Physio Ex free essay sample

The maximum threshold will not change in cardiac muscle cells (as with any other cells), which is determined by the X amount of voltage needed for calcium channels to open. After this point, no additional voltage can cause the channels to open more, or again, prior to depolarization. 3. Why is it only possible to induce an extrasystole during relaxation. a. 3. cardiac is able to depolarize only after repolarization 4. explain why wave summation and tetanus are not possible in the cardiac muscle tissue. a. Cardiac cells have long action potentials and long twitches, therefore do not show temporal summation. Act 2 1. Explain the effect that extreme vagus nerve stimulation had on the heart. a. The vagus nerve stimulation caused the heart to flat line restart and react normally. The response after the stimulation that resumed the heart is called the vagal escape. 2. The SA node of the heart is located in the right arterial wall 3. We will write a custom essay sample on Physio Ex or any similar topic specifically for you Do Not WasteYour Time HIRE WRITER Only 13.90 / page Describe how the sympathetic and parasympathetic nervous systems work together to regulate the heart rate. a. The sympathetic and parasympathetic are two branches of the autonomic nervous system. Both supply nerve impulses to the heart. The sympathetic (fight or flight), becomes more active when needed. Stimulation will increase the heart rate and force of contractions. The parasympathetic (resting and digesting) this branch is more active. Stimulation decreases the heart rate without directly changing force of contraction 4. What do you think would happen to the heart rate if the vagus nerve were surgically cut? a. The heart rate would increase but the heart would be damaged. The vagus nerve carries important information to the heart from the parasympathetic nervous system. This information is the decrease of heart rate, contraction strength, and the rate of the electrical impulses conducted in the heart. The sympathetic does the opposite and raise heart rate, contraction force and electrical conduction. Both of these systems work together. Act 3 1. Explain the effect that decreasing the temperature had on the frog heart. How do you think the human heart would respond? a. The colder temperature the heart rate is slower. A frog has no internal homeostatic regulating mechanism. The temperature will change depending on external environment. Because the human has an internal temperature of 35. 8-38. 2 degrees C even when the external environment changes. A cooler temperature for a humans heart rate would decrease and possibly be hypothermic in extreme external temperature conditions. 2. Describe why Ringers solution is required to maintain heart contractions? There are electrolytes of calcium, chloride, sodium, potassium, and magnesium. This is meant to keep the isolated intact heart workable. 3. Explain the effect that increasing the temperature had on the frog heart rate. How do you think the human heart would respond? The hotter he temperature for the frog the heart rate would increase. The human heart rate would increase and maybe not be able to maintain its homeostasis and possibly become hyperthermic, in extreme external temperature conditions. A frogs internal body temperature changes depending on external environment and has no internal homeostatic mechanisms to regulate temperature. Act 4 1. Atropine is an †Å"acetylcholine antagonist. † Does atropine inhibit or enhance the effects of acetylcholine? a. Describe your results and how they correlate with how the drug works. Yes. The heart rate increased from 44 to 69. The modifier worked in the opposite to the neurotransmitter, so this would be an antagonist. 2. Describe the benefits of administering digitalis? a. Digitals are used to bolster a weak heart in congestive heart failure. People with a bad heart need to have maximum time for the venous return and increased stroke volume would benefit from increased force of contraction and decreased heart rate. 3. Distinguish between cholinergic and adrenergic chemical modifiers. Include examples of each in your discussion. a. Cholingeric and adrenergic modifiers inhibit, mimic, or enhance the action of acetylcholine in the body. Pilocarpine is a direct acting cholinergic agonist that decreases the heart rate by directly acting on the receptor the same as acetylcholine. Atropine is a cholingeric antagonist that blocks the acetylcholine receptor increasing the heart rate. Epinephrine is an adrenergic agonist and binds to adrenergic receptor like B1, B2, and Alpha1 and increases heart rate. This mimics effect of the sympathetic nervous system. Act 5 1. Describe the effect that increasing the potassium had on the heart in this activity. How did this change the resting membrane potential of the cardiac muscle cell? a. Excessive potassium decreases the resting otential of the plasma membrane and decreases the force of contraction. The ectopic pacemakers can be caused by leakage of potassium into cardiac cells. The pacemakers then show in abnormal locations of the heart muscle. This decreases the force of contraction with a negative inotropic. In the experiment the heart was decreased to 28 and then erratic. 2. Des cribe how medicines called â€Å"calcium channel blockers† are used to treat patients and why? a. They are used to treat high blood pressure and abnormal heart rates. This blocks movement of calcium through channels and throughout phases of cardiac action potentials.