Endocrinology Flashcards
(52 cards)
What is homeostasis?
Maintenance of conditions in the internal environment within established tolerance limits
What is the order of a feedback system?
Stimulus
Controlled condition
Receptors
Control center
Effectors
Response
What are circulating hormones?
Chemical messengers secreted by endocrine glands which diffuse info the blood and are carried a large distance by cells
What are local hormones?
Produced by many tissues and serve as a means of local control. They diffuse between cells rather than being transported in the blood
e.g paracrines, autocrines
What is the difference between the nervous system and endocrine system?
Nervous system uses neurotransmitters to directly influence neuronal activity and behaviour
Endocrine system uses hormones to directly and indirectly influence neuronal activity and behaviour, as well as other bodily systems
What are the similarities between hormones and neurotransmitters?
Hormones are produced in endocrine cells and stored there later for release. Neurotransmitters are stored in pre-synaptic neurons until they are released
Hormones bind with specific receptors. Neurotransmitters bind with specific receptors
Hormones bind with receptors on surface or inside cells. Neurotransmitters bind to receptors on surface
Hormones and neurotransmitter binding triggers activities within the cell
What are the differences between neurotransmitters and hormones?
Neurotransmitters travel over synaptic space to recieving neuron. Hormones travel in blood to different locations in the body
Hormonal communication is slower than neurotransmission
What are the functions of the endocrine system?
Maintain a constant internal environment in the face of external challenges
Regulate metabolism and energy balance
Help regulate involuntary muscle contractions and secretions by glands
Guide growth and development
Contribute to the control of reproductive function
How do hormones work?
Hormone binds to receptor for that specific hormone on the cell membrane or inside the cell
Activated receptor-hormone complex alters the gene expression within the cell nucleus
Newly formed mRNA directs the synthesis specific proteins on ribosomes
New proteins alter the cells activity
What are secretions of hormones controlled by?
Signals from the nervous system
Changes in blood composition
Other hormones
What is the master control centre of the endocrine system?
Hypothalamus, it regulates the posterior and anterior pituitary gland
What are the features of the posterior pituitary?
Composed of nervous tissue
Secrets hormones made in the hypothalamus
What are the features of the anterior pituitary?
Composed of glandular tissue
Hypothalamus exerts control over the anterior pituitary by secreting releasing hormones or inhibiting hormones
What do the thyroid hormones, T3 and T4, regulate?
Metabolic rate- increase basal metabolic rate
- use extra oxygen to produce ATP and heat
Cellular metabolism- stimulate protein synthesis
- increase use of glucose
Growth and development- accelerate body growth
What does the adrenal gland hormone cortisol do?
Stimulates glucose production to provide resistance to stress
Depresses immune response and decreases inflammation
What does the adrenal gland hormone aldosterone do?
Involved in regulation of filtration rate in kidney as part of the renin-angiotensin negative feedback system
What does the adrenal gland hormone epinephrine do?
It is a norepinephrine, and is released in response to stress
Increases blood pressure, dilates airways, increases blood glucose, decreases digestion
What is the difference between endocrine and exocrine glands?
Endocrine glands are ductless glands where secretions
pass into the blood
Exocrine glands are open to the outside medium through ducts
How is Ca2+ regulated in the blood?
High level of Ca2+ in the blood stimulates thyroid gland parafolicular cells to release calcitonin (CT)
CT promoted deposition of blood Ca2+ into home matrix, which decreases blood Ca2+ level
Low level, of Ca2+ in blood stimulates parathyroid gland principal cells to release parathyroid hormone (PTH)
PTH promotes release of Ca2+ from bone matrix into blood and retards loss of Ca2+ in urine, which increases blood Ca2+ level
PTH also stimulates the kidneys to release calcitriol
Calcitriol stimulates increased absorption of Ca2+ from foods in the gastrointestinal tract, which increases blood Ca2+ level
Which repeats the cycle
How does the body respond to low blood glucose?
Low blood glucose stimulates the release of glucagon from alpha cells
Glucagon acts on liver cells to- convert glycogen to glucose
- form glucose from lactic acid and AA (gluconeogenesis)
Glucose released by hepatocytes raises blood glucose level to normal
How does the body respond to high blood glucose?
High blood glucose stimulates release of insulin by beta cells
Insulins acts on various body cells to:
-accelerate facilitated diffusion of glucose into cells
-speed up conversion of glucose into glycogen (gluconeogenesis)
-increase uptake of amino acids and increase protein synthesis
-speed synthesis of fatty acids (lipogenesis)
-slow gluconeogenesis
-slow glycogenolysis
The blood glucose level falls
If blood glucose continues to fall, hypoglycemia inhibits release of insulin
How is blood water concentration controlled in the body?
If there is high osmotic pressure (blood water concentration) osmoreceptors in the hypothalamus will detect this
Nerve impulses are sent to Hypothalamus and posterior pituitary gland
Increased release of ADH into the blood
Principal cells become more permeable to water, which leads to increased water reabsorption
Blood water concentration increases
How does the body regulate thyroid hormones T3 and T4?
If low levels of T3 and T4, or low, metabolic rate, this stimulates the release of thyrotropin releasing hormone (TRH)
TRH carried by hypophyseal portal veins to anterior pituitary gland, stimulates release of thyroid-stimulating hormone (TSH) by thyrotrophs
TSH released into blood stimulates thyroid follicular cells
T3 and T4 released into blood by follicular cells
Leads to normal blood levels of T3 and T4, or normal metabolic rate
Elevated T3 and T4 inhibit release of TRH and TSH
What is the growth hormone?
Somatotrophin
It is an anterior pituitary hormone
No specific target gland hormone
