Muscle Contraction Essay

Exercise 8 Simple Muscle Contraction
• 3 Phases
AB
- lag phase or latent phase
- (shortest) 0.00sec, usually less than 0.01sec
- brief period that exists between the application of the stimulus and the start of contraction
BC
- contraction, 0.05sec
- peak
- shortening of the muscle occur
CD
- relaxation period, 0.05 sec
- Occurs when Ca+ is transported back in the sarcoplasmic reticulum
Single muscle contraction= 100vib/sec (tuning fork)= 0.10 sec
10vib (result)
Neuromuscular junction
- formed when several branches of axons form a single muscle fiber
- also called synapse
- connection between a muscle fiber and nerve
"All or none" law of muscle contraction
- refers to the action potential that influences a muscular fiber to stimulation
Exercise
9 Summation
A- First baseline
B- Second baseline; first peak
C- Second peak
AB- first contraction
BC- second contraction
CD- relaxation
Summation
- a result of addition of the excitatory and inhibitory effects of many stimulus applied to a neuron - when a stimulus is applied in rapid succession, increase strength of muscle contraction occurs - what happens during summation? o When you apply a single stimulus, Ca+ ions are released causing the muscles to contract but when two rapid successive stimuli are applied before relaxation occurs, the muscle again will contract
Treppe
- forms a staircase muscle contraction
Tetanus
- sustained contraction when the muscle is stimulated repeatedly such that the interval between the stimuli is less than the contraction time
1. complete/fused- sustained contraction without partial contraction,
80-100times per sec contraction

2. incomplete- sustained contraction with partial relaxation, 20-30times per sec contraction

With the permission of Ma'm Salvador. Prepared by 2AMT Class Secretary.

Refractory period
- time which an excitable cell cannot respond to a stimulus that is usually adequate to evoke an action potential
Absolute refractory period
- time during which a second action potential cannot be initiated, even with a very strong stimulus Relative refractory period
- period which a second action potential can be initiated but only on a supramaxinal stimulus
Exercise 10 Isotonic and Isometric Contractions
A. Isometric contraction (equal distance) o length of muscle does not change but the amount of force increases as contraction occurs o eg. holding an object, standing
B. Isotonic contraction (equal tension) o length of the muscle changes but force is constant o eg.
walking, running, dancing: movements of the upper limb exhibit predominant isotonic contractions
1. Concentric isotonic contraction o contractions in which muscle tension increases as the muscle shortens o eg. bicep curling, straightening the arm, moving the hand from side to side
2. Eccentric isotonic contraction o contractions in which tension is maintained as the muscle lengthens o eg. person letting a heavy weight down slowly a person using his hamstring muscles when running downhill, overloading the bicep so that it straitens, contractions of quadriceps muscle when descending the stairs
Exercise 11 Pithing
Pithing
- destruction of CNS to render the frog free from pain
Signs of successful pithing
- needle has destroyed branches of the sciatic nerve
- frog's legs to extend forward and quiver a few moments
- with the withdrawal of needle, frog should remain limp throughout the experiment
Exercise 12 Muscle-Nerve Preparation
Purpose of teasing thigh muscles: to expose the sciatic nerve
Exercise 13 Applications of the Different Forms of Stimuli
Different forms of stimuli
A. Mechanical stimulus- single muscle contraction
B. Thermal stimulus
1. Hot water- single muscle contraction
2. Cold/iced water- single muscle
contraction
C. Chemical stimulus- series of muscle contraction
D. Electrical stimulus
1. Direct current- single muscle contraction

Set-up: battery connected to simple key and electrode/stimulator simple key connected to battery and electrode/stimulator electrode/stimulator connected to battery and simple key

2. Indirect current- series of muscle contraction
With the permission of Ma'm Salvador. Prepared by 2AMT Class Secretary.

Set up: battery connected to simple key and inductorium simple key connected to battery and inductorium inductorium connected to simple key, battery and electrode/stimulator Subthreshold stimulus
- does not cause action potential and no contraction occurs
Threshold stimulus
- produces action potential, contraction occurs
Exercise 15 Complex Coordinated and Uncoordinated Reflex
Reflex: RIPPU- Rapid. Involuntary. Programmable. Predictable. Unconscious. motor response to a specific stimulus
Reflex arc eg. Blink reflex
1 receptor
1 receptor: Sensory organ (Eye)
2 sensory neuron
2 Sensory/afferent neuron: Optic nerve
3 interneuron/association
3 interneuron: brain
4 motor neuron
4 motor/efferent: occulomotor nerve
5 effector (muscle/gland)
5 effector organ: levator palpibrae superioris or orbicular is oculi- closes the eye
Spasmodic movement
- strychnine solution: destroys enzyme acetylchlorinesterase
- acetylchlorinesterase: stimulates excitatory neurotransmitter inhibitor, binds with amino acid glycine which is another neurotransmitter for relaxation and contraction equilibrium hence the muscle will remain contacted in the diaphragm
Complex reflexes
- both flexors and extensors may be stimulated hence also sends signals to the other unit which is contralateral to extend for the preservation of life
Exercise 35 The Effect of Temperature on Cardiac Contractions
• intact muscle - 70beats per min
• in hot ringer's solution - increases (84beats per min)
• in cold ringer's solution - decreases (40beats per min)
• effects of: o Ca- increase vigor o K- decrease vigor
• effects of: o sympathetic cardia- increase o parasympathetic cardia- decrease o tachycardia- abnormal excessive rapid heartbeat which is over 100beats/min

o bradycardia- slow heart beat under 60beats/min
• contraction: high temperature- increase heart rate low temperature- decrease heart rate
*human: 60-80beats/min

With the permission of Ma'm Salvador. Prepared by 2AMT Class Secretary.