Lectures 71 and 72 muscle excitation

Question 1

Skeletal muscle fibers are the result of fusion of several

Answer 1

mononucleated undifferentiated myoblast cells

Question 2

Each skeletal muscle fiber contains one or many nuclei?

Answer 2

many

Question 3

Motor neurons that innervate skeletal muscle originate in what horn?

Answer 3

ventricular/anterior

Question 4

What is the sarcolemma?

Answer 4

the skeletal muscle cell membrane

Question 5

Which filaments are “thick”?

Answer 5

myosin

Question 6

I-bands, or light bands, contain only

Answer 6

actin

Question 7

Overlapping ends of actin filaments are called

Answer 7

A-bands

Question 8

What gives skeletal muscle its striated appearance?

Answer 8

actin and myosin bands

Question 9

What are the sites of interaction between thick and thin filaments that generate force and contraction?

Answer 9

cross bridges - projections from the sides of myosin filaments

Question 10

The Z line/disc is composed of

Answer 10

filamentous proteins - the non-overlapping ends of actin filaments are attached to these

Question 11

What is titin?

Answer 11

a large protein that acts as a framework holding filaments in place

Question 12

The tail of a myosin molecule is composed of 2 “heavy” chains that

Answer 12

spiral to form a double helix like DNA

Question 13

The myosin molecule tails bundle together to form

Answer 13

the body of the myosin filament

Question 14

What two things are essential for myosin heads to contract?

Answer 14

ATP and calcium

Question 15

What is the initiator of contraction?

Answer 15

troponin

Question 16

Troponin I has an affinity for

Answer 16

actin

Question 17

Troponin T has an affinity for

Answer 17

tropomyosin

Question 18

Troponin C has an affinity for

Answer 18

calcium

Question 19

What are the two types of NMJ blocking agents?

Answer 19

nAChR antagonists (non-depolarizing) and agonists not removed efficiently

Question 20

What are the two main classes of smooth muscle?

Answer 20

multi-unit and unitary

Question 21

Multi-unit smooth muscle works in what way?

Answer 21

the fibers it is composed of work separately with single specific nerve innervation

Question 22

T or F: unitary smooth muscle contracts as a whole

Answer 22

true

Question 23

Does smooth muscle contain tropomyosin or troponin?

Answer 23

no

Question 24

In smooth muscle, calcium binds to

Answer 24

calmadoulin

Question 25

What does calmadoulin activate?

Answer 25

myosin light-chain kinase; this phosphorylates myosin heads which cycle and shorten

Question 26

In smooth muscle, myosin filaments are connected to what instead of z-discs?

Answer 26

dense bodies