Beta Agonist/Norepinephrine

 

These drug classes activate the sympathetic system. The cell bodies from the pre ganglionic neurons are located in the spinal cord and release Ach onto the post ganglionic neurons in the sympathetic ganglia in order norepinephrine onto the SA node (view electrical systems of the heart.) The activation of the SA node by the binding of norepinephrine to the b adrenergic receptors causes the arteries smooth muscle to constrict (recall resistance equation, where a decrease in the radius causes a significant increase in resistance.) Once the artery smooth muscle constricts, calcium ions flow into the cardiac cells, which then allows the threshold potential to be reached quicker and increases the rate of firing of the pacemaker current. The end result is an increase in heart rate and contractility due to the constricted vessels lowered threshold potential. Other effects of sympathetic drugs include increase in total peripheral resistance and mean arterial pressure from the constriction of the vessel.

 

This process is seen in the ‘fight or flight’ mechanism, where the sympathetic reaction allows a reduction in blood flow to the parallel organs in order to increase flow the heart. This process works because of the shift in energy requirements causing the blood to ‘split’ through paths to the organs more in need. This process also causes ghrelin to be secreted from the stomach in preparation for glucose production as well as, renin from the kidneys as the baroreceptors sense decrease in blood volume due to high contraction preventing blood to fill. 

 

Beta Blockers

 

These drugs work in the same way as the previous drug class as they affect the sympathetic chain as well, however they have the opposite effects. Beta-blockers are competitive drugs, meaning they compete with norepinephrine to bind with the adrenergic receptors in order to decrease contraction and decrease heart rate. These drugs are usually given to patients with hypertension because of their high blood pressure from the high force or blood against their vessels. These drugs help reduce the blood pressure by increasing the radius of the vessels to decrease the resistance and then decrease heart rate and contractility.

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Atropine

 

Drugs that affect the parasympathetic system cause heart failure. The cell body of the pre ganglion neuron sits in the brainstem and extends to the peripheral nervous system to release Ach onto nicotine Ach receptors on the post ganglion neurons. The Ach from the post ganglion neurons will release Ach onto muscarinic Ach receptors on the SA node (see electrical systems of the heart.) The activation of the SA node will cause an outflow of potassium making the cell more negative/hyperpolarized and therefore a reduction in pacemaker current. Atropine in a muscarinic Ach receptor antagonist, meaning it counters the effect of heart failing by competing with Ach to bind at SA node. This is used for patients with bradycardia (see electrical systems of the heart) by increasing heart rate due to the block of hyperpolarization. 

 

Marijuana

 

Aside from neurological and respiratory deficits, marijuana affects the cardiovascular system due the main chemical ingredient, THC. The THC found in marijuana is a smooth muscle relaxant, meaning it increases the radius of the artery wall and reduces the resistance in order to allow an increase of flow to tissues. The increase in flow from the low resistance causes a significant drop in blood pressure in the arteries due to the less contractile force of blood against the vessel walls.

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Sodium

 

Although sodium is a mineral that is essential for life, there are some drastic risks associated with its overconsumption and excessive use. When there is too much sodium in our bloodstream, water gets pulled into our blood vessels to dilute the sodium that’s present, which subsequently increases the volume of blood that is then inside of the vessels; with an increase in the amount of blood flow in the vessels, you can expect an increase in the blood pressure of the human. This increased pressure is dangerous to the body because over time the vessels may overstretch, get injured and also build up plaque on its walls that can block future blood flow. Aside from causing problems related to high blood pressure, taking in high quantities of sodium can also lead to heart failure, heart disease and stroke.

 

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