Muscular System Flashcards
Bootcamp
what are the types of muscles
Smooth muscle
Cardiac muscle
Skeletal muscle
Smooth muscle
- Present in organ, airways blood vessels
- involuntary
- 1 nucleus per cell
- not striated (does not contains Sarcomeres)
Cardiac Muscle
- Present in the heart
- involuntary
- 1 nucleus per cell
- striated (contains Sarcomeres)
- contains intercalated disc which are made up of Desmosomes). and gap junction that connect the cytoplasm of cells together to allow ion exchange and coordinated electrical impulse propagation.
Skeletal muscle
- Present around bone
- voluntary
- many nuclei per cell
- Striated (contains Sarcomeres)
What is the skeletal muscle composed of?
Muscle → Muscle fascicles → Muscle fibers (muscle cells) → Myofibrils (contractile protein)
Sarcolemma
is the muscle fibers cellular membrane and it protects each muscle fiber
- Contains T-tubules
Sarcoplasm
is the cytoplasm of the muscle fiber and holds the myofibrils
Epimysium
- the most superficial sheath
- covers the muscle itself
Perimysium
Covers the muscle fascicles
Endomysium
- the deepest sheath
- cover the muscle fibers
what movement does all muscles do to move a body part?
they Contract (pull), They never push
Sarcomeres
inside of myofibrils are the functional unit of muscle fibers and shorten to cause muscle contraction
Myofilaments
contained with sarcomeres, divided into tin actin filaments and thick myosin filaments
Sarcoplasmic Reticulum
is the endoplasmic reticulum of muscle fibers that release stored calcium ions into the sarcoplasm through voltage-gated calcium channels when triggered by the depolarization of the muscle
Cross bridge cycling:
- Initiation: Calcium ions expose the
myosin-binding-sites on actin. - A cocked back, high energy myosin head
(containing ADP and Pi) forms a cross bridge with the actin. - The myosin head contracts and the power stroke occurs, bringing the myosin head back to a low energy state and releasing ADP and
Pi. As a result, the sarcomere shortens. - A new ATP molecule binds to myosin, causing
detachment of the myosin head from the actin filament. - The myosin head is an ATPase, and it
hydrolyzes the ATP into ADP and Pi. This
causes the myosin head to re-enter a cocked back, high energy state. (Return to Step 2 if calcium ions present). - Termination: Neuronal signaling from motor neurons ends. The sarcoplasmic reticulum pumps calcium back into itself, and troponin
brings tropomyosin back to cover myosin-binding sites on actin.
Rigor mortis
occurs in dead animals where there is no ATP available to release myosin from the actin
Z-line
-are the ends of the sarcomeres
- Thin actin filaments branch from the Z-lines towards the middle of the sarcomere
M lines
are the midpoints of the sarcomeres
- thick myosin filaments branch from the M lines towards the ends of the sarcomere
I band
is the area in the sarcomere where only actin filaments are present
A band
is the area in the arcomere where actin and myosin overlap
H zone
is the area in the sarcomere where only myosin is present
Motor unit
make up muscles; refers to all the muscle fibers innervated by a single neuron
Small motor units
include only a few muscle fibers and are used in precision movement
large motor units
includes many muscle fibers that are innervate by a single neuron and are used in powerful movements
twitch contraction
is the contraction of a muscle fiber through motor unit stimulation
- each twitch is the same size ad duration
- follow all-or-none principle
all-or-none principle
that a depolarization will cause all the muscle fibers to twitch if it is above threshold potential but will not cause any twitching if the depolarization is below threshold potential
what are the three phases of a twitch
Latent, Contraction, relaxation
Latent
action potential spreads over sarcolemma and T-tubules, signaling to sarcoplasmic reticulum to release calcium
Contraction
formation of cross bridges as a result of calcium ions binding to troponin.
- H zones shrink and muscle tension increases
Relaxation
Calcium is pumped back into the sarcoplasmic reticulum, ending cross bridge cycling and decreasing muscle tension
Summation
a process by which twitch add up to create a larger overall contraction
what are the two types of summation
- Wave summation (temporal summation)
- motor unit summation
Wave summation (temporal summation)
depolarizing a motor unit again during the relaxation phase
- may cause tetanus
-Twitches blend together during tetany, eventually causing fatigue (loss of muscle contraction).
tetanus
is when the muscle fibers cannot be further stimulated due to a lack of relaxation
motor unit summation
- different motor units are stimulated at different times to produce the intended amount of muscle contraction
- also known as Size principle of motor unit recruitment because smaller motor units are stimulated first before larger motor units come in to
help.
muscle
tone (muscle tonus)
Weak and involuntary twitches in small motor unit groups contribute to maintaining
