L-25 Flashcards
What is homeostasis?
The tendency towards a relatively stable equilibrium at the optimal living conditions
What is the set point for homeostasis?
The constant ideal condition
What is the normal range for homeostasis?
The amount of fluctuation from the set point that is normal and expected for the average person
Why may a person still exhibit symptoms of a hormone disorder if their levels are within the normal range?
the population normal range is wider than an individuals normal range so a level can fall outside of the individuals normal range but inside the population range
Is neural or hormonal control systems faster acting?
Neural
Does neural or hormonal control centres cause longer lasting action?
Hormonal
What are hormones?
Chemical messengers secreted from the endocrine glands cells that are carried in the bloodstream to the target cells upon which they act
What is a benefit of hormonal signalling occurring through the bloodstream?
One stimulus promoting hormone release can lead to changes in many different areas of the body including a variety of changes in different organs
Name the 5 major endocrine glands
- hypothalamus
- pituitary gland
- thyroid gland
- adrenal gland
- Pancreas
What is special about the hypothalamus?
Links the endocrine and nervous system
What are the 4 main physiological variables maintained homeostatically through hormones?
- blood sugar concentration
- growth and repair
- basal metabolic rate
- blood calcium concentration
What is meant by hormone action specificity?
A hormone can only affect cels with specified receptors for that hormone
What are the 2 main types of hormones?
Water soluble and fat soluble
What is the chemical classification of water soluble hormones
75% are peptides and others such as adrenaline of noradrenaline are catecholamines
Are water or lipid soluble hormones made and stored?
Water soluble hormones are made and stored until required when they are released via exocytosis, as well as thyroid hormones (lipid soluble)
How do water soluble hormones travel?
Dissolved in the blood
How are lipid soluble hormones chemically classified?
Generally steroids
When are lipid soluble hormones produced?
They are made from cholesterol as required
How do lipid soluble hormones travel?
In the blood bound to a carrier protein
Where are the receptors for water soluble hormones located?
In the plasma membrane
Where are the receptors for lipid soluble hormones located?
in the cytoplasm or nucleus
What is the cellular response to water soluble hormone activation (4)
- hormone binds to cell receptor
- this allows activation of G protein
- G protein activates/ inhibits second messenger production/reduction
- downstream proteins/pathways are activated or deactivated
What is the cellular response to lipid soluble hormone activation? (8)
- lipid soluble hormone dissociates from carrier protein
- hormone diffuses across cell membrane
- hormone binds to intracellular receptor
- hormone-receptor complex acts as a specific transcription factor
- target gene is activated
- new mRNA is generated
- new protein is generated by translation of mRNA
- new protein mediates cell specific response (slow process)
What is the difference between water and lipid soluble hormones in the mechanism of action?
Water soluble is through 2nd messengers and lipid soluble is by altering gene transcription
What is the difference between water and lipid soluble hormones in speed of response?
Water soluble is ms to minutes, fat soluble is hours to days
What two factors dies the amount of hormone in the blood depend on?
- rate of secretion
- rate of removal from blood
How is the rate of hormone secretion controlled?
Negative feedback loops
What is the pancreas
both and exocrine and endocrine organ
How much or the pancreas is made up of endocrine islet cells?
1% ish
What two major hormones does the pancreas secrete?
Glucagon and insulin
What 4 hormones can increase blood glucose levels?
glucagon, growth hormone, cortisol, adrenaline
Why is insulin so important?
the only hormone that can lower blood glucose concentration
What can prolonged high glucose levels lead to?
Diabetes Mellitus
What can low blood glucose lead to?
Hypoglycaemia
To maintain blood glucose within the normal range in the brain, what two metabolic states do we move between?
The fed state and the fasting state
What occurs in the fed state?
Cellular uptake of nutrients and anabolic metabolism (synthesis of glycogen, protein and fat)
What occurs during the fasting state?
Mobilisation of nutrients and catabolic metabolism ( breakdown of glycogen, protein, and fat)
Where is glucagon secretid from?
Pancreatic alpha islet cells
Where is insulin secreted from?
Pancreatic beta islet cells
What is glucagon released as a response to?
Low blood glucose conc.
What is insulin released in response to?
High blood glucose conc.
What does glucagon act on?
Liver cells
What does insulin act on?
Liver cells, muscle cells, adipose tissue
What does glucagon do?
Releases stored glucose
What does insulin do?
Stores glucose as glycogen
What is the normal range for blood glucose concentration
70-110mgdL^-1
