This document provides information on muscle physiology, including the different types of muscles and their functions. It discusses skeletal, smooth, and cardiac muscles. Skeletal muscles are voluntary muscles that attach to bones and allow for movement. They contain repeating contractile units called sarcomeres and require ATP for contraction. Smooth muscles are involuntary and found in organs and blood vessels. They do not contain sarcomeres and have slower, longer contractions regulated by calcium. Cardiac muscle exclusively makes up the heart and has automatic, rhythmic contractions driven by pacemaker cells.

1. Muscles physiology

2. Muscles function
Contract!
Generate motion
Generate force
Generate heat
Support

3. Muscular Functions
 Body movement (Locomotion)
 Maintenance of posture
 Respiration
 Diaphragm and intercostal contractions
 Communication (Verbal and Facial)
 Constriction of organs and vessels
 Peristalsis of intestinal tract
 Vasoconstriction of b.v. and other structures (pupils)
 Heart beat
 Production of body heat (Thermogenesis)

4. Properties of Muscle
 Excitability: capacity of muscle to respond to a
stimulus
 Contractility: ability of a muscle to shorten and
generate pulling force
 Extensibility: muscle can be stretched back to its
original length
 Elasticity: ability of muscle to recoil to original
resting length after stretched

5. Muscle Types
 Cardiac – heart
 Smooth – internal organs
 Skeletal – "voluntary"
Attach to bone
Move appendages
Support body
Antagonistic pairs
Flexors
Extensors

6. Categories of skeletal muscle actions
 Categories Actions
 Extensor - Increases the angle at a joint
 Flexor- Decreases the angle at a joint
 Abductor - Moves limb away from midline of body
 Adductor - Moves limb toward midline of body
 Levator - Moves insertion upward
 Depressor Moves insertion downward
 Rotator - Rotates a bone along its axis
 Sphincter -Constricts an opening

7. Types of Muscle
 Skeletal
 Attached to bones
 Makes up 40% of body weight
 Responsible for locomotion, facial expressions, posture, respiratory
movements, other types of body movement
 Voluntary in action; controlled by somatic motor neurons
 Smooth
 In the walls of hollow organs, blood vessels, eye, glands, uterus, skin
 Some functions: propel urine, mix food in digestive tract,
dilating/constricting pupils, regulating blood flow,
 In some locations, auto rhythmic
 Controlled involuntarily by endocrine and autonomic nervous systems
 Cardiac
 Heart: major source of movement of blood
 Auto rhythmic
 Controlled involuntarily by endocrine and autonomic nervous systems

8. Connective Tissue Sheaths
 Connective Tissue of a Muscle
Epimysium. Dense regular c.t. surrounding entire muscle
Separates muscle from surrounding tissues and organs
Connected to the deep fascia
Perimysium. Collagen and elastic fibers surrounding a
group of muscle fibers called a fascicle
Contains b.v and nerves
Endomysium. Loose connective tissue that surrounds
individual muscle fibers
Also contains b.v., nerves, and satellite cells (embryonic
stem cells function in repair of muscle tissue
 Collagen fibers of all 3 layers come together at each end of
muscle to form a tendon or Aponeurosis.

9. Muscle Types
Figure 12-1: Three types of muscles

10.  About 40% body mass
 Muscle fibers – cells
 Fascicle – bundle
 Motor unit
 Muscle
 sheath
 Attach to tendons (which attach to bone)
Skeletal Muscle Anatomy

11. Nerve and Blood Vessel Supply
 Motor neurons
stimulate muscle fibers to contract
Neuron axons branch so that each muscle fiber (muscle
cell) is innervated
Form a neuromuscular junction (= my neural junction)
 Capillary beds surround muscle fibers
Muscles require large amounts of energy
Extensive vascular network delivers necessary oxygen
and nutrients and carries away metabolic waste produced
by muscle fibers

12. Skeletal Muscle Anatomy

13. Skeletal Muscle Anatomy

14.  Multiple nuclei
 Sarcolemma
 T-tubules
 Sarcoplasmic reticulum
 Sarcoplasm
Mitochondria
Glycogen & ions
Myofibrils
Muscle Fiber Structure

15. Muscle Fiber Structure
Figure 12-3b: ANATOMY SUMMARY: Skeletal Muscle

16.  Actin –"thin fibers"
 Tropomysin
 Troponin
 Myosin – "thick fibers"
 Titin – elastic anchor
 Nebulin – non-elastic
Myofibrils: Site of Contraction

17. Myofibrils: Site of Contraction

18. Sarcomere: Organization of Fibers
Figure 12-6: Titin and nebulin

19. Skeletal Muscle Contraction: Mechanism
Figure 12-11a: Excitation-contraction coupling

20. Skeletal Muscle Contraction: Mechanism

21. Energy for Contraction: ATP & Phosphocreatine
• Aerobic Respiration
• Oxygen
• Glucose
• Fatty acids
• 30-32 ATPs
• Anaerobic Respiration
• Fast but
• 2 ATP/glucose
• Phosphocreatine ATPs

22. Energy for Contraction: ATP & Phosphocreatine
Figure 12-13: Phosphocreatine

23. Smooth Muscle
 Fusiform cells
 One nucleus per cell
 Nonstriated
 Involuntary
 Slow, wave-like
contractions

24. Smooth Muscle
• Cells are not striated
• Fibers smaller than those in skeletal
muscle
• Spindle-shaped; single, central
nucleus
• More actin than myosin
• No sarcomeres
• Not arranged as symmetrically as
in skeletal muscle, thus NO
striations.
• Caveolae: indentations in
sarcolemma;
• May act like T tubules
• Dense bodies instead of Z disks
• Have noncontractile intermediate
filaments

25. Smooth Muscle
• Grouped into sheets in walls of hollow organs
• Longitudinal layer – muscle fibers run parallel to organ’s long axis
• Circular layer – muscle fibers run around circumference of the organ
• Both layers participate in peristalsis

26. Smooth Muscle
• Is innervated by autonomic nervous system (ANS)
• Visceral or unitary (single unit) smooth muscle
• Only a few muscle fibers innervated in each group
• Impulse spreads through gap junctions
• Whole sheet contracts as a unit
• Often autorhythmic
• Multiunit:
• Cells or groups of cells act as independent units
• Arrector pili of skin and iris of eye

27. Smooth Muscle Cell

28. Myosin of Smooth Muscle
• Different isoform than that found in skeletal
muscle
• Smooth muscle myosin ATPase activity is
much slower, contraction is longer
• Myosin light chain in the myosin head
regulates contraction and relaxation

29. Smooth Muscle
• Relatively little sarcoplasmic reticulum
• Lacks T-tubules
• Chemically linked to the cell membrane,
rather than mechanically linked
• Ca +2 storage is supplemented by caveolae ,
small vesicles that cluster close to the cell
membrane. Voltage/ligand gated Ca +2
channels

30. Single-Unit Muscle

31. Properties of Single-Unit Smooth Muscle
• Gap junctions
• Pacemaker cells
with spontaneous
depolarizations
• Innervation to few
cells
• Tone = level of
contraction without
stimulation
• Increases/decreases
in tension
• Graded Contractions
• No recruitment
• Vary intracellular
calcium
• Stretch Reflex
• Relaxation in
response to sudden
or prolonged stretch

32. Multi-Unit Muscle

33. Comparisons Among Skeletal, Smooth, and Cardiac Muscle

34. Thank you