BIOL 141 notes 9
Popular in Physiology
verified elite notetaker
Popular in Science
verified elite notetaker
This 4 page Class Notes was uploaded by Camryn McCabe on Friday February 26, 2016. The Class Notes belongs to Biol 141 at a university taught by Janelle Malcos in Spring 2016. Since its upload, it has received 22 views.
Reviews for BIOL 141 notes 9
Report this Material
What is Karma?
Karma is the currency of StudySoup.
You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!
Date Created: 02/26/16
Lecture 9 notes Volume and pressure • For a fixed volume of fluid, pressure depends on the volume of the space it occupies – Large space = lower pressure – Small space = high pressure – As the size of the space changes, so does the pressure – Apply this concept to heart chambers Pressure gradient: difference in pressures between 2 regions (P – P ) 1 2 Fluid flows from high pressure to low pressure o Pressure at first point will decrease; pressure at second point will increase o This holds true as long as the path is not blocked Volume and pressure Volume of chambers change during a heartbeat Also pay attention to pressure in vessels Relaxation Diastole o Space of chamber increases , volume of fluid remains constant pressure decreases Contraction Systole o Space of chamber decreases, volume of fluid remains constant pressure increases Cardiac Cycle = complete contraction and relaxation Phase 1: Quiescent Period (before threshold, no action potential) o Atria and Ventricles are in diastole Pressure of blood vessels > pressure in heart No pressure in ventricles, therefore AV valves are open and semilunar valves are closed Blood fills atria and flows through the AV valves to ventricles o Heart fills with blood from bottom up (through atria to ventricles) Some blood is leftover from previous contraction Ventricles contain about 90mL of blood (at this point) NOT the maximum capacity of ventricle o SA node cells are depolarizing (but not to threshold yet) o Pressure in arteries in veins > pressure in chambers o Chambers are all relaxed, high volume Phase 2: Atrial Systole Lecture 9 notes o SA node depolarizes to threshold (action potential across atria) o Atria contract (systole) Pressure in atria > pressure in ventricles o Blood is forced into ventricles About 40mL more blood 90mL + 40mL = 130mL total This is the End Diastolic Volume (ventricles) Phase 3: Isovolumetric contraction o Atria repolarize and relax (diastole) Start to refill from veins o Ventricles depolarize and begin to contract (early systole) Contract from bottom up Blood forces AV valves closed This makes first heart sound o Pressure in ventricles increases o Blood does not leave ventricles yet Pressure in aorta and pulmonary artery > pressure in ventricles Isovolumetric contraction: no change in volume of blood, but ventricles start to contract Phase 4: Ventricular Ejection o Ventricles fully contract (full systole) o Pressure in ventricles > pressure in vessels Forces pulmonary and aortic valves open Semilunar valves are open; AV valves are shut Blood leaves ventricles Only 70mL leaves (stroke volume) o Stroke volume: amount that leaves after one stroke (contraction) 60 mL left behind (End Systolic Volume) o End Systolic volume: volume left when completely contracted o Atria are still in diastole Continue to fill with blood Phase 5: Isovolumetric Relaxation o Ventricles repolarize and relax (diastole) o Pressure decreases in ventricle Pressure in pulmonary artery and aorta > pressure in ventricle Blood tries to flow back, but valves shut and prevent this This makes the second heart sound Lecture 9 notes o Both sets of valves are still closed so volume of blood in ventricles doesn’t change Isovolumetric relaxation o When atria are filled, AV valves are forced open cycle brings again with quiescent period End Diastolic Volume – End Systolic Volume = Stroke Volume About 130 mL - About 60 mL = About 70 mL Cardiac Output (CO) o CO- the amount of blood pumped by the left ventricle in one minute (measures how efficiently our heart pumps blood) o Heart rate (beats/minute) X stroke volume (mL/beat) – HR X SV = CO o On average, total blood volume is pumped through the heart per minute o This is resting cardiac output What affects heart rate? o Average heart rate = about 75 beats/minute o Autonomic nervous system modulates SA node activity Without nervous system control, heart would beat about 100 beats/minute (SA node depolarization rate due to leak channels) Visceral motor responses are initiated from interneurons in “brain centers” o Center- collection of interneurons that receive sensory input about a specific function and create motor output to alter that function o “Cardiovascular control center” (CVCC): Cardiac control (heart) Cardioacceleratory neurons Cardioinhibitory neurons Vasomotor control (vessels) o Together they regulate blood pressure and heart function Why out body needs to alter heart rate? o Energy balance o O d2mand o Waste removal (CO ) 2 o Regulate blood pressure Organ function Lecture 9 notes Interneurons of the cardioacceleratory center will lead to an increased heart rate o Efferent neurons excited by this center are visceral motor neurons of the sympathetic system o Postganglionic neuron secretes norephinephrine (NE) Adrenergic receptors on cells of the SA node bind NE Cause an increase rate of action potentials of SA node o Maximum heart rate = 230 beats/minute Limit of SA node excitation Interneurons of the cardioinhibitory center will lead to an increased heart rate o Visceral motor neurons of the parasympathetic system o Postganglionic neuron secretes Ach Cholinergic receptors on cells of the SA node bind Ach Allow potassium to leave the cell hyperpolarizing reaction Rate of action potentials decrease o Normal heart rate = 70 beats/minute Without nervous control the heart would beat about 100 beats/minutes Sensory input is integrated to create motor output to SA node o Proprioceptors, baroreceptors, chemoreceptors are all integrated together o Proprioceptors (sensory input from muscles and tendons) Informs brain on changes in physical activity o Baroreceptors (sensory input from blood vessels) Informs brain on changes to pressure in vessels o Chemoreceptors (sensory input from blood vessels) Informs brain on changes in CO or2O lev2ls in the blood (change in chemicals) Important in respiratory system, but has some effect on heart rate)
Are you sure you want to buy this material for
You're already Subscribed!
Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'