Muscle Tissue Flashcards
What are the 4 Main functions of muscle tissue
Produce the Body movements, Maintain posture, Move Substances within the body, and Generate heat
What are muscle tissues composed of
Composed of elongated cells called myocytes or muscle fibers
What are the three types of muscle tissue
- Skeletal muscle
- Cardiac muscle
- Smooth muscle
What does a Skeletal muscle tissue require to contract
Requires innervation from a somatic motor neuron to contract
What is it called when a a muscle tissue doesn’t have a innervation
Atrophic
The muscles are separated from the skin by the subcutaneous layer or hypodermis composed by________ and _____________
Adipose tissue
Areolar tissue
What is Epimysium
Outer layer encircling the whole muscle
What is Perimysium
Surrounds bundles of 10-100 cells forming fascicles
What is Endomysium
Separates each individual muscle fiber from each other
What is a tendon
Tendons are rope-like extensions of the three connective tissue layers(1. Epimysium, 2. Perimysium
3. Endomysium) beyond the muscle fibers attaching the muscle to the periosteum of a bone
What does Fascia do
- Supports and surround the muscles and other organs of the body
- Holds together muscles with similar functions
- Allows free movement of muscles
- Carries the nerves, blood vessels, and lymphatics
Where do you see cardiac muscle tissue
Occurs only in the heart
Is Cardiac muscle tissue faster then Skeletal Tissue
Moderate speed of contraction, not as fast as skeletal muscle
How are the cardiac muscles attached to each other
The cells are strongly attached end-to-end by the intercalated discs
The Intercalated Discs are kept by_______ and ________
- Desmosomes
• Weld-like junctions preventing separation
of the cells during strong contractions
2. Gap junctions • Allow for very fast communication between many connected cells, which contract all at once with the same nerve impulse
What happens if the heart is cut off from innervation
Capable of contraction by auto-stimulation
If innervation was cut off, still the heart can contract
build-in rhythm of the heart is called
_______
autorhythmicity
What 2 things can adjust the heart beat by acting on the pacemaker
Hormones and neurotransmitters
What do Smooth Muscle Tissue look like
Non striated, spindle-like cells, thicker at the center with a single, centrally- located nucleus
Are smooth muscles voluntary or involuntary
Involuntary muscle innervated by the ANS (autonomic nervous system)
The Smooth Muscle: two types?
- Visceral (single unit) smooth tissue
• Skin, hollow organs like stomach, intestines, uterus, bladder
• Fibers connect by gap junctions and contract in unison as a single unit - Multi-unit smooth tissue
• Large arteries, airways, arrector pili, iris, ciliary body
• Individual fibers with own nerve
• Few gap junctions between neighboring cells
The Smooth Muscle Tissue are Located in:
- The walls of hollow internal organs
- The skin
- Blood vessels
- Airways
- Organs of abdominopelvic cavity
Are Smooth Muscle Tissue fast or slow
Slow speed of contraction
What are myocytes
The muscle cell, also known as the myocyte is the smallest subunit of all muscular tissues and organs throughout the body
The mature skeletal muscle cell measures about __ mm
in length, some can reach __ mm
The mature skeletal muscle cell measures about 10 mm
in length, some can reach 30 mm
What is the Sarcolemma of the Muscle Cell
Sarcolemma: is the plasma membrane
of the muscle cell
What are the Transverse (T) tubules of the Sarcolemma
Thousands of invaginations of the sarcolemma
toward the center of muscle cell
What are Transverse (T) tubules filled with
T tubules are filled with extracellular fluid allowing for the instant stimulation of all parts of the cell simultaneously with the same stimulus
What is the Sarcoplasm of the Muscle Cell
Sarcoplasm: is the cytoplasm of the muscle cell
What does Sarcoplasm contain
It contains:
• Large amounts of glycogen
- Myoglobin (protein only found in muscle)
- Abundant mitochondria close to the contractile proteins
• Myofibrils: the contractile organelles
that contain the myofilaments (thin
and thick)
• Sarcoplasmic reticulum (SR) membranous sacs encircling each myofibril. The dilated ends of the SR are called terminal cisterns. A T tubule and two terminal cisterns form a triad
• The SR stores calcium ions for the
muscle contraction
What is Myoglobin
protein only found in muscle
What are Myofibrils
the contractile organelles that contain the myofilaments (thin and thick)
What is the Sarcoplasmic reticulum (SR)
membranous sacs encircling each myofibril. The dilated ends of the SR are called terminal cisterns. A T tubule and two terminal cisterns form a triad
• The SR stores calcium ions for the muscle contraction
The myofibrils contain smaller protein structures called the filaments or___________
myofilaments
What are the two myofilaments
- Thin filaments are composed of protein actin
* Thick filaments are composed of protein myosin
What is a sarcomere
The filaments inside one myofibril are arranged in compartments called The Sarcomeres
The Sarcomeres are the basic functional units of a myofibril
How are the Sarcomere separated
The Sarcomeres are separated from each other within the muscle cell by a dense protein material called the Z discs
One sarcomere extends from one Z disc to the next Z disc
The myofibrils are built from three kinds of proteins:
- Contractile:
• Generate the forces for contraction - Regulatory:
• Help switching the contraction process on and off - Structural:
• Keep the thin and thick filament aligned
• Provide elasticity and extensibility
• Link the myofibrils to the sarcolemma
What is a Motor Unit
A motor neuron innervating a group of muscle fibers is called a Motor Unit
What does the motor unit need to contract
The motor unit requires the stimulation of the motor neuron to contract
The site where the communication between the motor neuron and the muscle cell occurs is called the _______
neuromuscular junction (NMJ)
How does the Sliding Filament Mechanism result in
muscle contraction?
The skeletal muscle cell shortens because the thick and thin filaments slide pass each other
How does the Sliding Filaments Mechanism work?
- Myosin pulls on actin, causing the thin filament to slide inward
- Consequently, Z discs move toward each other and the sarcomere shortens
- Thanks to the structural proteins, there is a transmission of force throughout the entire muscle, resulting in whole muscle contraction
What is the Role of the Intracellular Calcium
AN INCREASE of calcium within the muscle cell
(in the sarcoplasm) starts the filament sliding
The muscle contracts
What happens After the excitatory electrical impulse has expired
An active transport system pumps the calcium back
to its “prison” within the Sarcoplasm Reticulum (SR)
What happens when a decrease of calcium within the muscle cell happens
Turns off the sliding process
The muscle turns back to its original length
The muscle relaxes
what is adenosine triphosphate molecule (ATP)
The adenosine triphosphate molecule (ATP) provides the energy for muscle contraction
How much ATP is stored inside the muscle
Only little ATP is stored inside the muscle
How long can the ATP in the muscles power them
There is just enough ATP in the muscle to power muscle contraction for a few seconds
Production of ATP in Skeletal Muscle: three sources
- ATP from Creatine phosphate (15 sec)
- ATP from anaerobic glycolysis (2 Min
- ATP from aerobic respiration (several Min-HR)
When does muscle fatigue occur? 5 reasons
The muscle cannot produce enough ATP Insufficient oxygen Depletion of glucose Build up of lactic acid Some unexplained mechanisms
What are Isotonic Contractions
Occur when a constant load moves
through the ROM at a joint
The tension (muscle tone) remains almost constant during such contraction
There are two types of Isotonic Contractions:
- Concentric Contraction
The muscle shortens and pulls on another structure (For example, the flexion of the
forearm by the biceps brachii.) - Eccentric Contraction
The overall length of the muscle increases during contraction (For example, during the extension
of the previous movement)
What is a Isometric Contraction
The muscle does not or cannot shorten but the tension of the muscle increases greatly
What are Twitch Contractions?
Brief contraction of the entire motor unit from a single stimulation.
The eyeball muscles are fast-twitch
What are the proprioceptors?
Receptors imbedded in the muscles, they allow the recognition of our own body. We can locate our head and limbs even when we are not looking at them
The brain is constantly receiving information related to body parts positions. So, continuous adjustments are made to ensure coordination
The Proprioceptors Include:
- Muscle Spindles
• Within skeletal muscles - Tendon Organs or Golgi Tendon Organ (GTO)
• Within tendons
High myoglobin content are the___________
red muscle fibers
• Contain more mitochondria
• Better blood supplied
Low myoglobin content are the
white muscle fibers
The three Types of Skeletal Muscle Fibers:
- Slow Oxidative (SO) Fibers
- Fast Oxidative-Glycolytic (FOG) Fibers
- Fast Glycolytic (FG) Fibers
What are Slow Oxidative (SO) Fibers
- Dark-red colored, high myoglobin content. Highly blood supplied
- Generate ATP by aerobic respiration (oxidative)
- Contraction cycle proceeds at a slow pace
- Twitch contractions last from 100-200 msec
- Longer to reach peak tension
- Very resistant to fatigue
- Capable of prolonged sustained contraction
- Adapted to maintain posture, aerobic, endurance-type of activities (marathon running)
What are Fast Oxidative-Glycolytic (FOG) Fibers
- The largest fibers
- Dark-red appearance
• Contain large amounts of myoglobin. Highly blood
supplied
- Can generate large amount of ATP by aerobic respiration
- Moderate resistance to fatigue
- Generate ATP by anaerobic glycolysis too
- Twitch contractions last less than 100 msec
- FOG fiber muscles contribute in walking and sprinting
What are Fast Glycolytic (FG) Fibers
- Low myoglobin content. Few blood capillaries
- Appear white color
- Contain large amount of glycogen
- Generate ATP mainly by glycolysis
- Contract strongly and quickly
- Adapted for intense anaerobic movements of short duration
- Strength training requiring great strength for short times increase these fibers
- Fatigue very quickly
- FG fibers are used for weight lifting and throwing balls
What is Motor Unit Recruitment
Motor units recruitment is the process in which the number of active motor units increases
Weakest motor units are recruited first followed by stronger motor units
Motor units contract alternately to sustain contractions for longer periods of time
What is the distribution of Types of Fibers
Most skeletal muscles are a mixture of all three types of fibers
About 50% of a typical skeletal muscle are SO fibers
The ratio FG to SO fibers is genetically determined
Neck, back and leg postural muscles have higher proportion of __ fibers
SO
Proximal muscles of the upper limb have higher proportion of __ fibers
FG
Lower limb muscles have large number of __ and ___ fibers
SO and FOG
