Cardiovascular.pdf

CARDIOVASCULAR PATHOPHYSIOLOGY Describe cardiac anatomy 1. Chambers: The heart consists of four chambers: Right Atrium: Receives deoxygenated blood from the body via two large veins called the superior vena cava and inferior vena cava. Right Ve...

CARDIOVASCULAR PATHOPHYSIOLOGY Describe cardiac anatomy 1. Chambers: The heart consists of four chambers: Right Atrium: Receives deoxygenated blood from the body via two large veins called the superior vena cava and inferior vena cava. Right Ventricle: Receives blood from the right atrium and pumps it to the lungs through the pulmonary artery for oxygenation. Left Atrium: Receives oxygenated blood from the lungs through the pulmonary veins. Left Ventricle: Receives blood from the left atrium and pumps it into the aorta, which distributes oxygenated blood to the entire body. 1. Valves: There are four heart valves that ensure unidirectional blood flow: Tricuspid Valve: Separates the right atrium from the right ventricle. Pulmonary Valve: Located between the right ventricle and the pulmonary artery. Mitral (Bicuspid) Valve: Separates the left atrium from the left ventricle. Aortic Valve: Located between the left ventricle and the aorta.  2. Blood Vessels: Vena Cavae: The superior vena cava brings deoxygenated blood from the upper body to the right atrium, and the inferior vena cava brings deoxygenated blood from the lower body to the right atrium. Pulmonary Arteries: Carry deoxygenated blood from the right ventricle to the lungs for oxygenation. Pulmonary Veins: Transport oxygenated blood from the lungs to the left atrium. Aorta: Distributes oxygenated blood from the left ventricle to the rest of the body. 3. Layers of the Heart Wall: Pericardium: A double-layered sac that encases the heart and provides protection. Myocardium: The muscular middle layer responsible for contracting and pumping blood. Endocardium: The innermost layer that lines the chambers and valves, providing a smooth surface for blood flow. 4. Electrical System: The heart's rhythm is controlled by an electrical system that originates in the sinoatrial (SA) node and travels through the atrioventricular (AV) node and the bundle of His, causing coordinated contractions. Discuss normal cardiac physiology including: Normal contraction Cardiac output Blood pressure control - vasculature Normal Contraction: The heart's contraction is coordinated by electrical signals that travel through specialised pathways. The heartbeat is initiated in the sinoatrial (SA) node, located in the right atrium. This node generates electrical impulses that cause both atria to contract simultaneously, pushing blood into the ventricles.  The impulses then travel to the atrioventricular (AV) node, which briefly delays the signal to allow the ventricles to fill with blood. From the AV node, the electrical signal travels down the bundle of His and its branches, causing the ventricles to contract and pump blood to the lungs and the rest of the body. Cardiac Output: The amount of blood pumped by the heart per minute → determined by both heart rate (number of heartbeats per minute) and stroke volume (the amount of blood pumped with each heartbeat). The formula for cardiac output is: ○ Cardiac Output (CO)= Heart Rate × Stroke Volume ^^heart rate or stroke volume → ^^cardiac output. Blood Pressure Control - Vasculature: Blood pressure is the force exerted by blood against the walls of blood vessels. It is regulated through various mechanisms to maintain stable circulation: ○ Vasoconstriction and Vasodilation Blood vessels can constrict (narrow) or dilate (widen) due to signals from the nervous system and local chemicals. Constriction increases resistance, raising blood pressure, while dilation decreases resistance, lowering blood pressure. ○ Baroreceptor Reflex Baroreceptors monitor blood pressure. If blood pressure rises too high, the baroreceptors send signals to the brain, which in turn sends signals to the heart and blood vessels to lower blood pressure by reducing heart rate and causing vasodilation. ○ Renin-Angiotensin-Aldosterone System (RAAS) This hormonal system helps regulate blood pressure. When blood pressure drops, the kidneys release an enzyme called renin. Renin initiates a chain reaction that leads to the formation of angiotensin II, a potent vasoconstrictor. Angiotensin II also stimulates the release of aldosterone, which promotes salt and water retention, raising blood volume and pressure ○ Sympathetic and Parasympathetic Nervous System The sympathetic nervous system releases adrenaline and noradrenaline in response to stress or exercise. These hormones increase heart rate, cardiac contractility, and vasoconstriction → ^ blood pressure. The parasympathetic nervous system, through the vagus nerve, can slow heart rate and reduce blood pressure. Describe the measurements used to assess cardiac function Electrocardiogram (ECG) An ECG records the electrical activity of the heart → provides information about heart rate, rhythm, and any abnormalities in the electrical conduction pathways. Specific components of an ECG include the P wave (atrial depolarization), QRS complex (ventricular depolarization), and T wave (ventricular repolarization). Electrodes are placed on the skin using ECG stickers Regularity of the cardiac electrical events or other electrical events can be electrically filtered out Discuss the pathophysiology of heart failure Heart failure: when the heart does not generate sufficient cardiac output to meet the body’s metabolic needs (for 02, etc) HF with reduced ejection fraction (systolic heart failure) is most common → ventricular filling is normal/increased, but less blood is ejected due to muscle weakness HF with preserved ejection fraction (diastolic heart failure) → due to a stiff ventricle that doesn’t relax properly → inadequate filling of the ventricle Left ventricular failure aka congestive heart failure is most common → due to greater demands on the left ventricle High output HF → when cardiac output is normal/higher but there’s still inadequate supply of O2, etc to the tissues Causes ○ Ischemic heart disease ○ Hypertension ○ Idiopathic dilated cardiomyopathy Describe common pathophysiology of the cardiovascular system. Atherosclerosis The buildup of fatty deposits (plaques) in the inner walls of arteries. Over time, these plaques can narrow and harden the arteries, reducing blood flow. Inflammation, oxidative stress, and endothelial dysfunction play key roles in the initiation and progression of atherosclerosis. Hypertension When the force of blood against the walls of arteries is consistently too high. It can result from increased cardiac output, increased systemic vascular resistance, or both. Over time, hypertension can damage blood vessels, leading to atherosclerosis, vascular stiffness, and increased risk of heart attack and stroke. Heart Failure A condition in which the heart's pumping ability is compromised. It can be due to weakened heart muscles (systolic dysfunction) or impaired relaxation and filling (diastolic dysfunction). Common causes include hypertension, coronary artery disease, and cardiomyopathies. Compensatory mechanisms, such as sympathetic activation and fluid retention, initially help maintain cardiac output but can become detrimental in the long term. Ischemic Heart When there's reduced blood flow to the heart muscle due to narrowed or Disease blocked coronary arteries. This can lead to angina (chest pain) or heart attack (myocardial infarction). (Coronary Atherosclerosis is a major contributor to this condition. Artery Disease) Arrhythmias Abnormal heart rhythms that can result from disruptions in the heart's electrical conduction system. These disturbances can lead to tachycardia (fast heartbeat) or bradycardia (slow heartbeat), affecting the heart's ability to pump blood effectively. Valvular Heart Involves problems with the heart's valves, such as stenosis (narrowing) or Disease regurgitation (leakage). These issues can lead to inefficient blood flow, increased workload on the heart, and potential heart failure. Cardiomyopath Affect the heart muscle, leading to structural and functional abnormalities. ies Hypertrophic, dilated, and restrictive cardiomyopathies are common types These conditions can impair the heart's ability to pump blood effectively. Thrombosis Blood clot formation (thrombosis) can occur within blood vessels, leading to and Embolism reduced blood flow or complete blockage. Clots can also dislodge and travel to other parts of the body (embolism), causing further complications. Describe cardiac conduction. NEURAL PATHOPHYSIOLOGY Discuss the structure and function of the nervous system. Functions of CNS CNS = brain + spinal cord Processes and coordinates sensory data from inside and outside the body Motor commands control activities of peripheral organs (e.g., skeletal m.m.) Higher functions of brain include intelligence, memory, learning, and emotion Adult brain regions (outer grey matter, centre white matter) 1. Cerebrum = cerebral hemispheres 2. Diencephalon (thalamus, hypothalamus, epithalamus) 3. Brain stem (midbrain, pons, and medulla) 4. Cerebellum Spinal cord ○ Carries sensory info to the brain, transmits information from the brain to the effector organs ○ Central cavity surrounded by grey matter ○ External white matter composed of myelinated fibre tracts Functions of PNS PNS: all nervous tissue outside CNS and ENS Delivers sensory information to the CNS  Carries motor commands to peripheral tissues Nerves (peripheral nerves) ○ Bundles of axons with connective tissues and blood vessels ○ Carry sensory information and motor commands ○ Cranial nerves connect to brainstem ○ Spinal nerves attach to spinal cord Somatic Nervous System: ○ Responsible for voluntary movements and sensory perception. It controls skeletal muscles and processes sensory information from external stimuli, transmitting it to the CNS for further processing. Autonomic Nervous System (ANS): ○ Regulates involuntary bodily functions, such as heartbeat, digestion, and breathing. ○ Sympathetic → "fight or flight" response, preparing the body for action in times of stress or danger ○ Parasympathetic → "rest and digest" response, facilitating activities like digestion and relaxation. Neurons and Glial Cells: Neurons are specialised cells that transmit electrical and chemical signals (nerve impulses) throughout the body. ○ Consist of a cell body, dendrites (receiving extensions), and an axon (transmitting extension) ○ Communicate with each other through synapses, tiny gaps between axons and dendrites where neurotransmitters are released. Glial cells support and protect neurons. ○ Providing structural support ○ Insulating neurons (like myelin sheaths around axons) ○ Regulate the chemical environment around neurons. Outline how alterations to normal neural physiology can result in disease. Tumours of the Primary tumours: CNS ○ Intracerebral tumours arise from: Astrocytes – astrocytomas Oligodendrocytes – oligodendrogliomas ○ Extracerebral tumours arise from: Meningiomas Pituitary and pineal glands tumours Secondary or metastatic: ○ cancer originates outside the brain, but has spread to the brain. Symptoms may be localised or generalised depending on size and location. ○ Seizures ○ loss of equilibrium Nerve Injury and Most axons are myelinated: Regeneration ○ myelin increases the speed of nerve conduction. Nerves can only repair themselves if: ○ injury occurs in the PNS and; ○ injury occurs near the distal end of the axon. Demyelination in A chronic autoimmune, inflammatory demyelinating disease of CNS and CNS: optic nerve. Many genes (>200) and vitamin D deprivation during gestation increase the risk of MS. Multiple Sclerosis Eventually the axon is permanently damaged, leading to loss of myelin and (MS) permanent symptoms Progressive (20 yrs of more) loss of function à permanent disability. Symptoms usually remit (apparent absence of disease), partially or completely, wks after the onset of an early episode. ○ They vary depending on the location of lesion Loss of coordination and tremor speech diff., extreme fatigue, visual disturbances, memory loss