Lecture 11 Flashcards
What are the 4 skeletal muscle characteristics?
Excitable - responds to stimuli for action potentials
Contractile - shorten or thicken
Extensible - stretch when pulled
Elastic - returns to original shape after stretch/contraction
What are the skeletal muscle functions?
Movement
Posture/ expressions
Heat production
Protection of viscera (abdominal cavity)
How many neurons innervate each muscle fiber?
Only one
How many muscle fibers can be innervate by one neuron?
Can innervate up to 150 fibers
What constitutes a motor unit?
A single motor neuron and all the muscle fibers it innervates
What type of gate releases Ca+ into the synaptic end bulb?
A voltage Ca+ gate to releases the Ach neurotransmitters and exocytosis out
What is the role of ACH in the neuromuscular junction?
Ach is released by Ca+ to pass through the synaptic cleft and attach to chemical gated channels of the motor end plate and allow Na+ to enter the muscle fiber and reach end plate potential
What is the role of Na+ in the motor end plate?
Muscle fiber reaches endplate potential to open more Na+ channels along the sarcolemma -> depolarization causes Ca+ to be released from Sarcoplasmic reticulum
What is the role of Ca+ at the motor end plate?
Is released from sarcoplasmic reticulum to bind with troponin to move tropomyosin and expose actin sites
How does muscle contraction occur?
The ADP + Pi is bound to resting myosin head -> attaches to actin -> power stroke (movement) by releasing Pi -> after power stroke ADP is released -> ATP attaches to release head form actin -> left with ADP + Pi
What line of the sarcomere do the actin filaments move towards?
M line
What area of the sarcomere is in the A band?
The myosin heads (thick filament)
Which band changes shape with the sarcomere movement?
H and I band
What zone does the H band represent in the sarcomere?
The distance between the actin sites (thin filament)
Shortens when contraction occurs
Expands when stretch occurs
What zone does the I band represent on the sarcomere?
The distance between the myosin heads (thick filaments) when they move towards each other during muscle contraction
Becomes smaller in muscle contraction
Becomes larger in muscle stretch
What does the Z disc represent?
The boundary of the sarcomere
Attaches to actin (thin filament)
What condition must be met for muscle contraction to occur?
A high influx of Ca+ for actin to remain exposed
How does muscle fiber relaxation initiated?
Ach is broke down by ACHe to make acetic acid and choline -> Ca+ is reabsorbed by SR -> myosin heads are unable to bind to actin as tropomyosin moves over sites
What is the role of ATP in muscle contraction?
The cross bridge release of myosin head and actin site
The catabolic reaction (ATP ->ADP + Pi) allows for myosin activation
Na+/K+ pump for ATPase activity
What is botulism?
Toxins found in contaminated canned foods that prevent exocytosis of ACH resulting in paralysis
Used as Botox for uncontrolled muscles (blinkin/cross eyed) and prevent wrinkles and sweating
What is Rigor mortis?
Stiffness of death
Leaking of Ca+ from SR causes myosin heads to attach and contract but cannot release due to lack of ATP produced
3hrs after death till 12hrs
Subsides as cells breakdown
What is myasthenia gravis?
Low ACH receptors causing paralysis (motor will not respond)
ACHe inhibitors
Allows for more binding to receptors options
What is curare poisoning?
Prevents Ach from binding to receptors -> paralysis
Using in surgery and tranquilizers (blow darts)
How does nicotine affect the muscle?
Pretends to be Ach and binds to receptors to produce muscle spasms
What happens to the muscle from a black widow bite?
Massive release of ACH causing muscles to continuously contract and stop breathing
