Muscles Flashcards
Cardiac Muscle Tissue
Forms most of the heart wall
Is striated
Is involuntary
Can regenerate under certain conditions
Skeletal muscle tissues
Is attached to bones and moves part of the skeleton
Is striated (alternating light and dark bands)
Is voluntary (conscious control)
Has limited capacity for regeneration
Smooth muscle tissue
Located in the walls of hollow internal structures like blood vessels, airways and the stomach
Not striated
Is voluntary
Compared to other muscles it has a considerable capacity to regenerate
Functions of the muscle tissue
Producing body movements like running or walking
Stabilizing body positions like sitting or standing
Regulating organ volume by using ring muscles called sphincters to close off outlets from the stomach and bladder
Moving substances within the body like blood, food, sperm, eggs
Producing heat from the contraction of muscles
Skeletal muscle is composed of
Cells called muscle fibers
Epimyseum
CT that wraps the muscle fibers
Perimyseum
CT that surrounds a fascicles which is a bundle of 10-100 muscle fibers
Endomyseum
CT that wraps each individual muscle fiber
Tendon
A cord formed from the extension epimyseum, perimyseum, and endomyseum. It attaches the muscle to a bone.
What are skeletal muscles supplied with?
Nerves and blood vessels which provide nutrients and oxygen for the production of ATP
Sarcolemma
The name for the plasma membrane
T-tubules (transverse tubules)
Tunnel like inward extensions of the sarcolemma
Nuclei
Each muscle fiber contains multiple nuclei
Sarcoplasm
The name for the muscle fibers cytoplasm
Mitochondria
Makes large amounts of ATP for muscle contraction
Sarcoplasmic Reticulum (SR)
Similar to the endoplasmic reticulum; it stores calcium ions needed for muscle contraction
Myoglobin
Reddish pigment that stores oxygen until it is needed by the mitochondria to produce ATP
Myofibrils
Cylindrical structures within and extending the length of the muscle fiber
They contain thin and thick filaments (do not run the entire length of the muscle fiber)
Thick filaments
Made up of protein called myosin
Thin filaments
Contains the protein actin
Sarcomere
Compartment within the myofibril formed from the filaments of the thick and thin filaments
Basic functional unit of the muscle fiber
Z-discs
Zig zag zones that separate one sarcomere from the next
Sliding filament mechanism
During muscle contraction myosin heads of the thick filaments pull and slide on the thin filaments causing the thin filaments to pull toward the center of the sarcomere
When the filaments slide past each other it causes the sarcomere to get shorter causing the shortening of the entire muscle fiber
Ca+ must be high enough and there must be enough ATP available
Neuromuscular Junction
Nueromuscular junction is the synapse (connection) between a motor neuron and muscle fiber
Motor Neuron
A nerve cell that delivers an electrical signal called a muscle action potential (nerve impulse)
The message is what tells the muscle it’s time to contract
Motor unit- a single motor neuron plus all of the muscle fibers it stimulates. Stimulation of one motor unit causes all the fibers in the motor unit to contract at the same time
Axon terminal- the end of the axon (long process) of a motor unit that approaches but does not touch the sarcolemma of a muscle fiber. The ends of the axon terminal enlarge into synaptic end bulbs. The synaptic end bulbs contains sacs called synaptic vesicles which are filled with a chemical called acetylcholine (ACh) a neurotransmitter
Synaptic cleft
The space between the axon terminal and the sarcolemma of a muscle fiber
Motor end plate
The region of the sarcolemma near the axon teriminal; it contains millions of ACh receptors
When nerve impulses arrive at the synaptic end bulbs:
ACh is released from the synaptic vesicles. It diffuses across the synaptic cleft.
ACh binds to the receptors in the motor end plate. This opens ion channels in the sarcolemma that allow sodium ions to flow across the membrane and enter the muscle fiber
As a result the sodium ions rushing in, actin potential is generated which flows along the sarcolemma and through the t-tubules
Acetylholinesterase (AChE) breaks down ACh
Two things are needed for muscle contraction
Ca+
Energy
When a muscle fiber is relaxed:
Ca+ is found in the sarcoplasmic reticulum. When muscle action potential travels into the SR Ca12 is released into the sarcoplasm where it uncovers myosin biding site of the thin filaments
Contraction occurs:
As ATP is split into ADP and P and energy is transferred into myosin
The power stroke occurs
Myosin, the thick filaments slide the thin filaments, actin toward the center of the sarcomere
Energized myosin heads
Form cross bridges that attach to actin
Relaxation
ACh is broke down by AChE
Ca+2 are pumped back into the sarcoplasmic reticulum
Rigor mortis
After a person dies Ca+2 leaks out of the sarcoplasmic reticulum causing the thin filaments to slide and the muscles to stiffen
Lasts about 24 hours
Muscle tone
There is a continual involuntary activation of a small number of motor units even when the whole muscle is not contracting
Needed to maintain posture
Flaccid
Very limp
ATP
Produced by mitochondria
Provides energy for the moving thick filaments cross bridges when split
ATP–> ADP+P+Energy
Enough power contraction for only a few seconds
Creatine phosphate
The transfer of high energy phosphate group from creatine phosphate to ADP forms new ATP molecules
CP+ADP–> ATP+ creatine
Creatine phosphate and ATP provide enough energy for muscles to contract for about 15 seconds
Anaerobic cellular respiration (glycosis)
Found in the blood. Also produced within muscle fibers by the breakdown of glycogen, it’s storage form
Glucose is converted into pyruvic acid in these reactions which produce 2 ATPs without oxygen
1 glucose + 2 pyruvic acid –> 2 ATPs
Enough energy for 30-40 seconds
Aerobic cellular respiration
Mitochondria use oxygen to convert glucose to ATP
1 glucose –> O2 + 2 pyruvic acid –> CO2 + H2O + 36 ATP
10 minutes of activities
Muscle fatigue
Inability of a muscle to contract forcefully after prolonged activity
Recovery oxygen uptake
Elevated oxygen use after exercise
Twitch contraction
A brief contraction of all muscle fibers of a motor unit in response to a single action potential stimulus
Myogram
Recordings of muscle contractions
Latent period
Time between application of stimulus and actual shortening of the muscle fiber
Contraction period
Actual contraction is taking place
Relaxation period
Re-lengthening of the muscle
Wave summation
Increased strength of contraction that occurs when a second stimulus arrives before the muscle has completely relaxed after a previous stimulus
Infused tetanus
Repeated stimuli cause a sustained wavering contraction with partial relaxation between stimuli
Fused tetanus
Faster repeated stimuli cause a sustained muscle contraction without partial relaxation between stimuli
Motor unit recruitment
The process of increasing the number of contracting motor units. It allows for smooth movements to occur
Isotonic contractions
Tension remains relatively constant but length changes allowing movement
Isometric contraction
Muscle length does not or cannot change, but tension increases. This acts to stabilize posture
Aging effects on skeletal muscle
Skeletal muscle is slowly replaced with fibrous CT and adipose
Decrease in strength
Slow muscle reflexes
Loss of flexibility
Muscle tone
Slight
Constant contraction during consciousness
Isotonic
Shortens the muscle and causes movement
Isometric
Increases muscle tensions but no movement occurs
Tetanus
Continuous sustained contraction allowing smooth movement
Summation
“Stairstep” increase in contraction with repeated stimulation before muscle has completely relaxed
Essential for maintaining posture
Muscle tone
The third phase of muscle twitch contraction
Relaxation
These structures in the enlarged bulbs of an axon provide energy to make ACh
Mitochondria
State of limpness
Flaccid
Cytoplasm of a muscle fiber
Sarcoplasm
This tissue is responsible for most of the heat production going on in the body
Muscle tissue
The movement of these ions from outside the sarcolemma to inside causes an action potential to begin to move along
Sodium
These ions are necessary to trigger muscle contraction
Ca+2
Stored in the SR
Dietary supplement that some studies show may result in more lifting power
Creatine
The storage form of glucose in our liver and muscles
Glycogen
This anaerobic process provides enough energy for 30-40 sec of maximal activity
What is glycolysis
The connective tissue that attaches muscle to bone
Tendon
The source of energy for muscle contraction
ATP
What is another name for action potential?
What is nerve impulse
This is required by mitochondria in the aerobic production of energy for muscle contraction
What is oxygen
Another name for muscle cells
What is muscle fiber
This is the cell membrane of muscle cells
What is sarcolemma
The alternate light and dark bands running through the sarcoplasm of a muscle cell is
Straition
A single nerve fiber and the muscle fiber it supplies
What is motor unit
A chemical necessary to transfer the nerve impulse to stimulate the muscle
What is acetylcholine
The time between the application of a stimulus and the actual shortening of the muscle
Latent period
The two types of skeletal muscle contractions needed for normal body movements
Isotonic and tetanus
The connection between nerve fiber and muscle fiber is
Neuromuscular junction
A brief contraction of all muscle fibers of a motor unit in response to a single stimulus
What is a twitch
Most of the Co+2 is found here when a muscle fiber is relaxed
Sarcoplasmic reticulum
A stiffening of the muscles after death due to Ca+2 leaking out of the sarcoplasmic reticulum
What is rigor mortis
Name the major function of muscles
Movement, position, volume substances heat
The neurotransmitter released from the synaptic vesicles of neurons supplying skeletal muscle
ACH
What is the thick myofilament that has enlarged heads to form cross bridges
What is myosin
ATP—-ADP + phosphate group +energy
For contraction
CP+ ADP—-creatine + ATP
Creatine pathway
Glucose——-pyruvic acid——2ATP
No oxygen
Glucose—–O2 + pyruvic acid-CO2 + H2O + 36ATP
Oxygen
