What are the three portions of the sensory - output pathway? What is each?
- Sensory input: somatosensory to CNS
- Central processing: either reflex or brain comes up with a plan
- Motor output: muscle function
Match the following: (afferent / efferent), (sensory / motor).
- Afferent = sensory
- Efferent = motor
- “Get the F out”
When resting, are nerves a net positive or negative charge?
For this class, once an AP starts, when does it stop?
For muscle contractions, what ion starts the depolarization?
T/F: Muscles AND neurons are excitable.
What are the levels of a muscle going from smallest to biggest?
What is a muscle cell called?
What are myofibrils?
- Bundles of myofilaments
- Make up fibers
- Actin / myosin
What is a motor unit?
- A motor neuron and all of the muscle fibers it innervates
- Can contact as few as 3-5 fibers and as many as 100
T/F: Nerves can contact whole muscles.
- Nerves can only contact portions of a muscle, not the whole muscle
What are the two types of muscle fibers?
- Type 1
- Type 2
What are type 1 muscle fibers?
- Slow twitch muscle fibers
- Oxidative (requires oxygen)
- Can last longer before fatigue
What is the difference between slow and fast twitch muscles?
It is the difference on how long it takes for the muscle to fully contract
What are type 2 muscle fibers? What are the two types?
- Fast twitch muscle fibers
- Type 2a (oxidative glycolytic): oxidative glycolytic: a hybrid between fast and slow twitch
- Type 2b (glycolytic): No O2 required; fatigues fast
T/F: Function determines the type of fiber. Give an example?
- Posture and abs muscles are flexed all day long = they are slow twitch
- This can alter with age though
Can you alter types of fibers due to training?
What are the three main rules of how muscles work?
- They can only contract and relax
- Muscles only work on a joint they cross
- Muscles work best in the direction of their fibers
What are muscles that only cross one joint best for? Two joints?
- 1: strength, 1 function
- 2: stabilizing, multiple functions
What is the agonist muscle?
- The “prime mover”
- The main muscle that creates a certain motion
What is the synergist muscle?
- A muscle that assists the agonist in generating movement force
- It has another purpose besides helping the agonist
What is the antagonist muscle?
- A muscle that does the opposite action of the agonist
- Usually placed on the opposite side of the joint
- Usually inactive in a motion
What is the neutralizer muscle?
- A muscle that can get rid of a portion of a motion that isn’t wanted
- Ex.: different muscles allow the biceps to flex with different wrist placements
What is the stabilizer / fixater muscle?
A muscle that helps provide stability on an area or joint
What are the three types of muscle contractions?
What is a concentric muscle contraction?
When a muscle shortens in length during a contraction
What is an isometric muscle contraction?
When there is no length change during flexion
What is an eccentric muscle contraction? When is it often used?
- When the muscle is active but insertion and origin spread apart
- During changing directions or braking
What are closed kinetic chains? What is an example?
- Aka “CKC”
- Movements where the DISTAL segment is fixed…
- And the PROXIMAL segment moves
- Push ups
What are open kinetic chains? What is an example?
- Aka “OKC”
- Movements where the PROXIMAL segment is fixed…
- And the DISTAL segment moves
What is tetanus?
Full contraction of a muscle
What is active tension recruitment? Why does the body use this?
- The body uses small neurons before it starts to use large ones
- The body uses small motor units before it spends bigger ones
- The body uses type 1 (long term) before type 2 fibers (fast twitch)
- This allows only energy needed to complete a task
What is the main determinant for if an action is active or passive?
Whether or not it uses ATP
What is rate coding and what does it have to do with graded muscle contractions?
- The frequency of APs
- 1 action potential is one muscle twitch
- When the twitches go back to back faster, there is more force (vise versa)
- This allows for no muscle waste
What is synchronization?
- Where the body learns how to turn on multiple motor units at the same time
- Simultaneously firing the motor neurons
What is passive force production?
- Aka passive tension
- This tension is produced by the fascia layers of the body and the tendons and ligaments (the passive elastic components)
How does the physiological length-tension relationship of a muscle impacts performance of that muscle (amount of force production)?
- When the muscle gets larger or shorter than its resting length, less actin and myosin can overlap and there will be less force production
- Passive tension: stretching and bounce back; there is less when the muscle is short
What is passive insufficiency?
- Deals with multi-joint muscles
- The inability of a muscle to lengthen passively and allow full range of motion at all joints it crosses
- The range of motion is still not fully there, but the muscle won’t allow any further movement
What is active insufficiency?
- Deals with the active piece of multi-joint muscles
- This deals with when a muscle can’t contract any further to allow range of motion of all the joints it crosses
- The muscle is fully contracted, but there is still more range of motion
How does the tenodesis grasp work?
- Passive sufficiency of flexors causes a grasping motion when the wrist is extended
- Passive sufficiency of extensors causes the hand to let go when the wrist is flexed
How does the speed of concentric contractions affect force development? Why?
- Slow speed yields higher force development
- Vise versa
- Due to slower speed, there will be more time to recruit more motor units and actin and myosin will have more time for cross-bridge formation
How does the speed of eccentric contractions affect force development? Why?
- Force production increases with increased speed of eccentrics to a point
- Elasticity comes into affect
- Cross bridges of actin and myosin is easily to ratchet down than flexing
What are reflexes?
- INVOLUNTARY reaction due to a stimulus
- Predictable behavior
What are Golgi Tendon Organs (GTO)? What do they do?
- Small sensors woven into tendons at muscle tendon junctions
- Responds to a stretch of a muscle (afferent) and collagen fibers due to increased tension
- Protect the tendons from stretching too far
***What is the response (efferent stimulus) of a GTO?
- Autogenic inhabitation: turns off the muscle being stretched
- Reciprocal excitation: turns on the opposite of the muscle stretched
What are muscle spindles?
- Small receptors woven into muscle fibers
- Responds to speed and length of a stretch (afferent)
- Involved in myotatic stretch reflexes
***What is the response (efferent stimulus) of a muscle spindle?
- Autogenic excitation: turns on the stretched muscle
- Reciprocal inhabitation: turns off the opposite of the stretched muscle
T/F: Muscle spindles and GTOs work together.
What is the myotatic reflex?
What is load compensation? How does it work?
- Regulating functional muscle length via muscle spindles
- Muscle spindle stretches and then body compensates via muscle contraction
What is the stretch-shorten cycle?
- Think springs
- For there to be a great force production there needs to be: active contraction, passive contraction, neurological work
- Actively loading + passively stretching (to get passive tension) + neurological (fast = engages spindles)
What is the size principle?
Refers to the principle of which smaller motor units are recruited before large ones so the body doesn’t waste any energy
What is the active aspect to contractions?
The working of actin and myosin