BIO 2870 Lecture Notes - Lecture 7: Aponeurosis, Anal Canal, Integumentary System

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23 Aug 2016
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*3 types of muscle skeletal (voluntary…sarcomere), cardiac, smooth
Cardiac Muscle Tissue
-allows heart to function as a pump
-blood is sent to lungs for oxygenation and sent through your body
-Cardiocytes
-7characteristics
-are small
-have a single nucleus
-have short, wide t tubules
-have no triads
-have SR with no terminal cisternae
-are aerobic (high in myoglobin, mitochondria)
-have intercalated disks
-Intercalated Discs
-specialized contact points between cardiocytes
-join cell membranes of adjacent cardiocytes (gap junctions, desmosomes--
structure, physically connect cardiocytes)
-functions of intercalated disks
-maintain structure
-enhance molecular and electrical connections
-conduct action potentials
-coordination of cardiocytes
-link heart cells mechanically, chemically, and electrically, the heart
functions like a single, fused mass of cells (functional synctium)
*entire mass/sheet of cells contract together!
-Four functions of cardiac tissue
1. Automaticity
-contraction w/o neural stimulation
-controlled by pacemaker cells (self-sufficient to initiate action potential)
*initiate and maintain cardiac function
2. Variable contraction tension
-controlled by nervous system
3. Extended contraction time
-ten times as long as skeletal muscle
4. Prevention of wave summation and tetanic contractions by cell membranes
-long refractory period
*twitch here is up to 300 milliseconds
-important so that it doesn’t undergo wave summation
*muscle cells must complete twitch and recovery before the next
muscle contraction can happen
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*Skeletal muscle note: skeletal muscle is able to respond if you give another stimulation
before relaxation. (it can contract again)
-in cardiac muscle you cannot have this. They have to come down all the way
before responding to next stimulation
Smooth Muscle Tissue
-Eight Characteristics
.1) Long, slender, and spindle shaped
.2) Have a single, central nucleus
.3) Have no T tubules, myofibrils, or sarcomeres
.4) Have no tendons or aponeuroses
.5) Have scattered myosin fibers
.6) Myosin fibers have more heads per thick filament
.7) Have thin filaments attached to dense bodies
.8) Dense bodies transmit contractions from cell to cell
*Striations
-Muscle in Body Systems
.Forms around other tissues
.In blood vessels
Regulates blood pressure and flow
In reproductive and glandular systems
Produces movements
In digestive and urinary systems
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