D5 Hormones and metabolism Flashcards
What are endocrine glands?
Structures that decrete chemical messengers (hormones) directly into the blood
Where are hormones secreted from endocrine glands transported to?
specific target cells (figure 1)
What 6 types of hormones can there be?
- steroids
- proteins
- glycoproteins
- polypeptides
- amines
- tyrosine dreivatives
What 6 types of hormones can there be?
- steroids
- proteins
- glycoproteins
- polypeptides
- amines
- tyrosine dreivatives
What does this show?
A cross section through a thyroid gland follicle
What do thyroid hromones regulate?
Body’s metabolism
What does the follicle consist of?
A layer of cells (pink) around a central storage chamber
How do the components of the thyroid gland follicle work together to end up with hormones transporting around the body?
- the layer of cells (pink) produce the thyroid hormones
- hormones are secreted into the central chamber where they are stored in a viscous fluid colloid (yellow)
- follicle is surrounded by blood vessels (red), which transport the hormones around the body
What do thyroid hormones refer to?
- two similar hormones derived from tyrosine
- Triiiodithyronine (T3) and tetraiodothyronine (T4)
What is the difference between triiiodithyronine (T3) and tetraiodothyronine (T4)?
triiiodithyronine (T3): contains 3 iodine atoms
and tetraiodothyronine (T4): contained 4 iodine atoms
What does correct functioning of the thyroid require?
iodine in diet
What is a consequence of dietary insufficiency of iodine in diet?
Goiter
What is a goiter?
A condition
* inability to produce the thyroid hrmones because of thr absence of iodine
* hypothalamus and the anterior pituitary continuously stimulate the thyroid and enlargement of the thyroid results
What can iodine deficiency during pregnancy lead to?
- Affect fetal nervous development
- mental retardation in children
What effort has been made to eliminate iodine deficiency?
The international council for thr control of iodine deficiency disorders (ICCIDD), a non government organization (NGO) is partnered with UNICEF and WHO to mainly push for universal iodization of salt
What effort has been made to eliminate iodine deficiency?
The international council for thr control of iodine deficiency disorders (ICCIDD), a non government organization (NGO) is partnered with UNICEF and WHO to mainly push for universal iodization of salt
What do peptide hormones and lipid hormones differ?
In solubility
What does the difference in solubility of peptide and liipid hormones lead to?
Different mechanisms of action
What do peptide and lipid hormones have in common?
They act by binding to a receptor
What is the mechanisms of action of steroid hormones?
- cross directly through the plasma membrane
- Bind to receptor protein in cytoplasm
- cross through the nuclear membrane
- the receptor-hormone complex then serves as a transcription factor, promoting or inhibiting the transcription of a certain gene
How are steroid hormones able to pass directly through the plasma membrane and nuclear membrane?
It is lipid-soluble
What are 2 example of steroid hormones?
Estrogen and progesterone
What are 4 example of steroid hormones?
Estrogen, progesterone, testosterone, calciferol
What do receptor-hormone complex promote?
the transcription of specific genes
What can calciferol hormone affect?
absorption of calcium from the intestine
What is the mechanisms of action of steroid hormone calciferol?
- crosses the intestinal cell membrane
- binds to a receptor within the nucleus of the cell
- the receptor-hormone complex effects expression of the calcium transport protein calbindin in the small intestine which allows for the absorption of calcium from the intestine
In which two organs does cortisol act on to increase blood glucose?
liver and pancreas
How does cortisol affect raise blood glucose?
In liver cells
1. enter the nucleus
2. activates many of the genes needed for gluconeogenesis (conversion of fat and protein into glucose, raising blood glucose
3. at the same time, it decreases the expression of the insulin receptor gene (prevent glucose from being stored in the cells and also raising blood glucose)
In pancreas
1. cortisol-receptor complex inhibits the transcription of insulin genes
Why cant protein/peptide hormones pass through the membrane directly?
They are hydrophilic
What do protein/peptide hormones do instead since they cant pass through the membrane directly?
- bind to surface receptors
- trigger a cascade reaction
- mediated by chemicals called second messengers
Where are the receptors that peptide hormones bind to?
in the plasma membrane of the target cell
What are second messengers and what do they do?
small water soluble molecules that can quickly spread throughout the cytoplasm and relay signals throughout the cells
What are the 2 most common second messengers?
Calcium ions and cyclic AMP (cAMP)
* a large number of proteins are sensitive to the concentration of these molecules
What is epinephrene?
A hormone that mediates the “fight or flight” response when released
What do an organims need when under threat?
a supply of blood glucose as an energy source
What does epinephrene do when it reaches the liver?
- it binds to G-protein couple receptor (a receptor)
- the binding activates the G-protein
- G-protein then uses guanosine triphosphate (GTP) as an energy source to activate the enzyme adenylyl cyclase
- This converts ATP to cAMP
- the cAMP then activates protein kinase enzymes
- which in turn activate the processes of glycogen breakdown and inhibit glycogen synthesis
Gives supply of energy when epinephrene is released during fight or flight
What do hormones secreted by the pituitary gland control?
- growth
- Developmental changes
- reproduction
- homeostasis
What hormones do the anterior pituitary gland synthesize and secrete?
FSH, LH, prolactin
What hormones is secreted by the posterior pituitary gland?
Oxytocin and ADH
Where are the hormones secreted by the posterior pituitary gland synthesised?
in unusual cells called neurosecretory cells found in the hypothalamus
Where can neurosecretory cells be found?
In the hypothalamus
How is a hormone synthesised in neurosecretory cells and secreted by the posterior pituitary gland?
- the hormones travel down the axons of the neurosecretory cells
- are stored at the axons
- until impulses pass down the axon from the hypothalamus
- stimulating secretion
How is a hormone synthesised in neurosecretory cells and secreted by the posterior pituitary gland?
- the hormones travel down the axons of the neurosecretory cells
- are stored at the axons
- until impulses pass down the axon from the hypothalamus
- stimulating secretion
What controls hormone secretion by the anterior and posterior lobes of the pituitary gland?
the hypothalamus
What 2 systems in the body plays a role in homeostasis and in the control of other processes including reproduction?
Nervous and endocrine system
What links the nervous system to the endocrine system?
The hypothalamus via the pituitary gland
How is the pituitary gland effectively different glands?
the pituitary gland is made up of two parts with different mode of operation
How is the pituitary gland effectively different glands?
the pituitary gland is made up of two parts with different mode of operation
What is the role of the hypothalamus in hormone secretion?
- it secrete releasing factors
- which stimulate the secretion of the anterior pituitary gland’s hormones
- the releasing factors are carried from the hypothalamus to the anterior pituitary gland by a portal vein
What are the releasing factors from the hypothalamus carried by to the anterior pituitary gland?
by a portal vein
Why is the portal vein an unusual type of blood vessel?
it links two capillary networks
* one in the hypothalamus which unites to form the portal vein and another in the anterior pituitary gland, from which blood flows on to the rest of the body
How is negative feedback involved in the control of secretion of pituitary hormones?
e.g. ADH
* when blood solute concentration is too high
* impulses are sent along the axons of neurosecretory cells
* cause ADH secretion to increase
* ADH acts on the kidney
* If the blood solute concentration decreases too much, it is detected by the osmoreceptors in the hypothalamus
* fewer or no impulses are sent via neurosecretory cells
* ADH secretion reduces or stops
* allows blood solute concentration to rise
How is the prodution and secretion of milk controlled?
By hormonal control
by oxytocin and prolactin
What is prolactin?
A hormone produced by the anterior pituitary.
* stimulates mammary glands to grow and it also stimulates the production of milk
How is the ejection of milk acheived after pregnancy?
during pregnancy
* high levels of estrogen increase prolactin production but inhibit the effects of prolactin on mammary glands
After delivery
* abrupt decline in estrogen and progesterone
* removed inhibition of prolactin on mammary glands
* production of milk begins
Release of milk
* dependent on hormone oxytocin
* nursing by an infant stimulates the continued creation of prolactin
* stimulates oxytocin release
* oxytocin stimulates the contraction of cells that surrounds the structures holding the milk leading to the ejection of milk
How is the ejection of milk acheived after pregnancy?
during pregnancy
* high levels of estrogen increase prolactin production but inhibit the effects of prolactin on mammary glands
After delivery
* abrupt decline in estrogen and progesterone
* removed inhibition of prolactin on mammary glands
* production of milk begins
Release of milk
* dependent on hormone oxytocin
* nursing by an infant stimulates the continued creation of prolactin
* stimulates oxytocin release
* oxytocin stimulates the contraction of cells that surrounds the structures holding the milk leading to the ejection of milk
Where is oxytocin produced and stored?
By the neurosecretory cells of the hypothalamus and is stored in the posterior pituitary gland
What type of hormone are growth hormones? where are they produced?
polypeptide hormone
produced in the anterior pituitary
What is the main target of growth hormones?
receptors in liver cells
What does the binding of growth hormone to liver cells do? Additional effect?
- stimulates the release of insulin-like growth factor which circulates in the blood
- stimulates bone and cartilage growth
Additional effects
* increase in muscle mass
Why is growth hormone used as a performance enhacing drug?
- increase muscle mass
- increased availability due to development of genetically modified organisms that can produce it in large quantities
Why is growth hormone used as a performance enhacing drug?
- increase muscle mass
- increased availability due to development of genetically modified organisms that can produce it in large quantities
How does growth hormone acting as performance enhacing drugs benefit athletes?
- there is a correlation between muscle size and strength = so competitors that require short bursts of expolisve strength would benefit
- allows tired muscles to recover more quickly = can train harder and more often
How does growth hormone acting as performance enhacing drugs benefit athletes?
- there is a correlation between muscle size and strength = so competitors that require short bursts of expolisve strength would benefit
- allows tired muscles to recover more quickly = can train harder and more often
Why are performance enhacing drugs banned?
The benefits provided in terms of enhanced performance are small or non-existent compared to the risks of injecting the hormone
