Muscle Physiology

1
Muscle Physiology

• Chapter 1

2
Objectives

• Describe the micro and macrostructure of muscle
• Describe the sliding filament theory
• Differentiate types of muscle actions
• Discuss factors that affect force production

3
Huxley?
4
KEY POINT

• The muscular system is the organ system
  responsible for movement. Muscles develop
  tension, causing bones to act as levers and
  rotate around an axis.

5
(No Transcript)
6
Neuromuscular Components

• Neuromuscular junction- the point where a motor
  neuron joins muscle fibers, the motor end plate
• Motor unit- a motor neuron and all the muscle
  fibers it innervates
• All or none law- all the muscle fibers in a motor
  unit contract, or none contract

7
(No Transcript)
8
(No Transcript)
9
(No Transcript)
10
Structure of a Muscle Cell

• Sarcoplasm- the cytoplasm of a muscle fiber,
  contains mitochondria, sarcoplasmic reticulum
• Sarcomere- smallest contractile unit of muscle
  tissue
• Sarcoplasmic Reticulum contains calcium.

11
(No Transcript)
12
(No Transcript)
13
(No Transcript)
14
(No Transcript)
15
(No Transcript)
16
Structure of a Muscle Cell

• Myofibrils- long fibers in the sarcoplasm of
  muscle cells
• Actin (thin)
• Myosin (thick)
• Crossbridges- globular heads on the myosin
  molecules

17
(No Transcript)
18
Structure of Skeletal Muscle

• Contractile proteins- actin and myosin
• Myofibril- muscle fiber, one muscle cell
• Regulatory proteins- troponin and tropomyosin
• Sarcomere- Z-line to Z-line
• Sarcoplasmic reticulum/T-tubules-
  communications system in the muscle cell

19
(No Transcript)
20
Sliding Filament Theory of Muscle Contraction

• 1. Resting phase- calcium is segregated in the
  sarcoplasmic reticulum (SR), few crossbridges are
  attached, the muscle cell is at rest

21
Sliding Filament Theory of Muscle Contraction

• 2. Excitation phase- contraction coupling phase-
  calcium ions are released from the SR, troponin
  and tropomyosin undergo a conformational change,
  allowing actin to bind to myosin, causing flexion
  of the myosin head

22
Sliding Filament Theory of Muscle Contraction

• 3. Contraction phase- ATP causes myosin heads to
  detach from actin, ATP is hydrolized which
  cocks the myosin head, the myosin head attaches
  to the next active site

23
Sliding Filament Theory of Muscle Contraction

• 4. Recharge phase- as long as ATP is present to
  break the attraction of actin to myosin, and
  calcium is present, the cycle continues causing
  tension to develop in the muscle

24
Sliding Filament Theory of Muscle Contraction

• 5. Relaxation phase- stimulation from the motor
  nerve stops, calcium is re-segregated into the
  sarcoplasmic reticulum, troponin and tropomyosin
  return to their original shape and block the
  attraction of actin and myosin, the muscle
  returns to the resting unbound state

25
Cycle Time
26
Sliding Filament Animation

• http//www.sci.sdsu.edu/movies/actin_myosin_gif.ht
  ml

27
(No Transcript)
28
(No Transcript)
29
(No Transcript)
30
(No Transcript)
31
Summary of Muscle Contraction

• Acetylcholine (ACH) released from terminal
  portion of motor neuron
• ACH crosses the gap at the neuromuscular junction
• Muscle fiber membrane depolarizes through
  transverse tubules to the sarcoplasmic reticulum

32
Next Class

• Finish Chapter 1