C10 Endocrine system Flashcards
(29 cards)
What are the main organs of the endocrine system
Pineal glands
Hypothalamus
Pituitary gland
Thyroid gland
Parathyroid gland
Thymus gland
Adrenal gland
Pancreas
Ovary/testis
Main function of pituitary gland
Produce 9 major hormones that:
1. regulate body functions
2. Regulate the secretions of other endocrine glands
Main function of hypothalamus
regulates secretion of anterior pituitary
Main function of thyroid gland
Stores hormones
Main function of pancreas
Regulation of insulin secretion
Describe the structure of the pituitary gland
- Posterior pituitary
- extension of the nervous system via the infundibulum - Anterior pituitary
- Develops from the embryonic oral cavity
What is a hormone
A chemical messenger
- produced in small quantities
- transported some distance in circulatory system
- acts on target tissue elsewhere
Acute hormone secretion
Sudden release due to stimulus
Chronic hormone secretion
Small variations over long periods
Episodic hormone secretion
Eg. Estrogen & progesterone during the menstrual cycle
How do hormones work to control homeostasis
Target cells respond to a hormone because they have the correct receptor
- hormones promote homeostasis by altering activity of the body cell
Process of negative feedback
- Anterior pituitary secretes a tropic hormone which travels in blood to target endocrine cell
- Hormone from target endocrine cell travels to its target
- Hormone from target endocrine cell has negative feedback effect on hypothalamus and anterior pituitary to decrease secretion of tropic hormone
Example of negative feedback
- Stress/hypothermia causes TRH to be released from neurons within the hypothalamus –> passes through the hypothalamohypopysial portal system to the anterior pituitary
- TRH causes cells of the anterior pituitary to secrete TSH -> pass through general circulation -> thyroid gland
- TSH causes increased synthesis and release of T3&T4 into the general circulation
- T3&T4 acts on target tissue to produce a response
- T3&T4 also has inhibitory effect on the secretion of TRH from hypothalamus & TSH from anterior pituitary
Process of positive feedback
- Anterior pituitary secretes a tropic hormone which travels in blood to target endocrine cell
- Hormone from target endocrine cell travels to its target
- Hormone from target endocrine cell has positive feedback effect on hypothalamus and anterior pituitary to increase secretion of tropic hormone
Example
- Stretch of the uterus and the uterine cervix/stimulation of the breast’s nipples. increase action potential in axons of oxytocin-secreting neurons
- APs are conducted by sensory neurons from the uterus & breast to the spinal cord & up ascending tracts to the hypothalamus
- APs are conducted by axons of oxytocin-secreting neurons in the hypothalamohypophysial tract to the posterior pituitary -> increase oxytocin secretion
- Oxytocin enters the circulation, increasing contractions of the uterus & milk ejection from lactating breast
What hormones are released from the anterior pituitary
- Growth hormones (GH)
- THyroid stimulating hormones (TSH)
- Adrenocorticotropic hormones (ACTH)
- Melanocyte-stimulating hormone (MSH)
- Luteinising hormone (LH)
- Follicle-stimulating hormone (FSH)
- Prolactin
Growth hormone
GH
acts on most cells of the body, overall metabolism & growth
thyroid-stimulating hormones
TSH
stimulates thyroid to secrete T3 & T4
Adrenocorticotropic hormone
ACTH
stimulates adrenal cortex to secrete cortisol & aldosterone
Melanocyte-stimulating hormone
MSH
Causes melanocytes to produce more melanin
Luteinising hormone & Follicle stimulating hormone
LH & FSH
regulate production of gametes & reproductive hormones
Prolactin
role in milk production (lactation)
What hormones are released by the posterior pituitary
- Antidiuretic hormone (ADH)
- Oxytocin
Antidiuretic hormone (ADH)
stimulates the reabsorption of sodium & water from nephrons
