MMED1005 Lecture 10: Week 10 tutorial
7 Jun 2018
School
Department
Course
Professor
Septal defects:
- Occur when a hole develops in the septum of the heart
- Two types:
o Atrial septal defect
o Ventricular septal defect
Action potentials – what exactly is meant by depolarisation?
- Imagine a cell, e.g. nerve cell, cardiac cell, etc.
- It has a semipermeable membrane with channels that allow ions in and out of the
cell
- At rest, there is a channel that allows K+ ions to move through
o At rest, it has a tendency to move inside → outside
o Inside of the cell has a negative potential compared to outside
- Depolarisation occurs when the inside of the cell becomes more positive/less
negative
o This can occur by Na+ moving into the cell
- There is a threshold potential, where an action potential is generated
How do SVT’s work? Are they anything to do with electrical disruptions within the heart,
which then causes an irregular rhythm?
- Superventricular tachycardia (SVT)
o abnormally fast beating of the heart
o usually cause by re-entry currents within the atria or between ventricles and
atria producing high heart rates of 140-250 (premature depolarisation,
speeding up)
Would we need to know the various layers of cardiac tissue?
- Yes.
Diastole and systole:
- Diastole:
o Relaxed muscle, blood filling the chamber
- Systole:
o Contracting muscles, blood ejected from the ventricle
Intrinsic control of heart rate:
- Coming from the pacemaker cells
Extrinsic control of heart rate:
- If there is an increase in parasympathetic activity heart rate slows down because
signals slow down
- Sympathetic speed up
Cardiac output:
- Venous return is the most important determinant of cardiac output
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Occur when a hole develops in the septum of the heart. Two types: atrial septal defect, ventricular septal defect. Imagine a cell, e. g. nerve cell, cardiac cell, etc. It has a semipermeable membrane with channels that allow ions in and out of the cell. At rest, there is a channel that allows k+ ions to move through: at rest, it has a tendency to move inside outside. Inside of the cell has a negative potential compared to outside. Depolarisation occurs when the inside of the cell becomes more positive/less negative: this can occur by na+ moving into the cell. There is a threshold potential, where an action potential is generated. Superventricular tachycardia (svt: abnormally fast beating of the heart, usually cause by re-entry currents within the atria or between ventricles and atria producing high heart rates of 140-250 (premature depolarisation, speeding up) Diastole: relaxed muscle, blood filling the chamber. Systole: contracting muscles, blood ejected from the ventricle.
