APK 2105C Lecture Notes - Lecture 33: Brachial Artery, Muscle Tone, Arteriole

34 views2 pages
Chapter 14, Lecture 4
Vessels & Blood Pressure
Arterioles
o Provide greatest amt of resistance to blood flow (>60% TPR)
Resistance in capillaries vs. arterioles
Capillaries have larger total areaspread out pressure/resistance
o Why they are not more resistant than the arterioles
o Very low resistance in capillaries
o BP drops off in capillaries
o Velocity of blood flow is very low in capillaries
o First part of microcirculation
o Very important for BP regulation and blood distribution to organs/capillary beds
o Through all the arteriesmaintain BP very well/easily
Why can measure BP at brachial artery
When you get to arterioles = drop in pressure (large)
Largest pressure at arterioles because very small radius, lots of
muscle tone
Slows things down, decrease pressure in capillaries
o No pressure in capillaries
o No muscle in wall of capillaries
o Arteriolar tone
Very very small arteries
Small internal radius = some resistance
LOTS of smooth muscle in walls compared to radius
A little constricted at all times
o If fully relaxedcannot vasodilate = cannot increase blood
flow
o Can get 50% more constricted or dilated
o Very common
Regulatory mechanism
Increased or decreased for 2 reasons
o Control of blood flow to capillary beds
Intrinsic control mechanisms (from within organ
itself)
Local factors (chemicals)
o Changing MAP
Extrinsic control mechanisms
ANS and hormones
Autonomic NS
o Control of blood flow is more local, change in BP is more
global
Intrinsic control of BF = distribution of blood to organs
o EXTRINSIC control mechanisms regulate MAP
o INTRINSIC control mechanisms regulate flow of blood
directed to individual capillary beds
Based on metabolic needs of tissues
Decreased demand flow is decreased
Increased demand flow is increased
Locally regulated
find more resources at oneclass.com
find more resources at oneclass.com
Unlock document

This preview shows half of the first page of the document.
Unlock all 2 pages and 3 million more documents.

Already have an account? Log in

Get OneClass Notes+

Unlimited access to class notes and textbook notes.

YearlyBest Value
75% OFF
$8 USD/m
Monthly
$30 USD/m
You will be charged $96 USD upfront and auto renewed at the end of each cycle. You may cancel anytime under Payment Settings. For more information, see our Terms and Privacy.
Payments are encrypted using 256-bit SSL. Powered by Stripe.