Define myogenic.
Ability to contract without external nervous stimulation
How does the heart contract if it’s myogenic?
Stimulations with the heart cause depolarisation which send impulses throughout the heart to the apex, causing it to contract upwards, squeezing blood into the arteries.
What is the sinoatrial node and where is it located?
It is a small area of fibre near the vena cava.
How long does impulses pause for to allow atrial systole to be completed before passing down the Purkyne fibres?
0.13s
Where is contraction happening from to allow blood to be squeezed into the arteries?
The apex is contracted upwards.
(Apex is located at the bottom of the heart).
What is an ECG?
An electrocardiogram records electrical activity during the cardiac cycle; electrodes are attached to the chest and limbs, and a small current can be detected at the skin’s surface.
What is the P Wave on an ECG?
Atrial depolarisation, leading to atrial systole
What is PQ on an ECG?
Atrial Systole
What is PR on an ECG?
Time taken for impulses to be conducted from the SAN to the ventricles via the AVN
What is the QRS Wave on an ECG?
Ventricular waves of depolarisation, leading to contraction.
What is the ST on an ECG?
Ventricular Systole
What is T Wave on an ECG?
Repolarisation of ventricles during diastole.
Heart rate less than 60 indicates what
Bradycardia, a common system in fit athletes
Heart rate over 100 indicates what
Tachycardia, often linked to anxiety, fever or exercise.
Could be a symptom of CHD or fluid loss
What is ischaemia and what happens during it?
The heart tissue is deprived of oxygen due to blockage of coronary arteries.
Effects of adrenaline on the SAN, the arteries, and arterioles
On SAN, it increases heart rate and contractility.
It constricts arteries to non-essential organs, maximising blood flow to muscles.
It causes the dilation of arterioles suppling skeletal muscles.
What is tidal volume?
Volume of air breathed in and out in one breath.
What is vital capacity?
Maximum volume of air we can inhale and exhale
What is Minute ventilation (dm cubed per min)?
Volume of air taken into the lungs in one minute.
Multiple tidal volume by breathing rate for minute ventilation.
Lung volumes can be measured by spirometer
How is oxygen consumption found?
Find change in volume between two troughs of tidal volume measurements
How do you breathe?
Ventilation centre in the medulla oblongata controls breathing; the centre sends impulses every 2-3s to the external intercostal muscles and diaphragm, which contract to cause inhalation as pressure in the lungs drops.
During deep inhalation, neck and upper chest muscles are used.
As lungs inflate, stretch receptors in the bronchioles are stimulated, sending inhibitory impulses to the ventilation centre, stopping impulses to the muscles.
As diaphragm and intercostals relax, exhalation is permissible.
Exhalation is caused by the elastic recoil of the lungs and the lowering of the ribs.
Internal intercostal muscles only contract during deep exhalation.
What is the most important stimulus controlling breathing rate and depth at rest?
The concentration of CO2 in arterial blood via pH.
Small decrease in pH leads to large increase in ventilation.
What type of respiration do slow twitch muscle fibres undergo?
aerobic
What type of respiration do fast twitch muscle fibres undergo?
anaerobic
