Lecture 5 - Cardiovascular II Flashcards
list the vessels returning blood to the heart
superior and inferior vena cava, right and left pulmonary vein
list the vessels conveying blood away from the heart
pulmonary trunk –> L + R pulmonary arteries, ascending aorta
function of the aorta
carries oxygenated blood from the L ventricle to upper and lower body
Function of pulmonary arteries
carries deoxy blood from R ventricle to lungs
function of vena cava
carries deoxy blood from upper and lower body into R. atria
function of pulmonary veins
carries oxygenated blood from the lungs to the left atrium
describe why the brain receives a relatively large portion of blood from the heart compared to other organs
needs lots of energy to maintain membrane potential
Describe path of blood flow through the heart starting at the right atrium
right atrium –> tricuspid valve –> right ventricle –> pulmonary semilunar valve –> pulmonary arteries –> lungs –> pulmonary veins –> left atrium –> bicuspid valve –> left ventricle –. aortic semilunar valve –> aorta –> systemic circulation –> vena cava –> right atrium
function of superior vs inferior vena cava
superior: main route of blood from head, neck and upper limbs to the heart
inferior: main route from lower body to heart
describe the composition of the outer layer of arteries
connective tissue
describe the composition of the middle layer of arteries
smooth muscle and elastin
describe the diameter and function of elastic arteries
large diameter, helps propel blood onward while ventricles are relaxing
describe the diameter and function of muscular arteries
medium diameter, capable of greater vasoconstriction and vasodilation, helps adjust blood flow
composition of the inner most layer of arteries
thin sheet of endothelium
describe the stretch and recoil pattern of elastic arteries during ventricular systole and diastole
stretch during systole (contraction)
recoil during diastole (relaxation of ventricles), propels blood forward
describe the walls of arterioles
walls built of smooth muscle rings over elastic tissue
arterioles ______ when smooth muscle relaxes, _____ resistance
arterioles _____ when smooth muscle contracts, ____ resistance
dilates, decreasing
constricts, increasing
what do arterioles offer more of, compared to other vessels
offer more resistance to blood flow, can significantly affect BP via. vasoconstriction and vasodilation
Describe the walls of capillaries
thinnest wall of any blood vessel - consists of endothelial cells, forming a layer one cell thick.
describe the function of capillaries
site for diffusion of gasses, nutrients, and wastes between blood and tissues
describe the speed at which blood must flow in the capillaries in order to facilitate exchange
blood flow is slowest in the capillaries, must slow down to move substances in and out of the bloodstream
define thoroughfare channel
center vessel of capillary beds
what do capillaries branch into
capillary beds
function of precappillary sphincters
regulates the flow of blood into the capillary, can constrict and restrict blood flow
What are precapillary sphincters made of?
ring of smooth muscle
describe blood flow when the pre capillary sphincters are relaxed vs contracted
relaxed: blood flows through capillary bed
contacted: blood flows through thoroughfare channel (blood does not flow through capillary bed
do thoroughfare channels have precappillary sphincters
naur
In the sliding filament model of contraction, explain the state muscles filaments are in when ATP binds, where the ATP binds and the effect it has on both filaments
ATP binds to the head of myosin which reduces the affinity of myosin for actin causing the myosin to release from the actin filament. if all cross bridges/muscle were in this state, it would be fully relaxed
describe the process of ATP hydrolysis, where it occurs and the effect it has on actin and myosin in the sliding filament model of contraction. What state is the muscle in at this point
breakdown of ATP –> ADP and phosphate occurs on the myosin head. (Note: these products stay on the head of the myosin). hydrolysis –> head pivots around hinge (to a 90*C degree angle to the actin and myosin filaments). Rotation causes tip of the myosin to move along the actin filament to line up with a new actin monomer. “cocked state of myosin”, Muscle is relaxed
Describe cross-bridging in the sliding filament model of contraction
cocked myosin head binds to new actin monomer. ADPPi-myosin complex has an increased affinity for actin
what triggers the power-stroke . What happens and what kind of movement is generated
release of phosphorous from myosin . myosin head bends about the hinge –> Actin is pulled towards the tail of myosin molecule. Actin filament is drawn along the myosin filament –> generating force and motion
what happens when ADP is released from the myosin head in the sliding filament model.
actomyosin complex is left in a rigid state (attached state) –> completing cycle. myosin left at a 45 degree angle. complex remains bound until another ATP molecule binds to initiate another cycle
Describe how does cardiac muscle contraction is initiated
initially tropomyosin is blocking the actin binding sites on the myosin. calcium enters the sarcoplasm (cytoplasm of the muscle cell), binds to cardiac troponin –> moves tropomyosin away from actin binding site exposing where the actin will bind on the myosin. Now myosin head can bind to actin
what does smooth muscle use to develop force vs initiate contraction
smooth muscle cells use cross bridge to develop force and calcium ions to initiate contraction ( ??????)
what does the blood in capillaries flow onwards to
venules
describe the layers associated with the walls of venules
(outward) connective tissue coat, smooth muscle, endothelium (inwards)
describe the diameter and function of veins
large diameter, low resistance transport of blood back to the heart
describe the layers of veins from outer to inner
Connective tissue, middle layer of smooth muscle and elastic fibers, inner layer of endothelium
function of valves in veins
prevent backflow because very low pressure when travelling through veins
cause of varicose veins
valves dont function properly
compare and contrast arteries vs veins describing transport of blood, walls, flow, lumen and presence of valves
Arteries: carry blood away from heart under high pressure, thick walls, pulse flow, narrow lumen and no valves
vein: carries blood towards heart under low pressure, thin walls, smooth flow, large lumen and valves are present
function of the lymphatic system
picks up excess extracellular fluid and usable substances to return them to the cardiovsac. system
function of coronary arteries, veins and capillaries
hearts own network to supply cardiac muscle cells
importance of collateral routes in coronary circulation
back up routes so flow doesn’t fully stop, even if major vessels are occluded
describe the location of the right and left coronary arteries in terms of where they receive blood and cross
exit the ascending aorta just above the aortic valve. 2 branches subdivide and go over surface of the heart as they traverse away from aorta.
define Anastomosis and importance in coronary circulation
a point where two blood vessels join/merge. Provides collateral (alternative) routes of blood supply to the heart. Ex, branch of L coronary artery joins right branch
define oxygen tissue content
amount of oxygen available for production of energy to permit body function
define myocardial oxygen content
balance between how much oxygen is delivered to the heart minus oxygen consumed by the heart
what determines how much oxygen is delivered to the myocardium as long as pulmonary function is normal and there is sufficient haemoglobin
coronary blood flow
what does the amount of oxygen delivered to the heart depend on
lung function, haemoglobin present to carry oxygen, how much blood flows through the coronary arteries
how do you determine coronary blood flow
difference in mean pressure b/w the aorta and the right atrium where coronary blood empties
when is coronary flow greatest
diastole because it allows for the blood to flow more freely
myocardial ischemia
imbalance in myocardial oxygen demand and supply
what are some of the factors which may contribute to myocardial ischemia
increased heart rate (increases o2 consumption as both contraction and relaxation use o2 and decreases time for diastole)
describe what the circle of willis is and its importance
arterial circle via interconnected vessels in the brain. Large vessels originate from this to supply cerebral cortex. In sp. where circle is complete, blood flow to brain is maintained even with an obstruction at a single point
describe cerebral capillaries
non- fenestrated capillaries with tight junctions between endothelial cells
Describe diffusion and vesicular transport across cerebral capillaries
limited diffusion and vesicular transport
what are cerebral capillaries surrounded by
feet of astrocytes (glial cells)
What is the anatomic basis for the BBB
Cerebral capillaries
What does the BBB help maintain
maintains a constant composition of extracellular environment in the CNS
Role of the BBB
- protects the brain from endogenous and exogenous toxins
- prevents the escape of neurotransmitters into general circulation
Why are neurological diseases hard to treat
BBB limits the penetration of many therapeutic agents into the brain and spinal cord
What is the primary role of cerebral spinal fluid
protect the brain: serves as a cushion to limit trauma
what is cerebral spinal fluid pressure determined by
relative rates of formation and drainage
What is hydrocephalus
presence of excessive accumulation of CSF within the cranial cavity with subsequent dilation of the ventricular system
Symptoms of hydrocephalus
Head pressing, large dome shaped head, brain dysfunction, abnormal behavior, gait abnormalities
