Muscle anatomy and physiology

Question 1

What are the funtions of muscle tissue

Answer 1

Ø Producing body movements
Ø Stabilizing body positions
Ø Regulating organ volumes
-bands of smooth muscle called sphincters
Ø Movement of substances within the body
-blood, lymph, urine, air, food and fluids, sperm
Ø Producing heat
-involuntary contractions of skeletal muscle (shivering)

Question 2

Properties of muscle tissue

Excitability, Conductivity, Contractility, Extensibility, Elasticity

Answer 2

Excitability - respond to chemicals released from nerve cells
Conductivity - ability to propagate electrical signals over membrane
Contractility - ability to shorten and generate force Extensibility - ability to be stretched without damaging the tissue
Elasticity - ability to return to original shape after being stretched

Question 3

What are the three categories of muscles in mammals

Answer 3

skeletal, smooth, cardiac

Question 4

what are the main characteristics of Smooth muscle tissue?

Answer 4

• Attached to hair follicles in the skin
• Not striated
• Involuntary
• Located in hollow organs

Question 5

what are the main characteristics of Cardiac muscle tissue

Answer 5

• Only in the walls of the heart
• Striated
• Involuntary
• Auto-rhythmic because of built in pacemaker

Question 6

what are the main characteristics of Skeletal muscle tissue

Answer 6

• Attached to bones and skin
• Striated
• Voluntary (i.e. conscious control)
• Can be involuntary
• Powerful
• Primary topic of this lecture

Question 7

Skeletal muscle organisation

Answer 7

photo

Question 8

Skeletal muscle organisation

Connective tissue, Epimysium, Perimysium, Endomysium

All these connective tissue layers extend beyond the muscle belly to form the tendon

Answer 8

Connective tissue components of muscle
Superficial fascia is loose connective tissue & fat underlying the skin
Deep fascia = dense irregular connective tissue around muscle
Epimysium - dense regular connective tissue surrounding entire muscle
Perimysium - fibrous connective tissue surrounding fascicles (groups of muscle fibers)
Endomysium - fine areolar connective tissue surrounding each muscle fiber

Question 9

muscle composition - Fibers differ in myoglobin, mitochondrial ATPase activity and cytochrome content (production, transport, & storage of O2 and ATP)

what is the difference between red fibres “Slow-twitch” and white fibres “Fast twitch”

Answer 9

Red fibres “Slow-twitch”
Small; high oxidative capacity; ATP from
β-oxidation of fatty acids

White fibres “Fast-twitch”
Large; lower oxidative capacity;
Mostly anaerobic glycolysis;
Fatigue rapidly

Question 10

Requirements for Skeletal Muscle Contraction
1. activation -
2. Excitation -
what are they?

Answer 10

1. Activation: neural stimulation at a neuromuscular junction (NMJ)
2. Excitation-contraction coupling:
   • Generation and propagation of an action potential (AP) along the sarcolemma
   • Final trigger: a brief rise in intracellular Ca2+ levels

Question 11

what is the Sliding Filament Model of Contraction

photo

Answer 11

In the relaxed state, thin and thick filaments overlap only slightly
During contraction, myosin heads bind to actin, detaches, and binds again, to propel the thin filaments toward the M line
As the H zones shortens and disappears, sarcomeres shorten, muscle cells shorten, and the whole muscle shortens

Question 12

sliding filament theory PHOTO cylce

Answer 12

PHOTO (1. Binds, 2. Pulls, 3. Detaches, 4. myosin prepares, 5. Repeat)

Question 13

What is the ‘all-or-none’ principle?

Answer 13

If a stimulus is above a certain threshold, a nerve or muscle fiber will fire.

• The strength of a response of a nerve cell or muscle fiber is not dependent upon the strength of the stimulus.
• Nerve cell and skeletal muscle cell it innervates form a motor unit
• Four to several hundred muscle fibers supplied by motor neuron