Ch14 Flashcards
Which organ regulates blood pressure by regulating volume?
Kidney
What 3 parameters determine resistance for fluid flowing through a tube?
Length, radius, and viscosity
What is Poiseuille’s law? What is it simplified to in humans?
Resistance is proportional to (Length x viscosity) / (Radius^4)
1/(Radius^4)
If the radius of tube A = 2, what is the flow?
R=1/r^4=1/16
Flow = 1/R=1/(1/16)=16
What do autorhythmic cells lack compared to normal cardiac myocytes?
No organized sarcomeres hence no striations
How does the size of the t-tubules and the sarcoplasmic reticulum’s compare between cardiac and skeletal muscle cells?
T-tubules are larger in cardiac myocytes while the sarcophagi can reticulum is larger in skeletal muscle
How does the NCX transporter work in cardiac myocyte membranes?
It is a symporter that uses the Na+ gradient to pump Ca2+ out of the cell
How does the opening of the RyR gate compare in cardiac and skeletal muscle?
The skeletal myocytes use a DHP protein to open the RyR in the sarcoplasmic reticulum while cardiac muscle just uses the L-type Ca2+ channel in the membrane of the t-tubule
How are cardiac contractions graded?
By letting more or less Ca2+ into the myocyte
Why does stretch not affect cardiac muscle like skeletal muscle?
The heart has stretch-activated Ca2+ channels, meaning stretching can actually strengthen contractions
What is the resting membrane potential of skeletal and cardiac contractile myocytes?
S: -70mV
C: -90mV
What is the benefit of a long refractory period in cardiac muscle?
This disallows summation like in skeletal muscle, removing the possibility of tetanus poisoning
What is the resting membrane potential of contractile and autotrhythmic cardiac myocytes?
Autorhythmic cells are -60mV
Contractile cells are -90mV
How does the funny channel work?
As the cell naturally repolarizes after a contraction, the funny channel will open to let Na+ in at -60mV. It only lets it in slowly compared to the L-type Ca2+ channel whose threshold is -40 mV
What are the natural paces of the possible bodies of pacemaker cells?
SA node: 70 bpm
AV node: 50 bpm
Purkinje fibers: 25-40 bpm
In Einthoven’s triangle, where is there a group of two negative leads? Two positive?
Two negative leads are found on the right arm. Two positive leads are found on the left leg.
What are leads I, II, and III in Einthoven’s triangle?
I is right arm to left arm
II is right arm to left leg
III is left arm to left leg
What happens during a P wave?
Atrial depolarization
What happens during a P-R segment?
Conduction through AV node and AV bundle
What happens during the QRS segment?
Ventricular depolarization
What happens during the T wave?
Ventricular repolarization
Why isn’t atrial repolarization apparent on an ECG?
It’s too small to see
Why does the apex stay depolarized the longest compared to the rest on the ventricles?
It depolarizes first, but the top of the ventricles repolarizes first.
What is a first degree block in the internodal pathway?
Delay in internodal pathway. The P-R distance is extended
