Download Hormonal control of blood glucose

Hormonal control of blood glucose
In the GI tract, 80% of all carbohydrate is digested to glucose
Basically:
Glucose
Used for ATP production
Glycogen
Used for glucose storage
Insulin Effects on Muscle and
Fat Tissue
• Insulin initiates transfer of glucose
transporters to cell membrane
•  blood glucose
•  production of glycogen
Effects in Muscle & Fat
Glycogen synthesis
Glucose
transporter
glucose
SNARE dependent
transport
Glucose
transporter
Insulin
storage
vesicle
In the Liver
• insulin stimulates the synthesis of an
enzyme (glucokinase)
• Required to ‘trap’ glucose in the cell
• initiates glycogen production
Effects in Liver
GLUT2
Glycogen synthesis
Glucose
transporter
glucose
X
glucose
Glucose 6-phosphate
glucokinase
‘trapped’
Other hormones
• Glucagon
– Secretion stimulated by low blood glucose
– Activates enzymes for gluconeogenesis and
glycogenolysis
– Leads to  blood glucose levels
• Somatostatin
– Regulates secretion of insulin and glucagon
Glucose Regulation Summary
• Endocrine pancreas
• Secretion of several hormones important
for blood glucose regulation
• Insulin  glucose uptake and storage
– Different effects on liver and muscle & fat
• Glucagon  glucose production
Thyroid and Parathyroid
Thyroid
• Thyroid Hormones
– Produced in the follicle cells of the thyroid
– T3 triiodothyronine
– T4 thyroxine
• Both require iodine to be produced
• Thyroid hormones increase metabolic rate
in muscle, heart, liver and kidney
– Produces heat
• Lack of iodine during development
Stunted growth, called cretinism
Enlargement of the thyroid, called goiter
Due to lack of thyroid hormones and
overstimulation of the thyroid gland by
TSH
Because no negative feedback
Control of Thyroid
Cold
If –’ve feedback lost
Too much TSH
Get goiter
Hypothalamic neurons
Thyroid releasing hormone (TRH)
Anterior Pituitary
Thyroid Stimulating Hormone (TSH)
Thyroid
Release of thyroid hormones – T3 and T4
Control of extracellular Calcium
•
Two hormones
1. Parathyroid hormone
2. calcitonin
Parathyroid
• Low blood Ca++
stimulates release of
parathyroid hormones
• Act to increase blood
Ca++ by
–  Ca++ release from bone
–  Ca++ absorption in gut
–  Ca++ reabsorption in
kidney
Calcitonin
• Produced in parafollicle cells of the
thyroid gland
• High Blood Ca++ stimulates
release of calcitonin
• Act to decrease blood Ca++ by
– ↓ Ca++ release from bone
– ↓ Ca++ reabsorption in kidney
High Ca++
Low Ca++
Calcitonin
Mobilize Ca
From Bone
Parathyroid hormone
Reabsorb Ca
In the kidney
Increase absorption
of Ca from intestine
• Summary
– Blood glucose regulation
– Thyroid gland
– Calcium regualtion by parathyroid and
calcitonin
• What to do next Tuesday?
– review