L10 Muscle Comparative Physiology Flashcards
If a muscle shortens it does ‘work’
= force x distance
What is the rate of work called?
Power
What do I mean in the lecture by ‘the muscle problem’? How does a cockroach overcome this?
The muscle problem is that a muscle cannot contract with both high velocity and high force.
To overcome this the locust leg acts like a catapult. This is done by the locust leg flexing (as it crouches) and staying flexed in the crouch. In this time the extensor muscle builds and stores energy, so that when the flexor muscle relaxes, the energy stored in the extensor muscle is released very quickly and with high force.
Why do many muscles usually contract at just under the maximum speed of shortening?
c
Give the properties of fast twitch muscle fibres
Few mitochondria or blood vessels, little or no myoglobin (pale in appearance)
Develop greater tension faster, but fatigue quickly
Cannot replenish ATP for prolonged contraction
Good for power - speed or strength
Give the properties of slow twitch muscle fibres
Contains myoglobin (which is binds O2. Has many mitochondria and blood vessels (red in appearance)
Reserves of glycogen and fat therefore can produce ATP as long as O2 is available
High ATPase activity and can recycle cross-bridges rapidly
Maximum tension develops slowly but highly resistant to fatigue
What kind of muscle fibre is found in each and give some examples:
a) Postural muscle
b) large leg or arm muscles
a) slow twitch
e. g.: soleus muscle - continuously active for standing
b) fast twitch muscle
e. g.: rectus femoris - a pennate muscle`
Why is there a dark band of tissue in fish?
It is a slow contracting band of muscle, the muscle it uses most of the time for cruising
What is most of fish tissue pale?
Fast swim escaping muscle, few mitochondria and infrequently use
What are noisy fish?
Very fast contractions of muscles of the swim bladder
What is special about theses muscle fibres is that very fast Ca2+ rise and fall, there are a lot of Ca2+ pumps in the SER. CA2+ release from troponin is very fast and so is cross bridges attaching and detaching
In insects, what are the differences between synchronous and asynchronous muscles?
Synchronous: one spike per twitch.
e.g.: Dragonflies, locusts; moths
Asynchronous: low rate of motor neuron spikes. Generally, high wing beat frequency; (white fly, nearly 1,000 s-1)Stretch activated by antagonist muscle.
Main advantage:
No need for large sarcoplasmic reticulum; therefore more contractile protein.
e.g.: Flies; beetles, bees and others.
What is ‘catch’ in a bivalve’s muscles?
Long-lasting contractions:
Activated by Ach; unlocked by serotonin. Once catch is activated, muscle can remain contracted & stiff for long periods, for example between tides.Takes very little energy to remain locked
There needs to be a mechanism which allows the whole muscle fibre to contract at once. What mechanism is this?
1) Regulate the number of motor units (a single - a motor neuron connected to multiple muscle fibres, a muscle can have hundreds) that are active
Spatial summation and temporal summation.
