D4 The Heart Flashcards
the shart
Skeletal Muscle
Voluntary
Moves joints by strong and rapid contractions
Bundle of muscle fibres long multinucleated cell = muscle
Myoblasts fuse to create cell = also muscle regeneration
Stripy
Cardiac Muscle
Involuntary
Striated
Intercalated disc with gap junctions and desmosomes
Single central nucleus
Smooth Muscle
Gap junctions
Not striated actin and myosin randomly arranged
Structure of the cardiac muscle cells
Desmosomes
- hold cells together
Gap Junction
- allows cytoplasm to move (allowing action potential)
Intercalcated disks have the gap junctions
Single Nucleus
25-30% made of mitochondria
- aeorbic respiration NO LACTIC ACID
Cardiac Cycles / Heartbeat
A cycle is the time it takes to go from one heartbeat to the next
1 Heartbeat consists of 1 arterial and ventricular contractions.
The heart cycles at an average of 72 cycles per minute
1 cycle takes around 0.8 seconds to complete
Systole Contractions
Contracted Chamber
Leads to Increase in Pressure
Blood moves out of chamber
Diastole Contractions
Relaxed chamber
Leads to Decreased Pressure
Blood fills up
Valves
The heart makes a Lub-Dub sound
This occurs when the valves slam shut
Valves act as one-way doors that prevent blood from moving back into the previous chamber
Myogenic Contraction
The heart contracts myogenically
This means it occurs spontaneously and without the nervous system
It can happen because of the sinoatrial node (AKA Pacemaker)
Stethoscope and Murmurs
Proper positioning of the stethoscope to listen to each valve
Heart murmurs are the improper closing of the heart and backflow of the blood
Faulty valves at birth or damaged by disease, 20% are medical problems
Ventricle thickness
The left ventricle is thicker than the right because it needs to pump the blood to the extremities of the whole body
Blood Flow
DEOXYGENATED: Vena Cava → Right Atrium → Tricuspid Valve → Right Ventricle → Semilunar Valve → Pulmonary Artery → Lungs
OXYGENATED: Lungs → Pulmonary Vein → Left Atrium → Mitral Valve → Left Ventricle → Semilunar Valve → Aorta → Body
Pressure Changes in the Heart
Pressure in ventricles drops below that in atria, making the AV valves open; blood from atria drains into ventricles causing slow increase in pressure.
Rapid pressure increase closes AV valves (“lub”), when pressure rises above arterial pressure, blood is pumped to arteries as semilunar valves open; meanwhile atria are relaxed, but pressure starts to build up as blood from veins drain in.
Control of heart contractions through brain
1) CO2 accumulates in the blood
- The medulla oblongata senses a low pH
2) Medulla Oblongata Message through cardiac nerve
- Tells the sinoatrial node to increase the rate of the cycle
3) CO2 levels go back to normal or below normal
- Medulla sends a message to the SA node telling it to go back to resting rate through vagus nerve
Role of Adrenaline / Epinephrine (Hormones & Neurotransmitters)
Produced by glands on the kidneys known as the Adrenal glands
Released during stress & excitement
Tells the SA node to fire more often
Sphygmomanometer
Inflatable cuff w pressure gauge, pinches arteries to measure pressure
Electrocardiograms (ECG)
Y-axis is the measure of electrical activity
Data from electrocardiography can be used to assess heart conditions
Tachycardia (elevated resting heart rate)
Bradycardia (depressed resting heart rate)
Arrhythmias (irregular heart beats)
Fibrillations (unsynchronised contractions of the atria /ventricle)
Cardiac Assistance
Artificial Pacemakers
- A pulse generator that is attached to a couple of leads telling the heart to beat
Defibrillators
- Shock the heart back into it’s normal rhythm
Cardiac Issues
Atherosclerosis
Thrombosis
Hypertension
Atherosclerosis
Occurs due to the buildup of plaque (made of lipids, cholesterol and calcium) in the arteries (due to LDL high amounts)
Stiffens the muscle and causes the lumen to be smaller
In coronary arteries
Can cause a myocardial infarction (heart attack)
Thrombosis
Blood starts to clot within the blood vessels (in veins)
Means no movement of the blood
The clot can travel to the brain and block vessels there, which can cause a stroke
In the lungs it can cause a lung embolism
In the coronary arteries can cause a heart attack
Blood thinners can reduce clotting factors, however the negative effects is that on thin blood it’s easy to lose lots of it
Hypertension
Occurs when there is higher than normal blood pressure
Can be due to the narrowing of the blood vessel from plaque
Which leads to an increase of pressure because blood volume does not decrease but the vessel does.
Blood Pressure Reading
Systolic Pressure (should be high) pver Diastolic Pressure (should be low) mmHg
120/80 mmHg
left ventricle contraction force/refilling of the left ventricle
Systolic pressures issues
120 and lower = Normal
135 = Prehypertension
140-159 = Stage 1
160 and higher = Stage 2
I80 and Higher = Stage 3
From prehypertension to stage 2 to prevent any further weight loss is normally administered
Double Pump System
Circuit 1 - Lungs
Circuit 2 - Body
Cardiac Excitation-Contraction Coupling
(i dont think this is needed)
1) Current spreads through the gap junctions to contractile cell
2) Action potentials travel along the plasma membrane and the T tubules
3) Ca2+ channels open in the plasma membrane and the SR
4) Ca2+ induced Ca2+ release from SR
5) Ca2+ binds to troponin, which exposes the myosin-binding sites
6) Crossbridge cycle begins (muscle fibre contracts)
7) Ca2+ is actively transported back into SR and ECF
8) Tropomyosin blocks myosin-binding sites (muscle fibre releases)
