Lecture 8&9 Anatomy

Skeletal Muscke and Muscle Organization

what do skeletal muscles have

fibers : elongated cells that contract via longitudinal axis

why is the muscular system imporotant (2)

• physiological processes

• interactions w enviornment

what are the three types of muscle tissues and their functions

1. skeletal: pulls on skeletal bones and is voluntary

2. cardiac: pushes blood via artery/veins, involuntary, rhyhmic contractions

3. smooth muscle: pushes fluids/solids along digestive tract, involuntary

what are the 4 basic properties of muscle tissues and describe them

excitability: ability to respond to stimuli

contractibility: shortern/exert a pull or tesnion

extensibility: ability to continue to contract over a range of resting lengths

elasticity: ability to rebound toward orginal length

what are the 5 functions of skeletal muscles

1. skeletal movement (pull tendons to move bone)

2. posture/body position (stablize joints for posture)

3. support soft tissue (support weigth of visceral organs)

4. regulate entering/exiting material such as swalloing, urination

5. maintain body temp, energy used for contraction can be converted to heat

what is gross anatomy

study of organization of muscles, connective tissues, nerves w muscles and blood vessels w muslces

what is epimysium

a dense connective tissue that surrounds the entire muscle

what is permysium

dense conneective tissue that divdies the muscle into parralel compartments

parralel compartements that are broken up within the perimysium are called

fascilcles

what is the endomysium

dense connective tissue that surrounds individual muscle fibers

what do myosatellite cells do

repair damaged muscle tissue

what three things form a tendon

epimysium, perimysium, and endomysium

what do tendons do

connect muscle to a bone

what are aponeuroses

thick/flat sheets that connect muscle to muscle (type of connective tissue)

what type of communication occurs between a nerve and muscle, and where is it released

chemical

• chemical is released into neuromusclualr synapse known as NMJ

do blood vessels branch to form coiled networks to accomodate flexion/extension of muscles

yes

label down

A: neuromuscular junction

B: skeletal muscle fiber

C: axon

😩 nerve

what is fibromyalgia

seen mostly with women or men

muscoskeletal pain accompanied by fatigue, memroy loss, sleep and mood changes.

• can also have anxiety, depression, tension headaches

seen mostly w women

what is the name of the membrane that surrounds the muscle celll in skeletal muscle fibers

sacrolemma

what is the name of the cytosol of the muscle cell within the skeeltal msucle fibers

sarcoplasm

describe 3 things of the skeletal muscle fiber or muscle cell

• multinucleated

• nuclei are within the sarclemma

• 30-40cm

what is the name of the embryonic cells that form skeletal muscle fibers

myoblasts

do myoblasts form skeletal muscle fibers

no

what are myosatellite cells

cells that differentiate4 to assist in repair and regernation of skeletal muscle fibers

what is the name of the tubulues that conduct electrical impulses for muscle fiber contraction

transverse tubules aka T tubules

Chemical communication between a neuron and a skeletal muscle fiber occurs at a site called the

NMJ

The sarcolemma and these T tubules conduct electrical impulses, called _____ ——————, to stimulate muscle fiber contraction.

action potentials

what do myofibrils do

they are attatched to what at each end of the muscle cell

The active shortening of myofibrils is responsible for skeletal muscle fiber contraction.

attatched to the sarcolemma

what makes up myofibirls?

myofilaments including actin (thick protein filaments) and myosin (thin protein filaments)

what surrounds each myofibril? what is its function?

SR aka the sarcoplasmic reticulum

The SR is the storage and release site of calcium ions and has an essential role in controlling individual myofibril contraction

what is the sacromere

main unit of muscle fibers, many in each myofibril, has overlapping actin/myosin, and gives skeletal muslce an identifcicable characteristics

describe the sacromere organization (3) simple

myosin: thick filament

actin: thin filament

all myofilaments are arranged parallel to the long axis of the cell

Myofibrils are organized in repeating units called

• they are the smallest contractile units of muscle fibers. come in different size, density, and distribution

sacromeres

what are the 5 lines/bands you should know of the sacromere

1. z line

2. L band (light)

3. A band (dark)

4. H band

5. M line

what is the z line or z disc of the sacromere

bisect the I bands and mark the boundary between adjacent sarcomeres. Z lines are made up of proteins called actinin, which interconnect thin filaments of adjacent sarcomeres.

within the z line, what connects myosin to the z bands

titin

what is the I band (light)

isotropic band, only actin

• light when viewed using polarized light microscopy

what is the a band (dark)

anisotropic band that consists of actin and myosin

what is the zone of overlap with sacromere organization

when there is an overlapping chain of actin and myosin in the A band that creates striations

what does the H band consist of

only myosin

where is the m line found

middle of A band

what does the m line do

M line connect the central portion of each filament to the neighboring thick filaments. M lines stabilize the positions of the thick filaments.

Label

A: a band

B: l band

C: z line

😩 M line

E: H band

F: Titin

G: Z line

H: thin filaments

I: thick filaments

what are thin filaments made up of in sacromere organization

actin

what are the 4 things part of thin filaments

1. f actin

2. g actin

3. tropomyosin

4. troponin

what molecules have an active site or bidning site

g actin of thin filaments

what holds the f actin strands together

nebulin

what is tropomyosin

a protein that covers the active sites when the muscle is relaxed within thin filaments

what is tropnin

holds tropomyosin in position

what makes up thick filaments

and what do they contain of

myosin makes up thick filaments

myosin filaments consist of an elongated tail and a gobular head aka cross bridges

what is a tension

contracting muscle shortens in length by exerting a pull

when a muscle contract what happens

4

1. interactions of thick/thin filaments

2. calcium ions, presence of ATP

3. actin filaments slide toward each other

what is the sliding filament theory

actin filaments slide toward each other

• H and I get smaller

• zone overlap gets larger

• z lines get closer togehter

• A band remains the same

what is the dark region where thin filaments are found between the thick filaments

zone of overlap

what was the region of the sarcomere that contains thin filaments but no thick filaments

I band

explain the difference between these two images

left side is the resting sacromere

right side is the contracted sacromere

explain what occurs in a contracted sacromere

after cycles of bind pivot detach and reactivate, the muscle completes a contraction.

During contraction, sacromere in the A band stays the same width, Z lines move closer tg, and H / I bands get smaller

in muscle contraction what is the axon terminal

axon terminal is the tip of the axon at the neuromuscular junction

what is the synaptic vesicles

contain neurotrasmitter Ach

what happens when Ach is released

it gets released from the end of the axon into the synpatic cleft

what does the enzyme AChE do

an enzyme in the synaptic cleft that breaks down acetyhcoline

what are the 6 steps of muscle contraction

1. contraction cycle begins

2. active site exposure'

3. cross bridge formation

4. myosin head pivoting

5. cross birdge detachment

6. myosin reactivation

what happens during the first step of contraction cycle

a nerve impulse causes the release of the neurotransmitter ACh which comes in contact with the sacroplasmic reticulum (SR) the SR then releases its stored calcium ions and these ions then enter the zone of overlap

• causes changes in membrane potential

what happens during the second step of muscle contraction aka the active site exposure

calcium ions bind to troponin

• The bound calcium ions cause the tropomyosin molecule to roll so that it exposes the active sites on actin

what happens during the third step of muscle contraction aka cross bridge formation

once the active sites are exposed, the myosin heads extend and bind to the exposed active sites on actin. this forms cross bridgees

what happens during the fourht step of muscle contraction

myosin pivots towards the m line

what happens during the fifth step of muscle contraction

cross bridge deatachment

ATP binds to myosin heads and breaks the cross bridges between myosin and actin. cross bridges are exposed again

what happens during the sixth step of muscle contraction

cross bridge binding, cross bridge pivoting, cross bridge deatahcmnet repeats, and the hydorlysis atp is requrired

acetylcholine is broken down by what , what happens then

acetylchloinesterase, which causes the action potential to stop

what happens towards the end of muscle contraction that leads to muscle relaxes (5)

1. SR reabsobrs calcium ions

2. toponin/tropmyosin complex goes back to normal position

3. active sites are locked

4. cross bridges can no longer bind to active sites

5. muscle relaxes

in a muscle fiber, the amount of tension generated during a contraction depends on what

depends on the number of cross bridges interactions occuring in the sacromeres of the myrofibrils. then the number of cross bridghes depends on the overlap between thick and thin filaments.

label the first 5 in this image and muscle contraction

1. AcH is released, binds to receptors

2. action potential reaches T tubule

3. SR releases calcium

4. active site is epxosed cross bridge is formed

5. contraction begins

label the last 5 steps

1. ach is removed by AChE

2. SR recaptures calcium ions

3. active sites covered, no more cross bridge interactuib

4. contraction ends

5. relaxation occurs

what is precise control , what is an example of it

a motor unit controlling 2 or 3 muscle fibers

example: control over the eye muscles

what is an example of less precisde control

control over leg muscles

• motor unit controlling perhaps 2000 muscle fibers

what two things do muscle tension depend on

1. frequency stimulation

2. number of motor units involved

what is the all or none principle

complete contraction or none

what is recruitment

the amount of force of contraction depends on the number of motor units activated

what is muscle tone

tension of a muscle when it is relaxed

what are muscle spindles

specialzied muscle cells that are monitored by sensory nereves to control muscle tone

what is muscle hypertrophy

enlargement of the muscle

how does exercise help motor units

increases mitochondria, activiity of muscle spindles, concentration of glycolytic enymes and glycogen reserves

what is muscle atrophy

discontinued use of a muscle

• cuases a decrease in muscle mass, muscle tone, flaccid, and muscle fibers become weaker

what are the three types of muscle fibers

1. fast fibers (white fibers)

2. slow fibers (red fibers)

3. intermediate fibers (pink fibers)

what type of fiber is associated with eye muscles such as contractions, fast slow or intermediate

fast

what type of muscle fiber contains myoglobin, and is associated with slow leg muscles

slow fibers or red fibers

what type of fibers contract faster then slow fibers but slower then fast fibers

intermediate fibers also known as pink fibers

what is the above and bootm image what type of fibers

toop is slow fibers

bottom is fast fibers

what are 6 characteristics of fast fibers

• large

• densely packed myofibrils

• large glycogen reserve, few mitochondria

• large amounts of ATP

• fatigue rapidly

with fast fibers of skeletal muscle, do they contract using aerobic or anaerobic metablisjm

anaerobic, specifically glycolysis

what are the features of slow fibers, and do they contract via aerobic or anaerobic metablism

(7)

• small

• take 3x as long to contract

• can contract for longer periods of time

• contain a lot of myoglobin

• fatugie slowly

• aerobic metabolism

• MORE mitochronia then fast

who has fast fibers

sprinters, hand/eye muscles, intense workouts increase this

who has slow fibers

back and leg muscles

marathon runners

trianing for long distacne running

what are some shapes or arrangments of fibers

1. parallel muslce

2. conbergent

3. pennate

4. unipennate

5. bipennate

6. multipennate

7. circular

what are parallel muscles and examples

1. when muscle fascicles are parallel to longitudinal axis

examples: biceps brachii and rectus abdominis

what are converegent muscles

muscle fibers from a broad area but come together at a common point such as the tendon or raphe

what is an example of a convergent muscle

pectoralis major

what type of muscle is this

parallel

what type of muscle is this

convergent

what is a pennate muscle and the difference between uni, bi and multi

pennate muscle is a muscle fiber from an oblique angle to the tendon of the muscle

uni: all muscle fibers on same side of tendon

bi: muscle fibers are on both sides of tendon

multi: tendon branches within the muscle (such as the deltoid muscle)