Muscles and Skin Flashcards
1
Q
what are the 3 main functions of muscles ?
A
- locomotion
- maintaining + changing posture
- movement of internal organs
2
Q
what are the 3 types of muscles ?
A
- skeletal muscle
- smooth muscle
- cardiac muscle
3
Q
what is structural syncytium + example ?
A
- multi-nucleated cell that can result from multiple cell fusions of uni-nuclear cells
- skeletal muscle
4
Q
what is functional syncytium + examples ?
A
- electrically coupled through gap junctions
- cardiac muscle
- smooth muscle
5
Q
structure of skeletal muscle ?
A
- multinucleate
- striations
- voluntary - somatic nervous system
6
Q
Structure of Cardiac Muscle Cells ?
A
- single centrally located nucleus
- branched
- lots of mitochondria
- has intercalated discs - allows contact with adjacent cells
- has desosomes (mechanical strength )
- gap junctions ( allow electrical and chemical communication between cells)
- Involuntary
7
Q
Structure of Smooth Muscle Cells ?
A
- no striations
- uni-nuclear
- Spindle-shaped
- Cells are often interconnected by gap junctions
- involuntary - autonomic nervous system
8
Q
structure of sarcomere (6) ?
A
- sarcomere is distance between two Z lines
- Z line
- M line
- I band
- A band
- H zone
- titin filaments
9
Q
what is the I band ?
A
- light band, contains only actin filaments
- Z-line at its center
10
Q
what is the A band ?
A
- dark band
- myosin (thick)
11
Q
what is M line ?
A
- middle of scarcomere
- myosin filaments attched
12
Q
what is Z line ?
A
- marks the boundary of each sarcomere
- anchoring the actin filaments.
13
Q
what is the H zone ?
A
- center part of the A-Band where only myosin is present
14
Q
what are titin filaments ?
A
- elastic proteins
- keep actin + mysoin aligned
15
Q
what type of proteins are actin + myosin ?
A
- myosin= fibrillar
- actin = globular
16
Q
phases of skeletal/cardiac muscle contraction ?
A
- resting stage - ATP hydrolyzed
- Ca2+ binds to troponin
- causes a conformational change in tropomyosin
- tropomyosin leaves
- exposes myosin binding site on actin filaments
- myosin heas binds to actin forms cross-bridge
- power stroke occurs = releasing ADP+Pi and mysoin pulls actin
- causes contraction
- new ATP binds to myosin causes detachment from actin + breaks cross-bridge
- hydrolysis of ATP recocks mysoin head to original position
17
Q
contraction/ depolarisation stages ?
A
- Na+ channels open
- Na+ enters cell
- depolarisation travels down t-tubule
- causes L-Type Ca²⁺ channels to open
- influx of Ca²⁺ activates ryanodine receptors (RyR) on the SR, releasing more Ca²⁺.
-contraction activation: Ca²⁺ binds to troponin,
18
Q
relaxation/ repolarization ?
A
- Ca2+ reuptake into sarcoplasmic reticulum using Ca²⁺-ATPase pump (SERCA pump).
- withdrawal of Ca2+ to extracellular media
- exchange of Ca²⁺ out for 3 Na⁺ in with Na⁺/Ca²⁺ exchanger (NCX)
- and then Na/K+ pump exchanges 2K+ in for 3Na+ out
- activates K+ channels
19
Q
vascular smooth muscles ?
A
- walls of blood vessels
- arteries, veins + lymph vessels
20
Q
visceral smooth muscles ?
A
- airways, GI tract, urinary system
21
Q
Vascular Smooth Muscle Contraction ?
A
- excitation-depolarization due Voltage-gated L-type Ca²⁺ channels open.
- Ca²⁺-induced Ca²⁺ release from ER/SR via ryanodine receptors (RYR).
- Ca²⁺ binds to calmodulin (CaM).
- Ca²⁺-CaM complex activates Myosin Light Chain Kinase (MLCK).
- MLCK phosphorylates myosin head stimulating contraction.
22
Q
which muscle does not have a sarcomere ?
A
- smooth muscle
- still has actin myosin filaments
- contracts via Ca2+ calmodulin + myosin light chain kinase
