Muscle Physiology:
The Actions of the Sarcomere.
Cardiac
Muscle
Characteristics
 Intercalated disks
 Striated
 Involuntary
 Located in heart
Skeletal Muscle
Characteristics
 Many nuclei per
cell
 Striated
 Voluntary
 Located along
bones
Smooth Muscle
Nonstriated
Involuntary
Located in
digestive tract
Functions of Muscles
Movement: results from muscle contraction,
enables you to respond quickly
Maintains Posture and Joint Stability:
allows you to sit upright; stabilize joints of the body
Support Soft Tissue:
underlying digestive organs.
abdominal muscles protect
Guard Entrances and Exits
Generate Heat: heat is generated as they
work…FRICTION


Maintains body temperature
Skeletal muscles create the most heat
Characteristics of Muscle Tissue
Excitability:
ability to receive and respond to
stimuli…
Contractibility:
ability to shorten quickly and
with force…
Extensibility: ability to be stretched or extended
beyond their resting state…
Elasticity:
ability of a muscle fiber to recoil and
resume its resting length
Organization of Muscle
Muscles are
composed of groups
of fibers called
fasicles.
Fibers are the muscle
cells inside all muscle.
Tendons are bands of
collagen fiber that
attach muscle to
bone.
Sarcomere: the contracting
unit
Skeletal Muscle Striations
Z line
I band
H band
A band
Organization
from the
muscle fiber
to the
sarcomere.
Cross sectional view of Sarcomere.
Differences are
detected in the
sizes of the
myofilaments
Myosin is the
thicker fiber.
Actin is the
thinner fiber.
Striations are seen because of sarcomere
bands.
.
Muscle fiber structure
Muscle cell
Sarcolemma
Sarcoplasm
Sarcoplasmic
reticulum
T tubule
mitochondria
Structure of Muscle Tissue
Sliding Filament Theory
Sliding Filament Theory
Actin slides over myosin shortening the
sacromere between the Z lines
Chain of Events during
Muscle Contraction!
1. Cross Bridge
Attachment
2. Power Stroke
3. Cross Bridge
Detachment
4. Cocking (Recoil)
of Myosin Head
What happens at the sarcomere?
Players for the power stroke
Cross bridge
attachment
Power strokes
Cross bridge
detachment
“Cocking” of the
myosin head
Power stroke
Motor Unit: A motor neuron and all the
muscle fibers it stimulates.
Diagram of a Muscle Twitch
Increase in muscle tension
due to continued stimulation.
Muscle that reaches peak tension during rapid
cycles of contraction and relaxation.
Complete tetanus = relaxation
state is eliminated.
Label the
following!
Aerobic Muscle Metabolism
Glycolysis
Aerobic
Respiration


Krebs Cycle
ETC
Anaerobic Muscle Metabolism
Oxygen Debt
Lactic Acid
Fermentation
Muscle Fatigue
Creatine Phosphate
Red (slow) twitch fibers
Aerobic
Slow-acting ATPases (enzymes that break
down ATP)
Large amounts of myoglobin
Red color to cell
Abundant supply of mitochondria
Fatigue resistant-as long as O2 is available
High endurance (jogging, swimming, soccer)
White (fast) twitch fibers
Large pale cells with twice the diameter of
red fibers
Very little myoglobin
Contain fast-acting ATPases and contract
rapidly
Contain few mitochondria, but large glycogen
stores
Depend on anaerobic resp. to make ATP,
therefore fatigues easily
Low endurance, much power….sprints
Pink (intermediate) twitch
fibers
Mixture of red and white fibers
Aerobic mechanisms and fatigue
resistant
Contain fast-acting ATPases
High myoglobin content