. Physiology, experimental and descriptive . me after it isremoved from the body. This is regarded by many as due tothe action of certain ganglia imbedded in the walls of theheart, especially in the auricles; while others say that sincethe ventricle, in which no gangliahave been found, may beatindependently of the auricles, rhythmic contraction is charac-teristic of heart muscle, and that we are at present unable toexplain it. But while the impulses that originate the action of theheart arise within the heart itself, still the beat of the heartis constantly modified by iierve impulses reaching
. Physiology, experimental and descriptive . me after it isremoved from the body. This is regarded by many as due tothe action of certain ganglia imbedded in the walls of theheart, especially in the auricles; while others say that sincethe ventricle, in which no gangliahave been found, may beatindependently of the auricles, rhythmic contraction is charac-teristic of heart muscle, and that we are at present unable toexplain it. But while the impulses that originate the action of theheart arise within the heart itself, still the beat of the heartis constantly modified by iierve impulses reaching it fromwithout. The heart receives its nerves from two sources, the Sym-pathetic System and the Pneumogastric Nerves. The Sympathetic Nervous System consists of two rows of PNEUMOGASTRIC NERVES. 91 ganglia in the body cavity, one along each side of the spinalcolumn, receiving branches from the spinal nerves, and sendingbranches to all the internal organs of the body, ?— the heart andlungs in the thorax, and the Sympathetic Nerve Chains. Fig. 33, Relation of Spinal Cord andSympathetic Nervous System (Diagram). stomach, intestines, and theother organs of the abdominalcavity. In many places thesenerves form a thicknetwork called aplexus. One verylarge plexus is onthe posterior sur-face of the stomach, and iscalled the Solar Plexus. The Pneumogastric Nervesare a pair of the cranial nervesarising from the sides of thespinal bulb; and, passing downward, they give branches to the pharynx, gullet, and stom-Spinai Cord ach, the larynx, windpipe, and lungs, and theheart. Now, what-ever other functionthe pneumogastricnerves may have, theyseem to have the power ofretarding, or stopping al-together, the beat of theheart; and stimulation ofthe pneumogastric nerves may make the heart pause in a re-laxed condition. Other nerves may quicken the heart-beat,but the pneumogastrics are regarded as a brake on the heartsaction.
Size: 1831px × 1365px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauth, bookcentury1800, bookdecade1890, bookidcu31924031272762
