1. Vertebrate Muscle Anatomy
Muscles: convert the chemical
energy of ATP into mechanical work.

2. Three different kinds of muscles are found in vertebrate animals
Skeletal
Cardiac
Smooth
involuntary, striated auto-rhythmic
voluntary, striated
heart
moves bone
multi-nuleated
involuntary, non-striated
digestive system arteries, veins
evolved first

3. Anatomy of Skeletal Muscle
Muscle attaches at the origin
At its other end, the insertion, the muscle tapers into a glistening white tendon
As the muscle contracts, the insertion is pulled toward the origin and the arm is straightened or extended at the elbow. Thus the triceps is an extensor.
skeletal muscle exerts force only when it contracts, a second muscle — a flexor — is needed to flex or bend the joint.
antagonistic pair of muscles work across other joints, provide for almost all the movement of the skeleton.

4. Muscles movement Muscles do work by contracting
skeletal muscles come in antagonistic pairs
flexor vs. extensor
contracting = shortening
move skeletal parts
tendons
connect bone to muscle
ligaments
connect bone to bone

5. Skeletal Muscle: The striated appearance of the muscle fiber is created by a pattern of alternating dark A bands and light I bands.

6. Closer look at muscle cell
Sarcoplasmic reticulum
Transverse tubules (T-tubules)
Mitochondrion
multi-nucleated

7. Sarcoplasmic reticulum (SR)
Fig a
Synaptic terminal
Motor neuron axon
T tubule
Mitochondrion
Sarcoplasmic reticulum (SR)
Myofibril
Plasma membrane of muscle fiber
Ca2+ released from SR
Sarcomere

8. Muscle cell organelles
Sarcoplasm
muscle cell cytoplasm
contains many mitochondria
Sarcoplasmic reticulum (SR)
organelle similar to ER
network of tubes
stores Ca2+
Ca2+ released from SR through channels
Ca2+ restored to SR by Ca2+ pumps
pump Ca2+ from cytosol
pumps use ATP
ATP

9. Structure of striated skeletal muscle
Muscle Fiber
muscle cell
divided into sections = sarcomeres
Sarcomere
functional unit of muscle contraction
alternating bands of thin (actin) & thick (myosin) protein filaments

10. Muscle filaments & Sarcomere
Interacting proteins
thin filaments
braided strands
actin
tropomyosin
troponin
thick filaments
myosin

11. Thin filaments: actin Complex of proteins
braid of actin molecules & tropomyosin fibers
tropomyosin fibers secured with troponin molecules

12. Thick filaments: myosin
Single protein
myosin molecule
long protein with globular head
bundle of myosin proteins:
globular heads aligned

13. Thick & thin filaments
Myosin tails aligned together & heads pointed away from center of sarcomere

14. Thick filaments (myosin)
Fig b
TEM
0.5 µm
M line
Thick filaments (myosin)
Thin filaments (actin)
Z line
Z line
Sarcomere

15. Cardiac Muscle
Cardiac or heart muscle resembles skeletal muscle in some ways: it is striated and each cell contains sarcomeres with sliding filaments of actin and myosin.
Throughout our life, it contracts some 70 times per minute pumping about 5 liters of blood each minute.

16. Cardiac Muscle: Structure = Function
Striated
Different electrical and membrane properties form skeletal
Cardiac cells have ion channels in their plasma membranes that cause rhythmic depolarization = triggering action potentials with no input form NS

17. Unique traits of cardiac muscle relate to function of pumping blood
myofibrils of each cell are branched.
The branches interlock with those of adjacent fibers by adherens junctions. These strong junctions enable the heart to contract forcefully without ripping the fibers apart.

18. Smooth muscle is found in the walls of all the hollow organs of the body (except the heart). Its contraction reduces the size of these structures.
regulates the flow of blood in the arteries
moves your breakfast along through your gastrointestinal tract
expels urine from your urinary bladder
sends babies out into the world from the uterus
regulates the flow of air through the lungs
The contraction of smooth muscle is generally not under voluntary control.

19. Longitudinal muscle relaxed (extended) Circular muscle contracted
Fig
Longitudinal muscle relaxed (extended)
Circular muscle contracted
Circular muscle relaxed
Longitudinal muscle contracted
Bristles
Head end
Head end
Head end

20. Gap junction allows for coordinated behavior= contractions
No striations , single cell has spindle shape
The contraction of smooth muscle tends to be slower than that of striated muscle.
often sustained for long periods.

21. Smooth muscle (like cardiac muscle) does not depend on motor neurons to be stimulated.
However, motor neurons (of the autonomic system) reach smooth muscle and can stimulate it — or relax it — depending on the neurotransmitter they release (e.g. noradrenaline or nitric oxide, NO)
Smooth muscle can also be made to contract by other substances released in the vicinity (paracrine stimulation)
Example: release of histamine causes contraction of the smooth muscle lining our air passages (triggering an attack of asthma)by hormones circulating in the blood
Example: oxytocin reaching the uterus stimulates it to contract to begin childbirth.