24: Endocrine 1 Flashcards
What is endocrinology?
The study of hormones, their receptors and their intracellular signalling pathways
What are hormones?
Hormones are chemical messengers produced in one location and transported to a second location (target cells) where they exert their effects. Hormones often reach their targets via the bloodstream. They act at low concentrations
What are the principal functions of the endocrine system>
Maintain homeostasis -a stable environment in the face of a changing external environment. Example; dehydration
Regulation of growth and development
Control energy storage and use
Mediate the body’s response to environmental cues
What occurs with an autocrine hormone
Hormone loops back to itself (target cell is same cell) to create a response
What occurs with a paracrine cell?
Cell A —> Hormone —> Cell B —> Response
What occurs with an endocrine cell?
Cell A –> hormone –> bloodstream –> hormone —> Cell B —> response
What occurs with a neurocrine cell?
Cell A releases hormone via the axon of the cell –> hormone moves along bloodstream —> Targe cell B –> Response
What is the chemical classification of peptides?
Less than 50 amino acids
What is the chemical classification of proteins?
More than 50 amino acids
What is the chemical classification of amines?
Derivatives of tyrosine (amino acids)
What is the chemical classification of steroids?
Synthesised from cholesterol
What is the chemical classification of prostaglandins?
Synthesised from arachidonic acid
Describe the synergistic effects of hormones
Thyroid hormone by itself releases little or no fatty acid to adipose tissue cells
Epinephrine by itself only releases a small amount of fatty acid to adipose tissue cells
However, when you combine epinephrine and thyroid hormone together, you get a large amount of fatty acids released
This is as thryroid hormone increases receptors for epinephrine
Describe the role of melatonin.
“the hormone of darkness”
The pineal gland releases melatonin into the blood stream, it then feeds back on SCN as a Zeitgaber (“time giver”) signal
Describe hypothalamic control of anterior pituitary hormone secretion
slides
Describe the pathway for positive control of growth hormone secretion
GHRH —> Growth hormone –> Liver –> Insulin-like growth factor 1 –> Somatosatin neurons (periventricular nucleus)
Describe the negative control of growth hormone secretion. (inhibition)
Somatostatin (SS) inhibits the release of growth hormone. Insulin growth factor 1 goes back to the GHRH
Describe the control of growth hormone secretion.
G protein coupled receptor
Slides
What are the indirect growth effects of growth hormone?
Stimulates the growth of bones, muscles and other tissues by stimulating cell division (mitogenesis) via insulin-like growth factor (IGF -1)
What is the direct effect of growth hormone
Stimulates protein synthesis (in muscle)
What are direct metabolic effects of growth hormone>? (2)
Increases blood glucose by stimulating glucose synthesis (in liver) and inhibiting cellular uptake of glucose
Increases triglyceride breakdown and free fatty acid mobilisation in adipose tissue
Describe the pattern of growth hormone secretion
-Growth hormone secretion is pulsatile and follows a diurnal pattern
Describe the control of hormones on the posterior pituitary gland
Slides
What hormones are secreted by the posterior pituitary gland?
- Vasopressin
- Oxytocin
What are roles of vasopressin?
- Is secreted in response to increased plasma osmotic pressure or decreased blood volume
- Inhibits urine production (diuresis) in the kidney
- Causes blood vessle contraction (vasoconstriction)
What are the roles of oxytocin?
- Acts upon the kidney to promote sodium excretion (natruiresis)
- Increases release of atrial natruiretic factor from the heart
- Contacts mammary ducts for milk let-down during suckling
- Causes uterine contraction during delivery
What causes diabetes insipidus?
Secretion of vasopressin is impaired or absent.
So the person would become dehydrated and require a lot of water
