Lesson 8: Skeletal Muscle Part II

*CRB* Which of the following structures enables the Syncytium between cardiac muscle cells? (A) NMJ expansions (B) MEPPs (C) Intercalated Discs (D) Increased I bands

(C) Intercalated Discs Intercalated Discs make the Synycium possible between cardiac muscle cells.

State whether each of the brain parts is responsible for the voluntary control of skeletal muscle OR the involuntary control of smooth/cardiac muscle? (1) Cortex (2) Spinal Cord (3) Brain Stem (4) Sympathetic Ganglia

(1) Cortex - responsible for the voluntary control of skeletal muscle (2) Spinal Cord - responsible for the voluntary control of skeletal muscle (3) Brain Stem - responsible for the involuntary control of smooth or cardiac muscle (4) Sympathetic Ganglia - responsible for the involuntary control of smooth or cardiac muscle

Compare the location for each of the following muscle types: (1) Skeletal Muscle (2) Cardiac Muscle (3) Smooth Muscle

(1) Skeletal Muscle - located just under your skin, attached to your bones via tendons (2) Cardiac Muscle - this is the muscle that makes up your heart (3) Smooth Muscle - this muscle is wrapped around blood vessels and hollow organs

State whether each of the following muscle types are under autonomic or voluntary control: (1) Smooth Muscle (2) Cardiac Muscle (3) Skeletal Muscle

(1) Smooth Muscle - autonomic (2) Cardiac Muscle - autonomic (3) Skeletal Muscle - voluntary

Compare the speed of contraction for each of the following muscle types: (1) Smooth Muscle (2) Cardiac Muscle (3) Skeletal Muscle

(1) Smooth Muscle - slow (2) Cardiac Muscle - medium (3) Skeletal Muscle - fast

*CRB* Which of the following are ways that the force of contraction could be increased physiologically? I. Recruiting larger motor units to contract. II. Increasing the frequency of stimulation. III. Increasing the activation of the Antagonistic muscles. (A) I only (B) I and II only (C) II and III only (D) I, II and III

(B) I and II only Recruiting larger motor units to contract and increasing the frequency of stimulation can increase the force of contraction.

*CRB* Which of the following types of muscle are Myogenic, meaning that although they can respond to nervous input, nervous input is not required for these cells to contract? I. Smooth Muscle II. Cardiac Muscle III. Skeletal Muscle (A) I only (B) I and II only (C) II and III only (D) I, II and III

(B) I and II only Smooth and Cardiac Muscles are Myogenic, meaning that although they can respond to nervous input, nervous input is not required for these cells to contract.

Which of the following are characteristics of smooth muscles? I. Spindle shaped II. Only 1 nuclei III. Nuclei located in the periphery of the cell (A) I only (B) I and II only (C) II and III only (D) I, II and III

(B) I and II only Smooth muscles are spindle shaped with only one nuclei in the center.

Which of the following are characteristics of skeletal muscles? I. Short Fibers II. Only 1 nuclei III. Nuclei located in the periphery of the cell (A) I only (B) III only (C) II and III only (D) I, II and III

(B) III only Skeletal muscles have long fibers. They have many nuclei that are located in the periphery of the cell.

*CRB* Fill in the blanks: Type I muscle fibers are often called _____________-twitch muscle fibers, whereas Type II Muscle Fibers are called ________________-twitch muscle fibers. (A) Slow, Slow (B) Slow, Fast (C) Fast, Slow (D) Fast, Fast

(B) Slow, Fast Type I muscle fibers are often called Slow-twitch muscle fibers, whereas Type II Muscle Fibers are called Fast-twitch muscle fibers.

Which of the following are characteristics of cardiac muscles? I. Branched II. Can be Uninucleate or Multinucleate III. Nuclei located in the periphery of the cell (A) I only (B) III only (C) I and II only (D) I, II and III

(C) I and II only Cardiac muscles are branched. They typically have 1-3 nuclei that are located in the center of the cell.

*CRB* Fill in the blanks: In the pectoral muscles, you would expect to see more _________________ muscle fibers; in the hamstrings, you would expect to see more _____________ muscle fibers. (A) Type I, Type I (B) Type I, Type II (C) Type II, Type I (D) Type II, Type II

(C) Type II, Type I In the pectoral muscles, you would expect to see more Type II muscle fibers; in the hamstrings, you would expect to see more Type I muscle fibers.

*CRB* Fill in the blanks: There are also skeletal muscles that will work together to move a body part in the __________ direction, and this relationship is called _____________. (A) Same, Synergistic (B) Opposite, Agonistic (C) Opposite, Antagonistic (D) Both A and C

(D) Both A and C There are also skeletal muscles that will work together to move a body part in the Same direction, and this relationship is called Synergistic. There are also skeletal muscles that will work together to move a body part in the Opposite direction, and this relationship is called Antagonistic.

*CRB* Which of the following statements about increasing the frequency of stimulation of muscles are true? I. This increase in stimulation leading to an increase in contractile force is called "Summation". II. If the muscle is stimulated to the point it does not relax at all between stimulation, this would be called "Fused Tetanus". III. Muscles in Fused Tetanus will eventually tire, and will need to have a relaxation period. (A) I only (B) I and II only (C) I and III only (D) I, II and III

(D) I, II and III Each of the following statements are true: I. This increase in stimulation leading to an increase in contractile force is called "Summation". II. If the muscle is stimulated to the point it does not relax at all between stimulation, this would be called "Fused Tetanus". III. Muscles in Fused Tetanus will eventually tire, and will need to have a relaxation period.

Which of the following muscle types are striated? What does that mean? What is responsible for giving the muscle a striated appearance? I. Smooth Muscle II. Cardiac Muscle III. Skeletal Muscle (A) I Only (B) III Only (C) I and III Only (D) II and III Only

(D) II and III Only Cardiac and skeletal muscle are striated. They are striped due to the presence of sarcomeres arranged end-after-end, and the z-lines linking these sarcomeres gives that dark band appearance.

*CRB* The MCAT will not test you on where certain muscles begin and end, but knowing those terms may be useful. Fill in the blanks: A muscle has 2 attachment points, and will contract so that its ________________ moves closer to its _______________. (A) Origin, Termination (B) Origin, Insertion (C) Insertion, Termination (D) None of the above

(D) None of the above A muscle has 2 attachment points, and will contract so that its Insertion moves closer to its Origin.

What is the role of creatine phosphate?

Creatine phosphate can donate its phosphate group to ADP, quickly forming ATP in order provide energy to fast-constracting type 2 muscle fibers.

True or False? Calcium can pass through cardiac muscle cells' tight junctions to cause neighboring cells to contract.

False. Calcium can pass through muscle cells' GAP junctions to cause adjacent muscle cells to contract.

True or False? All skeletal muscles are attached to tendons.

False. Not every skeletal muscle is attached to a tendon/bone. For instance, the external oblique muscle is attached to a different fibrous tissue known as an aponeurosis.

*CRB* Compare where the calcium for contractions can come from between Skeletal and Cardiac Muscle.

In Skeletal Muscle, the Calcium all comes from intracellular stores and the Sarcoplasmic Reticulum. In Cardiac muscle, there are the Sarcoplasmic Reticulum with calcium, and there are also voltage-gated calcium channels and these gap junctions between cells for calcium to travel through.

Mitochondria are more prevalent in type 1 or type 2 skeletal muscle fibers?

Mitochondria are more prevalent in type 1 muscle fibers (hint: m1tochond1a).

*CRB* What is the role of Myoglobin in the muscles? Does it exhibit cooperativity?

Myoglobin is the oxygen storage molecule for the muscle. It is not cooperative, because it is made of only one subunit and can only bind one oxygen molecule.

Where are the sympathetic ganglia located in relation to the spinal cord?

The sympathetic ganglia are fused together and run parrallel to the spinal cord.

What does it mean to say that cardiac muscle cells are in a syncytium with one another?

This means that when one cardiac muscle cell contracts, it will cause the neighboring cardiac muscle cells to contract.

*CRB* True or false? Aponeuroses are where multiple muscle fibers can connect, and will often thin at one end to form a tendon to attach to bones.

True. Aponeuroses are where multiple muscle fibers can connect, and will often thin at one end to form a tendon to attach to bones.

*CRB* True or false? The difference in fatigability between the Type 1 and Type 2 fibers is based on their oxygen/blood supply.

True. The difference in fatigability between the Type 1 and Type 2 fibers is based on their oxygen/blood supply.

*CRB* There is also a difference between Type 2A and 2B muscle fibers. True or false? Type 2A muscle fibers are an intermediate, because they are fast twitch and have oxidative capabilities.

True. Type 2A muscle fibers are an intermediate, because they are fast twitch and have oxidative capabilities.

Compare the color of type 1 versus type 2 muscle fibers.

Type 1 muscle fibers are red in color while type 2 muscle fibers are white in color.

Compare the contraction speed of type 1 versus type 2 muscle fibers.

Type 1 muscle fibers contract slowly while Type 2 muscle fibers contract quickly.

Compare the contraction duration of type 1 versus type 2 muscle fibers.

Type 1 muscle fibers have long-lasting muscle contractions. Type 2 muscle fibers have short-lasting muscle contractions.

Do type 1 or type 2 muscle fibers primarily utilize aerobic respiration? Do type 1 or type 2 muscle fibers primarily utilize anaerobic respiration?

Type 1 muscle fibers primarily utilize aerobic respiration. Type 2 muscle fibers primarily utilize anaerobic respiration.

Do type 1 or type 2 muscle fibers fatigue easily? Do type 1 or type 2 muscle fibers resist fatigue?

Type 2 muscle fibers fatigue easily. Type 1 muscle fibers are fatigue resistant.