week 9.docx

+-----------------------------------+-----------------------------------+ | Learning Outcomes | | | | | | 1.List the basic components of | | | th...

+-----------------------------------+-----------------------------------+ | Learning Outcomes | | | | | | 1.List the basic components of | | | the cardiovascular system. | | | | | | 2.Describe the structures of the | | | heart and how they serve to pump | | | blood. | | | | | | 3.Discuss the deflection waves of | | | a normal ECG and explain their | | | significance. | | | | | | 4.Outline the basic steps of the | | | cardiac cycle. | | | | | | 5.Discuss the primary principle | | | of circulation and the | | | significance of high arterial | | | blood pressure. | | | | | | 6.Describe factors that affect | | | stroke volume and heart rate. | | | | | | 7.Discuss the significance of | | | peripheral resistance in the | | | cardiovascular system. | | | | | | 8.Discuss the significance of the | | | vasomotor control mechanism. | | | | | | 9.Discuss how the respiratory | | | pump and skeletal muscle pump | | | work to assist the venous return | | | of blood to the heart. | | | | | | 10\. Outline the hormonal | | | mechanisms that regulate blood | | | volume. | | | | | | 11\. Discuss the significance of | | | the pulse mechanism. | | | | | | 12\. List several major pulse | | | points in the body. | | +===================================+===================================+ | Function of heart and blood | - The cardiovascular system | | vessels | (circulatory system) consists | | | of: | | | | | | - The heart- a muscular | | | pumping device | | | | | | - Blood is pumped by | | | the heart around a | | | circuit of vessel as | | | it passes multiple | | | times through various | | | parts of the body | | | | | | - Closed system of vessels: | | | | | | - Arteries-carries | | | blood AWAY from the | | | heart. | | | | | | | | | | | | - Capillaries- conduct | | | blood through tissues | | | and permit Exchange | | | of materials | | | | | | | | | | | | - Veins- conduct blood | | | back TOWARD the | | | heart. | | | | | | - Homeostatic maintenance of | | | our body is due to continuous | | | and controlled movement of | | | blood. | | | | | | - Many controls mechanism help | | | regulate and integrate each | | | function and components of | | | the cardiovascular system | +-----------------------------------+-----------------------------------+ | Hemodynamics | - **Hemodynamics-** a | | | collection of mechanism that | | | influence the active and | | | changing circulation of | | | blood. | | | | | | - Circulation is a vital | | | function and the only means | | | that cells can receive | | | material needed for survival | | | and have their waste removed. | | | | | | - Circulation of different | | | volumes of blood per minute | | | at different time for organs | | | is needed. | | | | | | - Ex. more active cells | | | need more blood per | | | minute than less active | | | cell. | | | | | | - Blood circulates to | | | continually bring in more | | | oxygen and nutrients to | | | replace what is consumed. | | | | | | - Required control mechanisms | | | to accomplish 2 things: | | | | | | - Maintain circulation and | | | keep blood flowing | | | | | | - Vary the volume and its | | | distribution of the blood | | | circulated. | | | | | | - As structures increase its | | | activity, an increased blood | | | volume of blood must be | | | distributed | | | | | | - Means blood is shifted from | | | less active tissues to more | | | active tissues. | +-----------------------------------+-----------------------------------+ | Overview of the heart | - The heart is a four chambered | | | muscular organ | | Pericardium and its layers | | | | - Lie in the mediastinum region | | 3 layers that make up the heart | of the thorax | | wall | | | | - The apex of the heart lies on | | Chambers of the heart | the diaphragm pointing to the | | | left, while the base is the | | Valves of the heart. | wide portion of the heart | | | lying just below the second | | Pulmonary artery joins pulmonary | rib. | | valve (right ventricle)- think | | | lungs | - Between puberty-25 years old | | | the heart attains its adult | | Aorta joins aortic valve (left | shape and weight | | ventricle) | | | | - The heart has a special | | | covering called the | | | **pericardium**- a multilayer | | | sac that consists of **2 main | | | parts:** | | | | | | - **1. A fibrous portion** | | | -- made of tough white | | | fibrous connective tissue | | | that forms a loose, | | | inextensible outer | | | covering of the heart. | | | | | | - **2. Serous | | | pericardium-** lies | | | within pericardium. A | | | double layer of smooth, | | | moist serous membrane | | | | | | - **Parietal | | | pericardium-**adheres | | | to the inside of the | | | fibrous pericardium | | | | | | - **Pericardial | | | space-**space that | | | lies below perietal | | | and bove visceral. | | | Contain pericardial | | | fluid (10-15ml) | | | | | | - **Visceral | | | pericardium | | | (epicardium)-** a | | | layer that covers the | | | entire outer surface | | | of the heart | | | | | | - **3 distinct layers** of | | | tissues **make up the heart | | | wall** (same in both the | | | Atria and ventricles): | | | | | | - **Epicardium (Outer)** | | | | | | - Out layer of heart | | | wall | | | | | | - Is the visceral layer | | | of the serious | | | pericardium | | | (previously | | | described) | | | | | | - Same structure | | | with two | | | different names: | | | Epicardium and | | | serious | | | pericardium | | | \*\*\* | | | | | | - **Myocardium (middle)** | | | | | | - Middle layer | | | | | | - Bulk of the heart | | | wall, which is thick, | | | and contractile | | | | | | - Arranged cardiac | | | muscle cells | | | | | | - **Endocardium (inner)** | | | | | | - Delicate layer lining | | | the interior of the | | | myocardial wall. | | | | | | - Made of | | | **endothelium**-a | | | specialized type of | | | simple squamous | | | epithelium | | | | | | - **Lines** the | | | **heart** **and | | | all** of the | | | blood vessels. | | | | | | - Covers **beamlike | | | projection of | | | myocardial tissue** | | | called **trabeculae | | | carinae** (fleshy | | | beams) and add force | | | to the inward | | | contraction of the | | | heart wall. | | | | | | - Inward folds and | | | supporting connective | | | tissues make up the | | | flaps/cusps of the | | | major heart valves. | | | | | | - **Valves** ensure | | | the **one-way | | | flow** enabling | | | the heart to act | | | as a pump. | | | | | | - The interior of the heart is | | | **divided into four heart | | | chambers**: | | | | | | - **2 upper chambers called | | | the Atria (atrium | | | singular)** | | | | | | - Separated into left | | | and right chamber by | | | a septum (interatrial | | | septum) | | | | | | - Called **"receiving | | | chambers"** as they | | | receive blood from | | | veins | | | | | | - Veins pumps blood | | | toward the heart | | | from various | | | tissues. | | | | | | - **Atria alternately | | | relaxes and contracts | | | to receive blood,** | | | **then pushes it to | | | the lower chambers | | | (ventricles)** | | | | | | - **Does not generate | | | great pressure** to | | | move blood because it | | | doesn't travel far. | | | | | | - **Myocardial | | | wall** of each | | | **atrium is | | | thin** because of | | | this. | | | | | | - **2 lower chambers called | | | the Ventricles** | | | | | | - Separated into left | | | and right chamber by | | | a septum | | | (interventricular | | | septum) | | | | | | - Primary **"pumping | | | chambers"** of the | | | heart as the | | | **receive blood from | | | the atria** and | | | **pump** blood **out | | | of the heart into | | | arteries**. | | | | | | - **Force is needed** | | | to bump blood to a | | | further distance, so | | | the **myocardium | | | ventricle is | | | thicker** | | | | | | - **Myocardium of | | | left ventricle is | | | thicker than the | | | right** because | | | is pushes blood | | | through most | | | vessels of the | | | body. \*\*\* | | | | | | - **Right ventricle | | | only pushes blood | | | through** nearby | | | pulmonary vessels | | | that serve **the | | | gas exchange | | | tissues of the | | | lungs**. | | | | | | - The **heart valves** are | | | structure that **permit** the | | | **flow of blood in one | | | direction only**. | | | | | | - **4 valves** are used for | | | healthy function of the | | | heart: | | | | | | - **2 Atrioventricular | | | valves (AV)** | | | | | | - They guard the | | | opening between the | | | atria and ventricles | | | | | | - Have pointed flaps | | | called cusps (cuspid | | | valves) | | | | | | - **2 Semilunar valves | | | (SL)** | | | | | | - Located where the | | | trunk of the | | | **pulmonary artery | | | joins the right | | | ventricle** | | | (pulmonary valve) and | | | where the **aorta | | | joins the left | | | ventricle** (aortic | | | valve) | | | | | |  | | | | | | \(A) During atrial co | | | ntraction, | | | cardiac muscle in the | | | atrial | | | wall contracts, forci | | | ng blood | | | through the atriovent | | | ricular | | | (AV) valves and into | | | the | | | ventricles. | | | | | | \(B) During ventricul | | | ar | | | contraction that foll | | | ows, the | | | AV valves close and t | | | he blood | | | is forced out of the | | | ventricles | | | through the SL valves | | | and into | | | the arteries. | +-----------------------------------+-----------------------------------+ | The heart as a pump | - Covered functional anatomy of | | | heart, its 4 chambers and the | | | valves make up pumps: | | | | | | - The left pump (left side of | | | the heart) helps move blood | | | through the systematic | | | circulation. | | | | | | - Systematic circulation | | | includes blood flow to | | | and from all parts of the | | | body **except** the lungs | | | | | | - The right pump (right side of | | | the heart) helps move blood | | | through the pulmonary | | | circulation. | | | | | | - Cardiac muscle fibers | | | contract autorhythmially (on | | | their own) | | | | | | - Timing of action potentials | | | is coordinated across the | | | myocardium to pump | | | effectively. | | | | | | - Rate of cardiac muscle rhythm | | | can be sped up or down by | | | autonomic nerve signals. | | | | | | - The hearts conduction systems | | | generate pace setting | | | rhythmic impulses and | | | distributes them to different | | | region of the myocardium | | | along impulse conducting | | | pathways | | | | | | - 4 structures make the core of | | | the electrical condition | | | system of the heart: | | | | | | - **1. Sinoatrial (SA) | | | node** | | | | | | - Typical cardiac | | | impulse that | | | initiates mechanical | | | contraction of the | | | heart arises here. | | | | | | - Located beneath the | | | right atrial | | | epicardium at its | | | junction with the | | | superior vena cava. | | | | | | - Each impulse | | | generated here | | | travels swiftly | | | muscle fibers of both | | | atria. | | | | | | - An interatrial | | | bundle of | | | conduction fibers | | | facilitates rapid | | | conduction to the | | | left atrium | | | causing it to | | | contract, | | | | | | - Sends action | | | potential trough | | | the AV node | | | | | | - **2. Atrioventricular | | | (AV) node** | | | | | | - Action potential | | | enter here by using 3 | | | internodal bundles | | | and its conduction | | | begins to slow. | | | | | | - Slowing the | | | conduction allows for | | | complete contraction | | | of both atrial | | | chambers and for | | | ventricular filling | | | before the impulse | | | reaches the | | | ventricles. | | | | | | - After passing slowly | | | through AV node, it | | | makes its way to AV | | | bundles increasing | | | conduction velocity | | | | | | - **3.Atrioventricular (AV) | | | Bundle (bundle of His)** | | | | | | - The right and left | | | bundle branches and | | | the subendocardial | | | branches (Purkinje | | | Fibers) in which they | | | terminate conduct the | | | impulses throughout | | | the muscle of both | | | ventricles. | | | | | | - **4. Subendocardial | | | branches (Purkinje | | | fibers)** | | | | | | - **Included in process | | | above** | | | | | | - The AV node then | | | initiates a signal | | | that is conducted | | | through the | | | ventricular | | | myocardium by way of | | | the AV bundle (of | | | His) and | | | subendocardial | | | branches (Purkinje | | | fibers). | | | | | | - **Each heart conduction | | | system consists of cardiac | | | muscles that differ in | | | function from ordinary | | | cardiac muscle** | | | | | | - They are not contractile | | | and only permit rapid | | | conduction of an action | | | potential through the | | | heart. | | | | | | - **Pacemaker fibers-** fibers | | | that initiate signals | | | | | | - During the resting | | | membrane potential of a | | | pacemaker fiber, a | | | leakage of K+ ions out of | | | the cell, and an | | | increasing flow of Na+ | | | and Ca++ ions inward. | | | | | | - This depolarizes the | | | membrane, eventually | | | reaching the threshold | | | potential and triggering | | | an action potential. This | | | happens continuously it | | | produces an **intrinsics | | | rhythm** of action | | | potentials | | | | | | - **Conduction fibers-** | | | specifically adapted for | | | rapid conduction through the | | | syncytium. | | | | | | - They are high speed that | | | carry action potential | | | from pacemakers to more | | | distant area of the | | | syncytium. | +-----------------------------------+-----------------------------------+ | Electrocardiogram | - Impulse conduction generates | | | tiny electrical currents in | | S-T Segment is elevated can mean | the heart that spread through | | damage to the heart or ischemia | surrounding tissues to the | | | surface of the body. | | ECG Waves | | | | - The electrocardiogram (ECG | | P Wave | when written and EKG when | | | spoken)- record of the | | QRS Complex | electrical even that preceded | | | the contractions | | | | | | - Produced by attaching | | | electrodes of recording | | | voltmeter are attached to the | | | limbs and/or chest of the | | | patient. | | | | | | - Changes in voltage which | | | represent changes in the | | | hearts electrical activity | | | are observed as deflections | | | of a line drawn on paper or | | | traced on a video monitor. | | | | | | - Typical ECG deflection waves | | | and ECG intervals between | | | them briefly | | | | | | - Healthy ECG is composed of | | | deflection waves called the P | | | wave, QRS complex, and T wave | | | | | | - **P wave:** | | | | | | - Represents | | | **depolarization of | | | the atria**. | | | | | | - The deflection caused | | | by the passage of | | | electrical impulse | | | from the SA node | | | through the | | | musculature of both | | | atria. | | | | | | - **QRS complex** | | | | | | - Represents | | | **depolarization of | | | the ventricles | | | \*\*\*** | | | | | | - Repolarization of | | | atria, but is hidden | | | | | | - Combined duration of | | | all three deflections | | | of the QRS represents | | | the time required | | | (**0.07-0.11 | | | Second)** for | | | ventricle | | | depolarization. | | | | | | - Same time ventricles | | | are depolarizing, the | | | atria are | | | repolarizing. | | | | | | - **T wave** | | | | | | - Reflects | | | **repolarization of | | | the ventricles** | | | | | | - **Inverted T wave** | | | is often **seen after | | | myocardial muscle | | | damage** | | | | | | - Sometimes a U wave | | | can appear as a tiny | | | hump at the end of | | | the T wave. It | | | represents late | | | repolarization of | | | subendocardial | | | branches (Purkinje | | | fibers) in the | | | papillary muscle of | | | the ventricular | | | myocardium. | | | | | | - U waves can be a | | | sign of | | | **Hypokalemia** | | | (low blood | | | potassium) or too | | | much **Digoxin** | | | (a heart | | | medication) | | | | | | - **ECG Intervals-** provide | | | important information | | | concerning the rate of | | | conduction of an action | | | potential through the heart. | +-----------------------------------+-----------------------------------+ |  | | +-----------------------------------+-----------------------------------+ | Cardiac Cycle | - **Cardia cycle-** a single | | | heartbeat or a pumping cycle. | | Residual volume- a considerable | | | amount of blood left behind. | - Once cycle **consist of | | | contraction (systole) and | | In **heart failure** the residual | relaxation (diastole) of both | | volume remaining in the | atria and both ventricles** | | ventricles may greatly exceed | | | that ejected during systole | - The two atria contract | | | simultaneously then as they | | Diastasis-reduced ventricular | relax the two ventricles | | filling of the heart | contract and relax. | | | | | | - Gives the heart a pumping | | | action | | | | | | - The cardiac cycle illustrates | | | and integrates changes in | | | pressure gradients in the | | | left atrium, left ventricle, | | | and aorta | | | | | | - **The 5 steps of the cardiac | | | cycle:** | | | | | | - **1. Atrial systole** | | | | | | - Begins with the P | | | wave of the ECG | | | | | | - Electrical wave of | | | depolarization | | | followed by | | | contracting (systole) | | | myocardium of the | | | atria forces. | | | | | | - The contracting force | | | creates pressure | | | gradient that pushes | | | blood out of the | | | atria into the | | | relaxed ventricles. | | | | | | - Keep AV (cuspid) | | | valves open during | | | this phase. | | | | | | - SL valves remain | | | closed as the | | | arterial pressure is | | | higher than the | | | pressure in the relax | | | ventricles. | | | | | | - **2. Isovolumic | | | ventricular contraction** | | | | | | - The onset of | | | ventricular systole | | | coincides with the R | | | wave of the ECG and | | | the appearance of the | | | first heart sound | | | | | | - **Isovolumic-** | | | having same volume | | | | | | - Intraventricular | | | pressure begins to | | | increase **closing | | | the AV valves and | | | producing the first | | | heart sound.** | | | | | | - The pressure is still | | | not high enough to | | | open the SL Valves | | | (semilunar valve) | | | | | | - **3. Ejection** | | | | | | - SL valves are now | | | open, and blood is | | | ejected from the | | | heart when the in the | | | ventricles exceeds | | | that in the pulmonary | | | artery and aorta. | | | | | | - **Rapid ejection-** | | | characterized by a | | | marked increase in | | | ventricular and | | | aortic pressure. | | | | | | - **Reduced ejection-** | | | Coincides with the T | | | wave on the ECG | | | | | | - Residual volume | | | remains in the | | | ventricles at the end | | | f ejection period | | | | | | - In heart failure | | | the residual | | | volume remaining | | | in the ventricles | | | may greatly | | | exceed that | | | ejected during | | | systole. | | | | | | - **4. Isovolumic | | | Ventricular relaxation** | | | | | | - Period between | | | closure of the SL | | | valve and opening of | | | the AV Valve. | | | | | | - End of ventricular | | | ejection, the SL | | | valves close when the | | | ventricular pressure | | | drops. | | | | | | - As the **valves (SL) | | | snap shut**, they | | | **produce the second | | | heart sound.** | | | | | | - Closure prevents | | | blood from | | | re-entering the | | | ventricular | | | chambers from the | | | pulmonary trunk | | | and aorta. | | | | | | - Both | | | sets of valves | | | are closed and | | | there is no | | | change in volume. | | | | | | - **5. Passive Ventricular | | | filling** | | | | | | - As ventricles | | | continues to relax | | | the intraventricular | | | pressure continues to | | | drop. | | | | | | - Rising interatrial | | | pressure is produced | | | by return of venous | | | blood and forces open | | | the AV valves. | | | | | | - Blood rushes into the | | | relaxing ventricles | | | | | | - At the end of the | | | phase a new P wave | | | triggers he | | | contraction of the | | | atria that marks the | | | beginning of a new | | | cycle. | +-----------------------------------+-----------------------------------+ | Heart Sounds | - Heart makes typical sounds | | | during each cardiac cycle | | for blood to flow within the | | | circulatory system, there must be | - The **first sound "lubb"** is | | a gradient from high pressure to | caused by the | | low pressure, primary principle | contraction(systole) of the | | of circulation(hemodynamics) | ventricles and also by | | | **vibration of the vibrations | | Pressure difference drives the | of the AV Valve closing.** | | flow of blood | | | | - It is longer and lower | | | than second sound. | | | | | | - The **Second heart sound | | | "Dupp"** is short and sharp | | | caused by **the closing of | | | the SL valve as ventricles | | | relax (Diastole)** | | | | | | - Hearts sounds have clinical | | | significance because they | | | provide information about the | | | valves of the heart. | | | | | | - Any variation form normal in | | | the sounds indicates | | | imperfect functioning of the | | | valves. | | | | | | - Heart Murmur- common heard | | | atypical heart sound. | | | Produces a "swishing" sound | | | that may signify incomplete | | | closing of the valves or | | | stenosis(narrowing) of them | +-----------------------------------+-----------------------------------+ | Arterial blood Pressure | - Mary principle of | | | circulation, high pressure in | | | the arteries must be | | | maintained to keep blood | | | flowing through the | | | cardiovascular system. | | | | | | - Determinant of arterial blood | | | pressure is volume of blood | | | in the arteries. | | | | | | - Arterial blood pressure is | | | proportional to arterial | | | blood volume | | | | | | - Increase in arterial | | | blood volume increases | | | arterial pressure and | | | vice versa. | | | | | | - Factors that determine | | | arterial pressure: | | | | | | - Cardiac output (CO) | | | | | | - Affects the blood | | | entering the arteries | | | | | | - If cardiac input | | | increases, the amount | | | of blood entering | | | increases and tends | | | to increase the | | | volume in the | | | arteries | | | | | | - FINDS FORMULA | | | | | | - Peripheral resistance | | | | | | - Affects the blood | | | leaving the arteries | | | | | | - If peripheral | | | resistance increases, | | | it decreases the | | | amount of blood | | | leaving the arteries | | | which increases the | | | amount of blood left | | | in them. | | | | | | - Increase in either CO or | | | PR results in an increase | | | in arterial blood volume | | | which increases arterial | | | blood pressure. | +-----------------------------------+-----------------------------------+ | Factors that affect Stroke Volume | - Factors that affect the | | | strength of myocardial | | | contraction and the stroke | | | volume are mechanical, | | | neutral and chemical factors. | | | | | | - Starling Law of Heart | | | (mechanical) | | | | | | - Within limits, the longer | | | or more stretched the | | | heart fibers at the | | | beginning of contraction, | | | the stronger the | | | contraction. | | | | | | - Contractibility (strength of | | | contraction) can be | | | influenced by chemical | | | factors | | | | | | - Norepinephrine released | | | by sympathetic fibers in | | | the cardiac nerve and | | | epinephrine released by | | | into the blood by the | | | adrenal medulla can both | | | increase the strength of | | | contraction of the | | | myocardium. | | | | | | - Increase pushes more | | | blood out of the heart | | | per cardiac stroke thus | | | increasing stroke volume | | | | | | - Ejection fraction (EF)- can | | | be influence by neutral | | | factors | | | | | | - The ratio of stroke | | | volume (SV) to | | | end-diastolic volume | | | (EDV) | | | | | | - Usually expressed as a | | | percentage (Ef = (SV x | | | EDV) x 100 | | | | | | - Healthy adults have EF of | | | at least 55% | | | | | | - Ef goes down as the | | | myocardium fails | | | | | | - Afterload is also influences | | | by neutral factors | | | | | | - Harder is to push blood | | | out of the ventricles, | | | the lower stroke volume | | | will be | | | | | | - Unusually high afterload | | | from flow resistance in | | | arteries can cause heart | | | failure. | +-----------------------------------+-----------------------------------+ | Factors that affect heart rate | - sinoatrial (SA) node | | | initiates each heartbeat and | | | Chronotropic factors can and | | | do change the rate of the | | | heartbeat. | | | | | | - Factors that affect the heart | | | rate: | | | | | | - Autonomic control of | | | heart rate | | | | | | - The ratio of | | | sympathetic and | | | parasympathetic | | | impulses conducted to | | | the node per minute. | | | | | | - Cardiac pressoreflexes | | | | | | - Receptors sensitive | | | to changes in | | | pressure are located | | | in 2 places in the | | | heart: | | | | | | - Aortic baroreceptors | | | -- measuring pressure | | | in the aortic | | | pressure and adjust | | | based on its needs | | | | | | - Carotid | | | baroreceptors - | | | | | | - Carotid sinus reflex | | | | | | - Located at beginning | | | of the internal | | | carotid artery | | | | | | - Sensory fibers from | | | carotid sinus | | | baroreceptors run | | | through the carotid | | | sinus nerve and the | | | glossopharyngeal | | | nerve to the cardiac | | | control center. | | | | | | - Parasympathetic | | | impulses leave the | | | cardiac control | | | center travel through | | | the Vagus nerve to | | | each the SA node | | | | | | - Aortic reflex | | | | | | - Other reflexes- includes | | | emotions, exercise, | | | hormones, blood | | | temperature, pain, and | | | stimulation of various | | | exteroceptors also. | | | Influence heart | +-----------------------------------+-----------------------------------+ | Peripheral resistance | - The resistance to blood flow | | | imposed by the force of | | | friction between blood and | | | the walls of its vessel. | | | | | | - Friction develops because of | | | a characteristic of blood- | | | viscosity (thickness) | | | | | | - The resistance offered by | | | arterioles and accounts for | | | almost one half of the total | | | resistance in systemic | | | circulation. | | | | | | - Peripheral resistance in | | | arterioles determine arterial | | | blood pressure because the | | | more resistance there is in | | | the arterioles, the more | | | blood "backs up" in the | | | arteries to increase fluid | | | pressure | | | | | | - Blood viscosity stems from | | | proportion of red blood cells | | | (hematocrit) but also partly | | | from the protein molecules | | | present in blood. | | | | | | - Increase in blood protein | | | concentration or | | | hematocrit tends to | | | increase viscosity. | | | | | | - Under atypical conditions | | | like marked anemia or | | | hemorrhage, a decrease in | | | blood viscosity may be the | | | crucial factor lowering | | | peripheral resistance and | | | arterial pressure, even | | | circulatory failure. | | | | | | - Vasomotor mechanism- muscular | | | layer of the arterioles | | | constricting or dilating and | | | thus changing the amount of | | | resistance to blood flow. | | | | | | - Vasoconstriction- | | | Reducing the vessel | | | diameter by increasing | | | the contraction of the | | | muscular layer. | | | | | | - Vasodilation- Relaxation | | | of vascular muscles, | | | decreases resistance to | | | blood flow | +-----------------------------------+-----------------------------------+ | Vasomotor control mechanism | - Control center for this | | | complex system lies in the | | | vasomotor center of the | | | medulla | | | | | | - Upon stimulation, the control | | | system sends out impulses, | | | causing the restriction of | | | smooth muscles surrounding | | | some vessels | | | | | | - Sudden increase in arterial | | | blood pressure stimulates | | | aortic and carotid | | | baroreceptors; results in | | | arterioles and venules of the | | | blood reservoirs dilating | | | | | | - Decrease in arterial pressure | | | causes the aortic arc and | | | carotid sinus baroreceptors | | | to send more impulses to the | | | medulla's vasoconstrictor | | | centers; causes the vascular | | | smooth muscles to constrict | | | | | | - Vasomotor control mechanism | | | cont. | | | | | | - There are also chemoreceptor | | | reflexes in the aorta and | | | carotid arteries | | | | | | - Function when excess blood | | | carbon dioxide and low oxygen | | | content endanger the | | | stability of the internal | | | environment | | | | | | - Local control of arterioles | | | -- several kinds of local | | | mechanisms that produce | | | vasodilation in localized | | | areas | | | | | | - Function in times of | | | increased tissue activity | +-----------------------------------+-----------------------------------+ | Venus returns to the heart | - Venous return- amount of | | | blood that is returned to the | | | heart by way of the veins | | | | | | - Factors that influence venous | | | return include the reservoir | | | function of veins, which | | | occurs whenever blood | | | pressure drops and the | | | elasticity of the venous | | | walls adapts the diameter of | | | veins to the lower pressure, | | | thus maintaining blood flow. | | | | | | - Stress-relaxation effect: | | | change in blood pressure | | | causes a change in vessel | | | diameter. | | | | | | - Effect | | | of gravity: | | | | | | - Another factor that | | | influences venous return. | | | | | | - When a person is lying | | | flat, the pull of gravity | | | is equal above and below | | | the heart. | | | | | | - When a person stands | | | upright (orthostasis) the | | | pull of gravity combined | | | with the compliance (ease | | | of stretch) of the veins | | | causes a redistribution | | | of venous blood to the | | | lower limbs. | | | | | | - The orthostatic | | | effect can reduce | | | venous return to the | | | heart if not | | | counteracted by other | | | forces | | | | | | - Factors that can help | | | to overcome the | | | influence of gravity | | | is venous pumps that | | | maintain the pressure | | | gradient necessary to | | | keep blood moving | | | into the central | | | veins and from there | | | into the atria of the | | | heart. | | | | | | - Venous pumps | | | | | | - **Venous pumps--** | | | blood-pumping action of | | | respirations and skeletal | | | muscle contractions | | | facilitate venous return | | | by increasing pressure | | | gradient between | | | peripheral veins and vena | | | cavae | | | | | | - Change in pressure, | | | between expiration and | | | inspiration, helps move | | | blood along the venous | | | route back to the heart | | | | | | - As each skeletal muscle | | | contracts, it squeezes | | | the soft veins scattered | | | throughout its interior; | | | contractions push blood | | | upward toward the heart | | | | | | - Repeated contraction | | | of the muscles when | | | walking or doing any | | | other exercise keeps | | | the blood moving | | | forward in the veins | | | | | | - Total blood volume | | | | | | - changes in total blood | | | volume change the amount | | | of blood returned to the | | | heart | | | | | | - Balance between the | | | movement of water | | | into and out of the | | | plasma that affects | | | the homeostasis of | | | blood flow | | | | | | - Changes in total blood | | | volume | | | | | | - Receptors in the body | | | that detect the | | | balance between water | | | and solutes trigger | | | the ADH endocrine | | | reflex | | | | | | - ADH is released | | | by the posterior | | | pituitary and | | | acts on the | | | kidneys to reduce | | | the amount of | | | water loss | | | | | | - Renin-angiotensin-ald | | | osterone | | | system (RAAS) | | | | | | - Renin is released | | | when blood pressure | | | in the kidney is low | | | | | | - Release of rennin | | | triggers a series of | | | events that leads to | | | the secretion of | | | aldosterone from the | | | adrenal cortex | | | | | | - Aldosterone promotes | | |