Term
| What 3 bones make up the sternum? What joint is in the sternum? |
|
Definition
Manubrium
Mesosternum (body)
Xiphoid process
Xiphisternal joint |
|
|
Term
| What are the 3 skeletal components of the thoracic cage? |
|
Definition
Thoracic vertebrae and IVDs
Ribs and intercostal cartilages
Sternum |
|
|
Term
| Name the muscles in the thoracic cage |
|
Definition
|
|
Term
| What are the neurovascular components of the thoracic cage? |
|
Definition
| Intercostal nerves, arteries and veins |
|
|
Term
| What is the thoracic inlet? |
|
Definition
| where the thoracic cavity communicates with the neck |
|
|
Term
| What is the thoracic outlet? |
|
Definition
| where the thoracic cavity communicates with the abdomen |
|
|
Term
| What are the functions of the thoracic cavity? |
|
Definition
- protecting vital organs (including upper abdominal organs)
- chancging volume to facillitate movement of air into and out of lungs |
|
|
Term
| What is the diaphragm? What does it contain? |
|
Definition
- muscular partition between the abdominopelvic and thoracic cavity that closes off the thoracic outlet.
- contains arpetures that allow passage of structures (vessels, nerves, oesophagus) to and from abdomen
- innervated by the Phrenic nerve |
|
|
Term
| What are the 3 apertures in the diaphragm and what vertebrae do they correspond to? |
|
Definition
Caval opening T8/9
Oseophagus hiatus T10
Aortic opening T12 |
|
|
Term
| What are the external intercostal muscles, which direction do they go in and what effect do they have on the ribs? |
|
Definition
- complete sheet of muscles in the direction as if you were putting hands in pockets
- elevates ribs |
|
|
Term
| What are the internal intercostal muscles, which direction do they go in and what effect do they have on the ribs? |
|
Definition
- complete sheet of muscles in the direction as if you were putting hands in back pockets
- depresses ribs |
|
|
Term
| What are found between the internal and external intercostal muscles? |
|
Definition
Intercostal nerve
Intercostal artery
Intercostal vein |
|
|
Term
| How do the upper ribs change the volume of the thoracic cage? |
|
Definition
Increase diameter via a pump handle movement
superior and anterior movement of sternum |
|
|
Term
| How do the lower ribs change the volume of the thoracic cage? |
|
Definition
Increase transverse diameter via a bucket handle movement
Elevation of lateral shaft of rib. |
|
|
Term
| What are the subdivisions of the thoracic cavity? |
|
Definition
- Trachea divides into 2 primary bronchi
- 2 x pulmonary cavities (lined by a layer of parietal pleura)
- Midline region (mediastinum) |
|
|
Term
| What does the mediastinum enclose? |
|
Definition
| encloses heart, major vessels and nerves, trachea and osephagus) |
|
|
Term
| What is each lung surrounded by? |
|
Definition
2 membranous layers: parietal and visceral pleura (together they make the visceral sac)
between the two is the pleural cavity |
|
|
Term
| What does the pleural cavity contain and what is its function? |
|
Definition
a thin film of serous pleural fluid:
-reduced friction
-creates surface tension between the parietal and visceral layers to aid inspiration |
|
|
Term
| What causes a collapsed lung? |
|
Definition
| air in the pleural cavity |
|
|
Term
| Which pleura is in contact with the lung surface? |
|
Definition
|
|
Term
| How many lobes do each lung have? |
|
Definition
Right has 3:
- Superior, middle and inferior
Left has 2:
- superior and inferior |
|
|
Term
| What hangs off the superior left lobe? |
|
Definition
|
|
Term
| Describe the subdivisions of the mediastinum and where they are seperated |
|
Definition
horizontal plane passing through the sternal angle and the lower border of the 4th thoracic vertebra.
Split into superior and inferior mediastinum.
Inferior is further split into posterior, middle and anterior. |
|
|
Term
| Structures within the superior mediastinum include: |
|
Definition
Arch of the Aorta
Superior Vena Cava
Brachiocephalic Trunk
Left Subclavian Artery
Left Common Carotid Artery
Trachea
Oesophagus |
|
|
Term
| What is the heart enclosed in? |
|
Definition
| a pericardial sac which consists of 2 layers: Fibrous and Serous Pericardia |
|
|
Term
| What does the serous pericardium consist of? |
|
Definition
| 2 layers. The parietal and visceral layers are reflected at the base of the heart (great vessel roots) |
|
|
Term
| What is the role of the fibrous pericardium? |
|
Definition
| surrounds the serous pericardium, and serves a protective function |
|
|
Term
| What are the 3 layers of the hear? Inner to outer |
|
Definition
Endocardium
Myocardium
Epicardium |
|
|
Term
|
Definition
| continuous with the endothelium of the vessels |
|
|
Term
|
Definition
| composed of cardiac muscle |
|
|
Term
|
Definition
| consists of visceral serous pericardium |
|
|
Term
| What the valves in the heart? |
|
Definition
Aortic
Pulmonary
Tricuspid
Mitral |
|
|
Term
| Where does the Right atrium receive blood from? |
|
Definition
VENOUS blood
IVC
SVC
Coronary sinus |
|
|
Term
| Where does blood exits the right atrium to? |
|
Definition
| Right ventricle via the tricuspid valve |
|
|
Term
| Describe the internal structure of the right atrium? |
|
Definition
Posterior: smooth thin wall at which SVC, IVC and coronary sinus drain
Anterior: rough muscular wall composed of pectinate muscles
Atrioventricular orifice: deoxygenated blood flows to RV |
|
|
Term
| What divides the smooth and rough parts? |
|
Definition
| a ridge called the crista terminalis |
|
|
Term
| What is the fossa ovalis? |
|
Definition
| a depression between the atria |
|
|
Term
| Where does blood exit the right ventricle? |
|
Definition
| Blood exits to the Pulmonary Trunk via the Pulmonary Valve |
|
|
Term
| What are trabeculae carneae? |
|
Definition
| irregular muscular projections in the RV |
|
|
Term
| What does the RV narrow into superiorly? and what is it bordered by? |
|
Definition
| the conus arteriosus which leads to the pulmonary trunk. This is bordered by a muscular ridge: the supraventricular crest. |
|
|
Term
| Where does the LA receive blood from? |
|
Definition
| Receives OXYGENATED blood from the valve-less Pulmonary Veins |
|
|
Term
| Which atria has a thicker wall? |
|
Definition
|
|
Term
| Describe the internal structure of the left atrium? |
|
Definition
- large smooth wall and a muscular auricle containing pectinate muscles
- four pulmonary entering the smooth posterior wall
- atrioventricular orifice: oxygenated blood moved to the LV via mitral valve |
|
|
Term
| Where does the LV discharge blood to? |
|
Definition
| aorta via the aortic valve |
|
|
Term
| What are the LV walls covered by? |
|
Definition
| a network of delicate trabeculae carneae (finer and more numerous than found in the RV) |
|
|
Term
| What do pulmonary arteries do? |
|
Definition
| carry blood away from the heart. These are the only arteries in the body that carry DEOXYGENATED blood. |
|
|
Term
| What do pulmonary veins do? |
|
Definition
| carry blood towards the heart. These are the only veins in the body that carry OXYGENATED blood. |
|
|
Term
| Describe the thoracic aorta |
|
Definition
Descends through the thorax in the posterior mediastinum
Passes through diaphragm at T12 |
|
|
Term
| Where does the Cardiac AP originate from? |
|
Definition
SAN (right atrium)
The cells in the SAN exhibit autorhythmicity and are called pacemaker cells |
|
|
Term
| Describe a pacemaker cells resting membrane potential |
|
Definition
|
|
Term
| What happens to the membrane after an AP? |
|
Definition
| After an AP, the membrane immediately begins to depolarise until threshold is reached and another AP is triggered |
|
|
Term
| Describe the Electrical Activity in Pacemaker Cells of the Heart |
|
Definition
1. slow depolarisation until threshold is reached
2. rapid depolarisation (AP is reached)
3. repolarisation |
|
|
Term
| Describe the ions involved? |
|
Definition
1. Decreased K, Increased sodium and calcium (slow repolarisation)
2. Increased calcium (rapid deplarisation)
3. Decreased calcium and increased K (repolarisation) |
|
|
Term
| Describe the initiation and conduction of an impulse during a heartbeat |
|
Definition
1. From the SAN the AP spreads through the atrial tissue to the AVN via INTERNODAL TRACT
2. Impulse sperads into the ventricles via the AV bundle (bundle of his)
3. AV bundle divides into left and right branches (supplying ventricles)
5. impulses spread through the ventricles via the Purkinje fibres |
|
|
Term
| Which nodal cells transmit APs slower and how long is the delay? |
|
Definition
|
|
Term
| What are the electrical connections between cardiac muscle cells? |
|
Definition
Adjacent cells are coupled electrically- via gap junctions in the intercalated disk
This allows an action potential in one cell to spread rapidly to adjacent cells |
|
|
Term
| Describe phase 4 of Ventricular AP |
|
Definition
At rest (phase 4) K+ permeability is high- this falls during phase 0
When an action potential arrives from a neighbouring cell – membrane becomes more positive and Na+ channels open |
|
|
Term
| Describe phase 0 of ventricular AP |
|
Definition
| A rapid influx of Na+ ions underlies the depolarising (phase 0) |
|
|
Term
| Describe phase 1 of ventricular AP |
|
Definition
| The upstroke of the action potential is caused by an increase in the permeability of the cells to Na (P Na). These channels close rapidly (2-3 ms) which limits the extent of the depolarisation. Once depolarised (above -40 mV), this opens up L-type Ca channels in the cell membranes increasing the permeability to Ca ions. |
|
|
Term
| Describe phase 2 of ventricular AP |
|
Definition
| long plateau phase (2) of the ventricular action potential caused by influx of Ca2+ ions caused by opening of L-type calcium channels |
|
|
Term
| Describe phase 3 of ventricular AP |
|
Definition
| Repolarisation due to delcining Ca2+ influx and increased K+ permeability due to opening of delayed K+ channels and closure of L-type calcium channels |
|
|
Term
|
Definition
| spread of excitation through the myocardium creates small currents flowing through the ECF which can be detected on the body surface |
|
|
Term
| Describe Einthovens triangle |
|
Definition
| - 3 electrodes are placed on the limbs/chest to forma a triangle around the heart. Most common lead used is lead II |
|
|
Term
| What does lead II measure? |
|
Definition
| the surface electrical potential difference between LL and RA |
|
|
Term
| What does lead II reflect? |
|
Definition
| the spread of excitation from a longitudal aspect from base to apex of heart |
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
| What does the left side pump? |
|
Definition
| Blood to the body via the systematic circulation |
|
|
Term
| What does the right side pump? |
|
Definition
| Blood to the lungs via the pulmonary circulation |
|
|
Term
|
Definition
| Atrial systole begins and atrial contraction forces blood into the relaxed ventricles. Atrial diastole begins |
|
|
Term
|
Definition
| as ventricles contract, ventricular pressure exceeds atrial and the AV valves close. Pressure rises and semilunar valves are forced open, blood is ejected. |
|
|
Term
|
Definition
| Ventricular diastole causes ventricular pressure to drop and semilunar valves shut |
|
|
Term
| What is the lub heart sound |
|
Definition
| first sound: closure of the AV valves |
|
|
Term
| What is the dup heart sounds |
|
Definition
| second sound: closure of the semilunar valves |
|
|
Term
| What does the P-Q interval represent |
|
Definition
| measure of delay between atrial and ventricular depolarisation |
|
|
Term
| What does the Q-T interval represent |
|
Definition
| measure of duration of ventricular systole |
|
|
Term
| What does the T-Q interval represent |
|
Definition
| measure of duration of ventricular diastole |
|
|
Term
| Define cardiac output and the equation of how it is calculated |
|
Definition
volume of blood pumped by each ventricle per unit of time (Lmin-1)
CO = heart rate x stroke volume |
|
|
Term
What is the standard heart rate and stroke volume for a 70kg male at rest
therefore what is CO |
|
Definition
heart rate: 75bpm
stroke volume: 75ml
co: 5.25Lmin-1 |
|
|
Term
| What is the SAN innervated by? |
|
Definition
| both sympathetic and parasympathetic brances of the autonomic nervous system |
|
|
Term
| Which neurotransmitters and released and by what? |
|
Definition
Noradrenaline by postganglionic S fibres
acetylcholine released by P fibres |
|
|
Term
| What are para/sympathetic effects mediated by? |
|
Definition
P: muscarinic receptors
S: beta1-adrenoreceptors |
|
|
Term
| What is the resting and intrinsic frequency of the SAN? |
|
Definition
|
|
Term
|
Definition
| an abnormally rapid heart rate. |
|
|
Term
|
Definition
| abnormally slow heart action. |
|
|
Term
| Heart rate is increased by... |
|
Definition
| thyroxine, hyperthermia and drugs which mimic the effects of S stimulation or block the dominant P tone (e.g. atropine) |
|
|
Term
| What does parasympathetic stimulation lead to? |
|
Definition
the release of acetylcholine (ACh).
ACh decreases If (inhibits adenylate cyclase and reduces cAMP)- pacemaker potential is slowed and takes longer to reach threshold.
ACh increases the K+ permeability of the SA node cells (via IK-ACh) which hyperpolarises the maximum diastolic potential. |
|
|
Term
| What does sympathetic stimulation lead to? |
|
Definition
Stimulating the SNS leads to the following:
Rise in cAMP increases If so pacemaker potential rate accelerated
Reduction in K+ permeability so MDP more positive
Increased L-type Ca2+ current, so upstroke faster- more action potentials per unit time- tachycardia. |
|
|
Term
|
Definition
defined as the volume of blood ejected by each ventricle per heartbeat
SV equals the volume of blood in the ventricle at the end of diastole (end-diastolic volume, EDV) minus the volume of blood remaining at the end of systole (end-systolic volume, ESV) |
|
|
Term
| What is the ejection fraction? |
|
Definition
the fraction of the EDV ejected during the subsequent ventricular contraction
EF = SV / EDV |
|
|
Term
| What regulation is SV subject to? |
|
Definition
| both intrinsic and extrinsic |
|
|
Term
| What is the Frank Starling Law |
|
Definition
| the strength of contraction depends on the initial degree of stretch: increased EDV leads to increased stoke volume |
|
|
Term
| WHat does end-diastolic volume depend on? |
|
Definition
| venous return, which in turn depends on the pressure in the large veins returning blood to the heart: the central venous pressure (CVP) |
|
|
Term
| What are the factors that affect the CVP? |
|
Definition
Blood volume: increased blood volume → increased CVP
Postural changes
Respiratory and skeletal muscle ‘pumps’: these aid venous return and increased CVP
Venoconstriction (via increased sympathetic activity) → increased CVP |
|
|
Term
| Describe the autonomic regulation of SV? |
|
Definition
Sympathetic control
Effects are mediated by beta1-adrenoreceptors, this increases the influx of ca2+ into the ventricular myocyte during an AP |
|
|
Term
| Where is systematic blood pressure greatest? |
|
Definition
| in the aorta and declines throughout the circulation to reach 0 mmHg in the right atrium |
|
|
Term
| Where does the steepest drop in systematic blood pressure occur? |
|
Definition
| The steepest drop in pressure occurs in the arterioles, which offer the greatest resistance to flow |
|
|
Term
| What is systematic systolic pressure (BPs) |
|
Definition
Highest arterial pressure, corresponds to the systolic phase of the cardiac cycle
(Typical value: 120 mmHg) |
|
|
Term
| What is systematic diastolic pressure (BPd) |
|
Definition
| Lowest arterial pressure, corresponds to the diastolic phase of the cardiac cycle (Typical value: 80 mmHg) |
|
|
Term
| What is systematic pulse pressure? |
|
Definition
| (BPs - BPd) Typically 40 mmHg |
|
|
Term
| What is Mean Arterial Pressure (MAP) |
|
Definition
Calculated as:
BPd + (Pulse Pressure/3)
Typically (80 + 40/3) = 93 mmHg |
|
|
Term
|
Definition
| Fluid flow between 2 points is equal to the difference in pressure between the 2 points divided by the resistance to flow |
|
|
Term
|
Definition
|
|
Term
| How is CO, MAP and TPR related? |
|
Definition
|
|
Term
|
Definition
| increased local blood flow and increased rates of O2 delivery and CO2 removal |
|
|
Term
|
Definition
| receptors that are sensitive to pressure |
|
|
Term
| What does a rise in arterial pressure lead to? |
|
Definition
| stretches the arterial wall increasing the discharge rate of the baroreceptors |
|
|
Term
| What does an increase in baroreceptor discharge lead to? |
|
Definition
Increased parasympathetic and decreased sympatheic stimulation of the heart
Decreased CO
Decreased MAP |
|
|
Term
| How much O2 do cells of the body consume each minute? total |
|
Definition
|
|
Term
| How much CO2 do cells of the body produce each minute? total |
|
Definition
|
|
Term
How much air does an average male inhale per minute and how much of this reaches the alveoli?
How much is O2? |
|
Definition
|
|
Term
| Out of 880ml of O2, how much diffuses into the blood and how much is exhaled? |
|
Definition
250ml in blood
630 expired |
|
|
Term
| How do gases move through cell? |
|
Definition
Active diffusion
Lipid soluble |
|
|
Term
| What does Daltons Law state? |
|
Definition
| the pressure exerted by a mixture of gases is equal to the sum of the pressures that would be exerted by the individual gases occupying the same volume alone |
|
|
Term
| What happens to atmospheric air when it is inhaled? |
|
Definition
1. It is mixed with air in the respiratory ‘dead space’, which is relatively rich in CO2 and deficient in O2
2. It becomes saturated with water vapour (PH2O = 47 mmHg at 37OC) |
|
|
Term
| What does this result in? |
|
Definition
The result is that alveolar air has a higher PCO2 and a lower PO2 than atmospheric air:
PAO2 = 100 mmHg and PACO2 = 40 mmHg |
|
|
Term
| The rate at which a gas diffuses across the respiratory membrane is directly proportional to: |
|
Definition
(i) The concentration gradient across the membrane
(ii) The surface area of the membrane
(iii) The permeability of the membrane to the gas |
|
|
Term
| The rate at which a gas diffuses across the respiratory membrane is inversely proportional to: |
|
Definition
| the thickness of the membrane |
|
|
Term
|
Definition
| The amount of a gas that dissolves in a liquid at equilibrium depends on both the partial pressure of the gas in the gas mixture to which the liquid is exposed, and on the specific solubility of that gas in that particular liquid |
|
|
Term
| Which is more soluble, O2 or CO2? |
|
Definition
| This is because O2 is about 20 times less soluble than CO2 |
|
|
Term
| What occurs in pulmonary capillaries? |
|
Definition
| O2 diffuses from blood to cells (via interstitial fluid) and CO2 diffuses in opposite direction |
|
|
Term
| What occurs in systematic capillaries? |
|
Definition
| O2 diffuses from blood to cells (via interstitial fluid) and CO2 diffuses in opposite directions. |
|
|
Term
| State the Partial Pressures of O2 and CO2 in air |
|
Definition
|
|
Term
| State the Partial Pressures of O2 and CO2 in systematic arteries |
|
Definition
|
|
Term
| State the Partial Pressures of O2 and CO2 in pulmonary arteries |
|
Definition
|
|
Term
|
Definition
| a protein found in erythrocytes (red blood cells) which is capable of binding O2 in an easily-reversible manner |
|
|
Term
| Describe the structure of haemoglobin |
|
Definition
Hb consists of 4 sub-units, each of which contains a haem group (which contains an iron ion: Fe2+)
Each haem group is capable of binding one O2 molecule, so each Hb molecule can transport 4 O2 molecules |
|
|
Term
| What is the difference between oxyhaemoglobin and deoxyhaemoglobin? |
|
Definition
The complex of Hb and O2 is called oxyhaemoglobin (Hb.O2);
Hb without bound O2 is called deoxyhaemoglobin |
|
|
Term
| What does the binding or release of O2 by Hb depend on? |
|
Definition
| the PO2 in surrounding fluid: High PO2 facilitates binding; Low PO2 facilitates release |
|
|
Term
| When 100% saturated, 1 g of Hb carries ___ mL of O2 |
|
Definition
|
|
Term
| What is the O2-carrying capacity of Hb in the blood? |
|
Definition
| 200 mL O2 per litre of bloo |
|
|
Term
| What is the result of one o2 molecule biding to one of the Hb subunits? |
|
Definition
| changes its conformation, which increases the affinity of the other sub-units for O2, making it more likely that another O2 molecule will bind due to the conformational change to the molecule: positive co-operativity |
|
|
Term
| What affect does decreasing the affinity for Hb and O2 do to the curve? |
|
Definition
| shifts the curve to the right: this favours the unloading of O2 in the systemic capillaries (but inhibits O2-loading in the pulmonary capillaries) |
|
|
Term
| What affect does increasing the affinity for Hb and O2 do to the curve? |
|
Definition
| shifts the curve to the left: this favours O2 loading in the lungs, but inhibits O2 unloading in the systemic capillaries |
|
|
Term
|
Definition
| there would be factors that increase affinity in the pulmonary capillaries, and factors that decrease affinity in the systemic capillaries |
|
|
Term
| How does temp affect the affinity for Hb to O2? |
|
Definition
| An increase in temperature decreases the affinity of Hb for O2. |
|
|
Term
| How does ph affect the affinity for Hb to O2? |
|
Definition
| (Bohr effect): A decrease in pH decreases the affinity of Hb for O2. |
|
|
Term
| How does PCO2 affect the affinity for Hb to O2? |
|
Definition
| (Carbamino effect): CO2 reacts reversibly with certain amino acids in Hb to form carbaminohaemoglobin: |
|
|
Term
| How is CO2 transported in the blood? |
|
Definition
| Almost 90% as HCO3-, the rest dissolved in blood plasma or bond to Hb |
|
|
Term
| CO2 Exchange and Transport |
|
Definition
Cellular respiration produces around 200 mL of CO2 per minute
CO2 diffuses, via the ISF, into the plasma in the systemic capillaries, increasing the PCO2
CO2 diffuses into the erythrocytes, where it is converted to HCO3- and H+, a a reaction catalysed by the enzyme carbonic anhydrase
To prevent ‘product inhibition’ of this reaction, HCO3- is exchanged for Cl- ions from the plasma (the chloride shift) and the H+ ions are buffered by Hb (promoting the unloading of O2 from Hb.O2, which is an added benefit)
In the pulmonary capillaries, CO2 diffuses from the plasma into the alveolar gas, reducing the PCO2 in the blood
The series of reactions outlined above now proceeds in the reverse direction |
|
|
Term
| Describe the Haldane effect |
|
Definition
The binding of O2 to Hb reduces the affinity of Hb for CO2
therefore increases the rate of co2 elimination in the lungs |
|
|
Term
| What are the 3 major tasks physical exercises impose on the cardiovascular system? |
|
Definition
- Pulmonary blood flow must increase to enhance gaseous exchange in the lungs (obviously, ventilation must also increase)
- Blood flow through the working muscles must increase
- A reasonably stable blood pressure must be maintained |
|
|
Term
| In the case of exercise, O2 consumption may increase to up to about __ times its resting level. |
|
Definition
|
|
Term
| The corresponding 13-fold increase in O2 absorption by the pulmonary circulation is typically achieved by: |
|
Definition
a 1.5X increase in Stroke Volume
a 3X increase in Heart Rate
a 3X increase in Arteriovenous O2 difference |
|
|
Term
| In an untrained adult, CO can increase from around ____ at rest to a maximum of _____(a ___ fold increase) |
|
Definition
5 L.min-1
20-25 L.min-1
4-5 |
|
|
Term
| Heart rate rises linearly with work rate up to a maximum of ____bpm in adults |
|
Definition
|
|
Term
| Increase in heart is a result of: |
|
Definition
| decreased vagal (parasympathetic) inhibition and increased sympathetic stimulation of the pacemaker cells in the sinoatrial node |
|
|
Term
| What does Sympathetic stimulation of the atrioventricular node do |
|
Definition
| speeds up action potential conduction and shortens the AV delay |
|
|
Term
| What is increased stroke volume achieved by? |
|
Definition
| partly by an increase in filling pressure (which increases ventricular EDV) and partly by an increase in ventricular contractility (which increases ejection fraction and decreases ventricular ESV) |
|
|
Term
| What changes in systolic pressure during dynamic exercise |
|
Definition
| Systolic pressure rises markedly (by up to 60 mmHg during maximal exercise). This reflects the increases in stroke volume and ejection velocity |
|
|
Term
| What changes in diastolic pressure during dynamic exercise |
|
Definition
| Diastolic pressure is a reflection of TPR, which may rise only slightly (or even fall), depending on the balance between metabolic vasodilation and sympathetic vasoconstriction |
|
|
Term
|
Definition
| there is a large increase in pulse pressure and a more modest increase in MAP (around 20 mmHg) |
|
|
Term
| What is The Central Command Hypothesis |
|
Definition
| Proposes that the cerebral cortex both initiates voluntary muscle contraction and ‘commands’ the autonomic (and respiratory) neurones of the brainstem |
|
|
Term
| What is the evidence for The Central Command Hypothesis |
|
Definition
1. Heart rate may increase before the onset of exercise – an ‘anticipatory response’
2. After partial neuromuscular blockade, voluntary attempts to contract the partially paralysed muscle (requiring, presumably, a bigger central command signal) produce enhanced rises in heart rate and blood pressure |
|
|
Term
| What is The Peripheral Reflex Hypothesis |
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Definition
| Proposes that both proprioceptor inputs from joints and muscle and chemoreceptor inputs from the muscle contribute to the cardiovascular responses to exercise, particularly the pressor response (i.e. the observed increase in MAP) |
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Term
| What is the evidence for The The Peripheral Reflex Hypothesis |
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Definition
1.Heart rate continues to increase for 1-2 minutes after the onset of exercise, suggesting that the gradual interstitial accumulation of metabolites such as lactate and K+ ions could be driving the response
2. If a spygmomanometer cuff is used to occlude venous drainage from exercising muscles in a limb, these metabolites are retained in the muscle after exercise ceases: in these circumstances, the pressor response is partially maintained |
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Term
| What is central command responsible for? |
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Definition
| the initial increase in heart rate, mainly via a suppression of vagal outflow to the sinoatrial node |
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Term
| O2 transport is limited by: |
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Definition
1. The maximal attainable cardiac output
2. Extracellular resistance to diffusion between the erythrocytes and muscle myoglobin |
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Term
| The increased maximal attainable cardiac output is almost entirely due, both directly and indirectly, to changes in cardiac structure: |
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Definition
- The ventricular wall increases in thickness
- The ventricular cavities enlarge
- Myocardial vascularity increases |
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Term
| The following adaptations improve the rate of O2 diffusion from the erythrocytes to the muscle mitochondria: |
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Definition
- The development of new capillaries within the skeletal muscle vascular beds reduces the average diffusion distance
- Muscle mitochondria increase in number, especially at subsarcolemmal sites close to the capillaries
- Muscle myoglobin concentration increases |
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