Lecture 4: Skeletal Muscle and Nerve Tissue

Question 1

Simply put, how does contraction occur?

Answer 1

Actin (thin filaments) and myosin (thick filaments) slide past each other in myofibrils in the cytoplasm

Question 2

What is actin made of?

Answer 2

G-Actin Monomers

(globular protiens)

Question 3

What two chains does Myosin have?

Answer 3

Heavy chain with a globular head

Light chain

Question 4

How can you differentiate between skeletal, cardiac, and smooth muscle?

Answer 4

Skeletal: Striated and Voluntary

Cardiac: Striated and Involuntary

Smooth: Non-striated and Involuntary

Question 5

From smallest unit to largest, what are the divisions of a muscle?

Answer 5

Sarcomere -> Myofibrils -> Myocyte (Myofiber) -> Fascicle -> Muscle

Question 6

What connective tissue separates myofibers?

Answer 6

Endomysium

Question 7

What connective tissue separates fascicles?

Answer 7

Perimysium

Question 8

What fascial covering surrounds the entire muscle itself?

Answer 8

Epimysium

Question 9

What features can be used to identify Skeletal Muscle, especially in a histological slide?

Answer 9

Peripheral nucleii and Striations

Myofibers: Multinculeaded cylinders in the periphery of cell

Myofibrils: In the cytoplasm

Question 10

What is a sarcomere?

Answer 10

Basic structure of myofibril

Question 11

What serves as the defined border of a sarcomere?

Answer 11

Z disks

Question 12

What is the Sarcoplasm?

Answer 12

Cytoplasm of a Muscle Cell

Question 13

What is Sarcoplasmic Reticulum?

What is stored in there?

Answer 13

Tubular system which acts like smooth ER

-Calcium is stored

Question 14

What is the Sarcolemma?

Answer 14

The membrane around myocytes that penetrates the muscle cell as T tubules

Question 15

What are Transverse (T) Tubules?

Answer 15

Invaginations of sarcolemma

Question 16

What connects the Transverse Tubule to the Terminal Cisternae?

What do they do?

Answer 16

“End Feet”

Allow for calcium release

Question 17

What does the Terminal Cisternae do?

Answer 17

Dilated ends of Sarcoplasmic Reticulum that releases Calcium to trigger muscle contraction

Question 18

What is marked here as 1?

What does it contain?

Answer 18

I Band

-only actin thin filaments

Question 19

What is marked here as 2?

What is found here?

Answer 19

A Band

-Overlap of actin and myosin and H zone

Question 20

What is marked here as 3?

What is found here?

Answer 20

H Zone

-only myosin thick filaments

Question 21

What is marked here as 4?

What is found here?

Answer 21

M Line

-anchor site for myosin thick filaments

Question 22

What is marked here as 5?

What is found here?

Answer 22

Z Line

Anchor site for actin thin filaments

Question 23

What attaches to the Z disk?

Answer 23

Actin and Titin (which in turn holds myosin)

Question 24

What holds the Myosin to the Z disk, thus holding Myosin in place?

Answer 24

Titin protiens

Question 25

What all is contained within the H Zone?

Answer 25

Myosin fibers and the M line

Question 26

What is contained within the I band?

Answer 26

Actin The Z Disk (straddles sarcomeres)

Question 27

What is defined as the A band?

Answer 27

Distance from end to end of myosin within one sarcomere.

Question 28

Does the A Band shorten during contraction?

Answer 28

No. Only the H Zone and the I band shorten

Question 29

Where are myosin going one direction attached to the myosin going the other direction?

Answer 29

M line / M disc

Question 30

What two regions of a Myofibril shorten during muscle contraction?

Answer 30

The H Zone and the I Band

Question 31

What does Tropomyosin do?

Answer 31

Wraps between actin strands and holds troponin

Question 32

What keeps the muscles from contracting all the time?

Answer 32

Tropomyosin blocks the myosin binding sites

Question 33

What does Calcium do to incite muscle contraction?

Answer 33

It binds to Troponin, which then causes Tropomyosin to change conformation, and no longer block the Myosin binding sites on the Actin Filament

Question 34

What are the basic characteristics of **Type 1 muscle fibers**?

Answer 34

* Slow ATPases * Slow Contractions and low power (e.g. muscles in back) * Low fatigability * Many mitochondria and very aerobic * Abundant Myoglobin for O2 (gives red color)

Question 35

What is a **Type IIa Muscle Fiber**?

Answer 35

* Largest and most prevalent (seen in most of body) * Intertmediate ATPase that provides power * Primary aerobic

Question 36

What are the basic characteristics of **Type IIb Muscle Fibers**?

Answer 36

* Fast ATPase and largerly anaerbic * Rapid Fatigue * Low myoglobin content

Question 37

What are the major parts of a neuron?

Answer 37

* **Cell Body:** processes electrical information * **Cell Processes** * _Dendrites_: carries electrical signals *toward* cell body * Axons: carries electrical signals *away* from cell body * **Synapse:** Transfer of electric signals from axon terminal of one nerve to an effector cell

Question 38

What is the Nissl substance?

Answer 38

Rough ER that makes a lot of neurotransmitters and protein to maintain neurons

Question 39

What is the function of the Axon Hillock?

Answer 39

Sums up all of the action potentials from the dendrites, and sends a signal down the axon if it is sufficient.

Question 40

What is this type of neuron? How many dendrites and axons for this neuron?

Answer 40

**Multipolar Neuron** **-**Multiple dendrites, one axon

Question 41

What is this type of neuron? How many dendrites and axons for this neuron?

Answer 41

**Bipolar Neuron** -Single dendrite (with multiple extensions) and one axon

Question 42

What is this type of neuron? What are the characteristics of this neuron?

Answer 42

**Unipolar Neuron** A cell body connected to a cell process with a dendrite branch and an axon branch

Question 43

Do Schwann cells wrap around parts of single axons or many axons together?

Answer 43

Parts of a single axon in the PNS

Question 44

Do Oligodendrocytes wrap around parts of single axons or many axons together?

Answer 44

Many axons together in the CNS

Question 45

What connective tissue layer wraps a single myelinated or unmyelinated axon? ## Footnote *It is connective tissue between axons*

Answer 45

Endoneurium

Question 46

What connective tissue layer wraps a fascicle of nerve fibers together?

Answer 46

Perineurium

Question 47

What is the connective tissue layer surrounding the outside of the entire spinal nerve?

Answer 47

Epineurium

Question 48

In broad terms, how does the chemical synapse work?

Answer 48

**Step 1:** Synpatic vessels in the presynaptic knob release a NT into the synpatic cleft via exocytosis. **Step 2:** NT binds to a receptor on the postsynpatic membrane **Step 3:** Postsynpatic cell is now stimulated

Question 49

How does the neuromusclar junction work?

Answer 49

**Step 1****:** Acetylcholine is released into synaptic cleft **Step 2:** Acetylcholine stimulates sarcolemma and excites the muscle fiber. This stimulus is carried to T tubules to initiate contraction **Step 3:** Acetylcholine is broken down in synpatic cleft, ending its signal.

Question 50

What is an intrafusal muscle fiber? What are its two compartments?

Answer 50

Specialized fibers inside muscle spindle **Nuclear Bag Fibers:** Detect _change_ in length and degree of tension **Nuclear Chain Fibers:** Detect _static_ muscle length

Question 51

What is an extrafusal muscle fiber?

Answer 51

Muscle fiber outside muscle spindle under voluntary control, -In charge of contracting the muscle fibers

Question 52

What is the function of Alpha-Motor nerve fibers?

Answer 52

Sends the signal to contract to a muscle to extrafusal fibers

Question 53

Why is it important to have electrical impulses shuttled into the cell?

Answer 53

So that the myocyte can contract all at once, instead of from the outside in.