Lecture 10 - Circulation Flashcards
Components of the Circulatory System
- Heart: muscular pump
- Blood: fluid that can transport things around the body
- Blood vessels: conduits through which the fluid can be pumped around the body
Purpose of the Circulatory System
Pump nutriients, respiratory gases, wastes, hormones
Atrium
- region of the heart that receives incoming blood
* A = first
Ventricle
Region of the heart that pumps outgoing blood
Arteries
- Carry blood away from the heart
- branch out into arterioles
A=away
Veins
- Carry blood back to the heart
- smaller vessels (venules) join together to form larger vessels
Capillaries
- where arteries (arterioles) and veins (veinules) meet
- thiny, thin walled
Fish Circulatory System
- 2 chambered heart
- blood is pumped in a single circuit
heart–> gills–> tissue of the body –> heart
Process:
- Atrium receives blood from the body
- pumps it into the more muscular ventricle
- ventricle pumps blood to gills (gas exhange)
- blood elaving gills colelcts in large artery
- distributes blood to smaller arteries leading to tissues and organs of the body
- in tissues blood flows through beds of capilllaries
- blood collects in veins
- returns to atrium of heart
What is the disadvantage of fish circulation?
- blood loses pressure as it travels through gills
- limits ability to supply tissues with nutrients, oxygen
Why do birds/mammals have a different system of circulation?
- high nutrient demands and thus a very high density of vlood vessels
- heart must generate a high blood pressure to perfuse all the vessels
- have developed two separate circuits for blood flow
1. pulmonary (heart–> lungs –> heart)
2. systemic (heart –> tissues –> heart)
oxygenated blood can be pumped out of the heart to tissues at hihg pressure
Features Separate Pulmonary and Systemic Curcuits
- 4 chambered hearts
- Two Circuits:
1. Pumlonary
2. Systemic - Oxygenated and deoxygenated blood cannot mix
- Systemic receives blood with highest oxygen content
- blood with lowest oxygen content and highest CO2 is sent to lungs
- Can operate at different pressures
- large/higher pressure to pump blood through vessels of systemic
- lower pressure needed for pulmonary circuit in lungs
Comaprison of Pressure in Systemic and Pulmonary Circuit
- systemic: large pressure needed for pumping blood thruogh all the vessels (longer distance)
- pulmonary: lower pressure (shorter distance)
Features of the Human Heart
- Right atrium: receives deoxygenated blood from systemic circuit
- right ventricle: pumps deoxygenated blood through pumlonary circuit to get deoxygenated
- left atrium: receives oxygenated blood from the pulmonary circuit
- left ventricle: pumps oxygenated blood through the systemic circuit to get delivered to tissues
* one way valves prevent back flow
Right Heart vs Left Heart
- right heart receives deoxygenated blood (blue) and pumps it to lungs
- left heart receives oxygenated blood (red) and pumps it to the body
Path of Blood flow INTO the heart (right side)
- right atrium receives deoxygenated blood from superior and inferior vena cava
- Blood flows through an atrioventricular (av) valve into the right ventricle
- filling of the ventricle results from passive flow while the heart is relaxed between beats
- at the end of filling, the right atrium contracts
Where does the heart recieve blood from?
- superior and inferior vena cava
- into the av valve
How blood is pumped to lungs (2)
- right atrium contracts, right ventricle contracts
- AV valve closes
- Blood is pumped into the pulmonary artery leading to lungs (through pulmonary valve)
- gas exchange occurs in the lungs
- oxygenated blood returns to heart via the pulmonary veins
How blood flows in heart after beind oxygenated in lungs (3)
- re-enters heart in left atrium
- blood enters left ventricle through another AV valve
- ventricular filling is passive, completed with the atria contract
- left ventricle (very powerful), contracts
- pushes open aortic valve
- blood rushes into aorta to begin circulation throughout the body
The Cardiac Cycle
* both sides of the heart contract at the same time
- relaxation
- contraction of the two atria
- contraction of the two ventricles
Two phases:
- diastole:
- ventricles relax
- at very end, atria contract
- systole:
- ventricles contract
What are the sounds of the heart beat?
- as ventricles begin to contract, AV valves close
- “lub”
- transition from diastole to systole
- as ventricule begin to relax, aortic and pulmonary valves close
- “dup”
- transition from systole to diastole
What is a heart murmer
- when valves do not close completely, there is a backwards flow of blood
- “whoosh”
What is your pulse?
- pressure wave created by the contraction of the left ventricle in systole
Properties of Cardiac Muscle Cells
- has electrical signaling properties (like a neuron)
- can fire action potentials
- cardiac muscle cells are directly connected to each other via gap junctions
- cytoplasms are connected so direct and rapid spread of electrical signal
- coordinated contraction
How do cardiac cells communicate?
- gap junctions
- dont use neurotransmitters
Pacemaker cells
- cardiac muscle cells that can initiate action potentials without stimulation from the nervous system
- fire action potentials and stimulate neighboring cells to contract
- Sinoatrial (SA) node is the primary pacemake of the heart
Sinoatrial Node
Primary pacemake of the heart
in right atria
Properties of the pacemaker
- slower to rise
- broader
- slower to return to resting potentia
Process of Pacemaker
- RESTING
- specialized Na+ channels are open
- open at hyperpolarized voltage
- resting potential is less negative
- RISING
- voltage gated Ca++ channels open –> ca++ influx
- open and close more slowly than voltage gated Na+ channels = broader shape
- FALLING: same as usual
*hyperpolarization then causes the Na+ channels to open and AP start again
- voltage gated K+ chanels open
Nervous System and Heart Beat
- rate of heart beat can be controlled by nervous system
- regulates rate at which the resting potential dirfts upwards toward threshold
- some neurotransmitters can stimulate depolarization
- resting potential reached more quickly
- interval between pacemaker AP is decresed
- heart beats faster
- some neurotransmitters stimulate hyperpolarization
- membrane potential rises even more slowly
- interval between pacemaker action potentials lengthen
- heart slows down
Process of pacemaker and atrial contraction
- heart beat begins with AP in sinoatrial node
- action potential spreads rapidly through electrically coupled cells of the atria
- there ar no gap junctions between the cells of the atria and the cells of the ventricles
* ventricles do not contrac tin unison with the atria
atrioventricular (AV) node
- at junction of atria and ventricles
- specialized cardiac cells
- stimulated by depolarization of the atria
Ventricular Contraction
- AV node generatea AP
- conducted to ventricles via “bundle of his”
Bundle of His
- modified muscle fibers that conduct signal but do not contract
- branches out across ventricles as Purkinje fibers
- ensure that cardiac action potential spreads rapidly and evenly
- muscle cells of the ventricles experience AP and contract
Unique Properties of Cardiac Muscle Cells
- very long depolarization phase
* allows for prolonged muscle contraction -
rising phase
* is due to Na+ channels like a normal AP - Falling
- Voltage gated Ca++ channels open
- allows for extended plateau of depolarization
- Ca++ allows muscle cells to contract
- falling phase is due to K+ channels like normal AP
Summary of Contraction Patterns
- right and left atria contract at the same time
- coordinated by gap junctions
- the right ventricle and the elft ventricle contract at essentially the same time
- coordinated by bundle of his, purkinjie fibers, gap junctions
- Atria and ventricles contract at different times
- signal originates in sinoatrial node (atria) and spreads to AV node (ventricles)
What coordinates the atria to contract?
gap junctions
What coordinates the right and left ventricles to contract?
- bundle of his, purkinjie fibers, gap junctions
ECG/EKG
Electrocardiogram
Electrical events int he cardiac muscle can be recorded by electrodes on the surface of the body
Features of EKG
P=depolarization of the atrial muscle
- atrial contraction
- end of diastole
Q-S= depolarization fo ventricles
- ventricle contraction
- blood pumped out
- systole
- start AV valves close
- lub)
T= relaxation and repolarizatoin of ventricles
- start of diastole
- aortic and pulmonary valves close
- “dub”
