Module 3: Skeletal and Muscular Systems Flashcards
Describe all the components of the Skeletal muscle:
- larger than others
- makes up 40-50% of body mass
- striated (striped): arrangement of contractile components called sarcomeres, sarcomeres shorten when contracting (generally)
- muscle attached to bone via connective tissue called tendons and produce movement around a joint
- muscle cells/muscle fibres are long: during development, muscle fibres form by fusing multiple muscle cells (multi-nucleated, efficiency in repairing muscle fibres)
- controlled by the somatic nervous system (consciously influenced): innervated by motor neuron (direct from spinal cord), motor axons project to muscle fibres
Describe all the components of Smooth muscle:
- non-striated
- found (gastrointestinal tract, blood vessels, lymph, eye)
Describe all the components of Cardiac muscle:
- within contractile walls of the heart
- some striation
- ‘branches’, not necessarily parallel
- interconnect at intercalated disks allowing electrical signals to pass from one cell to another (helps synchronise heart muscle contraction), nucleus, intercalated disk (uninucleate- one nucleus)
How many skeletal muscles are there on each side of the human body?
approx 320
Outline 2 functions and structure points of skeletal muscle
- interact through production of movement and force
- characterised for postural, fine motor and gross motor control
List 2 characteristics of muscle fibres
- fatiguability
- force generating capacity
List 2 characteristics of whole muscles
- insertion points
- origin points
Describe muscle-tendon origin:
- attachment site that doesn’t move when the muscle contracts
- origin is usually proximal (closer to body midline)
List and describe the 4 qualities of skeletal muscle
- Contractibility: ability to shorten and thicken, develop tension
- Excitability: ability to respond to appropriate stimuli (action potential)
- Extensibility: ability to be stretched without damage
- Elasticity: ability to store some energy, and recoil to the resting length
Describe the microstructure of the muscle
- made up of a large number of bundles (fascicles) of muscle fibres (cells) surrounded by connective tissue
- a single muscle fibre cell is very long, runs parallel to other fibres: made from a large number of fused embryonic cells
- inside each cell is a bundle of myofibrils (muscle-slender fibre) that lie in parallel: a series of sarcomeres make up each myofibril, the sarcomere is the basic contractile unit of muscle, sarcomeres from adjacent myofibrils line up, giving muscle-striated appearance
- titin anchors myosin to the Z-line and can pull it back
- M-line contains myosin only: heads of myosin with actin binding site
Draw a diagram of a sarcomere
see booklet for full diagram
Describe the 8 steps in which the muscle fibre is stimulated
- Action potential reaches cavities in the sarcoplasmic reticulum
- Voltage-gated calcium channels open
- Calcium binds to troponin and causes tropomyosin to reveal myosin binding sites
- Myosin heads bind to the binding site
- Myosin causes actin to contract using the mechanical energy stored in the myosin head
- ADP and Pi detach from the myosin head
- ATP binds to the myosin head, causing it to detach from the binding site
- ATP is hydrolysed into ADP and Pi. The resulting energy is stored in the myosin head
Describe connective tissue and list the 4 types of connective tissue
- tissues are a group of similar cells and extracellular products organised to perform a common function
1. Epithelial tissue
2. Muscle tissue
3. Nervous tissue
4. Connective tissue
Describe 2 components of Muscle tissue
- a muscle is a muscle organ, comprised of muscle tissue and connective tissue
- little to no extracellular matrix
Describe 3 components of Connective tissue
- large amount of ECM: protein, salts, water, dissolved macromolecules
- located outside cells
- responds to physical stresses
List/describe the 5 things connective tissue consists of:
- Muscle fibres
- Fascicle
- Endomysium: array of tubes into which muscle fibres insert
- Perimysium: thickened area surrounding groups of the muscle fibres
- Epimysium: fine structure of connective tissue
Describe the connection between the nervous system and skeletal muscle (6 points)
- a single motor unit is the smallest functional unit in the musculoskeletal system
- 1 motor unit = 1 motor neuron, motor axon and all of the muscle fibres it innervates
- receives excitatory and inhibitory input from descending pathways, spinal interneurons and afferent fibres
- when sufficient excitatory input to reach firing threshold, an action potential is generated
- force altered by number and discharge rate of motor units and contractile properties of the muscle fibres
- distribution of muscle fibres from the same motor unit within a muscle are dispersed (crossover between motor unit muscle fibres, force distributed)
List the 3 fibre types of skeletal muscle
- Postural (type 1)
- Intermediate
- Ballistic (type 2)
Describe the qualities of Postural skeletal muscle fibre
- constantly working: ‘Cinderella’ fibres
- slow twitch, low force, fatigue resistant
- produces about 1.5 grams of force, for 150 milliseconds
Describe the qualities of Ballistic skeletal muscle fibre
- fatigue faster
- fast twitch, more force
- produces about 45 grams of force, for 100 milliseconds
Describe some properties of control of simple movements
- CNS receives excitatory and inhibitory input from descending pathways, spinal interneurons and afferent fibres (receptors in muscles and tendons)
List the 3 steps of signalling by neurons
- there are many dendrites on the aplha motor neuron
- if this is significant, an action potential will be generated
- generates myoelectric action potential (within muscle cell)
Describe the functions of the human skeleton and list the 6 components of the human skeleton
- framework of any structure, does not always comprise of bones
1. Exoskeleton: hard covering on outside of body
2. Hydrostatic skeleton: fluid held under pressure
3. Endoskeleton: within soft tissues - mechanical functions: support, protect and move
- metabolic functions: nutrient store (minerals and lipids), blood cell formation
4. Support: for muscles that contract to maintain posture, body shape and bodily functions - without the ribs the lungs would collapse
- the pelvis is the floor for the pelvic organs
5. Protect: body organs from potential harm - the skull protects the brain
- the vertebral column protects the spinal cord
- the rib cage, spine and sternum protect the lungs, heart and major blood vessels
6. Move: converting muscle contraction into movement of ourselves or something in the environment requires a rigid structure
List 3 examples of metabolic functions of the human skeleton:
- nutrient store
- blood cell formation
- stores 99% of the body’s calcium and 85% of the body’s phosphate
What are the 2 categories in which the skeleton can be divided into?
- Axial
2. Appendicular
List and describe the 4 main types of Axial bones
Axial- relating to or situated in the head and trunk region of the body: contains 80 bones
Skull (22):
- protects the brain
- supports soft tissues of the head
- mandible is separate and allows movement during chewing
Ossicles (middle ear):
- transmit sounds through movement/vibration
- hyoid bone: aids tongue in movement and swallowing
Rib cage (including sternum):
- protects heart and lungs
- supports shoulder girdle and allows movement such as respiration
Vertebral column:
- protection of the spinal cord
- support for rib cage and movement
List and describe the 3 main types of Appendicular bones
Appendicular- relating to limbs: contains 126 bones
Shoulder girdle:
- supports arm, forearm and hand movement
Pelvic girdle:
- support of abdominal contents and upper body
- support attachment of lower limb
- movement in locomotion
Thigh, leg and foot:
- movement
- supports entire weight of body
List/describe the 4 different anatomical planes
Anatomical planes: terminology for joint movements in the musculoskeletal system
- Sagittal (or median): divides the body into left and right
- Parasagittal: parallel with sagittal
- Coronal (or frontal): divides the body into dorsal and ventral (back and front; posterior and anterior)
- Transverse (or horizontal): divides the body into cranial and caudal (head and tail; superior and inferior)
List the 5 types of anatomical movements
- Abduction (out)/Adduction (in)
- Dorsiflexion (foot at right angle)/ Plantarflexion (foot straight down)
- Pronation (palm down)/ Supination (palm up)
- Extension (wrist/hand at right angle)/ Flexion (wrist/hand straight down)
- Lateral (palm and arm facing front/out)/ Medial (palm and arm facing inwards to body)
Describe Fibrous joints (3 points)
- contain fibrous connective tissue
- some cannot move at all, e.g. skull structures
- some allow little movements: depending on length of connective tissue, e.g. ligaments between tibia and fibula in the ankle
Describe Cartilaginous joints (3 points)
- contain cartilage
- cushion force
- allow more movement than fibrous joint
Describe Synovial joints (3 points)
- fluid filled cavity
- greatest range of movement
- 3 different types (hinge, ball and socket, pivot)
Describe Antagonistic muscles (2 points)
- oppose joint muscle
- work together
Describe Synergist muscle (1 point)
- help same joint motion
List the 4 different types of Bone
- Long
- Short
- Flat
- Irregular
Describe 2 components of Long bone
- shaft with ends: femur, phalanges
- leverage and movement
Describe 2 components of Short bone
- square-shaped: carpals, patella
- fine movement
Describe 3 components of Flat bone
- sternum
- protection
- haematopoiesis
Describe 2 components of Irregular bone
- pelvis
- protection, support, movement, haematopoiesis
Describe 3 components of Bone structure
- stiff and strong, resistant to compression and tension
- collagen: 40% tough and flexible
- calcium and salt: 60% hard and rigid between collagen fibres
List the 4 different types of Bone cells
- Osteoclasts
- Osteoblasts
- Osteocytes
- Osteogenic
Describe 2 components of Osteoclasts
- large cell with many nuclei
- breaks down bone matrix and responds to mechanical stress
Describe 3 components of Osteoblasts
- forms bone matrix in tunnels made by osteoclasts
- surface
- differentiate into osteocytes trapped in bone
Describe 3 components of Osteocytes
- maintains bone matrix, holds it together
- mineralises bone matrix
- can supply nutrients
Describe 1 component of Osteogenic
- stem cells develop into osteoblasts and then osteocytes
List/describe 3 types of material in composition of bone
- trabecular bone (spongy) for bone marrow development
- lamellar (compact) supports and stores calcium
- bones respond to stress
Outline key changes of musculoskeletal structures over lifespan
- bone acquisition during childhood affects later likelihood of osteoporosis
- decay:
- osteopenia: more reabsorption than deposition
- osteoporosis: low bone density, less able to absorb mechanical energy
List 3 components of muscle architecture
- Fibre length
- Muscle volume
- Physiological cross-sectional area
Describe 5 components of Physiological cross-sectional area
- longitudinal/parallel: fibre length = muscle length
- pennate (at an angle): fibre length> muscle length
- multi-pennate (multiple angles): fibre length»_space; muscle length
- muscles are a combination of these types
- different muscles have different force generating capacity
Describe force generating capacity in terms of PCSA
- the greatest predictor of force is the muscle’s physiological cross-sectional area
PCSA= muscle volume/fibre length - cross-sectional MRI scans of thigh, determine volume
- ultrasound reconstruction for fibre length
- ultrasound reconstruction for pinnation angle
Describe pennation angle
- actual muscle force (force applied to tendon)
- PCSA x cos(angle) where angle is the pennation angle
Describe sarcomere length (3 different components)
- Hill’s mechanical model of the muscle-tendon unit
1. Contractile component
2. Series Elastic component
3. Parallel Elastic component
Outline 5 components of the Contractile component
- muscle fibres, actin and myosin cross bridges
- relaxed: some overlap
- contracting: greater overlap
- fully contracted: full overlap, myosin may overlap (less force)
- 80 -120% of resting length is optimal sarcomere operating length
Outline 1 component of Series Elastic component
- intracellular titin, tendon
Outline 1 component of Parallel Elastic component
- connective tissue, epimysium and perimysium, endomysium
Describe a single motor unit
- one motor unit is the smallest functional unit in the musculoskeletal system
- 1 motor neuron, its motor axon and all of the muscle fibres it innervates
- evert action potential in the muscle fibres generates a little bit of force
Outline the importance of ‘number’ of single motor unit
- the more motor units, the more force
- more excitatory input recruits more motor units
Outline the importance of ‘discharge rate’ of single motor unit
- every action potential produces a little bit of force: ‘single twitch’
- summation of forces before twitch has expired
- series of action potentials at high frequency results in tetanus (highest amount of force able to be produced)
Outline the importance of ‘ fibre type’ of single motor unit
- slow twitch/fast twitch
- Henneman’s size principle: the recruitment of motor units based upon fibre type
1. Slow oxidative: slow contraction speed, aerobic respiration, slow fatigue, many mitochondria, high myoglobin content (red)
2. Fast Oxidative: fast contraction speed, aerobic respiration, intermediate fatigue, many mitochondria, high myoglobin content (red)
3. Fast glycolytic: fast contraction speed, glycolysis ATP source, fast fatigue, few mitochondria, low myoglobin content (white)
List/describe the types of contraction
Isometric: - static/same length Dynamic: - concentric (shortening) - eccentric (lengthening) Maximum force that can be produced is dependent on the direction: eccentric > isometric> concentric
Outline 4 points to do with the action potential and neuromuscular function
- the connection between the nervous system and the muscle is the neuromuscular junction
- AKA: motor point, motor end plate, synaptic cleft, synaptic terminal
- every AP generated in the motor neuron generates an action potential in the motor units’ muscle fibres
- myo-electric action potentials as they run along muscle fibres can be recorded by electromyography (EMG)
Outline 5 points to do with myoelectric action potential and EMG
- muscle action potential
- myoelectric action potentials are initiated by ACh released by the motor neuron
- ACh binds to proteins on muscle cell membrane, triggering a myoelectric action potential
- the action potential sweeps along the muscle fibre and into the transverse tubules
- surface EMG records myoelectric AP running along muscle fibres under electrodes
