Lecture 14- Muscle Tissue: Function+ Dysfunction Flashcards
Similarities between cardiac and smooth muscle
- Nuclei are central
- Only one contractile cell type
- Mycotyes communicate through gap junctions
Differences between smooth + cardiac muscle
- Smooth muscle does not contain sarcomeres
- Electrical conduction in cardiac muscle
- No troponins in smooth muscle
How does cardiac innervation work?
Parasympathetic- Slows down heart rate. Goes down the vagus nerve all the way towards the atrium.
Sympathetic- Increases heart rate. Send it’s signal down to T1,T4 level in spinal chord then towards the ventricles of the heart.
How does cardiac contraction work?
1) electrical signals acts on membrane and passes down t-tubule in the sarcolemma
2) Activates the DHP receptor, which pumps Calcium into the sarcosplasmic reticulum
3) Activates RYR to pump Calcium out from the sarcoplasmic reticulum into muscle cells
4) Calcium interacts with contraction machinery
Smooth muscle innervation
1) Neurotransmitters come out of Variscosity
2) The signal gives change in intracellular secondary messengers/ change in the Gated Calcium gates3)
3) Depolarisation of membrane, causes influx of calcium into cell
4) Calcium binds to calmodulin to form a complex and active myosin light chain kinase (MLCK) creates an activated enzyme with the complex.
5) The enzyme complex phosphorylates inactive myosin II from releasing it from a ring to a straight line with the heads available for actin binding+ causing contraction
6) Contraction keeps going until Calcium is not enough. Dephosphorylates the activated myosin so no available head.
How does Smooth muscle contraction work?
The dense bodies shorten and shorten the actin and myosin with it, contracting the whole muscle as a unit
Innervation of skeletal muscle
1) Nerve impulses realeases ACH from vesicles
2) Binds to receptors on the sarcolemma
3) Causes local depolarisation
4) Voltage-gated Sodium channels open, general depolarisation
3) Initiates an action potential propagated along the muscle
5) DHC receptors on t-tubule membrane change their conformation+ release Calcium into sarcoplasm.
6) Calcium binds with contraction machinery
What is the sliding filament theory?
1) Ca2+ binds to TnC of troponin, conformational change moves tropomyosoin away from actin’s binding site.
2) Mysoin head binds to actin+ contraction begins when ATP is hydrolysed into ADP+ pi
3) The working stroke occurs, myosin head pivots and bends as it pulls on the actin filament, sliding towards the M line.
4) When new ATP attaches to myosin head, cross bridge detaches.
What is Compartment syndrome?
Trauma in one compartment cause internal bleeding,exerting pressure on blood vessels+ nerves
Symptoms: Localised pain, Swollen shiny skin, Paresthesia
Myasthenia gravis
An autoimmune disease where the Ach receptors are blocked by antibodies
Symptoms: Reduced synaptic transmission, muscle weakness
Muscle Hypertrophy
Replacement of muscle fibres> destruction
When it stretches too far the A band and I BAND can’t re-engage anymore so new fibrils have to be produced.
Muscle atrophy
Destruction of muscle fibres> replacement
Bed rest, comma
Muscle’s aren’t being used
What is Duchenne Muscular dystrophy
X-linked recessive disease
Mutation in the dystrophin gene
Absence of dystrophin, excess calcium, taken by mitochondira. Osmolyte. Causes mitochondria to burst, Muscle to burst. Causes Rhabdomylosis.
Creative kinase and Myogoblin released
Creative Kinase
Enzyme used for making phosphocreatine. Used to be an indication of Myocardinal infarction
What is used to indicate myocardinal infarction?
Troponin I and T assays. There’s a peak in the curve
