Bio Unit 3 part 2 Flashcards
how is the tenstion excerted by a muscle during a single twitch influenced by
1;. the muscle type
2. sarcomere length at the start of contraciotn
what is sarcomere lenghth
the degree of overlap between the thick and thin filaments
what happens with too little overlap in sorcomere lenghth, too much over lap and way too much overlap
too litle: few crossbridges, little force can be generated
too much:actin filaments start to interfere with each other, less force generated
way too much overalp; thick filaments collide with Z disk, force rapidly decreases
how can the force of a muscle five be increased
a single twitch does not prepresent the maximum force the muscle fibre can develop, it is increased by increasing the rate of action potentials that stimulate the fibre
Summation
increase in force generated by a muscle, increase tenstion level
due to repeated stimulation from action potentials that occur before the muscle has fully relaxed
tetanus, incomplete (unfused) tetanus, and complete (fused tetanus
from summation
term for the state of muscle when it reaches maximmum force of contraction
incomplete (unfused) tetanus, slow sstimulation rate, fibre relaxes slightly between stimuli
complete (fused) tetanus; fast stimulation rate, fibre does not have time to relax
what is the motor unit and the two components
the basic unit of contraction in an intact skeletal muscle, muscle made up of many fifferent motor units
- a group of muscle fibers
- the somatic motor nueron that controls them, by action potental and contracts all muscle fibers
motor uni contracts in an all or none fashion
how is the contracction of the muscle baried
- changing the type of motor unit that is activated
- changing the number of motor units that are active
which will have more muscle fiberes per motor unit fine or cource movements
cource
what are all the fibres in a motor unit
they are all one type
isotonic
creates force and mocves a load, the load is ussually constant, and the muscle length changes
isometric
creates force without movement, muscle lenghth is constant and the load is usually greater than the force that can be applied
whaere is smooth muscle found in the body?
walls of hollow organs and tubes, bot attached to bones of skeleton
how are smooth muscles arrangess,single unit and multi unit
single unit, cells coupled by gapp junctions, not cessary to electrically stimulate each individual fibre and are found on walls of internal organs
multi-unit, no gap junctions, each individual musce fibre is separately innervated
on a whole muscle level what are teh differences betweeen smooth and skeletal muscle
contraction of smooth muscle changes muscle shape, not just lenghth
smooth muscle develops tension (force) slowly
smooth muscle can maintain contraction longer withought fatiguing, important because some are conracted most of the time
differences between smooth and skeletal level in a cellular level
page 79
what is the effect of not having T-tubles
page 80
difference between skeletal and smooth muscle in a molecular level
page 80
explain smooth muscle contraction
page 80
what are the 3 channells that Ca2+ enters through
voltage-gated channels , open when cell depolarizes
stretch-activated channels, open when membrane stretched
chemically-gated channels, open in response to hrmones
explain relaxation in smooth muscleq
page 81
what are cardiac msucle
specialized muscle cells of the heart, shares features with both smooth and skeletal msucles
most myocardial cells are typically……
striated and contractile fibers organixed into sarcomeres
how are cardiac muscle different from sckeletal muscle:
cardiac muscle cells are much smaller with single nucleus with about 1/4 of the cell volume is occupied by mitochondria, allows for sommunication in both direction
T-tubles are much alarger and branched and the sarcoplasmic reticulum is smaller
adjecent cells are joined by intercalated discs with desmosomes
how much is not incoleced in conractio of the cardiac muscle cell, but what are they iinvolved in
1% they are involved int he electrcal excitation of the heart, known as the electrical conducting sustem of the heart
they initiate heartbeat and allow the elecctrical excitation to spread rapidly throught the heart
they are connected to other cardiac cells via gap junctions
explain cardiac muscle contraction
page 83
what are teh factors influencing cardiac muscle contraction force
- changes in (Ca2+)
explained in 83
cardiac muscle is also what
an excitable tissue and can generate action potientions
explain the major sequence of evetnts of a cardiac muscle
page 86
why does sustained depolarization occur
because of the slow opening of the voltahe-gated Ca2+ channels
