Muscle

Question 1

What are the 3 types of muscle?

Answer 1

skeletal, smooth and cardiac

Question 2

Where is cardiac muscle found?

Answer 2

Occurs in the heart

Question 3

Where is skeletal muscle found?

Answer 3

Usually attaches to bones via tendons, it is also known as striated or voluntary muscle and is involved in movement, posture, heating and breathing

Question 4

Where is smooth muscle found?

Answer 4

Mainly in the walls of hollow tubes and organs

Question 5

Why is skeletal muscle referred to as fibers?

Answer 5

As they are extremely long and have an elongated structure

Question 6

What is the role of the cytoskeleton in muscle?

Answer 6

Skeletal muscle cells contain a large proportion of cytoskeletal components such as actin/myofibril
These filaments are arranged into smaller units of contraction called sarcomeres in myofibril
There are two distinct sections in the skeletal muscle cell, A bands and I bands (which contain a Z strip)

Question 7

What are the histological features of skeletal muscle?

Answer 7

• they have multiple peripheral nuclei
• this is a product of multiple cell fusions, synctium and the ability to produce more proteins
• they are very large cells
• the cytoplasm shows dark/light longitudinal sections

Question 8

What connects skeletal muscle and connective tissue?

Answer 8

endomysium= surrounds individual muscle fibers
perimysium = surrounds bunches of muscle fibers
epimysium= surrounds the entire muscle

Question 9

What are striations and sarcomeres?

Answer 9

striations = a single myofibril
sarcomeres = a repeating unit between Z lines

Question 10

What are striations/sarcomeres composed of?

Answer 10

thick myosin filaments

thin actin filaments

Question 11

What are:

• Dark A bands
• Light I bands
• Z bands

Answer 11

A = myosin and overlapping actin
I = actin
Z = where actin inserts/overlaps the myosin

Question 12

What is the sarcoplasmic reticulum?

Answer 12

Where Ca+ ions enter the system and the muscle contracts

Question 13

What are the steps in Ca+ ions entering the muscular system and contraction?

Answer 13

1. Vesicles of the neurotransmitter acetylcholine are released from the motor neurons axon and bind to receptors in the sarcolemma
2. Action potentials spread into the transverse tubular system and reach most of the fibre within milliseconds
3. The sarcoplasmic reticulum membranes release Calcium ions in response to the electrical impulse from the action potentials
4. Calcium floods myofibrils and the sarcomeres causing contraction of the actin/myosin filaments

Question 14

What is the neuromuscular junction?

Answer 14

the junction between the motor neuron and the muscle fiber

Question 15

What is the sarcolemma?

Answer 15

Plasma membrane of muscle cells

Question 16

What is the Sarcoplasmic reticulum?

Answer 16

ER organelle of muscle cell

Question 17

What are transverse tubules?

Answer 17

Extensions of the plasma membrane which extend from the sarcolemma to the sarcoplasmic reticulum

Question 18

What is the Sarcoplasm?

Answer 18

Cytoplasm of muscle cells

Question 19

What are the histological features of cardiac muscle?

Answer 19

• striated and has some sarcomeres with A/I bands and Z lines
• branched cells with 1/2 centrally located nuclei
• abundant mitochondria (sign of high respiration)
• There are numerous capillaries coursing through the branched cardiac muscle

Question 20

How are cells joined in cardiac muscle?

Answer 20

By intercalated disks such as desmosone junctions, adherence type junctions and gap junctions

Question 21

Provide examples of where smooth muscle is found?

Answer 21

Walls of organs such as the uterus, large and small intestine and respiratory system

Question 22

What are histological features of smooth muscle?

Answer 22

• no striations are present in smooth muscles, but it still relies on actin/myosin interactions for contraction
• plaques in cytoplasm with contractile filaments attached
• under neural, humoral and mechanical control
• central nucleus

Question 23

How do smooth muscle cells adjust their contraction/relaxation status?

Answer 23

by reorganising the actin cytoskeleton and intermediate filament network