Muscular Contractions Flashcards
Discuss the four basic types of muscle contraction:
- Isokinetic: constant velocity
- Dynamic: concentric, eccentric
- Isotonic: constant tension
- Isometric: constant length, no change
Discuss the five mechanical factors that can affect force production of skeletal muscle:
- Length-Tension Relationship: force directly related to actin-myosin interacting
- long length = low tension (3.5µm )
- optimal length = high tension (2.3-2.0µm)
- short length = low tension due to mechanical interference
- Force-Velocity Relationship: inversely related
- Cross-Sectional Area: Larger cross-sectional area, greater force produced
- Line of Pull & Muscle Type:
- Force Production: pennate fiber arrangement > longitudinal fiber arrangement
- Range of Motion: longitudinal fiber arrangement > pennate fiber arrangement - Stretch Shortening Cycle: increase force production with addition of stored elastic energy
Discuss the two major theories for DOMS:
Mechanical Trauma Mode:
1. structural damage to sarcolemma
2. disruption of calcium homeostasis
3. cell death
4. cellular debris & immune cells lead to inflammation/pain
Localized Ischemia Model:
1. swelling in muscle from activity & increase tissue pressure
2. ischemia, pain/spasm, additional spasm
Discuss the strategies for treatment & prevention of DOMS:
- Stretching: initiates inverse myostatic stretch reflex; stimulates GTO which relaxes stretched muscle
- Acute Exercise: endorphins
- Anti-inflammatories (NSAIDs): aspirin, ibuprofen (usually before exercise)
Discuss (draw and label) nerve anatomy (sensory & motor):
Motor Nerve: efferent pathway — CNS — Muscle
Sensory Nerve: afferent pathway — muscle — CNS
Discuss the events occurring when the action potential reaches the nerve terminal so depolarization will occur on surface of the muscle: (8)
- AP travels down axon
- Opens voltage gated Ca2+ channels so calcium moves into nerve terminals
- Vesicles (Ach) migrate to end & fuse to membrane
- Pre-synaptic vesicles undergo exocytosis
- Act released into NM junction
- Ach binds Ach receptors on sarcolemma & changes sarcolemma permeability
- Na+ enters & K+ leaves muscle fiber causing depolarization of sarcolemma as AP moves in both directions & down t-tubules
- signal termination and Ach esterase breaks down acetyl choline to acetate + choline
Compare the pyramidal & extrapyramidal tracts:
Pyramidal Tracts: cell bodies originate in motor cortex
- travels down spinal column & synapse with cell bodies of alpha motoneurons in ventral horns of gray matter
Extra Pyramidal Tracts: all other descending tracts
- originates in nasal nuclei & reticular formation
- responsible for muscle tone, posture, & head movement
Define a reflex, types of reflexes, & various components of reflex arc:
Reflex: involuntary rapid movement responding to stimulus resulting in a specific muscular response.
1. Autonomic: cardia, smooth muscle, glands
2. Somatic: muscle withdrawal reflex & crossed-extensor reflex
Reflex Arc:
1. muscle senses/converts signal to neural signal and travels via sensory nerve/afferent pathways through dorsal root to gray matter
2. interacts directly with m motorneuron cell body in ventral horn of gray matter or through interneuron cell
3. axon of motoneuron leaves gray matter by ventral root/efferent pathway to muscle
Define proprioception and compare how the vestibular apparatus and the muscle spindle work (i.e., what do they respond to, major receptors, afferents, efferents, etc.)
Proprioception: kinesthesis or body awareness
- Vestibular Apparatus: inner ear; balance & head position
- 2 sets or organs & receptors
- utricle & saccule & macula receptor = linear head accelerations
- semicircular canals & crista amputaras receptor = angular head accelerations - Muscle Spindles: fluid filled sacs within skeletal muscle - 7 intramural fibers; respond to length changes/rates of change
- center of spindle: 7 intrafusal fiber & 2 nuclear bag fibers
- periphery of spindle: 5 nuclear chain fibers
- 2 afferent pathways:
1. Annulospiral nerve ending: central portion of 7 intrafusal fibers; rate changes
2. Flower spray nerve ending: both ends of nuclear chain fibers; length changes
- 1 efferent pathway to ends of all 7 fibers
- gamma fusimotor nerves
- used during isometric contractions
Contrast myostatic reflexes vs. clasp knife reflexes:
Myostatic Reflex: striking patellar tendon causes rapid stretching of quadriceps
- muscle spindle wants to correct & shorten quads
- reciprocal inhibition of hamstrings
- activation of agonist & inhibition of antagonist
Golgi Tendon Reflex: high tension sensed by biceps tendon so GTO wants to prevent injury/inhibit biceps
- activation of triceps
- inhibition of agonist & activation of antagonist
Discuss the various aspects of neuromuscular adaptations that can occur following the appropriate exercise program (3):
- Neural adaptation:
1. increase central neural drive
2. better motor unit coordination
3. inhibition of GTO - Increased strength
- Increased cross-section area:
1. increased size & number of myofilaments (actin, myosin, etc)
2, increased number & size of myofibrils
3. increased amount & strength of connective tissue
Discuss the effects of anabolic steroids on the following: liver, cardiovascular system, male/female reproduction, psychological aspects
- Liver:
- decreased excretory function
- blood filled cysts
- tumors - Cardiovascular:
- decreased HDL
- hyperinsulinemia
- increased BP - Male reproduction:
- decreased testosterone, testicular size, sperm production - Female Reproduction:
- decreased estrogen, progesterone, LH, FSH
- inhibits ovulation - Psychological Effects:
- large mood swings
- decreased libido
- increased aggression - Other:
- male balding
- acne
- premature closing of epiphyseal growth plates
