MODULE 3: Support and Movement Flashcards
Muscle Types
skeletal, smooth, caridac
Smooth Muscle
- found within walls of gastrointestinal tract
- facilitates digestion via contraction
- non striated and parallel
- also found in blood vessels, lymphatic vessels, urinary bladder, uterus, male and female reproductive tracts, respiratory tract, skin and iris
Cardiac Muscle
- only found in contractile walls of heart
- striated and branched
- contractile properties
- muscle fibres interconnect at intercalated sidk
- allows electrical signal to pass from one cell to another
- helps syncronise heart muscle contraction
- uni-nucleate
Skeletal Muscle
- makes up 40-50% of body mass
- striated and stripes
- sarcomeres shorten suring contraction
- muscle cells/fibres are long and multi-nucleate
- multiple nuclei allow repair and growth all the way along fubre
- controlled by somatic system
Function and Structure of Skeletal Muscle
- 320 different skeletal muscles in humans x 2 sides
- muscles used for postural, fine motor and gross motor control
Contractility: ability to shorten and thicken to develop tension
Excitability: ability to respond to appropriate stimuli
Extensibility: ability to be stretched without damage
Elasticity: ability to store energy and recoil to resting length
- connective tissue dispersed throughout fibre
- muscle is made up of a large number of fasicles (bundles) of fibres surrounded by connective tissue
Sarcomeres
- contains a series of thick and thin filaments that move in relation to each other
- form adjacent myofibrils line up which gives striated appearance
- thin filaments (actin) attach at Z-line
- thick filaments (myosin) anchor at M line in centre of sarcomere
- Z line to Z line = sarcomere
- at rest, actin and myosin slightly overlap
- contraction = more overlap
- elastic filament: titin anchors myosin to z line and contributes passive force
- myosin and actin are fine protein strands
- heads on myosin have actin binding sites to pull actin for contraction
draw diagram
Cross Bridge
linked myosin head and actin filaments
Power Stroke
attachment and pull producing force
Connective Tissue
Endomysium: surrounds each muscle fibre
Epimysium: fibrous tissue that surrounds skeletal muscle
Perimysium: groups muscle fibres into a fasicle
The Motor Unit
- connection b/w nervous system and skeletal muscle
- smallest functional unit in musculoskeletal system
- motor unit = 1 motorneuron, its motor axon and all muscle fibres it innervates
- action potential generated in motor neuron generates an action potential in motor units muscle fibres
- force altered by number and discharge rate of motor units and contractile properties of muscle fibres
Muscle shapes
- affects action of muscle
- circular muscles can close an opening
- long muscles are better at controlling movement over joints that have a large range of motion
- shorter/wider muscles are better at generating larger forces over small range of motion
Cross-Sectional Area
- greatest predictor of force is physiological cross sectional area
PSCA = (muscle volume) / (fibre length)
Sarcomere Length and Myofibrils
- inside each muscle fibre is a bundle of myofibrils that lie in parallel
- contractile filaments that convert the electrical signal (AP) initiated in the nervous system to muscle force are within myofibril
- a series of sarcomeres make up each myofibril
Muscle Tendon Unit
Contractile Component (CC) - muscle fibres, actin and myosin cross bridges
Series Elastic Component (SEC)
- intracellular titin, tendon
Parallel Elastic Component (PEC)
- connective tissue, epimysium, perimysium, endomysium and passive cross bridge connections
Length Tension Relationship
- Sarcomere length influences force that can be developed
- optimal sarcomere length is 80-120% of resting sarcomere length
Discharge Rate
- force influenced by discharge rate of active motor units
- slow twitch: less force and longer duration
- fast twitch: more force and shorter duration
- easier to have summation of slow twitch
Axial Skeleton
- related to head and trunk of body
- 80 bones
- skull, rib cage,vertebral column
Appendicular
- relates to limbs
- 126 bones
- shoulder girdle, arm, upper limb, hands
- pelvic girdle
- lower limb, foot
Sagital / Parasagital
- divides body into left and right
- parallel w/ sagital (left and right but not equal)
Coronal
divided body into posterior and anterior
Sagital Plane
Transverse: divides into cranial and caudal (superior and inferior)
Flexion: decrease joint angle
Extension: increase joint angle
Dorsiflexion
raise foot
Plantarflexion
lower foot
Abduction / Adduction
away from body / towards body
Supination / Pronation
palm up / palm down
Lateral / Medial
external rotation / internal rotation
Joint Structures
Fibrous:
- contain fibrous connective tissue
- some cannot move (skull)
- some allow a little movement (depends on length of connective tissue)
Cartilaginous:
- contain cartilage
- cushions force
- allow little bit of movement
Synovial:
- have a space b/w adjoining bones
- synovial capacity filled with fluid
- largest range of motion
Synovial Joints
Hinge:
- restrict movement to a single plane
- b/w head and humerus, ulna, knee, fingers
Ball & Socket:
- enable arms and legs to rotate and move in external planes
- shoulder, hip
Pivot:
- rotating forearm at elbow
- head side to side
Antagonist Muscle Pairs
- muscles apply opposing force to perform joint movement (bicep and tricep)
Agonist Muscle Pairs
help perform same joint movement (quad)
Long Bone
- shaft with ends
- important for leverage and movement
- femur, phalanges etc
Short Bone
- square shaped
- important for fine movements
- carpals, tarpals, patella, etc
Flat Bone
- important for protection
- hematopoiesis (make blood)
- sternum, scapula, ribs etc
Irregular Bone
- important for protection, support, movement and hematopoiesis
- vertebrae, pelvis etc
Make up of Bones
Collagen - 40% dry weight - toughness and flexibility Calcium & Salts - 60% dry weight -hardness and rigidity - laid down b/w collagen fibres
Osteogenic Cells
- bone cells
- stem cells
- develop into osteoblast then osteocyte
Osteoclasts
- bone cells
- very large with many nuclei
- improves reabsorption efficiency
- respond to mechanical stress
- “dig tunnels” to be lined with collagen by osteoblasts
Osteocytes
- maintain bone matrix
- hold bone together
- mineralise bone matrix
- long cytoplasmic extensions
- nutrients to bone matrix
Osteoblasts
- line tunnel with collagen
- create bone matrix (build bone)
- located on bone surface
- differentiate into osteocytes when trapped in bone
Bone Types
Compact Bone:
- lamellar or cortical
- hard and dense
- support body
- stores calcium
- organised structure
Trabecular Bone:
- spongy
- greater surface area
- promotes bone marrow to develop
- trabeculae form along lines of stress
Primary / Secondary Ossification Centres
primary: form ~ 8 weeks after bone formation
secondary: present after birth until growth stops. involves developing ends of bone
Stages of Bone Development
- resting cartilage
- cartilage proliferation (hyperplasia - cells multiplying)
- cartilage maturation (hypertrophy)
- cartilage calcification (extracellular matric becomes calcified
- ossification (osteoblasts form bone)
draw diagram
Skeletal Decay
Trabecular:
- decrease in no. of traberculae (small rods within bone) with age
- bone cannot absorb as much energy without fracture
Osteoporosis:
- low bone density
- less able to absorb mechanical force
- increase fracture risk
Action Potentials in Muscles
- myo (muscle) electic APs are initiated by ACh released by the motor neuron
- ACh binds to proteins on muscle cell membrane, triggering myoelectric AP
- AP sweeps along the muscle fibre and into the transverse (T) tubules
- AP potential triggers Ca2+ release from sarcoplasmic reticulum into cytosol
- calcium ions binds to troponin in actin —> myosin binding sites exposed
- if ATP is bound to myosin, concerted to ADP + energy –> myosin in active state –> power stroke
- cycles of myosin cross-bridge formation and breakdown coupled with ATP hydrolysis, slide actin towards M line
- ADP leaves myosin. another ATP binds to myosin and returns to relaxed state. power stroke begins again when ATP is hydrolysed
- cytosolic Ca2+ removed by active transport into SR after AP ends
- tropomyosin blockage of myosin binding sites is restored, contraction ends, muscle fibres relax
4 Physiological Factors That Influence Muscle Force
- sarcomere length
- influences amount of force
- 80-120% of resting length is optimal for force production
- most active tension produces more passive force - no. of single motor units
- more motor units –> more force
- motor unit type
- higher frequency –> more force - PSCA
- (muscle volume) / (fibre length)
- higher PSCA –> more force - Contraction Type
- concentric is weakest
- eccentric is strongest
Oxidative and Glycolytic Skeletal Fibres
oxidative: slow, resistant to fatigue
glycolytic: fast, fatigue rapidly
