Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Year 1 Histology > Muscles > Flashcards

Muscles Flashcards

(80 cards)

Start Studying
1
Q

Muscle fibres comprise of several hundred ….

A

Myofibrils

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Define syncytium

A

a single cell or cytoplasmic mass containing several nuclei, formed by fusion of cells or by division of nuclei

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Features of a muscle fibres

A

Lipid droplets - fuel for respiration
Nuclei found in periphery of fibre
Lots of mito - high rate of resp

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Compare cardiac muscle to skeletal muscle

A

Cardiomyocytes form shorter fibres than skeletal muscle fibres
Cardiac muscle not built of syncytial fibres; they consist of single cells
Cardiac muscle contains single mono/dinucleated cells with limb-like extensions that allow the cells to connect to each other via intercalated discs
Centrally located nuclei in cardiac muscle; peripheral nuclei in muscle fibres
More mitochondria/capillaries in cardiomyocytes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Describe the length-tension relationship briefly

A

Amount of force exerted by a sarcomere depends on the degree of overlap between the thick and thin filaments
At full stretch , few myosin heads can attach to actin so the force exerted is weak
Beyond full contraction, the ends of the thin filament get in the way of each other and thick filaments are forced against the Z lines so force is reduced
At optimal length, all myosin head have access to actin so force is maximal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Structure of the fibres in heart walls

A

Muscle fibres arranged in several directions to achieve spiral like formation which allows the ventricles to contract in a wringing motion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are intercalated discs?

A

Connections between cardiomyocytes
Appear as dark jagged lines due to desmosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Skeletal muscle fibres have gap junctions
True or false

A

False

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Features of intercalated discs

A

Desmosomes allow longitudinal force transfer due to their strong adherence
Low resistance gap functions allow fast transfer of APs

strong adherence between fibres

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Arrangement of myosin heads in skeletal/cardiac muscle

A

Antiparallel all the way around the axis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Arrangement of myosin heads in smooth muscle

A

Antiparallel at opposite sides

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Why is the arrangement of myosin heads in smooth muscles advantageous ?

A

Allows longer sliding distances compared to skeletal muscle

higher amount of contraction can occur

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Structure of smooth muscle

A

Contraction shortens the smooth muscle cell to a fraction of its length while making it thicker

3D network of myosin, actin and intermediate filaments (not sarcomeres)

actin filaments held together by cytoskeletal proteins called dense bodies

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Smooth muscle cell features

A

Mononucleated

spindle shape

( dense network of filaments with one nucleus in the middle )

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Compare the three muscle types

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How does striation of skeletal muscle occur

A

Intermediate filaments such as desmin link Z lines laterally and myofibrils longitudinally

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Z lines are laterally linked by

A

Desmin intermediate filaments

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What proteins is mainly responsible for preventing overstretch in muscles ?

A

Titin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Role of myofibril cytoskeleton

A

Composed of mainly desmin fibres

Links myofibrils to each other

links synctycia to the basement membrane and into the surrounding connective tissue at the periphery

this allows force of contraction ti be transmitted both longitudinally and laterally

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is the endomysium ?

A

Connects to BM

Loose connective tissue with mixture of delicate/strong fibres that surrounds each muscle fibre

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is the perimysium ?

A

Mixed connective tissue , some dense, some loose, that groups muscle fibres into fascicles

where most nerves and blood vessels are found

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is the fascia ?

A

Dense layer of connective tissue that covers the muscle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is the epimysium

A

Relatively loose connective tissue between the fascia and muscle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Identify the endomysium, a muscle fibre, the perimysium, the epimysium, a fascicle and the fascia

A

perimysium surrounds the fascicle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Complete the sentences: Within muscle fibres, sarcomeres are arranged into a striated pattern by 1 _____ \_\_\_\_\_ which also transfer some of the force onto the 2 ________ , which surround the muscle fibres. muscle fibres are bundled into 3\_\_\_\_\_\_ which are surrounded by 4\_\_\_\_\_\_\_ the muscles are packed by 5 \_\_\_\_\_
1 intermediate filaments 2 endomysium 3 fascicles 4 perimysia 5 fascia
26
Which structures within a muscle are visible by naked eye ?
Fascicles can be seen as stripes
27
What are motor end plates
Where a motor neurone synapses with a muscle fibre 1 synapse per muscle fibre
28
Can AP be generated between muscle fibres?
No, AP can only be generated by motor end plates ; there are no gap junctions between muscle fibres
29
What is proprioception?
Sesnors in muscle fibres for stretch and speed of movement work in association with sensory neurones to allow your body to sense movement, action, and location
30
What is a motor unit ?
Refers to the motor neurone and the several hundred muscle fibres it attaches to each motor neurone synapses with the same muscle fibre type
31
What is the size principle
The idea that type 1 fibre motor units are recruited first if more force is required , type 2 motor units recruited
32
What is the difference between different fibre types ?
The isoform of myosin present
33
Describe structure of NMJ
Only present in skeletal muscles not cardiac muscle
34
State events that occur during chemical transition at a NMJ
1. AP arrive at presynaptic bouton 2. depolarisation of presynaptic membrane = voltage gated Ca2+ channels open 3. calcium-mediated exocytosis of ACh into synaptic cleft 4. ACh interacts with nAChR on sarcolemma 5. Conformational change of nAChR ; influx of Na+ into muscle cell ; effluent of K+ Via nAChR ; Receptor Generated Potentials (RGPs) formed 6. If RGPs exceed threshold , AP is generated; this AP is called an End Plate Potential (EPP) 7. EPP propagated down muscle ; release of Ca2+ Into cytosol from SR ; muscle contracts
35
Adaptations of muscles that require fine muscle control
1:1 ratio of motor neurone to muscle fibre
36
Explain Ca2+ regulated release of ACh
AP arrives at axon terminal terminal membrane depolarises voltage gated Ca2+ open Ca2+ diffuse into presynaptic bouton down conc grad this causes exocytosis of secretory vesicles of ACh
37
How is the capacity for detection of ACh release at the motor end plate enhanced?
Many more nAChR proteins present in sarcolemma than ACh molecules release by a single AP
38
What type of receptor are nAChR receptors ?
Ionotropic
39
How many NMJ does each myocyte have ?
One one presynaptic AP leads to one post-synaptic AP
40
describe how the neurones recover after an AP is initiated
* enzymes found in the synaptic cleft break down the neurotransmitter * acetyl cholinesterase AChE hydrolyses ACh * ACh→ acetic acid + choline * these products diffuse across synaptic cleft back to presynaptic knob where they are recombined to from the neurotransmitter again * this requires ATP * this causes the neurotransmitters to no longer be complementary to receptor sites so the neurotransmitter is removed from nAChR in postsynaptic membrane * NAChR therefore close * Na+/K+ pumps work to restore resting potential
41
What is myasthenia gravis
Autoimmune disease of NMJ autoantibodies against nicotine AChR = trouble with initiating muscle contractions
42
How is MG treated
**inhibition of AChE via drugs ; prolong time ACh is present in cleft ; increase chances of binding to receptors and causing AP**
43
What is quantal exocytosis
Small quanta (packets ) of ACh are released at rest as voltage-gated Ca2+ channels are inefficient this causes a small membrane depolarisation called miniature EPP (mepp)
44
What happens inside a myocyte after muscle contraction occurs ?
Ca2+ are removed from cytosol and returned to the SR by ATP-Ca2+ pumps
45
How does an ACh binding to receptors of the postsynaptic membrane cause muscle contraction
ACh binds to nAChR = epp = volatge gated Na+ channels = depolarisation to threshold = AP generated AP travels down T-tubules to SR AP communicates ryanodie receptor Ca2+ released by SR via voltage gated Ca2+ channels muscle contraction
46
compare type 1 and type 2 fibres in terms of : contraction time size of motor unit resistance to fatigue max duration of use force produced mitochondrial density capillary density glycolytic capacity myosin heavy chain human gene
47
Function of muscle spindles
Innervated by γ motor neurons ; provide info about length changes of muscle
48
Function of golgi tendon organs
Provide information about the strength of a muscles contraction
49
What are satellite cells?
Myoblasts that remain in muscle fibres to act asa stem cell reserve in case damage to myonuclei/muscle fibre occurs
50
Adaptation of skeletal muscles to exercise
Endurance training = Increased mito Resistance training = muscle hypertrophy = more myofibrils within fibres
51
How do satellite cells replace fibres ?
Cell fusion to syncytium , myofibril synthesis and maturation
52
How much blood is expelled from heart every heart beat
Around 70% in a healthy person
53
Two main features of heart
Constant contraction Synchronous muscle activation in ventricles
54
Name the 2 ways to increase function of heart
Inotripy - increased force of contraction = higher SV chonotropy = increased frequency of contraction = increased HR
55
Difference between AP in skeletal muscle and cardiac muscle
Duration of cardiac AP is much longer shorter AP in skeletal muscle allows more control over its contraction
56
How is cardiac muscle adapted to achieve synchronous contractions of the heart
longer AP to avoid tetanus in cardiac muscle (tetanus is prolonged contraction of a muscle caused by rapidly repeated stimuli - you want cardiac muscle to contract with same short duration and power each time) Longer AP achieved by plateau in AP due to influx of L-type Ca2+ channels (L for long-opening) to delay repolarisation this allows twitch contraction of the muscle
57
muscle force in a single myocyte regulated is regulated by ...
Frequency of action potentials summation - no time for muscle to relax before new contraction so prolonged muscle contraction
58
Muscle paralysis occurs when ....
No action potentials are initiated in the muscle
59
How is neuromuscular blockade useful?
Prevent muscle contractions Maintain muscle relaxation/paralysis without the need of deep general anaesthesia surgery (inc. cosmetic )
60
What are the 4 ways to prevent neuromuscular transmission ?
1. Prevent ACh synthesis by inhibiting choline uptake - no clinical use , slow effect and slow to reverse 2. prevent exocytosis of ACh e.g botulinum toxin prevents vesicles from fusing with membrane 3. block receptors e.g nicotinic receptor antagonists 4. increase reuptake/inactivation of AChE
61
Botox - clinical uses
* Treat cervical dystopia (neuromuscular movement disorder involving head and neck) * treat blepharospasm (involuntary eye muscle contractions ) * treat primary auxiliary hyperhidrosis (excessive sweating )
62
Explain how non-depolarising agents work include details about : Onset ; Duration ; mechanism of action ; is block preceded by stimulation of muscles?
Non-depolarising agents work by competing for the receptor binding sites on nAChR; this is called competitive antagonism longer duration ~ 30 mins relatively fast onset of effect ~ 3-5 mins Block is not preceded by stimulation of muscles During block high freq stimulation causes tetanus with slightly onset duration of twitch (called tetanic fade)
63
Agonism vs antagonism
Agonism = activates receptor Antagonism = deactivates receptor
64
Anticholinesterases can be used to ....
Reverse neuromuscular blockade due to action of antagonists
65
Explain how depolarising agents work include details of: Mechanism of action : onset ; duration ; use ; is its blocking effect preceded by muscle stimulation?
work by leaving the nAChR permanently open ; they mimic shape of ACh or nicotine (which both fit receptor sites on nAChR) new APs cannot be formed as overwhelms voltage gated Na+ channels ; rapid onset \<1min ; short duration ~ 5 min ideal for quick procedures e.g intubation , ECT(electro convulsive therapy) and dislocation Block preceded by muscle twitches
66
What happens upon high freq stimulation of non-depolarising block
Tetanus with duration only slightly longer than a twitch called tetanus fade
67
What happens upon high freq stimulation of depolarising block
68
How can you antagonise a non-depolarising block ?
Using agents that depolarise the sarcolemma drugs that increase ACh release e.g adrenaline / 4-aminopyridine anticholinestersases (AChE inhibitors )
69
name 3 common nACh-R antagonist/non-depolarising blockers
atracurium vecuronium gallamine
70
name 2 nACh-R agonist/depolarising blockers
suxamethonium dexamethonium
71
name 2 common ACh-esterase inhibitor (“anticholinesterase”)
physiostigmine neostigmine
72
What is Ca induced Ca release (CICR) ?
L-type Ca2+ channels are very close to ryanodine receptors on SR Ca2+ influx during cardiac AP results in Ca2+ release by SR small increase in [Ca2+]i Ca2+ then re-sequestered by SR via Ca2+ATPase pump and then expelled from cell by Na+/Ca2+ exchange
73
difference between calcium handling apparatus in cardiac vs skeletal muscle
skeletal - thin t-tubules, thick SR, triads ( each t-tubule connects with 2 SR membranes) ; cardiac - thick t-tubules, thin SR, diads ( each t-tubule connects with 1 SR membrane)
74
What is the effect of increasing the diastolic length of the cardiac myocyte
Increases sensitivity of myocyte to Ca2+ = more powerful heart contraction
75
What does inotrope mean
Agent that alters the force of muscle contraction
76
How do positive cardiac inotropes work
E.g caffeine cause more Ca2+ release from channels of the SR
77
How do negative inotropes work? how do they help reduce angina/blood pressure
Block L-type Ca2+ channels Reduced contraction = lower energy demand and blood ejected at lower force
78
Cardiac muscle needs ATP for
The myosin heads to detach and reset it forward
79
Energy sources of cardiac muscle
Mostly fat then glucose then lactate,glycolysis and ketones
80
Describe cardiac muscle mitochondria
They have continuous reticulum 2 distinct population : * interfibrillar - provide ATP for muscle contraction * subsarcolemmal - provide ATP for ATP-dependant processes in the AP

Year 1 Histology (10 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions