BI0005 - Lecture 21 - Heart Disease and Hypertension

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james14hunter
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BI0005 - Lecture 21 - Heart Disease and Hypertension
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2014-05-08 11:17:09
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BI0005 Lecture 21 Heart Disease Hypertension
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BI0005 - Lecture 21 - Heart Disease and Hypertension
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  1. What is vascular tone?
    • The smooth muscle of all vessels has a degree of resting tension.
    •    - This is called vascular tone and affects vessel diameter

    Small changes in vascular tone greatly affect vascular resistance and blood pressure.
  2. What factors affect vascular tone?
    • Intrinsic control (local control):
    •    – factors: stretch, temperature, locally released chemical factors

    • Extrinsic control:
    •    – factors: Autonomic Nervous System and circulating hormones
  3. Extrinsic control include:
    Nervous control of blood vessels

    Hormonal control of blood vessels
  4. How does blood pressure increase through hormones?
    Adrenaline, acts on β- adrenergic receptors – contracting cardiac muscle.

    • NorAdrenaline, acts on α- adrenergic receptors – contracts vascular smooth muscle
    • Angiotensin- contracts vascular smooth muscle

    Aldosterone- promotes renal Na+reabsorption – this increases plasma volume

    Antidiuretic hormone- promotes renal water reabsorption – this increases plasma volume
  5. How does blood pressure decrease hormonally?
    Adrenaline, acts on β- adrenergic receptors – relaxes vascular smooth muscle
  6. How is blood pressure controlled?
    Carotid Sinus - monitors blood pressure

    • Medulla - Receives & Integrates information on blood pressure
    •     – Sends excitatory output to heart and vasculature
    •        • NorAdrenaline is released onto heart and vasculature
  7. What is hypertension?
    'High blood pressure'

    • • Characterized by an arterial blood pressure persistently higher than normal:
    •     • Eg 140/90 mmHg

    • As diastolic pressureis chief determinant of mean BP, diastolic pressureis an important indicator of hypertension
  8. What is primary hypertension?
    • Primary: 80% patients, causes unclear, carotid sinus-medulla control sensitivity appears reduced

    • • borderline - diastolic 90- 95mmHg
    • • mild - diastolic 95-100mmHg6
    • • Moderate - diastolic 100-114mmHg
    • • severe - diastolic 114<< mmHg
  9. What is secondary hypertension?
    Secondary: 20% patients, resulting from, e.g. pregnancy, endocrine disorders, renal disease, vascular disorders
  10. Why do you want to control hypertension?
    – does not impair well-being

    • – but does lead to vascular damage& secondary complications:
    •     • atherosclerosis: of coronary vessels, cerebral vessels, renal vessels
  11. What would the "ideal" anti-hypertensive drug be?
    • – effective as a single agent
    • – lowers blood pressure
    • – have no long
    • - term toxicity
    • – taken once a day
    • – moderate cost

    • - No such agent currently exists!
  12. What drugs can be used in controlling hypertension?
    • • Diuretics
    •  - reduce blood volume (deplete Na+)

    • • β-adrenoceptor antagonists
    •    – decrease myocardial contractility

    • • Vasodilators
    •    – decrease vasoconstrictor tone

    • • Centrally acting drugs
    •    – decrease sympathetic outflow
  13. What do diuretics do?
    Thiazides - bendofluazide

    • • act on renal distal tubule
    • • leads to loss of Na+ and H2O

    • • Adverse effects
    •    • weakness
    •    • impotence
    •    • hypokalemia
    •    • hyper-uricaemia
  14. What do β-adrenoceptor antagonists do?
    initially: cause fall in BP by decreasing cardiac output

    followed by: return of cardiac output to normal whilst retaining lowered BP and lowered vascular resistance

    • • Adverse effects
    •    •cold hands
    •    • provocation of asthma
  15. What do vasodilators do?
    • reduce vasoconstrictor effects & sympathetic tone
  16. What do centrally acting drugs do?
    • activates inhibitory receptors in the medulla,

    • • Adverse effects
    • •drowsiness
    • • autoantibodies against erythrocytes

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