1
Q
Muscle Types
A
skeletal, smooth, caridac
2
Q
Smooth Muscle
A
- 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
3
Q
Cardiac Muscle
A
- 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
4
Q
Skeletal Muscle
A
- 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
5
Q
Function and Structure of Skeletal Muscle
A
- 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
6
Q
Sarcomeres
A
- 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
7
Q
Cross Bridge
A
linked myosin head and actin filaments
8
Q
Power Stroke
A
attachment and pull producing force
9
Q
Connective Tissue
A
Endomysium: surrounds each muscle fibre
Epimysium: fibrous tissue that surrounds skeletal muscle
Perimysium: groups muscle fibres into a fasicle
10
Q
The Motor Unit
A
- 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
11
Q
Muscle shapes
A
- 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
12
Q
Cross-Sectional Area
A
- greatest predictor of force is physiological cross sectional area
PSCA = (muscle volume) / (fibre length)
13
Q
Sarcomere Length and Myofibrils
A
- 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
14
Q
Muscle Tendon Unit
A
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
15
Q
Length Tension Relationship
A
- Sarcomere length influences force that can be developed
- optimal sarcomere length is 80-120% of resting sarcomere length
16
Q
Discharge Rate
A
- 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
17
Q
Axial Skeleton
A
- related to head and trunk of body
- 80 bones
- skull, rib cage,vertebral column
18
Q
Appendicular
A
- relates to limbs
- 126 bones
- shoulder girdle, arm, upper limb, hands
- pelvic girdle
- lower limb, foot
19
Q
Sagital / Parasagital
A
- divides body into left and right
- parallel w/ sagital (left and right but not equal)
20
Q
Coronal
A
divided body into posterior and anterior
21
Q
Sagital Plane
A
Transverse: divides into cranial and caudal (superior and inferior)
Flexion: decrease joint angle
Extension: increase joint angle
22
Q
Dorsiflexion
A
raise foot
23
Q
Plantarflexion
A
lower foot
24
Q
Abduction / Adduction
A
away from body / towards body
25
Supination / Pronation
palm up / palm down
26
Lateral / Medial
external rotation / internal rotation
27
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
28
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
29
Antagonist Muscle Pairs
- muscles apply opposing force to perform joint movement (bicep and tricep)
30
Agonist Muscle Pairs
help perform same joint movement (quad)
31
Long Bone
- shaft with ends
- important for leverage and movement
- femur, phalanges etc
32
Short Bone
- square shaped
- important for fine movements
- carpals, tarpals, patella, etc
33
Flat Bone
- important for protection
- hematopoiesis (make blood)
- sternum, scapula, ribs etc
34
Irregular Bone
- important for protection, support, movement and hematopoiesis
- vertebrae, pelvis etc
35
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
```
36
Osteogenic Cells
- bone cells
- stem cells
- develop into osteoblast then osteocyte
37
Osteoclasts
- bone cells
- very large with many nuclei
- improves reabsorption efficiency
- respond to mechanical stress
- "dig tunnels" to be lined with collagen by osteoblasts
38
Osteocytes
- maintain bone matrix
- hold bone together
- mineralise bone matrix
- long cytoplasmic extensions
- nutrients to bone matrix
39
Osteoblasts
- line tunnel with collagen
- create bone matrix (build bone)
- located on bone surface
- differentiate into osteocytes when trapped in bone
40
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
41
Primary / Secondary Ossification Centres
primary: form ~ 8 weeks after bone formation
secondary: present after birth until growth stops. involves developing ends of bone
42
Stages of Bone Development
1. resting cartilage
2. cartilage proliferation (hyperplasia - cells multiplying)
3. cartilage maturation (hypertrophy)
4. cartilage calcification (extracellular matric becomes calcified
5. ossification (osteoblasts form bone)
draw diagram
43
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
44
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
45
4 Physiological Factors That Influence Muscle Force
1. sarcomere length
- influences amount of force
- 80-120% of resting length is optimal for force production
- most active tension produces more passive force
2. no. of single motor units
- more motor units --> more force
- motor unit type
- higher frequency --> more force
3. PSCA
- (muscle volume) / (fibre length)
- higher PSCA --> more force
4. Contraction Type
- concentric is weakest
- eccentric is strongest
46
Oxidative and Glycolytic Skeletal Fibres
oxidative: slow, resistant to fatigue
glycolytic: fast, fatigue rapidly
