Chapter 2 - Neuromuscular Fundamentals

What are muscles responsible for?

Movement of body and all joints

What does muscle contraction produce?

Forces that cause joint movement

What are other functions of muscle?

Protection, posture/support, and body heat

How many muscles are there and what percent of body weight are they?

600, 40-50%

How many pairs of skeletal muscle are there?

215

What is aggregate muscle action?

Muscles work in groups to achieve joint motion

How do muscles work in cooperation?

Perform opposite actions at the joints

How are muscles named?

Visual appearance, anatomical location, and function

What does shape and fiber arrangement affect?

Exertion of force and range of movement

What does a greater cross section diameter indicate?

Greater force exertion

What is the advantage of long muscles?

Able to shorten over a greater range and longer ranges of motion

What are the major types of fiber arrangement?

Parallel and Pennate

What are the types of parallel muscle arrangements?

Flat, fusiform, strap, radiate, sphincter/circular

Describe flat muscles:

Sheet like and can spread force over a broad area

What is an example of a flat muscle?

Rectus abdominus & external oblique

Describe fusiform muscles:

Central belly that tapers at ends and can focus power onto small bony targets

What is an example of a fusiform muscle?

Brachialis & biceps brachii

Describe strap muscles:

Uniform in diameter enabling focusing of power onto small bony targets

What is an example of a strap muscle?

Sartorius

Describe parallel muscles:

Triangular muscles that are a combination of flat and fusiform, can focus force in a large area

What is an example of a radiate muscle?

Pectoralis major & trapezius

Describe sphincter (circular) muscles:

Surround openings and close them upon contraction

What is an example of a sphincter (circular) muscle?

Orbicularis oris, orbicularis occuli

What are the benefits of parallel muscles?

Have longer fibers arranged parallel to tendon allows them to have more range of motion

What are the benefits of pennate muscles?

Have short fibers oblique to tendon which provides them with more power

Which fiber arrangement has a greater cross sectional area?

Pennate

What are the types of pennate fiber arrangement?

Unipennate, bipennate, and multipennate

Describe unipennate muscles:

Fibers run obliquely from a tendon on one side only

What is an example of a unipennate muscle?

Biceps femoris, tibialis posterior

Describe bipennate muscles:

Fibers run obliquely on both sides of a central tendon

What is an example of a bipennate muscle?

Rectus femoris, flexor hallucis longus

Describe multipennate muscles:

Have several tendons with fibers running diagonally between them

What is an example of a multippennate muscle?

Deltoid

Which pennate muscle fiber arrangements have the strongest contraction?

Bipennate and unipennate

What are the golden rules of skeletal muscle activity?

Cross at least one point, the bulk of muscle lies proximal to the crossed joint, has at least 2 attachments, can only pull, and insertion tries to move towards the origin

Describe what contraction is:

Active tension developed as a result of stimulus

What is a common misconception about contraction?

Muscles get shorter

Do all muscle contractions cause shortening?

No, some contractions cause lengthening and even no change

What can muscle contractions cause?

They can cause, control, or prevent joint movement

What are ways muscles cause movement?

They initiate or accelerate the movement of a body segment

What are ways muscles control movement?

They slow down or decelerate movement of a body segment

What are ways muscles prevent movement?

They can prevent movement caused by external forces

What are the two categories of muscle contraction?

Isometric and isotonic

What are isometric contractions?

Static contractions where joint angle remains constant

What is the relationship between muscle torque and resistance torque in isometric muscle action?

Muscle torque = resistance torque

What do isometric muscle actions do? 

Prevent motion, increase the diameter of muscle, and keep joint stable

What are isotonic muscle actions?

Dynamic contractions where joint angle changes that cause movement

What are the types of isotonic contractions?

Concentric and eccentric

Describe concentric muscle action:

Muscle shortens under active tension creating a POSITIVE contraction

What is the relationship between muscle torque and resistance torque in concentric muscle action?

Muscle torque > resistance torque

What direction does the joint change in relation to the muscle force in concentric muscle action?

Joint angle changes in the same direction as muscle action

What is the role of concentric muscle action?

Accelerate and cause body segment movement

Describe eccentric muscle action:

Muscle lengthens under active tension creating a NEGATIVE contraction

What is the relationship between muscle torque and resistance torque in eccentric muscle action?

Muscle torque < resistance torque

What direction does the joint change in relation to the muscle force in eccentric muscle action?

Joint angle changes in the opposite direction as muscle action

What is the role of eccentric muscle action?

Control and decelerate body segment movement

Which type of muscle action produced the most force in everyday movements?

Concentric muscle action

What are passive joint movements?

Movement at a joint without muscle contraction

What causes passive joint movements?

Force applies by another object, resistance, or gravity

What is cocontraction?

When both agonist and antagonist muscles contract

What are agonist muscles?

Muscle that causes joint motion when contracting concentrically

What are primary agonists?

The muscle most involved with a movement

What are assistant agonists?

Muscle that contributes to joint movement, but significantly less

What are antagonist muscles?

Located opposite of agonist muscles and work in cooperation by relaxing and allowing movement

What happens if an antagonist muscle contracts?

It performs the opposite motion of the agonist

What do stabilizers do?

Surround a body part and fixate the area to allow other movement

Where are stabilizers found?

They are found at the proximal end to allow distal movements

What is another word for stabilizer muscles?

Fixators

What are synergist muscles?

Assist agonists with refined movements and prevent undesired motiuons

What are the types of synergist muscles?

Helping synergists and true synergists

Describe helping synergists:

Have a common action with agonist but can be antagonistic

What do helping synergists do?

Help move a joint and prevent undesired actions

What is an example of a helping synergists?

Anterior and posterior deltoid work to accomplish abduction

Describe true synergists:

Have no direct effect on agonist action and prevent undesired joint action

What do true synergists do?

Stabilize joint so that agonist can have more effective movement

What are neutralizer muscles?

Contract to resist another muscle to prevent undesirable movements

What is an example of a neutralizer muscle?

During elbow flexion, the pronator teres prevents supination

How are synergists and neutralizers different?

Synergists aid movement and neutralizers prevent movement

What are force couples?

When 2 or more muscles that pull in different directions result in a rotational, controlled movement

What is an example of a force couple?

The muddle trapezius, serratus anterior, and lower trapezius

What happens when a muscle contracts?

It attempts to perform all actions at once

What factors impact what muscle actions occur?

Motor units activated, joint position, muscle length, and other muscles

What system is responsible for voluntary movement?

The neuromuscular system

What happens to the muscular system if the nervous system isn’t working?

Contraction is unable to occur

What are the levels of control in the CNS

Cerebral cortex, basal ganglia, cerebellum, brain stem, and spinal cord

What does the PNS contain?

All remaining nerves in the body

What is the role of the spinal cord?

The common pathway between CNS and PNS

Describe the spinal cord:

Has specific control, integrates reflexes, and integrates cortical and basal ganglia activity

What are the divisions of the PNS?

Sensory and motor divisions

Describe the sensory nerves

Bring impulses from receptors in skin, joints, and muscles to CNS

Describe motor nerves:

Carry impulses from CNS to outlying regions of the body

What is another word for sensory nerves?

Afferent nerves

What is another word for motor nerves?

Efferent nerves

What are the divisions of efferent nerves?

Voluntary and involuntary

Describe voluntary nerves and provide another name for them:

Under conscious control and carry impulses to skeletal muscles; somatic nerves

Describe involuntary nerves and provide another name for them:

Carry impulses to the heart, smooth muscles, and glands involuntarily; visceral nerves

What are neurons?

Nerve cells responsible for generating and transmitting impulses

What are the parts of a neuron you must know?

Neuron cell body, dendrites, and axon