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3 types of muscle tissue
Skeletal, cardiac, smooth
Muscular system
ONLY skeletal muscles; each muscle is considered an organ
Funtions of muscle
Movement, Stability, Control of body openings and passages, heat production
Movement for Muscles
to move body parts, body contents, and to communicate
Stability in Muscles
Maintain posture and resist pull of gravity
Excitability (Responsivenes)
react to stimuli
What is another name for excitability?
Responsiveness
Condutivity
Spread electriacal impulse through muscle cell
Contractility
Shorten when stimulated
Extensibility
Can stretch without harm
(Lengthen beyond normal position without being harmed)
Elacticity
Can recoil from stretch
Skeletal
Voluntary, striated, attached to bone, contains muscle cell (muscle fiber/myofiber)
Skeletal muscle cell
Muscle fiber / Myofiber
Cardiac
Involuntary, striated, cardiomyocyte cell
Cardiac Cell is called
Cardiomyocyte
Smooth
Involuntary, non-striated, fusiform shaped
Fusiform cell shape
(diamond shape) tapered at ends
Structures of a muscle fiber
Sarcolemma
Sarcoplasm
Sarcoplasmic reticulum
Sarcolemma
Have Transverse (T) Tubules (invaginations of the sarcolemma)
Sarcoplasm
Contain myofibrils, glycogen, and myoglobin
Sarcoplasmic reticulum
A modified ER located with calcium + contains terminal cisterns
T/F : Calcium is not important
FALSE; Calcium is important as it aids muscle contractions.
Myofilaments
Contractile proteins and regulatory proteins
What are the types of myofilaments?
thick and thin filaments
Thick myofilament
Are Myosin
Thin myofilament
Are actin
Fibrous (F) actin
The part that resembles a necklace
Globular (G) actin
The bead in the necklace
Active Site
Myosin binding area on G actin
(Blocked by tropomyosin)
Regulatory proteins
Regulate when contraction occurs; consist of tropomyosin and troponin
Tropomyosin
Blocks active sites when the muscle relaxes
Troponin
Attaches to tropomyosin and binds to calcium when excited
Striations
narrows stripes that run perpendicular to the length of the cell
What are striations composed of?
Z lines, I band, A band, M line, H band
Sarcomeres
Goes from one Z-disc to another Z-disc, which consist of:
- A Band
- H Band
- M-Line within
A band
DARK stripe of thick myofilaments that partly overlap thin myofilaments
(Memory Trigger: Dark has an A in it)
H Band
Central region of A band that is a little lighter due to lack of thin myofilaments
M Line
Midline of A band (and H) that anchors thick myofilaments together
I Band
Light strip of thin myofilaments only
(Memory Trigger: i in light)
Z Disc (Z-Line)
- Midline of I band
- defines boundaries of sarcomere
- anchors actin and titin
During heavy exercise, the muscular system receives more than _________ of the heart's output.
3/4
Myasthenia gravis (MG)
autoimmune disease, destruction of neurotransmitter receptors
Muscular dystrophy
- Defective gene for dystrophin (a muscle protein)
- Skeletal muscle degeneration
Myopathies
diseases of muscle
Multiunit
independent control of smooth muscle cells
Unitary
Several cells excited at once; widespread in viscera
Synaptic Knob
Contains neurotransmitters
Synaptic cleft
The space where neurotransmitters are released
Postsynaptic membrane folds
Contains receptors to receive neurotransmitters