Chapter 18 - Blood Vessel & Chapter 19 - The Heart

Explain the events of the cardiac cycle, and relate the heart sounds to specific events.

"Lubb" first heart sound (s1) - lasts a bit longer than the second. Marks the start of the ventricular contraction and is the AV valves closing. "Dupp" (s2) when the semilunar valve closes. s3 - blood flowing into the ventricles s4 - atrial contraction

Discuss the movements of fluids between interstitial spaces.

.

afferent vs efferent

Afferent neurons are sensory neurons that carry nerve impulses from sensory stimuli towards the central nervous system and brain, while efferent neurons are motor neurons that carry neural impulses away from the central nervous systme and towards muscles to cause movement.

branches of the carotid arteries & where it serves

Ascends deep into the tissues of the neck to supply the face, neck and brain. Can be felt along the sides of the windpipe. Internal: Enters the skulls through the carotid canal of the temporal bones delivering blood to the brain and eyes. External: Branches to supple the neck, esophagus, pharynx, larynx, lower jaw, cranium and face. Carotid Sinus: Base of the internal carotid artery: Extend along a portion of the common carotid. Contain baroreceptors involved in the control of blood pressure. Vertebral Artery: arises from the subclavian artery and ascends within the transverse foramina of the cervial vertebrae. Left and Right vertebral arteries entre the cranium at the foramen magnum where they fuse aling the ventral surface of the medulla oblongata to form the basilar artery. Common carotid: Divides into external carotid artery and internal carotid artery.

Explain how the cardiovascular system responds to the demands of exercise.

Athletes have bigger hearts and larger stroke volume. The larger the stroke volume the slower the heart rate - as low as 32 bpm and can increase to levels 50% higher than those of non athletes. 1. Vasodialation occurs, peripheal resistance drops and blood flow through capillaries increased. 2. Venous return increases. Each inhalation creates a negative pressure in the thoracic cavity that pulls blood into the venae cavae from their branches = RESPIRATORY PUMP. 3. Cardiac output increases.

Describe the factors that determine blood flow.

Blood flow is determined by the interplay between aterial pressure and peripheral resistance. directly proportional to blood pressure and inversely proportional to peripheral resistance (increased resistance results in decreased blood flow). Aorta @ 120 mm Hg ---> capillaries @ 35 mm Hg ---> venules @ 18 mm Hg. as BP decreases it moves more slowly. Blood flow is the highest at the aorta. Blood flow is the slowest in the capillaries. Arterial pressure rises during ventricular systole and falls during ventricular diastole. The peak blood pressure measured during ventricular systole is called systolic pressure, and the minimum blood pressure at the end of ventricular diastole is called diastolic pressure.

Describe the factors affecting the heart rate.

Bradycardia - (SLOW) - less than 60 bpm. Acetylcholine released by parasympathetic neurons open chemically gated k+ channels in the plasma membrane, slowing the rate of spontaneous depolarization - declining heart rate. Tachycardia - (FAST) - 100+ bpm. Norephinephrine (NE) released by sympathetic neurons binds to beta-1 receptors, leading to opening of ion channels that increase the rate of depolarization and shorten the period of repolarization threshold more quickly - increasing the heart rate. Age, general health and physical conditioning can affect the persons normal heart rate. Cardioinhibitory center - controls parasympathetic neurons that slow the heart rate. Cardioacceleratory center - controls the sympathetic neurons that increase the heart rate.

heart's external anatomy

Can be easily viewed in the superficial view of the anterior surface. - 2 Atria are thin muscle walls and are highly expandable. When not filled with blood they deflate and become lumpy, wrinkled flap. - Sulci (Shallow grooves) mark the boundaries between the atria and ventricles, and between the left and right ventricles. - Connective tissue of the epicardium contain substantial fat, esp. along sulci. Fat must be stripped away to view the sulci. - Sulci contain arteries and veins that carry blood to/from cardiac muscle. ---------------- ANTERIOR ---------------------- - Auricle (looks like an ear) expandable pouch Right atrium - Coronary Sulcus - deep groove. Border between the atria and the ventricle. - Ligamentum arteriosum - attaches the pulmonary trunk to the aortic arch. fibrous remnant for the fetal connection between the aorta and the pulmonary trunk. - Anterior Interventricular sulcus - shallow depression on the anterior surface that marks the boundary between the left and right ventricle. ------------------ POSTERIOR --------------------- - Coronary sinus: carries the blood collected from the myocardium by numerous coronary veins and brings blood to the right atrium. - posterior ventricular sulcus: shallow depression on the posterior surface that marks the boundary bwtween the L and R ventricle.

Discuss the movement of fluids between capillaries

Capillary exchange - filtration, diffusion and osmosis. Capillary hydrostatic pressure (CHP) - is the blood pressure within the capillary beds, and it provides the driving force for filtration. CHP pushes the water and soluble molecules out of the bloodstream and into the intersistial fluid. Filtration - is the size-selective process. Only small solutes can cross the endothelium. Larger molecules such as plasma proteins remain in the bloodstream. Diffusion - net movement of ions and molecules from an area of higher concentration to and area of lower concentration. Occurs faster when distances are smalled, the concentration gradient is larger, and the iols or molecules involved are smaller. Occurs continuously across capillary walls.

Explain the complete round of cardiac systole and diastole.

Cardiac cycle is the period between the start of one heartbeat and the beginning of the next. During systole (contraction) the chamber contracts and pushed blood into the adjacent chamber or into the arterial trunk. Diastole (relaxation) Chamber fills with blood and prepares for the next contraction.

branches of the superior vena cava & where it serves

Drains the veins of the --- Neck: External jugular (superficial of the head and neck), Vertebral (drains the cervical spinal cord and the posterior surface of the skull) and the Internal jugular (drains deep structure of the head and neck). Right subclavian vein: Veins of the arm (Brachial vein, axillary vein and the basilic vein Veins of the arm: Brachial vein and the basilic merge to the axillary. The Cephalic vein extends along the lateral side of the arm. Forearm: Median cubital interconnects with the cephalic and basilic. Ulnar vein and the radial vein drain the deep palmar arch and then cross the elbow where they fuse to create the brachial vein. The cephalic vein with the median antebrachial and the basilic drain the superficial palmar arch. Digital: empty into the superficial and deep veins of the hand, which are connected to the palmar venous arch.

branches of the internal jugular veins & where it serves

Exists the skulls through the jugular foramen and delivers blood to the brachiocephalic vein on that side. Drains blood from the venous sinuses within the cranium. Meets with the external to form the brachiocephalic.

vasculogenesis

Formation of the first level by precursor endothelial cells called hemangioblasts.

branches of the external jugular veins & where it serves

Formed by the maxillary and temporal veins. Combines with the internal jugular to form the brachiophalic vein. Branches of the external jugular vein receives blood from veins draining from the cranium, face, lower jaw and neck on that side. Temporal, Maxillary, Facial and Occipital.

Describe the structures and functions of cardiac muscle

Forms both the atria and the ventricles. Its the middle layer and contains cardiac musslce tissue, blood vessels, and nerves. - Small ell size - Single centrally located nucleus - branching interconnections between cells - specialized intercellular connections - contained organized myofibrils and the presence of many aligned sarcomeres makes it look striated. - almost solely dependent on anerobic metabolism. - sacroplasm of cardiac cells contain many mitochondria and abundant reserves of myoglobin that store oxygen. - richly supplied with capillaries because they need a lot of oxygen to work properly. "Intercalated discs" bound together by GAP junctions and DESMOSOMES. Help stabilize the positions of the adjacent cells. Gap junctions allow ions and small molecules to move fast from one cell to another, which creates a direct electrical connection between two muscle cells. Action potential can move across intercalated disc. Myofibirls are interlocking muscle cells and are firmly anchored to the membrane at the intercalated disc and can "pull together" with maximum efficiency. Cardiac muscle called functional syncytium (fused mass of cells).

venous branches of the hepatic portal system & where it serves

Fusion of the superior mesenteric and inferior mesenteric and splenic veins. (largest volume of blood and most nutrients) flow through the superior mesenteric vein. Superior mesenteric: pancreaticoduodenal, middle colic, right colic, ileocolic and intestinal (small) Splenic vein: Left gastric (stomach), Right gastroepiploic (stomach) and pancreatic. Inferior Mesenteric: Left colic (descending colon), Sigmoid (sigmoid colon), superior rectal (rectum).

angiogenesis

Growth of new blood vessels from pre-existing vessels. Occurs with the migration of endothelial calls to form vascular networks.

vertebral arteries & where it serves

Inside the cranium, they supply blood to the spinal cord, medulla oblongata, pons and cerebellum before dividing into the posterior cerebral arteries which then branch off into the posterior communicating arteries.

branches of the descending aorta & where it serves

Intercostal Arteries: supply the chest muscles and the vertebral column areas. Superior Phrenic Arteries: Blood to the superior surface of the diaphragm. Inferior phrenic, adrenal, renal, gonadal, lumbar, common iliac., celiac trunk, (Branches of the celiac trunk: left gastric, splenic, common hepatic), Superior mesenteric, abdominal aorta and inferrior mesenteric. Visceral branches of the thoracic aorta: Supply to organs of the chest: Bronchial arteries - tissues of the lungs not involved in gas exchange. Esophageal arteries- supply the esophagus. Mediastinal arteries - supply the tissues of the mediastinum. Pericardial arteries - supply the pericardium

Explain central regulation

Involves both neural and endocrine mechanisms.

Explain autoregulation

Involves changes in the pattern of blood flow within the capillary beds as precapillary sphincters open and close in response to chemical changes in the interstitial fluid. Vasodilators - promote the dilation of blood vessels. Lactate accelerate blood flow through their tissue or origin.

Describe the structure of the pericardium and explain its functions

Is serous membrane that lines the pericardial cavity and covers the heart. Three layers: Epicardium, myocardium and endocardium. The parietal pericardium is the portion of the serious membrane that lines the outer wall of the pericardial cavity. It helps to form the pericardial sac. Epicardium - also known as visceral pericardium, covers the outer surface of the heart. Consists of exposed mesothelium and underlying layers of areolar tissue that is attached to the myocardium. Myocardium - muscular wall of the heart: forms both the atria and ventricles. Middle layer contains cardiac muscle tissue, blood vessels, and nerves. Concentrated layers of cardiac muscle tissue. Endocardium - Inner surface of the heart, including those of the heart valves. Simple Squamous epithelium and underlying areolar tissue. The endothelium of the heart is continous with the endothelium of the attached great vessels.

Explain the hormonal regulation of blood pressure and blood volume

LOW: - Epinephrine and Norepinephrine are released from the adrenal medullae. This stimulates cardiac output and peripheal vasoconstriction. - ADH - Angiotensin II - EPO - Aldosterone HIGH: - Cardiac cells, when stretched too much, released Natriuretic peptides. (Sodium & urination). ANP is produced by the cardiac muscle cells in the wall of the right atrium. - BNP (Brain netriuretic peptide): Produced by the ventricular muscle cells. As blood volume decreases, the stresses on the walls of the heart are removed, and natriuretic peptide production stops.

location and general features of the heart.

Located in the mediastinum, and enclosed by the pericardial cavity. General features: Great vessels - the largest veins and arteries in the body (top) Pericardial Sac - surrounds the heart. dense network of collagen fibers. Attaches to the central tendon of the diaphragm and sternum (bottom) and stabilizes the position of the heart.

branches of the venae cavae & where it serves

Located: large blue right and left veins from the top of the heart, down through the thoracic cavity into the abdomen. Lumbar veins: Drain the lumbar portion of the abdomen including the spinal cord and the muscles of the body wall. Gonadal: (Ovarian and testicular) drain from the ovaries and the testes. Right gonadal vein empties into the inferior vena cava, and the left into the left renal vein. Hepatic vein: drains the sinusoids of the liver. Renal veins: largest branches of the inferior vena cava, collect blood from the kidneys. Adrenal veins: drain adrenal gland. Right drains into the inferior vena cava and the left into the left renal vein. Phrenic: Drains the diaphragm. Right phrenic drains into the inferior vena cava, and the left drains into the left renal vein.

major arteries of pulmonary circuit

Oxygen-depleted blood from the body leaves the systemic circulation when it enters the right atrium through the superior and inferior venae cavae. The blood is then pumped through the tricuspid valve into the right ventricle. From the right ventricle, blood is pumped through the pulmonary valve and into the pulmonary artery. The pulmonary artery splits into the right and left pulmonary arteries and travel to each lung.

major veins of the systemic circuit

Oxygenated blood enters the left atrium from the pulmonary veins. The blood is then pumped through the mitral valve into the left ventricle. From the left ventricle, blood is pumped through the aortic valve and into the aorta, the body's largest artery. The aorta arches and branches into major arteries to the upper body before passing through the diaphragm, where it branches further into the illiac, renal, and suprarenal arteries which supply the lower parts of the body.

branches of the common iliac arteries & where it serves

Pelvis and Lower Limbs. Anterior: Femoral artery, deep femoral artery, femoral circumference artery, popliteal artey, posterior and anterior tibial artery. Psoterior: Right external iliac, Deep femoral, Femoral circumference, popliteal, anterior and posterior tibial. Fibular artery or peroneal artery. Foot: Doralis pedis, dorsal arch and plantar arch.

describe the changes in blood flow patterns that occur at birth.

Prior to birth, the lungs are collapsed and most blood bypasses the pulmonary circuit. The infant takes their first breath, which inflates the lungs and expands the pulmonary blood vessels. Blood rushes into the pulmonary vessels and the resulting pressure changes at the heart closing the foramen ovale and forming the fossa ovalis.

Describe the relationship between the AV and semilunar valves during a heartbeat.

RV (semilunar) and LV (thick and circular). RV acts like a bellow, pushing blood against the thick wall of the LV. Moves the blood efficiently with minimal effort and with LOW PRESSURE. LV contracts the diameter decreses drastically, the distance between the base (top) and the apex (bottom) like squeezing and rolling toothpaste. When the heartbeats the AV valve closes before the semilunar valve opens - and the semilunar valve closes before the AV valves open. If they did not do this they would get backflow of blood called regurgitation.

Describe an action potential in cardiac muscle, and explain the role of calcium ions.

Rapid depolarization - threshold voltage-gated sodium channels open, membrane suddenly becomes permiable to na+ (calcium). This causes a huge influx of sodium ions and the rapid depolorization of the sarcolemma. The channels involved are calls fast sodium channels, because they open quickly and remain open for only a few milliseconds. Plateau - membrane potential remains nears 0mV. When the membrane potential nears +30 MC the voltage gate sodium channels close and the cell begins to actively pumping the calcium out. As the sodium channels are closing the voltage-gated calcium channels are opening. These channels are called slow calcium channels. They open slowly and remain open for a long period of time. Repolarization - after 175 msec, slow calcium channels begin closing, and slow potassium channels begin opening. As the channels open, potassium ions (K+) rush out of the cell, and the net result is a period of rapid re-polarization that restores resting potential.

differences between fetal and adult circulation patterns

Related to exchange of oxygen between the fetal and maternal blood supply via the placenta umbilical cord - venous duct Temporary structural changges that allow fetal circulation to bypass the lungs Oval opening arterial duct

Describe the role of chemoreceptor reflexes in adjusting cardiovascular activity.

Respond to changes in carbon dioxide, oxygen or PH levels in the blood and cerebrospinal fluid (CSF) Sensory neurons located in the carotid bodies, situated in the neck near the carotid sinus, in the aortic bodies near the aortic arch and on the ventrolateral surfaces of the medulla oblongata. Stimulation of these triggers coordinated adjustments in cardiovascular and respiratory activity.

cardiac chambers

Right Atrium Right Ventricle Left Atrium Left Ventricle

Identify the major blood vessels, chambers, and heart valves.

Right Atrium - receives blood from the superior and inferior venae cavae and cardiac veins from the coronary sinus. Fossa Ovalis - ovel depression. Remnant of the foramen ovale, which closes at birth. Pectinate Msucle - prominent muscular ridges in the anterior atrial wall and inner surface of the auricle. ----------------------------------------------------- Right Ventricle - Received blood from the right atrium through the AV valve/Tricuspid. Cusps - three flaps on each valve. Attached to the fiber tissue chordae tendineae Papillary muscle - fibers of the tendineae originate at the conical muscular projections Pulmonary valve - Superior portion of the RV tapers towards the pulondary semilunar valve. Blood leaves the RV to the pulmonary trunk. Moderator band - prvents slamming of the AV cusps. ----------------------------------------------------- Left atrium - recieves blood from the pulmonary trunk. Left ventricle - Much larger than the right ventricle which allows it to build up enough force to push blood through the systemic system. Left atrioventricular valve - AV valve or bicuspid. permits blood flow through the left atrium into the left ventricle but prevents backflow. Contains a pair (2 valves). Also known as the Mitral valve or bishops hat. Trabeculae Carneae - series of musuclar riges on the inner surface of the R and L ventricle. Aortic valve - blood leave the LV by passing through this and travels into the ascending aorta.

Trace blood flow through the heart

Right Atrium, Right Ventricle, Pulmonary Trunk, Lungs, Pulmonary Veins, Left Atrium, Left ventricle, Aortic Arch Body.

major vessels supplying the heart, and cite their locations.

Right Coronary Artery - Follows the coronary sulcus around the heart. Supplies blood to the Right Atrium, portions of both ventricles and parts of the conduction systems of the heart (control heartbeat) - marginal arteries - from R coronary artery supply to the surface of the R ventricle Left Coronary Artery - supplies blood to the left ventricle, left atrium and interventricular septum - circumflex artery: between the L coronary artery and the large anterior. Large Anterior interventricular (left anterior descending) runs along the surface within the anterior interventricular sulcus. - Arterial anastomoses between the anterior and posterior interventricular arteries maintains a fairly stable blood flow despite pressure fluctuations in the L and R coronary arteries. - Circumflex artery: Branch of the left coronary artery that curves to the left around the coronary sulcus, eventually meeting and fusing with small branches of the R coronary artery. Marginal artery branches off from the circumflex to supply the posterior surface of the left ventricle. - Posterior Interventricular artery: supplied by the R coronary artery, runs toward the apex (tip) within the posterior interventricular sulcus. Supplies blood to the interventricular septum and adjacent portions of the ventricles. - Anterior cardiac veins: drain the anterior surface of the R ventricle, empty directly into the R atrium. - Great Cardiac Vein: begins anterior surface on the ventricles, along the IV Sulcus. Drains blood from the region supplied by the anterior IV artery. Reaches the level of the atria and curves around the L side of the heart within the coronary sulcus to empty into the coronary sulcus. - Coronary Sinus: expanded vein that opens into the R strium near the base of the inferior vena cava. - Posterior cardiac vein: drains the area supplied by the circumflex artery. - Small cardiac vein: receives blood from the posterior surface of the right atrium and ventricle. Empties into the coronary sinus along with the middle cardiac vein. - Middle cardiac veins: drains area supplied by the posterior interventricular artery. Empties into coronary sinus.

branches of the internal carotid & where it serves

Supplies the arteries of the anterior half of the cerebrum. Ascends to the level of the optic nerve, where it divides into three branches: Ophthalmic, anterior cerebral and middle cerebral. Internal carotid and basilar arteries are interconnected in a ring-shaped anastomisis called the Cerebral Arterial Circle. Ophthalmic: supplies the eyes Anterior Cerebral: frontal and parietal lobes. Middle: supplies the midbrain and the lateral surfaces of the cerebral hemisphere. Cerebral Arterial Circle: Circle of willis, encricles the infundibulum of the pituitary gland. Reduces the likelihood of serious interruption of blood flow because it can receive blood from either the carotid of the vertebral arteries.

major arteries of the systemic circuit

The deoxygenated blood continues through the capillaries which merge into venules, then veins, and finally the venae cavae, which drain into the right atrium of the heart. From the right atrium, the blood will travel through the pulmonary circulation to be oxygenated before returning gain to the system circulation, completing the cycle of circulation through the body

Describe the heart's location, shape, and borders

The heart is located near the anterior chest wall, directly posterior to the sternum. The center lies slightly to the left of baseline, and the entire heart is rotated to the left so that the right atrium and right ventricle dominate an anterior view. Borders: Base forms the superior border. Right border is formed by the right atrium Left border is formed by the left ventricle and a small portion of the left atrium. Left border extends to the APEX (pointed tip) where it meets the inferior. Inferior border is formed mainly by the inferior wall of the right ventricle. Adult heart measures 12.5 CM (5 IN)

major veins of the pulmonary circuit

The oxygenated blood then leaves the lungs through pulmonary veins, which returns it to the left atrium, completing the pulmonary circuit. As the pulmonary circuit ends, the systemic circuit begins.

Describe the factors that influence total peripheral resistance.

The resistance of the entire cardiovascular system. Depends on three factors: Vascular resistance, viscosity and turbulence. Vascular Resistance: Opposition to blood flow in the vessels. Largest component of total peripheal resistance. Results from friction between blood and the vessel walls. The amount of friction depends on the vessel length and the vessel diameter. The longer the vessel the greater the resistance. Layers of fuid moving at different speeds - layer of the blood closest to the vessel wall is slowed by friction, and the blood in the middle moves faster. Differences in diameter have more significant effects on resistance than in length. A small changes in vessel diameter creates a large change in vessel resistance. Viscosity - the thicker the material is, the more pressure it needs to flow at the same speed as a thinner substance. Whole blood has viscosity 5 times that of water, due to the plasma proteins and blood cells. Disorders that disrupt the hemacrit or plasma composition also change the blood viscosity, thus peripheral resistance. Turbulence - High flow rates, irregular surfaces and sudden changes in vessel diameter upset the smooth flow of blood, creating eddies and swirls. This is called turbulence. It increases the resistance and slows blood flow. Plaque in an artery can disrupt blood flow and create turbulence.

Define arteriosclerosis, and explain its significance to health.

Thickening and toughening of the arterial walls. Account for roughly 50% of all deaths in the US. The effects are varied: Arteriosclerosis of the coronary vessl is responsible for coronary artery disease (CAD), and arteriosclerosis of arteries supplying the brain can lead to stroke.

branches of the aortic arch & where it serves

Three elastic arteries originate along the aortic arch and deliver blood to the head, neck, shoulders and upper limbs. Brachiocepahlic: First branch - ascends for a short distance and branches to form the right subclavian artery and the right common carotid artery. Left Common - Second: arises from the aortic arch, supplies the left side of the head and neck. Left subclavian - Third: arises from the aortic arch have the same distribution pattern as the right subclavian. Right Subclavian - (Internal thoracic: supplies the pericardium and anterior wall of the chest) (vertebral artery: blood to the brain and spinal cord)

visceral arterial vessels & where it serves

Three unpaired branches: Celiac Trunk, Superior mesenteric artery and the inferior mesenteric artery. Celiac trunk: divides into the hepatic artery, Left gastric artery and splenic artery. Common hepatic - liver, stomach, gallbladder and duodenum. Left Gastric - stomach. Splenic Artery - spleen with branches into the stomach and pancreas. Superior Mesenteric: supplies the pancreas & duodenum, small intestines and large intestines. Inferior pancreaticoduodenal. Right colic, ileocolic, middle colic and intestinal arteries. Inferior Mesenteric: terminal portions of the colon and rectum. Left colic, sigmoid and rectal.

Describe the variables that influence stroke volume.

Varies with the movement of the pump (right and left ventricles) - Contractillity is influenced by hormones (epinephrine, thyroid hormones, and glucagon all increase contractillity). - Drugs used in clinical practice are used to lower contractillity (beta-blockers, such as propranolol or timolol and calcium channel blockers such as nifedipine or verapamil)

Elastic rebound

When the left ventricle contracts it forces blood into the aorta. New blood sarrival at elevated pressure stretches the elastic walls of the aorta. When the left ventricle relaxes, pressure decreases and the aorta recoils.

Explain how stroke volume and cardiac output are coordinated.

With exercise • EDV increases • Myocardium stretches more • Stroke volume increases

Systemic Circuit

carries blood away from your heart, delivers it to most of your organs and tissues, and returns it to your heart again.

Pulmonary Circuit

carries deoxygenated blood away from the heart, to the lungs, and returns oxygenated (oxygen-rich) blood back to the heart.

veins

carry blood from the capillaries back toward the heart.

arteries

carry the blood away from the heart

capillaries

enable the actual exchange of water and chemicals between the blood and the tissues

identify the layers of the heart wall

endothellium / areolar tissue / myocardium & connective tissue / areolar tissue / mesothelium --- pericadial cavity --- mesothelium / areloar tissue / dense fibrous layer

branches of the common iliac veins & where it serves

received blood from lower limbs, the pelvis and the lower abdomen. Common iliac, external iliac, internal iliac, gluteal, internal pedendal, lateral sacral, obturator, femoral, femoral circumflex, deep femoral, femoral, great saphenous, popliteal, small saphenous, anterior tibial, posterior tibial, fibular. Foot: plantar venous, anterior tibular, posterior tibular, fibular (peroneal) veins, dorsal venous arch, great saphenous and small sapheous vein (digitals)

Explain baroreceptor reflexes in response to changes in blood pressure and blood composition.

responds to changes in blood pressure. Receptors are located: - in the walls of the carotid sinuses, expanded chambers near the bases of the internal carotid arteries of the neck - The aortic sinuses, pockets in the walls of the ascending aorta adjacent tot he heart. - Right atrium. ------------------------------------------ Response to INCREASED BARORECEPTOR stimulation: Decrease in cardiac output due to parasympathetic stimulation and inhibition of sympathetic activity Widespread periphearl vasodialation, due to inhibition of vasometer center. Response to DECREASED BARORECPTOR stimulation: Increase in cardiac output. Widespread peripheal vasoconstriction caused by stimulation of vasomotor center. In crisis: major blood loss - sympathetic activation occurs: both norepinephrine and epinephrine enter the bloodstream. Immediate increase in cardiac output and generalized vascular constriction = elevates blood pressure.

afferent arterioles

supply the nephrons in many excretory systems. They play an important role in the regulation of blood pressure as a part of the tubuloglomerular feedback mechanism. The afferent arterioles branch from the renal artery, which supplies blood to the kidneys.

Describe the components and functions of the conducting system of the heart.

the network of specialized cardiac muscle cells that initiate and distribute the stimulus to contract. - each heartbeat begins with action potential generated at the sinotrail node (SA node). - SA node in embedded in the posterior wall of the right atrium, near the entrance of the vena cava. The impulse by this "pacmaker" is than distributed by other cells. - In atria conducting cells are found in the internodal pathways, which distribute the contractile stimulus to atrial muscle cells as the impulse travels toward ventricle. - Atrioventricle Node (AV Node) is in the junction between the atria and the ventricles. Also contains pacemaker cells, that do not ordinarily affect the heart rate. If any other pathway is damaged the AV node can generate heartbeats of 40-60 bpm. - Purkinje fiber - large diameter conducting cell that propagates action potential (multiply) rapidly. Final link in the distribution network and are responsible for the depolarization of the ventricular myocardinal cells that trigger ventricular systole. - AV bundle: located withing the interventricular septum. AV bundle normally the only electrical connection between the atria and the ventricles. - Bundle branches: AV leads to the right and left bundle branches. Left bundle branch (supplies the left ventricle, is larger than the right). Both branches extend toward the apex, turn and fan out deep to the endocardial surface. ** SA Node (0 sec) --> AV Node (50 msecs) --> AV Bundle & Bundle branches (150 msec) --> Moderator band (175 msec) --> Purkinje fiber (225 msec).

efferent arterioles

urinary tract of organisms. The efferent arterioles form from a convergence of the capillaries of the glomerulus. They play an important role in maintaining the glomerular filtration rate despite fluctuations in blood pressure.