Transcript The Muscular System

The Muscular System
J. Hinson
Human Anatomy and Physiology
JCHS
I. Introduction
The human body has over 400
skeletal muscles, which accounts for
~ 50% of the body weight!
Muscles are generally named for
their location, size, direction of
fibers, or number of attachments.
The gluteus maximus is the largest
muscle in the body.
The strongest muscle in the body is
the masseter.
II. Some Key Terms
origin: muscle attachment on
immovable bone; usually proximal
insertion: muscle attachment on
movable bone; usually distal
prime mover: major contractile
muscle producing movement
synergist: muscle assisting PM
antagonist: muscle stretched when
PM contracts
Major Muscle
Groups
III. Functions - Characteristics
A. Contractility: ability to shorten**
B. Excitability: (responsiveness or
irritability) ability to receive and
respond to stimuli
C. Extensibility: ability to be stretched
or extended
D. Elasticity: ability to recoil after
stretch
III. Functions - General
A. PROVIDES FOR
MOVEMENT via
contraction of
fibers
B. Maintaining
posture
C. Stabilizing joints
D. Generating heat
E. Protect internal
organs
IV. Types
A. Voluntary
(skeletal)
1. Attached to bone
2. Controlled by the
individual
3. Responsible for
body movements
http://www.medical-look.com/systems_images/Muscular_System.jpg
IV. Types
A. Voluntary
(skeletal)
4. Wrapped in layers
of connective
tissue called fascia
5. Fascia merges to
form a tendon
(connects two!)
http://www.ditchfieldpt.com/assets/fascia_1244463_white.jpg
http://www.eorthopod.com/images/ContentImages/foot/foot_achilles/foot_achilles_tendon_anatomy01a.jpg
IV. Types
B. Smooth
(involuntary)
1. Found in walls of
digestive and
urinary system
2. Found in blood
vessels and
bronchi
http://webanatomy.net/histology/muscle/smooth_muscle_arrangement.jpg
IV. Types
3) Cardiac
(Involuntary)
1. Found only in the
heart
2. Can go without
blood for only a
short time
http://webanatomy.net/
histology/cardiac/cardia
c_muscle.jpg
http://eduspace.fr
ee.fr/vs_pages/bi
onic_heart_fichier
s/real_heart.jpg
V. Structures
A. Epimysium: “overcoat” of dense
irregular connective tissue
surrounding entire muscle
B. Perimysium: fibrous connective tissue
surrounding each fascicle
C. Endomysium: reticular connective
tissue surrounding each individual
muscle fiber
V. Structures
D. Muscle: organ
E. Fascicle: bundle of muscle cells
F. Muscle fiber: striated cell; covered by
sarcolemma (membrane)
G. Myofibril: rod-like contractile unit of muscle
fiber
H. Sarcomere: contractile unit of a myofibril
I. Tendon/Aponeurosis: connective tissue
wrapping extending from muscle
SLIDING FILAMENT
THEORY
J. Hinson
Human Anatomy and Physiology
JCHS
I. The Neuromuscular Junction
A. Connection b/w nerve and
muscle fiber
B. In response to a motor nerve
impulse, the end of a motor
nerve secretes a
neurotransmitter,
Acetylcholine (ACh), which
stimulates a muscle fiber.
1.
http://academic.wsc.edu/faculty/jatodd1/351/motor_unit.jpg
http://camilolab.slu.edu/444/graphics/Leeson6-12.jpg
I. The Neuromuscular Junction
C. Threshold stimulus – minimal
stimulus needed to cause a
muscular
contraction
1.“all or none”
response
http://www.bbraunusa.com/stimuplex/graphics/hi_speed_nerve.jpg
II. Skeletal Muscle Contraction
A. Muscle fiber contraction results
from actin sliding over myosin.
1. The SARCOMERE is the structural
and
functional
unit of
the
muscle.
http://www.3dotstudio.com/zz.html
http://www.ucl.ac.uk/~sjjgsca/MuscleSarcomere.gif
Myosin
Actin
http://www.peprotech.com/uploadedimages/Sarcomere2.jpg
http://gilead.org.il/hcm/sarcomere.jpg
II. Skeletal Muscle Contraction
Contraction
Animation:
B. Contraction Stimulus
http://highered.mcg
raw1. Acetylcholine stimulates. hill.com/sites/00724
95855/student_view
2. Nerve impulse travels over 0/chapter10/animati
on__action_potentia
ls_and_muscle_cont
the mm. fiber surface and raction.html
via transverse tubules into fiber.
3. Sarcoplasmic reticulum releases
2+
Ca .
4. Cross-bridge forms b/w filaments,
and actin moves inward causing
the muscle to shorten.
http://www.ivyrose.co.uk/Topics/Mu
scles/SlidingFilament_Theory.jpg
II. Skeletal Muscle Contraction
B. Contraction Stimulus
2+
5. Fiber relaxes w/ uptake of Ca .
6. Cholinesterase decomposes ACh.
7. Actin-myosin cross-bridge breaks.
8. Muscle fiber relaxes.
Myofilament Contraction:
http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter10/animation__myofila
ment_contraction.html
Sarcomere Contraction Animation:
http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter10/a
nimation__sarcomere_contraction.html
http://www.octc.kctcs.edu/GCaplan/anat/Notes/API%20Notes%20J%20%20Muscle%20Contraction.htm
II. Skeletal Muscle
Contraction
C. ATP supplies the energy for mm.
fiber contraction, and creatine
phosphate stores energy that can be
used to synthesize ATP.
** Contraction will sustain as long as
enough ATP and Ca2+ is available!
II. Skeletal Muscle Contraction
D. Other responses
1. Twitch: short, single contraction
2. Sustained contraction: rapid
succession of twitches (fluid
movement).
3. Tetany: forceful, sustained
contraction
4. Muscle tone: minimal sustained
contraction (Posture!)
5. Myogram: recording of muscle
contraction
http://media.wiley.com/Lux/05/21805.nfg002.jpg
III. Muscular Response to
Exercise
A. Myoglobin: mm. cell protein
that stores Oxygen
B. Oxygen supply is sufficient at
rest or during moderate
exercise to support aerobic
respiration.
1. Energy released is lost as heat.
III. Muscular Response to
Exercise
C. During vigorous exercise, an O2
deficiency may develop, and lactic
acid may be produced, thus DOMS
(delayed onset muscle soreness).
1. Lactic acid accumulation
responsible for fatigue.
D. Oxygen Debt – O2 needed to
convert LA to glucose and restore
ATP and CP
http://img.sparknotes.com/figures/1/18b9012870c85fba3a8046a767b52ddf/anaerobicaerobic.gif