0428 - Muscle Histology - EG Flashcards
Define each of the three muscle groups as either voluntary/involuntary and striated/non striated
Voluntary - skeletalInvoluntary - smooth, cardiacStriated - skeletal, cardiacNon-striated - smooth
The plasma membrane of skeletal muscle is known as?
sarcolemma
The cytoplasm of skeletal muscle is known as?
sarcoplasm
The endoplasmic reticulum of skeletal muscle is known as?
sarcoplasmic reticulum
muscle fibres are surrounded by?
endomysium
Muscle fibres are arranged into bundles known as what?
fascicles
Fascicles are surrounded by?
perimysium
The muscle belly is surrounded by?
epimysium
Why are muscle cells multinucleated? Where are the nuclei found?
Because many myoblasts fuse together to form a single muscle cell. The nuclei are found peripherally.
List some contrasting features between type 1 and type 2 skeletal muscles.
Type 1 - slow contraction, aerobic, use oxidative phosphorylation, have many mitochondria and large amounts of myoglobin which give a red colour.Type 2 - Fast contraction, anaerobic, use glycolysis, rich in glycogen, have a white colour.
If stained muscle using a succinic dehydrogenase stain or NADH-TR stain, how are type 1 and type 2 muscles distinguished?
type 1 fibres stain dark and type 2 fibres stain pale.
What makes a muscle appear striated?
The ordered arrangement of myofibril contractile proteins.
The dark A band of a sarcomere represents?
section containing thick myosin filaments
The light I band of a sarcomere represents?
section containing thin actin filaments
The Z bands anchor which filaments?
actin filaments
Which bands of the sarcomere become narrower with contraction?
I and H bands
What is a motor unit?
A motor neuron and the muscle fibres it supplies.
What is the neurotransmitter released at the neuromuscular junction?
acetylcholine
Duchenne Muscular Dystrophy is inherited via what type of simple Mendelian inheritance? What is the protein affected?
x-linked disorder, results in abnormalities in the gene encoding dystrophin protein, which normally concentrates at the plasma membrane over Z bands where it links to cytoplasmic actin. Results in degeneration of muscle fibres and proliferation of endomysial connective tissue.
Where is the nucleus in smooth muscle cells?
Central.
In comparison to skeletal muscle which has Z lines, what do smooth muscle cells have?
Dense bodies which act as anchor points in the cytoplasm, and attachment junctions, which act as anchor points on the cell membrane.
How are the contractile proteins arranged in smooth muscle? What happens when they contract?
In a criss-cross arrangement, so when contract the cell goes from an elongated shape to a plump shape.
What is the difference between single unit (unitary)smooth muscle and multiunit smooth muscle? What are some examples of each type?
Single unit cells have extensive communications via gap junctions between adjacent cells so that they can contract as a single unit, examples in the gastrointestinal tract and uterus.Multiunit cells are independent from their neighbours and are capable of finer control, such as ciliary muscles of the eye and piloerector muscles of skin.
What is the difference between phasic and tonic contraction?
Phasic refers to the muscle exhibiting rhythmic or intermittent activity, often by single unit type muscle.Tonic referes to the muscle continuously maintaining a level of tone, for example in blood vessels, often by multiunit type muscle.
Compare and contrast cardiac myocytes with skeletal and smooth muscle cells.
Cardiac myocytes similar as elongated cells, have central nuclei like smooth muscle yet are also striated with sarcoplasmic reticulum and T tubules similar to skeletal muscle. Cardiac muscle is unique with branching fibres and intercalated discs
What is the function of intercalated discs?
Specialised junctions between cells permit the rapid spread of contractile stimuli due to areas of low electrical resistance, so the fibres can contract almost simultaneously.
What are the 3 types of membrane contacts from which intercalated discs arise?
Fascia adherens - sites of actin filament insertionDesmosomes - anchor intermediate filamentsGap junctions - pores with low electrical resistance for ion transfer
Cardiac muscle is innervated by the autonomic nervous system - what is the effect of sympathetic and parasympathetic stimulation?
sympathetic increases heart rate, while parasympathetic decreases heart rate.
What is hypertrophic cardiomyopathy?
myocardial dysfunction due to haphazard hypertrophy of myocytes and interstitial fibrosis, causing overal myocardial hypertrophy.
