Muscle Cells Flashcards
Name the 3 Muscle Types
- Skeletal
- Cardiac
- Smooth
Myology
Study of skeletal muscles
What are the 5 functions of Muscle?
Movement
Stability
Control body openings and passages
Heat productions
Glycemic control
Properties of Muscle
What is Excitability?
Aka responsiveness, ability to react to stimuli
Properties of Muscle
Conductivity
Ability of spreading electrical impulse through muscle
Properties of Muscle
Contractility
Ability to shorten when stimulated
Properties of Muscle
Extensiblity
Ability to stretch without harm
Properties of Muscle
Elasticity
Ability to recoil from stretching
Skeletal Muscle Tissue
- Striated, alternating light and dark bonds
- voluntary, decide to move
- attached to bone
- made up of myofiber/muscle fiber
Cardiac Muscle Tissue
- Striated
- Involuntary movement
- Made up of cardiomyocyte
Smooth Muscle Tissue
- Nonstriated
- Involuntary movement
- Fusiform cell shape (thick in center, tapered at ends)
Sacrolemma
Plasma membrane of muscle fibers (outer layer)
Transverse Tubules
Penatrates the sacrolemma
Sends electrical currents from outside stimuli to the inside of the sacrolemma
Sacroplasm
Cytoplasm of the muscle cell
Contains:
- glycogen: storage of energy
- Myoglobin: binds to oxygen
- Myofibril: makes up bundles of muscle fibers
Sarcoplasmic Reticulum
Stores and releases calcium for muscle contraction and relaxation
Contains Terminal Cisterns:
- stores and releases calcium when action potentials goes through transverse tubules, eliciting muscle contraction
Thick Myofilaments
Made up of myosin protein
Heads project out from hundreds of myosin bundled together
Thin Myofilaments
Made up of two layers of actin
Fibrous (F) actin: resembles necklace
Globular (G) actin: resembles one bead of necklace
- Active site: myosin binding area on G actin
Elastic Myofilaments
Made up of titin protein
Anchors thick myofilaments
Myofilaments
Functions of Tropomyosin and Troponin
Tropomyosin:
Blocks active sites when muscle is relaxed
Troponin:
Attaches to tropomyosin, binds calcium when excited
Describe Skeletal Muscle Striations
Narrow light and dark strips perpendicular to cell
(A-band: Dark stripe
I-band: light stripe)
Striations
A-Bands
Dark stripe of thick myofilaments (myosin) that partly overlap thin myofilaments (actin)
Striations
H-Bands
Central region of A-Bands that only contain myosin
Striations
M-Line
Midline of A-Band and H-Band
(holds thick myofilaments together)
Striations
I-Bands
Light Stripe of thin and elastic myofilament (only F and G actin, no myosin)
Striations
Z-Disc
Protein that anchors thin and elastic filaments
Defines boundaries of a sarcomere (Z-Disc to Z-disc)
Striations
Sarcomere
Made up of both actin and myosin (both responsible for muscular contraction)
Basic unit of contractile muscle fiber
Blood supply to Muscles during resting and heavy excerise
Resting: Muscle receives 1/4 supply of hearts blood output
Heavy Excerise: Muscle receives 3/4 supply of hearts blood outputs
Describe what happens at the Neuromuscular Junction: Synapse
(aka point of communication)
- Motor Neuron Synaptic knob contains vesticles containing ACh
- ACh gets deposited by the motor neuron synaptic knob and goes through the synaptic cleft
- Postsynaptic membrane folds of muscle cells contain ACh receptors
- ACh binds to receptors that then trigger an action potential that sends info into the muscle
Motor Units
One motor unit can control multiple muscle fibers (behaves as a single functional unit)
Small amounts of motor units are used in fine motor control (ex. eyeball movement)
Large amounts of moter units are used in larger muscle contraction (Ex. leg movement)
What are large motor units associated with?
Strength
What is ACh?
A neurotransmitter
Describe a what a Neuromuscular Junction is
The site where the nerve fiber (axon terminal) connects with the muscle fiber (motor end plate)
Contraction and Relaxation
Excitation: 1st Phase (1-3)
- Nerve signal arrives at synapsis knob
- Knob releases ACh, ACh bings to muscle receptors, ion gates open which excites muscle
- Excitation spreads down and through muscle cell
Contraction and Relaxation
Excitation - Contraction Coupling: 2nd Phase (4-8)
- Electrical impulse triggers calcium realse from SR (Sacroplasmic Reticulum)
- Calcium binds to troponin, which moves tropomyosin to expose actin
- Myosin breaks down ATP and extends head
- Myosin forms cross-bridge with actin
- Myosin pulls actin in power stroke, then detaches, reattaches, pulls again, etc
Contraction and Relaxation
Relaxation: 3rd Phase (9-10)
- Nerve singal stops
- SR (Sarcoplasmic Reticulum) reabsorbs calcium, troponin blockade resumes and tension subsides
Slow Oxidative Muscle Fibers
- Slow twitch, Red, Type 1 fibers
- Small diameter
- Aerobic ATP production (oxygen required)
- Abundent in Mitochondria, Myoglobin, Capillaries (gives the red color)
- Low Levels of glycogen
- Resistant to fatigue
- Predominate in postural muscles
