module 3: heart and blood vessels

what are intercalated discs? what 2 regions are within the discs?

Intercalated discs are junctions that joint sarcolemma’s together like interlocking fingers, they contain 2 regions:

1. fasciae adherens

2. gap junctions

what is the function of the fasciae adherens within intercalated discs?

desmosome-like junctions: long, strong stitches

• physically bind cells together

• transmit the contractile force to adjacent cells

what is the function of the gap junctions within intercalated discs?

small channels made of connexons

• allow passage of ions between cells: “"cell to cell communication”

Flow of Blood (where is blood oxygenated/deoxygenated)

1. SVC / IVC / Coronary Sinus

2. Right atrium → tricuspid valves

3. Right ventricle → pulmonary semilunar valve

4. Pulmonary trunk / artery

5. Lung / pulmonary capillaries → back to the heart / pulmonary veins

6. Left atrium → mitral / bicuspid valve

7. Left ventricle (strongest chamber) → aortic semilunar valve

8. aorta → body

Arrhythmias: what is tachycardia and bradycardia (include bpm)?

• Tachycardia: heart beats too fast (>100bpm)

• Bradycardia” heart beats too slow (<60bpm)

Arrhythmias (variation from normal heart rhythm): what is atrial fibrillation?

• random signals originating from the AV node

• cause ventricles to contract quickly and irregularly

• can form clots, which can break off, reach the brain, and cause strokes

Arrhythmias (variation from normal heart rhythm): what is ventricular fibrillation? what causes this?

• irregular beats originating w/i the ventricles

• ventricles are unable to pump blood (quivering)

• results in cardiac arrest

what is the conducting system? does it depend on extrinsic nerve impulses?

Conducting system: specialized cardiac muscle cells that carry impulses throughout the heart

• does not depend on extrinsic nerve impulses, functions independently

what is the order of the conducting system pathway (5 components)?

1. SA node

2. AV node

3. AV bundle

4. bundle branches

5. purkinje fiber (subendocardial conducting network)

describe the 3 structures represented on an EKG, what does each represent?

1. P wave: atria contract (depolarize)

2. QRS complex: atria recharge (repolarization not visible, hidden by the spike) and ventricles contract (depolarize)

3. T wave: ventricles relax and recharge (repolarize)

heart sounds: lub-dup sound is made by what?

sound of valves closing

first sound: name and what causes it?

Lub (S1)

• AV valves close (mitral & tricuspid)

• ventricles start to squeeze

second sound: name and what causes it?

Dub (S2)

• semilunar valves (aortic and pulmonary) close

• ventricles begin to relax

what controls heart rate? this can be altered by which 2 extrinsic neural controls?

SA node, sets the hearts inherent rate of contraction

1. Parasympathetic nerves: decreases HR (i.e. rest and digest)

2. Sympathetic nerves: increase HR and strength of contraction (i.e. fight or flight, emotion, exercise)

describe the 3 tunics that form the wall of blood vessels. what is the blood-filled space of a vessel called?

1. Tunica intima (deepest)

• Contains simple squamous epithelium

2. Tunica media (functional layer)

• contains smooth muscle for vasoconstriction and vasodilation

3. Tunica externa

• composed of connective tissue

4. Lumen: contains blood

what are the 3 types of arteries?

1. elastic arteries

2. muscular (distributing) arteries

3. arterioles

Elastic arteries are the largest arteries, they contain a lot of (_) to help (_)?

• a.k.a. conducting arteries because they are the pathway for blood leaving the heart

• High amount of elastin to help soften the surge of blood pressure

Muscular (distributing) arteries

• function??

• structure??

a.k.a named arteries

1. distribute blood to body regions and organs

2. thicker tunica media than elastic arteries

• improved constriction/dilation

Arterioles are known as…?

These can be controlled by an intristic factor like…?

1. Smallest arteries (some only possess smooth muscle)

2. sympathetic NS

• fight-or-flight triggers vasocontraction

• increases BP and makes skin pale

capillaries are the smallest blood vessels, for this reason RBCs pass through in (_). what are 4 site-specific function of capillaries?

• Red blood cells pass through single file

1. Lungs: exchange O2 and CO2

2. Small intestines: receive nutrients

3. Endocrine glands: receive hormones

4. Kidneys: remove nitrogenous wastes

capillaries are the smallest blood vessels, what are the 3 types and their permeability?

1. Continuous: least permeable (most common)

2. Fenestrated: semi-permeable

3. Sinusoidal: most permeable

what 4 locations lack capillaries, meaning they are avascular?

1. epithelium

2. cartilage

3. cornea

4. lens

describe the size of venules. venules join the form what?

• smallest veins

• venules join to form veins

what are 4 key structural differences between veins and arteries?

Arteries // veins

1. Thicker walls // thinner walls

2. Thicker tunica media: more smooth muscle

3. Smaller, round lumens // wide, flattened lumens

4. No valves // have valves

Pulmonary circuit

direction of flow?

1. Heart → lungs

• to oxygenate blood

Systemic circuit

1. Heart → Body (back to heart)

• Oxygenate tissues

Flow of blood through blood vessels. 6 steps, 5 types of blood vessels

1. Heart → arteries

2. Arteries → arterioles

3. arterioles → capillaries

4. capillaries → venules

5. venules → veins

6. veins → heart