Exam 2

• vagal tone


  - without supervision, the sinoatrial node would keep the heart beating at about 100-110 bpm

  - the parasympathetic nervous system has a continual effect through the Vagus nerve which slows it down to about 75 bpm
• vagal escape


  when heart starts racing when it shouldn't be (problem with vagal tone)
• tachycardia

  abnormally high resting (>100 bpm)
• bradycardia

  abnormally low resting heart (<60 bpm except if you're an athlete then it would be normal to be this low)
• congestive heart failure


  umbrella term including anything that causes abnormally low cardiac output

  - coronary atherosclerosis

  - high blood pressure

  - myocardial infarctions

  - dilated cardiomyopathy
• coronary atherosclerosis / CHF

  - coronary arteries clogged from plaque (calcium) deposits

  - stroke volume decreases, decreased amount of O2 delivered to cardiac muscle

  > can't contract like it used to
• high blood pressure / CHF

  heart has to contract with greater force to eject the blood, decreased stroke volume and cardiac output
• myocardial infarction

  - O2 supply to heart is temporarily eliminated

  - permanent loss of contractility

  > lack of O2 converted it to fibrous connective tissue

  - coronary arteries usually the ones that are blocked
• dilated cardiomyopathy

  - too much blood in ventricles for extended period of time

  - flabby ventricles

  - too much stretch over time
• heart tissue composition / embryological development

  - composed of cardiac muscle

  - mesoderm
• heart development

  - originates as two separate tubes of endothelial tissue

  > tubes fuse together into a single chambered heart by day 23

  - day 25: early stages of the 4 chambers form

  - D-looping occurs

  > rightward bending of the heart to flip it upside down

  - chambers continue to develop and separate from each other

  - day 46: heart in orientation it will be at birth
• foramen ovale


  - fetal hole between right and left atria through the interatrial septum

  - shortcut that allows most blood to bypass the pulmonary circuit

  > gaseous exchange occurring at the placenta

  - closes over at birth → fossa ovalis

  
• ductus arteriosus

  - connection between pulmonary artery and aorta

  - blood that didn't go through the foramen ovale winds up in the pulmonary artery and can enter the aorta there

  - seals after birth → ligamentum arteriosum

  
• age-related changes in heart function

  - valve sclerosis

  - decreased cardiac reserve

  - fibrosis of myocardium

  - atherosclerosis
• valve sclerosis


  - deposits (ex. calcium) accumulate on top of raphe/valve flaps (makes them more rigid)

  - the valves lose functionality

  > prevents them from closing all the way

  > backflow of blood occurs

  - decreased cardiac output

  - gradual process (accumulates over time, even now)

  - can be offset by a healthy diet
• decreased cardiac reserve


  - as you age, you lose the ability to have a large cardiac reserve

  - can be somewhat offset by exercise
• fibrosis of myocardium

  - if you fail to use the myocardium, it will begin to atrophy and become non-contractile (fibrous connective) tissue

  - loss of ability to contract of strongly

  - prevention: stay active

  > use it or lose it → so use it!
• atherosclerosis

  - accumulation of plaque (typically cholesterol) along inside of blood vessels

  - reduces diameter of blood vessels → changes bp

  - risk factors: high fat diets, cigarette smoking
• we have a __________ circulatory system

  closed
• arteries


  - carry blood away from heart

  - generally oxygen rich blood (except pulmonary arteries)

  - elastic & muscular
• elastic arteries


  - more proximal to the heart

  - larger diameter

  - low resistance

  - walls rich in elastin (sheets of elastic CT)

  > allows them to rebound and resist to maintain high bp

  - ex: aorta or pulmonary artery
• muscular arteries

  - more distal to the heart

  - smaller diameter

  - branch off elastic arteries and carry blood to organs

  - still have some elastin but not nearly as much

  - have a lot of smooth muscle in their walls
• arterioles


  branches off of muscular arteries and lead to capillary beds
• capillaries

  - branch off of arterioles

  - microscopic blood vessels

  - walls are one cell thick (tunica interna)

  > simple squamous epithelial tissue

  - RBCs have to go through single file (maximizes diffusion)

  - site of gaseous exchange

  > gases diffuse from blood to interstitial space or vice versa based on pressure differences
• venule


  connect capillaries to veins
• veins

  - venules connect to these

  - return blood to the heart (vers le cœur)

  - generally carry oxygen poor blood (except pulmonary vein)

  - more blood here than anywhere else

  - lowest pressure here

  - valves assist blood returning to heart
• lumen


  space/opening in the middle of the vessel that contains the blood (considered an exterior surface)
• tunica interna


  - inner lining which surrounds the lumen

  - composed of simple squamous epithelium

  - cells bind to create a flat, smooth, frictionless surface

  - continuation of cardiac endothelium/endocardium
• tunica media

  - middle layer, deep to tunica interna

  - consists of smooth muscle and elastin

  - thick in arteries, thinner in veins

  - controls blood vessel diameter through sympathetic nervous system

  > these impulses cause vasoconstriction

  > absences of these impulses allow vasodilation

  - chemicals like epinephrine from adrenal medulla also cause vasoconstriction
• tunica externa

  - outermost layer (deepest)

  - made up of collagen and DICT

  - anchors blood vessel in place

  - vasa vasorum found here (if present)
• vasa vasorum


  little blood vessels to vascularize large blood vessels
• continuous capillaries


  - most common

  - simple squamous epithelial

  - endothelial very tightly joined together

  - small intercellular clefts (exchange happens through cells)

  - contain pinocytic vesicles

  
• fenestrated capillaries


  - has pores/holes (fenestrations) to increase permeability

  - found in areas associated with high absorption and filtration rates

  - kidneys, endocrine organs, small intestines, digestive tract

  
• sinusoidal capillaries


  - relatively large openings

  - leakiest capillary

  - large molecules & blood can pass through the walls

  - found in the liver and red bone marrow of bones

  > where blood enters/exits the vasculature

  > liver recyles old blood cells, red bone marrow produces new blood cells

  
• terminal arteriole


  sends blood to capillary bed, can change blood flow by changing its diameter
• metarteriole


  branches off from terminal arteriole
• thoroughfare channel


  becomes postcapillary venule; main middle channel
• postcapillary venule

  thoroughfare channel empties into this and returns blood to the vein
• vascular shunt


  metarteriole & thoroughfare channel; must always be open
• true capillaries

  - branches off arterioles

  - where gas exchange occurs

  - microcirculation regulates amount of blood going through the capillary beds