nucleus by a cytoplasmic binding protein
T3 effects
.Fetus and neonate (an infant aged 1 month or less)
–Development of CNS and bone
•Adult
–Sets basal metabolic rate (BMR)
–Increases cellular respiration by activating mitochondria
–Heat production: Stimulates increased consumption of glucose, fatty acids and
Goiter
Caused by iodine deficiency
Regulation of plasma calcium
.Why is plasma Ca2+ level important?
•Calcitonin secretion from parafollicular cells of thyroid lowers plasma Ca2+ level
•Parathyroid hormone secretion from parathyroid glands increases plasma Ca2+ levels
•Influence on bone progenitor cells
Pancreas
-Endocrine portion consists of islets of Langerhans(1/3)
-also called tail of pancreas
•Alpha cells secrete glucagon
•Beta cells secrete insulin
Exocrine is about 2/3 and is enzymes
Regulation of insulin and glucagon secretion
- a high blood glucose concentration stimulates insulin and inhibits glucose secretion
- increase blood glucose, alpha cells decreased glucagon, beta cells increase insulin, increase cellular uptake and utilization of glucose, decrease glucose, negative feedback to blood - Glucagon also stimulates the breakdown of stored fat (lypolysis) into free fatty acids. The liver converts FFA to ketone bodies.
- low blood glucose concentration, alpha cells increased glucagon, beta cells decreased insulin, decreased cellular uptake of glucose, increase glycogenolysis, increase gluconeogenesis, increase glucose, negative feedback to blood
Metabolic balance of plasma glucose
Absorption of meal:
Increase insulin decrease glucagon, increase glucagon insulin ratio, formation of glycogen, fat, and protein. Blood: decrease glucose, amino acids, fatty acids, and ketone bodies
Fasting:
Decrease insulin increase glucagon, decrease insulin glucagon ratio, hydrolysis of glycogen, fat, and protein + gluconeogenesis and ketogenesis. Blood: increase glucose, amino acids, fatty acids, and ketone bodies
Diabetes
.Diabetes Mellitus (70% of population)
(Chronic high plasma glucose)
–Type I (Juvenile): Insulin dependent diabetes (IDDM)
-genetic, pancreas beta cell not healthy, doesn’t make enough insulin
–Type II (Adult): Non-insulin dependent diabetes (NIDDM)
-have insulin, just not enough. Obesity, less reception for insulin
-third type during pregnancy. Gastational?
Oral glucose tolerance test
- Ingest 100 g of glucose and monitor blood glucose levels (top) and plasma insulin levels (bottom) over several hours
- normal: glucose level rises the lowers and levels out quickly, insulin secretion
- diabetes: glucose in blood keeps rising because glucose can’t go into cell. No insulin secretion
Other health problems related to pancreas
-Circulatory System
•Nervous System
•Renal Failure
Diabetic shock: too much insulin, take insulin and not eat, unconscious because the brain is starved for glucose. Blood sugar too low
Diabetic coma: too little insulin, high plasma glucose, unconscious because brain cells cannot utilize glucose, brain cells shrink because under high osmolarity
