10 - Endocrine System Flashcards
The study of the endocrine system includes several (4) categories:
- Autocrine chemical messengers.
- Paracrine chemical messengers.
- Neurotransmitters
- Endocrine chemical messengers.
What are autocrine chemical messengers?
An autocrine chemical messenger stimulates the cell that originally secreted it.
Give an example of autocrine chemical messengers.
The chemical messengers secreted by white blood cells during an infection. They can stimulate their own replication rate.
What are paracrine chemical messengers?
Paracrine chemical messengers act locally on nearby cells. These chemical messengers are secreted by one cell type into the extracellular fluid and affect surrounding cells of a different type.
Give an example of a paracrine chemical messenger.
An example is histamine, which is released by certain white blood cells during allergic reactions. Histamine stimulates vasodilation in nearby blood vessels.
What are neurotransmitters?
Neurotransmitters are chemical messenger secreted by neurons that activate an adjacent cell, whether it is another neuron, a muscle cell, or a glandular cell.
What are endocrine chemical messengers?
Endocrine chemical messengers are secreted into the bloodstream by certain glands and cells, which together constitute the endocrine system. These chemical messengers affect cells that are distant from their source.
Give the 10 main regulatory functions of the endocrine system:
- metabolism
- control of food intake and digestion
- tissue development
- ion regulation
- water balance
- heart rate and blood pressure regulation
- control of blood glucose and other nutrients
- control of reproductive functions
- uterine contractions and milk release
- immune system regulation
(1-5: 1 / 6-9: 2)
Are sweat glands endocrine glands?
No, they are exocrine glands.
Hormones fit into one of two chemical categories. Which?
- Lipid-soluble hormones
2. Water-soluble hormones.
How are lipid-soluble hormones transported?
In the bloodstream, but because of their low solubility in the aqueous blood, they attach to binding proteins.
How are water-soluble hormones transported?
They can dissolve in blood, so most of them circulate the bloodstream freely.
How are lipid-soluble hormones delivered to tissue?
They need to detach from their binding proteins. Once detached they are small and hydrophobic, which enables them to diffuse across the cell membrane (for instance that of the capillaries).
How are water-soluble hormones delivered to tissue?
They are large and hydrophilic, so they do not diffuse across the cell membrane easily.
Why can some hormones be taken orally, like synthetic estrogen, but others have to be injected, like insulin?
Hormones that are soluble in lipids, such as estrogen, may be taken orally because they can diffuse across the wall of the stomach. Insulin however is a protein hormone and will not be able to diffuse across the wall of the stomach, and will therefore be metabolized and therefore lose its physiological function.
Three types of stimuli regulate hormone release. Which?
humoral, neural and hormonal.
What is meant by humoral stimuli of hormone release?
Blood-borne chemicals (that are not hormones) can directly stimulate the release of some hormones. These chemicals are referred to as humoral stimuli.
Give an example of a humoral stimuli and its hormone.
Glucose levels in the blood directly stimulate insulin secretion by the pancreas.
What is meant by neural stimuli of hormone release?
Some neurons signal hormonal glands directly.
Give an example of a neural stimuli and its hormone.
In response to stress or exercise, the sympathetic division of the autonomic nervous system stimulates the adrenal gland to secrete epinephirne and norepinephrine.
What is meant by hormonal stimuli of hormone release?
When a hormone stimulates the secretion of other hormones.
Give an example of hormonal stimuli of hormone release.
Hormones from the hypothalamus and anterior pituitary gland regulate the secretion of thyroid hormones from the thyroid gland.
Two major mechanisms maintain hormone levels n the blood within a homeostatic range. Which?
- Negative feedback
2. Positive feedback.
What is meant by hormone regulation by negative feedback?
Negative feedback is where the hormone’s secretion is inhibited by the hormone itself once blood levels have reached a certain point. The hormone may inhibit the action of other, stimulatory hormones to prevent the secretion of the hormone in question.
What is meant by hormone regulation by positive feedback?
Some hormones, when stimulated by a tropic hormone, promote the synthesis and secretion of the tropic hormone in addition to stimulating their cell. In turn, this stimulates further secretion of the original hormone.
Lipid-soluble hormones bind to which type of receptors?
Nuclear receptors.
Water-soluble hormones bind to which type of receptors?
Membrane-bound receptors.
What is a nuclear receptor?
A receptor type that most often is located in the target cell nucleus or cytoplasm. Often this leads to a change in the expression of DNA in that particular cell.
What is a membrane-bound receptor?
A receptor type that extend across the target cell membrane.
What is the hormone response element?
The sequence of DNA that is the target of the receptor’s actions.
What is the transcription factor?
The combination of the hormone and its receptor. They are named such because they, together, regulate the transcription of the hormone response element of the DNA.
What is the effect of the steroid hormone aldosterone on the kidneys?
Aldosterone affects its target cells in the kidneys by stimulating the synthesis of proteins that increase the rate of Na+ and K+ transport. The result is a reduction in the amount of Na+ and an increase in the amount of K+ lost in urine.
Membrane-bound receptors activate responses in two ways. Which?
- Some receptors alter the activity of G proteins at the inner surface of the plasma membrane.
- Other receptors directly alter the activity of intracellular enzymes.
G proteins consists of subunits. Which?
3 subunits. From largest to smallest, they are called: alpha, beta and gamma.
How would a G protein look during its inactive state?
In the inactive state, a guanine diphosphate (GDP) is bound to the alpha subunit of each G protein.
How would a G protein look during its active state?
In the active state, guanine triphosphate (GTP) is bound to the alpha subunit.
Before the hormone binds to its receptor, where is the G-protein?
Before the hormone binds to its receptor, the G protein consists of three subunits, with GDP attached to the alpha subunit, and freely floats in the plasma membrane.
What happens to the receptor just after the hormone has bound to it?
After the hormone binds to its membrane-bound receptor, the receptor changes shape, and the G protein binds to it. GTP replaces GDP on the alpha subunit of the G protein.
After the hormone binds to its membrane-bound receptor, the receptor changes shape, and the G protein binds to it. GTP replaces GDP on the alpha subunit of the G protein. What happens after, but still while the hormone is attached?
The G protein separates from the receptor. The GTP-linked alpha subunit activates cellular responses, which vary among target cells.
What happens to the receptor when the hormone is no longer attached?
When the hormone separates from the receptor, additional G proteins are no longer activated.
How does inactivation of the alpha subunit of a G protein occur?
Inactivation of the alpha subunit occurs when phosphate is removed from the GTP, leaving GDP bound to the subunit.
Why are hormones that target membrane-bound receptors a part of a fast response?
They typically produce an instantaneous response because the second messenger they activate influences already existing enzymes.
What is meant by signal amplification in regards to hormones?
Each receptor typically produce thousands of second messengers, which leads to a cascade effect and ultimately amplification of the hormonal signal.
Short: what is the pituitary gland?
The pituitary gland (hypophysis) is a small gland about the size of a pea. It rests in a depression of the sphenoid bone inferior to the hypothalamus of the brain.
Short: what is the hypothalamus?
The hypothalamus is an important autonomic nervous system and endocrine control center of the brain. It is located inferior to the thalamus.
The pituitary gland has two parts.
The anterior pituitary and posterior pituitary.
What is the tissue of the anterior pituitary gland, and what is its embryonic origin?
It is made up of epithelial cells derived from the embryonic oral cavity.
What is the tissue of the posterior pituitary gland?
It is an extension of the brain and is composed of nerve cells.
What is the hypothalamic-pituitary portal system?
The capillary beds and veins that transport the releasing and inhibiting hormones between the hypothalamus and the pituitary gland.
What is the infundibulum?
Infundibulum and infundibular stalk are alternative names for the pituitary stalk, the connection between the hypothalamus and the posterior pituitary. (Wikipedia)
