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Skeletal Muscle Structure And Function Flashcards

1
Q

What are smooth muscles

A

Smooth muscles line hollow organs (e.g. gut, blood vessels). They are involuntarily controlled

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2
Q

What are cardiac muscles

A

Muscles located in the heart. Responsibly for the contractility of the heart and hence flow of blood around the body. They are under involuntary control

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3
Q

What is skeletal muscle

A

Muscle that applies force to the bones of the skeleton to produce movement and control posture. It is under voluntary control

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4
Q

How many directions do skeletal muscles generate force in

A

One - shortening/contracting

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5
Q

What are the 4 secondary jobs of skeletal muscle

A

Support and protection for internal organs (e.g. muscles of abdominal wall)
Provides voluntary control over major openings of the body
Converts energy into heat (used to maintain core temp)
Provides major store of energy and protein

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6
Q

What type of tissue ensheathes muscle fibres and connects them to bones

A

Connective tissue

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7
Q

What two systems is skeletal muscle richly linked with

A

The vascular system (rich supply of blood vessels)
The nervous system (richly supplied with nerve fibres)

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8
Q

Outline the whole muscle structure

A

Muscle fibres are gathered into bundles called fascicles
Fascicles are gathered into bundles called muscles
Fibres, fascicles, and muscles are each ensheathed in connective tissue
Tendons connect muscles to bone

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9
Q

What are the 4 major components that make up muscle

A

Muscle tissue, nerves, blood vessels, and connective tissue

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10
Q

What are muscle fibres

A

Muscle cells

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11
Q

What are the 3 connective tissues involved in the muscle structure

A

Endomysium- surrounds each muscle fibre
Perimysium - surrounds each fascicle (bundle of myofibrils)
Epimysium - surround entire muscle

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12
Q

What are myofibrils

A

A basic rod like organelle of a muscle cell

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13
Q

Outline the structure of the individual cell fibres

A

Muscle fibres are encapsulated by the sarcoplasmic reticulum and surrounded by transverse tubules
A muscle fibre is comprised of bundles of myofibrils
Myofibrils are made of repeating units called sarcomeres
Sarcomeres are made of contractile proteins or myofiaments

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14
Q

What are the two myofilaments

A

Actin - thin filaments
Myosin - thick filaments

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15
Q

What gives muscle its striated appearance

A

The orientation of Actin and Myosin filaments

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16
Q

How is the activity of force producing elements controlled

A

Transverse tubules conduct electrical signals (action potentials) deep into the core of the fibre

17
Q

What are transverse tubules

A

Tubular extensions (invaginations) of the surface membrane

18
Q

What is the sarcoplasmic reticulum

A

An extensive membranous tubular network associated precisely with the T tubules at regular intervals

19
Q

What is a membrane triplet triad

A

Where the terminal chambers of the sarcoplasmic membrane associate with the transverse tubules to form a membrane triplet called a triad

20
Q

What is the function of the sarcoplasmic reticulum

A

To take up and store Ca, then release Ca2+ into the cytoplasm on receipt of an action potential along the associated transverse tubule

21
Q

Outline what contributes to the sarcomeric structure

A

The arrangement of contractile proteins
Thick filaments (primarily myosin) interlace with thin filaments (primarily actin)

22
Q

What is actin

A

A globular protein (G-actin). Globules assemble to form filamentous protein strands

23
Q

What is myosin

A

A molecule that has a long tail and a globular head
Myosin heads are able to “flex”

24
Q

What is the thick filament made of

A

Formed from arrays of pairs of myosin molecules arranged with the tails pointing towards the m line and forming a complex double helix structure

25
Q

What is a thin filament

A

Each thin filament is a twisted strand of 2 rows of F-actin actin terminating at one end of the Z line

26
Q

Summarise the muscle structure

A

Sarcoplasmic reticulum - a mesh like network that is interconnected and wraps around each myofibril - functions as Ca2+ storage
Transverse tubules are regularly spaced and associated with the Sarcoplasmic reticulum
Terminal cisternae of the SR and the Transverse tubules form structure know as the triad

27
Q

Summarise the muscle at a cellular level

A

A single muscle fibre is a single muscle cell
Each fibre is made of multiple myofibrils
The repeating unit in a myofibril is a sarcomere
Sarcomere contains thick and thin myofilaments (contractile proteins)

28
Q

How do electrical events in the brain trigger muscle force production

A

Action potentials arise in the brain, are conducted down spinal cord to motor neurons in spinal cord. Action potentials in spinal cord motor neurons are conducted out of CNS along motor axons to muscle fibres

29
Q

What is the neuromuscular junction

A

Where the myelinated axon of a motor neuron terminates at a single point on the muscle fibre

30
Q

What is a motor unit

A

The motor neuron and all the muscle fibres it controls

31
Q

What is the M line

A

Connects the central portion of each thick filament

32
Q

What is the Z Line

A

Mark boundries between adjacent sarcomeres. Proteins called actinins interconnect thin filaments of adjacent sarcomeres

33
Q

What is the structure of troponin

A

Consist of three globular subunits
One binds to tropomyosin forming troponin-tropomyosin complex.
One binds to G actin, holding troponin-tropomyosin complex in position
Third subunit has receptor that binds two calcium ions

34
Q

What is the sliding filament theory in terms of bands

A

The H bands get smaller
The zones of overlap get larger
The Z lines move closer together
The A bands remain constant

35
Q

What is acetylcholine

A

A neurotransmitter; a chemical released by a neuron to change the permeability or other properties of another cells plasma membrane

36
Q

What is the relation between acetylcholine and acetylcholinesterase

A

Acetylcholine is stored in vesicles within the axon cytoplasm. Acetylcholine changes the permeability or other properties of other cells plasma membrane
Acetylcholinesterase is an enzyme that breaks down acetylcholine. It is in the synaptic cleft and and the sarcolemma (muscle cell plasma membrane)

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