Ch.20 Blood Vessels 2 Flashcards
Blood viscosity
Resistance to flow (thickness)
Ex: anemia- decreased viscosity-decreased resistance- increased blood flow
Resistance
Amount of friction blood experiences traveling through vessels slowing it down affected by
- blood viscosity
- vessel length
- vessel radius
Vessel length
Increase vessel length link
(example: weight gain)
Increased resistance
Decreased blood flow
Vessel radius
Increased diameter
Decrease resistance
Increase total blood flow
Blood pressure
Force per unit area of blood vessel wall (hydrostatic)
Blood Pressure gradient
Highest in arteries and lowest in veins
Driving force in propelling blood through the vessels
Arterial blood pressure
Pulsing b/c ventricles are contracting systolic P an relaxing diastolic P
average blood pressure
120/80 mmHg
Pulse pressure
Difference between systolic and diastolic blood pressure
(Ex: 180 come backkkk
Pulse
Throbbing sensations associated with pulse pressure
Capillary blood pressure
Pulse pressure and capillaries - 0
-low enough so that not to damage vessels behind
-high enough to ensure capillary exchange
-
Mean arterial pressure (MAP)
Average of blood pressure forces on arteries
MAP= Diastolic pressure + 1/3 post pressure
Ex: ((80*2)+120)/3= 93
MAP<60 insufficient blood flow
Capillary blood pressure at the arterial end is about…
Capillary blood pressure at the venous end is below…
…35mm Hg (filtration)
…16mm Hg (reabsorption)
Venous blood pressure
- venous return
- 20mm Hg in venues =0 reaches right atrium
- small gradient may be insufficient to move blood when standing so moment is facilitated by valves & skeletal muscle & respiratory pumps
Venous return
movement of blood back to the heart
Skeletal muscle pump
Assists movement of blood within the limbs with each muscle contraction while valves help to prevent backflow
Prolonged inactivity leads to blood pooling in leg veins
Respiratory pump
Assist movement of blood from abdominal >
thoracic cavity>
heart (due to action of the diaphragm)
Short-term (neural) regulation of blood pressure
-occurs through autonomic resources
-monitors blood pressure & makes adjustments quickly by altering:
Cardiac output
Resistance (vessel diameter)
Long term (hormonal) regulation of blood pressure
- Occurs through endocrine reflexes
- moniters blood pressure and makes adjustments slowly but altering:
Resistance (vessel diameter) Blood volume (fluid intake or urine output)
Cardiovascular center
Located in medulla
- cardiac center
- vasomotor center
Cardiac center
Regulates heart activity
- cardioacceleratory (sympathetic) center
- cardioinhibitory center
Vasomotor center
Controls the degree of vasoconstriction
- sympathetic pathways
-cardioacceleratory (sympathetic) center
Increase heart rate and force
Increased cardiac output
Increased blood pressure
cardioinhibitory (parasympathetic) center
Decreased heart rate
Decrease cardiac output
Decreased blood pressure
Sympathetic pathways
Extend to various blood vessels
Response will depend on the receptor type located on the vessel:
- alpha receptors
- beta receptors
Alpha receptors
(In most vessels)
Trigger vasoconstriction
Beta receptors
Are present (in most vessels) (cardiac and skeletal muscles) trigger vasodilation
Activation of vasomotor center leads to
A. Due to constriction of many vessels > increased blood pressure
B. Increased circulating blood volume due to the shifting blood from venous reservoirs > increased blood pressure
C. Redistribution of blood flow
Cardiovascular center response is triggered by the information arriving from…
Baroreceptors
&
chemoreceptors
Baroreceptors
Respond to the stretch in the vessel walls
-aortic arch
Carotid Sinus
Aortic Arch
Monitor systematic blood pressure
Carotid sinus
Monitor blood pressure in the head and the neck, more sensitive
Chemoreceptors
(Carotid body & aortic bodies)
Respond to:
Increased CO2,
Decreased pH
Decreased O2
Hypothalamus
Can increase cardiac output & resistance triggered by:
- increased body temperature
- fight or flight response
Limbic system alters
Blood pressure in response to emotions
