Slide Set 5 Flashcards
3 types of muscles
- skeletal
- cardiac
- smooth
Which muscles do we have voluntary control over?
Skeletal
Structure of skeletal muscle
multinucleated
striations
large muscle fibers
a flexor-extensor pair of muscle is called:
antagonist muscle group
Which tissue is present in skeletal muscles
connective tissue
Connective tissue components
- epimysium : covers the muscle as a whole
- perimysium : binds fascicles together and is wrapped around it
- endomysium : covers skeletal muscle fibers
Unique structure of skeletal muscle cell is due to :
- T tubules : allow electrical signals traveling along sarcolemma to move deeper in cell
- The triad : formed from a triplet of tubules, made of the sarcoplasmic reticulum, allows signal traveling along T tubule
What is the contractile unit of muscle fibres
the sarcomere
= segment of myofibril between 2 successive Z lines
what gives skeletal muscle its striations?
The A and Z bands of the sarcomere
Muscle fibers -> __ -> myofilaments
myofibrils
Myofilaments are made up of 4 different proteins
Myosin : thick filaments
Actin
Tropomyosin
Troponin
Thin filaments attach to
both Z lines of a sarcomere
What are the regulatory proteins
- nebulin : helps align actin
- titin : provide elasticity, stabilise mysosin
Globular protein that forms 2 fibrous strands that twist around each other to form bulk of thin filament is
actin
What are 2 phases leading to muscle fibre contraction
Phase 1 : motor neuron stimulates muscle fiber
Phase 2 : excitation-contraction coupling occurs
In neuromuscular junctions, motor neurons connect to sarcolemma at __
motor endplate
Neuromuscular junction
= synapse where neurotransmitter molecules transmits signals, motor neuron is in contact with muscle fiber
Which neurotransmitter is released by a motor neuron when it binds with receptors of muscle fiber
acetylcholine
Mechanism of contraction
- fiber stimulated by motor neuron releasing ACH
- electrical impulse travels from sarcolemma down the T tubule where voltage change triggers opening of the voltage gated calcium channels
- allows passive diffusion of calcium out of the SR -> triggers contraction process
What initiates a muscle action potential?
The net entry of SODIUM through ACH receptor-channel
Can muscles store ATP?
very little
Muscles store __ used to make ATP on __
phosphate
creatine
A sprinter would have which kind of fibres?
Fast-twitch glycolytic fibres (work anaerobically)
what are the types of skeletal muscle fibres?
Slow-twitch
Fast twitch : oxidative-glycolytic fibres and glycolytic fibres
Why are slow twitch fibres darker?
due to myoglobin
Cardiac muscle fibers are different to skeletal muscle fibres in that :
- they have intercalated disks
- branched fibres
- retain calcium in the SR longer, longer contraction
Smooth muscle
- small, tapered cells, single nuclei
- no T tubules
- loosely organized SR
- calcium finds to CALMODULIN
- no stations (still has thick & thin filaments)
Types of smooth muscle tissue
- single unit
- multiunit
Difference between the types of smooth muscle
single unit : have gap junctions, many cells contract as a unit
multi unit : doesn’t act as a single unit, each fiber responds to 1 nervous input
Each cell is individually enervated
= multi unit smooth muscle tissue
Smooth muscle contraction is
slower and longer
6 groups with smooth muscle
vascular gastrointestinal urinary respiratory reproductive eye
What controls smooth muscle
- hormones
- paracrines
- neurotransmitters
Where is the heart found?
in mediastinum
2 circuits in heart
pulmonary (low pressure, low resistance)
systemic (high pressure, high resistance)
Veins
carry blood to heart
Arteries
carry blood away
Heart is composed mostly of
myocardium
Which 2 factors influence arterial blood pressure by peripheral resistance ?
- blood viscosity
- diameter of arterioles
What are the 4 different valves
- 2 AV valves= atrioventricular valves (R&L)
- pulmonary and artery semilunar valves
Which valves prevent back flow from left and right atria
AV valves
thanks to chord tendinae
Which valves prevents back flow of blood
semilunar valves
__ cells receive signal from __ cells in the hear
Contractile; autorhythmic
5 major structures compose the conduction system of the heart
- Sinoatrial node
- Atrioventricular node
- AV bundle (bundle of HIs)
- Right & Left bundle branches
- Purkinje system
What is the heart’s pacemaker?
the SA node
what can be overexcited due to lack of sleep, caffeine, excess nicotine? This causes a higher depolarisation
Purkinje fibers
-> ectopic focus
What is an indicator of heart damage
cardiac troponins
