W2: Hypertension Flashcards
PBL 2 Drugs Vascular changes
What are the 3 layers of blood vessels and describe them briefly
Tunic Externa: layer of loose, thick connective tissue which has elastic and collagen fibres. It has a supporting function.
Tunica media:
(External elastic lamina: provides recoil to arteries)
circular layer of Smooth Muscle: controls vessel diameter
Tunica intima:
(internal elastic lamina - only in larger arteries)
lamina propria
basement membrane
Endothelial cell: flattened, thin layer which allows blood to flow smoothly.
what are 2 important functional properties of arteries ?
Their elasticity and contractility - comes from elastic tissue
What are the 3 types of arteries? give examples
Elastic arteries: large and bendy, they propel high pressure blood out of the heart. e.g. aorta, common carotid, common iliac, subclavian
Muscular arteries: are less bendy (less elastic fibres and more smooth muscle), Smooth muscle allows them to contract to maintain blood pressure further away from the heart. They are distributing arteries since they repeatedly branch. e.g. radial, ulnar, , femoral, axillary.
Arterioles: resistance vessels which branch not capillaries
Describe some differences between veins and arteries?
Arteries: thickest layer is the tunica media, small lumens
Veins: thickest layer is tunica adventitia, large lumens
What is the cell type found in endothelium?
Simple squamous
What do large veins usually have?
Valves to prevent back flow of blood
Define blood pressure
The hydrostatic pressure of blood exerted against the walls of a blood vessel or heart chamber.
What is systolic blood pressure?
The maximum arterial pressure resulting from the ejection of blood during ventricular contraction.
What is Diastolic pressure?
Arterial blood pressure during ventricular relaxation
What is the calculation for Mean Arterial Pressure?
MAP = Diastolic BP + 1/3 Pulse Pressure
What is the calculation for pulse pressure?
PP = systolic - diastolic
Define MAP
MAP = average pressure in arteries during one cardiac cycle
Describe haemodynamic factors affecting blood pressure
Cardiac Output
Total peripheral resistance:
Blood vessel diameter (smaller the lumen, the greater the resistance)
Blood vessel length (longer the vessel, the greater the resistance)
blood viscosity
Compliance (stretchiness) of blood vessel
Pressure gradient
Describe the neurohormonal factors that affect blood flow?
Autonomic nervous system:
When sympathetic activity is increased, this increases release of noradrenaline. This induces vasoconstriction of blood vessels and increases HR and BP. Parasympathetic activity is inhibited.
Hormonal control: renin-angiotensin-aldosterone system
E.g. if blood pressure is low:
Beta 2 receptors on Juxtaglomerular cells respond to sympathetic nerve stimulation.
They increase Renin secretion in the kidneys which is involved in the conversion of angiotensinogen (produced by the liver) to angiotensin I.
Angiotensin convening enzyme (ACE) which is found in vascular endothelium converts angiotensin I to angiotensin II.
AII has very important functions:
Increases sympathetic activity
Increases tubular Na and Cl reabsorption and H20 retention to increase blood volume and therefore BP.
Increases aldosterone secretion from the adrenal gland
which stimulates tubular Na and H20 reabsorption.
Increases arteriole vasoconstriction to increase BP.
Increases ADH secretion from the pituitary gland which increases water reabsorption from the collecting duct.
If the blood pressure is HIGH:
Atrial-natriuretic peptides: are released form the right atrium. They induce vasodilation and promote Na and water excretion which lowers blood volume and therefore BP.
Define hypertension
Hypertension is a long term medical condition in which arterial blood pressure is persistently elevated
describe the stages of hypertension
Normal BP range: 90-119 / 60-79
Prehypertension 120-139 / 80-89
Stage 1: 140-159 / 90-99
Stage 2: >160 / >100
Describe the 2 types of hypertension and their causes
Primary (95% of cases):
no direct cause but closely linked with poor lifestyle choices e.g. lack of exercise, alcohol, high salt diet, obesity
Secondary: (5% fo cases) usually due to an underlying condition e.g. endocrine issues (Cushing's disease) Renal parenchymal disease Renal artery stenosis Drugs e.e.g NSAIDs
What are the effects of hypertension on the body?
Increased CO
Increased sympathetic activity, particularly in kidneys
increased renin release, angiotensin II, aldosterone etc.
What are the severe consequences of hypertension?
Damages endothelial cells
Increases risk of: Atherosclerosis Stroke Cerebral haemorrhage Heart failure Myocardial infarction Renal failure Retinopathy
Heart disease
Peripheral artery disease
Vascular dementia
Premature death
Describe the responses to changes in posture
When someone goes form supine (lying down) to standing position, the effects of gravity cause venous pooling in the vessels below the heart. This increase venous pressure and, to compensate, the veins dilate and the CO, SV and cardiac filling is reduced.
This hypotension is only transient as the baroreceptor reflex detects the change in pressure.
The baroreceptors decrease their firing rate in response to the low blood volume.. This increases sympathetic activity and the HR increases.
Peripheral vasoconstriction increases TPR which helps restore blood pressure.
Define and describe postural hypotension
Postural hypotension is a condition where a person’s blood pressure drops abnormally when they stand up form lying down/sitting.
It occurs use to the fair of the baroreceptor reflex and is defined by a decrease in systolic blood pressure of > 15 mmHg
