Presentation on theme: "Arteries AWAY Branch Typically oxygenated.. Capillaries Smallest. Most abundant. – How many?? – Why? Exchange."— Presentation transcript:
Arteries AWAY Branch Typically oxygenated.
Capillaries Smallest. Most abundant. – How many?? – Why? Exchange
Veins TOWARDS Converge. Typically deoxygenated.
3 Layers of the Vascular Wall Tunica interna Tunica media Tunica externa.
Tunica Interna/Intima Lining. Endothelium. Supported by loose CT. Only layer in capillaries.
Tunica Media Primarily smooth muscle plus elastic fibers. Most prominent layer in arteries.
Tunica Media Smooth muscle tone Regulated by: – Metabolites – Hormones – Sympathetic vasomotor neurons.
Vasomotor neurons constantly release NE onto TM smooth muscle. – What does the NE do? – Why have a constant release?
Increased NE release by a vasomotor neuron causes: – Tunica media smooth muscle tone to: – Vessel diameter to: – Resistance to blood flow in the vessel to: – Blood flow thru the vessel to:
This gentleman has fatty plaques in his lower leg arteries. How do you think they affect blood flow? How does that relate to his facial expression? His doctor recommends that the sympathetic nerves to those arteries be cut. Why?
Tunica Externa/Adventitia Primarily collagen Function? Most prominent layer in veins
Elastic Arteries Aorta and major branches. Act as AUXILIARY PUMPS.
Regional distribution Significant layer Muscular Arteries
Smallest. May or may not have an externa. Highly innervated by vasomotor neurons. Arterioles
Regulation of blood pressure and flow. Easy to change the diameter. – How would you do it? – Why would you want to? Arterioles
Capillaries Smallest. Thin walls Billions Function? Almost everywhere.
Continuous capillaries –––––––– Most common and least permeable. No endothelial “holes” Intercellular clefts. Abundant in…
Capillary Blood Pressure Low BP. Why is this good? (Think about the structure of a capillary.)
Venous Blood Pressure Even lower BP. Very small gradient.
What is responsible for venous return? Remaining force imparted by ventricular systole. Gravity. Skeletal muscle pump. Respiratory pump. Venomotor action.
Skeletal Muscle Pump
Respiratory Pump Deep Inspiration Thoracic volume will… Pressure in thoracic cavity will… Pressure in thoracic veins will… Blood flow into thoracic veins and towards the heart will…
Venomotor Tone An increase in sympathetic activity causes: – NE release on the TM of medium/large veins to… – Venous pressure to… – Venous return to…
Controlling MAP Why do we need to control it? Short term Long term
Vasomotor Cardioinhibitory Cardioacceleratory Brain Centers for Short Term MAP Control
Increased vasomotor center activity __creased sympathetic output to arterioles Vaso__________ __creased peripheral resistance __creased blood pressure What about a decrease in vasomotor activity?
Increased cardioacceleratory center activity __creased sympathetic output to heart __creased heart rate and stroke volume __creased cardiac output __creased blood pressure What about a decrease in cardioacceleratory activity?
Increased cardioinhibitory center activity __creased parasympathetic output to heart __creased heart rate __creased cardiac output __creased blood pressure What about a decrease in cardioacceleratory activity?
Baroreceptors signals the cardiac and vasomotor centers via CN IX and X. Frequency of these impulses is proportional to MAP. Cardiac and vasomotor centers adjust their output accordingly.
Demonstrating the Baroreceptor Reflex Take the subject’s radial pulse. Find the carotid pulse point and GENTLY press on it. What will happen to the radial pulse? Why?
Adrenal Medullary Mechanism Release epinephrine (and a small amt of NE) in response to: – Large drops in MAP. – Increases in physical activity. – Stressful situations.
–––––––––– HR SV CO PR BP Adrenal Medullary Mechanism How would activation of the adrenal medulla affect:
Renin-Angiotensin-Aldosterone System Renin Angiotensin II
Indirect Mechanism VasoconstrictionAldosterone &Thirst Antidiuretic hormone Increased TPR Increased BV Increased BP Renin-Angiotensin-Aldosterone System Angiotensin II
In response to a fall in MAP, renin release by the kidney would: In response to a rise in MAP, renin release by the kidney would: Indirect Mechanism Renin-Angiotensin-Aldosterone System
A 25yo woman complains to her doctor of headaches and blurred vision. Her blood pressure is 200/130 mmHg. After the BP has been reduced, investigations are made to find the cause of the problem. It’s discovered that her left renal artery is narrowed. Why would this cause the rise in BP?
Long Term BP Control Achieved by the... Primarily done by altering...
____________ blood volume _________BP Long Term BP Control Large increase in BP ____________ urine formation ____________ urine output
As we go from the aorta to the billions of capillaries, what happens to the total cross- sectional area? What happens to the velocity of blood flow?
As we go from the billions of capillaries to the venae cavae, what happens to the total cross- sectional area? What happens to the velocity of blood flow?
The Paradoxical Problem of the Vasomotor Center
Local Regulation of Blood Flow Autoregulation - adjustment of blood flow to each tissue according to its immediate needs. Surplus or deficiency of local chemicals influences local vessel diameter and blood flow.
Working Muscle Tissue Tissue CO 2 levels ___ Tissue O 2 levels ___ Arterioles serving tissue vaso________ Lactic acid levels ___ ______blood flow to tissue CO 2 _______ Lactic acid _______ Heat _______ O 2 ________ Local Regulation of Blood Flow Tissue temp. ____