Study Guide K (test 2)

Is there enough blood to fill all capillaries?

no

Where must blood be delivered?

to organs and tissues where it is most needed and away from areas where it is not

What is local blood flow?

the blood delivery locally to the capillaries of a specific tissue and is measured in milliliters per minute

What is perfusion?

specific amount of blood entering capillaries per unit per gram of tissue

What is the degree of vascularization?

extent of blood vessel distribution within a tissue = the potential ability of blood delivery

What are some tissues that are well vascularized?

the brain, skeletal muscle, heart, liver

What are some tissues that are poorly vascularized?

tendons, ligaments

What are some tissues that are avascular?

mature cartilage, epithelial tissue

What is angiogenesis?

formation of new blood vessels in tissues that require them

Why is angiogenesis an active area of cancer reasearch?

to try and deprive it of oxygen and nutrients needed for growth

What is the myogenic response?

the contraction and relaxation of smooth tissue within blood vessels in response to changes in stretch of the blood vessel wall

What is the myogenic response to increase in blood pressure?

additional volume of blood to enter the blood vessel = increase in stretch of wall vasoconstriction

What is the myogenic response to decrease in blood pressure?

causes lower blood volume to enter blood vessel = decrease in stretch of wall = vasodilation

What are vasodilators?

substances that cause smooth muscle relaxation

• which results in both vasodilation of arteriole and opening of precapillary sphincters

What are vasoconstrictors?

substances that cause smooth muscle contraction

• both arterioles vasoconstriction and precapillary sphincters closing

= blood flow decreases into a capillary bed

What is autoregulation?

a tissue regulates or controls its local blood flow in response to its changing metabolic needs

What are some local substances that lead to vasodilation?

increase in CO2, lactate, H+, K+

What are some that lead to vasoconstriction?

decrease in CO2, lactate, H+, K+

What is an example of reactive hyperemia?

entering a warm room after being outside in the cold and your checks turn bright red

due to the increased blood flow in the dermis and the normal blood flow in the skin resumes

What is the role of histamine?

inflammatory mediators

response to trauma, allergic reaction, infection exercise → cause vasodilation

What are Local substances of vasodilators?

decreased oxygen levels

decreased nutrient levels

increased CO2, H+, K+, lactate levels

histamine, bradykinin, Nitric oxide, prostaglandins

What are hormones and neurotransmitters of Vasodilators?

ANP, EPI

What are Local substances of Vasocontrictors’’?

increased O2 levels

increased nutrient levels

Decreased CO2, H+, K+, lactate levels

leukotrienes, thromboxanes, endothelins

What are hormones and neurotransmitters of Vasoconstrictors?

Angiotensin II, aldosterone, ADH, Norepinephrine

Maintaining local blood flow depends on having _________ _________ blood flow

adequate total

What is total blood flow?

the amount of blood transported throughout the entire vasculature in a given period of time

What does total blood equal?

Cardiac output

What is blood pressure?

force per unit area that blood exerts against the inside wall of a vessel

What is the driving force that propels blood through the vessels?

blood pressure gradient

Why is blood flow pulsatile in arteries?

consequence of the ventricles contracting and relaxing

What is the systolic pressure?

contraction = max stretch

What is diastolic pressure?

relaxation = no more stretch

The average blood pressure is 201/80 mm Hg, what does each number represent?

201= systolic ( pulse pressure)

80= diastolic ( mean arterial pressure)

What is pulse pressure?

the additional pressure placed on the arteries from when the heart is resting to when its contracting

How is pulse pressure calculated?

difference btwn systolic ad diastolic

What is a pulse?

a rhythmic throbbing of an arterial wall as blood is being pumped through the vessel

How is a pulse detected?

across the body where an artery may be compressed against a bone or solid structure

What is the mean arterial pressure?

average of blood pressure on the arteries

How is the mean arterial pressure estimated?

diastolic pressure + 1/3 pulse pressure

Is the flow in capillaries pulsatile?

no

How does the blood pressure at the beginning of a capillary compare to the flow at the end of the capillary?

higher BP = filtration of arterial end abt 40

low BP = reabsorption of venous end below 20

Can you take a pulse using a vein?  Why or why not?

no b/c blood is far removed from the pumping action of the heart

 

What are the two “pumps” that aid in the venous return of blood? 

1. Skeletal muscle pump

2. Respiratory pump

How does the Skeletal muscle pump work?

as skeletal muscles contract veins are squeezed to help propel blood toward the heart and valves prevent blood backflow

How does the Respiratory pump work?

inhale: diaphragm contracts and flattens, intra-abdominal pressure increases and places pressure on the vessels within the abdominal cavity as the thoracic cavity volume increases and intrathoracic pressure decreases and blood is propelled from vessels in abdominopelvic cavity into the vessels in the thoracic cavity

exhale: diaphragm relaxes and returns to its dome shape, thoracic cavity volume decreases and intrathoracic pressure increases which places pressure on vessels within the thoracic cavity. Blood moves from the vessels in the thoracic cavity back into the heart. As intra-abdominal pressure decreases allows blood to move from the lower limbs into the abdominal vessels

What are varicose veins?

dilated and tortuous

valves in these veins have become dysfunctional causing blood to pool to one area and the vein begins to swell and bulge

What structure in veins are nonfunctional in varicose veins?

valves

What is resistance? 

amount of friction the blood experiences as it is transported through the blood vessels

How does resistance influence blood flow?

determines how fast or slow blood flows

What are three factors that impact peripheral resistance?

blood viscosity, blood vessel length, size of lumen blood vessels

What is viscosity?  

resistance of fluid to its flow → “thickness” of a fluid

thicker the fluid = more viscous = greater its resistance to flow

thinner the fluid = less viscous = less resistance to flow

How does an increased viscosity impact resistance?

causes greater its resistance to flow

How does a decreased viscosity impact resistance? 

causes less resistance to flow

What examples of anemia?

a lower than normal number of RBC and blood has less resistance to flow

What are examples of dehydration?

greater than normal RBC and blood has more resistance to flow

How does increasing vessel length impact resistance? 

Describe an example of this.

longer vessels result in greater friction

ex: when a person gains a large amount of wright the body must produce miles of additional vessel length by angiogenesis for blood to be transported thus vessel resistance increases

What is the major way resistance is regulated by the body?

vessel radius

Write an equation to relate blood flow and the blood vessel radius.

f ~ r^4

(flow) ~ (radius)

Why does vasodilation and vasoconstriction have such a dramatic impact on blood flow?

dilation = greater flow

constriction = less flow

What is the equation for total blood flow? 

flow ~ (P1-P2)/R

How is the blood pressure gradient related to blood flow? 

directly proportional

What would lead to an increased blood pressure gradient flow? 

increase total blood flow

What would lead to decreased blood pressure flow?

decrease blood flow

How is resistance related to blood flow? 

inversely related

How would increased resistance impact flow? 

decrease in blood flow

How would decreased resistance impact flow?

increase in blood flow

Explain why individuals with significant weight gain or atherosclerosis often have high blood pressure.

because a greater pressure gradient must be produced to overcome the higher resistance and ensure normal blood flow and adequate perfusion of all tissues

Why is it important to regulate blood pressure?

to maintain homeostasis

What part of the brain contains nuclei for ANS reflexes that regulate BP?

medulla oblongata

The cardioacceleratory center is associated with which ANS division?

sympathetic nervous system

What neurotransmitter does the cardioaccelerator center release? 

norepinephrine

How does impact HR? 

increases HR

How does impact stroke volume?

increases SV

What is impact on CO?

greater CO

The cardioinhibitory center is associated with which ANS division? 

parasympathetic nervous system

What neurotransmitter does the cardioinhibitory center release? 

acetylcholine

How does impact HR?

decrease HR

How does impact CO?

decreases CO

What is regulated by the vasomotor center?

degree of vasoconstriction and vasodilation of blood vessels

Do blood vessels have dual innervation?  Explain.

no b/c only innervated by sympathetic division w/no innervation by parasympathetic division

What ANS division innervates blood vessels?

sympathetic division

When the SNS (and adrenal medulla) is activated how is Peripheral Resistance, circulating blood volume, and blood flow impacted?

increased PR, larger circulating BV, redistribution of blood flow

A barometer measures atmospheric pressure, a baroreceptor detects pressure where?

stretch of the blood vessel wall

Name two locations where baroreceptors are found.

aortic arch and carotid sinuses

Baroreceptors send signals to the ________________ _____________ in the ____________ ________________

cardiovascular center

medulla oblongata.

What are the ANS reflexes that involve blood pressure regulation?

baroreceptor reflexes

If BP decreases:

1.  _______ stretch in aorta + carotid sinus

2.  _______ signals sent to cardiovascular center

3.  _________ sympathetic signals to heart; __________ parasympathetic.  HR & SV __________. CO _________.

4.  ___________ sympathetic signals to blood vessels.  Vasoconstriction __________.  PR ____________. 

5. BP _____________ as a result.

1. less

2. fewer

3. increase, decrease, increase, increases

4. increase, increases, increases

5. increase

If BP increases:

1.  ______ stretch in aorta + carotid sinus

2.  ______ signals sent to cardiovascular center

3.  ___________  sympathetic signals to heart; ____________ parasympathetic.  HR, SV, CO _________.

4.  ___________ sympathetic signals to blood vessels.  Vasodilation _____________.  PR ____________.

BP ____________ as a result.

1. increase

2. increase

3. decreases, increases, decrease

4. decrease, decrease, decrease

5. decrease

Where are chemoreceptors located? 

What do they detect?

located: within the brain

detect: chemicals in fluids

Why would high CO2, and low oxygen levels stimulate vasoconstriction?

the levels would stimulate chemoreceptors and their increased firing would stimulate vasomotor center = constriction in this case to decrease the levels and return to homeostasis

The medulla has reflexes that regulate quick changes in BP.  Other parts of the brain are involved as well.  Give some examples.

increase in body temp, flight or fight result in hypothalamus increasing CO and resistance

anxiety = increase BP

limbic system = alters blood pressure in response to emotions or emotional memories

What are the three effects of angiotensin II. 

vasoconstriction, stimulating thirst center, decreasing urine formation

How does aldosterone help maintain blood volume and blood pressure?

increasing absorption of Na+ and water in kidney

How does ADH help maintain blood volume and blood pressure?

increases absorption of water in kidney decreasing its loss in the urine

What is the source of ANP?

atrium

What is its stimulus for release?

stretch of the atrial walls due to increased BV and venous return

What is the effect of ANP?

stimulates vasodilation = decreases peripheral resistance

increase urine output = decreases BV

What are the three primary variables that influence blood pressure?

CO, resistance, BV

What instrument is used to measure BP?

sphygmomanometer

What is hypertension? 

chronically elevated blood pressure