Endocrine System Flashcards
(36 cards)
What are the 8 endocrine glands
Pituitary gland and hypothalamus, Pineal glands, Thyroid glands, Parathyroid glands, Adrenal glands, Pancreatic islets, Organs with secondary endocrine functions and local hormones
What are hormones and what do they do?
They are chemical messengers and influence metabolic activity
What do hormones control and regulate?
Reproduction. Growth and development. Electrolyte, water and nutrients balance of the blood. Regulation of metabolism. Mobilisation of body defences.
How do hormones have an effect?
Hormones are chemicals which instruct cells to perform or carry out certain functions. Under the influence of hormones cells may manufacture and release other chemical substances into the body, they may also increase or decrease their absorption/release of certain chemical substances across the cell membrane.
How do non-steroid (water soluble) hormones pass through the cell membrane?
- Non-steroid hormone and Receptor protein
- Merge in the cell membrane
- Activates the production of chemicals
- Chemicals then activate the enzymes
- Enzymes are released into the cell
How does steroid hormones
1.Steroid hormone goes through the cell membrane
2. Then binds with the steroid receptor
3. Steroid receptor and hormone moves to the nucleus
4. Steroid complex binds to DNA which produces another chemical protein.
How does the nervous system control the breakdown of hormones?
Initiates responses rapidly
Short-duration responses
Acts via action potential and neurotransmitters
Acts at specific locations determined by axon pathways
Neurotransmitters act over short distances
How does the Endocrine system control the breakdown of hormones?
Initiates responses slowly
Long-duration responses
Acts via hormones released into the blood
Acts at diffuse locations – targets can be anywhere blood can reach
Hormones act over long distances
What are hormones?
Long-distance chemical signals that travel in lymph or blood
What do endocrine glands do?
ductless, release hormones into the surrounding tissue fluid.
What do exocrine glands do?
have ducts that carry secretions to a membrane surface.
How endocrine organs are stimulated to produce hormones?
Humoral Stimulus – Hormone released as a result of altered level of a certain ion or nutrient.
Nervous stimulus – The nervous system stimulates an organs to release hormones.
Hormonal Stimulus – Sometimes hormone release is caused by another hormone.
Edocrine glands - Hypothalamus
Pituitary gland - where is it and what does it do?
In the brain
- The pituitary and the hypothalamus act as a unit.
Regulate activities of most of the endocrine glands.
- Anterior and posterior pituitary gland in different ways.
Anterior pituitary gland, how does it work?
Hypothalamus and the anterior pituitary are linked by capillaries called Pituitary portal system (PPS)
PPS transports to the AP, allowing easy passage of hormones into the bloodstream - also transports oxygen and nutrients.
Posterior pituitary gland, how does this work?
Formed from nervous tissue - nerve cells supported by glial cells (pituicytes).
Posterior pituitary hormones are synthesised in the nerve cell bodies, transported along the axons and stored in vesicles.
Pineal gland - where is it and how does it work?
In your brain
Secretion is suppressed by daylight; increased during darkness.
Melatonin is the hormone secreted by the pineal gland.
Thyroid gland - where is ti and how does it work?
It is situated in the neck in front of the larynx and trachea.
Spherical follicles formed from cuboidal epithelium. They secrete and store colloid
Colloid contains precursor molecules of thyroid hormones. (Thyroxine T4 and
tri-iodothyronine T3)
What does T3 and T4 do?
Increase metabolic rate and heat production.
Regulates metabolism of fats, carbohydrates and proteins.
Parathyroid gland - how many do you have, where is it and what does it do?
Four parathyroid glands embedded in the posterior surface of the thyroid gland.
PTH secretion increases blood calcium levels by:
-Releasing calcium stored in bone into the blood stream
-Increasing calcium reabsorption from the renal tubules. More calcium is reabsorbed back into the blood during the formation of urine.
PTH and Calcitonin (from the Thyroid) work together to keep the blood calcium levels within normal range.
What does calcium do?
- Muscle contraction
- Transmission of nerve impulses
- Blood clotting
- Normal action of many enzymes
The Pancreas
The pancreas is both an exocrine and an endocrine gland.
Exocrine - Acinar glands
Endocrine - Pancreatic islets
The islets have no ducts, therefore hormones diffuse directly into bloodstream.
What are the two types of islets? how do they secrete hormones differently? What do they both do?
Alpha cells secrete Glucagon
Beta cells secrete Insulin
Both control blood glucose levels.
What does insulin do?
Insulin: (reduces blood glucose levels)
Increases conversion of glucose to glycogen in the liver and skeletal muscle (Glycogenesis)
What does Glucagon do?
Glucagon: (increases blood glucose levels)
Increases conversion of glycogen to glucose in the liver and skeletal muscle (Glycogenolysis)
In severe circumstances encourages the breakdown of fats and proteins to form new sugar (Gluconeogenesis)
