Explain the concept of muscle contraction based on neuroelectrical, chemical and energy sources.
Potassium ions are more prevalent within the muscle that they are outside, while sodium ions are greater on the outside. The inner part of the cells is negatively charged compared to the outside which is positively charged. When a nerve impulse reaches a neuromuscular junction, it causes the endings of the axons to release neurotransmitter acetylcholine (Rizzo 9-3a). The action therefore causes the cell membrane to become permeable to the sodium ions. The Na+ rush in making the potassium ions to rush out in an effort to restore the resting potential. Since the potassium ions are not enough compared to sodium ions, they are unable to restore balance. The muscle cell therefore generates its own action potential that penetrates deep into the muscle fiber through the T-tubules. It resultantly causes the release of Calcium ion from the sarcoplasmic reticulum. The calcium ions are released to the fluids around the myofibrils. The calcium ions stop the actions of the inhibitor elements (tropomyosim and troponin) which cause the contraction process to occur.
The calcium ion combines lightly with myosin to form stimulated myosin, which reacts with ATP also attached to the myosin. The reaction releases energy to form actomyosin. Mysosin filaments pull and connect with the actin filaments causing an increase in the width of the Z lines to reduce but the A bands to remain the same (Rizzo, 9.4a). At this moment, the sodium-potassium pump joins in to restore the resting potential. The Calcium ions are absorbed to stop the contraction process.
Glycosis occurs changing glucose into pyruvic acid with a net gain in 8ATP if oxygen is present. When oxygen is absent then lactic acid forms but with a gain of 2 ATP. The Krebs Citric acid cycle then follows, which converts pyruvic acid into carbon 2 oxide, water and a total of 30ATPsPhospohocreaticn also occurs in muscles cells and the combustion of free fatty acids, all producing an extra ATP. The ATPs produced are use within the contraction process.
- Name and give the location for 10 major superficial muscle of the body.
- 1 from the head
Mentalis – it originates from the mandible ( lower jaw) and terminates in the lower part of the chin.
- 1 from the neck
Pltysama located in the upper chest and shoulders and extends along the collarbone and the neck sides then continues to the lower jaw.
- 1 from the chest
Pectoralis Major – it originates from intertubular sulcus of the humerus with two heads, Each from anterior surface of medial clavicle and anterior surface of the sternum respectively.
- 1 from the abdomen
Eternal oblique – originates from the 5th-12th rib and terminates into iliac crest and pubic tubercle.
- 2 from the arms
Flexor Carpi Ulnaris – it originates from the medial epicondyle passes through the wrist and ends in the pisiform carpal bone.
Palmaris Longus – originates from medial epicondyle and ends in the flexor retinaculum of the wrist.
- 2 from the legs
Quadriceps femoris – it is composed of four muscles. The Vatus lateralis, medialis and intermidus originates from the femur and end in the patella. The rectus femoris originates from the pelvis and attaches to the patella.
Sartorius – originates from the pelvis and terminates in the tibia.
- 2 from anywhere
Trapezius – located on the back. It originates from the spine of the shoulder blades and terminates in the collar bone
Sternocleidomastoid muscle – it starts at the base of the skull to the lower thoracic vertebrae of the spine.
- Myasthenia Gravis
Myasthenia gravis is a muscle problem characterized by weakness and rapid fatigue of any of the muscles within your voluntary control. It starts because of breakdown in the normal communication between the muscle and the nerves.
In Eye Muscles
Drooping on one or both of the eyelids
Double vision, either horizontally or vertically
In Face or Throat Muscles
Impairment in speaking
Difficulty in swallowing
Difficulty in chewing/ Wearing out
Change in facial expressions
In the Neck and Lib Muscles
Weaknesses within the arms, legs and neck. Can affect your walking if in legs and the neck has difficulty holding the head.
People Likely to Face the Disease
It can affect people of all ages
Affects mostly men older than 60 and women younger than 40
People who have family history of autoimmune diseases
The disease has no cure
- I]t is howver treated with medication with a drug called pyridostigmine (Mestinon). It can also be used with an autoimmune therapeutic option
- In severe cases, the blood may need replacement with an antibody free plasama.
- Surgery is also a treatment option.
Rizzo, Donald C. Fundamentals of anatomy and physiology. Cengage Learning, 2015.