Exercise Physio LECTURE 1.txt

Cerebrum - responsible for higher mental functions, movement, visceral functions, perception, behavioral reactions, and for the association and integration of these functions. 

Motor Cortex - consists of the primary motor cortex and the premotor cortex

Premotor Cortex - causes general patterns of movement involving groups of muscles that perform specific tasks. Involved in the unconscious fine tuning of muscle activity required for highly-skilled movements.

Sensory Cortex - relays information into the motor cortex for control of motor activities

Basal Ganglia - functions in muscle tone, control of movement

Thalamus - acts primarily as a relay station of sensory input as well as interpretation of some sensory input, such as pain, temp, crude pressure and touch

Cerebellum - coordination of movement

Medulla Oblongata - controls heart rate, blood flow, equilibrium, swallowing, salivation and respiration

Pons - controls respiration; also involved in facial/neck sensations and the regulation of facial expressions, eye movement, taste, salivation and equilibrium.

Midbrain - conveys sensation of touch, proprioception and vibrations to the thalamus; also, involved in the regulation of eye movement, pupil size and lens shape.

Pyramidal System - Of the pyramidal motor tracts, 90% cross-over at the decussation of pyramids and 10% are ipsalateral

Extrapyramidal System - general movement patterns (i.e., muscle tone and posture, control of head movement to vision and hearing, and equilibrium), highly-skilled movements which facilitate the execution of whole movement patterns without conscious awareness of the individual parts (i.e., allows for fine tuning)

Sensory receptors that provide feedback to the CNS include:

• Muscle Spindles
• Golgi Tendon Organs
• Bulbs of Krause
• Pacinian Corpuscles
• Ruffini End Organs 

Limbic System - provids input to the motor cortex regarding motivation drives and needs

"descend along the same side/do not cross-over)

occurs when only one side of the body is developed through motor training, but due to a cross-transfer effect the other side of the body does receive some neural stimulus and hence, is developed to some extent.

provide sensory information regarding joint angle, acceleration at the joint, and the degree of deformation brought about by pressure.

Greatly contribute to kinesthetic awareness because they prodvide info regarding body awareness

Pacinian corpuscles detect changes in vibrations

Ruffini corpuscles detect changes in temp

in general, sense position, length, tension, pressure and temp in a muscle and hence, regulate rate of change in length as well as facilitating kinesthetic awareness.

proprioceptors located in muscles at their junctions with tendons and in ligaments of joints; if force of contraction and consequently tension is too great, inhibits alpha and gamma motor neuron of contraction muscle thereby reducing excess tension and thus preventing injury (protective mechanism - reflex inhibition).

Also, appear to help equalize the contractile forces of seperate muscle fibers.

proprioceptors located in intrafusal muscle fibers which lie parallel to the extrafusal (normal) muscle fibers.

involved in gross muscular contraction

activate the intrafusal muscle fibers

sensory receptors that detect the length or stretch on the intrafusal muscle fibers

receives and carries information from annulospiral endings via spinal cord

• (1) sense length of fibers
• (2) reflex contraction
• (3) coavtivation

a motorneuron and all the muscle fibers that it innervates

• -each is the same in fiber type composition (either SO, FOG, or FG - no mixtures)
• -each type differs in sensitivity to stimulation (SO is easiest, FG is hardest - size principle)
• -each operates on "all-or-none" principle
• -all fibers in motor unit are equally sensitive to neural stimuli

Force Production Determinants

• -dependent on actin and myosin bonding*
• -# of fibers w/in active motor units (hyperplasia will increase fiber #)
• -# of motor units activated
• -size of fiber wi/in active motor units (hypertrophy)
• -balance between stimulating and inhibiting hormones
• -frequency of impulses
• -speed of movement and fiber type

innervate the extrafusal muscle fibers

a nerve cell

cell body of a neuron

process of a neuron that carries impulses away from the cell body

portion of a neuron that carries impulses toward the cell body

responsible for producing myelin

portion of a myelinated axon which is not covered by myelin sheath

important for saltatory conduction as impulse "jumps" from one Node of Ranvier to the next allowing for fast nerve impulse conduction

the point of contact where nerve impulses are transmitted from one neuron to another

the membrane proximal to a synapse

the membrane distal to a synapse

gap between pre and post synaptic membrane

vesicles in the axon terminal where neurotransmitters are stored

connective tissue surrounding a muscle; connects into tendon at the origin and insertion of the muscle

connective tissue surrounding a fasciculus or group of muscle fibers

connective tissue surrounding a muscle cell or fiber

muscle cell membrane

cytoplasm of muscle cell; site of anaerobic metabolism

site of cellular oxidation or aerobic metabolism; powerhouse of the cell

threadlike protein strands

functional unit of the muscle cell; runs from Z line to Z line

thin protein myofilaments

thick protein myofilaments

also called S-1 heads; extend from actin and myosin

long, thin molecules that lie on the surface of the actin strand

globular molecules (tropomyosin molecules embedded)

anchored to the sarcolemma

• (1) anchors actin (pulling mechanism)
• (2) keeps actin properly oriented around myosin (surrounding)
• (3) provides pathway for T-tubule system to go deep into muscle tissue

light areas near the Z lines consisting of the thing, actin myofilaments

dark areas consisting of both the thin myofilaments and the thick, myosin myofilaments

slight variation in the shading of the A band due to absence of the actin myofilaments

appear to parallel Z lines (invaginations of the cell membrane)

run parallel to myofibrils

store Ca⁺⁺

collectively, the two cisternae and T tubule are known as the triad

• (1) influx of Ca⁺⁺ into the axon terminal stimulates the release of acetylcholine (contraction - step 1)
• (2) binding of calcium to regulatory sites on troponin remove the inhibition between actin and myosin (contraction - step 4)

• (1) the release of previously stored energy drives the power stoke of the myosin S-1 head resulting in the pulling (sliding) of actin over myosin (contraction - step 5)
• (2) new molecule of ATP binds to myosin S-1 head causing the dissociation of actin and myosin; myosin ATPase breaks ATP down into ADP + P_i, heat, and energy which is used to tilt the myosin S-1 head back down and away from actin to the resting, relaxed position (contraction - step 6)
• (3) ATP is used to actively pump Ca⁺⁺ back into the sarcoplasmic reticulum cisternae when the nerve impulse stops (relaxation - step 1)

twitches occur at the rate of 100-200 per second during sustained muscular contraction

• (1) peak rate of muscle contraction (peak twitch rate) is dependent on myosin ATPase activity and the size (thickness) of the motor axon
• (2) maximal force (tension) that a muscle can generate is dependent on the amount of actin-myosin binding that is taking place
• (3) continuation of muscle contraction is dependent on the ability to recycle ATP

speed of contraction dependent on

• A. size of axon (myelination)
• B. myosin ATPase; FT > ST

FG > FOG > SO

maximum tension dependent on action-myosin binding; FT > ST

FG > FOG > SO

continuation of muscle contraction is dependent on ability to recycle or regenerate ATP; ST > FT

SO > FOG > FG

myosin ATPase high in FT glycolytic, anaerobic fiber

SDH high in ST fibers

(light circle, dark circle) 50% ST oxidative - aerobic [SO, Type I, Red]

(two dark circles) 30% FT high oxidative glycolytic [FOG, Type IIa, Intermediate]

(dark circle, light circle) 20% FT glycolytic - anaerobic [FG, Type IIb, White]

(various physiological mechanism underlying the properties)

(various physiological mechanism underlying the properties)

(various physiological mechanism underlying the properties)

motor units whose neurons have a smaller cell body (i.e., ST motor units) are generally recruited first followed by motor units whose neurons have a larger cell body (FT motor units).

Cross-innervation studies indicate that "neurons dominate the response characteristics of the muscle tissue" due to either (theories) axoplasmic flow of a genetic substance theory or use-disuse theory.

Although traditional thought suggested that ST fibers could not be converted to FT fibers and vice-versa; recent studies indicated that sprint training increase FT fibers and decreased ST fibers

more research is needed to resolve the issue

"neurons dominate the response characteristics of the muscle"

2 Theories

• (1) axoplasmic flow
• (2) use-disuse

"genetic substance"

Muscle fiber type composition for a muscle shows basically normal distribution in both men and women.

1-5, 1-5A, 1-5B

• A. Number of fibers within an active motor unit
• B. Number of motor units activated within a muscle
• C. Size of fibers within an active motor unit
• D. Balance between stimulating (acetylcholine) and inhibition (GABA) neurotransmitters
• E. Frequency of neural impulses
• F. Synchronous, coordinated firing of motor units
• G. Motor unit recruitment patterns
• H. Speed of movement and fiber type
• I. Initial length of the muscle fibers
• J. Angle of pull
• K. Architecture (configuration) of tendon and muscle fibers

1-6

(1) Metabolic by-products, such as lactic acid accumulation from anaerobic glycolysis or the accumulation of ketone bodies from the breakdown of fatty acids in the absence of the needed carbohydrates to prime the pump for fat utilization, will decrease the pH of muscle tissue; a decrease in pH will interfere with Ca⁺⁺ release from the sarcoplasmic reticulum, actin-myosin binding, and ATP breakdown for energy

(2) Deletion of the neurotransmitter acetylcholine in the motor neuron axon terminal

(3) Depletion of the intramuscular phosphagen stores 

(4) A greater relative distribution of FT muscle fibers in the working muscles will result in an earlier onset of fatigue; FT muscle fibers (particularly FG) have much lower oxidative capabilities and consequently endurance capabilities than the ST oxidative muscle fibers and to a certain extent, the FOG muscle fibers

1-7

(1) FT muscle fibers have faster speeds of movement capabilities than ST muscle fibers; consequently, an individual with a relatively high distribution of FT muscle fibers can potentially move at faster speeds of movement than an individual with a relatively high distribution of ST muscle fibers. About 25% of the difference in speed of movement capabilities can be attributed to amount of FT muscle fiber types

(2) The greater the force production capabilities relative to resistance, the greater the potential speed of movement; similarly, the greater the force production capabilities relative to body weight, the greater the potential acceleration of the body and consequently, the greater the potential speed of movement. Hence, an increase in force production capabilities or a decrease in excess fat weight will increase the potential speed of movement.

(3) The greater the coordination via synchronous recruitment of agonist and antagonist muscle groups, the greater the potential speed of movement.

1-8, 1-8A

Phosphagen or ATP-PC System

Anaerobic Glycolytic

Lactic Acid System

Aerobic Glycolytic System

Kreb's Cycle

Beta or Fat Oxidative System

Electron Transport System

be able to match the substrates and enzymes with the correct cycle or system

Sarcoplasm

• -phosphagen ATP-CP or alactate
• -anaerobic glycolysis or lactic acid
• -aerobic glycolysis or CHO oxidation STARTS in sarcoplasm
• -beta (fat) oxidation TG's start in sarcoplasm

Mitochondria

• -aerobic glycolysis or CHO oxidation ENDS in mitochondria
• -beta (fat) oxidation
• -ETS inside inner membrane of mitochondria

citrate from inhibits PFK to slow down glycolysis to spare CHO to prime the pump for fat usage

pyruvate converted to oxaloacetate to combine with acetyl CoA from fat to form citrate

cardiac muscle = 38 ATP

skeletal muscle = 36 ATP

2

• Phosphagen ATP-CP
• -myosin ATPase
• -CPK (creatine phosphokinase)
• -AK (adenylate kinase)

• Anaerobic Glycolysis
• -phosphorylase
• -HK (hexokinase)
• -PFK (phosphofructokinase)
• -PK (pyruvate kinase)

• Aerobic Glycolysis
• -CS (citrate synthase)
• -SDH (succinate dehydrogenase)
• -O₂
• -ETS cytochromes
• -kreb's cycle enzymes

• Beta Oxidation
• -lipase
• -thiokinase
• -thiolase
• -O₂
• -ETS cytochromes
• -kreb's cycle enzymes

• ETS
• -cytochromes

At the onset of exercise, the energy system respond in the following order in reach steady state exercise:

• (1) phosphagen metabolism
• (2) anaerobic glycolysis
• (3) oxidation metabolism
• (3a) anaerobic glycolysis - CHO oxidation (moderate intensity)
• (3b) beta oxidation (low intensity)

12-15 seconds

45-60 seconds

greater than 4 minutes

• Thyroxine
• Cortisol
• Glucagon
• Epinephrine
• Norepinephrine
• Insulin - inhibits HSL (hormone sensistive lipase) & decreases fat mobilization
• Caffeine - stimulates HSL (also stimulates phosphorylase in glycolysis)

Exercise decreases insulin release from pancreas

CHO Loading Prior to Exercise

approximately 1-week prior to a major endurance event, perform a long workout to deplete the muscle glycogen stores. Then for the next 3 days eat a low CHO diet. Then, switch to a high CHO diet for the 3 days prior to the major endurance competition.

CHO Fluid Ingestion During Exercise

During exercise, drink 4-8 ounces of cold water every 10-15 minutes containing a 5-10% glucose concentration.

Both CHO loading prior to exercise and the ingestion of CHO fluids during exercise will significantly increase muscle glycogen levels thereby enhancing performance during moderate intensity, long duration exercise. The capacity of aerobic glycolysis will be increased as well as the capacity of fat oxidation due to an increase in muscle glycogen which is also needed to prime the pump for fat utilization.

Recent research indicates that CHO loading prior to high intensity, short duration exercise enhances performance by increasing work time to exhaustion before fatigue occurs.

Recent research also indicates that CHO fluid ingestion will enhance intermittent high intensity exercise performance by increasing work time to exhaustion before fatigue occurs.

This type of intermittent high intensity exercise is similar to what is experienced by athletes in sports such as basketball, soccer and hockey. During high intensity, short duration exercise, CHO loading prior to exercise and CHO fluid ingestion during exercise appears to enhance CHO availability and hence anaerobic work capabilities.