D.4 The Heart Flashcards
Structure of Cardiac muscle cells
- Striated
- 1 nucleus
- involuntary
- Y shaped
- Short & Wide
- Have specialised junctions with intercalated discs (containing gap junctions)
- Rich in mitochondria
- Rich in glycogen granules
Allows for messages to travel fast to sllow all cardiab muscle cells to contact at the same time
Atrial Contraction
- Sinoatrial node in the right ventricle acts as the primary pacemaker. It sends out an eletrical signal to the atria via gap junctions in the intercalated discs.
- Atria systole occurs by having the cardiac muscles in the atria walls contract.
- Blood is pumped into the ventricles through the semiluna valves
- A signal from the sinoatrial node is then relayed by secondary messengers to the atrioventricular node with a delay, allowing the ventricles to fill with blood
Ventriclular contraction
- The Atrioventricular node receives a signal from the Sinoatrial node
- The AV node sends signals down the septum via the Bundle of his
- The Bundle of His send the impulse to the Purkinje fibres in the ventricular wall causing the muscle to contract at once
- This sequence of events ensures contractions begin at the apex (bottom), forcing blood up towards the arteries (aorta/ pulmonary artery).
Systole Vs Diastole
Systole = contract
Diastole = relax
Mapping of cardiac cycle to a Normal ECG trace
Electrocardiogram
PQRST
P wave = depolarisation of the atria in response to signalling from the sinoatrial node (atrial systole)
QRS complex = depolarisation of the ventricles (ventricular systole)
T wave = ventricle diastole
The use of artificial pacemakers to regulate the heart rate
An artificial pacemaker is a medical device that delivers electrical impulses to the heart in order to regulate heart rate
Cardiac output
Amount of blood pumped out of the heart in 1 min
= HR x SV
Effects on HR
exercise, age, disease, temperature, emotions, body size, altitude, stress, drugs, sodium & calcium ions in blood
Controlled by hormones and nervous system
Nervous system controlling heart rate
Sympathetic nervous system:
- release neurotransmitters to SA node to increase HR
Parasympathetic nervouse system:
- Release neurotransmitters to SA node to decrease HR
Effect of epinephrine on the HR
When released from the adrenal gland they travel through blood and attach to receptors in the heart
- Activation of the receptor increases the HR
Stroke Volume
Amount of blood pumped in each contraction from the left ventricle
systolic and diastolic blood pressure measurements
Measured in bracheal artery
average adult = 120/80 mmHg to 140/90 mmHg
Systole is at the top (Contraction of the venricles)
Diastole at the bottom (Relaxation of the ventricles)
Defibrilation
Fibrillation is the rapid, irregular and unsynchronised contraction of the heart muscle fibres
Fibrillation is treated with a defibrilator
- Sino actrial and atrioventricular node are not working in sync
Defibrilator sends electricle impulses through the heart to reset the sino atrial node
Hypertension
+ Causes
abnormally high blood pressure
causes of hypertension include a sedentary lifestyle, salt/ fat-rich diets and excessive alcohol or tobacco use
Thrombosis
the formation of a clot within a blood vessel in the circulatory system due to tares
- occurs in arteries when the vessels are damaged due to deposition of cholesterol
Thrombosis in coronary arteries = heart attack
In brain = Stroke
Plaque on artery wall = Atherosclerosis
Heart sounds
Reading a graph of blood pressure during systole and diastole
