Back to AI Flashcard MakerBiology /Biology IB HL - D4 The Heart Part 1
What is the heart composed of and how are these special?
The heart is composed of cardiac muscle cells which have specialised features that relates to their function.
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Key Terms
Term
Definition
What is the heart composed of and how are these special?
The heart is composed of cardiac muscle cells which have specialised features that relates to their function.
What are the 4 (basic) specialisations of cardiac muscle?
myogenic; branched; intercalated discs; mitochondria
What does it mean that cardiac muscle cells are myogenic?
Cardiac muscle cells contract without stimulation by the central nervous system (contraction is myogenic).
Why are cardiac muscle cells branched?
Cardiac muscle cells are branched, allowing for faster signal propagation and contraction in three dimensions.
What is the purpose of intercalated discs?
Cardiac muscles cells are not fused together, but are connected by gap junctions at intercalated discs.
What is the quantity of mitochondria in cardiac muscle cells?
Cardiac muscle cells have more mitochondria, as they are more reliant on aerobic respiration than skeletal muscle.
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| Term | Definition |
|---|---|
What is the heart composed of and how are these special? | The heart is composed of cardiac muscle cells which have specialised features that relates to their function. |
What are the 4 (basic) specialisations of cardiac muscle? | myogenic; branched; intercalated discs; mitochondria |
What does it mean that cardiac muscle cells are myogenic? | Cardiac muscle cells contract without stimulation by the central nervous system (contraction is myogenic). |
Why are cardiac muscle cells branched? | Cardiac muscle cells are branched, allowing for faster signal propagation and contraction in three dimensions. |
What is the purpose of intercalated discs? | Cardiac muscles cells are not fused together, but are connected by gap junctions at intercalated discs. |
What is the quantity of mitochondria in cardiac muscle cells? | Cardiac muscle cells have more mitochondria, as they are more reliant on aerobic respiration than skeletal muscle. |
What are the 3 (basic) properties are unique in cardiac tissue? | longer period of contraction and refraction; heart tissue does not become fatigued; cells separated between atria and ventricles |
Why does cardiac muscle need to have a longer period of contraction? | Cardiac muscle has a longer period of contraction and refraction, which is needed to maintain a viable heart beat. |
Why is it useful that heart muscle does not become fatigued? | The heart tissue does not become fatigued (unlike skeletal muscle), allowing for continuous, life long contractions. |
Why are the cells separated between atria and ventricles? | The interconnected network of cells is separated between atria and ventricles, allowing them to contract separately. |
What do intercalated discs allow for? | Cardiac muscle cells are not fused together but are instead connected via gap junctions at intercalated discs. This means that while electrical signals can pass between cells, each cell is capable of independent contraction. |
What controls the coordinated contraction of the heart? | The coordinated contraction of cardiac muscle cells is controlled by specialised autorhythmic cells (‘pace makers’). |
What is the SAN? | Within the wall of the right atrium is a specialised cluster of cardiomyocytes which directs the contraction of heart tissue. This cluster of cells is collectively called the sinoatrial node (SA node or SAN). |
What is the role of the SAN? | The sinoatrial node acts as a primary pacemaker, controlling the rate at which the heart beats (i.e. pace ‘making’). |
What does the SAN “Send out”? Where does the signal go? | It sends out electrical signals which are propagated throughout the entire atria via gap junctions in the intercalated discs. |
What is the result of the signal sent out by the SAN? | In response, the cardiac muscle within the atrial walls contract simultaneously (atrial systole). |
What are the atria and ventricles separated by? | The atria and ventricles of the heart are separated by a fibrous cardiac skeleton composed of connective tissue. |
What is the role of the non-conductive connective tissue of the heart? | This connective tissue functions to anchor the heart valves in place and cannot conduct electrical signals. |
How do the signals sent by the SAN travel through the non-conductive barrier? | The signals from the sinoatrial node must instead be relayed through a second node located within this cardiac skeleton. |
What is the second node of the heart? | This second node is called the atrioventricular node (or AV node) and separates atrial and ventricular contractions. |
How does the AV differ from the SAN? | The AV node propagates electrical signals more slowly than the SA node, creating a delay in the passing on of the signal. |
Why is there a delay between atrial and ventricular contraction? (general) | The separation of atrial and ventricular contraction is important as it optimises the flow of blood between the heart chambers. |
Why is there a delay between atrial and ventricular contraction? (specific) | The delay in time following atrial systole allows for blood to fill the ventricles before the atrioventricular valves close. |
When does ventricular contraction occur? | Ventricular contraction occurs following excitation of the atrioventricular node (located at the atrial and ventricular junction). |
Where does the AV send signals down? | The AV node sends signals down the septum via a specialised bundle of cardiomyocytes called the Bundle of His. |