physiology Flashcards
functions of skeletal muscle
maintain posture, proposeful movement, resp movement, heat production, contribution to metabolism
describe skeletal muscle
straited and voluntary (innervated by somatic nervous system), no gp junctions, neurogenic initiation
where does the calcium from skeletal muscle come from
SR
what is the neurotransmitter in skeletal muscle
acetyl choline
what is straited and involuntary
cardiac muscle
what is unstraited and involunatry
smooth muscle
what is a motor unit
a single alpha motor neuron and all the skeltal muscle fibres in it innervates
what muscles have fewer motor fibres per motor unit
muscles for fine movements
how many fibres do muscles in the fingers and eyes have per motor unit
about 10
how many fibres do muscles for powerful movements have (the thigh)
100-1000 per motor unit
what does myocin look like
thick and dark
what does actin look like
thin and light
what does skeletal muscle consist of
parallel muscle fibres bundled by connective tissue - fibres usually extend the entire length of the muscle
what is myocin +actin
sacromere
what are sacromeres
functional units of muscle
what happens in sacromeres
actin slides over myocin which is ATP dependent
where is sacromere found
between two Z lines
what are the 4 zones of sacromeres
Abane, H zone, M line and I band
what happens in skeletal muscle fibres
Ca2+ is released from the lateral sacs of the SR when the surface action potential spreads down the transverse tubules
when is ATP needed
during muscle contraction (to power cross bridges) and during relaxation (to release cross bridges + to pump Ca2+ back into SR
what is a sign of death
rigor mortis
what is rigor mortis
when Ca2+ is pumped back into the SR
what does skeletal muscle tension depend on
the number of muscle fibres contracting and the tension developed by each contracting muscle fibre
in skeletal muscle what is shorterthe action potential or the resulting twitch
the action potential
how can a stronger contraction be achieved in skeletal muscle
by summating twitches through repitive fast stimulation of skeletal muslce
what is tetanus
muscle fibre stimulated so rapidly it has no opportunity to relax
example of tetanus
lock jaw
why cant cardiac muscle be tetanus
due to long refractory period
what does increased frequency of stimulation of skeletal muscle do
lead to stronger contraction
how can maximum contraction be achieved
when the muscle is at its optimum length before the onset of contraction
what is isotonic contraction used for
used for body movements and moving objects
what happens in isotonic contraction
tension remains constant as the muscle strength changes
what happens in isometric contraction
used for supporting objects in fixed positions and maintain body posture
when does muscle tension develop in isometric contraction
at constant muscle length
Type 1 muscle contraction
slow oxidative
what is slow oxidative
slow contraction, high resistance to fatigue, low aerobic eg walking
straited muscles
skeletal and cardiac
cardiac muscle initiation of contraction is
myogenic
skeletal muscle initiation of contraction is
neurogenic
is the continuity of cytoplasm between nerve and skeletal muscle cells
no
what is a motor unit
a single alpha moor neurone and all the skeletal muscle fibres it innervates
levels of organisation of muscles
muscle, neuron, fibre, myofibril, sarcomere
what do Z lines do
connect the thin filaments of two adjoining sarcomeres
what is a t TUBULE
extensions of the membrane than dip into muscle fibre
what do motor units allow
simultaneous contraction of a number of muscle fibres
what helps to prevent muscle fatigue
asynchronous motor unit recruitment during sub maximal contractions
can cardiac muscle be tetanised
no
what is type IIa fibre
fast oxidative
what is type Iix fibre
last glycolytic
what are type 2 fires used for
aerobic and anaerobic metabolism and are useful in prolonged relatively moderate work activities
what is fast glycolytic fibres used for
anaerobic metabolism and are mainly used for short-term high intensity activities e.g. jumping
what is a reflex
a stereotypes response to a specific stimulus - they are the form of coordinated movement
what is a stretch reflex
a negative feedback that resists passive change in muscle length to maintain optimal resting length of muscle
what is a muscle spindle
sensory receptor in muscle stretch
what causes impaired skeletal muscle function
intrinsic disease of muscle, disease of NMJ, disease of lower motor neurons which supply the muscle, disruption of input into motor nerves
genetic causes of muscle disease
congenital myophathies, chronic degeneration, abnormalities in membrane ion channels
acquired causes in intrinsic msucle disease
inflammatory myopathies, non inflammatory, endocrine, toxic
symptoms of muscle disease
muscle weakness/tiredness, delayed relaxation after voluntary contraction, muscle pain, muscle stiffness
investigations of nueromuscular disease
emg, nerve conduction studies, muscle enzymes, inflammatory markers, muscle biopsy
what is a synovial joint seperated by
a cavity containing synovial fluid
what is a synovial joint united by
a fibrous capsule
what is the inner capsule of a synovial joint lined by
synovial membrane
what is the articular surafces of the bones invilved in a synovial joint covered by
carterlage
how much synovial fluid is in an adult knee
<3.5 ml
what does the synovial fluid do
lubricates, facilitates ovements, minimises wear and tear, aids in nutrition of articular cartilage, supplies chondrocytes with O2 and nutrients
rapid movement means what for viscosity and elasticity
decreased viscosity and increased elasticity
what colour is synovial fluid
clear
what is articular cartiage usually
hyaline
descrbe hyaline cartilage
elastic sponge liek
what does articular cartilage have
special extracellualr matrix
what is the extracellular matrix of articular joints made of
water, collagen, proteroglycans
what is the extra cellular matrix madeand degraded by
chondrocytes
markers of cartilage degradation
serum and synovial keratin sulphate
what type of arthtritis is this - wear and tear, carrtilage and synovial composition and synocial composition and function deteriorate with age
osteoarthritis
what type of arthritis is this synovial cell proliferation and inflammation
rheumatoid
what type of arthritis is this- deposition of salt crystals
gouty arthtritis
what is the diagnosis of this - injury and inflammation to periaticular structures
soft tissue rheumatism
3 types of joints
synovial, fibrous, cartilaginous
what is synovial fluid made from
it is derived from hyaluronic acid
what type of collagen decreases with age
type 2
what is transduction of pain
translation of noxious stimulus into electrical activity at the peripheral receptor
what is transmission of pain
the propagation of pain signal as nerve impulses through the nervous system
what is the modulation of pain
modification/hindering of pain transmission in the nervous system
what is the perception of pain
conscious experience if pain
what are nociceptors
primary sensory afferent neurones normally activated by intense noxious stimuli
what type of neurones are nociceptors
first order neurones
where do second order neurones ascend from
the spinal cod in the anterolateral system
where do second order neurones terminate
in the thalamus
what are the major nociceptors
sensory afferent neurons atvated by intense noxious stimuli
myelination of a fibres
thin
myelinaton of c fibres
unmyelintated
where do alpha neurons recieve input from
upper motor neurons of the brain, sensory inputs from muscle spindles spinal interneurones
what are alpha nuerones directly responsible for
generation of force by muscle
what makes a motor unit
alpha motor neurone + muscle
where does the alpha motor unit communicate with muscle fibre
at the NMJ
what is the mechanism by which cells communicate electrically with one another across the synaptic celft
synaptic transmission
two forms of synaptic transmission
electrical or chemical
what does a gap junction consist of
two hemichannels
what do gap junctions permit the passage or
small molecules (<1KdA)
how does orthodromic synaptic transmission proceed
with limited delay
