Chapter 10 Flashcards
What are the three types of muscle tissue?
Cardiac, smooth, skeletal
What are the common properties of all muscle tissue and briefly describe them?
Excitability - Plasma membrane changes electrical state from polarized to depolarized to send electrical signal (action potential) along length of membrane
Contractility – shortening of muscle tissue when one protein is being pulled by another protein
Elasticity – ability to return to original length when relaxed (due to elastic fibers)
Extensability - stretch or extend
List the three connective tissue layers that help to compartmentalize muscle tissue.
Epimysium, perimysium, endomysium
What is the function of the sarcoplasmic reticulum?
Stores, releases, and retrieves calcium ions
List the components of the sarcomere.
Actin, myosin, troponin, tropomyosin
Write out the steps in excitation-contraction coupling.
- Signaling begins when neuronal action potential travels along axon of motor neuron – individual branches and terminate at NMJ
- At NMJ, axon terminal releases chemical messenger (neurotransmitter) acetylcholine (ACh)
- ACh diffuse across space (synaptic cleft) and bind to ACh receptors on motor end-plate of sarcolemma (other side of synapse)
- Binding of ACh – channel in receptor opens and positive charged ions pass through muscle fiber – cause it to depolarize (membrane potential of muscle fiber becomes less negative or closer to 0)
- Membrane depolarization – another set of ion channels (voltage-gated sodium channels) triggered to open
- Sodium enters muscle fiber – action potential rapidly spreads along membrane to initiate excitation-contraction coupling
- Immediately after depolarization, it repolarizes – establishes negative membrane potential
- ACh degraded by enzyme acetylcholinesterase (AChE) so ACh cannot rebind to receptor and reopen its channel – unwanted extended muscle excitation and contraction
- Propagation of action potential along sarcolemma is excitation part
What is the purpose of a T-tubule?
Allows the action potential to reach the membrane of the sarcoplasmic reticulum
What are the three mechanisms to generate ATP?
Creatine phosphate pathway, aerobic respiration or fermentation, glycolysis
Describe isotonic and isometric contractions.
Isotonic – Tension in muscle is constant – load moved as length of muscle changes
Concentric – muscle shortening to move load
Eccentric – muscle tension decreases and muscle lengthens
Isometric - As muscle produces tension without change in the angle of skeletal joint – does not move load
Differentiate between treppe, incomplete tetany, and complete tetany.
Treppe - Skeletal muscle dormant for extended period and then activated to contract, initial contraction generates half force of later contractions; Muscle tension increases in graded manner
Incomplete tetany - quick cycles of contraction with short relaxation phase for each
Complete tetany - If stimulus frequency is so high that there is no relaxation phase – contractions continue
List and describe the three types of muscle fibers.
Slow oxidative – contract slowly and use aerobic respiration
Fast oxidative – contract quickly and use aerobic respiration
Fast glycolytic – contract quickly and use glycolysis
What happens in sarcopenia?
Muscle fibers die – replaced with connective tissue and adipose tissue
Muscles lose ability to produce powerful contractions – decreased strength (even in posture and mobility)
Decreased FG fibers
Greater number of SO fibers – longer contractions that do not produce powerful movements
Decreased size of motor units – fewer fibers stimulated and less muscle tension produced
What makes contraction in cardiac muscle unique?
Contract in wave-like pattern due to intercalated discs and contract as a syncytium and controlled by pacemaker cells that have autorhythmicity
What is calmodulin?
Binds calcium in smooth muscle tissue to activate myosin kinase - activates myosin heads by phosphorylating them
Describe hyperplasia in smooth muscle?
Divide to produce more cells and see in uterus during puberty – more uterine smooth muscle fibers and increase myometrium
