Chapter 3: The Muscular System Flashcards
How many muscles are there total in the body?
650 total
What are the attachment points for muscle on bone?
Origin: less movable attachment closest to the head
Insertion: more movable attachment closest to the feet
What’s the main similarity between ligaments, joint capsules and tendons?
-Limited blood supply and low metabolism
What does epimysium do?
- A thin layer of connective tissue that covers each muscle
- Protects the muscle from friction against other muscles or bones
What is skeletal muscle made of?
Bundles of muscle fibers
What is a myofibril?
A rodlike unit of a muscle cell made up of sarcomeres
What does a sarcomere do?
Shortens the muscle fiber
What chemical is needed in the cross-bridge cycle?
Calcium
What is the sliding filament theory of muscle contraction?
Skeletal muscle shortens because the thick and thin filaments slide past one another.
The lengths of the individual thick and thin filaments do not change.
How does calcium cause muscle contraction?
By binding to the proteins that normally block actin from interacting with myosin
What is ATP?
The molecular unit of energy that drives the actin-myosin crossbridge
What process breaks down ATP into adenosine diphosphate (ADP) to release energy stored within its phosphate bond?
ATP hydrolysis
What is the first of the 6 required steps for muscle contraction?
ATP binds to myosin’s head, causing it to release from actin
What is excitation-contraction coupling?
The process of a neural signal elevating calcium in order to cause muscle contraction
What is sarcoplasmic reticulum?
A network of tubules within muscle that stores and releases calcium
What are the 3 muscle functions?
Concentric action: when an activated muscle shortens
Eccentric action: when an activated muscle lengthens.
Isometric action: when an activated muscle remains in a static position.
What are muscle fibers always attempting to do? Describe the scenarios based on contraction type
Shorten, even if they lack the pulling force to do so.
A concentric action occurs when the pulling force a muscle generates is greater than the force applied by resistance in the opposite direction.
An eccentric action occurs when the pulling force is less than the resistance force
An isometric action occurs when the pulling force equals the opposing force
What is an agonist muscle or muscle group?
An agonist is the prime mover for a muscle or muscle group producing a movement. The biceps brachii is the agonist for elbow flexion.
What are the 3 main skeletal muscle fibers?
Type I slow-twitch fibers
Type IIa fast-twitch fibers
Type IIx fast-twitch fibers
What causes DOMS?
An exercise is performed for the first time or hasn’t been performed in weeks or months
There’s a significant increase in training intensity, such as adding 10 percent load compared to the previous workout
The volume of exercise significantly increases, such as doing six sets instead of three.
Can additional mitochondria can be created through training?
Yes, in a process called mitochondrial biogenesis
Who has a higher proportion of type 1 fibers?
Endurance athletes
Who has a higher proportion of type IIa fibers
Strength-power athletes
What muscle fiber type is most determined by genetics and and inactivity?
Type IIx fibers
What are the two types of hypertrophy?
Myofibrillar hypertrophy: growth of the myofibrils, which increases a muscle’s force potential.
Sarcoplasmic hypertrophy: an increase in volume of glycogen and semifluid plasma, which doesn’t increase a muscle’s force potential.
When does hypertrophy occur?
When muscle protein synthesis is higher than protein breakdown over the course of a day.
List the 3 theories for hypertrophy during resistance training
Mechanical tension: the mechanical stress within a muscle and its supporting tissues when it works against resistance
Metabolic stress: the buildup of lactate, protons (H+), and inorganic phosphates during exercise.
Muscle damage: damage to the muscle fibers in response to high-volume or intense exercise.
What is activated during hypertrophy?
A muscle’s satellite cells
Anterior or ventral
The front of the body relative to another reference point
Posterior or dorsal
The back of the body relative to another reference point
Superior
Above a reference point
Inferior
Below a reference point
Medial
a position relatively closer to the midline of the body
Lateral
A position relatively farther away from the midline
Proximal
a position closer to a reference point
Distal
a position farther from a reference point
Bilateral
Refers to both sides
Unilateral
Refers to only one side
Superficial
Near the surface
Deep
further beneath the surface
Cephalic
Toward the head
Caudal
Toward the bottom
Prone
lying facedown
Supine
lying on one’s backside
What are the 7 primary lines of fascia within the body?
Spiral Line Arm Lines Lateral Line Superficial Front Line Deep Front Line Superficial Back Line Functional Lines
What is responsible for sensing motion, body position, and effort?
Proprioception
-What is each muscle bundle called?
A fascicle
What is the perimysium?
The connective tissue support surrounding each fiber bundle within the muscle belly
What is each muscle fiber made up of?
Smaller myofibrils
What are the 3 types of muscles?
Cardiac muscle
Smooth muscle
Skeletal muscle
What role does skeletal muscle play in the body?
It’s the contractile tissue that produces voluntary and reflex action via force
What does calcium do in the cross-bridge cycle?
Allows the myosin head to attach to actin, which in turn shortens the sarcomere
What happens as sarcomeres shorten?
Myosin and actin slide past one another
What can trigger satellite cells to become active? What happens then?
Mechanical tension
Metabolic stress
Muscle damage
Once active, satellite cells donate their nuclei to the muscle fibers, causing them to grow.
What role do satellite cells play outside of hypertrophy?
Aid regulatory processes that facilitate repair, regeneration, and growth.
What’s the most likely cause of hypertrophy?
Mechanical tension likely the primary factor since hypertrophy often occurs without significant metabolic stress or damage to the muscle
What happens when the muscle stops receiving a signal from the brain?
Calcium is reabsorbed into the sarcoplasmic reticulum, which allows it to relax.
What are the two elements of muscle?
Contractile elements (myofibrils) Non-contractile elements (glycogen and semifluid plasma)
What is the antagonist muscle or muscle group?
An antagonist performs an action opposite that of an agonist. The triceps extends the elbow joint, making it the antagonist to the biceps brachii, which flexes the elbow.
What is a synergist muscle or muscle group?
Synergists work together during movement and provide assistance to the agonist. When curling a dumbbell with the right arm, the muscles that cross the wrist joint must work to hold the weight in a neutral position, while muscles that act on the shoulder apply force to stabilize the joint
What is not the cause of DOMS?
Lactate levels - they return to normal within one to two hours after training ends
What happens with calcium during the fight-or-flight response
It rapidly elevates in the muscle, allowing the muscle to contract with more force.
What are the characteristics of Type I slow-twitch muscle fibers?
Smallest
Produce the least force
Use for an activity that’s below an athlete’s lactate threshold, such as walking or jogging for 30 minutes.
What are the characteristics of type IIa fast-twitch fibers?
Medium-sized
Produce moderate to high amounts of force.
They work with type I fibers during an activity, such as climbing 10 flights of stairs or walking up a long hill.
What are the characteristics of type IIx fast-twitch fibers?
Largest
Produce the most force.
Short, quick bursts of high-intensity activity, such as a maximum vertical jump or heavy squat.
What is the most common shift in muscle fiber type?
Toward higher-endurance (type 1) characteristics
What are the common shifts in muscle fiber types?
Type IIx muscle fibers have been shown to shift to type IIa fibers
Type IIa can shift to type I
What is the difference between muscle fiber type by lower and upper body?
Lower body muscles have the highest percentage of type I fibers. The soleus muscle in the calf complex has been shown to be as high as 90 percent type I muscle fibers.
Upper body muscles have a higher percentage of type II fibers
What chemicals are pulled from the blood, taken into the muscle, and then to build muscle proteins?
Amino acids
What happens when muscles atrophy?
Atrophy occurs when protein breakdown is higher than protein synthesis.
Muscle proteins are broken down into amino acids and then released into the blood, where they’re used for other metabolic processes.
What is the second step in muscle contraction?
The myosin head moves from a cocked to an uncocked position via ATP hydrolysis
What is the 3rd step in muscle contraction?
Myosin and actin form weak cross-bridge attachment through ADP and phosphate attachment
What is the 4th step with muscle contraction?
Myosin releases phosphate from its head allowing it to form a stronger cross-bridge attachment with actin.
What’s the 5th step in muscle contraction?
Power stroke. The myosin recocks, which then pulls the Z lines closer together and shortens the sarcomere.
What’s the 6th and final step of muscle contraction?
ADP releases from the myosin head
Myosin will remain in a cocked position and bound to actin until another ATP attaches, which then starts the process over at Step 1
What chemical does myosin release when forming a strong cross-bridge attachment with actin?
Phosphate
What is responsible for elevating calcium in order to cause muscle contraction?
A neural signal
