Heart + Smooth Muscle

Created by

Adrian Hoffman

Cards (169)

Cardiac Muscle
shorter than skeletal muscle
Cardiac Muscle
Fat
branched
mono - or binucleate
striated
Striated - high levels of organization
(actin / myosin Organizes into sarcomeres)
Intercalated discs connect cardiac cells into branched fibers
many gap functions to communicate
Three types of Myocytes ( cardiac muscle cells)
Pacemaker cells : specialized to initiate heart beat
Conducting myocytes : specialized to send Action potentials quickly
Contracting Myocytes : contract and shorten
Intercalated Discs
wavy , not straight
important for surface area
lots on junction
In Intercalated Discs, there are desmosomes
Desmosomes : lots of collagen ,
hard to pull apart,
very strong and can make flexible
Intercalated Discs
Desmosomes : Hold cardiac muscle cells together, protect gap junction
Gap Junction : located in spots with long axis, reason is for easier communication
Are all cardiac muscle connected?
No
Cardiac Muscle
bunch of cells connected together by gap junctions
If one gap junction spreads and Action potential, all connected muscle will release action potential
Cardiac Muscle Fiber Structure
Sarcolemma : Plasma membrane of muscle cell
T-tubules : Made of membrane, continues with plasma membrane, carries action potential
Sarcoplasmic reticulum : Smooth ER of muscle cell, stores and releases calcium , less organized than skeletal
Myofibrils : Made of sarcomeres - contractile rods
Mitochondria : Makes ATP , A LOT of them
Word Bank
Diad, T-tubules, Mitochondria , Sarcolemma, Myofibrils, Sarcoplasmic reticulum
A) Sarcolemma
B) T-tubules
C) Myofibrils
D) Sarcoplasmic Reticulum
E) Mitochondria
F) Diad
Cardiac Muscle Contraction
Differences between skeletal and cardiac muscle:
Energy Requirements : aerobic respiration and fuel sources
Lots of mitochondria increases oxygen consumption
uses glucose and fats when possible
if needed, can adapt to use other fuels
Cardiac Muscle Contraction
Differences between skeletal and cardiac muscle:
2. The anchor point : what does muscle pull on?
Cardiac muscle has fibrous skeleton
lots of collagen = collagen maintains its shape
Cardiac Muscle Contraction
3. Means of stimulation- automaticity/autorhythmicity
cardiac muscle is intrinsically stimulated
Cardiac Muscle Contraction
4. Action Potential spread - gap junction
Cardiac muscle works synchronously.
Triggers one cell, triggers all connected by gap juction
Cardiac Muscle Contraction
5. Length of the absolute refractory period - heart needs to pump
Longer in cardiac muscle forces relaxation
Allows filling
Action Potentials in Contracting and Conducting Myocytes
2. Plateau Phase - Is due to Ca2+ influx through slow Ca2+ channels. This keeps the cell depolarized because few K+ channels are open
Action Potentials in Contracting and Conducting Myocytes
Depolarization - Due to Na+ influx through fast voltage-gated Na+ channels. Positive feedback cycle rapidly opens many Na+ channels reversing the membrane potential. Channel inactivation ends this phase
Action Potentials in Contracting and Conducting Myocytes
3. Repolarization - due to Ca2+ channels inactivating and K+ channels opening.
This allows K+ efflux, which brings membrane potential back to its resting voltage
Na+ channels open
Na+ channels close
Ca2+ channels open
Slow Ca2+ in. Prolonged depolarization
Ca2+ channels close. K+ channels open
K+ channels flow out
Action Potentials in Contracting and Conducting Myocytes
Much faster depolarization in Cardiac
Time is longer in Cardiac
Cardiac Muscle contraction (Contracting Myocytes)
AP moves along SR. Stimulus triggers influx of Ca2+
Ca2+ activates RYR on SR resulting in Ca2+ released in cytosol
Three ways for Cardiac muscle relaxation (Contracting Myocytes)
Contraction cycle concludes, Ca2+ exported in exhchange for Na+. Also, pump that uses ATP to let Ca2+ out (2 pumps) ( Ca2+ ATPase and Na+ - Ca2+ exchanger)
Cytoplasmic Ca2+ is sequestered in the SR (SERCA Ca2+ pump)
Mitochondria avidly takes up Ca2+
Action Potentials in Pacemaker Cells
Autorhythmic
Never stops working
Action Potentials in Pacemaker Cells
Pacemaker potential
Na+ Influx (Na+ channels open)
Relatively slow point
Relatively slow depolarization to threshold
Action Potentials in Pacemaker Cells
2. Depolarization
Ca2+ influx (channels open. Flow in)
Faster (quick depolarization to peak membrane potential)
Action Potentials in Pacemaker Cells
3. Repolarization
K+ influx (channels open. Flow out)
Action Potentials in Pacemaker Cells
Na+ open
Na+ close. Ca2+ open
Ca2+ close. K+ open
K+ close. Na+ open
Action Potentials in Pacemaker Cells
Pacemaker cells are always active
unstable
Heart - Gross Anatomy
About the size of your fist
Great Vessels : Any vessels carrying blood into an out of heart
Heart - Gross Anatomy
Apex of heart - Hits into wall cage
Apical impulse - Where apex of heart hits
Pericardium
direct irregular connective tissue
Protects + anchors heart in place
Prevents overfilling (fibrous)
Provides friction free environment (serous)
Pericardium
Between the Parietal and Visceral, there is a space filled with fluid
Fluid is there to make sure that the epithelial tissue can slide pase one another without problem
The Pericardium
A) Fibrous
B) Parietal
C) Visceral
D) Fluid
Layers of the Heart Wall
Epicardium - connective tissue binds to muscle underneath. Fused to it
A) Epicardium
B) Myocardium
Cardiac Muscle Bundles
Lots of Collagen (some elastic fibers)
anchors cardiac muscle
drives pattern of contraction
anchors valves and great vessels to heart
Endocardium
Simple squamous epithelial lining
At great vessels, continuous with endothelial vessels
Impermeable to O2
Pathway of Blood through the Heart
Superior / Inferior Vena Cava
Right atrium
Tricuspid value
Right ventricle
Pulmonary Semilunar valve
Pulmonary trunk / arteries
LUNGS
Pulmonary veins
Left atrium
bicuspid value
Left ventricle
Aortic semilunar valve
Aorta
BODY
(Rinse and Repeat)