muscles Flashcards
name the 3 different types of muscles tissue and their difference structures
3 types of muscle tissue
– Skeletal (attached to bones) = 40% body wt.
– Cardiac (heart & great vessels).
– Smooth (hollow vessels & organs)
what is the difference between striated and non-striated muscles
S: highly ordered arrangement of contractile proteins
NS: less ordered…
which muscle types are straited and which are non striated
NS: smooth
S: skeletal and cardiac
why do the muscles have different microscopic appearance
different functions
which muscle can relax and recover quickest and slowest: provide a order
skeletal> cardiac >smooth
describe what happens during a flexion
triceps muscle relaxes
biceps muscle contracts (flexors)
describe what happens during an extension
triceps muscle contracts (extensor) biceps muscle relaxes
what is an antagonistic pair and what is a good example of it
each reverses the action of the other
e.g. flexion and extension
what is the muscle equivalent of a muscle cell
muscle fiber
what is the muscle equivalent of a cell membrane
sarcolemma
what is the muscle equivalent of a cytoplasm
sarcoplasm
what is the muscle equivalent of a modified E.R
sarcoplasmic reticulum
describe the ultrastructure: where is the sarcomere
Z line to Z line
how are sarcomeres arranged
Highly ordered filament arrangement - ensures efficient interaction
name the 2 filament tpes
thick, myosin
thin actin
describe arrangement of thin filaments
2 polymer helices, F and G actin
what is the metaphorical description of thin and thick filaments
double string of pearls-A, thin
golf clubs in a bag’ -M, thick
(thin) what is the F actin function
no diretionality
(thin) what is the G actin function
myosin binding site
(thin) what is the function of tropomyosin
guards binding site
(thin) function of nebulin
separate 2 thin helices, align actin
describe the sarcomeres within the smooth muscles
No ‘sarcomeres’, but caveolae
(sarcomere) what is the function of titin
elasticity and stabilizes myosin
what does calcium do within the power stroke
binds to TN and shifts exposing binding site of G actin, allows for power stroke
fibre types Fast, fatigable
glycolytic (sparse mitoch/myoglobin)
fibre types - Slow, fatigue-resistant
oxidative (high mitoch/myoglobin)
Exercise & Fatigue
name 2 types of contractions
neurogenic and myogenic
difference in the 2 types of contractions: neurogenic and myogenic
N: skeletal muscle contracts when M.N activated
M: Cf cardiac muscle & most smooth muscle, contracts spontaneously
Latent period- what is it
schematic of the series elastic component
what are the 5 components force generation depends on
- Initial length of muscle
- Degree of activation (no. active muscle fibres)
- Rate of contraction (fibre type, fast/slow)
- Frequency of stimulation
- Cross-sectional area of muscle
Frequency of stimulation: describe single twitch freq
well spaced
does tension always induce movement and explain the mechanisms behind this
no due to isotonic contraction, muscle contracts, shortens and creates enough force to move load
on a force velocity relationship graph where is the isotonic and isometric contractions
isotonic contraction in the middle and isometric o at 0 velocity of shortening
what is the difference between isometric and isotonic contraction
No external load -> max rate of shortening -> isotonic.
* Max load -> no shortening -> isometric
what does a greater load mean for contraction speed
– Greater load -> slower shortening.
true or false: isotonic means no movement and no power/work
false it is isometric,
what is the most efficient fraction and percentage of rate of shortening
1/3 max rate of shortening.
* For humans, efficiency of most frequently used leg muscles
– = ~20-25% max rate of shortening
what does tension muscle fibre equation
no. myofibrils/ muscle fibre
what does resistance training do to the muscle fibre
increases number of myofibrils
increase x sectional area of individual muscle fibres
true or false resistance training increases in number of muscle fibres
false it increase cross sectional area no number of fibres
which types of muscles have quicker contraction rates
skeletal>cardiac>smooth
(smooth muscle) contractile organisations: how does the multi-unit contract and how (separately or together)
- predominant
– cells connected by gap junctions
3D clusters of smooth cells
– activity in one cell -> others -> single functional unit. - all contract together as single unit
(smooth muscle) contractile organisations: how does the multi-unit contract (separately or together)
Multi-unit
– cells not connected by gap junctions
- each stimulated separately as multi unit
(smooth muscle) contractile organisations: single unit examples
gut, uterus, bladder ANS, activity strongly influenced by circulating hormones (e.g. epinephrine)
(smooth muscle) contractile organisations: multi unit examples
intrinsic muscles of eye (iris/lens), skin piloerectors, lge blood vessels
(smooth muscle) contractile organisations: single unit contraction type
– spontaneous rhythmic contractions, originate in pacemaker areas. = MYOGENIC CONTRACTION
(smooth muscle) contractile organisations: multi unit contraction type
activated by nerve activity only -> similar to skeletal muscle
motor units. = NEUROGENIC CONTRACTION
Typical smooth muscles organisations
single unit & multi-unit organisation
smooth muscle vs cardiac muscle : what initiates contractile properties
S: actin/myosin - contractile proteins
C: cardiac AP - myogenic
smooth muscle contraction; what are dense bodies
where the diagonal filaments bundles of actin and myosin intersect
Excitation/contraction coupling: contraction of muscles
calcium enters from SR and ECF to phosphorylate calmodulin
from inactive to active myosin light chain kinase
MLCK + ATP = active myosin ATPase
ATPase + actin = increased muscle tension
relaxation of smooth muscles
calcium pumped out using ATP into ECF and SR through pump Na+/Ca2+ exchanger and Ca2+ pump
Ca2+ drops off calmodulin
active to inactive calmodulin
myosin phosphatase takes Pi off myosin head
myosin ATPase activity decrease –> inactive myosin
= decreased muscle tensions
what is the difference between myosin phosphatase and kinase
kinase activates proteins and phosphatase deactivates
true or false: calcium can diffuse through membrane from ECF and SR into the cell for smooth muscle contraction
no, Calcium is pumped out using ATP against conc. grad. for smooth muscle relaxation
caveolae function in smooth muscle
small invagination that concentrate Ca, so that it can readily flood in
(smooth muscle) difference between slow wave, pacemaker potentials and pharmacochemical coupling
SW: fire AP when threshold is reached
P: depolarise when threshold is reached
PC: when chemical signals change muscle tension without changing membrane potentials
(smooth muscle) provide examples of slow wave, pacemaker potentials and pharmacochemical coupling
SW + P : Ca channels open and contract
P: hormone/paracrine factors e.g. histamine or nitric oxide
(smooth muscle) what triggers the regulation of contractions process from ECF
signal ligands such as ANS transmitter circulating hormone
and depolarization or stretch
(smooth muscle) what does this regulation of contractions process from ECF trigger
membrane receptors, membrane channels, and store operated Ca2+ channels
(smooth muscle) what do membrane receptors trigger
modulatory pathways –> alter MLCK/myosin phosphatase
alter actin associated proteins
increase IP3 –> sarcoplasmic Ca2+ release
–> cell response
(smooth muscle) what do membrane channels trigger
increase Ca2+ entry –> cell response
(smooth muscle) what do store operated Ca2+ channels trigger
decreased intracellular Ca2+ stores
–> cell response
cardiac muscles: what are intercalated disks
allow cells to attach to each other and communicate with each other- disk between 2 adjacent cells
cardiac muscles: what do intercalated disks contain
gap junctions for electrical contractions
cardiac muscles: describe the structure of cardiac muscle
one nucleus, gap junctions and desmosomes many mitochondria for energy
cardiac muscles: what do desmosomes do
are strong attachments to support the powerful contractions
action potential skeletal muscle and what does repeated activity cause
skeletal : AP before tension generated
causes summation & tetanus
cardiac muscles: action potential duration
refractory period is very long (compare to skeletal, 15-5x longer)
this means that cannot get multiple stimuli in a healthy heart
cardiac muscle: where is the AP and why is tetanus not possible
AP during tension generated: Tetanus impossible due to long refractory period
what’s the different roles of skeletal and cardiac muscle during contraction
s: triggers contraction
c: dictates length of contraction
how to increase the freq of membrane potential in Sino atrial cell
sympathetic stimulation, noradrenaline activating only Sino atrial cells through β1 adrenoceptors
how to increase heart rate
increase the freq of membrane potential in Sino atrial cell
difference in membrane potential graph in SA cells when heart rate increases and decreases
increases: faster depolarisation and hyperpolarisation
decrease: slower depolarisation and hyperpolarisation
how to decrease heart rate
decrease the freq of membrane potential in Sino atrial cell
how to decrease the freq of membrane potential in Sino atrial cell
Parasympathetic stimulation/acetylcholine
- slows pacemaker cells
-through muscarinic ACh receptors
Sino atrial membrane potential: adrenoreceptor β1 function and muscarinic Ach receptor function
increase Ca2+ and I.f flow for sympathetic stimulation
decrease Ca2+ and I.f flow for sympathetic stimulation
what is a membrane potential made up of in a Sino atrial cell
membrane potential = pacemaker potential (1) and action potential (2)
Sino atrial membrane potential: what happens at the start and end of pace maker potential
start: not Na+ in, I.f channels open
end : Ca2+ in, channels open , threshold potential, I.f channels close
Sino atrial membrane potential: what happens at the rise, peak, point of hyperpolarisation of action potential
rise : Ca2+ in, I.f channels close
peak : Ca2+ channels close and K+ channels open
point of hyperpolarisation: K+ channels close
what is the chronotropic effect vs the inotropic effect on heart muscle
chronotropic effect : change of rate
inotropic effect : change of force through increase cotnractility
true or false: the positive ionotropic effect is due to sympathetic stimulation and occurs by change in length
explain answer
false, without any length change cause the receptors on surface change intrinsic ability of muscle cell to contract
what is the positive negative ionotropic effects
positive = increased contractibility
negative = decreased contractibility
Sino atrial membrane potential: describe the cascade of reactions to increase contraction force
adrenoreceptor β1 stimulation - increase cAMP - activates PKA - phosphorylation of V-G Ca2+ Channels - longer open time - increase Ca2+ influx/AP = increase contraction force
what is the sarcomere proportional to
blood volume returning to heart
skeletal vs cardiac: which has higher tension at a set sarcomere length (not 100%)
skeletal does over cardiac
describe 2 functional benefits to length tention relaationship
more venous return (e.g. exercise) -> stretch -> more
forceful contraction
more blood pressure in left vent -> more venous return -> more forceful contraction
what does venous return mean
flow of blood from the periphery back to the right atrium, hence cardiac output
what is Starling’s Law of the Heart
heart pumps out all blood received.
describe the internodal pathway: Electrical conduction system of the heart
SA node; AV node, A-V bundle, bundle branches, Purkinje fibres
