physiology Flashcards
what are the physiological functions of skeletal muscles? (5)
- maintenance of posture
- purposeful movement in relation to external environment
- respiratory movements
- heat production
- contribution to whole body metabolism
what is the largest type of tissue in the human body?
muscle
what are the 3 types of muscle tissue?
- skeletal muscles
- cardiac muscles
- smooth muscles
what muscle type is striated?
skeletal and cardiac
how does striation appear under a light microscope?
alternating dark bands and light bands
what causes the light/dark bands that can be seen in striated muscle?
light- actin thin filaments
dark- myosin thick filaments
what muscles are voluntary and what ones are involuntary ?
voluntary- skeletal muscle
involuntary- cardiac and smooth muscle
what nervous system controls skeletal muscle?
somatic nervous system
what nervous system control cardiac and smooth muscles?
autonomic nervous system
what type of muscle has a neurogenic initiation of contraction?
skeletal
what muscle has a myogenic initiation (initiated in muscle) of contraction?
cardiac muscle
what muscle has motor units?
skeletal muscle (the units are sarcomeres)
what muscle has neuromuscular junction present?
skeletal
what muscle has gap junctions present?
cardiac
how does calcium enter in cardiac muscle?
from ECF and sarcoplasmic reticulum
how does calcium enter in skeletal muscle?
entirely through the sarcoplasmic reticulum
what is the transmitted at the neuromuscular junctions in skeletal muscle?
acetylcholine
muscles which serve fine movements (external eye muscles, facial expressions, intrinsic hand muscles) have more or fewer fibres per motor unit?
fewer
what does the number of muscle fibres per motor unit depend on?
the function served by the muscle
how are skeletal muscles attached to the skeleton?
by tendons
how far do skeletal muscle fibres (cells) extend across the muscle?
they extend the entire length of the muscle
what are myofibrils?
specialised contractile intracellular structures
where are myofibrils found?
in skeletal muscle fibres (cells)
where are sarcomeres found?
in myofibrils
what is a functional unit of an organ?
the smallest componment capable of performing all functions of that organ
what is the functional unit for skeletal muscle?
a sacromere
what are the 4 zones a sacromere has?
A-band
H-zone
M-line
I-band
what is the A-band made up of?
thick filaments (myosin) along with portions of thin filaments (actin) that overlap both ends of thick filaments (myosin)
what is the H-Zone?
area within middle of A-band where thin filaments dont reach
what is the M-line?
it extends vertically down the middle of the A-band within the centre of the H-zone
what is the I- band?
it consists of remaining portion of thin filaments that do not project in A-band
how is muscle tension produced?
by sliding actin filaments on myocin filaments
what does force generation depend on?
it depends on ATP dependant interaction between thick (myosin) and thin (actin) filaments
when is Ca2+ needed?
-to switch on cross bridge formation ( actin myosin cross bridge) which allows actin to be pulled inward during contraction
- myosin is made up of 2 heads; one for ATP and one for binding to actin.
- actin is made up of lots of actin subunits, tropomyosin and troponin (a Ca2+ binding unit)
- the tropomyosin on the actin blocks the actin from binding to the myosin
- when Ca2+ binds to the troponin, the tropomyosin is moved allowing actin to bind to myosin and allowing cross bridge formation
what is ATP required for in skeletal muscle?
both contraction and relaxation
why is ATP needed during muscle contraction?
to power cross bridges
-it binds to myosin ATP binding site on one of its two heads
what is ATP needed for during relaxation?
to release cross bridges and to pump Ca2+ back into the sarcoplasmic reticulum
what does the gradation of skeletal muscle tension depend on?
- number of muscle fibres contracting within the muscle
- tension developed by each contracting muscle fibre
how long does the action potential last in skeletal muscle compared to the twitch?
action potential is much shorter than the duration of the muscle twitch
how is a stronger contraction of skeletal muscle achieved?
by adding together/summating twitches due to repetitive fast stimulation of skeletal muscle
what is isotonic contraction used for?
- body movements
- moving objects
what is isotonic contraction?
when the muscle tension remains constant as the muscle length changes
when is isometric contraction used?
to suport objects in fixed positions and for maintaining body posture
what is isometric contraction?
when muscle tension develops at constant muscle length
what is the main source of ATP when O2 is present?
oxidative phosphorylation
what is the main source of ATP when O2 is not present?
glycolysis
what is an immediate source of ATP?
the transfer of high energy phosphate from creatine phosphate to ADP
what are slow oxidative type I fibres used for? (slow twitch)
prolonged relatively low work aerobic activities e.g. walking
what are fast oxidative type IIa fibres used for? (intermediate twitch fibres)
-for both aerobic and anaerobic metabolism, relatively moderate activities e.g. jogging
what are fast glycolytic type IIx fibres used for? (fast twitch)
-use anaerobic metabolism and are used for high intensity activities e.g. jogging
what are the three types of joints?
synovial, fibrous and carilaginous
give an example of a fibrous joint
-coronal suture (bones of the skull in adults)
do fibrous joints allow much movement?
no
describe the structure of fibrous joints
bones united by fibrous tissue
describe the structure of cartilaginous joints
bones united by cartilage
do cartilaginous joints allow much movement?
they allow limited movement
give examples of cartilaginous joints
- intervertebral discs
- pubic sympsis
- part of the sacroiliac joints
- costochondral joints
do synovial joints allow much movement
yes a lot
give an example of synovial joint
hip
describe the structure of a synovial joint
bones seperated by a cavity (containing synovial fluid) and united by a fibrous capsule
what is the inner capsule of the fibrous capsule of the synovial joint lined with?
synovial membrane
what is the synovial membrane
vascular connective tissue with capillary networks and lymphatics that lines the fibrous capsule of a synovial joint
where are synovial cells (fibroblasts) found?
in the synovial membrane
what do synovial cells produce?
synovial fluid
what are the articular surfaces of bones covered with in a synovial joint?
cartilage
how can synovial joints be classed?
either simple or compound
what is a simple synovial joint?
a synovial joint that has on pair of articular surfaces (eg metacarpophalangeal joint)
what is a compound synovial joint?
a synovial joint with more than one pair of articular surfaces (eg elbow joint)
what are the physiological functions of joints?
to serve the functional requirements of the musculoskeletal system (structural support and purposeful motion)
what roles do joints play in purposeful motion?
- stress distribution
- confer stability
- joint lubrication
was is the function of synovial fluid?
- lubricates the joint, facilitating movement hence reducing friction, wear and tear
- aids the nutrition of articular cartilage
- supplies the chondrocytes (cartilage cellss) with O2 and nutrients and removes CO2 and waste
what is the joint cavity in a synovial joint filled with?
synovial fluid
is the synovial fluid static?
no because it is continuously replenished and absorbed by the synovial membrane
what makes the synovial fluid highly viscous?
the hyalorunic acid (mucin) produced by the synovial cells
what occurs to the viscosity and elasticity of the synovial fluid during rapid movement?
decrease in viscosity
increase in elasticity
what occurs to the properties of synovial fluid in OA?
the properties become defective due to diseased joint
what is the normal WBC of synovial fluid?
<200 WBC/mm3
what are the normal polymorph levels if synovial fluid?
<25m/mm3
what happens to the WBC count of the synovial fluid during inflammatory or septic arthritis?
is increases
when does the synovial fluid turn from normal clear and colourless to red?
in traumatic synovial tap and in haemorrhagic arthritis
what is the articular cartilage made up of?
water (70%) and collagen (20%) (mainly type II collagen which decreases wirth age) and proteoglycan (10%)
what is the extracellular matrix (ECM) synthesised, organised, degraded and maintained by?
chondrocytes
what occurs if the rate of ECM degradation exceeds the rate of its synthesis?
joint disease
what occurs to the synovial cell during rheumatoid arthritis?
synovial cell proliferation and inflammation causing rheumatoid arthritis
what does deposition of salt crystals in the joint do?
can cause gouty arthritis
what are the four distinct processed in the physiology of pain?
transduction, transmission, modulation and perception
what is the transduction process of pain?
-translation of noxious stimulus into electrical activtiy at the peripheral nociceptor
what is the transmission process of pain?
propagation of pain signal as nerve impulses through the nervous system
what is the modulation process of pain?
modification/hindering of pain transmission in the nervou system e.g. by inhibitory neurotrasmitters like endogenous opioids
what is the perception process of pain?
the conscious experience of pain, causes physiological and behavioural responses
pain begins with the activation of what receptors?
Nociceptors
whats an example of a first order neurone?
Nociceptor
what do first order neurones do?
relay information to second order neurones in the CNS by chemical synaptic transmission
where are the second order neurones found?
they ascend the spinal cord in the anterolateral system (terminate in the thalamus)
what is the spinothalamic tract (STT) involved in?
Pain perception (location, intensity)
what is the spinoreticular tract (SRT) involved in?
autonomic responses to pain, arousal, emotional responses, fear of pain
what do the third order neurones do in the nociceptive pathway?
relay sensory from the thalamus to the primary sensory cortex
what are the subtype of nociceptors?
A delta fibres and C fibres
what type of pain do A delta fibres detect?
it is myelinated so it mediates the ‘first’ or fast pain
what type of pain of pain do C-fibres mediate?
they are unmyelinated so mediate ‘second’, slow pain
what type of pain of pain do C-fibres mediate?
they are unmyelinated so mediate ‘second’, slow pain
what nociceptor is incharge of noxious mechanical and thermal stimuli?
A delta fibres
what nociceptors respond to all noxious stimuli?
C fibre
what nociceptor is responsible for lancinating, stabbing and pricking sensations?
A delta fibres
what fibres are responsible for burning, throbbing, cramping and aching sensations?
C fibres
what does nociceptive pain function as?
a warning physiological protective system to detect and avoid noxious stimuli
what causes neuropathic pain?
damage to neural tissue
what does neuropathic pain usually feel like?
can be perceived as burning, shooting, numbness, pins ands needles and may be less localized
what is dysfunctional pain?
pain where there is no identifiable damage or inflammation
give examples of dysfunctional pain
fibromyalgia, IBS, tension headache, temporomandibular joint disease, interstitial cystitis
what is highlighted blue?
epimysium
what is highlighted blue?
perimysium
what is highlighted blue?
fascicles
what is highlighted blue?
endomysium
what is highlighted blue?
sarcolemma
what is highlighted blue?
myofibril
