Major endocrine glands (8)
Pineal Pituitary Thyroid Thymus Adrenal Pancreas Ovary Testes
Functions of the endocrine system (4)
- Regulates metabolism
- Regulates fluid and electrolytes
- Counteracts the effects of stress
- Regulates growth
Gland secretion patterns
Endocrine - released into bloodstream
Autocrine - acts on same cell that releases it
Paracrine - released into surrounding tissue
Amines
Catacholamines and thyroid hormones
Proteins and peptides
Insulin, calcitonin, oxytocin, GH
Steroid
Mineralocorticoids, glucocorticoids and gonadocorticoids
Lipid-based so can diffuse into cells
Hormones are secreted in response to…
Level of some constituent of the blood
Other hormones
Stimulation of nerves
Patterns of interaction
Antagonistic - stop an effect
Permissive - allow things to happen
Synergistic - more than the sum of their parts
Hypothalamus
Interface between neuronal and hormonal activity
Secretes regulatory hormones which control hormone release from pituitary gland
Neural control over endocrine cells of adrenal gland
Posterior pituitary
Secretes ADH and oxytocin
Anterior pituitary
Secretes releasing and inhibitory hormones
e.g. TSH, GH, FSH, LH, growth hormone, prolactin
3 levels of the adrenal cortex
Zona glomerulosa produces mineralocorticoids (kidney and fluid)
Zona fasciculata produces glucocorticoids (stress)
Zona reticularis produces gonadocorticoids
Adrenal medulla
Adrenaline and noradrenaline are released after firing of splancnic nerve from hypothalamus
Adrenal disease (3)
Cushings - excessive ACTH
Hypoadrenocorticism/Addison’s disease
Pheochromecytoma - tumour of chromaffin cells
Hormone releasing cells in the pancreas
Alpha cells secrete glucagon
Beta cells produce insulin
Gamma cells produce pancreatic peptide
Delta cells produce somatostatin
When blood glucose increases…
- Insulin is secreted
- Binds to receptor outside cell
- Receptor and insulin are endocytosed
- Glucose transport proteins are inserted into the cell membrane
- Glucose is internalised and blood glucose drops
When blood glucose decreases…
- Glucagon is secreted
- Stimulates breakdown of glycogen in liver and skeletal muscle
- Glycogen becomes glucose
Type I diabetes
Pancreas doesn’t secrete insulin well
Type II diabetes
Problems with insulin receptors
Two forms of thyroid hormone
T3 - tri-odo thyroxine
T4 - thyroxine
Physiological effects of thyroid hormone (6)
Bind to mitochondria to increase ATP production
Activate genes that stimulate energy use
Increase metabolic rate
Lipolysis
Protein synthesis
Enhance effects of some neurotransmitters
Regulation of thyroid hormones (negative feedback loop)
- Hypothalamus releases TRH
- Pituitary releases TSH
- Thyroid gland produces T3 and T4
- Blood levels of T3 and T4 are normal
- T3 and T4 bind to proteins
- As levels drop, binding proteins release T3 and T4
- As levels increase again, hypothalamus inhibits pituitary
Treatment for hypothyroidism
HRT - l-thyroxine
Adverse effects - abnormal heart rhythms, osteoporosis
