Physiology 1 and 2 Flashcards by ariannewhiteside@outlook.com Whiteside

What are the striated muscles

Skeletal and cardiac

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What makes the muscles striated?

Alternating dark thick myosin bands and light thin actin bands

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What are skeletal muscles innervated by

the somatic nervous system - subject to voluntary control

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What are cardiac and smooth muscles innervated by

Autonomic nervous system - involuntary

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How does initation of contraction come about in skeletal and cardiac muscle

Neurogenic by skeletal muscle, and myogenic by cardiac

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How does calcium enter cells in skeletal and cardiac muscle

In skeletal muscle, entirely from SR - in cardiac muscle from ECF and SR (Calcium induced Ca release)

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What is the transmitter at the neuromuscular junction

Acetylcholine

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What is a motor unit

A single alpha motor neurone and all the skeletal muscle fibres it innervates

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Where is precision more important than power

Extra ocular muscles, few muscle fibres per motor unit

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What exists inside a muscle fibre (one cell)

Myofibril and sarcomere

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How are skeletal muscles usually attached to bones

by tendons

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What are the functional units of muscle

Sarcomeres

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What are myofibrils

Specialised contractile intracellular structures

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What is a functional unit of any organ defined as

the smallest componenet capable of performing all the functions of that organ

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Where is the sarcomere found

between two Z lines

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What is the A band

made up of thick filaments along with portions of thin that overlap in both ends of thick filaments

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What is the H Zone

lighter area within middle of A band where thin filaments don’t reach

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What is the M line

Extends vertically down middle of A band within the centre of H zone

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What is the I Band

Consists of remaining portion of thin filaments that do not project in A Band

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How is muscle tension produced

By sliding of actin filaments on myosin filaments

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What is force generation dependent upon

ATP dependent interaction between thick and thin filaments

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What is ATP required for

both contraction (to power cross bridges) and relaxation (release cross bridges and pump calcium back into SR) of muscle

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What is Calcium required for

to switch on cross bridge formation

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What is excitation contraction coupling

the process whereby the surface action potential results in activation of contractile structures of the muscle fibre

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Where is calcium released from in skeletal muscle fibres

Lateral sacs of the sarcoplasmic reticulum

When is calcium released from skeletal muscle fibres

When the surface action potential spreads down the transverse T tubules

What are T tubules

Invaginations of the surface membrane that dip into the muscle fibre

What is motor unit recruitment

a stronger contraction achieved by stimulation of more motor units

What are the two primary factors which changes the gradation of skeletal muscle tension

Number of muscle fibres contracting within the muscle and tension developed by each contracting muscle fibre

In skeletal muscle, what relation does the duration of the action potential have to the resulting twitch

the duration of the action potential is much shorter than the duration of resulting twitch

Why can cardiac muscle not be tetanised

The long refractory period prevents generation of tetanic contraction

What is tetanus

A maximal sustained contraction achieved by summation of action potentials

Is a single twitch useful in bringing about meaningful muscle activity

No its not

How can maximal tetanic contraction be achieved

When the muscle is at its optimal length before the onset of contraction

When in the body are skeletal muscles at their optimal length

At their resting length

What are the two types of skeletal muscle contraction

Isotonic and isometric

What is isotonic contraction used for and what is it

Body movements and moving objects, muscle tension remains constant as the muscle length changes

What is isometric contraction and whats it used for

Muscle tension develops at a constant muscle length, used for supporting objects in fixed position and maintaining body posture

What happens to the velocity of muscle shortening as the load increases

It decreases

What are the 3 main metabolic pathways that supply ATP in muscle fibre

Transfer of high energy phosphate from creatine phosphate to ADP, oxidative phosphorylation, glycolysis

What is an immediate source for ATP

Transfer of high energy phosphate from creatine phosphate to ADP

What is the main source for ATP when oxygen is present

oxidative phosphorylation

What is the main source for ATP when oxygen is not present

Glycolysis

What are the 3 types of skeletal muscle fibres

Slow-oxidative, fast-oxidative, fast glycolytic

What are slow oxidative type 1 fibres (slow twitch) used for

prolonged relatively low work aerobic activities eg. posture, walking

What are fast oxidative type 2a (intermed twitch) fibres used for

prolonged relatively moderate work activities eg jogging (use both aerobic and anaerobic)

What are fast glycolytic type 2x fibres (fast twitch) used for

anaerobic metabolism, short term high intensity activities eg. jumping

What is a reflex action

a stereotyped response to a specific stimulus - the simplest form of coordinated movement

What is the simplest monosynaptic spinal reflex

Stretch reflex

Sum up a stretch reflex

Serves as a negative feedback that resists passive change in muscle length to maintain optimal resting length of muscle

Where is the sensory receptor located in musc;e

in the muscle spindle, activated by muscle stretch

What effect does stretching the muscle spindle have

increases firing in the afferent neurones, which synapse in the spinal cord with alpha motor neurones (efferent) - activation of the reflex results in contraction of stretched muscle

What are muscle spindles

the sensory receptors for stretch reflex, collection of specialised muscle fibres

What are muscle spindles also known as

intrafusal fibres

what can ordinary muscle fibres be known as

extrafusal fibres

Where are intrafusal fibres found in the muscle

The belly

What are annulospiral fibres

the sensory nerve endings on muscle spindles

What is the efferent motor nerve supply to muscle spindles called

gamma motor neurones

does the contraction of intrafusal fibres contribute to the overall strength of muscle contraction

What is the role of gamma motor neurones

They adjust the level of tension in the muscle spindles to maintain their sensitivity when the muscle shorten during muscle contraction

Some useful investigations in neuromuscular disease

Electromyography, nerve conduction studies, muscle enzymes CK, inflammatory markers, muscle biopsy

What is myalgia

muscle pain

What is myotonia

Delayed relaxation after voluntary contraction

What are two main causes of intrinsic muscle disease

Genetically determined, acquired