Physiology: circulatory system Flashcards
What is the circulatory system?
Network of organs and vessels responsible for transporting blood, nutrients, oxygen, carbon dioxide, hormones, and waste products throughout the body.
Components of circulatory system
- Circulatory fluid (hemolymph, blood)
- Vascular system (arteries, capillaries, veins)
- Propulsor organ (heart)
How does circulatory fluid move through body?
Propulsion:
- rhythmic contractions of heart
- elasticity of arterial vessels
- compression of vessels (by body movements)
- contraction of smooth muscle of vessels
Unidirectionality (making sure the fluid will only go in 1 direction):
- Presence of valves and/or septa
Hemodynamics
Dynamics of blood flow
Volumetric flow rate (Q) (hemodynamics)
Volume of circulatory fluid set in motion in unit of time. Proportional to difference in pressure (Poiseuilles law)
Hemodynamics (vessel type)
- arteries
- arterioles
- capillaries
- veins
Arteries
(number, special feature, functions)
- number: several hundred
- special features:
- thick, highly elastic walls
- large radii
- functions:
- passageway from heart to organs
- serve as pressure reservoir
Arterioles
(number, special feature, functions)
- number: half a million
- special features:
- highly muscular, well innervated walls
- small radii - functions:
- primary resistance vessels
- determine distribution of cardiac output
Capillaries
(number, special feature, functions)
- number: ten billion
- special features:
- very thin walled
- large total cross-sectional area - functions:
- site of exchange
- determine distribution of extracellular fluid between plasma and interstitial fluid
veins
(number, special feature, functions)
- number: several hundred
- special features:
- thin walled compared to arteries
- highly distensible
- large radii - functions:
- passageway to the heart from organs
- serve as blood reservoir
Hemodynamics (pressure, velocity, area)
In the circulatory system, how is the potential energy transformed to kinetic energy?
- potential energy is transformed into kinetic energy as blood moves through the blood vessels
- transformation due to the pressure generated by the heart as it pumps blood into the arteries
describe the energy within the circulatory system
(4 steps)
Potential Energy in the Heart
- heart contracts during systole
- generates pressure that pushes blood into the arteries
- pressure creates potential energy within the blood
Conversion to Kinetic Energy:
- blood moves from the arteries to smaller arterioles and then to capillaries
- the pressure gradually decreases
- kinetic energy of the blood increases as it accelerates through narrower vessels due to the conservation of mass and the principle of fluid dynamics
Blood Flow:
- kinetic energy of the blood allows it to flow through the circulatory system
- delivering oxygen and nutrients to tissues and organs
- while removing waste products
- blood flow driven by the pressure difference between the arteries and veins
- also driven by the pumping action of the heart
Return to Potential Energy:
- as blood moves through the capillaries and into the veins, its kinetic energy decreases as it encounters increasing resistance to flow
- decrease in kinetic energy is associated with a decrease in pressure
- when blood returns to the heart, it has largely transitioned back to potential energy
- ready to be pumped out again during the next cardiac cycle
high or low velocity after heart?
- high
- max pressure
- max velocity when potential energy becomes kinetic energy
is the transversal area in the circulatory system constant?
No
velocity, area and pressure from heart to capillaries?
- area increases
- velocity decreases
- pressure decreases
what happens after the velocity decreases?
- pressure decreases
- probability of energy transformation to
- movement decreases
diameter of vessel increases
what’s the name of the process during the exchange in capillaries?
-diffusion
-passive
-using the gradient
-takes time
why is the velocity so low in the capillaries?
- Gradient needs enough time to have the possibility to exchange oxygen, glucose, etc. with interstitial fluid
- passive diffusion with gradients
- active transport of e.g. glucose
- takes time because transporters are
involved - time to bind etc.
crucial because it allows sufficient time
for the exchange
- takes time because transporters are
from a microscopic view, is the movement of particles during capillary exchange fast or slow?
Fast
from a macroscopic view, is the movement of particles during capillary exchange quick or slow?
Slow
how does the velocity develop after passing the capillaries?
velocity increases
1. Decrease in cross-sectional area leads to increase in velocity because vessel diameter increases
2. Decrease in total-vascular resistance
- larger blood vessels have less resistance due to their larger lumens and fewer branches
- moves quicker in larger vessels
3. Smooth muscle contraction
- veins contain smooth muscle in their walls
- can contract or relax to regulate blood flow
- when smooth muscle contracts, it can squeeze blood forward, contributing to an increase in velocity
4. Gravity and Muscular Pump
- contribute to an increase in blood velocity as it moves from the lower extremities back towards the heart
5. One-Way Valves
- prevents back flow
- unidirectional
Why do pressure peaks occur in the aorta, arteries, and arterioles?
- pressure peaks occur due to heart activity
- with systolic pressure representing high peaks
- and diastolic pressure representing low peaks
Why do the pressure peaks disappear or decrease as blood flows through the capillaries?
Pressure peaks disappear or decrease due to the properties of capillary walls
- capillaries have thin, compliant walls
- can expand to accommodate the incoming blood volume during systole and recoil during diastole
- elastic recoil helps to dampen pressure fluctuations, resulting in a smoother flow of blood through the capillaries
- Diameter Changes: Capillaries undergo vasomotion, altering diameter to dissipate pressure
- Energy Dissipation: Blood flow through resistance vessels dissipates energy, smoothing pressure peaks
what is an open circulatory system?
what is a closed circulatory system?
- Annelids, cephalopods and all vertebrates
- Blood flows in continuous circuit made up of arteries, capillaries and veins
- Blood volume low
- High blood pressure
o Animal sizes are larger because of high blood pressure
o Allows ultrafiltration at capillary levels - Local circulatory system can be regulated (vasoconstriction and vasodilation)
- In vertebrates: a parallel circuit > lymphatic system > reabsorption of liquid passing through capillaries in the tissues.
what about the relationship of the volume and pressure of hemolymph and blood in open and closed circulatory systems?
- open
- high hemolymph volume
- space available for hemolymph in whole body
- low hemolymph pressure - closed
- low blood volume
- space available for blood only in vessels
- high blood pressure
- allows a flow under long distances
vasoconstriction?
narrows blood vessels, increasing pressure inside the vessel
mechanism: Constriction of vessel walls reduces vessel diameter, leading to increased pressure
vasodilation?
opposite of vasoconstriction
widens blood vessels, decreasing pressure inside the vessel
what are the functions of circulatory systems related to movement and erection?
overview: Arterial system
property: pressure reservoir
do fish have a large or short ventral aorta?
- a short one (possible due to fish heart structure)
- it’s very elastic for regulating the blood flow that goes to the gills
what does a fish heart consist of?
- venous sinus
- atrium
- ventricle
- bulbus arteriosum
- respiratory and systemic circulatory systems are NOT separated
- blood enters from right
- bulbus arteriosum is important for buffering pressure variations
blood pressure in fish
pericardium
- Definition: Double-layered sac surrounding the heart.
- Function: Protects the heart, anchors it in place, and prevents overfilling.
Pericardium in Fish
Description: Pericardium is semi-rigid in fish.
Function: Maintains negative pressure lower than atrial pressure.
Purpose: Facilitates rapid filling during ventricular systole.
Aortic Pressure Regulation in Fish
Description: Difference in aortic pressure between ventricular systole and diastole is limited.
Mechanism: High elasticity of the bulbs arteriosum.
Importance: Ensures efficient circulation and prevents excessive pressure fluctuations.
overview: Venous system
why does the blood or hemolymph spend more time in veins than arteries?
due to low velocity in veins
therefor: lots of blood inside the veins
what helps the flow and movement in the veins?
a muscle structure that contracts and squeezes the vein structure
increases pressure
increases flow
what problem comes due to squeezing the veins and how is it solved?
- problem: two directions of flow when squeezing
- solved by: valves
- Valves opening and closing is mechanical
- Opening through pushing due to increase of pressure
- Closed valve: closed due to increase of pressure after valve structure
It’s a mechanical movement (both)
how large are capillaries in diameter?
- 1mm long
- diameter: 3-10 micrometer
blood cells are usually 50 micrometer in diameter. how can they pass capillaries?
blood cells deformation allow the flow through capillaries
Important is the structure of capillaries: no vessel constriction in capillaries
The capillary wall is made up of a single layer of endothelial cells resting on a basement membrane (collagen and glucosaminoglycans)
capillary network overview
What are the two primary forces involved in the movement of substances across capillary walls?
it’s two forces that act in opposite directions
How do proteins retained in capillaries influence fluid movement?
Proteins retained in capillaries create a force that attracts water, known as the osmotic force.
What happens to the forces at the start of the capillary?
- At the start of the capillary, there is a significant outward pressure (blood pressure) and osmotic pressure.
- The combination favors blood pressure, with the sum of pressures being 11 mm Hg, thus favoring exit from the capillary.
- Substances must enter the interstitial fluid to reach different cells afterwards
How do pressure dynamics change at the middle of the capillary?
- At the middle of the capillary, decreasing volume leads to decreasing pressure.
- Although transfer stops, the process continues.
- Osmotic pressure remains constant
while blood pressure decreases. - The sum now favors osmotic pressure, at 9 mm Hg, directing substances from interstitial fluid into the capillary
e.g., uptake of CO2 produced by cells
What changes in pressure occur during capillary exchange?
Initially, there is an outward pressure of 11 mm Hg
followed by an inward pressure of 9 mm Hg.
It’s important to note that the amount leaving is not equal to what returns inside.
What problems can arise if interstitial fluid increases?
Increased interstitial fluid leads to inflation, as substances transfer through it via simple diffusion.
The increased fluid increases transfer time, necessitating the maintenance of a constant amount of interstitial fluid.
How is constant interstitial fluid maintained?
The lymphatic system
serves as an accessory system
limiting the interstitial fluid amount
Vessels within the lymphatic system can receive water and solutes from the interstitial fluid, allowing the extra fluid to reenter the circulatory system.
What is the role of the lymphatic system in fluid balance?
The lymphatic system plays a crucial role in regulating interstitial fluid volume.
It limits the amount of interstitial fluid and recaptures excess liquid, returning it to the circulatory system.
Arrangement of vascular systems
- single circulation
- e.g. fish - double circulation
- double secretion needs double entry
- division of vascular system
Why is high pressure in respiratory organs not desirable?
The structure of respiratory organs is very simple
it’s lacking multiple cell layers to withstand strong pressure
Thus, high pressure could potentially damage or disrupt their function.
How is the structure of respiratory organs adapted to infusion?
Respiratory organs have a simple structure with a low number of cell layers, - which facilitates infusion.
This adaptation is essential for efficient gas exchange.
What evolutionary significance does the distinction between systemic and pulmonary circulation have?
What distinguishes the heart muscle (myocardium) from skeletal muscle?
How does the activation of contraction differ between skeletal and cardiac muscles?
What is the role of gap junctions in cardiac muscle?
How does intrinsic activation function in the heart muscle?
Why is the heart muscle considered rich in muscle?
overview “heart”
squid- and octopus heart
How does the cardiovascular system of fish differ from that of octopuses and squids?
What challenges does the cardiovascular system of octopuses and squids face due to the distance between the heart and organs?
How does the cardiovascular system of octopuses adapt to maintain sufficient pressure?
heart in hagfish (overview)
What additional structure aids venous return in the hagfish cardiovascular system?
How does the hagfish heart ensure the proper flow of blood?
What regulates the function of the hagfish heart?
What insights does the hagfish heart provide into vertebrate evolution?
What is the function of the caudal heart in hagfish?
Why is there a need for an auxiliary heart in hagfish?
How does the contraction of muscles in the caudal heart chambers affect blood flow?
What happens during relaxation of the caudal heart chambers?
evolution of the vertebrate heart
What challenges does the amphibian heart face regarding blood circulation?
How does the amphibian heart prevent the mixing of oxygen-rich and oxygen-poor blood?
How does the amphibian heart ensure functional separation of blood flow?
What mechanism aids in directing blood flow in the amphibian heart?
the reptilian circulation
ventricle of turtles
- 3 interconnected internal sub chambers
1. cavum venosum
2. cavum pulmonale
3. cavum arteriosum - cavum venosum and cavum pulmonale are separated by partial septum
- cavum arteriosum connected to the cavum venosum by intercaval canal
3 large arteries come out of the ventricle
1. pulmonary artery
2. right systemic arch
3. left systemic arch
during a dive lungs can be bypassed by diversion of systemic venous blood directly back into the systemic circuit
that’s called “right-to-left shunting”
Describe the structure and function of the reptilian heart
heart of estuarine crocodiles
- complete separation of atria and ventricles by septa
- with clear division between systemic and pulmonary circulation
- they have 2 systemic aortas arising from each ventricle
- they are connected by the “foramen of Panizza”
- during ventilation: right aorta closed by valve
but: foramen allows blood flow also into the left aortic arch - during dive: lungs can be bypassed by the right aorta
because pulmonary artery is closed by the “cog-teeth valve”
foramen allows blood flow also in aortic arch
How does the heart of a crocodile differ from other reptiles?
What adaptations does the crocodile heart have for diving?
cardiac cells of the mammalian heart
- myocetes in
- sinoatrial node
- atrioventricular node - myocetes in
- inner surface of ventricle walls
- bundles of His
- Purkinje fibers - myocetes
- making up most of the myocardium
What are the key features of a mammalian heart?
What are the specialized cells present in the mammalian heart?
cardiac action potentials
- action potential in cardiac contractile cells differs
considerably from the action potential in cardiac autorhythmic cells - prolonged plateau phase
Explain the action potential in cardiac cells.
How is the action potential generated in cardiac cells?
How does the action potential lead to muscle contraction in cardiac cells?
What mechanism triggers muscle contraction in cardiac cells?
Describe the process of muscle contraction in cardiac cells.
How does calcium contribute to muscle contraction in cardiac cells?
cardiac output
neurogenic hearts in decapods
control of circulation
arterial system
the autonomic nervous system
the nervous system
autonomic nervous system: cholinergic and adrenergic
How is the activation of the heart different in crustaceans?
Why is regulating heart activity important in animals?
How is pressure generated in the circulatory system?
How is blood pressure regulated in the body?
How is organ perfusion regulated in mammals?
How does the nervous system regulate heart activity?
What are the different receptor types involved in the autonomic nervous system?
Action Potential Propagation in Crustaceans
Control of Circulation
Arterial System
Nervous System
Autonomic Nervous System
Baroreflex in response to change in blood pressure: Afferent Pathways
Baroreflex in response to change in blood pressure: Efferent Pathways
In the case of a hypertensive episode
increase in parasympathetic activity
Baroreflex in response to change in blood pressure: Efferent Pathways
If blood pressure falls below normal
sympathetic nervous system is activated
Baroreflex in response to change in blood pressure: adrenergic receptors
