One half of a heartbeat diastole is the sound of the mitral and tricuspid valves closing. The other half systole is the sound of the aortic and pulmonary valves closing.
During diastole, the ventricles relax and fill with blood. During systole, they contract and pump blood out to the body. The rate and force of contraction of the heart and the degree of narrowing or widening of blood vessels are controlled by several hormones and by the autonomic nervous system the part of the nervous system that controls involuntary activity. The heart beats because of a tiny electrical current that begins in the sinoatrial node. Rhythmic electrical impulses or discharges from the sinoatrial node cause the contraction of muscle fibers in the heart.
While an animal is at rest, the sinoatrial node discharges many times each minute; in a resting cat, it will discharge more than times per minute. Heart rate is also inversely related to blood pressure. When blood pressure increases, heart rate decreases; when blood pressure decreases, heart rate increases. In heart failure, nerve endings that are sensitive to blood pressure changes called baroreceptors report the lower blood pressure to the brain, resulting in an inappropriately elevated heart rate. Unfortunately, this further injures the heart.
Heart sounds are produced by the rapid acceleration and deceleration of blood and the resulting vibrations in the heart due to the circulation of blood. They can be heard using a stethoscope. In cats, 2 heart sounds can normally be distinguished. Heart murmurs are vibrations that can be heard coming from the heart or major blood vessels and generally are the result of turbulent blood flow or vibrations of heart structures such as part of a valve.
Murmurs are typically described by their timing that is, whether they occur during diastole, systole, or continuously , their intensity that is, whether they can be heard easily or with difficulty , and their location. Not every murmur indicates a heart disorder; for example, innocent murmurs are sometimes detected in healthy kittens less than 3 months of age. Arrhythmias are abnormalities of the rate, regularity, or site of heartbeat formation.
The chances are considerably greater in purebred cats; but because there are so many more random-bred cats than purebreds, statistics are misleading. Veterinarians see more cases in middle-aged male cats than females [ at some facilities 3: Among the purebred cats, Maine Coon, Ragdoll, British Shorthair, Bengals, Norwegian forest, Sphynx, Chartreux and Persian cats see more of this problem that house cats originated from unplanned, random litters.
Since cat breeders are more alert to the problem they are also more likely to discover these heart illnesses early in their cat's lives than is a casual cat owner. Not every case of heart failure in cats is due to cardiomyopathies. As in all animals and humans, hearts sometimes just develop wrong. Most folks speak about three types. Hypertrophic cardiomyopathy is by far the most common form of cardiomyopathy. HCM is caused by defective genetic instructions on how the heart should be built.
These cats develop a heart with walls too thick hypertrophy and heart muscles too powerful for proper heart function. At that point, all forms of heart failure are the same congestive heart failure in their signs and symptoms.
The blood then flows through the pulmonary veins into the left atrium. Body plan Decapod anatomy Gastropod anatomy Insect morphology Spider anatomy. That action " dries " out their excessively " wet " lungs and allows cats with HCM to breath more easily. Heart sounds are produced by the rapid acceleration and deceleration of blood and the resulting vibrations in the heart due to the circulation of blood. When the pelvic limb is lifted off the ground, contraction of the caudofemoralis causes the limb to abduct and the shank to extend by extending the hip joint. Retrieved 26 February It is occasionally given to cats with HCM in an attempt to lessen these abnormal heart beats — particularly when they occur in the left upper heart chamber where arrhythmias atrial fibrillation and blood turbulence are thought to encourage the formation of blood clots.
In Maine Coon cats and Ragdolls, the defective gene has been identified. Although the known genes that are responsible for HCM are dominant — that is only one bad one of a two-gene pair is necessary to cause the problem — a phenomenon called incomplete penetrance protects some cats who are carriers from ever developing the disease. In cats where the pair of genes are both defective, most do go on to develop the disease. In this form of cardiomyopathy, scaring fibrosis interferes with the normal expansion and contraction of the heart chambers The heart becomes too "stiff".
All degrees of scaring are possible. In some cases, only limited areas of the heart are affected; in others, the entire organ. Veterinarians know considerably less about what is going wrong in these hearts than we do about cats with HCM. As with HCM, males seem a bit more likely to develop the problem. When the restrictive form occurs, symptoms are the same in both forms. Scaring is usually associated with trauma or inflammation.
But a Japanese group that examined many cats with RC thought it more likely that it occurred due to errors in cell organization and development. DCM was the most common form of cardiomyopathy in cats before It became the least common cause after it was discovered that most cases were due to a taurine deficiency.
For them, it is an essential amino acid that they must obtain from their diet. When due to a taurine deficiency and caught early, many of these problems are reversible. This is the opposite of what occurs in HCD and RC where the heart walls become thicker and muscle bound - but the effect on blood circulation is the same.
The problem usually starts in the left ventricle, spreads to the left atrium and can eventually encompasses the entire organ. All the potential symptoms seen in Hypertrophic cardiomyopathy and Restrictive cardiomyopathy can also occur as a feature of DCM.
When the lack of taurine was the cause, blindness retinal degeneration was also a quite common sign. Veterinarians still encounter an occasion case of dilated cardiomyopathy in cats even though they are eating a taurine-rich diet. So there are apparently other factors involved. Some say that Siamese cats and breeds related to them are more prone to DCM than random bred cats. I do not know if that is true. In humans, about a third of the people that develop DCM inherited their susceptibility to it from their parents.
DCM is still an important health problem in dogs. The cause of DCM in dogs is unknown; but some find taurine and carnitine supplement occasionally helpful.
What Causes Hypertrophic Cardiomyopathy? Defective genes that govern your cat's heart development are the underlying cause of hypertrophic cardiomyopathy. These groups of genes give instructions direct the assembly of the proteins that allow heart muscle to contract. These heart muscle proteins are called myosins. Like all proteins, they are composed of amino acids. When the genes that give instruction on how heart myosins should be assembled have a "typo" error, one or more of the amino acid units that form the myosin molecules is the wrong one. Many genes take part in this building processes.
As of , errors in 11 different genes have been linked to HCM in humans. As I mentioned earlier, cases of cardiomyopathy range from the very mild, and imperceptible where cats act perfectly normal to very severe. In some cats, the disease progresses in severity as time goes by, in others it does not.
Lets talk about the more severe cases: There are two underlying problems that account for all the possible signs. The first is the inability of the failing heart to move blood adequately and the second is the generation of blood clots. Cats with failing hearts lack energy. In some, fluid pools in their tummies as well ascites.
Not feeling their old selves, the cats may become very picky eaters and loose weight. Its origin is from the neural spines of the first four thoracic vertebrae, and its insertion is at the vertebral border of the scapula. Its action is to draw the scapula to the dorsal. The Rhomboideus capitis is the most cranial of the deeper muscles. It is underneath the clavotrapezius. Its origin is the superior nuchal line, and its insertion is at the scapula. Action draws scapula cranially.
The Splenius is the most superficial of all the deep muscles. It is a thin, broad sheet of muscle underneath the clavotrapezius and deflecting it. It is crossed also by the rhomboideus capitis. Its origin is the mid-dorsal line of the neck and fascia. The insertion is the superior nuchal line and atlas. It raises or turns the head. The serratus ventralis is exposed by cutting the wing-like latissimus dorsi. The said muscle is covered entirely by adipose tissue. The origin is from the first nine or ten ribs and from part of the cervical vertebrae.
The serratus dorsalis is medial to both the scapula and the serratus ventralis. Its origin is via apoeurosis following the length of the mid-dorsal line, and its insertion is the dorsal portion of the last ribs. Its action is to depress and retracts the ribs during breathing.
The intercostals are a set of muscles sandwiched among the ribs. They interconnect ribs, and are therefore the primary respiratory skeletal muscles. They are divided into the external and the internal subscapularis. The origin and insertion are in the ribs. The intercostals pull the ribs backwards or forwards. The caudofemoralis is a muscle found in the pelvic limb. When the pelvic limb is lifted off the ground, contraction of the caudofemoralis causes the limb to abduct and the shank to extend by extending the hip joint. Pectoantebrachialis muscle is just one-half inch wide and is the most superficial in the pectoral muscles.
Its origin is the manubrium of the sternum , and its insertion is in a flat tendon on the fascia of the proximal end of the ulna. Its action is to draw the arm towards the chest. There is no human equivalent.
The pectoralis major, also called pectoralis superficialis , is a broad triangular portion of the pectoralis muscle which is immediately below the pectoantebrachialis. It is smaller than the pectoralis minor muscle. Its origin is the sternum and median ventral raphe, and its insertion is at the humerus. The pectoralis minor muscle is larger than the pectoralis major.
However, most of its anterior border is covered by the pectoralis major. Its origins are ribs three—five, and its insertion is the coracoid process of the scapula. Its actions are the tipping of the scapula and the elevation of ribs three—five. The most posterior, flat, thin, and long strip of pectoral muscle is the xiphihumeralis. It is a band of parallel fibers that is found in felines but not in humans. Its origin is the xiphoid process of the sternum. The insertion is the humerus. In the cat there are three thin flat muscles that cover the back, and to a lesser extent, the neck.
They pull the scapula toward the mid-dorsal line, anteriorly, and posteriorly. The most anterior of the trapezius muscles, it is also the largest. Its fibers run obliquely to the ventral surface. Its origin is the superior nuchal line and median dorsal line and its insertion is the clavicle. Its action is to draw the clavicle dorsally and towards the head. Acromiotrapezius is the middle trapezius muscle. It covers the dorsal and lateral surfaces of the scapula. Its origin is the neural spines of the cervical vertebrae and its insertion is in the metacromion process and fascia of the clavotrapezius.
Its action is to draw the scapula to the dorsal, and hold the two scapula together. Spinotrapezius, also called thoracic trapezius , is the most posterior of the three. It is triangular shaped. Posterior to the acromiotrapezius and overlaps latissimus dorsi on the front. Its origin is the neural spines of the thoracic vertebrae and its insertion is the scapular fascia. Its action is to draw the scapula to the dorsal and caudal region. The digestion system of cats begins with their sharp teeth and abrasive tongue papillae, which help them tear meat, which is most, if not all, of their diet.
Cats naturally do not have a diet high in carbohydrates, and therefore, their saliva doesn't contain the enzyme amylase. The gastrointestinal tract of domestic cats contains a small cecum and unsacculated colon. The stomach of the cat can be divided into distinct regions of motor activity.
The proximal end of the stomach relaxes when food is digested. The stomach is not only a muscular structure, it also serves a chemical function by releasing hydrochloric acid and other digestive enzymes to break down food. Food moves from the stomach into the small intestine. The first part of the small intestine is the duodenum. As food moves through the duodenum, it mixes with bile , a fluid that neutralizes stomach acid and emulsifies fat.
The pancreas releases enzymes that aid in digestion so that nutrients can be broken down and pass through the intestinal mucosa into the blood and travel to the rest of the body. Food then moves on to the jejunum. This is the most nutrient absorptive section of the small intestine. The liver regulates the level of nutrients absorbed into the blood system from the small intestine.
From the jejunum, whatever food that has not been absorbed is sent to the ileum which connects to the large intestine. The large intestine reabsorbs water and forms fecal matter. There are some things that the cats are not able to digest. For example, cats clean themselves by licking their fur with their tongue, which causes them to swallow a lot of fur. This causes a build-up of fur in a cat's stomach and creates a mass of fur. This is often thrown up and is better known as a hair ball. The short length of the digestive tract of the cat causes cats' digestive system to weigh less than other species of animals, which allows cats to be active predators.
Cats are not adapted to synthesize niacin from tryptophan and, because they are carnivores, can't convert carotene to vitamin A, so eating plants while not harmful does not provide them nutrients.