A&P Chapter 9 Flashcards
Contractibility
Ability of a muscle to shorten with force.
Functions of the Muscular System
Body movement, posture, respiration, body heat production, communication, constriction of organs and vessels, heart beat.
Excitability
respond to a stimulus.
Extensibility
Stretch to a limited degree. Muscles can stretch when needed.
Muscle types
Skeletal: Body movements; voluntary.
Smooth: walls of hollow organs; involuntary
Cardiac: Heart; involuntary.
Fasciculi
bundles of fibers
Perimyseum
connective tissue surrounding fasciculi.
Epimysium
connective tissue surrounding entire muscle.
Motor Neurons
nerve cells that stimulates muscle contraction.
Neuromuscular Junctions
contact points between axons and muscle fibers.
Muscle fiber development
Precursor cells –> myoblasts –> multinucleated cells
Sarcolemma
Plasma membrane of muscle fiber
Sarcoplasmic reticulum
Modified smooth endoplasmic reticulum
Sarcoplasm
Muscle cytoplasm
Myofibril
Threadlike connections between fibers
Actin
Thin myofilaments
Myosin
Thick myofilament
Sarcomere
Basic structural unit and functional skeletal muscle.
Actin+ myosin
Powerhouse of the muscle
Z-disk
Attachment point for actin
Z network
ligand-gated ion channels
ligand binds to receptor channel
ion channel opens to allow ion to enter cell
voltage-gated ion channels
open and close in response to voltage changes
Resting membrane potential
resting= negative ions inside, positive ions outside
depolarization phase
opening of channels and triggers contraction
repolarization phase
closing of channels and relaxation
calcium
release causes contraction
muscle twitch
lag phase: time between stimulus and contraction.
contraction phase: time of contraction
relaxation phase: time of relaxation.
Summation
repeated stimulation (stimulus strength and response)
Recruitment
increased number of fibers (stimulus strength and response)
Subthreshold stimulus
no contraction
Threshold stimulus
contraction
submaximal stimuli
additional motor units
maximal stimuli
all motor units
stimulus frequency
contraction increases as stimuli increases
repeated stimulation inhibits resting.
incomplete tetanus
fibers partially relax between contractions.
complete tetanus
no relaxation between contraction.
isometric (muscle contraction)
no change in length but tension increases.
- postural muscles of the body.
isotonic (muscle Contraction)
change in length but tension remains constant.
- Concentric: overcomes opposing resistance and muscle shortens.
- eccentric: tension maintained but muscle lengthens.
muscle tone (muscle contraction)
constant tension by muscles for long periods of time
fatigue
decreased capacity to work and reduced efficiency of performance.
Fatigue Types
psychological: depends on mental state of individual.
Muscular: results form ATP depletion.
Synaptic: occurs in NMJ due to lack or acetylcholine.
Physiological Contracture
state of fatigue where due to lack of ATP neither contraction nor relaxation can occur.
Rigor Mortis
development of rigid muscles several hours after death. Calcium leaks into sarcoplasm and attaches to myosin heads and crossbridges form. Ends when tissue start to deteriorate.
Slow Twitch
Respond slow to stimulation
resistant to fatigue
Fast twitch
respond slow to stimulation
fewer mitochondria
prone to fatigue ra
Atrophy
decrease in size due to inactivity
Heat production
exercise: metabolic rate and heat production
Post-exercise: metabolic rate stays high due to oxygen debt.
Shivering: uncoordinated contraction of muscle fibers resulting in shaking and heat production.
Types of Smooth Muscle
Visceral or unitary : cells in sheets, function as a unit.
–numerous gap junctions; wave of contraction
– digestive and reproductive tracts
Multiunit: cells or groups of cells act as independent units.
– Sheets(blood vessels ); bundles(arrector pili and iris); single cells (capsule of spleen)
