Chapter 12 Flashcards
Where is skeletal muscle found in the body and what are some of its unique structures?
Skeletal muscle is found where the muscles that move the body
- multinucliated cells
- uniform striations
Where is cardiac muscle located and what are its distinct features?
It is only found in the heart
- singly nucliated cells
-intercalated disks help keep the tissue in place while the heart is pumping
- striated
- contains cardiomyocytes (specialized heart cells)
Where is smooth muscle located in the body and what are some of its unique features?
Found in internal organs like the stomach and bladder
- not striated
- singly nucliated
How is a skeletal muscle organized starting from the muscle down to the sarcomere? Describe it.
The skeletal muscle is made up of
multiple muscle fascicles which contains blood vessels, nerves, and multiple muscle fibers
muscle fibers are made up of multiple muscle cells
muscle cells contain sarcoplasmic reticulum, nuclei, t-tubules, mitochondria, glucose granules, and myofibrils
myofibrils contain sarcomeres
How are muscles connected to bone? And what is it made out of?
Skeletal muscles are connected to bone by tendons made of collagen.
What is the outer layer of a skeletal muscle?
Epimysium
What is the connection between the epimysium and the tendons?
The tendon extends to the epmysium
What is the outer layer of muscle fasicles?
Perimysium
What is the outer layer of a muscle fiber?
endomysium
What is the role of t-tubules in a muscle cell?
It is where an action potential from a motor neuron will travel from the motor end plate on the sarcolemma of the myofibril down through the t-tubes to get deep into the muscle cell
What is the role of the sarcoplasmic reticulum in a muscle cell?
It is modified endoplasmic reticulum that stores calcium in the muscle cell which is important to contract a muscle
How much higher are the calcium levels in the sarcoplasmic reticulum than the rest of the muscle cell? An what is the name of the protein that holds it in place?
40,000 times higher and casequesterin
What is in a myofibril?
It is made up of long line repeating sarcomeres
What defines a sarcomere’s boundaries?
The z- discs that are kind of like the bookends for each individual sarcomere
What is the h-zone of a sarcomere?
Area between Z-disk and M-line where there’s only myosin present
What is the m-line of a sarcomere?
Midline of the sarcomere
What is the I band of a sarcomere?
Light band of the sarcomere that contains only actin filaments
What is in the a band of a sarcomere?
Contains thick and thin filaments
What are the regulatory proteins of the sarcomere?
Troponin and Tropomyosin
What are the contractile proteins of the sarcomere?
Actin and myosin
What are the stabilizing proteins of the sarcomere?
Titin and nebulin
What is a contraction?
it is the creation of tension within a muscle
What is the sliding filament theory of muscle contraction?
The sliding filament theory of contraction is that in order for a contraction to occur, it must the thick (myosin) filaments and the thin (actin) filaments must overlap
What are the steps for calcium to get into the sarcomere beginning with the action potential arriving in the axon terminal of the motor neuron?
1) the action potential arrives and this causes calcium channels to open
2) this allows for the vesicles containing ACh to bind to the membrane and for exocytosis to occur
3) after diffusing across the synapse it allows for ACh to bind to nicotonic receptors and this causes Na+ to open
4) as a result that causes and action potential/ a depolarization to travel through the t-tubules
5) when the action potential passes where the t-tubules meet the sarcoplasmic reticulum it causes the DHP channels to change their shape which pulls on the RYR channel
6) the pull on the RYR channel cause the calcium to flow out of the sarcoplasmic reticulum and flood into the myofibril
7) this is what gets Ca2+ into the sarcomere
How does the calcium get back into the the sarcoplasmic reticulum?
through a calcium ATPhase
How does the calcium in the sarcomere affect muscle contraction beginning in the rigor state?
1) beginning in the rigor state, the myosin head binds to ATP so it can relax
2) when the calcium arrives in the sarcomere it binds to troponin which shifts tropomyosin out of the way of the active site of actin
3) the myosin splits (hydrolizes) the ATP into ADP and P (energized state)
4) with the active site open it allows for the myosin head to bind to the active site (cross bridge is formed)
5) then it releases the ADP and P in a power stroke and myosin heads turn towards the midline
What is the energized state of actin and myosin?
after myosin has split the atp into adp and p and its in the cocked position
What happens when myosin does a power stroke?
It is already bound to the active site of the actin and it releases the ADP and P
What does a muscle need to relax?
The myosin needs another ATP to attach to in order to relax
What sources of energy are stored within muscle cells?
ATP and Phosphocreatine
What is phosphocreatine?
A molecule that has high energy phosphate bonds and that can transfer its energy into ADP and with the enzyme creatine kinase, it can get turned into ATP
What are the four methods used by muscles to regenerate ATP
Phosphocreatine, Anaerobic glycolysis, Citric acid cycle, and Fatty acid oxidation
How fast is the phosphocreatine process and what is its ATP yield?
Very fast and it yields 1 ATP
What are some of the downsides of phosphocreatine?
Must be replenished at rest
Creatine is a waste produce
What is the speed and ATP yield for ATP glycolysis?
Fast and it yields 2 ATP
What are the byproducts of anaerobic glycolysis?
Lactic acid disrupts pH
What is the speed of production and the ATP yield for the citric acid cycle?
Slow and produces roughly 30 ATP
What are the downsides of the citric acid cycle?
It requires oxygen and glucose
What is the speed and ATP yield of Fatty acid oxidation?
Very slow and yields 90-129 ATP
What is the downfall of fatty acid oxidation?
It is only useful during light excercise
When going around doing day to day activities what forms of ATP production is our muscles most likely to use?
Citric acid cycle and fatty acid oxidation
What forms of ATP production are more likely to be used for strenous excercise?
Phosphocreatine and anaerobic glycolysis
What do the muscles need ATP for?
- the relaxation and contraction cycles
- sequestering calcium back into the sacroplasmic reticulum for relaxation Calcium ATPhase
- sodium potassium pumps
How is creatine filtered out of the body?
It is filtered by the kidneys and then excreted via urine
How does the body regulate the lower pH caused by lactic acid build up?
The kidneys have to balence it out in order to help the body remain in homeostasis
How does low pH affect the muscles?
A low pH can cause pain in the muscles
How does low pH affect the membrane potential of cells?
It lowers it making it harder for the cell to produce another graded potential based on an action potential
What is the one form of ATP production that is used by cardiac muscle?
Fatty acid oxidation and it packed with a lot of mitochondria to make that possible
What two forms of ATP production are used by smooth muscle?
Fatty acid oxidation and the Citric Acid Cycle
What forms of ATP production are used by skeletal muscle?
Phosphocreatine
Anaerobic glycolysis
Citric acid cycle
Fatty acid oxidation
How is muscle fatigue described?
It is described as as a reversible condition where exercising a muscle that cannot generate or sustain an expected power output.
What are the two main forms of what can cause muscle fatigue?
Central and peripheral nervous system signals
What happens in central fatigue?
This is when the brain starts to say that its done even though physiologically you could still keep going
What can signal central fatigue to occur?
A buildup of H+ or lactic acid in the muscles
What is the goal of central fatigue?
to protect yourself from completely depleting your physical energy stores
What happens in peripheral fatigue?
It is when your become physically fatigued as a result of depleting things you need to keep going or an accumulation of things that prevent you from continuing
What stores get depleted in peripheral fatigue?
glycogen
phosphocreatine
atp
What stores get accumulated in peripheral fatigue?
Phosphate in the cytosol
K+ in the extracellular fluid
What can also cause peripheral fatigue?
decreased neurotransmitter availability
What are the two factors that determine the speed of the muscle fiber/cell?
how fast the myosin splits ATP and the speed of calcium sequesteration
What are the characteristics of type 1 or slow twitch fibers?
- mostly use oxidative ATP production
- extensive myoglobin (red)
-small diameter - high capillary density (red)
What are the characteristics of type 2 or fast twitch muscle fibers?
- mostly glycolytic ATP production
- little myoglobin
- large diameter
- low capillary density
Does the term fast glycolytic fibers refer to type 1 or type 2 fibers?
type 2 fast twitch
Does the term slow oxidative refer to type 1 or type 2 muscle fibers?
type 1 muscle fibers or slow twitch
What are the characteristics of intermediate muscle fibers?
it contains a mix of both
In human athletes, are sprinters, jumpers, or distance runners more likely to have fast glycolytic fibers in their quadricepts muscles?
Sprinters and Jumpers
In human athletes, are sprinters, jumpers, or distance runners more likely to have slow oxidative fibers in their quadriecpts muscles?
distance runners
What does tension of a muscle mean?
a direct reflection of the length between the individual sarcomeres before a contraction begins.
What is resting fiber length?
Resting fiber length is length between the thin and thick filaments that gives them the optimum amount of force when they contract
What does too much overlap between resting fibers do to the force of the sarcomere contraction?
It’s a too small amount of sliding possible to create a necessary amount of force
What does too little overlap between resting fibers do to the force of the sarcomere contraction?
Leads to too few cross bridges between the filaments or not enough of a pull
Why do animals (humans included) feel the natural tendency to stretch?
To help adjust their sarcomeres into the optimal resting fiber length
What does a single action potential cause in a muscle?
A twitch
What happens when there are multiple action potentials in a row before the muscle fully relaxes?
That results in the summation of the action potentials and results in an increase of strength of the contraction
What is a motor unit?
It is made up of one somatic motor neuron and the muscle fibers that it stimulates
Can a motor neuron innervate different types of muscle fibers in a motor unit?
no
How many muscle fibers are in a small motor unit?
3-5 muscle fibers
How many muscle fibers are in a large motor unit?
1,000-2,000 muscle fibers
What actions are small motor units used for gross or fine motor skills?
Fine motor skills
What actions are large motor units used for fine or gross motor skills?
Gross motor skills
Where in the body could small motor units be found?
In the muscles that control the face, fingers, and eye muscles
Where in the body could large motor units be found?
In muscles like the quadricepts, and gastrocnemius
What is unique about the sarcomeres within smooth muscle cells?
- actin is more present in smooth muscle compared to skeletal muscle
- it does not have troponin
- there are no sarcomeres
How do motor units help muscles be able to retain the same levels of tension for longer?
Because they can recruited and take turns to give each other rest
(kind of like a relay)
What are the similarities between smooth and skeletal muscle?
They both have myosin and actin cross bridges
Ca2+ is needed to initiate contractions but location and purpose are different
How is smooth muscle different from skeletal?
- slower contractions
-fatigue resistant - small mononucleated cells
- uses electrical or chemical signals
Are smooth muscle contractions periodic, tonic or both?
both
Do smooth muscles act individually, collectively, or both ?
both
What organ systems contain smooth muscle?
Vascular, digestive, urinary, respiratory, reproductive, and ocular
What stimulates smooth muscle contraction?
Calcium that comes from the ECF and it does not bind to troponin but it still initiates the binding between myosin and actin
What trait about the contraction of smooth muscle gives it more contraction length compared to skeletal muscle?
The fact that it twists
What are the characteristics of cardiac muscle?
-striated
- mono-nucleated
- short, branched cells
- gap junctions at intercalated discs
- altered by ANS and hormones
Which part of the body controls spinal reflexes and central pattern generators?
The spinal cord
Which parts of the brain control postural reflexes along with hand and eye movements?
The brain stem and the cerebellum
Which parts of the brain are responsible for voluntary movements?
The cerebral cortex and the basal ganglia
What is the difference between the initiation of voluntary movement compared to a reflex?
With a voluntary movement it starts in the cerebral cortex with to plan the movement
In a reflex any movement that occurs is initiated based on information that is received throughout the body such as the proprecoceptors
Do both voluntary and reflexes both need input from the cerebral cortex?
No, reflexes do not need input from the cerebral cortex but it is used sometimes
For voluntary movement to happen is utilizes the ________________
corticospinal tract
What is unique about learned movement?
That at first is requires a lot of attention from the cerebral cortex as its learned but then as it’s practiced it becomes more automatic
What is the basal nuclei?
It is clusters of grey matter in the brain that controls movement?
Why is the term basal ganglia inaccurate?
Because ganglia are located in the PNS while the basal nuclei is located in the CNS
What 2 parts of the brain are commonly impacted by Parkinson’s disease?
Basal nuclei and the substanita nigra
What are the 3 major symptoms of Parkinson’s disease?
-Tremors
- Slow movements/ unable to initiate movement
- Rigidity
What is decussation?
It describes when fibers cross at the medulla oblongata along the coriticospinal tract
What does decussation mean for a patient’s symptoms versus the location of brain damage in stroke patients?
It means if they are having difficulties moving one side of the body then they opposite side of the brain is affected
ex can’t move left arm = issue in the right part of the brain
Which types of muscle do not connect to bone?
cardiac and smooth
What is the function and location of titin?
runs along from the z disc to m line and it maintains structure and elasticity
What is the function and location of nebulin?
located along actin and stablizes it
What does excitation contraction coupling mean?
It describes how an excitation (chemical change/electrical activity) leads to a contraction (mechanical change)
Put the following steps in order:
1. Myosin heads bind to actin, forming cross-bridges
2. ATP binds to the myosin head, causing it to detach from actin
3. ATP is hydrolyzed, energizing the myosin head
4. Calcium binds to troponin, shifting tropomyosin and exposing binding sites on actin
5. The myosin head pivots, performing the power stroke and pulling actin toward the center of the sarcomere
4,1,5,2,3
Is DHP a protein, receptor or a channel?
Receptor
Is RYR a protein, receptor, or a channel?
Channel
Is type 1 a slow twitch or fast twitch fiber?
Slow or distance runners are number 1
Is type 2 a slow twitch or fast twitch fiber?
Fast twitch because if your hot to go you have to go fast!
