Muscle Cells

Question 1

Name the 3 Muscle Types

Answer 1

• Skeletal
• Cardiac
• Smooth

Question 2

Myology

Answer 2

Study of skeletal muscles

Question 3

What are the 5 functions of Muscle?

Answer 3

Movement
Stability
Control body openings and passages
Heat productions
Glycemic control

Question 4

Properties of Muscle

What is Excitability?

Answer 4

Aka responsiveness, ability to react to stimuli

Question 5

Properties of Muscle

Conductivity

Answer 5

Ability of spreading electrical impulse through muscle

Question 6

Properties of Muscle

Contractility

Answer 6

Ability to shorten when stimulated

Question 7

Properties of Muscle

Extensiblity

Answer 7

Ability to stretch without harm

Question 8

Properties of Muscle

Elasticity

Answer 8

Ability to recoil from stretching

Question 9

Skeletal Muscle Tissue

Answer 9

• Striated, alternating light and dark bonds
• voluntary, decide to move
• attached to bone
• made up of myofiber/muscle fiber

Question 10

Cardiac Muscle Tissue

Answer 10

• Striated
• Involuntary movement
• Made up of cardiomyocyte

Question 11

Smooth Muscle Tissue

Answer 11

• Nonstriated
• Involuntary movement
• Fusiform cell shape (thick in center, tapered at ends)

Question 12

Sacrolemma

Answer 12

Plasma membrane of muscle fibers (outer layer)

Question 13

Transverse Tubules

Answer 13

Penatrates the sacrolemma

Sends electrical currents from outside stimuli to the inside of the sacrolemma

Question 14

Sacroplasm

Answer 14

Cytoplasm of the muscle cell

Contains:
- glycogen: storage of energy
- Myoglobin: binds to oxygen
- Myofibril: makes up bundles of muscle fibers

Question 15

Sarcoplasmic Reticulum

Answer 15

Stores and releases calcium for muscle contraction and relaxation

Contains Terminal Cisterns:
- stores and releases calcium when action potentials goes through transverse tubules, eliciting muscle contraction

Question 16

Thick Myofilaments

Answer 16

Made up of myosin protein

Heads project out from hundreds of myosin bundled together

Question 17

Thin Myofilaments

Answer 17

Made up of two layers of actin

Fibrous (F) actin: resembles necklace
Globular (G) actin: resembles one bead of necklace
- Active site: myosin binding area on G actin

Question 18

Elastic Myofilaments

Answer 18

Made up of titin protein

Anchors thick myofilaments

Question 19

Myofilaments

Functions of Tropomyosin and Troponin

Answer 19

Tropomyosin:
Blocks active sites when muscle is relaxed

Troponin:
Attaches to tropomyosin, binds calcium when excited

Question 20

Describe Skeletal Muscle Striations

Answer 20

Narrow light and dark strips perpendicular to cell
(A-band: Dark stripe
I-band: light stripe)

Question 21

Striations

A-Bands

Answer 21

Dark stripe of thick myofilaments (myosin) that partly overlap thin myofilaments (actin)

Question 22

Striations

H-Bands

Answer 22

Central region of A-Bands that only contain myosin

Question 23

Striations

M-Line

Answer 23

Midline of A-Band and H-Band

(holds thick myofilaments together)

Question 24

Striations

I-Bands

Answer 24

Light Stripe of thin and elastic myofilament (only F and G actin, no myosin)

Question 25

# Striations Z-Disc

Answer 25

Protein that anchors thin and elastic filaments Defines boundaries of a sarcomere (Z-Disc to Z-disc)

Question 26

# Striations Sarcomere

Answer 26

Made up of both actin and myosin (both responsible for muscular contraction) Basic unit of contractile muscle fiber

Question 27

Blood supply to Muscles during resting and heavy excerise

Answer 27

Resting: Muscle receives 1/4 supply of hearts blood output Heavy Excerise: Muscle receives 3/4 supply of hearts blood outputs

Question 28

Describe what happens at the Neuromuscular Junction: Synapse (aka point of communication)

Answer 28

1. Motor Neuron Synaptic knob contains vesticles containing ACh 2. ACh gets deposited by the motor neuron synaptic knob and goes through the synaptic cleft 3. Postsynaptic membrane folds of muscle cells contain ACh receptors 4. ACh binds to receptors that then trigger an action potential that sends info into the muscle

Question 29

Motor Units

Answer 29

One motor unit can control multiple muscle fibers (behaves as a single functional unit) Small amounts of motor units are used in fine motor control (ex. eyeball movement) Large amounts of moter units are used in larger muscle contraction (Ex. leg movement)

Question 30

What are large motor units associated with?

Answer 30

Strength

Question 31

What is ACh?

Answer 31

A neurotransmitter

Question 32

Describe a what a Neuromuscular Junction is

Answer 32

The site where the nerve fiber (axon terminal) connects with the muscle fiber (motor end plate)

Question 33

# Contraction and Relaxation Excitation: 1st Phase (1-3)

Answer 33

1. Nerve signal arrives at synapsis knob 2. Knob releases ACh, ACh bings to muscle receptors, ion gates open which excites muscle 3. Excitation spreads down and through muscle cell

Question 34

# Contraction and Relaxation Excitation - Contraction Coupling: 2nd Phase (4-8)

Answer 34

4. Electrical impulse triggers calcium realse from SR (Sacroplasmic Reticulum) 5. Calcium binds to troponin, which moves tropomyosin to expose actin 6. Myosin breaks down ATP and extends head 7. Myosin forms cross-bridge with actin 8. Myosin pulls actin in power stroke, then detaches, reattaches, pulls again, etc

Question 35

# Contraction and Relaxation Relaxation: 3rd Phase (9-10)

Answer 35

9. Nerve singal stops 10. SR (Sarcoplasmic Reticulum) reabsorbs calcium, troponin blockade resumes and tension subsides

Question 36

Slow Oxidative Muscle Fibers

Answer 36

- Slow twitch, Red, Type 1 fibers - Small diameter - Aerobic ATP production (oxygen required) - Abundent in Mitochondria, Myoglobin, Capillaries (gives the red color) - Low Levels of glycogen - Resistant to fatigue - Predominate in postural muscles