Anatomy 3 exam

4 Functions of muscle tissue

Movement of body parts

Stabilization of body position/posture and joints

Storage and movement of substances(blood, urine, foodstuffs): entrances and exits guarded by muscle sphincters

Heat generation: shivers

Supports soft tissue

signs of skelteal muscle isssues

and how to test

Weakness in the muscles in the arms during repeated contraction

Droopy eyelids, face, and jaw

Test with eletomypographic studies

Properties of all muscle tissue

Electrical excitability / irritability / conductivity (Response to stimuli with an electrical signal that produces contraction and leads to an action potential)

Contractility (shortens forcefully)

Extensibility (can be stretched or extended)

Elasticity (returns to resting length)

Muscle cells: nucleus is where?

in the muscles cells that are pink

skeletal muscle structure, function and special properties

Structure: nucleus and pushed off to the side because of so many contractile components

• Muscle fibers(muscle cells) are very long and run as long as the organ

• Striated with parallel fibers

Function: connects muscle to bone to control voluntary movements and the 4 functions like protecting organs in the thoracic and abdominopelvic cavity; generates heat

Special properties: can be multinucleated

cadiac muscle, structure, function and special properties

Structure: nucleus is more circular

• muscle fibers/cells branch in a Y formation

• intercalated discs where the cells come together at the ends (helps with twisting so that when the heart contracts it becomes a smaller cavity, not just shorter)

• stratied

function: Contraction causes the involuntary movements of heart chambers to become smaller, pumping blood out of the heart and throughout the blood vessels in the cardiovascular system

Special properties: multinucleated but not as many as skeletal (up to 5)

smooth muscle, structure, function and special properties

Structure: cells in sheets that run along the longitudinal axis or in a circular layer

• muscle fibers (muscle cells):

• nucleus more circular

• striations less extreme?

• cells are tapered around each end to look fusiform

function: Contraction causes involuntary movements in hollow organs, blood vessels and airways to become narrower in diameter, which in turn produces the movement of blood, fluids, and foodstuffs throughout the cardiovascular and digestive systems; component of the digestive, urinary, and reproductive systems as well as the airways and arteries

special properties: uninucleated

skeletal muscle location

smooth muscle location

cardiac muscle location

skeletal muscle: attaches to bone

smooth muscle: hollow walls of organs

cardiac muscle: in heart myocardium

Fascia

a continuous, three-dimensional web of fibrous connective tissue—composed primarily of collagen, elastin, and water—that wraps around, supports, and separates every muscle, bone, nerve, blood vessel, and organ in the body

fascicile

bundle of muscle fibers within a muscle that is coved by perimysium

Epimysium

Each muscle is wrapped in a sheath of dense, irregular connective tissue called the epimysium

allows a muscle to contract and move powerfully while maintaining its structural integrity

separates muscle from other tissues and organs in the area, allowing the muscle to move independently.

Continuous with the tendon and periosteum so the muscle can have a strong connection to bone so it will not rip off when it contracts

Perimysium

Inside each skeletal muscle, muscle fibers are organized into individual bundles, each called a fascicle, by a middle layer of dense irregular connective tissue called the perimysium

Endomysium

Inside each fascicle, each muscle cell/fiber is encased in a thin areolar connective tissue layer of collagen and reticular fibers called the endomysium

endomysium contains the extracellular fluid and nutrients to support the muscle fiber. These nutrients are supplied via blood to the muscle tissue.

myofibril

the contractile elements of a single muscle cell

long protein cords that extend entire legnth of cell

Tendon

attaches muscle to bone

dense regular connective tissue

tendons to pull on bones, the collagen in the three tissue layers (the mysia) intertwines with the collagen of a tendon

At the other end of the tendon, it fuses with the periosteum coating the bone.

tension created by contraction of the muscle fibers is then transferred though the mysia, to the tendon, and then to the periosteum to pull on the bone for movement of the skeleton.

Aponeuros

broad tendon-like sheet called an aponeurosis

broad sheet of connective tissue in the lower back that the latissimus dorsi muscles (the “lats”) fuse into is an example of an aponeurosis

where are blood vessles in muscles

around the muscle cells inside the facicles

blood vessels branch off off the epimysuim perimysium and endomysium

Muscle fiber function

Also called muscle cells or myofibers

very long

function: to contract muscle

Sarcolemma function

plasma membrane of muscle fiber

lets things in and out

Sarcoplasm function

Cytoplasm of a muscle cell

Holds organelles, myofibrils, glycogen(carb for energy), and myoglobin(gets O2) and Ca2+

myofibrils function

bundle of myofilaments(thick and thin) within a muscle cells and fill casrcoplasm and are surrouned by sarcoplasmic reticulum and mitochonria

sarcoplasmic reticulum function

2 parts

SR

Net-like membrane structures like the smooth ER that store Ca2+ for contractions

Parts: triad: terminal cisternae and transverse tubule

terminal cisternae

Inside the SR and part of the triad

Dilated end sacs of the SR that cross the muscle fiber

2 of these are in the triad

transverse tubule

t tubules

part of triad (1 in each that is sandwiched between 2 terminal cisternae)

tubular infolding from sarcolemma

in between 2 terminal cisternae

goes all the way through muscle cell and allows for chemical signals to get in and out of cell

mitocondria in muscle cells

Pushed between the myofibrils

Many, because muscles have a high demand for ATP

sarcomere function

segment of myofibril from Z to Z disc

functional contractile unit of muscle fiber

thick myofilaments function

Thick filaments are made of myosin (heads on the right and left in zone of overlap and a bare zone in the middle)

The thick filaments bind to and pull the thin filaments

Connected to M plate and connected to Z plate via elastic titin(which runs through the whole thick filament M line to Z disc)

make up A bonds and H zone

thin myofilaments function

Thin filaments are made of 2 strings of actin(fibrous F actin string and globular G actin beads twisted together with tropomyosin and troponin connected on beads

on I bands and in the overlap zone of A band

lighter and reacts to myosin through a Ca2+-binding site

together thick and thin filaments…

Thin and thick filaments slide past each other, producing more overlap in contracted muscle than in relaxed muscle

Interaction between actin and myosin requires calcium

Make up a myofibril inside of muscle cells

each thick filament is surrounded by _ thin filaments

6

I band vs A band

I just has thin filaments

A has thick filaments and thin filaments in the overlap zone

actin and myosin function (contractile proteins)

Actin globules in thin filaments that have active site for Ca2+

Myosin in thick filaments, with heads all on the same side that come off of 2 different protein strings (dimer) that are spiraled around each other and can bind to actin to contract muscle

tropomyosin and troponin function (regulatory proteins)

Both are connected to actin

Tropomyosin: a white fibrous protein that covers the active site on globular actin

Troponin: regulates the activity of tropomyosin by rolling when detecting Ca2+ so the active site is open so myosin can bind

• Ca2+ binds here

• is also bound to Tropomyosin

how to find … on a myofibril in a sarcomere

A band

I band

H zone

M line

A band: dark, thick filaments and has a darker zone of overlap with the thick and thin

I band: light and made of thin filaments and connected to Z disc on each end of the sarcomere

H zone: middle of A band that is lighter and just thick filaments

M line: middle of A band, where thick filaments are linked to the transverse protein by titin

how dose a muscle shorten?

Individual sarcomeres shorten when thin filiments slide towards M line and pull the Z discs closer to each other, and as the Z discs pull closer they pull on the sarcolemma to achive overall shortening of the cell

steps in the sliding filament mechanism

1) Ca2+ is detected by troponin, so it changes shape and rolls tropomyosin away from the active site then myosin heads hydrolyze ATP —> ADP + Pi and become reoriented into a high-energy conformation, cocked back and energized

2) myosin heads bind to G actin active site, forming temporary cross-bridges

2) myosin cross-bridges rotate toward the center of the sarcomere M line (power stroke) and pull thin filaments with them as the myosin heads move to a lower energy state

4) as myosin heads bind ATP so the cross-bridges detach from actin

then will hydrolyze ATP and renergized and move back to high energy state cocked back

what happens to I H and A band and Z discs when a muscle contracts

I disappear since this move to middle

H disappears since thin are part of whole A band

A is darker, and the zone of overlap is the entire thing

Z discs slide in sarcomere shorter

why dose thin filaments not slip back after crossbridge detatch in sliding filiament theory?

the crossbridges do not all form and detach at the same time they stagger like tug or war using both hands

what causes contractions in muscles

This happens because an electrical impulse from a nerve cells in CNS communicates with the muscle fibers chemically and the chemical signal is converted to an electrical signal that tells myofibrils to shorten

electrical impulse or signal at the __ —> chemical signal between the _ and _ —> electrical impulse or signal at the __

electrical impulse or signal at the _neuron_ —> chemical signal between the _neuron_ and _muscle fiber_ —> electrical impulse or signal at the _muscle_

what is the Neuromuscular junction

NmJ is the point of communication between CNS and muscular system

going from electrical signal to chemical signal to electrical signal

which type of muscle tissues can contract without nervous stiumlation

smooth and cardiac

not skeletal they need the connection to neuron and nurotransmitters for every contraction b/c voluntary

know

motor nerve fibers

synaptic knob

synaptic axon terminal

synapse

ACh neurotransmitter

neuromuscular junction

membrane folding in muscle of NmJ

membrane covering that seals the synaptic cleft

pic from slides

can 1 motor neuron from a synaptic terminal or synapse with multiple muscle cells?

can 1 motor neuron innervate multiple cells?

YES

Neuromuscular junction role in excitation-contraction coupling

a. Neural stimulus arises from a motor neuron

b. Acetylcholine is released from neuron

c. ACh binding to receptors in NmJ and cause Na+(?????) to enter muscle, triggering muscle action potential

d. ACh is broken down in the synaptic cleft, terminating its action

Neuromuscular junction role in excitation-contraction coupling

a. Muscle contraction is stimulated by a signal from a nerve cell

b. An electrical signal, called an action potential, is generated within the muscle cell

c. Action potential produces a change in the calcium concentration in the cytosol

d. Increases in cytosolic calcium produce muscle contraction

e. Excitation-contraction coupling is thus the sequence of events by which an electrical signal leads to sliding of the microfilaments

differnce between ligand gated channels, voltage gated channels, mechanically gated channels, and leak channels

Ligand-gated channels: Channels respond to ligands that bind to them

Voltage-gated channels: Channels respond to electrical changes in the plasma membrane

Mechanically gated channels: Channels respond to a mechanical stimulus

Leak channels: Channels always (or randomly) open, ions “leak” in and out

what dose resting membrane potential look like?

The transmembrane potential of a cell at rest

• inside: K+, -proteins, -phosphates

• outside: Na+, -Cl

The separation of charges across a membrane in an excitable cell at rest: inside is negative and outside is positive

why is inside of cell negative?

Na K ATPase

sends 3 Na+ out and only 2 K+ in

what direction dose Na+ move and when dose this happen

moves down its gradient into the cell

when the inside is negative (normally)

what direction dose K+ move and when dose this happen

Moves down its gradient so out of cell

When inside is too postive/outside is negative (not normal)

Describe excitation-contraction coupling

Excitation-contraction coupling is thus the sequence of events by which an electrical signal leads to sliding of the microfilaments

Action potential role in excitation-contraction coupling

An electrical signal is produced by ion movements across the plasma membrane of excitable tissues (like nervous tissue and muscle tissue)

Na and K channels closed in the resting membrane potential

Na chanels open and ions Na ions enter as depolarization

then Na close and K+ channels open and K ions leave for repolarization, which will be completed when the K channels close

Action potential steps on small level

resting membrane potential

local potential

threshold

depolarization

tip point?? (action potential is tip - resting membrane potential?)

repolarization

hyperpolarization

Action potential steps on large level

• Action potential travels to the synaptic terminal and Ca2+ ion enter the synaptic termial though Voltage gated channels

• ACh is released though exocytosis from synaptic terminal

• ACh diffueses across the synaptic clefts and binds to receptors in NmJ on muscle cell

  • K+ leaves muscle cells though ligans gated channel

  • Na+ enters muscle cell though ligated gated channels

• Influx of Na produces a local depolarization that opens voltage-gated Na+ channels

• Action potential in the muscle cell is created and travles to triad

• Voltage-gated Ca2+ channels open in the SR

  • Ca2+ leaves SR by diffusion

  • Activation of sliding filaments because Ca2+ is available to bind to troponin

At rest

electrical signal

Ca2+ release?

contraction

NO electrical signal

NO Ca2+ release

NO contraction

when excited…

Action potential travels from neuron to muscle cell

Action potential travels along muscle cell

Action potential opens Ca++ channels in SR

Ca++ floods into sarcoplasm

Ca++ binds to troponin, initiating contraction

Acetylcholine role in excitation-contraction coupling

Released from motor neurons through exocytosis and binds to receptors NmJ on muscle cell which causes

• K+ leaves muscle cells though ligans gated channel

• Na+ enters the muscle cell though ligated gated channels

What is meant by the term, “motor unit?”

a single motor neuron (nerve cell) and all of the skeletal muscle fibers it controls

Describe how frequency of stimulation affects muscle tension

latent period

contraction period

relaxation period

Describe how muscle tone is produced

Define and distinguish between isotonic and isometric contractions

iosotonic: muscle changes length

• conecntric shortens

• eccentric lengthens

isometiric muscle stays same length

What is a muscle twitch, and what happens during each phase of a twitch contraction?

Length-tension relationship

The length of the sarcomere AT REST affects the amount of force generated with a muscle contraction

Describe and outline the metabolic reactions by which muscle fibers produce ATP

Muscles generate ATP by 3 mechanisms

Creatine phosphate

anaerobic respiration

aerobic respiration

Distinguish between aerobic and anaerobic respiration

anaerobic respiration: glucose, glycogen, sugars and starches

• muscle glycogen + glucose from blood

• glycolysis makes 2 ATP and 2 Pyruvic acid

• 2 pyruvic acids become 2 lactic acid, which goes into blood

aerobic respiration

-amino acids from protein breakdown + fatty acids liberated from adipose cells + pyruvic acids from glycolysis + O2 from hemoglblisn in blood or from myogliblin in muscle fibers

Criteria for describing SKELETAL muscle fibers

a. Fast and slow muscle fibers (see the table at the end of the notes)

b. How do they produce energy?

Skeletal muscle

Appearance of cells; unique

features

Location in the body

Cell size – large or small?

Connective tissue coverings

Sarcoplasmic reticulum

t-tubules present?

Source of Ca++ - extracellular fluid / SR / both?

Junctions between fibers?

Regulator proteins for contraction? (Name them)

VOLUNTARY or INVOLUNTARY?

Appearance of cells; unique

features

Location in the body

Cell size – large or small?

Connective tissue coverings

Sarcoplasmic reticulum

t-tubules present?

Source of Ca++ - extracellular fluid / SR / both?

Junctions between fibers?

Regulator proteins for contraction? (Name them)

VOLUNTARY or INVOLUNTARY?

smooth muscle

Appearance of cells; unique

features

Location in the body

Cell size – large or small?

Connective tissue coverings

Sarcoplasmic reticulum

t-tubules present?

Source of Ca++ - extracellular fluid / SR / both?

Junctions between fibers?

Regulator proteins for contraction? (Name them)

VOLUNTARY or INVOLUNTARY?

Appearance of cells; unique

features

Location in the body

Cell size – large or small?

Connective tissue coverings

Sarcoplasmic reticulum

t-tubules present?

Source of Ca++ - extracellular fluid / SR / both?

Junctions between fibers?

Regulator proteins for contraction? (Name them)

VOLUNTARY or INVOLUNTARY?

Distinguish among physiologically different muscle fiber types (fast glycolytic or fast-twitch; slow oxidative or slow twitch; intermediate or fast-oxidative glycolytic), and describe how the anatomy of these fiber types contributes to their function

fast glycolytic or fast-twitch

Diameter

Tension produced

Contraction speed

Fatigue resistance

Color

Myoglobin content

Capillary supply

Mitochondria

Glycolytic enzyme concentration

Substrates used to generate ATP

Diameter

Tension produced

Contraction speed

Fatigue resistance

Color

Myoglobin content

Capillary supply

Mitochondria

Glycolytic enzyme concentration

Substrates used to generate ATP

slow oxidative or slow twitch

Diameter

Tension produced

Contraction speed

Fatigue resistance

Color

Myoglobin content

Capillary supply

Mitochondria

Glycolytic enzyme concentration

Substrates used to generate ATP

Diameter

Tension produced

Contraction speed

Fatigue resistance

Color

Myoglobin content

Capillary supply

Mitochondria

Glycolytic enzyme concentration

Substrates used to generate ATP

intermediate or fast-oxidative glycolytic

Diameter

Tension produced

Contraction speed

Fatigue resistance

Color

Myoglobin content

Capillary supply

Mitochondria

Glycolytic enzyme concentration

Substrates used to generate ATP

Diameter

Tension produced

Contraction speed

Fatigue resistance

Color

Myoglobin content

Capillary supply

Mitochondria

Glycolytic enzyme concentration

Substrates used to generate ATP

Describe the functional and structural characteristics of cardiac muscle

intercalated discs are unique!

Describe the functional and structural characteristics of smooth muscle

single nucleus

intermediate filaments

caveolae

important differences in physiology compared to striated muscle