micocirculation

Question 1

using starlings equation, determine the flow of fluid into or out of the capillaries.

Pc=20

Pif=-2

Oc=25

Oif=2

Answer 1

NFP=Kf[(Pc-Pif)-(Oc-Oif)]

hydrostatic increase=

oncotic pressure=

You can assume thePif and Oc to be constant… the biggest variable is going to be Pc

(20-2)-(25-2)= -5, fluid moves in to the vessels

Question 2

describe the histology of the vascular bed involved in regulating capillary resistance.

what is the regulation site?

Answer 2

1. flow volume is not equual through capillaries
2. regulation sites
   
   1. arterioles
3. metarterioles- shunt
   
   1. capillary bypass and regulate flow into capillary
   2. closing off the capillary, the blood will flow through here.
4. circular smooth muscle
   
   1. alters radius, therefore changing the resistance = less flow
   2. located
      
      1. arterioles
      2. precapillary sphincter

Question 3

describe the mechanisms of mypgenic response

Answer 3

myogenic reponse

1. VSMC respon
   
   1. sac opening-> increase na and Ca in ->depolarization ->increase calcium->VSMC contract

Question 4

describe VSMC

1. what makes them pulsatile? what are the consequences of this?
2. what overides this pulsatility?

Answer 4

vascular smooth muscle cells

1. undergo spontaneous alteration in tone due to intrinsic slow wave
   
   1. spontaneous depolarization due to Ca cauing depolarization
   2. blood flow through a given capillary is intermittent as blood is shunted between capillaries
2. overiding pacemaker-based pulsility are local** and **global regulators
   
   1. local
      
      1. myogenic
      2. paracrine
      3. metabolic
   2. global
      
      1. hormones and autonomics
         
         1. playa minor role in regulating microcirculation
         2. operate largely on arteries and veins

Question 5

what are the VSMC local regulation via paracrine?

Answer 5

1. NO
   
   1. major paracrine vasodilator
   2. response to a variety of events
      
      1. sheer
      2. pathogens
      3. injury
   3. induced by
      
      1. ACh
      2. ATP
      3. bradykinin
      4. serotonin
      5. substance P
      6. histamine
   4. action
      
      1. acttivation of guanylyl cyclase->increase cGMP->increase cGMP dependent protein kinase ->phophorylation of MLCK and SERCA
         
         1. MLCK is inhibited
         2. SERCA is inactivated
2. endothelin
   
   1. vasoconstrictor
   2. released by
      
      1. sheer
      2. hypoxia
   3. acts
      
      1. phospholipase C pathway

Question 6

what are the local hyperimic factors inducing vascular smooth muscle cells for vasodilation?

Answer 6

Hyperemia= regulation of blood flow based on metabolic activity

1. tissue dependent
2. pH
   
   1. mediated through indirect and direct pathways
      
      1. indirect
         
         1. contributes to NO production
      2. direct
         
         1. extracellular acidosis reducs intracellular calcium concentrations
   2. maint contributors
      
      1. CO2
      2. lactic acid
3. decrease in PO2
   
   1. releases
      
      1. adenosin
         
         1. binds to the A2 receptor
            
            1. increases cAMP->vasodilation
      2. prostaglandin 2
      3. NO release
         
         1. induces cGMP
4. ATP
   
   1. decrease in atp opens K channels (ATP dependent K channels)
      
      1. similar to pancreatic beta cells
      2. increases in K closes voltage gated calcium channels.

Question 7

How does the vasular bed (VSMC) resond to changin systemic pressure?

Answer 7

autoregulation- response by vascular beds altering resistance in reponse to changing systemic pressure to stabilize tissue perfusion.

increasing tissue perfusion = decrease in

Question 8

expalin the systems involved in global regulation of VSMC

Answer 8

sympathetic regulation, very little parasympathetic, is at the level of arteriole and small arteries and veins

1. brain regions regulating sympatheti tone aretonically active with frequency of activity varying and varying the vascular tone
2. respirationg make a contribution at lower frequencies
3. majority of vascular smooth muscles adrenergic receptors are
   
   1. a1
      
      1. ​induces constriction
      2. in higher concentration and require high concentration of E,
         
         1. overpower b2 b/c of higher amounts compared to B2
      3. prefers NE
   2. b2
      
      1. ​induces dilation
      2. in lower concentration and receptors are high affinity, need very little to cause dilation
      3. prefers E
   3. postganglionic sympathetic neurons also release
      
      1. NE,ATP, NY- all leading to 3 phases of contraction
   4. medullar releases E

Question 9

compare regulation of veins and arteries by the sympathetic nervous system

Answer 9

1. veins
   
   1. conttain ONLY a1
      
      1. can only contrict, NOT DILATE
   2. constriction is dependent on sympathetic tone, acting on veins before arteries
   3. also repond to
      
      1. paracrine and hormones
      2. not really influenced by hyperimic factors (metabolic)
   4. important for venous constriction during hemorrage and arterial dialtion
2. arteries
   
   1. Regultes the blood flow from one organ to another by changing total peripheral resistance (TPR)
   2. much of the body blood volume is in skeletal muscles
      
      1. TPR change is heavily targeted to skeletal vasculature

Question 10

TPR change is heavily targeted to which organ?

Answer 10

TPR change is heavily targeted to skeletal muscle vasculature.

hyperimic factors contribut greatly to this

pH being the most effective, causing dilation of the blood vessels

Question 11

Larger substances are most likely to move through which process through the cell?

Answer 11

trancellular, via endocytosis

Question 12

movement across the cell requires ATP. does this obey ficks law

Answer 12

No, ficks law operates off of diffusion. and requires no ATP

Question 13

NFP facors filtration in the ____ and reabsorption in the _____

Answer 13

NFP favors filtration in the first 2/3 of the capillary and reabsorption in the last 1/3

• hydrostatic pressure is greater in the first 2/3 and oncotic pressure is greater in the last 1/3

Question 14

how does water move in the interstitium

Answer 14

diffusion

Question 15

Lymph channels are found every where except ___(4). What is there instead?

how could head injury or broken bone play into question of lymph system?

Answer 15

lymph channels are found every where except: skin endomysium of muscle, bone and CNS

1. skin, endomysium of muscle and bones
   
   1. have small prelymphatic channels that join lymph vessels
2. CNS
   
   1. drain into CSF and then into the vessels

Head injury and broken bones are not conscerned with lymph flow?

Question 16

explain the movment of fluid from the interstitial fluid into the lymph capillary

Answer 16

fluid with colloids can enter the lymphatic capillaries unimpeded

Endothelial cells anchored to connective tissue. When the tissue swells with excess fluid, theanchoring filaments pull open the valve-> draining the excess fluid and then close the valve once in the lymph vessel

moving the fluid

1. intrinsic
   
   1. myogenic response to SAC as in capillaries( with smooth muscles)-> contracting and pushing the fluid to the next valve
2. extrinsic
   
   1. extrinsic compression forces that increase flow: surounding skeletal muscle
      1.

Question 17

what does not reabsorb in the kidney?

Answer 17

glomerulus is one of the few places that does not reabsorb

Question 18

when are veins fully dilated?

Answer 18

basal tonicity