Upgrade to remove ads
PSIO Lecture Exam 3, PowerPoint 23: "Cardiac and Smooth Muscle"
Terms in this set (72)
***The underlying mechanisms in all three muscle types (cardiac, smooth, and skeletal) rely on variations of two common themes:
1. Sliding filaments (actin & myosin)
2. Regulation of cytoplasmic [Ca2+]
What is the function of the cardiac muscle?
The cardiac muscle pumps blood.
Describe how the heart pumps blood.
The cardiac muscle involves contraction of muscle around a confined volume, increasing the pressure so the fluid can be pushed through the circulatory system.
How are cardiac and skeletal muscle related?
Both cardiac and skeletal muscle are striated. Smooth muscle is not!
***For skeletal muscle, where does calcium come from?
In skeletal muscle, calcium comes from ONLY the sarcoplasmic reticulum.
How do the cells of cardiac muscle compare to the cells of skeletal muscle? (2)
In comparison to skeletal muscle cells, cardiac muscles are smaller and are branched.
How does cardiac muscle's T-tubule and SR system compare to skeletal muscle's?
Cardiac muscle has a much less extensive T-tubule and SR system compared to skeletal muscle's.
How are the myofibrils of cardiac muscle organized?
Cardiac muscle's myofibrils are organized into sarcomeres.
Describe the cell-to-cell interactions of cardiac muscle compared to skeletal muscle's.
Cardiac muscle has extensive cell-to-cell interaction.
Describe the cells of cardiac muscle (3).
*Smaller than skeletal muscle
*1 or 2 nuclei
What is the function of T-Tubules?
T-tubules allow electrical signals to travel deep down into the muscle fiber.
How are the T-tubules of cardiac muscle developed? Through what?
The T-tubules of cardiac muscle are developed by pace maker cells through gap junctions.
Why isn't the SR system of cardiac muscle as extensive as that of skeletal muscle?
In skeletal muscle, calcium comes ONLY from the SR, so it needs to be more extensive! For cardiac muscle, though, calcium comes from the SR as well as from outside of the cell, so it doesn't need as extensive of an SR system because it has 2 sources of calcium, while skeletal has only one source.
Cardiac and skeletal muscle are known to have striations. What creates these striations?
Sarcomeres are what create striations in cardiac and skeletal muscles!
Is the sarcomere organization of cardiac muscle the same as the sarcomere organization of skeletal muscle?
Yes! Their sarcomeres are composed of the same elements, are the same.
Why does cardiac muscle have extensive cell-to-cell interactions?
Because electrical signals have to move from one cell to the next and the cells have to be firmly attached for contraction so that they don't separate; they contract together as a whole for an effective pump!
How does the cells of cardiac muscle contract? Why?
The cells of the cardiac muscle have to be firmly attached to one another so that they contract as one big whole, which allows for an effective pump!
What are the functions of intercalated disks (of cardiac muscle)?
Intercalated disks of cardiac muscle help to hold adjacent cells together and transmit the force of contraction from cell to cell.
What are the 2 major substructures of intercalated disks?
How is cardiac muscle functionally similar to skeletal muscle?
Like in skeletal muscle, the sliding filament model also applies for cardiac muscle!
What are 3 major factors of the sliding filament model?
Watch a video explaining this process!
*Ca2+ interaction with thin filament
When it comes to obtaining calcium, how does cardiac muscle differ from skeletal muscle?
Skeletal muscle has an extensive SR system which delivers calcium to the muscle. Cardiac muscle, however, requires calcium to be delivered from both its SR system as well as from outside of the cell!
When is the entry of extracellular calcium required in cardiac muscle?
Entry of extracellular calcium is required on a beat-to-beat basis.
How does the contraction of cardiac muscle differ from that of skeletal muscle?
Skeletal muscle contraction is initiated by an electrical signal sent from the central nervous system. Cardiac muscle contraction, however, is NOT initiated by an electrical signal from the CNS!
What is cardiac autorhythmicity?
Cardiac autorhythmicity refers to the electrical activity of the heart & how the heart contracts rhythmically as a result of APs (action potentials) that it generates by itself.
***Does cardiac muscle get nervous input?
Yes, cardiac muscle can receive nervous input, but it is NOT REQUIRED!
In cardiac muscles, what are electrical and contractile activity initiated by?
Pacemaker cells initiate electrical and contractile activity in cardiac muscle.
The initiation of electrical and contractile activity by pacemaker cells leads to...
Spontaneous generation of APs (action potentials)
If you had a heart in a dish, if you added a couple things to it like APs, what would happen?
The heart would continue to beat!
Without nervous input, what is the intrinsic rate of the heart?
Without nervous input, the heart has an intrinsic rate of 110.
Compare the motor units of cardiac muscle vs. skeletal muscle.
Skeletal muscle has many motor units! Cardiac muscle has NO motor units!
Why doesn't cardiac muscle have motor units?
Cardiac muscle doesn't need motor units because its neuron and all its muscle fibers are innervated by that motor neuron.
So instead of having a motor unit like skeletal muscle has, cardiac muscle instead has...
Motor neuron, which innervates itself and all its muscle fibers.
Describe the process of cardiac muscle's motor neuron.
Every cell contracts with every beat. The electrical signal moves from cell-to-cell through gap junctions.
How does electrical signal move in cardiac muscle?
In cardiac muscle, electrical signal moves from cell to cell through gap junctions.
Where is cardiac muscle found?
Cardiac muscle is only found in the heart.
Is tetanus involved in cardiac muscle contraction?
NO! Every cardiac muscle contraction is a twitch! There's no tetanus whatsoever!
What is a twitch?
A twitch is composed of the latent period, then one single action potential for one contraction, then relaxation, repeat.
What is tetanus?
Tetanus is the addition of action potentials to increase the force of contraction of the muscle.
Every cardiac muscle contraction is a...
How does nervous input affect cardiac muscle?
Nervous input influences the rate & strength of muscle contraction, but nervous input is not REQUIRED for cardiac muscle!
Nervous input influences the rate and strength of contraction. In cardiac muscle, this nervous input acts on what 2 things?
*Acts on pacemaker cells
*Acts on calcium delivery
The nervous system doesn't need to worry about reaching what kind of cells since it already affects/acts on what kind of cells?
There's no need for the nervous system to go to specific cardiac muscle cells; it only affect pacemaker cells!
How does a stronger contraction affect the cardiac muscle?
A stronger contraction allows the heart to pump more of the blood that's inside it, out.
***What kind of twitch is cardiac muscle?
Cardiac muscle is a slow twitch, meaning its contraction is rather slow.
The single twitch of cardiac muscle has a very long time course (100's of millisec). This reflects characteristics of the...
Cardiac action potential.
What is the function of smooth muscle?
The function of smooth muscle is to control diameter of 'tissue tubes' such as that of blood vessels, gut, etc.
Is there only one type of smooth muscle?
No, there are many types of smooth muscle!
What are the 2 common structural features of smooth muscle?
*Smooth muscle has one, small nucleus only.
*Smooth muscle lacks a CLEARLY organized structure.
Does smooth muscle have sarcomeres? Why or why not?
Unlike cardiac and skeletal muscles, smooth muscle does NOT have sarcomeres! This makes sense because smooth muscle is not striated, and sarcomeres cause striations.
Does smooth muscle have voluntary or involuntary muscle contraction?
Smooth muscle has involuntary muscle contraction.
Smooth muscle is organized around what kind of structures?
Smooth muscle is organized around tubular structures.
How do smooth muscle cells look? (2)
Smooth muscle cells are spindle shaped and have one small nucleus.
Does smooth muscle have extensive T-tubule/SR systems?
No, smooth muscle doesn't have extensive T-tubule/SR systems.
If smooth muscle doesn't have extensive T-tubule/SR systems, where does it get its calcium from?
Smooth muscle gets its calcium from outside of the cell to make contraction occur!
What kind of filaments does smooth muscle have, and how are they organized?
Smooth muscle still has thin and thick filaments like cardiac and skeletal muscle do, they're just organized and overlap a little more randomly!
Do crossbridges form in smooth muscle?
Yes, crossbridges form in all 3 muscle types.
Smooth muscle has dense bodies. What are dense bodies?
Smooth muscle's dense bodies act as anchor points for thin filaments.
What is in-between the thin filaments of smooth muscle, and what does this allow for?
In-between the thin filaments of smooth muscle are thick filaments, which overlap with the thin filaments and allow for contraction.
Compare the contraction speed of smooth muscle in comparison to that of cardiac and skeletal muscle.
The contraction speed of smooth muscle is a lot slower than that of cardiac and skeletal muscle.
Describe how smooth muscle looks like when its relaxed vs. what it looks like when it contracts.
When smooth muscle is relaxed, its longer in shape and spindle-shaped. When it contracts, it shortens and kind of twists.
How do you generate more muscle tension? How do you generate less muscle tension?
Generate more muscle tension with more calcium; generate less muscle tension with less calcium.
Is smooth muscle very similar to cardiac and/or skeletal muscle?
No, not really. Cardiac and skeletal are the most similar of the 3. Smooth muscle is very different from them.
What is the key to the generation of tension in smooth muscle?
Like for all 3 muscle types, the regulation of cytoplasmic calcium is still key for the generation of tension in smooth muscle.
While yes, the regulation of cytoplasmic calcium is key for generation of tension in smooth muscle just as in the other 2 muscle types, how does that regulation differ for smooth muscle?
In smooth muscle, Ca2+ DOES NOT interact with regulatory proteins on the thin filament to permit myosin head groups to bind.
Instead of binding to regulatory proteins during the regulation of cytoplasmic calcium, calcium instead binds to what (for smooth muscle tension generation)?
Instead of binding to regulatory proteins, calcium binds to enzymes inside the muscle fiber.
How does calcium binding to enzymes instead of regulatory proteins for the generation of muscle tension affect the thick and thin filaments of smooth muscle?
This causes changes to thick filaments, but not to thin filaments.
For smooth muscle, what does the level of tension reflect?
The level of tension reflects a balance between the number of active and inactive head groups.
Calcium enters smooth muscle through the calcium channel and binds to what enzyme?
Calcium binds to calmodulin enzyme.
Everything happens a lot (slower/faster?) in smooth muscle in comparison to cardiac and skeletal muscle.
Everything happens a lot slower in smooth muscle in comparison to cardiac and skeletal muscle.
For smooth muscle, what is the result of an increase in calcium? (2)
An increase in calcium levels increases the number of active head groups, which therefore increases tension.
In skeletal muscle contraction, what does calcium bind to, and what does this in turn activate?
In skeletal muscle, calcium binds to troponin, which will activate the actin found in thin filaments.
THIS SET IS OFTEN IN FOLDERS WITH...
PSIO 201Lecture 9 02/05/16 : Introductio…
PSIO 201Lecture 10 02/8 &10 /16 : Composition and…
PSIO Lecture Exam 3, PowerPoint 17: "Tissue and Ce…
PSIO 201Lecture 11 02/12 /16 : Bone formation
YOU MIGHT ALSO LIKE...
MCAT Biology | Kaplan Guide
Introduction to Cardiac and Smooth Muscle
12-Ch. 18 Key differences between skeletal and car…
Chapter 10 Anatomy
OTHER SETS BY THIS CREATOR
FTM Exam 2, Week 5 & 6 material
FTM, Exam 1 genetic diseases
FTM, Exam 1, Diseases (not including hereditary)
FTM, Exam 1, Week 1: concepts for review