Heart and cardiac muscle (wk6) Flashcards
Describe the heart in the thoracic cavity:
Heart in the thoracic cavity:
-The heart is located within the thoracic cavity, which is the 2nd largest hollow space of the body. The thoracic cavity is enclosed by the ribs, the vertebral column, and the sternum, and is separated from the abdominal cavity by the diaphragm.
-The heart is pushed to the left side of the sternum, which means that the left lung is a bit smaller to accommodate the heart taking up the space
Describe the external anatomy of the heart
-Pericardium, pericardial fluid
-The heart is surrounded by a fibrous sac called the pericardium. It is a structure of 2 layers, one on the inside attaching to the actual muscle of the heart and then on the outside layer of the heart.
-The pericardium protects the heart by providing lubrication during its constant movement. Pericardial fluid is found in between the 2 layers of the pericardium. It acts as lubrication for the heart because the heart creates lots of friction as it works very hard, so is able to minimise the inflammation from it. The pericardium and the fluid are able to reduce the clinical cardiology condition that is when people get inflammation of the fat of the muscle, which creates swelling and limits the amount of contractions the heart can achieve because it’s contained in such a small space.
-It also helps anchor the heart against the diaphragm and spine
Annotate a diagram of the external anatomy of the heart
Describe the internal anatomy of the heart
-Coordinate collection and right side of the heat
Internal anatomy of the heart:
-The heart has its own blood supply, from the coronary arteries (coordinate collection). The coordinate collection is a system that the heart has to receive blood so that it can operate like other muscles in the body.
-The right side of the heart is the blude side and received blood from the body. The blood has gone around the body and released some oxygen, meaning it has a lower oxygen content and is returning into the heart to be pumped into the lungs. It can pick up a fresh oxygen supply and get rid of waste that it has picked up from going around the tissues.
Describe the internal anatomy of the heart
-Left side and atria
-The left side of the heart is receiving fresh oxygenated blood from the air from the lungs, into the ventricles, which is then pumped out into the body so that it can support the medical, metabolic and other functions of the different tissues
-The top part of the heart is the atria which are the receiving chambers.
Annotate a diagram of the internal anatomy of the heart
Describe the internal anatomy of the heart
-Vena cava
-Vena cava -> The biggest veins that we have in our body. We have the superior vena cava that returns the deoxygenated blood from the systematic circulation to the right atrium and the inferior vena cava that receives blood from the body below the heart.
-When blood arrives to the cava, it enters the 1st chamber of the heart, the right atrium and one of the receiving chambers. The right atrium has the ability to contract slightly which pushes the blood through the first part to the heart
Describe the internal anatomy of the heart
-Bicuspid and tricuspid valve and veins
-Bicuspid valve (mitral valve) -> One of the heart’s 4 valves that help prevent blood from flowing backwards as it moves through the heart.
-Tricuspid valve -> This valve is on the left side of the heart and the mitral valve is in the left ventricle, which is the stronger ventricle of the heart. This means that more blood can be pushed through the aortic valve and the bigger bout of blood in the heart into the aorta and the main arteries is able to supply blood to the arms and legs.
-Veins towards the heart and arteries away from the heart
Describe the heart valves
-Atrioventricular valves, mitral valves and coronary artery
-Atrioventricular valves -> They separate the atria from the ventricles. They are bigger because they need to allow blood to flow passively. They don’t have a lot of force by contracting so blood passively goes through the vent through the balance.
-Mitral valve -> Is also called bicuspid because it only has 2 flaps, not 3, meaning that they have to control the ejection of the blood from the ventricles at the front of their infrastructure
-Coronary artery -> It is located just outside of the aortic valve. It’s the 1st recipient of the freshly oxygenated blood that comes from the air. In the diagram, the aortic valve is found in the core of the heart valve structure and demonstrates how the valve is open which allows the blood flow through, and when the pressure goes down, it eventually relaxes the gap to go back down to prevent blood going in the opposite direction.
Annotate a diagram of the heart valves
Describe cardiac muscle
-Characteristics etc
-Cardiac muscle is similar to skeletal muscle in terms of its structure, but it operates similarly to smooth muscle (involuntarily)
-It has striations and repeated sgments along the muscle fibres
-The heart/ cardiac muskce isn’t controlled voluntarily, however it can be influenced emotionally. This is because the heart is operated by the nervous system without conscious direct involvement.
-The muscle fibres in cardiac muscle are mechanically associated with one another through decimal forms which are part of the surface, which tethers the meuscle fibers together. This means that movement in 1 is translated to a movement in the next one.
Describe cardiac muscle
-Gap junctions and activation phase
-Gap junctions -> These are the electrical and chemical connections between fibres. This means that electrical activity that is generated in on and part of the heart can travel through the heart muscle in an organised fashion. This high organisation means that blood can be directed at the right time to the right point and the contraction of the ventricles is organised that it can push the valves to allow the blood to leave. The orchestrated contraction of the heart is made possible by the organised passage of the signal through the force that we have at the end of the fibres in conductivity.
-Activation phase -> The activation in the cardiac muscle depends on the depolarisation of the potassium channel, which when it opens, it polarises the membrane of the muscle fibre. The calcium channel also opens, but from into the cell from the outside of the muslce fibre (the calcium inside the muscle activates the receptor on the reticulum). This mean that the more calcium releases, the greater the contraction force the muscle will have.
Describe signal propogation in the heart
The gap junctions allow an electrical signal to originate from a specialized part of the heart and propagate from fibre to fibre in a structured and organized pattern
+Draw the diagram
Describe EEC in cardiac muscle:
-Excitation-contraction reaction in cardiac v skeletal muscle -> The contraction of cardiac muscle cells is dependent on extracellular Ca2+
-Cardiac muscle -> The fibres contract via excitation-contraction coupling, using a mechanism unique to cardiac muscle called calcium-induced calcium release. This release involves the conduction of calcium ions into the cardiomyocyte, triggering further release of ions into the cytoplasm.
-Calcium prolongs the duration of muscle cell depolarization before repolarization occurs. Contraction in cardiac muscle occurs due to the binding of myosin heads to ATP, which then pulls the actin filaments to the centre of the sarcomere, the mechanical force of contraction.
Describe EEC in skeletal muscle:
The excitation-contraction coupling in skeletal muscle refers to the Ca 2+ mediated link between the membrane excitation and the mechanical contraction.
