Physiology Flashcards
name the physiological functions of skeletal muscle
posture
movement/ respiratory movements
heat production
contributor to whole body metabolism
skeletal muscle is striated/non striated and voluntary/ non voluntary
striated and voluntary
which nerves innervate skeletal muscle?
somatic nervous system
skeletal muscle has _______ initaion of contraction
neurogenic
what is the transmitter at the neuromuscular junction of skeletal muscle
Ach
skeletal muscle fibres are organised into what?
motor units- single alpha motor neuron
muscles that allow for precise movements will have fewer/greater motor fibres per unit than for power?
fewer
sort into levels of organisation 1. muscle fibre 2. sarcomere 3. myofibril 4. actin/filamin 5. whole muscle
- actin/filamin 2. sarcomeres 3. myofibrils 1. muscle fibre 5. whole muscle
define functional unit
smallest component capable of performing all the functions of that organ
sarcomere is found between what two lines?
Z lines
what are the four zones of the sarcomere
A- band
H- zone
M- line
I- band
describe the A- band
thick filaments with portions of thin filamwetns that overlap in both ends of thick filaments
describe the H- zone
lighter area of the A-band where thin filaments dotn reach
describe the M-line
extends vertically down A-band within the centre of H-zone
describe I-band
remaining portion of thin filaments that don’t project in A-band
muscle contraction is caused by what?
actin filaments sliding on myosin filaments
force generation of muscle depends on what?
ATP- dependant interaction
in skeletal muscle fibres Ca2+ is released from where?
lateral sacs of the sarcoplasmic reticulum
the surface action potential of skeletal muscle spreads down what?
the transverse (T)- tubules (extensions of the surface membrane)
what allows simultaneous contraction of muscle fibres?
motor units
stimulating more motor units to achieve a stronger contraction is known as what?
motor unit recruitment
asynchronous motor unit recruitment during submaximal contractions helps prevent what?
muscle fatigue
tension developed by each contracting muscle fibre depends on what two things?
frequency of stimulation and summation of contractions
length of muscle fibre
the action potential in skeletal muscle is longer than the duration of the resulting twitch true/false
false- the AP is shorter
describe single twitch in skeletal muscle
the muscle fibre has completely relaxed before being restimulated
with single twitch the second twitch is the same/greater magnitude than the first twitch
same magnitude
what happens if a muscle fibre is restimulated before it has completely relaxed?
the second twitch is added to the first resulting in twitch summation
what is tetanus?
when a muscle fibre is stimulated so rapidly it doesn’t have time to relax between stimuli- maximal sustained contraction
what type of muscle cannot be tetanised and why?
cardiac muscle- long refractory period
when is maximal tetanic contraction achieved?
when the muscle is at its optimal length before the onset of contraction
the tension developed by skeletal muscle increases with what?
frequency of stimulation
what is the optimal length of skeletal muscle in the body?
the resting length
what are the two types of skeletal muscle contraction?
isotonic isometric
what movements is isotonic contraction useful for?
body movements moving objects
describe isotonic contraction
muscle tension remains constant as the muscle length changes
what movements is isometric contraction useful for?
supporting objects in fixed posn
maintaining body posture
describe isometric contraction
muscle tension develops at constant muscle length
how is muscle tension developed in both isotonic and isometric contractions?
transmitted to bone via elastic components of muscle
what are the contractile and elastic components of muscle?
contractile- sarcomeres
elastic- connective tissue/tendon
the velocity of muscle shortening increases/decreases as the load increases?
decreases
what are the main differences between types of skeletal muscle fibres?
ATP synthesis pathway
resistance to fatigue
activity of myosin ATPase
what are some of the metabolic pathways that supply ATP in muscle fibres?
transfer of high energy phosphate from creatine phosphate to ADP (immediate source)
oxidative phosphorylation (O2 present)
glycolysis (O2 isn’t present)
what are the three types of skeletal muscle fibres?
Type I- slow oxidative
Type IIa- fast oxidative
Type IIx- fast glycolytic
give some feature of type I- slow oxidative muscle fibres
slow twitch
many mitochondria
low myosin ATPase activity
low glycogen content
what activities are type I- slow oxidative fibres useful for?
prolonged low work aerobic activitities e.g posture, walking
give some features of type IIa fast oxidative muscle fibres
intermediate twitch fibres
many mitochondria
high myosin ATPase activity
intermediate glycogen content
what activities are type IIa fast oxidative fibres useful for?
aerobic and anaerobic metabolism, prolonged moderate work e.g jogging
give some features of type IIx fast glycolytic muscle fibres
fast twitch
few mitochondria
high myosin ATPase activity
high glycogen activity
what activities are type IIx fast glycolytic muscle useful for?
anaerobic metabolism used for short term high intensity activiites e.g jumping
what is the simplest form of coordinated movement
reflex action
define reflex
reflex action is a stereotyped response to a specific stimulus
the stretch reflex is the simplest form of what kind of reflex?
monosynaptic spinal reflex
what is the stretch reflex?
negative feedback that resists passive change in muscle length to maintain optimal resting length of muscle
what does the stretch reflex help with?
posture e.g while walking
what sensory receptor in muscle is activated by muscle stretch?
muscle spindle
stretching the muscle spindle increases firing in what? where do they synapse?
afferent neurons synapse in the spinal cord with the alpha motor neurons
what are muscle spindles a collection of and what are they known as?
collection of specialised muscle fibres known as intrafusal fibres
what are ordinary muscle fibres referred to as?
extrafusal fibres
where are muscle spindles found?
within the belly of muscles and run parallel to ordinary muscle fibres (extrafusal)
what are annulospiral fibres?
the sensory nerve endings of muscle spindles
do muscle spindles have their own efferent (motor) nerve supply?
yes- gamma motor neurons
What do the gamma motor neurons do to muscle spindles?
Adjust the level of tension in muscle spondles to maintain their sensitivity during muscle contraction
contraction of intrafusal fibres contributes to the overall strenght of muscle contraction true/false?
false- they do not contribute to the overall strength of contraction
give examples of some geneticalluy determined myopathies
congenital
chronic degeneration e.g Muscular dystrophy
abnormalities in membrane ion channels e.g myotonia
give an example of aqcuired inflammatory myopathies
polymyositis
give an example of a non-inflammaotory acquired myopathy
fibromyalgia
give an example of an endocrine acquired myopathy
cushing syndrome
thyroid disease
give an example of a toxic acquired myopathy
alcohol
statins
what are the symptoms of muscle disease
muscle weakness/tiredness
delayed relaxation after voluntary contraction (myotonia)
muscel pain (myalgia)
muscle stiffness
what are some useful investiagtions in neuromuscular disease?
Electromyography (EMG)- electrodes detect presence of muscular activity
nerve conduction studies
muscle enzymes (CK)
Inflammatory markers C reactive Protien (CRP), plasma viscosity (PC)
muscle biopsy
What are the three type of joint in the body?
Synovial
fibrous
cartilaginous
describe fibrous joints and give an example
bones united by fibrous tissue
dont allow any movement
bones of the skull in adults
descirbe cartilaginous joints and give examples
bones united by cartliage
limited movement
intervertebral discs, pubic symphsis, costochondral joints
desrcibe synovial joints
seperated by a cavity and united by fibrous capsule
which joint is described as being amphiarthosis?
cartilaginous joint
which joint is described as being synarthrosis?
fibrous joint
which joint is described as being diarthrosis?
synovial joint
where is synovial fluid found?
the synovial cavity
in addition to the fibrous capsule what other structures unite and support synovial joints?
ligaments
tendons
bursae
the synovial membrane lines what aspect of the fibrous capsule?
the inner aspect
is the synovial membrane vascularised?
yes- it is a vascular connective tissue with capilary networks and lymphatics
synovial cells (fibroblasts) within the synovial membrane produce what?
synovial fluid
what are the two classes of synovial joint?
simple- one pair of articular surfaces
compound- more than one pair of artivualr surfaces
give an example of a simple synovial joint
metacarpophalangeal joint
give an example of a compound synovial joint
elbow joint
with regards to stress distribution the greatest share of loading energy is taken up where?
the muscles and tendons crossing each joint
give some functions of synovial fluid
lubrication
reduces friction
aids in nutrition of articular cartliage
supplies chondrocytes with O2 and removes CO2
the synovial fluid is continously replenished adn absorbed by what?
synovial membrane
what is responsible for the high viscosity of synovial fluid?
hyaluronic acid (mucin)- prod by synovial cells
uric acid in the synovial fluid are dervied by what?
dialysis of blood plasma
the synovial fluid contains few cells normally, what are these mainly?
mononuclear leucocytes
rapid movement is associated with inc/dec viscosity and inc/dec elasticity?
decreased vscosity
increased elasticity
in what disease do the viscous/elastic properties of synovial fluid become defective?
osteoarthritis
what colour is normal synovial fluid?
clear and colourless
what is the WBC count in normal synvoial fluid?
<200 WBC/mm3 of which polymorphs are usually <25/mm3
when would synovial fluid turn red?
traumatic synovial tap
haemorrhagic arthirits
what kind of synvoial fluid would have a straw/yellow colour and give a total white cell count of 2,000-75,00
inflammatory synovial fluid
what kidn of synovial fluid would give a total white cell count of >100,000
septic synovial fluid
the thin and opaque appearance of synovial fluid from a severely infected joint is due to what?
the very high polymorph count
what ares some of the main functions of articular cartliage?
low friction- help prevent wear-and-tear
distributes pressure
what are the four zones of articualr cartilage?
superfical
middle
deep
calcified
articualr cartilage is usually which type?
hylaiine
the ECM of articualr cartilage is synthesized, degraded and maintained by what cells?
chondrocytes
articular cartliage is vascular/avasuclar?
avascular
from what does articular cartilage recieve nutrients and O2
via synovial fluid
describe the rate of ECM degradation with the rate it is replaced in an normal joint
degredation doesnt exceed the rat eof replacement- there is a balance
changes in the relative amounts of the components of the ECM (water, collagen, proteoglycans) would also change what?
the mechanical properties of the cartilage
what would occur if the rate of ECM degredation exceeds the rate of synthesis?
joint disease
what are the catabolic factors in the ECM?
TNF alpha
IL- 1
what do catabolic factors do in the ECM?
stimulate proteolytic enzymes and inhibit proteoglycan synthesis
what are the anabolic factors in the ECM?
tumour grwoth factor TGF
insulin like growth factor (IGF)-1
what do anabolic factors do in the ECM?
stimulate proteoglycan synthesis and counteract effects of IL-1
what are some markers of cartilage degredation?
Serum and synovial keratin sulphate
Type II collagen in synovial fluid
deterioration of cartilage with age gives rise to what condition?
osteoarthritis
synovial cell proliferation and inflammation casue what condition?
rheuamatiod arthritis
depsoition of salt crystals e.g uric acid can cause what conditio?
gouty arthritis
injury and inflammation to periarticular structures causes what condition?
soft tissue rheumatism e.g injury to tendon causes tendonitis
subchondral sclerosis and subchondral cyst formation will be present in what condtion?
osteoarthritis
