Page 17 - Human anatomy COMPLETELY DONE1

movements of the arm and its departments.
PELVIC GIRDLE AND LEG MUSCLES:
-Pelvic muscles provide hip movement.
-The thigh muscles are involved in the movement of the thigh and lower leg.
-The muscles of the lower leg are necessary for the movement of the foot.
-The muscles of the foot bend and unbend the toes.
FEATURES OF MUSCLE WORK
Most skeletal muscles move one or another joint. There are flexor muscles,
extensors, adductors of the joint, withdrawing joint, rotators of the joint.
Usually, several muscle groups participate in any joint movement. The muscles
that jointly participate in any joint movement are called synergists, and the muscles
involved in the movement of the same joint in the opposite direction are called
antagonists. For example, in the elbow joint, the flexor (biceps muscle) and the extensor
(triceps muscle) are antagonists.
By contracting, the muscle acts on the bone as a lever and performs mechanical
work. Muscle contraction requires energy.
Flexion in the joint is carried out with the contraction of the flexor muscles and
simultaneous relaxation of the extensor muscles. Their coordinated activity is possible
due to the alternation of excitation and inhibition processes in the nerve cells of the
spinal cord. For example, the contraction of the flexor muscles of the arm is caused by
the excitation of motor neurons of the spinal cord. At the same time, the extensor
muscles relax. This is due to the inhibition of other motor neurons associated with
extensor muscles.
The flexor muscles and extensor muscles of the joint can simultaneously be in a
relaxed state. So, the muscles of the arm hanging freely along the body are in a state of
relaxation. When holding a heavy object in a horizontally extended arm, there is a

simultaneous contraction of both flexors and extensors of the joint.

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