Week 7 - Endocrine System Flashcards
What does the Endocrine System do?
Endocrine glands secrete hormones that travel in the bloodstream to target tissues
Allows cells to communicate with each other
Functions of the Endocrine System
- Metabolism
- Control of food intake and digestion
- Tissue development
- Ion levels
- Water balance
- Heart rate and blood pressure changes
- Control of blood glucose and other nutrients
- Control of reproductive functions
- Uterine contractions and milk release
- Immune system function
3 types of hormone secretion patterns
Chronic hormone secretion - Stable concentration is maintained in the blood stream over along period of time
Acute hormone secretion - Hormone secretion increases rapidly for a short time, usually is water soluble (e.g. insulin and epinephrine)
Episodic hormone secretion - Hormones are secreted at regular intervals and concentrations (e.g. insulin-secreting pancreatic beta cell)
3 different types of hormone regulation/activation and what each do
Neural activation - a neuron releases a neurotransmitter that signals the endocrine gland to release a hormone
Hormonal activation - a hormone (typically called a hormone-releasing factor) will stimulate an endocrine organ/gland to release a different hormone
Humoral control - the control of hormone release in response to changes in extracellular fluids such as blood or the ion concentration in the blood e.g. rise in blood glucose stimulates pancreas to release insulin
Two major mechanisms allow homeostatic levels of hormones in the body
Positive and Negative feedback systems
Positive feedback system
Self-propagating system where the hormone stimulates it’s target cell and also promotes synthesis and secretion of the hormone
Negative feedback system
Self-limiting system where the hormone is inhibited by itself when there is adequate hormone levels in the blood
What happens when a cell down regulates it’s receptor response
This occurs when the cell decreases the number of receptors it has on the cell membrane
What happens when a cell up regulates?
An increased rate of receptor synthesis in the cell allows for more receptor sites for hormones
Name the glands that make up the Endocrine system (10)
Hypothalamus, Pituitary, Pineal gland, Parathyroids, Thyroid, Thymus, Pancreas (islets), Adrenals, Testes and Ovaries
Major control site of the nervous and endocrine system
Hypothalamus
Where does the hypothalamus receive it’s information? (3)
Hormones, emotions and the CNS
The hypothalamus is connected to the pituitary gland by an extension called:
infundibulum
Growth hormone-releasing hormone (GHRH)
Structure, Target tissue and Response
Peptide, Anterior pituitary cells that secrete growth hormone, increased growth hormone secretion
Growth hormone-inhibiting hormone (GHIH), or somatostatin
Structure, Target tissue and Response
Small peptide, AP cells that secrete GH, decreased GH secretion
Thyrotropin-releasing hormone (TRH)
Structure, Target tissue and Response
Small peptide, AP cells that secrete TSH, increased TSH secretion
Corticotropin-releasing hormone (CRH)
Structure, Target tissue and Response
Peptide, AP cells that secrete Adrenocorticotropic hormone, increased ACTH hormone secretion
Gonadotropin-releasing hormone (GnRH)
Structure, Target tissue and Response
Small peptide, Anterior pituitary cells that secrete luteinizing hormone and follicle-stimulating hormone, increased LH and FSH hormone secretion
Prolactin-releasing hormone (PRH)
Structure, Target tissue and Response
Unknown, AP cells that secrete prolactin, increased prolactin secretion
Prolactin-inhibiting hormone (PIH)
Structure, Target tissue and Response
Dopamine (amino acid derivative), AP cells that secrete prolactin, decrease prolactin secretion
What type of tissue is the posterior pituitary gland made of
Neural tissue
What is another name for the posterior pituitary gland
Neurohypophysis
What structure connects the hypothalamus to the pituitary gland?
Infundibulum
Specialised blood portal system between hypothalamus and AP
Hypothalamohypophysial portal system
Posterior pituitary gland steps from stimuli to target tissue (4)
- Stimuli from the nervous system causes an increase or decrease in action potentials from hypothalamic neurons
- Action potentials move through axons down the hypothalamohypophysial tract to the posterior pituitary.
- Causes the release of stored neurohormones from the pituitary gland
- Neurohormones circulate in the blood and travel to their target tissues
Posterior Pituitary Hormones
Antidiuretic Hormone (ADH) or Vasopressin, Oxytocin
ADH
Stimulation (2 types), Target Tissue, Response
Stimulation: Osmoreceptors respond to changes in blood osmolality.
Increase in osmolality → increases action potentials in both osmoreceptors and ADH neurosecretory neurons → increasing ADH secretion
Stimulation: Baroreceptors respond to changes in blood pressure
Decrease in blood pressure → increases action potentials frequency → increasing ADH secretion
Target tissue: kidneys
Response: Kidneys retain more water to decrease osmolality or increase blood pressure
The majority of anterior pituitary hormones are what type
Tropic hormones which stimulate the secretion of other hormones from other endocrine glands or organs
Name the Anterior Pituitary Hormones
Growth Hormone (GH), Thyroid-Stimulating Hormone (TSH), Adrenocorticotropic Hormone (ACTH), Luteinizing Hormone (LH), Follicle-Stimulating hormone (FSH), Prolactin
GH Stimulation, target tissue, and response
Stimulation: Stressors (low blood glucose) stimulates GH releasing hormone from hypothalamus, increases the secretion of GH by AP
Target tissue: most tissues
Response: Stimulates growth, regulates metabolism, regulates blood nutrient levels during fasting and post meal
What type of feedback does GH have
Negative feedback and GH inhibiting hormone decreases the secretion of GH
TSH Stimulation, target tissue, and response
Stimulation: Controlled by the secretion of Thyroid releasing hormone (TRH) and thyroid hormone
Target tissue: Thyroid gland
Response: Stimulates the synthesis and secretion of thyroid hormone
How is the TSH inhibited
It is inhibited by the presence of thyroid hormone
Negative feedback
ACTH stimulation, target tissue and response
Stimulation: Released in response to corticotropin-releasing hormone (CRH)
Target tissue: Adrenal cortex
Response: Increased secretion of glucocorticoid hormones
