Cardiovasular System Flashcards
Identify the types of vessels that make up the circulatory system
Arteries
Anastomic arteries (connecting arteries)
Arterioles
Capillaries
Venules
Veins
Describe the structure and function of arteries
Arteries: thick walls, withstand high pressure. Structure depends on how close to heart. E.g tunica media = lots of elastic tissue, little smooth muscle, allowing to stretch and absorb pressure. Elastic decreases, smooth muscle increases as the arteries branch and become smaller
Describe the structure and function of arterioles
Arterioles: consist mainly of smooth muscle. Contraction and relaxation of smooth muscle allows precise control of their diameter
Describe structure and function of venous walls
Venules: they are thinner that atrial walls, but have the same three layers of tissue. This is because they have to withstand less pressure
Describe structure and function of veins
Veins: some large veins possess valves, which help prevent backflow
Describe how the pressure changes as blood progresses from the arteries through the venous system
Blood pressure is high when travelling through the arteries
Blood pressure drops significantly when travelling through the capillary beds (allowing diffusion of small molecules)
Blood then travels through the venous system at a lower pressure due to this
Describe the role of the skeletal muscles and valves in return of blood to the heart
The contraction of skeletal muscles surrounding the deep veins compresses them, pushing blood towards the heart
Valances prevent backflow to ensure blood is travelling in the right direction
Define pulse
A rhythmic throbbing of arteries as blood is propelled through them, usually felt in the wrists or neck.
The number of pulse beats per minute normally represents heart rate, and varies considerably from person to person.
Describe the position of the heart, its shape and relationship to the lungs, major vessels, diaphragm and oesophagus
The heart lies obliquely in the thoracic cavity in the mediastinum (the space in between the lungs), slanted slightly to the left
The apex (tip of the heart) is positioned inferiorly, resting on the central tendon of the diaphragm
The major blood vessels e.g. Aorta are positioned superiorly, entering the heart at its base
The oesophagus is positioned posteriorly
Describe blood flow through the heart from the pulmonary to systemic circulation
Pulmonary moves blood between the heart and lungs (deoxygenated blood) —> oxygen poor from all over body enters right atrium through inferior and superior vena cava, tricuspid valve opens, blood travels from right atrium to right ventricle, when full it squeezes, closing tricuspid valve, opening pulmonary valve, blood flows from pulmonary artery to lungs
Systemic moves blood between heart and rest of the body (oxygenated blood)—> oxygen rich travels from lung to left atrium through pulmonary vein, mitral valance opens, blood into left ventricle from atrium, left ventricle full, squeezes closing mitral valve, opening aortic valve, heart send blood to your organs, where it flows to the rest of the body
Outline the function of the heart and a pump including the vents through one cardiac cycle
The heart goes through a rhythmic cycle of contraction and relaxation, which 3 main stages
Complete cardiac diastole- it is the rest period between beats, the myocardium in the atria and ventricles are complete relaxed
Atrial systole- atrial contraction
Ventricular systole- ventricular contraction
The valves open and close according to the pressure within the chambers of the heart. This ensures blood only flows in one direction.
Describe the conduction system of the heart
The heart posses a property of autorhythmicity, which means it generates its own electrical impulses and beats independently, it is not reliant on external mechanisms to innate each heartbeat
It is supplied with both sympathetic and parasympathetic nerve fibres, which increase and describes the intrinsic heart rate
The heart responds to a number of hormones
Specialised neuromuscular cells in myocardium initiate and conduct impulses, causing coordinated and synchronised contraction
Define the terms blood pressure and peripheral resistance
Blood pressure: the force of circulating blood on the walls of your arteries
Peripheral resistance: the resistance of the arteries to blood flow. There are 3 factors that affect it
1) autonomic activity
2) blood viscosity
3) medications
Explain how cardiac output and peripheral resistance generates blood pressure
If the body needs more oxygen:
Cardiac output increases so that more oxygen is available throughout the body. It does this by increasing heart rate and total peripheral resistance (through vasoconstriction)
This increases blood pressure
Outline the location and role of baroreceptors and the medullary cardiovascular centre in the control of blood pressure
Baroreceptors are located within the wall of the aortic and carotid sinuses. They are nerve endings sensitive to stretch. They are responsible for the baroreceptor reflex, the body’s main mechanism for controlling blood pressure.
They continuously feed information into the CVC (located in the medulla) regarding the degree of stretch in the arterial walls, which directly reflects the pressure in the vessel.
