Term
| What are the components of ryanodine receptors? |
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Definition
A & L subunits - open RyR
I1 - calcium can bind to create a long-term block
I2 - calcium can bind to create short-term block |
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Term
| How do ryannodine receptors work? |
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Definition
1. Ca2+ from inside the SR bind to L, creating calcium 'sparks'
2. Ca2+ in the cytosol bind to A, opening RyR & allowing efflux of calcium
3. Increase in cytosolic Ca closes RyR (I1 long-term, I2 short-term) |
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Term
| Which has a low affinity inhibition, L1 or L2 of RyR? |
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Definition
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Term
| Which has a high affinity inhibition, L1 or L2 of RyR? |
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Definition
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Term
| What is malignant hyperthermia, and what causes it? |
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Definition
uncontrolled release of Ca2+ by ryanodine receptors in the SR, leading to excessive muscle contraction
Mutation in ryanodine receptors (can be in L-type Ca2+ & Na as well but this is more rare) |
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Term
| What triggers malignant hyperthermia? |
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Definition
Gene-environement interactions
e.g. exposure to volatile anesthetics, exercise, succinylcholine |
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Term
| Symptoms of malignant hyperthermia |
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Definition
-respiratory or metabolic acidosis
-hypertension
-hyperthermia
-elevated CK
-tachycardia
-muscle spasms
-elevated resp rate |
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Term
| How is malignant hyperthermia diagnosed & treated? |
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Definition
Diagnose w/ contracture test
Treat: dantrolene, hyperventilate w/ 100% O2, cool body |
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Term
True or False
Individuals with malignant hyperthermia are sensitive to caffeine |
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Definition
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Term
| How does calcium return from the cytoplasm to the sarcoplasmic reticulum? |
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Definition
SERCA on mmb of SR pumps Ca2+ back inside using ATP (90% of it)
Na/Ca exchangers & pumps on cell mmb can pump Ca2+ out of cell as well |
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Term
| What happens with Ca2+ in regards to heart failure? |
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Definition
-cardiac cells will start moving Ca2+ out of the cell via Ca/N exchangers, instead of returning it to SR using SERCA
-less Ca2+ in SR for next use, excess Na+ in cell due to exchanger activity
-abnormal depolarizations result in arrhythmia |
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Term
| What are the steps of calcium activation & cross bridge formation? |
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Definition
1. Ca binds to TropC
2. Block on Trop I is released
3. Myosin can binds to actin weakly
4. Small contraction generated, causes conformational change in actin
5. Stronger bind between myosin & actin
6. Stronger contraction results from ATP being released
8. Ca+ either releases troponin & myosin is blocked again, or the cycle repeats. |
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Term
| What is Canine Dilated Cardiomyopathy? What causes it? |
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Definition
-heart cannot pump blood well because the chamber is enlarged and weak
-chamber can't relax and fill, or contract properly
-due to myofilaments being unable to generate enough force |
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Term
| What is used to treat DCM in doberman pinschers? How? |
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Definition
deoxygenated ATP
-increase expression of R1R2 (ribonucleotide reductase) which promotes dATP production
-can do this my introducing a virus with this enzyme into the cell |
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Term
| What pathway does blood follow through the heart? |
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Definition
Vena Cavas
Right Atrium
Tricuspid Valve
Right Ventricle
Pulmonary semilunar valve, pulmonary trunk
Pulmonary veins
Left atrium
Mitral valve
Left Ventricle
Aortic Semilunar Valve
Aorta |
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Term
| These valves control the flow of blood between ventricles & vascular system |
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Definition
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Term
| These valves control between atria and ventricles |
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Definition
| tricuspid & bicuspid/mitral |
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Term
| What is mitral valve regurgitation? |
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Definition
-valve failure due to excess connective tissue
-stiff valves can't seal
-ruptures chordae tendonae -> valves flutter
-valve prolapse = valve slips into previous chamber |
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Term
| What are the stage of MVR? How do you treat? |
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Definition
A: high risk, no signs (all KCS that don't have a heart murmur)
B: Structural disease visible with echocardiogram, but no clinical signs
Treatment - ACE inhibitors, pimobendan
C: clinical signs, heavy breathing
Treatment - ACE inhibitors, pimobendan, furosemide
D: clinical signs of heart failure, lack of response to treatment
Treatment - increase med doses |
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Term
True or False
MVR is a curable disease |
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Definition
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Term
| Do large animals or small animals get more calcium from the SR, to supply muscle contraction? |
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Definition
| small animals (e.g. rodents) |
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Term
| While not done in vet med yet, how can valves be repaired in human medicine? |
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Definition
Annuloplasty - sew a PTFA ring structure surrounding the valve to shrink the opening
Prolapse correction - replace chordae tendonae with ePTFE cords (artificial replacements) anchored in suture |
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Term
| How does dantrolene work? |
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Definition
| stabilizes RyR to prevent uncontrolled calcium release |
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