Lab 5: Muscle Anatomy and Physiology

Question 1

In the LT lab station, how did the EMG signal (trace) change when weight was added to the participants arm? Based on your data, when weight is added, what is occurring within the muscles to maintain joint position?

Answer 1

bigger graph spikes, tripes antagonises with bicep. Recruit more motor units to increase neural activity (as represented by graph). 1 textbook = small motor units, 3 textbooks = bigger motor units

Question 2

muscle antagonist coactivation is a phenomenon where opposing muscle groups, such as biceps and triceps, contract simultaneously to stabilize a joint. When the bicep was contracting, what did you observe in the triceps tracing? what role do you think the triceps would play during elbow flexion?

Answer 2

triceps tracing would also slightly increase, because biceps and triceps work together during coactivation

Question 3

pectoralis major

Answer 3

action: depress the scapula, or elevates the ribs, stabilizes by anteriorly tilting the scapula

origin: anterior surfaces of the 3rd to 5th ribs

insertion: coracoid process of scapula

Question 4

serratus anterior

Answer 4

action: protraction of scapula, boxers muscle (flex elbow)

origin: from 1st to 8th or 9th ribs

insertion: entire anterior length of medial border of the scapula

Question 5

levator scapula

Answer 5

action: elevates, retracts and rotates the scapula, as well as lateral flexion of the neck

origin: transverse processes of C1 to C4 vertebrae

insertion: superior angle of scapula

Question 6

trapezius

Answer 6

action: retraction, internal rotation, elevation, depression

origin: external occipital protuberance, the medial third of the superior nuchal line, the nuchal ligament, and the spinous process of C7-T12

insertion: clavicle, acromion process and scapular spine

Question 7

rhomboid major

Answer 7

action: scapular retraction, rotation

origin: spinous process of T1-T4 vertebrae

Insertion: medial border of scapula

Question 8

rhomboid minor

Answer 8

action: scapular retraction, rotation

origin: spinous process of C6 to C8

insertion: medial border of scapula

Question 9

shrug your shoulders. what muscles allow you to return to anatomical position?

Answer 9

trapezius muscles

Question 10

Locate the prominent spine of the scapula posteriorly and follow the spine to its lateral end. What is this structure? Locate the junction between the structure and the clavicle by thrusting your arm anteriorly repeatedly until you can palpate it. What is this joint called?

Answer 10

The prominent structure at the lateral end of the spine of the scapula is the acromion, and the joint between the acromion and the clavicle is the acromioclavicular joint

Enables small gliding movements that are critical for full shoulder motion, especially during overhead activities.
Contributes to scapular rotation and positioning during arm movements.

Question 11

deltoid

Answer 11

action: abduction (pull upwards), medial and lateral rotation, flexor and extensor of shoulder

origin: clavicle, acromion process and spine of scapula

insertion: deltoid tuberosity

Question 12

latissimus dorsi

Answer 12

action: extension (pull arm backwards) , adduction (down to body), medial rotation

origin:spinous processes of T7 to L5, sacrum and iliac crest

insertion: medial crest of the intertubercular (bicipital) groove

Question 13

pectoralis major

Answer 13

action: flexion (shoulder), extension (of arm when flexed), adduction, medial rotation (of arm)

origin: clavicle, sternum, superior six costal cartilages and abdominal aponeurosis

insertion: lateral crest of the intertubercular (bicipital) groove

Question 14

Teres Major

Answer 14

action: extension (shoulder), adduction, medial rotation of arm

origin: lateral border of scapula

insertion: medial crest of intertubercular (bicipital) groove

Question 15

Infraspinatus

Answer 15

action: lateral rotation (pull humorous towards back)

origin: infraspinous fossa of scapula

insertion: greater tubercle of humerus

Question 16

subscapularis

Answer 16

action: holds head of humerus in place and medially rotates the arm

origin: subscapular fossa

insertion: anterior side of humerus

Question 17

supraspinatus

Answer 17

action: abduction (pull up on humerus)

origin: supraspinous fossa

insertion: greater tubercle of humerus

Question 18

teres minor

Answer 18

action: holds head of humerus in place and laterally rotates, adducts the arm

origin: scapula’s posterior surface, near the upper part of its lateral border.

insertion: greater tubercle of humerus

Question 19

Locate the greater tubercle of the humerus on the superior surface of the shoulder. Place your hand on the superior and lateral portion of your shoulder, What muscle are you palpating? What is the origin and insertion of this muscle? What actions is it responsible for?

Answer 19

The supraspinatus is the most superior of the rotator cuff muscles

origin: supraspinous fossa

insertion: greater tubercle of humerus

action: abduction (pull up on humerus)

Question 20

Palpate your biceps brachii. In order to feel this muscle contract, what action can you perform?

Answer 20

flexion and supination

Question 21

Palpate your triceps brachii. In order to feel this muscle contract, what action can you perform?

Answer 21

extension (pull ulna into straightened position)

Question 22

Identify the muscles comprising the quadriceps femoris group. What is the primary movement of these muscles?

Answer 22

rectus femoris (originates at hip and crosses knee and hip joint), vastus intermedius (center), vastus medialis (medial) , vastus lateralis (lateral)

action: extension at knee, flexion of hip

Question 23

what is the longest muscle in the body? Generally where does the muscle originate and insert?

Answer 23

The sartorius muscle

origin: hip, crosses anterior surface of thigh

insertion: medial side of leg

Question 24

identify the muscles compromising the hamstring group. What is the primary movement of these muscles?

Answer 24

semitendinosus (medial), biceps femoris (lateral and superficial) + lateral rotation of leg) , semimembranosus (deep)

action: flexion at knee, extension at hip

Question 25

describe the IT band and its function

Answer 25

thick band of fascia, CT, that extends from the outside of the hip down to the knee. Plays crucial role in stabilizing the knee during activities like running and cycling. IT band tightness can lead to pain by causing friction against the lateral femoral epicondyle, particularly when the knee is repeatedly bent and straightened.

This condition known as IT band syndrome, can result in sharp or aching pain on the outside of the knee, and may cause referred hip pain. Common among athletes who engage in repetitive knee flexion and extension activities.

Question 26

Processes occurring at the Neuromuscular junction

Answer 26

1. first AP causes opening of Ca2+ voltage gated channels
2. exocytosis of synaptic vesicles (Ach is inside)
3. release of Ach
4. binding of Ach to ligand gated sodium channel
5. opening of ligand gated Na+ channels
6. closing of Na+ channels
7. breakdown of Ach into acetic acid and choline
8. reabsorption of choline
9. production of new Ach