cardiorespiratory Flashcards
in which direction do K+ ions move, why, and what effect does this have?
- ions move out of the cell down a concentration gradient due to higher intracellular concentration
- hyperpolarising effect
in which direction do Na+ and Ca2+ ions move? what effect does this have?
- ions move into the cell due to higher extracellular concentration
- depolarising effect
what is the difference in depolarisation due to influx pf Na+ ions, and Ca2+ ions?
Na+ channels cause rapid depolarisation, which is short-lived due to rapid inactivation
open potassium channels cause sustained depolarisation
what is the primary substrate for ATP in myocardial metabolism?
fatty acids
how is ATP supplied during moderate or submaximal exercise?
80% by fatty acids
how is ATP supplied during heavy exercise?
oxidation of lactate
why is resting heart rate lower than the rate at which the SA node fires?
parasympathetic stimulation of the vagus nerve causes a decrease in HR
at which points in exercise is there sympathetic and parasympathetic innervation?
parasympathetic activity inhibited (vagal stim) occurs early in exercise
sympathetic innervation increases as exercise increases
what is the effect of switching off vagal stimulation during exercise?
rate of depolarisation increases, threshold is reached more rapidly
what is the site where the greatest regulation of blood pressure occurs?
arterioles
why is a decrease in pressure important for venous return?
arterial blood has a pressure of 90mmHg, this needs to decrease to 1mmHg for return to the heart
what is the mean arterial pressure?
93mmHg
where does the resting potential of vascular smooth muscle cells sit?
around -40mV
what are the intrinsic mechanisms for control of blood pressure?
1) metabolic regulation
2) endothelial regulation
3) myogenic regulation
what are the main cardiovascular adaptations to training?
- increase in heart size
- increased stroke volume
- decrease in overall HR and recovery time
what ECG changes occur during exercise?
slight increase in P wave amplitude shortening of P-R interval shift to the right of the QRS axis S-T segment depression occasional ectopic contractions
what is indicated by an exaggerated ST-depression during an exercise stress test?
coronary heart disease
how is maximum heart rate calculated?
208 - 0.7 x age
on what does stroke volume depend on?
- venous return
- ventricular dispensability
- ventricular contractility
what does external respiration consist of?
pulmonary ventilation and pulmonary diffusion
what does internal respiration consist of?
transport to and from tissue, capillary diffusion and exchange
what happens during inspiration?
- diaphragm flattens, external intercostal muscles contract
- volume in the lung increases, pressure decreases, causing air to move in
what happens during expiration?
- diaphragm relaxes, external intercostal muscles relax
- volume in the lung decreases, pressure increases and air moves out
how does the process of expiration change in exercise?
it becomes an active process, internal intercostal muscles pull the ribs back down to increase rate of expiration
what is tidal volume?
volume moving in and out during each breath
what is vital capacity?
greatest amount of air that can be expired after maximal inspiration
what is residual volume?
amount of air retained in the lungs after maximal expiration
how is total lung capacity calculated?
sum of VC and RV
what is the role of the bronchial tree?
increases surface area over which gaseous exchange can occur
what causes bronchoconstriction?
cold, allergens, parasympathetic activity
what causes bronchodilation?
sympathetic activity, adrenaline/noradrenaline, exercise, B2-agonists
what are alveoli?
air sacs at the end of bronchioles
how much blood does the pulmonary circulation get per minute?
4-6L at rest
why do pulmonary vessels have less smooth muscle than systemic vessels?
pressure drop is much smaller
how does a change in partial pressure facilitate gas exchange at the alveoli?
oxygen moves in due to lower pressure, CO2 moves out into the lungs
what is daltons law?
total pressures of a mixture of gases equals the sum of the partial pressures of the individual gases in that mixture
how are oxygen and carbon dioxide transported in the blood?
O2: 2% diffused freely in the blood 98% combined with Hb
CO2: 60-70% dissolved in the blood as bicarbonate ions, 7-10% dissolved as free CO2, 20% of this binds Hb
describe how partial pressures facilitate movement of oxygen into arterial blood
pO2 in the pulmonary arterial blood is lower than alveolar gas, therefore O2 diffuses into the blood
what is the role of myoglobin?
transfers oxygen into the cell, and to mitochondria for oxidative phosphorylation
how is breathing regulated?
autonomic and voluntary control. respiratory control centres in the medulla oblongata and pons
what are the types of chemoreceptors?
central: sense pCO2, pH
peripheral: sense pO2, pCO2 and pH
what are the initial and later changes in pulmonary ventilation during exercise caused by?
initial changes due to neural inputs
later changes occur due to changes in chemical composition of the blood gases/pH
what does ventilatory threshold refer to?
the process by which ventilation will increase disproportionately to O2 consumption in order to remove excess CO2
name 3 respiratory disorders which limit the ability to exercise?
- Asthma
- Fibrosis
- COPD
what is pulmonary hypertension? what are the effects of this?
high blood pressure in the arteries of the lungs
arteries become less compliant, reduced blood flow, heart failure, death
what does the Nersnt equation allow? what does it assume?
calculation of resting potential from [intracellular] and [extracellular]. assumes the membrane is only permeable to one ion
how is contraction coupled in cardiac muscle?
each cell is connected through gap junctions
how is vasomotor tone regulated?
variable resting potential of around -40mV can be modulated. Ca2+ and Na+ influx via non-selective channels cause vasoconstriction, potassium influx causes dilation
what causes a decrease in stroke volume?
decrease in vascular resistance due to vasoactive metabolites
what is sympatholysis?
balance of sympathetic stimulation that causes an increase in contraction and decrease due to local metabolism
what causes long-QT syndrome?
mutations to Ikr or Iks channels
what is the impact on cardiac function associated with long-QT?
the heart fails to contract as a syncytium.
what is hypertrophic cardiac myopathy?
where cardiomyocytes are misaligned, commonly caused by mutations to B-myosin heavy chain, myosin binding protein C, cardiac troponin T or tropomyosin. causes force generation impairment and fibrosis
how does long qt cause sudden cardiac death?
reversion to irreversible ventricular fibrillation
