AP exam 3

The functional unit of skeletal muscle

sarcomere

The globular protein that binds with calcium ions inside the sarcoplasm and is bound to tropomyosin

troponin

connective tissue covering each individual muscle cell(fiber)

endomysium

wave of depolarization that sweeps over a sarcolemma is known as

action potential

sarcolemma

muscle fiber plasma membrane

h zone

light region around m line

acetylcholine

neurotransmitter

motor end plate 

highly folded region of sarcolemma, forms muscle side of neuromuscular junction 

m line

connects thick filaments down center of sarcomere

a band

dense central region of sarcomere

sarcoplasmic reticulum

contains high calcium concentration

axon terminal 

helps form the nmj along with the motor end plate of a muscle 

stores calcium during skeletal muscle relaxation

sarcoplasmic reticulum

cardiac muscle

striated, uni-nucleated

smooth muscle

non-striated, uni-nucleated

skeletal muscle

striated, multi-nucleated

synaptic end bulb 

dilated end of an axon terminal 

T-tubules

periodic invaginations in the sarcolemma

synaptic cleft

space between the motor neuron and motor end plate

functions of skeletal muscle

posture,reservoir for amino acids, help maintain body temperature via shivering, control entrances and exits of the digestive and urinary systems, produce movements via tension and pulling on bones

what prompts the release of neurotransmitter at the NMJ?

the wave of depolarization reaching the axon terminals (synaptic end bulbs) allowing for voltage-gated calcium channels to open, allowing calcium into the neuron, and destabilizing the vesicles housing ACH to that they release it via exocytosis

Arrange structures from largest to smallest

skeletal muscle, fascicle, muscle cell (fiber) myofibril, myofilaments

Which of the following correctly describe smooth muscle relative to cardiac and skeletal muscle?

The organization of actin and myosin is different in smooth muscle as compared to skeletal and cardiac as they are striated. 

z disc (line)

boundary of a sarcomere formed from actin

I band 

area in muscle fiber containing only actin

a band

area of the sarcomere containing overlapping actin and myosin

myosin

thick

actin

thin

Tropomyosin

fibrous protein that hides the binding sites on Actin

I band (during contraction)

it shortens 

A band (during contraction)

it stays the same

During which phase of a muscle twitch does calcium (Ca++) bind to troponin and cause the formation of cross-bridges?

Contraction period

Which of the following occurs during the latent period of a muscle twitch?

Action potential propagates and Ca++ is released

Which of the following is true about the relaxation phase of muscle contraction? (Select all that apply)

Tropomyosin re-shields the binding sites on actin,

Muscle tension decreases,

Ca++ is actively pumped back into the SR

What protein interaction is primarily responsible for muscle contraction?

Actin and myosin

Which of the following are considered key roles of skeletal muscle?

Producing movement

Stabilizing joints

Generating heat

h zone (during contraction)

it disappears

z discs (during contraction)

move closer together

differentiate cardiac muscle from skeletal or smooth

having intercalated discs

myofilaments 

the proteins actin and myosin

muscle fiber

a muscle cell

Which of the following correctly describe smooth muscle relative to cardiac and skeletal muscle?

The organization of actin and myosin is different in smooth muscle as compared to skeletal and cardiac as they are striated. 

motor neuron and skeletal muscle cells innervated by said neurons axon terminal’s

motor unit

Step 1 (of muscle contraction)

The nerve action potential (electrical impulse) reaches the end of a neuron at a neuromuscular junction allowing the opening up of voltage-gated channels allow a calcium influx which then stimulates the release of Acetylcholine at the synaptic cleft

Step 2 (of muscle contraction)

The neurotransmitter Acetylcholine binds with chemically-gated channels on the muscle sarcolemma, resulting in the opening up of the gates and an influx of sodium, resulting in depolarization (the flipping of the original polarity of the muscle cell membrane).

Step 3 (of muscle contraction)

When depolarization reaches a critical level and voltage-gated channels on the sarcolemma open, there is a fast opening of channels allowing for more sodium influx, and the beginning of a slower opening for potassium channels.  The rapid influx of sodium ions allows for a wave of depolarization to sweep  the sarcolemma (muscle action potential) and down the t-tubules (transverse tubules). 

Step 4 (of muscle contraction)

The wave of depolarization reaching the sarcoplasmic reticulum opens voltage-gated channels to open, releasing stored calcium ions

Step 5 (of muscle contraction)

Calcium binds with troponin causing a conformational change = movement and subsequent movement of the protein Tropomyosin, which uncovers the binding site located on the action proteins.

Step 6 (of muscle contraction)

Energized Myosin heads bind with binding sites = cross bridge (and power stroke) = tension

Identify the correct organelle that is involved in releasing calcium ions

sarcoplasmic reticulum 

When considering skeletal muscle relaxation, which of the following is correct?

calcium is actively being pumped back into the sarcoplasmic reticulum

agonist

mover

synergist

assist agonist

antagonist

opposite of agonist

fixators

stabilize to allow movement 

Temporal, zygomatic, buccal,mandibular, cervical

cn7, all originate at skull, all insert skin ct

eye muscles: superior rectus, medial rectus, f rectus, inferior oblique

cn3

muscles of the eye

originate at skull, insert at sclera (white)

lateral rectus of eye

cn6

superior oblique

cn4

super hyoid muscles

open mouth, elevate hyoid bone, elevate larynx, protect airway during swallowing of food

infrahyoid muscles

depress hyoid, lower larynx, open up airway, food swallowed

boyle’s law

the law of inhalation that states, volume up then pressure down and vice versa

Posterior forearm muscles 

extension at the wrist of hand/fingers

anterior femoral compartment (muscles)

extension of knee

anterior forearm muscles

flexion at wrist or hand/fingers

posterior leg muscles

plantar flexion at ankle and flexion at toes

posterior femoral muscles (hamstrings)

flexion at knee and extension at hip

medial femoral compartment (muscles)

adduction at hip

erector spinae involved in

extension of vertebral column

popliteus

muscle that unlocks the knee; flexes the knee as well

rectus femoris

a quadriceps muscle; involved in flexion of the hip and extension of the knee

biceps femoris

hamstring muscle that contains two heads involved in flexion the knee ; the leg head also extends the hip

sartorius

the longest muscle in the body; involved in flexion of the hip and knee as well ad adduction and lateral rotation of the thigh

semitendinosus

hamstring muscle that flexes the knee and extends the hip

The muscles responsible for movement at the hand and wrist originate?

in the forearm and insert at the carpal area or at the phalanges

palmaris longus

flexor of the wrist; inserts into palmar aponeurosis

extensor digiti minimi

extends 5th digit at the metacarpophalangeal and interphalangeal joints

flexor pollicis longus

flexes thumb

extensor indicis

extends 2nd digits (index finger)

abductor pollicis longus

abducts and extends thumb at 1st carpometacarpal joint

extensor digitorum

extends the wrist and digits 2 -5 at the metacarophalangeal joints

flexor digitorum profundus

flexes distal phalangeal joints at digits 2 - 5

flexor carpi radialis

flexion and abduction of the wrist

Rotator Cuff Muscles 

they all insert into the greater or lesser tubercles of the humerus

they hold the head of the humerus in the glenoid cavity

brachialis

primary flexor of the elbow; insert into ulna

pronator quadratus

pronates the forearm

triceps brachii

extension at the elbow

brachioradialis

flexes forearm at elbow joint; inserts into radial bone

biceps brachii

flexion at elbow; supination of the forearm; flexion of the arm at the shoulder

The muscles that are responsible for movement at the forearm cross the elbow joint or are located within the forearm itself.

They are responsible for flexion, extension, supination, and pronation at the elbow and forearm. 

Piriformis

part of the lateral rotators at the hip

Mastication

The muscles all insert into the mandible,

they are all innervated by CN V (Trigeminal),

they include the masseter, medial and lateral pterygoids, temporalis muscles

The muscles responsible for movement at the hip and thigh originate?

at the pelvis and insert into the femur, a few inserts at the knee allowing flexion, extension, adduction, abduction, and rotation at the hip. 

medial hip compartment

muscles involved in adduction of the hip

iliopsoas

primary flexors at the hip

gluteus maximus

largest gluteal muscle involved in extension at the hip

gluteus medius

lateral rotator and medial rotation of the thigh; site of inter muscular injections

gluteus minimus

smallest of the gluteal muscles; involved in abduction and medial rotation of the thigh

adductor magnus

largest adductor; also involved in lateral rotation of the thigh