Joint and muscle physiology Flashcards
What are the three main types of joint?
Synovial (diarthroses- e.g. knee)
Fibrous (synarthroses e.g. skull sutures)
Cartilaginous (amphiarthroses e.g. pubic symphisis)
What type of cells produce synovial fluid?
Fibroblasts
What are the functions of synovial fluid?
Lubricate, reduce friction and wear/tear
Replenish chondrocytes
The viscosity of synovial fluid is a function of which of its constituents?
Hyaluronic acid
How would inflamed synovial fluid appear?
Straw coloured/completely opaque, white cell count 2000-7500, >50 polymorphs per mm3
What are the main functions of articular cartilage?
Load distribution to subchondral bone
Provide low friction articular surface
What are the three components of articular cartilage?
Water (lubrication, nutrition, resiliency), Type 2 collagen (stiffness and strength), proteoglycan (compressive properties associated with load bearing)
What type of cells synthesise articular cartilage?
Chondrocytes
What are the three main types of muscle?
Smooth
Cardiac
Skeletal
Define “motor unit”
A single motor neurone and all the muscle fibres (cells) it innervates
What is the functional unit of skeletal muscle?
Sarcomere
Describe the hierarchical structure of skeletal muscle.
Muscle —> (many) muscle fibres —> (many) myofibrils (actin and myosin filaments) —> sarcomere
What neurotransmitter is involved in excitation/contraction coupling?
Acetylcholine
Action potential travels across …. and down the …. of muscle fibre, inducing …. release from the ….. of the…..
Surface membrane T-tubules Calcium release Lateral sacs Sarcoplasmic reticulum
How does calcium enable cross bridge formation?
Binds to troponin on actin filaments, displacing tropomysin and uncovering cross-bridge formation sites
What is ATP required for in excitation-contraction coupling?
To power cross-bridge formation; to release cross bridges (during relaxation) and actively pump calcium back into the sarcoplasmic reticulum
What does the gradation of skeletal muscle tension depend on?
Number of contracting muscle fibres
Tension developed by each contracting muscle fibre
What are the two types of skeletal muscle contraction?
Isotonic- tension remains the same as muscle gets shorter (moving objects etc)
Isometric- muscle length stays the same as tension develops (posture)
What is a reflex action?
Stereotyped response to a specific stimulus
How are passive changes in muscle length resisted?
Stretch reflex
What are the sensory nerve endings for the stretch reflex?
Annulospiral fibres
Describe the patellar stretch reflex.
Increased firing in afferent fibres due to stretch; synapse in spinal cord (L3/L4), firing in alpha motor neurones, contraction of muscle and relaxation of antagonist muscle
What are the main differences between subtypes of skeletal muscle fibres?
Pathways used for ATP synthesis
Resistance to fatigue
Activity of the myosin ATPase which determines speed of contraction
Describe how a) Type 1 b) Type 2a c) Type 2x skeletal muscle fibres are adapted for their purpose
a) slow twitch fibres- prolonged low-work aerobic exercise- many mitochondria, few enzymes for anaerobic glycolysis
b) intermediate- mixed
c) fast twitch- fast glycolytic- few mitochrondria. Explosive movements
