Lecture 12 Endocrine System Flashcards
What are the general functions of the Endocrine System?
- Regulating growth, development, metabolism
- Maintaining homeostasis of blood composition and volume
- Controlling digestive processes
- Controlling reproductive activities
What are endocrine glands? Explain them.
The Endocrine system is composed of endocrine glands that are spread throughout the body.
Endocrine glands produce and secrete hormones that communicate and control other body cells. They travel in the blood to reach target cells.
An endocrine gland (via hormones) can communicate with any body cell that has a receptor for that hormone so the functions can be quite diverse.
What are Target cells?
Body cells display receptors for specific types of hormones.
* Cells that have specific receptors for a hormone are called target cells
Briefly explain how the Endocrine system works.
Endocrine glands produce and secrete hormones that travel in the blood in order to reach target cells.
Endocrine glands lack ducts so hormone secretions from endocrine cells enter the interstitial fluid and then the blood.
Hormones are transported in the blood from the endocrine gland where they are produced to all body tissues.
Hormones then leave the blood and enter the interstitial fluid, which provides the hormone potential access to all body cells.
Hormones bind only to target cell receptors to initiate a particular response in the target cell
What’s the difference between the nervous and endocrine systems?
The endocrine system uses chemical signaling (hormones, produced by glands) while the nervous system uses electrical signaling.
The signal transmission of the nervous system is fast, while in the endocrine system, it is slow because they have to travel some distance through the bloodstream.
What is a reflex? Explain them.
A reflex is a pre-programmed involuntary response to a stimulus.
* Secretion of hormones from endocrine glands is controlled through a reflex.
Endocrine reflexes are stimulated by one of three types of stimulation.
* Hormonal, Humoral, Nervous
Explain Hormonal Stimulation.
The release of a hormone in response to another hormone binding.
Explain Humoral Stimulation.
The control of hormone release in response to changes in extracellular fluids such as blood or the ion concentration in the blood.
Explain Nervous Stimulation.
Direct stimulation from the nervous system.
What is the Infundibulum?
Thin/hollow stalk which connects the hypothalamus and pituitary gland.
Where is the Pituitary gland located? Explain the different parts of the pituitary gland.
The pituitary gland is housed in the sphenoid bone of the skull and is composed of two portions.
* The posterior pituitary
* The anterior pituitary
Explain the Posterior pituitary and the Anterior pituitary.
Posterior pituitary (neurohypophysis)
* Composed of neurons that extend from the hypothalamus to the posterior pituitary created the hypothalamo-hypophyseal tract.
(the posterior pituitary does not form any hormones, instead, it stores the hormones that were made in the hypothalamus.)
Anterior pituitary (adenohypophysis)
* Composed of hormone-producing cells
* Connections between the hypothalamus and the anterior pituitary gland involve 2 capillary plexuses that are interconnected. This is called the hypothalamo-hypophyseal portal system.
What are Antidiuretic Hormones (ADH)?
Produced in the hypothalamus and stored and released in the posterior pituitary
Targets:
- Kidneys: reduces water loss in the urine & promotes water reabsorption
- Thirst Center: relays nerve signals to tell the body to drink more water
(when you are dehydrated)
What are Oxytocin Hormones?
Produced in the hypothalamus and stored and released in the posterior pituitary
Targets:
- Smooth muscle of uterus: to help deliver a baby
- Smooth muscle of breasts in lactating females: help ejection of breast milk
What are Regulatory hormones?
They are produced in the hypothalamus and are transported through the hypothalamo-hypophyseal portal system to the anterior pituitary.
* The anterior pituitary then releases its hormones into general circulation so they can reach their target cells.
These regulatory hormones act as either:
* Releasing hormones: causing an increase in secretion in a specific A.P. hormone.
* Inhibiting hormones: causing a decrease in secretion in a specific A.P. hormone.
What are Thyroid stimulating hormones (TSH)?
Stimulates release of hormones from the thyroid gland
What are Prolactin hormones?
Regulates production of breast milk in lactating females.
What are Adrenocorticotropic hormones (ACTH)?
Stimulates the adrenal cortex to secrete glucocorticoids which increase blood levels of nutrients molecules.
What are Follicle-stimulating hormones (FSH) and Luteinizing hormones (LH)?
- Act on the gonads in both males and females
- Development of egg and sperm cells, release of reproductive hormones
What are Growth hormones?
Stimulates the liver to release insulin-like growth factors which stimulate cell growth and division
- When growth hormone is over produced it can cause Hypersecretion (pituitary giantism)
- When growth hormone is under produced it can cause Hyposecretion (pituitary dwarfism)
What are Calcitonin hormones?
Produced by parafollicular cells and ultimately lowers blood calcium levels.
Targets:
- Bone: inhibits bone breakdown by osteoclasts and lengthens lifespan
- Kidney: increases loss of calcium in the urine
(triggered by high Ca2+ concentration in the blood)
What are the two regions of adrenal glands?
Regions:
* Inner Adrenal Medulla
* Outer Adrenal Cortex
- Adrenal Cortex Zones:
* Zona glomerulosa
* Zona fasciculata
* Zona reticularis
What are the two hormones produced by the Adrenal Medulla? Explain them.
Epinephrine and Norepinephrine via stimulation from the sympathetic division of the autonomic nervous system.
Targets:
- Heart, blood vessels, liver, adipose cells
(prepares body for fight of flight)
What are Mineralocorticoids?
Hormones of the Adrenal Cortex- zona glomerulosa
- A group of hormones that help regulate the concentration of electrolytes in the body fluids
