muscles

what are the 3 types of muscle

what are muscle cells and striations

• skeletal muscle

• smooth muscle

• cardiac muscle

muscle cells = myocytes

striations = stripes

what is skeletal muscle

• most common

• attaches to bone skeleton

• under VOLENTARY control

• fibres: striated, tubular and multi nucleated

smooth

• stomach, intenstine, urinary system, throughout arteries and veins plays vital role in regulation of blood pressure and tissue oxygenation ( covers walls of organs)

• no striations, uninucleated

• INVOLENTARY control

cardiac muscle

• INVOLENTARY

• contracts to pump blood around body

• only covers wallsof heart

• uninucleated

• straited

• not fatiguing ( lots of mitochondria)

major types of movement:

• flexion

• extension

• abduction

• adduction

• medial rotation

• lateral rotation

• flexion = movement decreases angle between body parts

• extension = movement to increase angle between body parts

• abduction = movement away from midline

• adduction = movement towards midline

• medial rotation = rotation towards midline

• lateral rotation = rotations away from midline

  

easy way to remember flexion and extension:

flexion = forward or folded

extension = backward or straiten

define

• actin

• myosin

• the neutransmitter that muscles use

• sarcomere

actin - thin filament

myosin - thick filament

neurotransmitter that muscles use = acetylcholine

sarcomers = basic functional units of muscle fibres that shorten to produce muscle contractions

what is sliding filament theory

muscles contract because actin filaments slide past myosin filaments pulling sarcomers shorter without the filaments themselves changing lengths

what is

• a motot uit

• neuromuscular junction

• Alpha (α) motor neurons:

include what is needed to create a large force and high precision respectively

• a motot uit = motor neuron + muscle fibres it innervates

• neuromuscular junction = synapse between motor neuron and muscle fibre

• Alpha (α) motor neurons: innervate extrafusal skeletal muscle fibres → cause contraction.

large forces need motor neurons with more muscle fibres

high precision needs more motor neurons

3 types of muscle fibres

type 1: slow, oxidative , fatigue-resistant

type 2a: fast, oxidative , intermediate metabolic properties

type 2b: fast, glycolic , fatigable

way to remember:

type 1 be SO FR

type 2 FOI

type 2 bfgf

motor unit types

differ in size of α motor neuron, number of fibres & fibre type

• slow (s) motor units

• fast-fatiguable (FF) motor units

• fast-fatigue-resistant (FR) motor units

Slow ( S) motor units (4 points)

• innervate small ‘red’ muscle fibres

• contract slowly,generate relatively small forces

• rich in myoglobin, cappillaries and mitochondria → fatigue resistant

• importnat for sustained contracts e.g. upright posture

Fast-fatiguable (FF) motor units

• large α motor neurons innervate larger, pale muscle fibres

• produce large force but sparce mitochondia → fast fatiguing

• useful for brief exertions needing large forc e.g. running

Fast - fatigue-resistant ( FR) motor units

• intermediate size motor units

• not as fast as FF → more resistant to fatigue

• generate twice force of slow( S) motor units

what is motor recruitment t

how nervous system increases muscle force by activation motor units in specific order

S→FR→FF

muscle spindles

stretch receptors within body of skeletal muscle that primarily detects changes in muscle length

• comvey length info to cns via afferent nerve fibres

• have both sensory and motor components

muscle spindle gamma motor neurons

• what do they do

• efferent signals that innervate muscles fibres ( myofibrils) in the muscle spindle

• keep muscle spindles taut and adjust sensitivity of muscle spindle

what is golgi tendon organ (GTO)

sends info about force level to spinal cord

what happens if a muscle's force level exceeds its set point

the golgi tendon organ inhibits the alpha motor neurons which innevrate the muscle, lowering force

what is the tonic vibration reflex

• sustained contraction of a muscle subject to vibration

• 30-100Hz vibration activates muscle spindles and sends inputs to afferent nerve fibres, causing muscle to contract

how can proprioceptive signals be tricked

tonic vibration illusion - vibration of muscle tendon can give illusion that the limb is moving even when it is stationary because cns interprets strong muscle spindle activity as movement

( this isnt super important)

what is H reflex (Hoffmann reflex)

electrically stimulating 1a afferents sensory fibres without activating the muscle spindles directly

what is the sliding filament theory ( 4 steps )