Lecture 38 Flashcards
What part of blood glucose maintenance can be considered a feed forward system?
The release of amino acids and gastrointestinal hormones upon food entering the body, this can lead to insulin secretion before the blood glucose level has increased and is hence a feed forward system.
Why can insulin be considered as a signal that the body had been fed? Why can the lack of it be considered as starvation?
Insulin triggers cells within the body to take up and utilise/store nutrients.
The lack of it means glucagon secretion which instead mobilises glycogen stores in the liver, breaks down proteins to be used for gluconeogenesis, mobilizes fat stores and increases ketone production. These can all be considered as processes which use up nutrient stores within the body, meaning a lack of nutrients and hence starvation.
What are the main factors of type 1 diabetes Mellitus?
Little or no insulin production, typically affects younger people. It may be associated with prior illness and the subsequent autoimmune response which destroys the beta cells in the pancreas. Can be caused by environmental factors and a genetic predisposition.
What are the three main signs of diabetes mellitus?
Polyuria (large volumes of urine), Polydipsia (excessive drinking/thirst), polyphagia (excessive hunger).
What are the main factors of type 2 diabetes mellitus?
Insulin resistance leading to overworking of the beta cells and eventual wearing out of those beta cells. At first insulin is still secreted but is not enough to keep the blood glucose level normal due to reduced cellular responses. Tends to be caused by aging, obesity (due to a reduced number or function of insulin receptors and altered intracellular signalling in the target cells), genetic predisposition and other medical conditions.
Do both types of diabetes mellitus lead to hyperglycemia or hypoglycemia? Which type is likely to be more fat?
Type 1 and type 2 diabetes mellitus lead to hyperglycemia. Type 2 is more likely to be fat as the insulin levels produced may still be enough to maintain lipid and ketone levels but not enough to maintain blood glucose levels.
What treatment options are there for diabetes mellitus?
Type 1 can only be treated with insulin injections, type 2 can be treated with exercise, weight loss, oral drugs and insulin if required.
What are the two other types of diabetes besides diabetes mellitus?
Diabetes insipidus: caused by altered anti diuretic hormone or decreased response to it leading to lots of dilute urine with no glucose, often associated with a brain injury or tumour in the region of the pituitary gland.
Gestational diabetes: May affect women during pregnancy and may be resolved afterwards (not always).
How does diabetes mellitus cause thirst? Why is the urine sweet?
The high levels of glucose in the blood causes the blood to have a higher osmolarity than normal, this causes the kidneys to cause more urination and hence thirst. The urine is sweet due to glucose in the urine (glycosuria) which couldn’t be absorbed by the renal tubules due to the high glucose levels.
What is diabetic ketoacidosis? What is hyperkalemia and how does this tie in with ketoacidosis? Why is giving insulin to patients with diabetic ketoacidosis dangerous?
The ketones produced due to lack of insulin are acidic, leading to acidosis in excess, this leads to hyperventilation and hyperkalemia in many diabetics as well as causing an acetone smell on the breath.
Hyperkalemia is the exchange of the H+ in the acidic blood for K+ from inside the cells, this causes the total K+ of the body to deplete in the urine and as such if insulin is given to patients with diabetic ketoacidosis it can lead to hypokalemia as the H+ levels in the blood lower.
What are the chronic (long term) complications for patients with diabetes mellitus?
Cardiovascular disease, renal failure, retinal damage, poor wound healing, peripheral nerve damage and susceptibility to infection. All of which are linked to the cells not getting enough nutrients (hyperglycemia).
how are insulin injections normally handled?
One injection prior to a meal which is long acting (the feed forward part) and then smaller injections based on blood glucose readings (the negative feed back part).
How is blood pressure returned to normal following blood loss? What step must occur before this can finish? Which nerves will slow the heart? which will speed it up?
The blood pressure drop is detected by sensors in the large arteries, this information is sent to the cardiovascular control centres in the brainstem by nerves. A nerve impulse is sent back from the brain to the heart to tell it to increase the heart rate and force of contraction, this increases the cardiac output and hence blood pressure. (Nerve impulses are also sent to blood vessels to cause constriction and cause blood to divert from non essential organs.)
Prior to this finishing though platelets and coagulation must seal the wound to prevent more blood loss.
The sympathetic nerves speed the heart while the parasympathetic slow it down.
What signs typically occur with shock? Why?
Pale due to vasoconstriction of skin blood vessels, sweating due to innervation of sweat glands by sympathetic nervous system and tachycardia (increases heart rate due to compensation for blood pressure).
How is blood volume returned to normal following loss?
Arterioles in the kidneys detect the reduced blood pressure and trigger events leading to secretion of hormones from various organs which act to restore blood volume (and pressure), this is done via Na+ reabsorption by kidneys, water reabsorption by kidneys and thirst stimulation.
