Communication, hormones and homeostasis Flashcards
What are endocrine glands
Groups of cells that are specialised to secrete hormones
What are hormones
Chemical messengers often proteins or peptides and some are steroids
When are hormones secreted
When an endocrine gland is stimulated such as by a change in concentration of a specific substance. They can also be stimulated by electrical impulses
How do hormones travel around the body
They diffuse into the blood and take them around the circulatory system. They then diffuse out of the blood and around the body each hormone binding to specific receptors for that hormone found on membranes of cells called target cells.
What is tissue that contains target cells
Target tissue
What is the pathway of a response for chemical signals such as low blood glucose concentration
Stimulus - blood glucose concentration
Receptors on pancreas cells detect the low concentration
Hormone - The pancreas releases the hormone glucagon into the blood
Effectors - Target cells in the liver detect glucagon and convert glycogen into glucose
Response - Glucose is released into the blood, so glucose concentration increases
What is another word for a hormone and why
A first messenger because it carries the chemical message the first part of the way from the endocrine gland to the receptor on the target cells
What does a hormone binding to its receptor cause
Activates an enzyme in the cell membrane which catalyses the production of a molecule inside the cell called a signaling molecule which signals to other parts of the cell to change how the cell works
Why is a signaling molecule called a second messenger
It carries the chemical message the second part of the way from the receptor to other parts of the cell
What is the cascade that the hormone adrenaline results in
Adrenaline is the first messenger and it binds to specific receptors in the cell membranes activating an enzyme called adenylyl cyclase. This catalyses the production of a second messenger called cyclic AMP. Then a cascade of enzyme reactions occur making more glucose available to the cell by catalyzing glycogen breaking down to glucose
What are the adrenal glands
Endocrine glands that are found just above the kidneys containing the cortex and medulla
What is the function of the cortex of the adrenal glands
Secretes hormones such as cortisol and aldosterone when you are stressed which have a role in long and short term responses to stress.
How does the cortex section of the adrenal gland when responding to stress
- Stimulating the breakdown of proteins and fats into glucose, increasing the amount of energy avaliable so the brain and muscles can respond to the situation
- Increasing blood volume and pressure by increasing the uptake of sodium ions and water by the kidneys
- Suppressing the immune system
What is the function of the medulla of the adrenal gland
Secretes catecholamine hormones (adrenaline and noradrenaline) when stressed. These act to make more energy in the short term
How does the medulla section of the adrenal gland respond to stress
- Increasing heart and breathing rate
- Causing cells to break down glycogen to glucose
- Constricting some blood vessels so that blood is diverted to the brain and muscles
What are the islets of Langerhans
Areas of the pancreas containing endocrine tissue found in clusters around blood capillaries. They secret hormones directly into the blood
What are the islets of Langerhans made from
Alpha and beta cells
What do alpha cells secrete
Glucagon
What do beta cells secrete
Insulin
What are ectotherms
Animals that can’t control their body temperature internally and must control by changing their behavior.
What are ectotherms internal temperature, activity and metabolic rate controlled by
Their internal temperature and activity depends on the external temperature. They are more active in higher temperatures. Their metabolic rate is variable and generate very little heat themselves
What is an endotherm
An animal that controls their body temperature internally by homeostasis but can also do so by behaviour
What are endotherms internal temperature, activity and metabolic rate controlled by
Their internal temperature is less affected by external temperature and their activity is largely independent of temperature. They constantly have a high metabolic rate and generate a lot of heat from metabolic reactions.
What are mammals mechanisms to reduce body temperature
Sweating - secreted from sweat glands, taking heat from the body and evaporating it
Hairs lie flat - less air is trapped so the skin is less insulated and heat can be lost more easily
Vasodilation - arterioles dilate near the skin surface so more blood flows through the capillaries in the surface levels of the dermis. This means that more heat is lost from the skin by radiation and temperature is lowered.
What are the mechanisms to increase body temperature
Shivering - muscles contract in spasms so more heat is produced from increased respiration
Much less sweat - reduces heat loss
Hairs stand up - erector pili muscles contract trapping more air preventing heat loss
Vasoconstriction - arterioles near the surface of the skin constrict so less blood goes to the capillaries in surface of the dermis.
Hormones - release of adrenaline and thyroxine increasing metabolism and therefore heat
What are the different types of thermoreceptors and what do they do
Thermoreceptors in the hypothalamus detect internal temperature
Thermoreceptors in the skin (peripheral temperature receptors) detect external temperature
What controls mammals body temperature
The hypothalamus
What occurs when there is a rise in body temperature
- Thermoreceptors detect temp is too high
- Hypothalamus sends signals to effectors
- Vasodilation, sweating, hairs lie flat, no shivering, no adrenaline or thyroxine
- More heat’s lost and less heat is produced by the body
What occurs when there is fall in body temperature
- Thermoreceptors detect temp is too low
- Hypothalamus sends signals to effectors
- Vasoconstriction, much less sweating, hairs stand upright, shivering, adrenaline and thyroxine release
- More heat is produced and conserved by the body
What can change your blood glucose concentration
Eating carbs will rise and exercise will make it fall due to respiration
What is the normal concentration of glucose in the blood
90mg per 100cm^3
What is blood glucose monitored by
Cells in the pancreas called islets of Langerhans
What are insulin and glucagon
Peptide hormones which respond to restore the blood glucose concentration to the normal level
How does insulin lower blood glucose
1) Binds to specific receptors on the cell membranes of liver cells and muscle cells
2) Increases the permeability of cell membranes to glucose so cells take up more glucose
3) Insulin also activates enzymes that convert glucose into glycogen
4) Cells are able to store glycogen in their cytoplasm as an energy source
5) The process of forming glycogen from glucose is glycogenesis
6) This increases the rate of respiration of glucose in muscle cells
How does glucagon raise blood glucose concentration when too low
1) It binds to specific receptors on cell membranes of liver cells
2) Activates enzymes that break down glycogen into glucose called glycogenolysis
3) Glucagon promotes the formation of glucose from glycerol and amino acids
5) The process of forming glucose from non carbs is gluconeogenesis
What occurs in the negative feedback mechanism if a rise in blood glucose is detected
- Pancreas detects blood glucose concentration is too high
- Beta cells secrete insulin and alpha cells stop secreting glucagon
- Insulin binds to receptors on liver and muscle cells
- Cells take up more glucose, glycogenesis is activated, cells respire more glucose
- Less glucose in blood
What occurs in the negative feedback mechanism if a fall in blood glucose is detected
- Pancreas detects blood glucose concentration is too low
- Alpha cells secrete glucagon and beta cells stop secreting insulin
- Glucagon binds to receptors on liver cells
- Glycogenolysis is activated, gluconeogenesis is activated, cells respire less glucose
- Cells release glucose into the blood
How do beta cells secrete insulin
1) When blood glucose conc is high, more glucose enters the beta cells by facilitated diffusion
2) More glucose in a beta cell causes the rate of respiration to increase making more ATP
3) The rise in ATP triggers the potassium ion channels in the beta cell plasma membrane to close
4) This means potassium ions can’t get through the membrane so build up inside the cell
5) This makes the inside of the beta cell less negative as there are more positively charged potassium ions inside the cell so the plasma membrane of the beta cell is depolarized
6) Depolarisation triggers calcium ion channels in the membrane to open, so calcium ions diffuse into the beta cell
7) This causes the vesicles to fuse with the beta cell plasma membrane, releasing insulin by exocytosis
What is diabetes full name
Diabetes mellitus
What is diabetes mellitus
A condition where blood glucose concentration can’t be controlled properly. Either type 1 or 2
What is type 1diabetes
No insulin is produced.
Auto-immune disease where the body attacks and destroys the beta cells in the islets of Langerhans . After eating, blood glucose conc rises and stays high which can result in death if untreated. The kidneys are unable to reabsorb all the glucose so some is excreted in the urine`
How to treat type 1 diabetes
With insulin therapy:
- Regular insulin injections
- Insulin pump
Islet cell transplantation
What do people with type 1 diabetes need to do
Regularly monitor blood glucose conc and think about diet and activity
What is type 2 diabetes
Occurs when beta cells don’t produce enough insulin or the body does not respond properly to insulin. Linked to obesity. Glucose conc is higher than normal if insulin receptors do not work.
How to treat type 2 diabetes
Lifestyle changes: eating healthy, exercise and losing weight
Medication:
- Metformin, sulfonylureas, thiazolidinedione’s
Insulin therapy
How else can insulin be produced
By genetically modified bacteria. It can be extracted from animal pancreases but GM bacteria is more commonly used.
Stem cells could also be produced by growing them into beta cells to be implanted into the pancreas making insulin as normal for type 1 suffers
Why is GM bacteria used to produced insulin over from animal pancreas’s
- Cheaper
- Large quantities can be produced
- Less likely to trigger an allergic reaction or be rejected by immune system
- More ethical/religious
