A&P I Ch.10 & 11 Flashcards
Primary Functions of Skeletal Muscles
-movement
-support
-posture
-temperature regulation
-communication
Skeletal Muscle Function of Movement
- create movement by contracting
- pull on tendons which are connected to bones
Skeletal Muscle Function of Support
- muscles in abdominal wall support visceral organs
- shield tissue from injury
Skeletal Muscle Function of Posture
- muscles continuously contract to hold the body still, maintaining upright/ standing position
Skeletal Muscle Function of Temperature Regulation
- skeletal muscle is 40% of our body mass
- it has disproportionate effect on body temperature
Skeletal Muscle Function of Communication
- facillitates all modes of interpersonal communication
-e.g. speaking, typing, writing, facial expressions, and gestures
Functional Characteristics of Skeletal Muscle
-Contractibility
-Excitability
-Extensibility
-Elasticity
Functional Characteristics of Skeletal Muscle Contractibility
ability of muscle to shorten and produce tension at its ends
-pulls on tendons
Functional Characteristics of Skeletal Muscle Excitability
ability of a muscle fiber to respond rapidly to electrical or chemical signals (from neurons)
Functional Characteristics of Skeletal Muscle Extensibility
capacity of muscle to stretch to normal resting length and beyond after contraction
Functional Characteristics of Skeletal Muscle Elasticity
capacity of muscle to return to its normal resting length after a stretch
Plasticity
muscle’s ability to constantly adapt to stretching
Skeletal Muscle Macrostructure Red
muscle tissue
Skeletal Muscle Macrostructure White
tendons
What are the criteria for skeletal muscle naming?
-muscle action
-specific body regions
-muscle attachments
-orientation of muscle fibers
-muscle shape
-muscle size
-number of muscle heads at an attachment site
Muscle Action Meaning and Example
indicates muscle’s primary action
ex. flexor digitorum longus (flexes digits)
Specific Body Regions Meaning and Example
indicates muscle location
ex. rectus femoris is near the femur
Muscle Attachments Meaning and Example
indicates origins and/or insertions
ex. sternocleidomastoid originates on the sternum and clavicle and inserts into the mastoid process of the temporal bone
Orientation of Muscle Fibers Meaning and Example
indicates organization of muscle fascicles
ex. rectus abdominis is composed of fibers running in vertically straight (“rectus”) orientation
Muscle Shape Meaning and Example
ex. deltoid is like a triangular delta symbol
ex. abductor pollicis longus is a long tendon
Muscle Size Meaning and Example
ex. gluteus maximus is the largest of the buttocks muscles
Number of Muscle Heads at an Attachment Site Meaning and Example
indicates number of muscle bellies or heads each contains at the superior or proximal attachment site
ex. triceps brachii has three heads
Three concentric layers of wrapping connective tissue components
-epimysium
-perimysium
-endomysium
Epimysium
-dense irregular tissue wrapping whole muscle
-fibrous connective tissue sheath that surrounds the entire muscle
Perimysium
-dense irregular connective tissue wrapping fascicle
-houses many blood vessels and nerves
Endomysium
-areolar connective tissue wrapping individual fiber
-delicate layer for electrical insulation, capillary support, binding of neighboring cells
Blood Vessels and Nerves
- skeletal muscle is vascularized, has extensive blood vessels
-deliver oxygen and nutrients, removing waste products - skeletal muscle is innervated by somatic neurons
-axons of neurons branch, terminate at neuromuscular junctions
-can allow for voluntary control of contraction
Tendon
tough band of fibrous connective tissue connecting muscle to bone
Perymisium and Endomysium
provide anchorage and support to local nerves and blood vessels
What structure connects muscle to bone?
Tendons
Structure of the Sarcomere
-smallest contractile unit of skeletal muscle
-repeating units of longitudinally- arranged actin and myosin
-allow for sliding filament model of muscle contraction
-boundaries formed by Z-lines
Inferior Structure of a Muscle Fiber
- Thin
-F-actin
-G-actin - Thick
Thin Filament
looks like pearls on a string
F-actin
-thin filament
-initiates many cellular processes including cell motility and muscle contraction
G-actin
-thin filament
-the monomer from which F-actin is formed
Thick Filament
filament looks like double-headed golf clubs
The sliding filament model of muscle movement
1) Calcium ions bind to troponin on actin’s active site
2) Myosin binds actin to form a cross- bridge (“cocked” formation)
3) Phosphate is released, the myosin head moves into low-energy conformation and actin slides towards the M line (“Powerstroke”)
4) A new molecule of ATP replaces ADP (cross-bridge detachment)
5) Cross-bridges break and the cycle repeats
Which part of the sarcomere forms its boundaries?
Z line
A Band
Actina and Myosin
H Zone
Myosin shrinks when actin is pulled to midline (M-line)
I band
Actin
True or False? Actin Filament is thin while Myosin Filament is thick
True: “Actin (thick) filament”
“Myosin (thin) filament
Motor Units Include a Motor Neuron and the muscle fibers it ___________
Innervates
Motor Unit
-in the brain sends impulses
-impulse travels through spinal cord to motor neuron
-muscle action potential stimulated, and sacromeres slide
Neuromuscular Junctions
dump acteocholine
Motor Unit
- Axons of motor neurons from spinal cord (or brain) innervate numerous muscle fibers
- The number of fibers a neuron innervates varies
-small motor units have less than five muscle fibers
–alow for precise control of force output
-Large motor units have thousands of muscle fibers
–allow for production of large amount of force (but not precise control) - Fibers of a motor unit are dispersed throughout the muscle (not just in one clustered compartment)
The __________ ___________ is a chemical synapse between an alpha motor neuron and a muscle fiber
Neuromuscular Junction
Neuromuscular Junction (NMJ)
- where the axon terminal of an alpha motor neuron and the membrane of a muscle fiber meet
- stimulation causes build-up of intracellular Na+, exit of intracellular Na+, exit of intracellular K+
- graded potentials lead to action potentials of Ca2+ release
- stimulation ends when acetylcholinesterase (breaks bonds) degrades Ach in synaptic cleft
1) Neuromuscular Junction: Excitation of Skeletal Muscle Fiber
- 1a) Calcium entry at synaptic knob
- 1b) Release of ACh from synaptic knob
-1c) Binding of ACh at motor end plate
Calcium entry at the synaptic knob
-nerve signal travels down (propagated down) the axon, opens voltage-gated Ca2 channels (triggers entry)
-Ca2 diffuses into the synaptic knob
-Ca2 binds to proteins on surface of synaptic vesicles
Release of ACh from synaptic knob
-vesicles merge with cell membrane at synaptic knob exocytosis
-thousands of ACh molecules released from about 300 vesicles
- calcium binding triggers synaptic vesicles to merge with the synaptic knob plasma membrane and ACh is exocytosed into the synaptic cleft
Binding of ACh at motor end plate
- ACh diffuses across the fluid-filled synaptic cleft at the motor end plate to bind with ACh receptors
- Excites Fiber
Steps of a Complete Muscle Contraction
1) ACh binds to muscle fiber
-make graded potential
2) Action potential moves into T tubules
3) Ca2+ is released by sarcoplasmic reticulum
4) Ca2+ binding, cross-bridge formation
5) Muscle Contraction; uses ATP
6) Acetylcholinesterase degrades ACh
7) Ca2+ reabsorption into sarcoplasmic reticulum
8) Active sites become unexposed
9) Further sliding prevented
Supplying Energy for Skeletal Muscle Metabolism
- Muscles only have a little ATP in storage
-Stored ATP is spent after 5 seconds of intense exertion - Addiotional ATP rapidly produced via mypokinase (shuttle phosphates)
-Phisphate transferred form one ADP to another to make ATP
Three ways to generate additional ATP in skeletal muscle fiber
-creatine phosphate
-glycolysis
-aerobic cellular respiration
Creatine Phosphate
- contains high-energy bond between creatine and phosphate
- phosphate can be transferred to ADP to form ATP
- catalyzed by creatine kinase (break the bond take the phosphate)
- 10-15 seconds of additional energy
Glycolysis
-does not require oxygen (anaerobic)
-Glucose (from muscle’s glycogen or through blood) is converted to two pyruvate molecules
-2 ATP released per glucose molecule
-occurs in cytosol
Aerobic Cellular Respiration
- requires oxygen
- occurs within mitochondria
- pyruvate oxidized to carbon dioxide
-transfer of chemical bond energy to NADH and FADH2
-energy used to generate ATP by oxidative phosphorylation
–produces a net of 32 ATP - Triglycerides can also be used as fuel to produce ATP
-More ATP from tiglcerides with longer fatty acid
ATP from Muscle Fibers
5 seconds (short and intense exercise)
ATP from Creatine Phosphate and ADP
10 seconds (short and intense exercise)
ATP from Anaerobic Glycolysis
40 seconds (short and intense exercise)
ATP from Aerobic Pathway
hours (prolonged exercise)
How many seconds of energy does a 50-meter sprint require?
-less than 10 seconds
-ATP supplied primarily by phosphate transfer system
How many seconds of energy does a 400-meter sprint require?
-less than one minute
-ATP supplied primarily by glycolysis after first few seconds
How many seconds of energy does a 1500-meter sprint require?
-more than one minute
- ATP supplied primarily by aerobic processes after first minute
How does a muscle get most of its energy at rest?
aerobic metabolism
Fatigue inducing situations
-Lactic Acid build-up (makes blood more acidic) after high-intensity exercise
-Glycogen depletion after medium-intensity exercise over long periods of time
Muscle Fatigue
muscles cannot continue contractions even under nervous stimulation
Lactic Acid Removal
-Lactic Acid can be recycled back to pyruvic acid
-used by mitochondria to generate ATP or rebuild glycogen reserves
-also shuttled through the blood to the liver and back to the muscle (Cori cycle)
High-Intensity Exercise
-maintains/ improves muscular strength, endurance, mass, size, metabolic capacity, power, resting metabolic rate, bone mineral density and overall physical function
Muscle Soreness
- delayed-onset muscle soreness (DOMS) usually lasts 3-4 days and is most intense after eccentric contractions
- May be caused by very small muscle tears or injury to connective tissues/ tendons
- Principle of overload: body adapts after rest and becomes stronger
Locations of Smooth Muscle
- blood vessels of cardiovascular system
-helps regulate blood pressure and flow - bronchioles of respiratory system
-controls airflow to alveoli - intestines of digestive system
-mixes and propels materials - ureters of urinary system
-propels urine from kidneys to bladder - uterus of female reproductive system
Structure of Smooth Muscle Cells and Tissue
- smaller than skeletal muscle cells
- spindle-shaped
- have centrally-located nucleus
- no t-tubules or visible sarcomeres
- do not fuse during development
- connected by junctions
-have membrane invaginations called caveolae
Main Functions of Smooth Muscle
-line walls of hollow organs
-responsible for involuntary movements
-contraction/ relaxation of passageways to allow flow (e.g. respiratory passageways or blood vessels)
-contraction of organs (e.g. uterus)
Main differences of Smooth Muscle from Skeletal Muscle
- smooth muscle produces more force and achieves greater change in size
-smooth muscle is regulated at the level of myosin phosphorylation rather than troponin binding
-smooth muscle contraction is involuntary, slower, and able to endure
-smooth muscle can contract phasically
What are the two categories of Smooth Muscle?
Multiunit and Single Unit
Multiunit Smooth Muscle
- arranged in units that receive stimulation to contract individually
-found in many areas
-degree of contraction depends on number of motor units activated, similar to skeletal muscle
In what areas are Multiunit Smooth Muscles found?
-iris and cilliary muscles of the eye
-arrector pilli muscles in skin
-large air passageways in respiratory system
-walls of larger arteries
Single-unit (visceral) Smooth Muscle
-most common type
-stimulated to contract in unison as cells linked by gap junctions
-form two or three sheets in wall of hollow organ
-in many locations
In what locations are single-unit smooth Muscles found?
-walls of digestive, urinary, and reproductive tracts
-portions of respiratory tract
-most blood vessels
Origin
muscles’s proximal attachment, typically moves the least
Insertion
muscle’s distal attachment typically moves the most
Agonist
mucle or muscle group most directly involved in movemnet
Antagonist
opposing muscle group; slows down limbs during fast movement
Synergist
muscles that stabilize the body during movement but are not responsible for the movement
Definition of Isotonic Contractions
generation of muscle force with constant muscle tension and change in muscle length
Concentric
-isotonic contraction
-contractile force is greater than external load
-muscle shortens
-more
Eccentric
-isotonic contraction
-contractile force is less than external load
-muscle lengthens
-less
Definition of Isometric Contractions
active muscle contraction without changing the muscle length
-equal
Example of isometric contractions
“stalemate” during arm wrestling match
During what type of muscle contraction(s) does the muscle length change?
Concentric and Eccentric
Endurance exercise leads to _______ _____ __________.
better ATP production
Resistance exercise leads to ____________.
hypertrophy
Hypertrophy
-muscle increases in size due to increases in synthesis of contractile proteins
-muscle also increases glycogen reserves and mitochondria
-limited amount of hyperplasia (increase in number of fibers)
Atrophy
-change in muscle from lack of exercise
-decrease in size due to lack of use
-ex. someone wearing a cast
-initially reversible but becomes permamanent if extreme
