Q: Which muscle is primarily responsible for flexing the forearm at the elbow, and what is the equation for torque ($$\tau) $$generated by this muscle if the force ($$F) $$applied is 50 N and the lever arm ($$r) is 0.03 m$$?

Biceps brachii; $$\tau = F \times r = 50 \times 0.03 = 1.5\ \text{Nm}$$

Q: Which muscle is responsible for the movement of the head from side to side, and what is the equation for angular velocity ($$\omega) if $$the head rotates $$\theta = 90^\circ in$$ $$t = 2$$ seconds?

Sternocleidomastoid; $$\omega = \frac{\theta}{t} = \frac{\pi/2}{2} = \frac{\pi}{4}\ \text{rad/s}$$

Q: Which muscle is primarily responsible for plantar flexion of the foot, and what is the equation for work ($$W) $$done if the force ($$F) is 200 N $$and the distance ($$d) $$moved is 0.05 m?

Gastrocnemius; $$W = F \times d = 200 \times 0.05 = 10\ \text{J}$$

Q: Which muscle is responsible for flexing the thigh at the hip joint, and what is the equation for power ($$P) if $$the force ($$F) is 150 N $$and the velocity ($$v) is 0.2 m/s$$?

Iliopsoas; $$P = F \times v = 150 \times 0.2 = 30\ \text{W}$$

Q: Which muscle is primarily responsible for adduction of the thigh, and what is the equation for calculating the resultant force ($$F_{res}) if $$Adductor longus and Adductor magnus each generate 80 N at an angle of $$30^\circ to $$each other?

Adductor longus; $$F_{res} = \sqrt{80^2$ + 80^2$ + 2 \times 80 \times 80 \times \cos(30^\circ)} \approx 151.6\ \text{N}$$

Question 1

A patient presents with difficulty chewing and weakness in jaw closure. Which muscle is most likely affected?

Accepted Answer

Masseter

Question 2

During a physical exam, a patient is asked to raise their eyebrows. Which muscle is primarily responsible for this action?

Accepted Answer

Epicranius

Question 3

A baseball pitcher suffers an injury that impairs his ability to rotate his forearm so his palm faces downward. Which muscle is most likely damaged?

Accepted Answer

Pronator teres

Question 4

Which muscle is primarily responsible for flexing the forearm at the elbow, and what is the equation for torque ($$	au) $$generated by this muscle if the force ($$F) $$applied is 50 N and the lever arm ($$r) is 0.03 m$$?

Accepted Answer

Biceps brachii; $$	au = F 	imes r = 50 	imes 0.03 = 1.5\ 	ext{Nm}$$

Question 5

A runner complains of pain in the lateral side of the lower leg after training. Which muscle is most likely involved?

Accepted Answer

Fibularis longus

Question 6

Which muscle is responsible for compressing the cheeks during blowing, and what is the physiological significance of this action?

Accepted Answer

Buccinator; It prevents food from accumulating between teeth and cheeks during chewing.

Question 7

A patient is unable to abduct their arm at the shoulder joint. Which muscle is most likely impaired?

Accepted Answer

Deltoid

Question 8

Which muscle group is primarily responsible for extension of the knee, and what is the formula for calculating the total force ($$F_{total}) if $$each of the four muscles generates 100 N?

Accepted Answer

Quadriceps femoris (Rectus femoris, Vastus medialis, Vastus intermedius, Vastus lateralis); $$F_{total} = 4 	imes 100 = 400\ 	ext{N}$$

Question 9

A patient presents with difficulty flexing their wrist. Which muscle is most likely compromised?

Accepted Answer

Flexor carpi radialis

Question 10

Which muscle is responsible for the movement of the head from side to side, and what is the equation for angular velocity ($$\omega) if $$the head rotates $$	heta = 90^\circ in$$ $$t = 2$$ seconds?

Accepted Answer

Sternocleidomastoid; $$\omega = \frac{	heta}{t} = \frac{\pi/2}{2} = \frac{\pi}{4}\ 	ext{rad/s}$$

Question 11

A patient is unable to extend their fingers. Which muscle is most likely affected?

Accepted Answer

Extensor digitorum

Question 12

Which muscle is primarily responsible for plantar flexion of the foot, and what is the equation for work ($$W) $$done if the force ($$F) is 200 N $$and the distance ($$d) $$moved is 0.05 m?

Accepted Answer

Gastrocnemius; $$W = F 	imes d = 200 	imes 0.05 = 10\ 	ext{J}$$

Question 13

Which muscle is most involved in smiling, and what is the physiological mechanism behind this action?

Accepted Answer

Zygomaticus; It elevates the corners of the mouth by contracting.

Question 14

A patient is unable to rotate their arm laterally at the shoulder. Which muscle is most likely impaired?

Accepted Answer

Infraspinatus

Question 15

Which muscle is responsible for flexing the thigh at the hip joint, and what is the equation for power ($$P) if $$the force ($$F) is 150 N $$and the velocity ($$v) is 0.2 m/s$$?

Accepted Answer

Iliopsoas; $$P = F 	imes v = 150 	imes 0.2 = 30\ 	ext{W}$$

Question 16

A patient is unable to compress their abdomen during forced expiration. Which muscle is most likely compromised?

Accepted Answer

Transversus abdominis

Question 17

Which muscle is primarily responsible for adduction of the thigh, and what is the equation for calculating the resultant force ($$F_{res}) if $$Adductor longus and Adductor magnus each generate 80 N at an angle of $$30^\circ to $$each other?

Accepted Answer

Adductor longus; $$F_{res} = \sqrt{80^2$ + 80^2$ + 2 	imes 80 	imes 80 	imes \cos(30^\circ)} \approx 151.6\ 	ext{N}$$

Question 18

A patient is unable to extend their leg at the hip joint. Which muscle is most likely impaired?

Accepted Answer

Gluteus maximus

Question 19

Which muscle is responsible for elevating the scapula, and what is the equation for mechanical advantage ($$MA) if $$the effort arm ($$d_e) is 0.04 m $$and the load arm ($$d_l) is 0.02 m$$?

Accepted Answer

Trapezius; $$MA = \frac{d_e}{d_l} = \frac{0.04}{0.02} = 2$$

Muscular System: Surface Muscles Identification and Functions

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