What drives blood flow? What is the equation?
pressure differences
ΔP = P1 - P2
How does pressure difference and resistance affect flow?
Flow = Pressure difference (ΔP) / Resistance to flow (R)
increase in pressure increases flow
increase in resistance decreases flow
What is the equation for resistance? How is it related to flow?
Resistance = length x viscosity / r^4 = 1 / r^4
Flow =ΔP / R =ΔPr^4
What is systemic MAP? pulmonary? What accounts for the difference between systemic and pulmonary flow?
93 mmHg
10 mmHg
less force generated by right ventricle
less distance blood must travel (decreased resistance)
How does pressure change across the circulatory system? Why?
it decreases due to resistance
What vessel has the greatest resistance?
arteriole
What is the equation for mean arteriole pressure (MAP)? Pulse pressure (PP)?
MAP = diastolic + (PP/3)
PP = systolic - diastolic
How is pressure maintained during diastole?
Windkessel effect
- elastic recoil of the great vessels
How does atherosclerosis affect blood pressure?
increase blood pressure
What is the equation for cardiac output?
CO = stroke volume (SV) x heart rate (HR)
How does resistance in series and in parallel affect blood flow? How does this relate to the human CV system?
Resistance in series is the sum of all resistance while the resistance in parallel is the inverse of the sum of resistance
This means in parallel circuits, flow will mostly take the path of least resistance.
The human CV system is a parallel system
What effect does Ca2+ have on smooth muscle? cAMP?
Ca2+ = contraction
cAMP = relaxation
What two general factors affect vascular tone?
extrinsic factors and intrinsic factors
What are the 3 types of extrinsic factors?
Hormones
Neuronal (SNS)
Vascular smooth muscle differences
What are the types of hormonal extrinsic factors?
vasodilators
epinephrine at low levels
vasoconstrictors
angiotensin II
Vassopressin
epinephrine at high levels
What are the type(s) of SNS extrinsic factor(s)
norepinephrine
What are the vascular smooth muscle differences that affect vascular tone?
Depending on the location, smooth muscle will either express alpha 1 or beta 2 receptors
What are the 3 types of intrinsic factors?
myogenic autoregulation
metabolic regulation
endothelium derived factors
What is myogenic autoregulation and how does it work?
vascular smooth muscle will contract or relax depending of the pressure is too low or too high, respectively
What are the two types of metabolic regulation?
Activer hyperemia
local tissues will release vasodilators to increase blood flow according to metabolic needs
Reactive hyperemia
local tissues release vasodilators in the event of a clot. The vessel returns to normal diameter when the clot has passed and vasodilators are washed away
What are the 2 endothelial derived factors? When are they made?
NO
relaxes muscle when drag friction experienced by cell is great
Endothelin
contracts muscle when drag friction experienced by cell is low
How does vascular tone determine distribution of blood flow?
Organs are connected via parallel circuit. Flow will take the path of least resistance. By increasing and decreasing vascular resistance, the body can direct blow flow according to its needs
What is compliance? Where in the cardiovascular system is it highest? Why?
Compliance is the ability to stretch and rebound
Compliance is highest in veins, which allows for it to act as a blood reservoir
Where are baroreceptors located?
in the carotid sinus and in the aortic arch
What controls the baroreflex? ow does it work?
medulla oblongata
Baroreceptors are mechanoreceptors that respond to pressure. Increased stimulation due to increased pressure tells the medulla to decrease sympathetic outflow and increase parasympathetic outflow. If pressure is low, baroreceptor activation will be low resulting in the increase sympathetic flow and decreasing parasympathetic flow
What does ansa cervicalis innervate?
superior belly of omohyoid
sternohyoid
sternothyroid
thyrohyoid
What does V3 innervate?
mandibular branch
anterior belly of digastric
mylohyoid
What does VII innervate?
platysma
posterior belly of digastric
stylohyoid
What does IX innervate?
sensory to pharynx, carotid sinus, and carotid body
What does XI innervate?
SCM and trapezius
What does XII innervate?
hypoglossus
What does prevertebral fascia contain?
deep neck muscles
scalenes
What does the carotid sheath contain?
common carotid a.
IJV
CN X
What does pretracheal fascia contain?
thyroid gland
trachea
esophagus
What does investing fascia contain?
trpezius
SCM
CN XI
What does superficial fascia contain?
platysma
nerves
superficial veins
What does superior laryngeal n. innervate?
internal laryngeal = sensory for larynx above vocal cords
external laryngeal = motor for cricothyroid
What does recurrent laryngeal n. innervate?
motor and sensory to larynx below vocal cords
What are the general three layers of blood vessels
tunica intima:
- endothelial cells
- basement membrane
- internal elastic lamina
tunica media:
- smooth muscle with varying degree of elastic fibers
- external elastic lamina
tunica adventitia:
- Type I collagen
- Elastic fibers
- Vasa vasorum
Where are elastic arteries found? muscular arteries?
elastic:
- aorta, pulmonary artery, branches of great vessels
muscular:
- all other arteries. They distribute blood to organs
What are the three types of capillaries?
continuous
fenestrated
sinosoids
Describe continuous capillaries with regards to their basement membrane and function. Where are they located?
continuous basement membrane
highly regulated exchange between tissue and blood
located most place within the body
Describe fenestrated capillaries with regards to their basement membrane and function. Where are they located?
fenestrated basement membrane
rapid exchange of substances between tissue and blood
kidneys and more
Describe sinosoid capillaries with regards to their basement membrane and function. Where are they located?
large perforations in basement membrane
maximum exchange between tissue and blood
spleen, bone, and more
What causes blood velocity to be low in capillaries?
blood velocity = CO/total cross sectional area
the total cross-sectional area of capillaries is extremely large
What are the two mechanisms of transcellular exchange?
diffusion
- membrane permeable substances move through the cell
transcytosis
- uses vesicles to capture substances by endocytosis and release by exocytosis
What drives diffusion? what is the relationship between diffusion and distance?
diffusion is driven by a concentration gradient
time of diffusion increases with the square of the distance
What is paracellular exchange? How does this relate to capillaries?
The passage of substances through spaces between or through cells
exchange of particles is mediated by the type of capillary
What is hydrostatic pressure? how does it change over the length of the capillary?
hydrostatic pressure = [hydrostatic pressure in capillary] - [hydrostatic pressure in interstitial space]
it decreases
What is oncotic pressure? how does it change over the length of the capillary?
oncotic pressure = [capillary osmotic pressure] - [interstitial osmotic pressure]
it remains relatively constant
What is edema?
excess fluid in the interstitium
What current is only found in pacemaker cells?
If
What current is responsible for phase 0 in non-pacemaker cells?
INa
what current is responsible for phase 0 in pacemaker cells and the calcium influx in phase 2 in non-pacemaker cells?
ICa.L
What current is responsible for phase 2 and 3 and the repolarization phase in pacemaker cells
IKs and IKr
What current is responsible for phase 1?
ITO
What current is responsible for phase 4 in non-pacemaker cells?
IK1
How does the SNS affect pacemaker cells? How does the PNS?
SNS increases the If current
PNS decreases the If current
Why is it important to have a long absolute refractory period in the heart?
The refractory almost lasts as long as the entire muscle twitch to avoid tetanus