Biology 2313 Week 7 Notes
Biology 2313 Week 7 Notes Biology 2313
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This 7 page Class Notes was uploaded by Ednjon Parilla on Saturday October 8, 2016. The Class Notes belongs to Biology 2313 at University of Texas at El Paso taught by Dr. Zaineb Al-Dahwi in Fall 2016. Since its upload, it has received 20 views. For similar materials see Human Anatomy & Physiology II in Science at University of Texas at El Paso.
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Date Created: 10/08/16
Chapter 18: The Heart – Cardiac Output (Continued) Under normal conditions: pressure in ventricle is higher than blood in the aorta In afterload (hypertension): pressure in aorta is higher than blood in aorta o Provides a hard time for the ventricle to push open valve flaps 1) ESV; SV = Cardiac Output Factors Influencing Heart Rate Chronotrope: chemicals that have an effect on heart rate o Positive Chronotropic Agents = SV o Negative Chronotropic Agents = SV o Autonomic Nervous System 1) Sympathetic NS Stress response, fight of flight = Positive Chronotopes Activation of Sympathetic NS NT (neurotransmitter): Norepinephrine binds to beta- 1 receptors on SA Node o Influences pacemaker potential o Makes the SA Node fire faster; HR (heart rate) + 2+ Increases Na and causes Ca influx o Fiber innervating the myocardium in contractile cardiac muscle cells o Contractility; ESV = SV Important to Note: SV does NOT decline as it would if only HR; contractility serve as a compensating factor! Releases NT Epinephrine from the Adrenal Medulla in the Adrenal Gland o HR o Thyroxine Enhances both Norepinephrine and Epinephrine Direct effect on the heart (controls the HR) 2) Parasympathetic NS Rest & Digest = Negative Chronotopes Occurs during the inhibition of the Sympathetic NS Activated after the activation of the Sympathetic NS NT: Acetycholine o Effect on SA Node Opens K channels (hyperpolarizing SA Node) = K efflux Takes longer to reach threshold; SLOWS HR/beating of the SA Node o No Effect on cardiac muscle cells PNS does NOT innervate the myocardium Under Resting Condition Vagal Tone: predominate effect of PNS Heart receives impulses from Sympathetic and Parasympathetic NS PNS effect through the Vagal Nerve is more dominate o Beats: 72 – 80 bpm (at rest) If vagal nerve is cut; the heart will speed up to natural bpm in SA Node (100 bpm) Exercise has tri-effect o Effects the EDV, ESV, and Heart Rate 1) Activity of smooth muscle cells; speeds up Venus Return back to the heart; EDV, SV = Cardiac Output 2) Heart Rate; speeds up Venus Return; EDV, SV = Cardiac Output 3) Activates Sympathetic; Contractibility; ESV, SV = Cardiac Output Key: Important Terms Positive Chronotopes Negative Chronotopes Neurotransmitter Hormone Chapter 19: The Cardiovascular System – Blood Vessels Anatomical Features of Blood Vessels Most important factor in maintaining blood pressure is the Blood Vessel! Order of blood flow Heart = Pump o Arterial System = pumps blood AWAY from the heart 1) Elastic Arteries (includes aorta) = conducting vessels 2) Muscular Arteries = distributing vessels 3) Large Arterioles = resistance vessels 4) Small Arterioles = resistance vessels 5) Capillaries = Exchange Vessels o Venous System = pumps blood TOWARD the heart 6) Small Veins = capacitance vessels 7) Large Veins = pumps blood back to the heart Structure of Blood Vessels in General: 3 Layers (tunica) i. Tunica Intima Innermost, in contact with the blood Lumen of blood vessels Made of endothelium (single layer of simple squamous epithelial cells) Sub-endothelial Layer Only in blood vessels larger than 1 __ Made of basal membrane and loose ______ tissue ii. Tunica Media Middle layer Made of circular arranged smooth muscle cells (ability to contract) Contraction = Vassal Constriction Smaller diameter of blood vessel (lumen) Relaxation = Vassal Dilation Also made of elastic fibers (External Elastic Lamina) iii. Tunica Externa Made of bundles of collagen fibers Specific Anatomy of Blood Vessels 1) Elastic Arteries o Contains all 3 tunicas Tunica Media = HUGE amount of elastic fibers (usually called Pressure Reservoirs) Sandwiched between circular arranged bundles of smooth muscle cells o Aorta is capable of stretching when filled and recoiling into original shape when relaxed. (DOES NOT SHRINK) This feature sustains pressure in circulation o Acts as conducting tubes = called Conducting Vessels 2) Muscular Arteries o Distributes blood to individual organs = called Distributing Arteries o Muscle located in Tunica Media Thickest in all other layers = HUGE amount of smooth muscle cells Elastic Lamina: sheets of elastic fibers that sandwich Tunica Media both on the internal and external sides 3) Large Arterioles o Contain all 3 tunics o Similar to arteries’ structure but extremely thin compared to them 4) Smaller Arterioles o Leads blood to capillaries or bypasses ________ o Major Feature = Tunica Media Surrounded by a single layer of smooth muscle cells in circular arrangement? NO TUNICA EXTERNA o Sympathetic NS controls the diameter by secretion of hormones Once the diameter is changed = change in resistance = change in blood flow = change in blood pressure 5) Capillaries o Called exchange vessels; they exchange respiratory gases o Made of a single layer only = Tunica Intima Consists of endothelium, no sub-endothelium (only present in larger diameters) Extremely small diameters Surrounded by basement membrane Work in a network = Capillary Beds Lateral contact by mostly desmosomes and some tight junctions o Tight Junctions are incomplete; leave gaps in between epithelial cells Gaps are called Intercellular Clefts, which allow the passage of water-soluble substances o 3 Types of Capillaries: i. Continuous Capillary Least permeable capillary Basement membrane Completed Pericyte: located on top of continuous capillary Stabilizes the continuous capillary Located: skin, muscles, central nervous system Continuous Capillary in CNS in Brain Blood Brain Barrier o DO NOT have intercellular clefts o Contain COMPLETE tight junctions ii. Fenestrated Capillary Increased permeability (compared to continuous cap.) Intercellular clefts are discontinuous Basement membrane Completed No pericyte Fenestrations: holes present in epithelial cells Help in the exchange of material Needed in areas of high filtration rates o Located in the kidneys Needed in areas of high absorption rates o Located in the digestive system Needed in areas of high secretion o Located in endocrine glands iii. Sinusoidal Capillary Most permeable Large size of lumen Large intercellular cleft Fenestrations (pores) are much larger o Associated with organs: Liver Bone Marrow Platelets are made through megakaryocyte pushing through the fenestrations Spleen Storage of lymphocytes by their cytoplasmic extensions fitting into the fenestrations Basement membrane Incomplete o Overall Features of Capillary Beds Terminal Arteriole Vascular Shunt (made of meta-arteriole) Leads to next part of vascular shunt o Thoroughfare Channel Blood vessel that leads blood into Post-Capillary Venule Capillary Bed: Anatomical of Vascular Shunt + True Capillaries Microcirculation: Physiology blood flow from the Terminal Arteriole to Post-Capillary Venule o True Capillaries Arise from metarteriole (also called terminal arteriole) Most lead to Thoroughfare Channel Pre-capillary Sphincters Made of smooth muscle cells surrounding the root of each true capillary at the metarteriole Forming a part where it can contract in which blood is prevented from entering true capillaries Controlling blood flow into capillaries o Can either go through the true capillaries or the shunt Starts at Terminal Arteriole Post-Capillary Venule (ships true capillary) o Sends to where it’s needed If exercising blood is sent to skeletal muscles 6) Post-Capillary Venule (venule = small vein from capillaries) o Endothelium, surrounded by parasites (not all, only some) that stabilizes the venule o Extremely permeable and porous o Where WBCs leave circulation and adhere to this venule at the endothelial cells and leave through intracellular clefts 7) Larger Venules o Larger lumen than post-capillary venule o Has a wall containing all layers of capillaries Tunica Intima = unchanged Tunica Media = extremely thin, 2-3 layers of circular muscle cells No elastic fibers! Tunica Externa = extremely thin 8) Veins o All three tunics Tunica Initma = the same in all! Tunica Media = thin, no elastic fiber Tunica Externa = bulkiest layer, made of huge collage fiber bundles o Called Capacity Vessels/ Blood Reservoir 65% of blood is held here If punctured blood doesn’t spurt like punctured arteries Veins have a lower blood pressure Veins return blood BACK to the heart Adaptations help return blood at the same rate as pumped o Structural Adaptations Large Diameter ↳ Lower resistance = increased blood flow Lumen ↳ Venus Valves – folds from Tunica Intima ▫ Most abundant in lower limbs (opposed by gravity) Blood Pressure Driving force for blood flow; down the gradient Blood Pressure refers to the systemic arterial blood pressure BP in elastic arteries close to the heart during ventricular contraction and relaxation o Arterioles Allow drastic drop in blood pressure Where the blood faces the greatest resistance o Aorta (elastic artery) Peak level of blood pressure inside aorta (takes place in VT contraction) Blood pushed into aorta from heart Lowest level of BP is here during VT relaxation Called Diastolic Pressure Aorta recoiled after blood has been pushed out of the aorta Pressure is still higher than the rest of circulation Which pushes the blood out because blood flow happens with difference in blood pressure! Pulse = difference between systolic and diastolic pressure 1 Mean Arterial Pressure = Diastolic Pressure + Pulse Pressure 3