Diabetes Flashcards
What is homeostasis?
The relative constancy of the body’s internal environment
What is the central process for the NS?
Detect- Intergrate- Respond
What are the three categories of the Peripheral NS?
Sensory system
Autonomic system
Somatic system
What does the somatic NS innervate to?
Skeletal muscle (voluntary responses)
Alpha motor neurons
What does the autonomic NS innervate to?
Preganglionic fibre->ganglion->postganglioinc fibre-> smooth, cardiac muscles/ glands and neurones
What are oligodendrocytes and where are they found?
Forms myelin sheath around axon in CNS, insulates and increases speed of transmission
What are the three categories in the autonomic NS?
Sympathetic (fight/flight)
Parasympathetic (rest/digest)
Enteric (neural network surrounding the gut)
What are Schwaan cells and where are they found?
The same as the oligodendrocyte but found in the peripheral NS
What is an astrocyte?
Provides structural and metabolic support in neurones
Take up excess neurotransmitters
Have foot processes which sit at junction of epithelial cells and protect them (blood brain barrier)
What are microglia?
Immune cells of the NS
What does the cell body contain?
Nucleus, mitochondria, RER- to make membrane proteins
What does an axon do?
Nerve fibre extending from axon hillock
Carries the action potentials
1µm-1m
Contains microtubules-which move proteins through neuron body
What do dendrites do?
Receive input from other neurons
Outgrowths from cell body
1-500000 per cell
What does the axon terminal do?
Synapse, release of neurotransmitter
Name sensory neurons and what do they do?
Afferent, transmit info to CNS, have sensory receptors at peripheral end
Name motor neurons and what do they do?
Efferent, transmit info from CNS to effector to organs or to other neurons
Name relay neurons and what do they do?
Interneurons – only in CNS and transmits from neuron to neuron, 99% of all neurons
What is a ganglia?
Collection of cell bodies of neurons
What does the peripheral NS consist of?
43 pairs of nerves
12 cranial pairs (brain)
31 spinal pairs
Name an important cranial nerve and what does it do?
Cranial nerve 10, vagus nerve
Parasympathetic supply from CNS to the thoracic organs (heart, lungs etc)
What is a nerve fascicle?
Many axons bundled in connective tissue
Describe the neuroendocrine mechanism:
The endocrine system works in coordination with the nervous system to maintain homeostasis
What is a hormone?
A chemical substance used to carry info from one part of the body to another via the blood
How is hormone secretion controlled?
Negative feedback
How can an action of a hormone be controlled?
An antagonistic hormone
Give the antagonistic hormone for insulin:
Glucagon
Why is glucose very important for the body?
Its the source of energy for the brain, 120g per day
What is the normal BG levels?
3.5-5.8mmol/L
What can amino acids be made into and where does the excess go?
Made into proteins (structural/ secretory)
Excess:
-can be made into glucose/ fat
-excreted via urea (urine)
What can glucose be made into and where does the excess go?
Most glucose used in respiration and expired for ATP
Excess:
-made into glycogen storage in liver/muscles
-can be made into fatty acids
What can fatty acids be made into?
Made into triglycerides stores in adipose tissue
Most produce ATP
What is the synthesis and breakdown of glycogen called?
Synthesis= glycogenesis
Breakdown= glycogenolysis
How much glycogen can be stored?
A limited amount
What is the synthesis and breakdown of fat called?
Synthesis= lipogenesis
Breakdown= lipolysis
How much fat can be stored?
Store as much as need, major energy store
What is the name for glucose being made by a.a and what is the name for protein breakdown?
Glucose synthesis= gluconeogenesis
Protein breakdown= proteolysis
What is glucagon and where is it secreted from?
Antagonistic to insulin, secreted from alpha cells in the islets of Langerhans
What is cortisol and where is it secreted from?
Glucocoticoid from adrenal cortex
Increase energy sources as part of stress response
What is adrenaline and where is it secreted from?
Increase blood glucose and fatty acids
Secreted from adrenal medulla
What is growth hormone and where is it secreted from?
Major effect in protein synthesis in muscles
Secreted from anterior pituitary, can elevate BG
What is somatostatin and where is it secreted from?
Inhibits digestion and absorption
Secretion of pancreatic hormones
Secreted from delta cells of endocrine pancreas in response to raised glucose or a.a
What is pancreatic polypeptide and where is it secreted from?
Appetite reduction
Secreted form F cells (pp cells) in response to raised a.a
What is amylin and where is it secreted from?
Delays gastric emptying
Secreted from B cells
Describe insulin:
Two polypeptide chains joined by disulphide bridges
A peptide hormone consists of alpha and beta chains
Acts as a tyrosine kinase receptor
Where is insulin secreted from and where does it target?
It is secreted from the B cells in the islets of Langerhans in endocrine pancreas into hepatic portal vein (liver being target)
How is insulin synthesised?
Synthesised as a pro peptide by ribosomes on the RER
Processing in the Golgi involves:
-folding and formation of disulphide bonds
-removal of the C peptide (31aa) to give 2 chains, A-21aa and B30aa linked by disulphide bonds
C peptide aswell as insulin is secreted, insulin is stored until secretion is stimulated
How can you indirectly measure the level of insulin secretion?
Plasma C peptide level is a measure of insulin secretion as it isn’t cleared rapidly from the blood
Describe the basic negative feedback mechanism for blood glucose control:
After a meal, BG increases
Glucose diffuses into pancreatic B cell via GLUT2
Increase in glucose conc in the cell causes secretion of insulin
Insulin decreases BG
Decreased glucose in the B cell decreases insulin secretion
Describe 3 other factors which can influence insulin secretion:
Some a.as (leucine, arginine) increase a.a secretion
Autonomic NS (parasympathetic increases, sympathetic decreases)
Some gut hormones (incretins- GLP1) secreted in the GI tract in response to food
Describe the pharmacological mechanism of how insulin is secreted from glucose:
Glucose enters the cell by diffusion via GLUT2
Glycolysis and the Krebs cycle forms ATP
ATP can gate a K+ channel which closes the K+ channel (ATP gated K+ channel) and this causes depolarisation as less K+ moves out
Depolarisation causes activation of voltage gated Ca2+ channels to open and Ca2+ enters the cell
Causes Ca2+ induced calcium release from the ER, causes exocytosis of secretory granules (containing insulin) causes insulin release
In which way does a.a cause the release of insulin?
The same way as glucose
How does the parasympathetic NS cause an increase in insulin?
Ach acting at muscarinic receptors, increase Ca2+ via Gq-> PLC->IP3-> Ca2+