Physiology Flashcards
define a motor unit
single alpha motor neurone and all the skeletal muscle fibres it innervates
which part of the nervous system are muscles controlled by?
somatic nervous system
what is secreted across the NMJ
ACh
how does an AP initiate a muscle contraction?
AP spreads down T-tubules which are close to lateral sacs of SR which contain Ca2+
Ca2+ binds to troponin on actin leading to movement of tropomyosin to uncover an actin binding site which myosin forms cross bridges with
how can muscle twitches be summated?
AP is shorter than the twitch
what happens if there is no opportunity for the muscle to relax?
tetanus is produced
two types of movement
isotonic (movement)
isometric (posture)
metabolic pathways for ATP used by muscles
creatine phosphate
oxidative phosphorylation
glycolysis
three types of muscle fibre
- slow oxidative type 1 (aerobic)
- fast oxidative type IIa (moderate)
- fast glycolytic type IIb (anaerobic)
what do slow oxidative fibres have a lot of?
mitochondria and myoglobin so are resistant to fatigue
define a reflex
stereotyped response to a specific stimulus
describe the monosynaptic spinal reflex
- muscle spindle (sensory receptor) activated by stretch causes firing in afferent neurones
- gamma motor neurones adjust tension in muscle spindle
- synapse at spinal cord with alpha-motor neurones
3 types of joints
- fibrous (synarthrosis)
- cartilaginous (amphiarthrosis)
- synovial (diarthrosis)
describe fibrous joint
bones are united by fibrous tissue causing no movement
example of fibrous joint
in the skull
describe cartilaginous joint
bones united by cartilage causing limited movement
example of cartilaginous joint
primary= physis secondary= vertebrae
describe a synovial joint
bones are separated by cavity containing synovial fluid and united by fibrous capsule with synovial membrane
what are bones covered with in synovial joints
hyaline
role of synovial fluid
lubricates joint
supplies chondrocytes with nutrients while removing waste
what makes synovial fluid
synovial membrane which contains vasculature, lymphatics and fibroblasts
role of articular cartilage
low friction
distributes pressure to subchondral bone
what is articular cartilage ECM made up of?
water
collagen (type II)
proteoglycans (GAGs)
is cartilage avascular?
yes
markers of cartilage degradation
serum keratin sulphate
type II collagen
