Skeletal MicroAnatomy, Smooth & Cardiac Muscles

Question 1

T-tubules

Answer 1

-Are extensions of the cell membranes (sarcolemma) that associate with the ends (terminal cisternae) of the sarcoplasmic reticulum.

Question 2

Motor unit

Answer 2

-is single motor neuron and all the muscle fibers it controls

-Size varies with muscle control
-Ex:
•external eye (precise control) 4-6 muscle fibers
•leg muscle (gross control): 1000-2000 muscle fibers
-Muscle fibers of different motor units are intermingled within a radicle to distribute force better.

Question 3

3 major types of skeletal muscle fibers

Answer 3

• Fast Fibers
• Slow Fibers
• Intermediate Fibers

Question 4

Fast fibers

Answer 4

• Large in diameter
• Anaerobic
• Very Pale (few blood vessels, less myoglobin)
• have densely packed myofibrils, few mitochondria
• Produce powerful contractions

Question 5

Slow Fibers

Answer 5

• Half the diameter of fast fibers
• Highly aerobic (lots of mitochondria)
• Appear dark red (more blood vessels, myoglobin)
• Take 3x as long to contract compared to fast fibers
• Can maintain longer sustained contractions

Question 6

Intermediate fibers

Answer 6

• more closely resemble fast fibers
• Contain little myoglobin
• Relatively Pale
• More capillaries and more fatigue resistant than fast fibers

Question 7

3 types of muscle tissue

Answer 7

• Skeletal Muscle
• Smooth Muscle
• Cardiac Muscle

Question 8

Skeletal Muscle

Answer 8

• Found in Bones
• Voluntary contraction
• Striations
• Pulls on Bones

Question 9

Cardiac Muscle

Answer 9

• Found in heart
• Rhythmic contractions (involuntary)
• striations
• Pushes blood through arteries and veins

Question 10

Smooth muscle

Answer 10

• Pushes fluids and solids along the digestive tract
• Involuntary contractions
• no striations
• Found in GI & blood vessels

Question 11

Smooth muscle features

Answer 11

• Slow, sustained contractions
• under autonomous control
• Contain actin and myosin filaments but lack sarcomeres

Question 12

What 3 major differences between cardiac and skeletal muscles?

Answer 12

• Size: cardiac muscles are smaller
• Organization: Cardiac Muscle cells branch
• Number of nuclei: Cardiac Muscle Cells has 1 centrally places nucleus

Question 13

Similarities of cardiac and skeletal muscles?

Answer 13

-Both Contain actin and myosin filaments in an organized array that produces striations.

Question 14

Cardiomyocytes

Answer 14

-Found only in the heart
-Smaller than Skeletal muscles
-Single, centrally-located nucleus
-Highly branched
-cells contain organized myofibrils, striated appearance
-Cells connected by intercalated discs
•Gap junctions
•Desmosomes/Anchoring junctions
-Almost totally dependent on aerobic (need oxygen) metabolism for energy