Cardiac, Lymphatic, and Respiratory Systems
Explain: How Heart Muscle Fibers Contract and the Pacemaker’s Role?
Cardiac muscle also consists of sarcomeres containing alternating thick and thin filaments. The cells tend to contract rhythmically and spontaneously, but these contractions are synchronized by electrical signals produced by specialized, highly developed muscle fibers of the sinoatrial node. Cardiac muscle fibers are electrically interconnected links between cells located interspersed, which allows for coordinated contraction. Specialized fibers act as a pacemaker. Action potentials that originate in the pacemaker spread quickly through the heart using specialized areas in which interspersed links connect adjacent muscle cell membranes, allowing the potential to synchronize their contractions as they travel from one cell to another.
The Lymphatic System in Circulation
The lymph nodes in the system have antibodies, lymphocytes, and plasma proteins that leak into the bloodstream to defend the body. It is a great fighter against infection and filters the lymph through lymph nodes, where white blood cells ingest foreign invaders such as viruses and bacteria. The lymphatic system consists of lymphatic vessels, tonsils, lymph nodes, the thymus, and the spleen. It removes excess interstitial fluid that seeps from the walls of blood vessels to remove waste and recycle items, which then returns to the circulatory system. It transports fat into the bloodstream from the small intestine. The thymus is most active in young children and produces lymphocytes involved in immunity. The spleen filters blood by passing it through macrophages and lymphocytes, which kill bacteria and damaged blood cells.
Tracheal Breathing:
The tracheae are a system of internal tubes that carry air directly to branched cells in the body. They subdivide and branch to form tracheoles, or smaller canals that penetrate the tissues of the body and allow the exchange of gases. Each cell in the body is near a tracheole. Air enters the tracheae through a series of openings called spiracles, which have valves that allow opening or closing. Large insects use body muscle movements in the abdomen to ensure the movement of air in the tracheae.
The Human Respiratory System:
The human respiratory system consists of a conductive portion and a gas exchange portion. The air first passes through the conductive portion, which consists of the nose and mouth, pharynx, larynx, trachea, bronchi, and bronchioles, and reaches the gas exchange portion, consisting of alveoli (microscopic sacs). The blood is within a dense network of capillaries surrounding the alveoli; they release carbon dioxide and absorb oxygen from the air. Almost all the oxygen in the blood is bound to hemoglobin in red blood cells. Hemoglobin binds oxygen in concentrations representative of those observed in the alveolar capillaries and releases lower concentrations of oxygen to the tissues. Carbon dioxide diffuses into the blood from tissues and is transported as bicarbonate, bound to hemoglobin, or dissolved in the plasma. Breathing actively sucks air into the lungs by contracting the diaphragm and rib muscles, which expands the chest cavity. Relaxation causes the chest cavity to collapse and release the air. Breathing is controlled by nerve impulses that originate in the respiratory center in the medulla oblongata. The rate of respiration is controlled by receptors such as the medulla, which monitor carbon dioxide levels in the blood.