Muscular System

Read Ch 6 Review Questions begin on page 198

S/A #2, 7, 10, 12, 18, 20, 21At the Clinic #2, 5, 6

Overview

Over ½ of body’s mass is muscle—90% of that is skeletal muscle

These contractile cells have high energy needs, so it’s common to see an ample blood supply associated with muscles

http://www.edukshun.info/wp-content/uploads/2008/04/big-muscles.jpg

Overview con’t: Blood provides glucose and oxygen while removing

metabolic waste products Muscles (and nervous tissue) consume almost 70%

of the food energy taken into your body daily Muscle is as intensive a consumer of calcium as is

the skeletal system—much of the Ca stored in bones is made available for the muscles’ needs.

Categorizing muscles

Microscopically

Nonstriated (no lines)

Striated (lines running through)

micro.magnet.fsu.edu/

htt

p:/

/ph

ela

fel.

tech

nio

n.a

c.i

l/~

tam

arh

/web

sit

e/i

mag

es/d

iffere

nt-

kin

ds-o

f-m

uscle

s-

2.j

pg

Categorizing muscles

ControllabilityInvoluntary (no control)Voluntary (control)

Categorizing muscles

Location Cardiac: Involuntary, only found in

heart Smooth: Involuntary, lines digestive

organs Skeletal: voluntary muscles found

attached to bones

Functions of the Muscular System

Movement of body parts—by pulling on bones. Bones act as levers, joints as the fulcrum.

Guard entrances and exits

Posture Stabilizing joints Create heat

Physiology of muscleContraction is achieved by

the simultaneous shortening of all the sarcomeres within a cell.

Three stages: Neural stimulationContractionRelaxation.

Neural StimulationTakes place at

the neuromuscular junction.

The nerve cell releases a neurotransmitter

neurotransmitter—a chemical used for cell to cell communication.

http://www.freewebs.com/soaring_sphincter_travel_agency/nerve%20impulse2.bmp

Neural Stimulation Muscles respond to

the neurotransmitter acetylcholine (Ach).

Ach binds to receptors on the sarcolemma.

The binding of Ach affects the transport of ions across the sarcolemmawww.cells.de/.../Neuromuscular-

junction.jpg

Neural Stimulation In a resting muscle, the concentration of

sodium ions is normally higher in the fluid outside the muscle cell while the concentration of potassium ions is higher inside the cell.

Sodium/potassium pumps maintain these unequal ion concentrations.

upload.wikimedia.org/wikipedia/commons/thumb/...

Neural Stimulation This imbalance produces an unstable

condition. When stimulated by Ach the membrane loses its ability to maintain the imbalance.

Once the membrane is stimulated, it opens the ion channels permitting the free flow of sodium into the muscle cell and potassium out of the cell.

In turn, calcium stored in the sarcoplasmic reticulum is released to begin the contraction phase

Muscle Contraction When calcium

(released by the sarcoplasmic reticulum) binds to the troponin, contraction begins.

Troponin sits on tropomyosin on the same region where actin binds to myosin.

www.cvphysiology.com

Muscle Contraction Ca bumps troponin off the binding

site, permitting myosin to attach to actin.

Troponin also transmits info that activates ATP synthesis around the myosin. The ATP provides energy for the myosin head to swivel and pull the myosin toward the actin.

Myosin crossbridges at work…

http://www.patrickcarlberg.dk/images/thinfilament.jpg

Muscle Relaxation Relaxation occurs when there are no

more neural stimulations exciting the sarcolemma. The sodium and potassium ion levels are completely recovered

The sarcoplasmic reticulum has retrieved most of the Ca, causing the release of the myosin heads from the actin.

There is no mechanism for the muscle cell to lengthen (so we’ll discuss how that happens later in the lecture).

SquintingStimulus

Receptor

Regulator

Sensory Nerves

Motor Nerves

Effectors

Light reduced

Video links

http://www.hippocampus.org/Biology

search for Biology for AP/Skeletal Muscle contraction

Crash course—Muscles http://www.youtube.com/watch?v=jqy0i1KXUO4

Bozeman Science—Muscles http://www.youtube.com/watch?v=mejCXr7p37U&list=PLCC2DB523BA8BCB53&index=17

Neural Stimulation Videos

https://www.youtube.com/watch?v=0mhAN4-8uWo

https://www.youtube.com/watch?v=uJTdx1GbEqU&noredirect=1

http://www.youtube.com/watch?v=hzXVe4RS8-A

Muscular Contraction videos

http://www.youtube.com/watch?v=BMT4PtXRCVA

https://www.youtube.com/watch?v=zopoN2i7ALQ

https://www.youtube.com/watch?v=f0mDFP7qn1Y

Animations

http://www.wisc-online.com/objects/ViewObject.aspx?ID=AP2904

http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter42/animations.html#

Contraction in Action

Planning your skit…

http://3dotstudio.com/contract.gif

http://media-2.web.britannica.com/eb-media/36/2836-004-C63246A5.gif

Contraction in Action--Skit

Links to put on website http://www.youtube.com/watch?v=

EdHzKYDxrKc http://www.youtube.com/watch?

v=mWPmUqRZYls http://www.youtube.com/watch?v=e3Nq-

P1ww5E

Muscle cell structure

Animation of entire process…

Video of sarcomere shortening

Other factors found in muscle fibers ensuring adequate muscle contractions: Creatine Phosphate: stores energy in

muscle cells. It collects this energy from ATP and is capable of storing it for long periods of time.

Glycogen (stored form of glucose) can supply glucose when muscles cells need it to produce ATP

Myoglobin is a chemical that stores oxygen for certain muscle cells. This O2 permits muscle cells to provide large amounts of ATP during continuous or heavy work.

Skeletal Muscle Action Muscle cells either contract or don’t…so

we get graded effects based on contraction of more individual fibers at the same time.

Strength is achieved by stimulating more individual fibers to fire

Endurance is achieved by producing contraction and relaxation groups working together.

Body Movements Flexor—decreases

the angle of the joint by bringing the bones closer together

Extensor—extends a joint by increasing the angle between the bones

Body MovementsRotator—

movement around an axis (partway around)

Tensor—important posture/positioning muscles that make a body part more rigid or tense.

Body MovementsAbduction—

moving away from the midline

Adduction—moving toward the midline

Body Movements Depressor—

produce a downward movement

Levatator—provide an upward movement

Sphincter—decreases the size of an opening

www.cescg.org

ww

w.m

da.o

rg

Special MovementsPronator—

motion of palm downward

Supinator—palm moves upward

Special Movements

Inversion—turning the sole of your foot medially

Eversion—turning the sole of your foot laterally

Special MovementsDorsiflexion—

pointing your toes up toward your shin

Plantar Flexion—pointing your toes downward

Muscular System

Pathologies

Rigor Mortis Calcium leakage out of the sarcoplasmic

reticulum into the sarcomere. Common after death. Eventually, the muscle cells structures start to decay, causing the muscles to become soft and loose.

Strain Most common

muscle ailment An injury due to

overworking the muscle’s force on the joints.

Injury to the tendon or muscle tissue

http://www.nlm.nih.govhttp://www.fairview.org

Sprain A sprain is an injury

to a ligament. (A ligament is a thick, tough, fibrous tissue that connects bones together.)

Ligaments prevent abnormal movements. When too much force is applied to a ligament they can be stretched or torn. www.eorthopod.com

Contusion Bruising of

the muscle

www.bruisepatch.com

Muscle Spasms Involuntary,

abnormal contractions of a muscle or muscle group

Caused by a wide range of medical conditions

www.cure-back-pain.org

Muscle Cramp Painful contraction of

a muscle Extreme muscle

exertion is the most common cause of cramps, although certain poisons and bacterial infections can also cause muscle cramping

www.answers.com

Paralysis

Complete failure of a muscle function Rigid paralysis—excessive muscle

stiffness Flaccid paralysis—complete lack of

muscle contraction Many causes…including spinal injury

and poisoning Eg: Tetanus--Caused by soil bacteria

that produces poisons that cause rigid paralysis

Dermatomyositis

Inflammation of the muscle and overlying skin.

Cause: unknown, but it can be treated with drugs (to reduce inflammation) and sun avoidance www.nytimes.com

Muscular dystrophies Group of conditions

that involve progressive weakness in the voluntary muscles.

Usually due to the inability of the nervous system to stimulate muscle action

Eventually results in muscle atrophy and wasting.

esciencenews.com

Tetany Calcium imbalance disease that causes extended periods of spasms in the arm and leg muscles.

Do NOT confuse this with the bacterial disease tetanus!

Cachexia Type of muscle loss associated with

diseases such as AIDS and cancer.

Also found in starvation and a common consequence of anorexia and bulimia

ww

w.a

ids-

images.

ch

Cachexia A slower form is a normal consequence

of aging b/c the body reduces its ability to rebuild muscle structure as you age. Brought about by sedentary lifestyles—

resulting from other age related illnesses Neural stimulation also is lessened as

you age; important for muscle upkeep

Nutritional issues with muscle loss

Protein turnover: muscles need lots of protein to maintain their integrity Malnutrition and undernutrition as we age

greatly affects protein turnover. Can be caused by poor diets or income levels Lack of appetite as we age is another

contributing factor As we age, our digestive system can’t absorb

some of the impt amino acids needed for muscle cell growth/maintenance.

Muscle atrophy—other causes

Decline in sex hormones and other chemical messages needed for muscle cell growth, maintenance and repair. Insulin-like growth factor-1: known

to lessen with maturity Cytokines cause muscle atrophy

and are known to increase with age