Muscle Structure and Function Flashcards
_____ Muscles mainly line hollow organs (eg gut, blood vessels) and are not
under voluntary control.
Smooth
_____ muscle is located only in the heart, it generates force to pump blood
around the body and is not under voluntary control.
Cardiac
_____ muscle applies force to the bones to control posture and body
movements. It is mostly under voluntary control.
Skeletal
Which muscle type(s) are made up of cells called fibres
All 3
Skeletal, Cardiac, Smooth
Volunatary control in muscles is…
Being in control
(Using mind to control and activate them)
Muscles develop force by contracting (True or false)
True
…Individual muscle cells are called muscle fibres, They
gather into bundles called ____
Fascicles
[Fa-Sick-Kill]
*Fascicles are further bundled into _____
Muscles
A muscle fibre is comprised of bundles of myofibrils, which are made of repeating
units known as ______
sarcomeres
What is a sarcomere?
-The basic contractile unit of a muscle fiber.
- Made up of actin (thin) and myosin (thick) filaments.
- Shortens during muscle contraction to generate force.
Whats special about apperance of skeletal muscle cells?
-Long and tube-like
(Due to repeating sarcomeres)
The ______ is the muscle fiber’s version of the phospholipid bilayer (cell membrane).
sarcolemma (Sar-Co-Lemma)
What is the job of the SR (Sarcoplasmic reticulum) which is wrapped around muscle cells
The sarcoplasmic reticulum (SR) in muscle cells is responsible for **storing, releasing, and reabsorbing calcium ions (Ca2+)
Sarcoplasmic reticulum (SR) is associated with the T tubules at regular intervals?
(True false)
True
Transverse tubules (t-tubules) are extensions of
the sarcolemma deep into the fibre.
What are the three key proteins involved in excitation during Excitation-Contraction Coupling (EC-Coupling?
DHPR (voltage sensor), RyR (calcium channel), SERCA (calcium pump).
How does the signal lead to muscle contraction in EC-Coupling?
The electrical signal travels down the T-tubules, activates a receptor (DHPR), which then triggers another receptor (RyR) on the SR to release calcium, causing the muscle to contract.
The signal is coming from the nerves running throughout the muscle
(If Lost look at diagram on One note skeletal muscles)
How does the muscle relax in EC-Coupling?
After contraction, calcium is pumped back into the SR by Calcium Pump using ATP, reducing calcium in the cell and allowing the muscle to relax.
striated appearance is like..
Striped
(Like long strips)
Transverse tubules (T-tubules) are tube-like
extensions of the sarcolemma.
What is their job
Their job is to conduct electrical signals
(action potentials) deep into the core of the
fibr
*When the nerves signal to the muscle that it’s time to contract, how does
that signal get inside the cell and how does it cause a contraction? How
is the signal stopped so the contraction can end?
A motor neuron sends an electrical signal (action potential) down its axon.
It then binds to binds to sarcolemma, triggering an action potential in the muscle cell.
The action potential spreads along the sarcolemma and travels deep into the muscle fiber through T-tubules (invaginations of the membrane).
T-tubules carry the signal to the sarcoplasmic reticulum (SR), which stores calcium ions (Ca²⁺).
Then the nerve signal stops and Ca²⁺ is pumped back in.
Sarcomeress are at the _____ level
(size of them)
cellular
In EC-Coupling RyR are the
Passive channel for Ca2+ to flow for muscle contraction
In EC-Coupling DHPR are the
Voltage sensors
(Voltage from nerves telling muscle to contract)
In EC-Coupling SERCA are the
ATP pump
(That pumps Casium back into Sarcoplasmic reticulum to relax the muscle)
In T Tubles the (T) stands for
(Prolly not important)
Transverse
Tropomyosin is
The ribboin-like protein that wraps around actin that blocks myosin heads touching the actin for EC coupling
Troponin is
The ball-like protein that blocks myosin heads touching the actin for EC coupling
How does Calcium ions allow Myosin heads to pull on Actin
When Ca²⁺ is released from the sarcoplasmic reticulum, it binds to troponin, causing tropomyosin to shift and expose myosin-binding sites on actin. This allows myosin to bind, triggering muscle contraction.
The Cross-Bridge Cycle for EC-Coupling
The head is attached to actin.
Cross-Bridge Detachment – ATP binds to myosin, causing it to release actin.
Myosin Reset (Reactivation) – ATP hydrolyzed → myosin head recocks (ADP + Pi).
Cross-Bridge Formation – Myosin head (with ADP + Pi) binds to actin.
Power Stroke – Pi is released → myosin pulls actin → ADP released.
What two factors determine skeletal muscle force generation?
Recruitment (number of fibers contracting) and frequency of stimulation.
What happens when the frequency of stimulation is super high in skeletal muscles?
It reaches tetanus, resulting in maximum possible force.
What is a characteristic of muscles rich in fast fibers?
They produce a lot of force quickly but tire out quickly due to limited energy reserves. They are WHITE
What is a characteristic of muscles rich in slow fibers?
hey can generate a lot of energy over time and are difficult to fatigue. They are RED
Fibres are covered in
Endomysium
Fascicles are covered in
Perimysium → Covers fascicles
Muscle (whole thing) → Covered by ___
Epimysium
Which of these describes an eccentric muscle contraction?
A) Muscle shortens while generating force
B) Muscle lengthens while generating force
C) Muscle generates force without changing length
D) Muscle fibers fatigue and stop contracting
B) Muscle lengthens while generating force
What occurs in a concentric muscle contraction?
(think about Biceps in curl)
The muscle shortens while generating force, such as lifting a dumbbell during a bicep curl.
What defines an isometric muscle contraction?
(think about Biceps in curl)
The muscle generates force without changing length, like holding a plank or carrying an object steady.
What happens during an eccentric muscle contraction?
The muscle lengthens while generating force, often to control movement, like lowering a dumbbell.
Which of the following occurs when a muscle is in tetanus?
A) The muscle contracts and relaxes rapidly
B) The muscle fails to contract
C) The muscle remains in a sustained contraction
D) The muscle generates a weak contraction
C) The muscle remains in a sustained contraction
Which muscle is the prime mover for knee extension?
A) Biceps femoris
B) Gastrocnemius
C) Rectus femoris
D) Tibialis anterior
C) Rectus femoris
2 Arrangement patterns of Muscle fibres
Parallel (Self explanitory)
and
Pennate
(Diagonal, so more fibres in same area giving them morepulling power, but now less ROM due to shorter fibres)
Penate muscles are _____ able to Contract further than Parallel muscle and provide a ______ maximum contraction force than Parallel
1) Less
2) Greater
Liam Lawson Is..
Washed
