lecture 17 - muscle histology Flashcards
What are the 3 types of muscle?
skeletal, cardiac, smooth
What are the 2 types of striated muscle?
skeletal, cardiac
What are the 2 types of involuntary muscles?
cardiac, smooth
What are the units within a skeletal muscle, from biggest to smallest?
muscle, fascicle, muscle cell/fibre, myofibril, myofilaments
Are skeletal muscle fibres branched or unbranched?
unbranched
What is the shape and orientation of muscle cell nuclei?
oval, periphery, multiple nuclei
What is the term for the cytoplasm of a muscle cell?
sarcoplasm
What is the term for the plasma membrane of a skeletal muscle cell?
sarcolemma
What is the outer layer of a muscle cell?
basal lamina
What is the basil lamina of a muscle cell?
A connective tissue/collagen covering on top of hte sarcolemma
What is a skeletal muscle triad?
A group of 3 vessels that goes deep into the muscle fibre from the surface, made up of a T-tubule and 2 terminal cisternae of the sarcoplasmic reticulum
What are the components of a skeletal muscle triad?
1 T-tubule, 2 terminal cisternae
What are skeletal muscle T-tubules?
Invaginations of the sarcolemma that penetrate between the myofibrils in a transverse plane
What are skeletal muscle terminal cisternae?
Expanded sacs of sarcoplasmic reticulum that penetrate in between the myofibrils
Which sarcolemma band is a T-triad located at in skeletal muscle?
the A band
What is the boundary of a sarcomere at each end?
Z line
What is a sarcomere?
A single contractile unit of a myofibril
What proteins make up myofibrils?
Actin (20%), myosin (60%), other proteins (20%)
What is the I band of a sarcomere?
Isotropic band - The part of either side of a Z disc formed by non-overlapping parts of actin/thin filaments
What is the A band of a sarcomere?
Anisotropic band - band with thick filaments plus the overlapping ends of thin filaments, including the H zone in the middle which just contains non-overlapping thick filaments.
What is the H zone of a sarcomere?
The central non-overlapping zone of thick filaments in the middle of a sarcomere
What is the line that marks the centre of a sarcomere?
M line
How many neurones can innervate a single muscle cell?
Only 1
What is the name for motor terminals of motor neurones on muscles?
Motor end plate
What is the process of muscle contraction, from action potential to cross bridge cycling?
1.) action potential at neuromuscular junction / motor end plate
2.) depolarisation of sarcolemma
3.) propagation of depolarisation down T-tubules
4.) Ca2+ release from terminal cisternae
5.) Ca2+ binding to troponon, displacing tropomyosin and exposing myosin binding sites
6.) cross bridge cycle
What happens to the length of the I band during contraction?
Shortens
What happens to the length of the A band during contraction?
remains the same
What happens to the length of the H band during contraction?
shortens
What protein anchors actin to the outer basal lamina in a myofibril?
Dystrophin
What protein is absent in Duchenne’s muscular dystrophy?
Dystrophin
What are the 5 layers of connective tissue coverings of the layers within a muscle?
Outer to inner: Fascia, epimysium, perimysium, endomysium, basal lamina
What type of collagen is found in the epimysium?
Collagen Type I
What connective tissue layer contains muscle spindles?
Perimysium
What connective tissue layer contains capillaries and nerve fibres?
Endomysium
What connective tissue layer is the site of metabolic exchange?
The endomysium
What is the function of muscle spindles?
They are mechanoreceptors essential for proprioception - sensitive to stretch
Where are muscle spindles located?
In between muscle fascicles
What connective tissue layer covers a muscle spindle?
A capsule, which is an extension of the perimysium
What are the small muscle fibres within the fuse/spindle of a muscle spindle?
IFF - intrafusal fibres
What are extrafusal fibres of a muscle spindle?
The normal muscle fibres found outside the capsule of a muscle spindle
What is the process of muscle spindle activation?
muscle stretch causes change in muscle length,
force converted to capsule,
afferent nerve stimulation,
transmission to spinal cord,
extrafusal muscle activation and contraction
What cells are found on the periphery of muscle fibres and aid in repair?
Satellite cells
Where are muscle satellite cells located?
Periphery of muscle fibres, between sarcolemma and basal lamina
Why are muscle satellite cells normally inactive?
They are involved in muscle repair, but only in early postnatal life or in acute injuries.
What tissue makes up tendons?
Regular dense fibrous connective tissue
What cells produce tendon matrix?
Tenocytes
Where is the tendon blood/nutrient supply derived from?
The external connective or synovial tissue
What is a myotendinous junction?
A place where muscle fibres and tendons interlock/attach
How are muscles fibres and tendons attached at myotendinous junctions?
Specialised proteins connect actin of last sarcomere to sarcolemma, basal lamina and then tendon collagen
What is an osteotendinous junction?
The point where tendons and bones are connected
What allows bone and tendons to interlock at an osteotendinous junction?
Fibrous or fibrocartilaginous insertions
