Lecture 3 Flashcards
What are the three types of vertebrate muscle?
Skeletal, cardiac, and smooth
What types of movements are in each type of muscle?
Skeletal-voluntary (running, playing piano), some involuntary (breathing)
Cardiac-involuntary (beating of heart)
Smooth-involuntary (movement of internal organs)
What are the cells called of muscles?
Muscle fibers
What is a trait of muscle fibers?
Excitable (general action potential like neurons)
What is a trait of muscle fibers?
Excitable (general action potential like neurons)
What is the structure of cardiac muscle?
Cells electrically coupled, tightly joined to one another
What is the structure of smooth muscle?
Cells arranged in sheets in internal organs
What is the structure of skeletal muscle?
Long cells, striped structure like in cardiac (remember! striations)
What are striations?
The lines in the structure of skeletal muscle and cardiac muscle
What is the breakdown of the structure of skeletal muscle?
Muscle -> Bundle of muscle fibers -> Smaller bundle of muscle fibers (connective tissue) -> single muscle fiber (cell but long and multinucleate) -> myofibrils
What is significant about muscle fibers?
Large and multinucleate
What are muscle fibers bundled by?
Connective tissue
What are myofibrils?
highly organized assemblages of myosin and actin filaments
What is one muscle fiber made of?
Many myofibrils
What are the contractile proteins in skeletal muscles?
Actin and myosin
What is actin?
A contractile protein, thin filament
What is myosin?
A contractile protein, thick filament
How are actin and myosin arranged?
Lie in parallel and slide past each other during contraction
What do actin and myosin form?
Sarcomeres
What do actin and myosin form?
Sarcomeres
What do multiple sarcomeres form?
A single myofibril
What is the Z line?
Where actin is connected
What is the M band?
The middle, myosin is attached here
What is titin?
A protein that runs from Z line to Z line
What is the A band?
from myosin to myosin
What is the H zone?
only myosin
What is the I band?
only actin
What happens to actin and myosin during muscle contraction?
They slide against each other
Who founded the muscle contraction model?
Hugh Huxley and Andrew Huxley simultaneously discovered the model in Cambridge; did not know each other
What happens to a sarcomere when a muscle contracts?
It gets smaller
What happens to a sarcomere when a muscle relaxes?
It gets larger
What happens to a sarcomere when a muscle relaxes?
It gets larger
Which lines stay the same when a muscle contracts or relaxes?
M band, A band
Which lines get smaller when a muscle contracts or relaxes?
Z to Z, I band, H zone
Which lines get smaller when a muscle contracts or relaxes?
Z to Z, I band, H zone
What does sarcomere length determine?
Force
What determines force of a muscle?
Sarcomere length
What happens when actin and myosin are fully contracted?
No more space for shortening
What happens when actin and myosin are fully stretched?
Less force, hard to pass each other
What happens when actin and myosin are fully stretched?
Less force, hard to pass each other
How does the peripheral nervous system send things to the CNS?
Afferent/sensory neurons
How does the CNS send things to the peripheral nervous system?
Effector/motor neurons which can be voluntary (skeletal muscle) and autonomic/involuntary (cardiac, smooth muscle)
How does the CNS send things to the peripheral nervous system?
Effector/motor neurons which can be voluntary (skeletal muscle) and autonomic/involuntary (cardiac, smooth muscle)
What is autonomic?
Involuntary
Where does skeletal muscle contraction start?
At the motor neuron
Where does skeletal muscle contraction start?
At the motor neuron
What is the process of skeletal muscle contraction?
Motor neuron makes contact with muscle cell (neuromuscular junction) –> AP arrives from motor neuron spread across muscle fiber membrane –> travels inside cell to reach myofibrils –> Actin and myosin can contract/pass each other in response to signals
What is the process of skeletal muscle contraction?
Motor neuron makes contact with muscle cell (neuromuscular junction) –> AP arrives from motor neuron spread across muscle fiber membrane –> travels inside cell to reach myofibrils –> Actin and myosin can contract/pass each other in response to signals
What is a motor unit?
One motor neuron and all the muscle fibers it synapses with
What is the presynaptic cell?
Motor neuron
What is the neuromuscular junction?
Junction between motor neuron and muscle cell membrane
What are the neurotransmitters in muscle contraction?
Acetylcholine
What are acetylcholine molecules?
Neurotransmitters in muscle contraction
Where are acetylcholine molecules in muscle contraction?
In vesicles in the motor neuron
What does the axon terminal do?
Releases acetylcholine
What does the axon terminal do?
Releases acetylcholine
What does acetylcholine do once released from the axon terminal?
Binds to receptors on the muscle cells
What happens when acetylcholine binds to receptors on the muscle cells?
Na+ enters the muscle cells, changing membrane potential and triggering more Na+ ion channels to open –> AP
What is the postsynaptic cell?
Motor end plate of muscle cell
What is the postsynaptic cell?
Motor end plate of muscle cell
What spreads the AP into the muscle fiber?
T Tubules, sarcoplasmic reticulum
What is sarcoplasmic reticulum?
Membrane-like structure that helps spread AP in muscle fiber; stores Ca2+ (Calcium pump on the membrane of the reticulum keeps sucking Ca2+ into the reticulum)
What does the AP in T Tubules affect?
DHP and ryanodine receptors on the sarcoplasmic reticulum
What is sarcoplasmic reticulum?
Membrane-like structure that helps spread AP in muscle fiber; stores Ca2+ (Calcium pump on the membrane of the reticulum keeps sucking Ca2+ into the reticulum–leak channel?)
What does the AP in T Tubules affect?
DHP and ryanodine receptors on the sarcoplasmic reticulum
What happens once the DHP and ryanodine receptors are affected on the sarcoplasmic reticulum?
The proteins change shape and no longer connect, thus causing Ca2+ to be released from the reticulum to the outside, spreading eventually to actin and myosin.
What happens once the DHP and ryanodine receptors are affected on the sarcoplasmic reticulum?
The proteins change shape and no longer connect, thus causing Ca2+ to be released from the reticulum to the outside, spreading eventually to actin and myosin.
What does the sarcoplasmic reticulum release Ca2+ into?
The sarcoplasm (muscle fiber cytoplasm)
What does the sarcoplasmic reticulum release Ca2+ into?
The sarcoplasm (muscle fiber cytoplasm)
What receptors are in the sarcoplasmic reticulum?
DHP and ryanodine receptors
What does a Ca2+ increase in the sarcoplasm initiate?
Myofibril to contract
What does myofibril contraction depend on?
Structures of actin and myosin filaments
What is actin made of?
The actin monomer, tropomyosin, and troponin
What does myofibril contraction depend on for skeletal muscle?
Structures of actin and myosin filaments
What is actin made of?
Proteins: actin monomer, tropomyosin, and troponin
What is the actin monomer?
The bead structure
2 together forms an actin polymer
What is tropomyosin?
A protein that is a long strand, covers certain points on actin (the orange dots that are the myosin-binding sites)
What is troponin?
a protein that has 3 subunits: 1 binds to tropomyosin, 1 binds to actin, and 1 that’s a linker
What is myosin made of?
Many heads sticking out in different positions; not as smooth as actin; kind of like golf clubs
A linear polypeptide chain and a globular head
What does a globular head do for skeletal muscles?
Binds to orange dots on actin
What does a globular head do for skeletal muscles?
Binds to orange dots on actin
What does ATP stand for?
Adenosine triphosphate
What process yields free energy?
Hydrolysis of ATP
What is hydrolysis of ATP?
ATP + H20 –> ADP + Pi + energy
What is hydrolysis of ATP?
ATP + H20 –> ADP + Pi + energy
What is adenosine?
adenine and ribose
What do we need for muscle contraction in the skeletal muscle?
ATP, Ca2+, and proper structure of actin and myosin
What do we need for muscle contraction in the skeletal muscle?
ATP, Ca2+, and proper structure of actin and myosin
What are the steps of muscle contraction specifically in actin and myosin?
- Ca2+ binds to troponin –> causes a change in conformation of troponin and twisting of tropomyosin –> exposure of myosin-binding sites on actin
What are the steps of muscle contraction specifically in actin and myosin for skeletal muscle?
- Ca2+ binds to troponin –> causes a change in conformation of troponin and twisting of tropomyosin –> exposure of myosin-binding sites on actin
- Myosin head now attaches to actin molecule causing a cross-bridge.
- The phosphate group falls off the myosin head, leaving only ADP on the myosin, causing a large change in myosin conformation called the power stroke (when the filaments slide past one another)
What are the steps of muscle contraction specifically in actin and myosin for skeletal muscle?
- Ca2+ binds to troponin –> causes a change in conformation of troponin and twisting of tropomyosin –> exposure of myosin-binding sites on actin
- Myosin head now attaches to actin molecule causing a cross-bridge.
- The phosphate group falls off the myosin head, leaving only ADP on the myosin, causing a large change in myosin conformation called the power stroke (when the filaments slide past one another)
- ATP binds to myosin head in exchange for ADP, causing myosin to release from actin.
- Myosin head returns to resting position, Ca2+ falls off, muscle relaxes
What are the steps of muscle contraction specifically in actin and myosin for skeletal muscle?
- Ca2+ binds to troponin –> causes a change in conformation of troponin and twisting of tropomyosin –> exposure of myosin-binding sites on actin
- Myosin head now attaches to actin molecule causing a cross-bridge.
- The phosphate group falls off the myosin head, leaving only ADP on the myosin, causing a large change in myosin conformation called the power stroke (when the filaments slide past one another)
- ATP binds to myosin head in exchange for ADP, causing myosin to release from actin.
- Myosin head returns to resting position, Ca2+ falls off, muscle relaxes
Why do you get stiff when you die?
Because your muscles all contract since there is no more ATP to allow for detachment–all muscle fibers stay contracted
Why do you get stiff when you die?
Because your muscles all contract since there is no more ATP to allow for detachment–all muscle fibers stay contracted
What is the path of action potential?
Motor neuron to muscle fiber to T Tubule to sarcoplasmic reticulum
What are three systems for muscle ATP supply?
Immediate system, glycolytic system, and oxidative system
What does the immediate system use?
Preformed ATP and creatine phosphate; storage is low
What is involved in the glycolytic system?
Glucose, fast metabolism of carbohydrates, fewer ATPs (not a sufficient amount)
What is involved in the oxidative system?
Slow metabolism of carbohydrates and fats; more ATPs because of complete burning of the fuel; depends on mitochondria and oxygen (fuel gets into mitochondria, generates ATP, ATP comes out)
What are the differences in the systems of ATP supply for muscles?
Immediate system drops quickly. Glycolytic builds and peaks at 30 seconds. Oxidative peaks after 1 minute but lasts much longer, can keep going
What are slow-twitch muscle fibers?
Oxidative or red muscle (e.g., soleus muscle)
What do slow-twitch muscle fibers contain?
Myoglobin (oxygen binding protein: allows binding to oxygen for oxygen storage), many mitochondria and blood vessels
What are slow-twitch muscle fibers?
Oxidative or red muscle (e.g., soleus muscle)
What do slow-twitch muscle fibers contain?
Myoglobin (oxygen binding protein: allows binding to oxygen for oxygen storage), many mitochondria and blood vessels
What is the maximum tension for slow-twitch fibers and what’s the rate of development?
low maximum tension, develops slowly
What is slow-twitch fiber highly resistant to?
Fatigue
What are slow-twitch fibers good for?
Aerobic work that requires endurance because it uses the oxidative system
What do slow-twitch muscle fibers contain?
Myoglobin (oxygen binding protein: allows binding to oxygen for oxygen storage), many mitochondria and blood vessels –> looks darker
What are slow-twitch fibers good for?
Aerobic work that requires endurance because it uses the oxidative system
What are slow-twitch fibers good for?
Aerobic work that requires endurance because it uses the oxidative system
What kinds of cells or fibers use the immediate system?
All of them
What are fast-twitch fibers?
Glycolytic or white muscle (e.g., biceps)
What are fast-twitch fibers?
Glycolytic or white muscle (e.g., biceps)
What does fast-twitch fibers have?
Fewer mitochondria and blood vessels –> glycolytic system (less ATP but faster)
What are slow-twitch fibers good for?
Aerobic work that requires endurance because it uses the oxidative system (running)
What does fast-twitch fibers have?
Fewer mitochondria and blood vessels, little or no myoglobin –> glycolytic system (less ATP but faster)
What is myoglobin?
Oxygen binding protein
What are the advantage and disadvantage of fast-twitch fibers?
Develop greater maximum tension faster (fast ATP), but fatigue more quickly (less ATP)
What are fast-twitch fibers good for?
Short-term work that requires maximum strength (weight lifter, sprinter)
What are fast-twitch fibers good for?
Short-term work that requires maximum strength (weight lifter, sprinter) aka anaerobic exercise
What are fast-twitch fibers good for?
Short-term work that requires maximum strength (weight lifter, sprinter) aka anaerobic exercise
What does exercise increase?
Muscle strength and endurance
How does exercise increase muscle strength and endurance (2 ways)?
Through anaerobic and aerobic exercise
How does anaerobic exercise help?
Increases strength by inducing formation of new actin and myosin filaments
Tears muscle –> feedback response requires body to make more actin and myosin fibers –> muscle cells become bigger –> generate more force
No more muscle cells are created here.
Weight lifting
How does aerobic exercise help?
Enhances endurance by increasing oxidative capacity (more mitochondria, blood vessels, myoglobin).
How does aerobic exercise help?
Enhances endurance by increasing oxidative capacity (more mitochondria, blood vessels, myoglobin).
Muscle cells have more mitochondria and blood vessels generated –> enhance oxygen phosphorylation capacity.
Running
How does aerobic exercise help?
Enhances endurance by increasing oxidative capacity (more mitochondria, blood vessels, myoglobin).
Muscle cells have more mitochondria, blood vessels, and myoglobin generated –> enhance oxygen phosphorylation capacity.
Running
How does aerobic exercise help?
Enhances endurance by increasing oxidative capacity (more mitochondria, blood vessels, myoglobin).
Muscle cells have more mitochondria, blood vessels, and myoglobin generated –> enhance oxygen phosphorylation capacity.
Running
What do cells form in cardiac muscle?
A strong meshwork
What is the structure of cardiac muscle?
Cells electrically coupled, tightly joined to one another, striated, smaller cells than skeletal, uninucleated, branch and intercalate (for mechanical adhesion and coupling)
What do cells form in cardiac muscle?
A strong meshwork
What does intercalated structure mean and what is this for?
Enables cells to couple better. Cardiac muscle
What are characteristics of cardiac muscle?
Strong, resistant to tearing, withstand high pressures
What are characteristics of cardiac muscle?
Strong, resistant to tearing, withstand high pressures, AP spreads fast
What is a heartbeat?
Myogenic (generates AP itself, unlike the skeletal muscle that depends on the CNS to send signals)
What can heart muscle be modified by?
Autonomic nervous system (CNS)
What is the structure of smooth muscle?
Cells arranged in sheets in internal organs; long, spindle shaped, uninucleated, no striated but “smooth” look
What are characteristics of cardiac muscle?
Strong, resistant to tearing, withstand high pressures, AP spreads fast because of intercalated structure
What can heart muscle be modified by?
Autonomic nervous system (CNS)
What are characteristics of smooth muscle?
AP in one cell can be spread to all others in the sheet (not as fast as with cardiac but still fast)
Provides contractile force for most internal organs
How is AP generated for smooth muscle cells?
It is induced by stretch
What is different about AP generation in smooth vs cardiac vs skeletal?
Stretch is the stimulus for smooth. Cardiac-itself. Skeletal-motor neurons
What is different about AP generation in smooth vs cardiac vs skeletal?
Stretch is the stimulus for smooth. Cardiac-itself. Skeletal-motor neurons
What do stretched cells do in smooth muscle cells?
Depolarize and fire action potentials which start contraction
What do stretched cells do in smooth muscle cells?
Depolarize and fire action potentials which start contraction
What is stretch important for?
Moving food through the digestive tract
What is different about AP generation in smooth vs cardiac vs skeletal?
Stretch is the stimulus for smooth. Cardiac-itself. Skeletal-motor neurons
Skeletal and cardiac: Ca2+ binds to troponin on actin.
Smooth: Ca2+ modifies enzyme myosin kinase –> adds phosphate group to myosin head (phosphorylate) –> bends myosin
What is stretch important for?
Moving food through the digestive tract
What is stretch important for?
Moving food through the digestive tract
What is the important difference between smooth and cardiac/skeletal muscle contraction?
In smooth, actin doesn’t have tropomyosin or troponin. So, sides are constantly exposed for myosin to bind to. However, it won’t bend or have a power stroke unless the head is phosphorylated by an enzyme (myosin kinase) activated by Ca2+.
What is the important difference between smooth and cardiac/skeletal muscle contraction?
In smooth, actin doesn’t have tropomyosin or troponin. So, sides are constantly exposed for myosin to bind to. However, it won’t bend or have a power stroke unless the head is phosphorylated by an enzyme (myosin kinase) activated by Ca2+.
What are the steps of smooth muscle contraction?
Stretch –> AP –> Ca2+ released from sarcoplasmic reticulum –> modify myosin kinase –> phosphorylate myosin head (add phosphate) –> bind to actin
What are the steps of smooth muscle contraction?
Stretch –> AP –> Ca2+ released from sarcoplasmic reticulum –> modify myosin kinase –> phosphorylate myosin head (add phosphate) –> bind to actin
How does the neural system modify cardiac and smooth muscle contraction?
Autonomic/involuntary nervous system –> sympathetic and parasympathetic divisions
What is the sympathetic division of the autonomic nervous system?
norepinephrine –> accelerate heart rate, inhibit smooth muscle (fight or flight)
What is the parasympathetic division of the autonomic nervous system?
acetylcholine –> inhibit heart rate, stimulate smooth muscle
What is the parasympathetic division of the autonomic nervous system?
acetylcholine –> inhibit heart rate, stimulate smooth muscle
also in skeletal system in AP generation! acetylcholine is a stimulating effect
What is the parasympathetic division of the autonomic nervous system?
acetylcholine –> inhibit heart rate, stimulate smooth muscle
also in skeletal system in AP generation! acetylcholine is a stimulating effect
What are the two different neurotransmitters that modify cardiac and smooth muscle contraction?
norepinephrine (accelerate heart rate and inhibit smooth muscle) and acetylcholine (inhibit heart rate and stimulate smooth muscle–stimulates skeletal muscle as well)
What can you do in an experiment to see how neurotransmitters affect smooth muscle cells?
Stimulation from neurotransmitters of the autonomic nervous system induce contractions in the smooth muscles of the gut – measure muscle contractions (or the force of it–increases-> muscle contracts; decreases -> muscle relaxes) and electrodes (membrane potential)
What can you do in an experiment to see how neurotransmitters affect smooth muscle cells?
Stimulation from neurotransmitters of the autonomic nervous system induce contractions in the smooth muscles of the gut – measure muscle contractions (or the force of it–increases-> muscle contracts; decreases -> muscle relaxes) and electrodes (membrane potential)
Smooth muscle differs from both cardiac and skeletal muscle in that
Depolarization and action potentials are initiated by stretch
What are the 3 types of skeletal systems?
Hydrostatic skeleton, exoskeleton, endoskeleton
What is a hydrostatic skeleton?
Where the liquid (water) inside the body works with muscle contracting or relaxing to provide movement forces (it provides a force to move forward)
Ex. worm
What is an exoskeleton?
Skeleton outside of the body
Ex. insects (grasshoppers), crabs
What are the advantages and disadvantages of exoskeletons?
Good at protecting you but so rigid that you must release it and grow a new layer if you have growth (at this time, you can become very vulnerable for attacks)
What is an endoskeleton?
Skeleton is inside the system and other things are attached to it.
What is the benefit of an endoskeleton?
Provides support (not as much as with exoskeleton but provides our bones and body to grow together)
How many bones are there in the human endoskeleton?
206 bones
What do bones contain?
Collagen fibers and calcium phosphate
What do bones contain?
Collagen fibers and calcium phosphate (deposited in calcium fibers)
Where is cartilage located and what are its characteristics?
On surfaces of bone joints; ears, nose, and larynx (air)
Stiff and resilient, flexible, reduces bone clashes
Where is cartilage located and what are its characteristics?
On surfaces of bone joints; ears, nose, and larynx (air)
Stiff and resilient, flexible, reduces bone clashes
What are some characteristics of bone cells?
not stiff, constantly remodeling, storage of calcium is important
What do bones contain?
Collagen fibers and calcium phosphate (deposited in bone matrix)
What are some characteristics of bone cells?
not stiff, constantly remodeling, storage of calcium is important -keeps Ca2+ storage to maintain homeostasis of Ca2+
Where does calcium phosphate deposit?
In the bone matrix
What are osteoblasts?
Fresh new bone cells
What are osteocytes?
Inside the matrix; one type of bone cell; has very thick extracellular matrix (–> connective tissue has very sensitive extracellular matrix with collagen fibers)
What are osteoclasts?
Little digger cells–constantly digs bones and recycles materials–osteoblasts follow and lay new bone structure–secrete extracellular matrix; calcium phosphate gets deposited in extracellular matrix (remodeling of the bone)
How do bone cells coordinate?
Stress on bones provides information to cells; triggers coordination of cells
What happens to astronauts’ bones in long periods of zero gravity?
They decalcify
What happens to astronauts’ bones in long periods of zero gravity?
They decalcify
What does weight-bearing exercise do to bones/
It builds up the bone (induces bone remodeling with the pressure it puts on the bone), helping to prevent osteoporosis (loss of bone density)
What is osteoporosis?
Loss of bone density
What is osteoporosis?
Loss of bone density
What are joints?
Where two or more bones come together; allow motion in different directions
What connective tissues connect muscles and bones?
Ligaments, tendons
What are ligaments?
connective tissue that holds bones together at joints
What are tendons?
connective tissue that joins muscle to bone
What are tendons?
connective tissue that joins muscle to bone
ex. Golgi tendon organ sense contraction of muscle
In what direction do muscles exert force?
In only one direction
How do muscles create movement?
By working in antagonistic pairs (opposite): flexor and extensor
What is the flexor and what are some examples?
The muscle that bends or flexes the joint Biceps femoris (back of thigh) or biceps (arm)
What is the extensor and what are some examples?
The muscle that straightens or extends the joint
Ex. quadriceps (front of thigh) or triceps (arm)
