Muscles Flashcards
Muscle function (1)
Exert force (movement, maintain posture)
Muscle function (2)
Stabilize joints
Muscle function (3)
Produce heat
Muscle function (4)
Protect internal organs
Special feature (1)
Contractile (exerts force by contracting/shortening and pulling things together)
Special feature (2)
Electrically excitable = allows rapid stimulation of whole cell
Skeletal muscle tissue
Voluntary (typically) except reflexes
Cardiac muscle tissue
In heart
Smooth muscle tissue
In walls of other hollow organs
What are skeletal muscles main function?
To move bones
Skeletal muscle origin attachment
The less moveable attachment (proximal)
Skeletal muscle insertion attachment
The more moveable attachment (distal)
Skeletal muscles must cross a _____ to act on that _____
Joint, joint
What does skeletal muscle action depend on?
Side of bone the attachment is on
Muscles do work by ____________ NOT __________
Shortening, lengthening
Antagonist
Another muscle undoing an action for another muscle’s action
Agonist (prime mover)
A muscle that has major responsibility for a particular action
Synergist
A muscle that helps the agonist
Sheaths of connective tissue organize what?
Muscle fibers
Endomysium
Surrounds muscle fiber (delicate white network)
Perimysium
Surrounds each fascicle (bundle of muscle fibers wrapped around)
Epimysium
Surrounds entire muscle (thickest and wraps around entire muscle)
Tendon
Extension of the sheaths (connects muscle to bone)
Fascia
Surrounds groups of muscles
Muscle fiber (cell) is normally as long as what/
The whole muscle
Myofibrils
Long organelles made of actin and myosin filaments
Multinucleate
Has many nuclei
In muscle cells, actin and myosin are organized into myofilaments which is a type of what?
Microfilament
Striations indicate what?
Repeating groups of protein filaments (actin, myosin, etc.)
What is each section of myofibril called?
Sarcomere
Sarcomere
Basic functional unit of skeletal muscle contraction
Can muscle fiber cells divide after birth?
NO!
Strength training
Each muscle fiber thickens by adding more protein filaments
Strength is proportional to _____________________
Total cross-sectional area of fibers attached to tendon
Which muscles are stronger? Pennate or parallel?
Pennate are stronger, but parallel are more flexible/able to contract
Satellite cells
Undifferentiated cells between muscle fibers
Do satellite cells continue dividing?
Yes when needed
What happens when muscles grow, strengthen, or there is muscle damage?
Satellite cells merge with muscle fibers (adds nucelus)
Nerve cells
Direct nervous stimulation is the ONLY cause of contraction
Motor neuron
Nerve cell that controls muscle fibers
Motor unit
Motor neuron + all muscle fibers it innervates
Neuromuscular junction
Region where motor neuron contacts muscle fibers
What does botox do in the neuromuscular junction?
Botox blocks neurons from getting to the muscles (paralyzes face essentially removing wrinkles)
What is the sliding filament mechanism?
Myosin and actin filaments slide past one another (myosin head crawls along actin)
What happens while actin and myosin are sliding against each other in the sliding filament mechanism?
The sarcomere shortens by increasing overlap between actin and myosin = FILAMENTS DO NOT SHORTEN
Where is cardiac muscle found and is it voluntary?
Walls of heart, no
What do chains of short branching cells allow for in cardiac muscle?
Stacked end-to-end cells allows for coordinating activities
How many nuclei are there per cell in cardiac muscle?
1 or 2 nuclei per cell
Can cardiac muscle cells divide after birth?
NO! Stuck with the heart you are born with essentially
Intercalated discs
Junctions between cells
Gap junctions
Passageway for communication (ions carry signal between cells)
Fasciae adherens
Function is resisting tension (hold adjoining cells together)
Is cardiac muscle striated?
Yes, zig-zag shaped in orderly structure
Are sarcomeres present in cardiac muscle?
Yes, along with actin and myosin
Causes of contraction in cardiac muscle (1)
Spontaneously generated signal! (on a timer)
Causes of contraction in cardiac muscle (2)
Via gap junctions from other cardiac muscle cells (got signal from something)
The _____ of spontaneous contraction is/is not affected by nervous input
Rate, is
Where does smooth muscle form?
Walls of hollow organs (other than heart)
Are smooth muscle contractions voluntary?
No!
How many nucleuses per fusiform cell in smooth muscle?
1 (uninucleate)
Can cells divide after birth in smooth muscle?
Yes! They can easily regrow and regenerate better than other tissues
Does smooth muscle have striations or sarcomeres?
No! Instead, has network of actin and myosin
What do all the gap junctions in smooth muscle allow for?
Coordinating contractions
What is the loose organization of actin and myosin good for?
Allows smooth muscle cells to generate force even when greatly stretched (DIG system stretching when there’s food present)
What happens when smooth muscle contracts in circular layers?
The tube narrows
What happens when smooth muscle contracts in longitudinal layers?
The tube shortens
Smooth muscle contraction cause (1)
By direct nervous control (but involuntary)
Smooth muscle contraction cause (2)
Other chemical signals (ex: hormones/during pregnancy)
Smooth muscle contraction cause (3)
Stretching
Smooth muscle contraction cause (4)
Via gap junctions from other smooth muscles
Smooth muscle contraction cause (5)
Spontaneously generated
