Week 4: Endocrine System Flashcards
What are the components of the endocrine system?
- Hypothalamus
- Pineal gland
- Pituitary gland
- Thyroid gland
- Parathyroid gland
- Adrenal glands
- Pancreas
- Testis/ovaries
Where do hormones act on the body?
Hormones influence the activity of cells that have receptors for that particular hormone.
What 3 things is the endocrine system important for?
- Reproduction
- Growth and development
- Metabolism, fluid and electrolyte balance
How do water soluble hormones move to their target cell and cause a pathological response?
- Water soluble hormones circulate freely in the blood plasma.
- Diffuses from blood to bind to its recepta on the plasma membrane of a target cell.
- The binding activates a second messenger system.
- The 2nd messenger system alters cell activity (the physiological response).
How do lipid-soluble hormones move to their target cell and cause a pathological response?
- Hormones binds to transport proteins for circulation in the blood.
- Diffuses through the lipid bilayer of cell membrane into target cell.
- Binds to and activates receptors in cytosol or nucleus.
- Gene expression is altered causing synthesis of a new protein.
- Cell activity is directly altered by the new protein (pathological response)
What are 3 types of signals for hormone secretion stimulation?
Endocrine gland secretion can be stimulated by:
* Action potentials (nervous): released in response to neurons innervating an endocrine gland.
* Changes to blood chemical composition (humoral): In response to changes in the blood concentration of a particular substance. e.g. increased BGL stimulates pancreatic insulin secretion.
* Action of other hormones (hormonal): one hormone in the blood stimulates the secretion of another.
What is the term for when 2 hormones act together for a greater effect than if each acted alone?
A synergistic effect.
What tissue is the posterior pituitary gland composed of, and how is it connected to the hypothalamus?
The posterior pituitary gland is composed of neural tissue, and it is connected to the hypothalamus via neural pathways - axons that extend to it from the hypothalamus through the hypophyseal tract.
What are the 2 hormones secreted by the posterior pituitary gland?
Posterior piuitary hormones are oxytocin and antidiuretic hormones.
What is synthesised and stored in the thyroid gland?
Thyroid hormone
What are the 3 steps in the production of hormones by the anterior pituitary gland?
- Hypothalamic hormones reach anterior pituitary gland via hypophyseal portal veins.
- Anterior pituitary hormone release is stimulated by releasing hormones and suppressed by inhibiting hormones from the hypothalamus.
- The anterior pituitary gland releases hormones that travel to target tissues in the body.
What is a hormone?
A mediator molecule, released by an endocrine gland, and regulates activities in cells in other parts of the body.
What controls the pituitary gland?
The hypothalamus
What gland maintains the basal metabolic rate of the body?
The thyroid gland.
how many parathyroid glands are there, and what is their function?
There are 4 parathyroid glands.
They control the levels of calcium in the extracellular fluid.
What is the main endocrine function of the pancreas?
To regulate blood glucose levels via secretion of insulin and glucagon.
Where are the adrenal glands located in the body, and what 3 hormones do they produce?
They are located on top of each kidney. They produce adrenaline, cortisol, and aldosterone.
What is the endocrine function of the testis or ovaries?
The function of the testis is to produce testosterone.
The function of the ovaries is to produce oestrogen and progesterone.
What are the 2 chemical classes of hormones?
- Water soluble
- lipid soluble
Where do hormones bind to in the body?
Target cells equipped with specific receptors for that hormone.
What is down-regulation?
Excess hormone concentration causes the body to decrease the number of receptors for a hormone. This makes the body less sensitive to that hormone.
What is up-regulation?
Low hormone concentration causes the body to make more receptors for a hormone. This makes the target cell more sensitive to that hormone.
What are the 2 categories of hormones?
- Circulating hormones: produced by endocrine cells and released into the bloodstream to circulate to the target cell.
- Local hormones: act within the immediate vicinity of their production site. Do not travel in the bloodstream.
What is the second messenger system?
The binding of a water-soluble hormone to a receptor on the cell membrane surface, causing the production of a second messenger inside the cell, which produces the hormone-stimulated response.
What is the difference between endocrine and exocrine glands?
- Exocrine glands: secrete products into ducts.
- Endocrine glands: secrete products into the interstital fluid.
What are the functions of hormones?
- Regulation of:
- chemical composition and volume of internal environment.
- Metabolism and energy balance.
- Contraction of smooth and cardiac muscle fibres.
- Glandular secretions.
- Some immune system activities.
- Control growth and development.
- Regulate operation of reproductive systems.
- Help establish circadian rhythms.
What is the term for when the actions of 2 hormones oppose each other?
Antagonistic effects
What is the term for when the action of a hormone requires a simultaneous or recent exposure to a second hormone?
A permissive effect.
which region of the brain controls the pituitary gland?
The hypothalamus.
What connects the hypothalamus and the pituitary gland, and what are the 2 portions of the pituitary gland?
A stalk called the infundibulum connects the two.
The pituitary gland is divided into 2 portions: the anterior and posterior pituitary.
What tissue is the anterior pituitary gland composed of and how is it linked to the hypothalamus?
It is composed of glandular tissue, and is linked to the hypothalamus via a vascular network called the hypophyseal portal.
What is the functional relationship between the hypothalamus and the anterior pituitary gland?
The hypothalamus controls the anterior pituitary gland by releasing hypothalamic hormones, which travel through the hypophyseal portal veins to influence the release or suppression of anterior pituitary hormones.
What is the functional relationship between the hypothalamus and the posterior pituitary gland?
The hypothalamus sends action potentials through the neural pathways that connect it to the posterior pituitary gland, that lead to the release of stored hormones directly into the bloodstream.
What are the hormones produced by the anterior pituitary gland?
- Growth hormone
- Thyroid stimulating hormone (TSH)
- Follicle-stimulating hormone
- Luteinising hormon
- Prolactin
What is required for thyroid hormone synthesis?
Iodide is required, which is only supplied through dietary intake.
What is the thyroid gland made up of ?
Thyroid follicles
What 2 hormones are released from thyroid hormone synthesis?
- T3: Triiodothyronine
- T4: Thyroxine
What are the 5 functions of thyroid hormones in the body?
- Basal metabolic rate: rate of energy expenditure/O2 consumption at rest.
- Metabolism: Synthesis of carbohydrate, fat, protein.
- Heat production: Increased metabolic activity causes increased heat production.
- Regulation of tissue growth and development: Essential for normal growth.
- Effects on cardiovascular system: HR, BP
What is the negative feedback loop for thyroid hormone release?
- Low T3 & T4 blood levels or low metabolic rate stimulates TRH (Thyrotropin-Releasing Hormone) release.
- TRH is carried by hypophyseal portal veins to anterior pituitary gland and stimulates release of TSH (Thyroid-Stimulating Hormone) by thyrotrophs.
- TSH released into the blood stimulates thyroid follicular cells.
- T3 & T4 are released into the blood by follicular cells.
- Elevated T3 inhibits the release of TRH and TSH.
