Transcript How Animals Move - Harford Community College

How Animals Move
Chapter 21
Pumping Up Muscles
• Androstenedione
– Intermediate in testosterone and
estrogen synthesis pathways
– Taken as dietary supplement
– Doesn’t help add muscle
– Does have negative side effects
Pumping Up Muscles
• Creatine phosphate
– Short chain of amino acids
– Donates phosphate to ATP when muscles need
quick energy
– Does enhance performance in sports that require
short bursts of energy
– Long-term effects unknown
p.349
3 Types of Skeletons
feed me!
1. Hydrostatic skeleton
2. Exoskeleton
resting
3 Types of Skeletons
3. Endoskeleton (vertebrates)
Generalized mammal
pelvic girdle
pectoral girdle
a Skull bones
CRANIAL BONES
d Pectoral girdle
and upper limb bones
FACIAL BONES
CLAVICLE
b Rib Cage
STERNUM
RIBS
SCAPULA
c Vertebral Column
VERTEBRAE
INTERVERTEBRAL DISKS
HUMERUS
RADIUS
CARPALS
ULNA
PHALANGES
METACARPALS
e Pelvic girdle
and lower limb bones
PELVIC GIRDLE
FEMUR
PATELLA
ligament bridging a
knee joint, side view,
midsection
TIBIA
FIBULA
TARSALS
METATARSALS
PHALANGES
Fig. 21-3, p.351
Functions of Bones
• Interact with muscle to enable
movement
• Support and anchor muscles
• Enclose and protect internal organs
• Store calcium and phosphorus
• Produce blood cells
Long Bone
Structure
• Compact bone
• Spongy bone
• Central cavity
contains yellow
marrow
nutrient canal
central cavity
(contains yellow
marrow)
compact bone tissue
spongy bone
tissue
Compact Bone Structure
• Compact bone consists of many dense,
cylindrical layers surrounding canals
cylindrical layers
blood vessel
spongy bone tissue
compact bone tissue
outer layer of
dense connective
tissue
Bone Marrow
• Yellow marrow
– Fills the cavities of adult long bones
– Is largely fat
• Red marrow
– Occurs in spongy bone of some bones
– Produces blood cells
Bone Mass
• In adults, bone building and bone breakdown
continue constantly
• Osteoblast secretions form bone
• Osteoclasts enzymes degrade bone
• Adding and removing minerals adjusts bone
strength and helps maintain blood calcium
levels
Bone Density
• Exercise can increase bone density
• Osteoporosis: Decrease in bone density
– May occur when the action of osteoclasts
outpaces that of osteoblasts
– May also occur as a result of inability to absorb
calcium
Osteoporosis
Where Bones Meet
• Joints: Areas of contact or near contact
between bones
• Ligaments: Straps of connective tissue at joints
• Arthritis: Joint damage or inflammation
– Osteoarthritis
– Rheumatoid arthritis
Skeletal Muscle
• Bundles of muscle
fibers
• Tendons attach
muscles to bone
• Lever system
• Opposing muscle
groups
biceps
triceps
Fig. 21-7, p.354
Skeletal Muscle Contraction
• A muscle is made up
of bundles of muscle
fibers
• Muscle fiber
contains crossbanded myofibrils
myofibril
Sarcomere
Myofibril is made up of thick and thin
filaments arranged in sarcomeres
sarcomere
sarcomere
Z band
sarcomere
sarcomere
Z band
Z band
Muscle Microfilaments
Thin filaments
Thick filaments
• Two actin strands
twisted together
• Myosin
• Globular proteins
• Motor protein
• Parallel with myofibril
• Tail and double head
Sliding-Filament Model
• Myosin heads
attach to actin
filaments
• Myosin heads tilt
toward sarcomere
center, pulling actin
with them
Sliding-Filament Model
When actin filaments are pulled inward,
toward sarcomere center, sarcomere shortens
Filaments
themselves
do not
shorten
Contraction Requires Calcium
• Skeletal muscles contract in response to
signals from motor neurons
• Signals release calcium from sarcoplasmic
reticulum
• Calcium allows actin and myosin to bridge
Contraction Requires Energy
• Muscle cells require huge amounts of ATP
energy to power contraction
• Cells store only small amounts of ATP
• Three pathways supply ATP to power muscle
contraction
ATP for Contraction
ADP + Pi
pathway 1
relaxation
dephosphorylation
creatine phosphate
contraction
creatine
pathway 2
aerobic
respiration
oxygen
pathway 3
glycolysis
alone
glucose from bloodstream and from
glycogen break down in cells
Motor Unit
• One neuron and all muscle fibers it controls
• When a motor neuron is stimulated, all
fibers in muscle unit contract
simultaneously, producing muscle twitch
• Rapid, repeated stimulus of motor unit
produces tetanus
peak
relaxation
Twitch and
Tetanus
stimulus
contraction starts
time
number of stimuli per second
number of stimuli per second
tetanic
contraction
twitch
repeated stimulation
Muscle Tension
• Mechanical force exerted on an object by a
contracting muscle
• For a muscle to shorten, muscle tension must
exceed the load that opposes it
• Load may be the weight of an object or pull
of gravity on muscle
Two Types of Contraction
Muscle
shortens as
it contracts
Isotonic contraction:
Load is less than muscle’s
peak capacity
Muscle contracts
but can’t shorten
Isometric contraction: Load is
greater than muscle’s peak
capacity
Infection and Motor Neurons
• Bacterial toxins block motor neuron control
– Clostridium botulinum, botulism
– Clostridium tetani, tetanus
Muscle Fatigue
• Inability to maintain muscle tension
• Glycogen is depleted after a period
of tetanic contraction
• Requires recovery time
Muscular Dystrophies
• Genetic disorders in which muscles weaken
and degenerate
• Duchenne muscular dystrophy
– Defective protein in muscle plasma membrane
prevents normal binding of actin filaments to Z
band
• Myotonic muscular dystrophy
Exercise
• Aerobic
– Long duration, low intensity
– Increases number of mitochondria, number of
blood capillaries to all skeletal muscle
• Strength training
– Intense, short duration
– Makes fast-acting muscles form more myofibrils
and enzymes for glycolysis
Aging
•
•
•
•
Muscles shrink
Number of muscle fibers decreases
Slower healing time
Aerobic exercise improves fitness and memory
Osteogenesis Imperfecta