Lecture 11 Flashcards
What are responsible for the heart contracting?
Cardiomyocytes
Cardiomyocytes can contract without a
Connection to the nervous system
Where are the APs for heart contraction coming from?
They are generated by the Cardiomyocytes themselves
Hearts have a specialized group of cells called
Pacemaker Cells
Pacemaker cells function to
Create APs that cause different chambers of the heart to contract
Why are Pacemaker Cells able to generate APs?
They have unstable resting membrane potentials
The unstable resting membrane potentials for Pacemaker cells are caused by?
Sodium channels called Funny channels
When do Funny Channels open?
During hyperpolarization and allow Na+ to enter the cell until the threshold is crossed and an AP occurs
Pacemaker cells are grouped together in the
SA Node
Pacemaker cells have the same three phases of AP, but they
Deal with Ca2+ ions instead of Na+ ions
What happens during Depolarization in Pacemaker cells?
Voltage-gated Ca2+ channels open and Ca2+ enters the cell
What ion causes for muscle contraction in the heart?
Ca2+
Voltage-gated Ca2+ channels open when
The threshold potential has been crossed in the pacemaker cells by funny channels and sodium entering the pacemaker cells
APs generated in the pacemaker cells cause muscle cells in the two atria to
Contract at the same time
The AP spreads across the muscle cells in the two atria until it reaches the
AV Node
What does the AV node function to do?
Delays the AP before it reaches the muscle cells in the ventricles, allowing the ventricles to contract after the atria
Heart pumps blood through the arteries via the
Systemic circuit
Arteries near the heart have a
Thicker tunica externa
A thicker tunica externa is composed of
Collagen fibers that strengthen the vessel to withstand this added force
Fluctuations in BP are a result of
Heart contractions
The speed at which blood is traveling is greatest in the
Left ventricle
Capillaries lack both a
Tunica externa and tunica media
How is the Tunica Intima in capillaries?
An extremely thin and porous
Blood moves the slowest in the
Capillaries
Differences in permeability are caused by
The fenestrations in the tunica intima
Continuous Capillaries are most commonly found in
Vertebrate circulatory systems and in muscle and lung tissue
What is the function of Continuous Capillaries?
They allow gas exchange to occur between the blood and lungs + deliver oxygen to muscles that use a lot of oxygen
Fenestrated Capillaries can be found in
The glomerulus of the kidneys, allowing kidney to filter blood
Describe Fenestrated Capillaries
Larger pores allow water, ions, and other small molecules to move into the kidneys
Sinusoidal Capillaries are
Extremely Porous
Sinusoidal Capillaries are found in the
Bone marrow
Veins have a
Thinner tunica externa
