NEURO PHYSIOLOGY Flashcards
what is the difference with paracrine and autocrine
paracrine is when the hormone affect local targets and autocrine is when they act on the producing cell itself
what are the three categories of hormones
peptides and proteins eg insulin
steroid hormones which are synthesised from cholesterol
amino acid derivatives eg adrenaline and thyroid hormones
which type of hormones need to be bound to carrier proteins and why
lipid soluble ones eg cortisol and T3,T4. the carrier proteins prevents it from degradation in the blood and it dissociates once at the receptor
how are peptide hormones produced
produced as prohormones which have reduced activity until they’re cleaved by endopeptidases.
where are hormones stored
in secretory granules that are released by exocytosis after the appropriate stimulus which is dependant on Ca 2+
how are steroid hormones produced
produced from cholesterol which is stored in lipid droplets within the cell until needed. hormone synthesis takes place in the mitochondria and SER. the hormone is made and released immediately upon stimulation
how are amino acid derivative hormones formed
the actecholines (adrenaline and noradrenaline) are synthesised from tyrosine residues and stored in secretory vesicles and rebased in response to an AP
T4 and T3 are formed by iodination of tyrosine resides and bind to intracellular receptor altering gene transcription. bind to thyroglobulin and slowly release hormones to target tissues
what is water soluble hormone signalling
hormone binds to the cell surface receptors to activate downstream signalling eg G proteins leading to camp as a second messenger. these pathways cause changes to specific cellular reaction resulting in the response hormone. causes an enzyme cascade which happens outside as it water soluble hormones can’t cross inside and so the cascade creates a final product which can cross and will create the effect the hormone needed to create
how does steroid hormone signalling work
the steroid hormone dissociates from carrier protein and can diffuse across the cell membrane to bind to an intracellular receptor. this complex acts as a factor which controls the expression of target genes. these pathways lead to changes in cellular reactions causing a response to the hormones
what is the target organ and the action of ACTH
adrenal cortex and its a stress response and sodium retention
what are the direct effects of GH
- increased fatty acid use
- decreased rate of glucose uptake and metabolism
- glycogen breakdown
what are the indirect effects of GH
increased formation of collagen and deposition of bone matrix
disorders of growth hormone
- hyper secretion in children results in gigantism and in adults acromegaly
- hyposecretion results in pituitary dwarfism
what hormone does the pineal gland secrete
melatonin which induces sleep and resets the pacemaker of the circadian rhythm
how does the thyroid gland work
the stimulus causes the hypothalamus to release TRH and this causes the anterior pituitary to release TSH which causes the thyroid gland to release T3 and T4
how does the thyroid gland release T3 and T4
- thyroglobulin molecules are packaged into vesicles and exocytosed into the lumen of the follicle.
- the iodide ion enters through a sodium/iodide cotransporter and exits into the lumen through a chlorine/iodide antiport
- iodide ions oxidized to iodine and added to the thyroglobulin
- MIT, DIT, T3 and T4 mixture is formed
- the mixture is endocytosed back into the follicle
- the mixture undergoes proteolysis and the T3 and T4 is released
what is the function of T3
- increases basal metabolic rate
- maintain body temp
- stimulate protein synthesis
it has a greater activity than T4
what is the function of the parathyroid hormone
involved in calcium homeostasis. Sustained levels of PTH acts to increase osteoclast activity and bone resorption, releasing calcium
what does PH do to kidney
- increase reabsorption of calcium from urine
- increases the expression of the enzyme which activates vitamin D
- increases the excretion of phosphate
what is the function of vitamin D metabolite
increases the absorption of calcium and phosphate in the GI tract
what hormone does the zona glomerulosa produce
mineralcotricoid
what hormone does the zona fasiculata produce
glucocorticoids
what hormone does zona reticularis produce
adrenogens
what hormone does the medulla produce
catecholamine, noradrenaline and ardrenaline
what is the function of aldosterone
increases sodium and water reabsorption in the kidney
what is the function of androgens
source of testosterone in women
what is the function of cortisol
exerts anti-inflammatory effects and decreases immune response
what are disorders of the adrenal gland
excessive cortisol leads to Cushing syndrome
what is up regulation and down regulation
upregulation is when there is an increase in the number of receptors on the membrane and downregualtion is when there is a decrease in the number of receptors on the membrane
what is hormone deficiency
often due to autoimmune destruction of the endocrine gland
what is hormone resistance
mutation in hormone receptors which leads to downstream effects
what is hormone excess
endocrine tumors antibody mediated trigger of hormone receptors
what is the function of insulin
increase glucose absorption from the blood and stimulates glycogen formation
what is the function of glucagon
stimulates glycogenolysis and inhibits insulin release
which cells in the islets of langerhan produce insulin and which ones produce glucagon
insulin- beta cells
glucagon beta cells
where are the alpha cells located compared to beta cells
alpha cells line the centre and beta cells surround it
what is the normal blood glucose level
4-6mmol/L
how does glucose enter the cell
needs a glucose transporter which is the GLUT-2 transporter in beta cells
how is insulin released
glucose enters beta cell and is metabolized. this leads to an increase in ATP. The potassium channel gets inhibited and this leads to depolarization and so Ca2+ enters and this leads to insulin secretion
what are incretins
peptide hormone released by the intestine that act on pancreatic cells to stimulate insulin release
what is the effect of insulin on target cells
insulin receptor is tyrosine-kinase linked and when insulin binds it leads to vesicles containing GLUT-4 to move to the membrane which increases transcription of glucose metabolism enzymes. this surpasses gluconeogenesis and increases potassium uptake
what is the HbA1c test
older Hb binds to glucose and becomes glycated. an increase in blood glucose means increase in HbA1c and is used to indicate levels over three months
what are the general effects of high blood glucose
increased thirst
increased appetite frequent urination
what are the acute complications of high blood glucose
diabetic ketoacidosis
blurred vision
low consciousness
coma/death
what are the long-term complications of high blood glucose
nerve damage
sigh loss
CV disease
what is type 1 diabetes
T1DM
autoimmune
pancreas doesn’t produce insulin
which group is most likely at risk of T1DM and what is the genetic susceptibility
north europeans
30% more likely if parents have it
what is type 2 diabetes T2DM
insulin resistance
which group is most likely at risk of T2DM and what is the genetic susceptibility
black African and carribean and south asians
75% more likely if relative has it
what factors cause T2DM
insulin resistance causes more glycogen to be broken down and increased blood glucose levels
insulin resistance also causes less glucose uptake from blood
what are the treatments for diabetes
T1DM-diet and exercise and insulin
T2DM-diet and exercise and drugs e.g. metformin
what is double diabetes and how is it caused
when someone has type 1 and they get onto insulin which causes weight gain this then can lead to insulin resistance which is type 2
what is gestational diabetes
high blood glucose without type 1 or type 2 but is cause by insulin resistance
3-9% of preganancies
what are the risks to a child when the mother has gestational diabetes
oversize newborn low on sugar jaundice higher risk of obesity x6 of getting T2DM
what is the link between Alzheimers and diabetes
an increased risk of AD with diabetes. insulin resistance lowers energy of metabolism and so increases stress on brain cells which can lead to AD
what are some complications of diabetes
frequent urination due to increased osmotic pressure in blood
increase in thirst (polydipsia)
what is diabetic neuropathy
-nerve damage due to damage to small blood vessels and toxins
what is diabetic ketoacidosis
cells are unable to transport glucose and so consume fats for energy
fats breakdown to produce acidic ketones which leads to low pH
what are symptoms of ketoacidosis
muscle pain heart palpitations nausea vomiting coma death
what is hypoglycaemia
low blood glucose which leads to inability to provide energy to neurons
what are symptoms of hypoglycemia
headache dizziness blurred vision hunger tachycarida shaking
