phase 1 week 6 Flashcards
What are the general functions of muscles?
movement
heat production
posture
What are muscle fibres coated with?
endomysium
What are fascicles?
groups of muscle fibres
What are fascicles bound by?
perimysium
What are muscles covered by?
epimysium
Describe skeletal muscles
long cylindrical cells many nuclei striated voluntary rapid contractions
Describe cardiac muscle
branching cells 1 or 2 nuclei striated involuntary medium speed contractions
Describe smooth muscle
fusiform cells 1 nucleus non-striated involuntary slow, wave-like movement
What are some defining features of skeletal muscle?
plasma membrane = sarcolemma cytoplasm = sarcoplasm Smooth ER = sarcoplasmic reticulum many more mitochondria several nuclei transverse (T) tubules - inward extensions of the sarcolemma myofibrils made up from microfilaments
What is a sarcomere?
from Z line to Z line
What is the A band?
The length of the myosin filament
What is the I band?
The regions with no myosin
What is the H zone?
The central region where there is no actin filaments
What connects myosin to the Z band?
titan
Give a summary of muscle excitation and contraction
Nerve impulses reach neuromuscular junction
Acetylcholine is released from the motor neuron
Acetylcholine binds with receptors of the muscle membrane and allow Na+ entry
Na+ influx will generate an action potential in the sarcolemma
Action potential travels down the T-tubule
Sarcoplasmic reticulum releases Ca2+
Ca2+ binds with troponin and moves the troponin-tropomyosin complex
Binding sites on the actin filament are exposed
Myosin heads attach to binding sites and create a power stroke
ATP detaches myosin heads and energises them for another contraction
When action potentials cease the muscles stop contracting
What is a motor unit?
All the muscle cells that are controlled by one nerve cell
Give examples of some motor unit ratios
back muscles 1:100
finger muscles 1:10
eye muscles 1:1
What is muscle tonus?
tightness of a muscle
some fibres always contracted