Module 7 - Axial Movement

accessory nerve

cranial nerve XI (eleven) extending from brain stem area to the neck muscles through jugular foramen

action potential

change in voltage of a cell membrane in response to a stimulus that results in transmission of an electrical signal; unique to neurons and muscle fibers

activation gate

part of the voltage-gated Na+ channel that opens when the membrane voltage reaches threshold

axon

single process of the neuron that carries an electrical signal (action potential) away from the cell body toward a target cell

axon hillock

tapering of the neuron cell body that gives rise to the axon

axon segment

single stretch of the axon insulated by myelin and bounded by nodes of Ranvier at either end (except for the first, which is after the initial segment, and the last, which is followed by the axon terminal)

axon terminal

end of the axon, where there are usually several branches extending toward the target cell

axoplasm

cytoplasm of an axon, which is different in composition than the cytoplasm of the neuronal cell body

dendrite

one of many branchlike processes that extends from the neuron cell body and functions as a contact for incoming signals (synapses) from other neurons or sensory cells

depolarization

change in a cell membrane potential from rest toward zero

external oblique

superficial abdominal muscle with fascicles that extend inferiorly and medially flattened bony process that extends laterally from the scapular spine to form the bony tip of the shoulder

facial nerve

cranial nerve VII (seven) extending from brain stem area to the facial muscles through stylomastoid foramen

foramen ovale of the middle cranial fossa

oval-shaped opening in the floor of the middle cranial fossa

hyperpolarization

while the K+ channels are open, membrane goes slightly over the resting potential

inactivation gate

part of a voltage-gated Na+ channel that closes when the membrane potential reaches +30 mV

insertion

end of a skeletal muscle that is attached to the structure (usually a bone) that is moved when the muscle contracts

internal oblique

flat, intermediate abdominal muscle with fascicles that run perpendicular to those of the external oblique

jugular foramen

irregularly shaped opening located in the lateral floor of the posterior cranial cavity

lateral pterygoid

muscle that moves the mandible from side to side

linea alba

white, fibrous band that runs along the midline of the trunk

masseter

main muscle for chewing that elevates the mandible to close the mouth

mastication

chewing

mastoid process

large bony prominence on the inferior, lateral skull, just behind the earlobe

membrane potential

distribution of charge across the cell membrane, based on the charges of ions

nerve

cord-like bundle of axons located in the peripheral nervous system that transmits sensory input and response output to and from the central nervous system

neuron

neural tissue cell that is primarily responsible for generating and propagating electrical signals into, within, and out of the nervous system

oblique

at an angle

orbicularis oculi

circular muscle that closes the eye

orbicularis oris

circular muscle that moves the lips

rectus abdominus

long, linear muscle that extends along the middle of the trunk

refractory period

time after the initiation of an action potential when another action potential cannot be generated

repolarization

return of the membrane potential to its normally negative voltage at the end of the action potential

resting membrane potential

the difference in voltage measured across a cell membrane under steady-state conditions, typically -70 mV

phrenic nerve

nerve is connected to the spinal cord at cervical levels 3 to 5 responsible for the muscle contractions that drive ventilation

spinal cord

organ of the central nervous system found within the vertebral cavity and connected with the periphery through spinal nerves; mediates reflex behaviors

splenius capitis

neck muscle that inserts into the head region

sternocleidomastoid

major muscle that laterally flexes and rotates the head

stylomastoid foramen

opening located on inferior skull, between the styloid process and mastoid process

styloid process

downward projecting, elongated bony process located on the inferior aspect of the skull

synapse

narrow junction across which a chemical signal passes from neuron to the next, initiating a new electrical signal in the target cell

synaptic cleft

small gap between cells in a chemical synapse where neurotransmitter diffuses from the presynaptic element to the postsynaptic element

temporalis

muscle that retracts the mandible

threshold

membrane voltage at which an action potential is initiated

transversus abdominis

muscle that compresses abdominal viscera

trigeminal nerve

cranial nerve V (five) extending from brain stem area to the jaw muscles through foramen ovale

voltage-gated channel

on channel that opens because of a change in the charge distributed across the membrane where it is located

zygomaticus major

muscle that draws upper lip upwards

the muscular system

makes up half of body weight (weighs more than any other organ system)

~700

how many muscles does the skeletal system contain

skeletal, cardiac, smooth

types of muscles

axial muscles

support the axial skeleton

appendicular muscles

support, move, brace limbs

tendons

conduct the forces of contraction to perform specific tasks

parallel fascicle organization

fibers parallel to one another and along the force-generating axis (ex. biceps brachii)

belly

central body of a parallel muscle

fascicle, belly (parallel)

arrow, bracket (type of muscle)

~30%

how much do parallel muscles shorten?

convergent muscles

fascicles that extend over broad area one one side and converge on common attachment site (tendon) (ex. pectoralis major)

versatility of convergent muscles

different parts can pull in different directions so does not pull as hard on attachment as parallel muscles

tendon, base (convergent)

arrow, bracket (type of muscle)

pennate muscle

at an angle from the tendon, do not move as far as parallel muscles, contain more myofibrils than parallel muscles, develop more tension than parallel muscles (ex. extensor digitorum, rectus femoris, deltoid)

unipennate muscle (ex. extensor digitorum)

1

bipennate muscle (ex. rectus femoris)

2

multipennate muscle (ex. deltoid muscle)

3

circular muscle

sphincters, fascicles in concentric circles, contraction decreases diameter of opening (ex. orbicularis oris)

origin

where the fixed end of a skeletal muscle attaches, usually proximal to insertion, mostly bones

action

specific movement produced by a skeletal muscle

agonist

the primary mover, muscle whose contraction is mostly responsible for producing a particular movement (ex. biceps brachii)

antagonist

muscle whose action opposes movement of a particular agonist (ex. triceps brachii), can have multiple per agonist

synergist

smaller muscle that helps a larger agonist work efficiently by providing additional pull or stabilization at the origin (ex. brachioradialis)

fixators

synergists that assist by preventing movement at another joint (ex. deltoid)

muscles of the head and neck

muscles of facial expression, extrinsic eye muscles, tongue, pharynx, neck

muscles of the vertebral column

muscles that stabilize, flex, extend, rotate vertebral column

oblique and rectus muscles of the trunk

broad sheets/bands forming muscular walls of thoracic and abdominopelvic cavities

muscles of the pelvic floor

span the pelvic outlet and support organs of he pelvis

orbicularis oculi

contraction closes eye

action of the orbicularis oculi

medial bones of the orbit (frontal, maxilla and lacrimal)

origin of the orbicularis oculi

circumference of the orbit

insertion of the orbicularis oculi

orbicularis oris

protrudes lips

action of the orbicularis oris

tissue of lips

origin of the orbicularis oris

under skin near corners of the mouth

insertion of the orbicularis oris

zygomaticus major

draws upper lip upward

action of the zygomaticus major

zygomatic bone

origin of the zygomaticus major

under skin near corners of the mouth

insertion of the zygomaticus major

masseter

elevation and protraction of the mandible

action of the masseter

zygomatic process of maxillae, anterior zygomatic arch

origin of the masseter

mandibular ramus

insertion of the masseter

temporalis

elevates mandible

action of the temporalis

temporal

origin of temporalis

mandible

insertion of the temporalis

lateral pterygoid

elevates mandible

action of the lateral pterygoid

pterygoid process of the sphenoid

origin of the lateral pterygoid

mandible

insertion of the lateral pterygoid

temporal branch of facial nerve

innervation of orbicularis oculi