Chapter 15- Muscle structure and physiology (2) Flashcards
What are sarcomeres?
Groups of myosin, actin and elastic myofilaments within the myocyte arranged together.
What is found at the end of each sarcomere?
A connective tissue called a Z disc.
What is attached to the Z disc?
Thin actin filaments
What interlocks between the actin filaments?
Myosin filaments anchored to the z disc by titin.
What is the I band?
The region containing thin actin filaments.
It appears light
What is the A band?
The area of overlapping actin and thicker myosin.
It appears dark
What is the H zone?
The region of myosin only
Why does a myofibril appear striped?
Because it consists of a repeating series of sarcomeres, arranged end to end in a line.
What is found at the end of the sarcoplasmic reticulum?
A cisterna- a membranous sac filled with calcium.
What is the transverse tubular system?
This is a continuation of the sarcolemma.
This system is crucial for excitation contraction coupling.
FUNCTION OF SKELETAL MUSCLE IN DOC
FUNCTION OF SKELETAL MUSCLE IN DOC
Fast twitch muscles contract…
quickly for rapid/brief motion.
Slow twitch muscles contract…
slowly and are usually active for prolonged periods of time.
Why do slow twitch muscles have many mitochondria and myoglobin?
Because these muscles are active for prolonged periods of time so uses a lot of energy, thus, have many mitochondria and myoglobin which stores oxygen
Myoglobin gives muscle what colour?
A red colour
What muscles are involved in maintaining posture and what muscle fibres do they contain?
Your soleus muscle in your lower leg and muscles in your back
Why do fast twitch muscles have a large sarcoplasmic reticulum?
For rapid release and uptake of calcium.
Why are fast twitch muscles less vascularised?
Because they rely on anaerobic respiration.
Little myoglobin results in the fast twitch muscles being what colour?
White colour
The extraocular muscles that move your eyes are made up what?
Fast twitch muscle fibres.
The size of muscle contraction is controlled in two ways:
1- Spatial summation
2- Temporal summation
How many motor neurons does a single muscle have and what does it come along with?
Each muscle has at least one motor neuron with a variable number of axon terminals.
What does each axon terminal form?
Each axon terminal forms a neuromuscular junction with a single muscle fibre.
What does a motor unit consist of?
A motor unit consists of one motor neuron and all the muscle fibres it innervates- to supply with nerves
When a motor neuron transmits an action potential, what happens to the all the muscle fibres it innervates?
They contract
