Week 3

Question 1

Types of Muscle

Answer 1

Skeletal
-multinucleated, cylindrical, striated, voluntary
Cardiac
-Cells are smaller and branched, striated, involuntary
Smooth
-Cells are tapered, nucleus on the periphery, not striated, involuntary

Question 2

A motor neuron synapses with skeletal muscle at the_______________

Answer 2

Neuromuscular junction (NMJ)

Question 3

Neuron releases _____________ which binds to ______________, causes depolarization.

Answer 3

ACh, nicotinic receptors

Question 4

Motor Unit

Answer 4

Individual motor neuron and all of the muscle fibers it innervates

Question 5

Small motor unit

Answer 5

neuron innervates few muscle fibers

Provides precise control of very fine movements (eyes, fingers)

Question 6

Large motor unit

Answer 6

• neuron innervates many muscle fibers

- useful for contraction of muscles in the leg, maintaining posture

Question 7

Muscle fibers are surrounded by a layer called the ________________

Answer 7

Endomysium

Question 8

Muscle fibers are arranged in _____________ surrounded by a _____________

Answer 8

Fascicles, perimysium

Question 9

Tendons are an extension of the ____________ that surrounds the muscle

Answer 9

Epimysium

Question 10

Reflex actions

Answer 10

involuntary movements controlled in spinal cord

Question 11

Volitional actions

Answer 11

complex voluntary activities, organized in motor areas in cerebral cortex

Question 12

Final common pathway is the …

Answer 12

Alpha motor neuron

Question 13

Where does the alpha motor neuron originate and exit?

Answer 13

Originates in ventral horn of the spinal cord, exits through ventral root

Question 14

What do alpha motor neurons innervate?

Answer 14

Skeletal muscle

Question 15

Skeletal muscle contractions results in…

Answer 15

Movement

Tension development to stabilize the body

Question 16

Muscle cells =

Answer 16

FIBERS. A “muscle” is many fibers in parallel

Question 17

Two types of skeletal muscle fibers

Answer 17

Extrafusal

Intrafusal

Question 18

Extrafusal muscle fibers

Answer 18

strongest, most common, usually attached to tendons at either end

Question 19

Intrafusal muscle fibers

Answer 19

tension-sensing fibers. Sensory neurons are located here

Question 20

How are skeletal muscles classified?

Answer 20

based on metabolism and speed of contraction

Question 21

Slow Twitch Fibers

Answer 21

• Red muscle
• produce slow, sustained contractions
• require aerobic metabolism to generate ATP for contraction. Thus, need a constant supply of oxygen
• Use molecules called MYOGLOBIN to store oxygen. Myoglobin has a dark pigment
• Used for long duration activities such as maintaining posture. Slow to fatigue

Question 22

Fast Twitch Fibers

Answer 22

• White muscle
• Produce fast, short-duration contractions
• Rely on anaerobic metabolism supplied by GLYCOGEN, which is stored in muscle (and liver)
• Fire fast, but fatigue quickly
• Used for rapid, finely controlled movement or short bursts of energy

Question 23

Distribution of types of muscle fibers is ….

Answer 23

Genetic. Specific types of training can develop one set of fibers more than the other

Question 24

Sensory Neurons

Answer 24

have processes in muscle. Transmit info about state of contraction and tension

Question 25

Two types of sensory neurons

Answer 25

Muscle Spindles Golgi Tendon Organs -Both types of sensory neurons transmit info to somatosensory cortex for integration or to spinal cord for reflex

Question 26

Muscle spindles

Answer 26

innervate intrafusal fibers, act as stretch receptors. When intrafusal muscle cells stretch, muscle spindle increases its discharge of APs. LENGTH

Question 27

Golgi tendon organs

Answer 27

Innervate extrafusal fibers near the tendons, generate more APs as fibers develop tension. FORCE

Question 28

Muscle cell or fiber =

Answer 28

myocyte

Question 29

plasma membrane =

Answer 29

sarcolemma

Question 30

Striations in muscle (alternating dark and light bands) result from...

Answer 30

two types of myofilaments: ACTIN (thin) and MYOSIN (thick)

Question 31

Sarcomere

Answer 31

functional unit of muscle.

Question 32

A-band

Answer 32

at the center of the sarcomere. Dark band containing myosin

Question 33

I-band

Answer 33

light band at ends of sarcomere, contains actin

Question 34

M-line

Answer 34

in sarcomere. Holds myosin filaments in place

Question 35

Z-discs

Answer 35

Edges of sarcomere comprised of Z-discs, which connect ends of actin from one sarcomere to the next

Question 36

functional unit of muscle

Answer 36

sarcomere

Question 37

myofilaments are surrounded by ___________ which stores __________

Answer 37

sarcoplasmic reticulum, Ca2+

Question 38

Embedded in the sarcoplasmic reticulum are ____________ which are invaginations of plasma membrane

Answer 38

T-Tubules

Question 39

AP travels down the muscle fiber, transverses into the ______________ on the SR, voltage gated ________ channels on SR open, ___________ binds to myofilaments, causing muscle contraction

Answer 39

Tubules, Ca2+, Ca2+

Question 40

actin

Answer 40

two actin filaments are wrapped around each other

Question 41

Tropomyosin

Answer 41

actin is associated with long fibrous proteins called tropomyosin. Each tropomyosin molecule is associated with a protein complex called troponin.

Question 42

Troponin

Answer 42

protein complex associated with tropomyosin

Question 43

T-T complex

Answer 43

together, tropomyosin and troponin form a regulatory protein complex called the T-T complex

Question 44

Myosin

Answer 44

each thick filament is comprised of 300 - 400 myosin molecules wrapped together. - each myosin contains a long rod-shaped tail and head - the head contains binding sites for actin and ATP - The head region is associated with myosin "LIGHT CHAINS" - Head regions project from the sides of the filament and form CROSS-BRIDGES during muscle contraction

Question 45

How are action potentials created on the muscle fiber?

Answer 45

- NMJ consists of the motor axon terminal, the MOTOR END PLATE of the muscle fiber, and the synaptic cleft that separates the two - AP travels down the motor neuron, triggering voltage-gated Ca2+ channels to open. Ca2+ enters neuron, causes exocytosis of ACh-containing vesicles into synaptic cleft - ACh binds to nicotinic receptors on motor end plate. Na+ enters muscle fiber, depolarizes membrane, creates an AP

Question 46

Role of the T-tubule in muscle contraction

Answer 46

AP travels along the sarcolemma and follows down T-tubules toward center of cell. This special conduction allows innermost portion of cell to receive AP quickly. Note that muscle fibers are not myelinated

Question 47

Role of the SR (sarcoplasmic reticulum)

Answer 47

- Stores calcium in sac-like areas called TERMINAL CISTERNAE - RYANODINE RECEPTOR (RyR) controls realease of calcium from SR. In skeletal muscle, RyR1 acts as a voltage-gated calcium channel. When open, calcium is released and travels to myofilaments. This causes muscle contraction. - After contraction, intracellular calcium is stored in the SR using an ATP-dependent calcium pump. - Release and storage of calcium occurs quickly, allowing muscle contraction to occur up to 100x/second.

Question 48

Sliding Filament Theory

Answer 48

1. Action potential (AP) 2. AP travels through T-tubules 3. Release of calcium from SR 4. Calcium binds to troponin 5. Conformational shift in actin to expose binding sites 6. Myosin heads bind to actin 7. Power stroke (contraction)