Heart control DR. HANA OMER

CONTROL OF CARDIAC OUTPUT The control of cardiac output is essential for adjustments of the blood pressure and blood flow requirements under different physiological and pathological states . Example : 1. muscular exercise increases the oxygen demand 2. in cases of fever, there is dilatation of the vascular bed with consequent lowering of arterial blood pressure .

Regulation of the heart rate It is by neural or humoral mechanisms . The neural mechanisms depend on autonomic innervation, and the humoral mechanisms depend on baro and chemoreceptors .

The Autonomic Nervous System and the Heart Autonomic nervous system controls involuntary actions Works with the voluntary nervous system to allow body functions to proceed smoothly

The Autonomic Nervous System and the Heart Autonomic nervous system conductors: Sympathetic nervous system Speeds up the heart Parasympathetic nervous system Regulates the rate .

The Autonomic Nervous System and the Heart Parasympathetic nervous system it slow the heart rate . Sends messages through vagus nerve, which can be stimulated by: Pressure on carotid sinus Straining against a closed glottis (Valsalva maneuver)

The Autonomic Nervous System and the Heart Parasympathetic nervous system (cont’d) If brain senses the heart should slow its pace: Electrical impulse travels to the SA node Causes release of acetylcholine (ACh) Signals node to slow heart .

The Autonomic Nervous System and the Heart

The Autonomic Nervous System and the Heart Sympathetic nervous system Adapts to changing demands Increases heart rate Strengthens cardiac muscle contraction force increase CO

The Autonomic Nervous System and the Heart Sympathetic nervous system (cont’d) In response to need for more oxygen: Brain sends message through nerves to heart Commands conveyed through release of norepinephrine and Epinephrine Heart speeds up to prevent lactic acid buildup .

Drugs that Act on the Sympathetic Nervous System Classified by the receptors with which they interact (alpha and beta receptors)

Drugs that Act on the Sympathetic Nervous System

Drugs that Act on the Sympathetic Nervous System Sympathomimetic drugs imitate actions of naturally occurring sympathetic chemicals Isoproterenol: pure beta agent

Drugs that Act on the Sympathetic Nervous System Phenylephrine: pure alpha agent Other drugs have varying degrees of alpha and beta activity.

Drugs that Act on the Sympathetic Nervous System Beta-sympathetic agents classified as: Beta-1 adrenergic agonists: work on cardiac beta receptors Beta-2 adrenergic agonists: work on pulmonary beta receptors

Drugs that Act on the Sympathetic Nervous System Sympatholytic blockers work by beating agents to receptor sites.

Drugs that Act on the Sympathetic Nervous System Beta adrenergic blockers occupy beta receptors.

Drugs that Act on the Sympathetic Nervous System Major autonomic agents: Atropine: Parasympathetic blocker Used to speed the heart Norepinephrine: Sympathetic agent Used to increase blood pressure Isoproterenol: Sympathetic agent Used to increase CO and dilate bronchi

Drugs that Act on the Sympathetic Nervous System Major autonomic agents (cont’d): Epinephrine: Sympathetic agent Used for peripheral vasoconstrictor effect Dopamine: Sympathetic agent Used to increase renal perfusion, increase rate and force of myocardial contraction, and constrict peripheral blood vessels

Drugs that Act on the Sympathetic Nervous System Major autonomic agents (cont’d): Albuterol: Sympathetic beta-2 agent Used to induce bronchodilation. Propranolol: Sympathetic beta blocker Used to slow the heart rate, decrease chronic angina pain, and to depress irritability in the heart