Movement (Test Two)

Question 1

What does animal movement rely on?

Answer 1

The fundamental mechanism called contractile proteins.

Question 2

What is the most important protein contractile system composed of?

Answer 2

Actin and Myosin

Question 3

Briefly explain what actin is.

Answer 3

Spherical protein that forms filaments (strands) that are involved in the cytoskeleton and muscle contraction.

Question 4

Briefly explain what myosin is.

Answer 4

A motor protein that is involved in muscle contraction by converting ATP into mechanical energy

Question 5

In what organisms does ameboid movement occur?

Answer 5

1. Macrophages
2. ameboid/unicellular
3. WBC
4. some embryonic cells
5. some cancer cells

Question 6

How do ameboid cells change shape?

Answer 6

By extending and withdrawing pseudopodia (false feet)

Question 7

How do ameboid cells move?

Answer 7

By assembling and disassembling actin and myosin filaments, the cell membrane is pushed forward, and the cytoplasm follows.

Question 8

What are cilia and what are their functions?

Answer 8

They are tiny, hairlike processes that extend from surfaces of many animal cells, that do not use actin or myosin

Functions:

1. To move whole unicellular organisms and some cnidarians in water
2. Also used to propel fluids and materials across epithelial surfaces in larger animals.

Question 9

What are flagella?

Answer 9

Flagellum are whip-like structures (longer than cilia) that are usually used for locomotion or movement of things

They also do not use actin or myosin

Question 10

What is the difference between Ciliary and Flagellar movement?

Answer 10

1. Flagella beat symmetrically, and water is propelled parallel to its length like a propeller (sideways movement)
2. Cilia have a fast power stroke down and slow recovery, like oars (upward movement)

Question 11

Nearly all movement in animal bodies is the result of what?

Answer 11

Muscle cell (fibers) contractions

Question 12

Describe skeletal muscle.

Answer 12

Striated muscles that are transversely striped with alternating dark and light bands (striations) and are multi nucleated.

They are long cylindrical cells that are packed together in bundles called fascicles and enclosed by tough connective tissue.

Question 13

What is the purpose of skeletal muscle?

Answer 13

They are attached to skeletal elements that move the trunk, appendages, eyes, respiratory organs and mouthparts.

Question 14

What does skeletal muscle do at the ends when it connects to bones via tendons?

Answer 14

It reduces thickness (tapers)

Question 15

What does skeletal muscle look like in abdominal muscles?

Answer 15

They look like flattened sheets.

Question 16

How are skeletal muscles stimulated? Are they voluntary?

Answer 16

They are stimulated by motor fibers under conscious control.

Question 17

Describe Cardiac Muscle.

Answer 17

1. Fast acting, with similar contraction mechanism to skeletal muscle, but has involuntary control.

Question 18

Where does the heat beat originate?

Answer 18

Within a specialized cardiac muscle, and can continue to beat outside the body

Question 19

Describe Smooth Muscle.

Answer 19

Smooth (visceral) muscle lacks striations and the cells are much smaller, tapering at both ends, with a single central nucleus.

Question 20

Where is smooth muscle located?

Answer 20

Smooth muscle forms sheets of muscle to circle the walls of tubes, ducts and passages.

Question 21

Is smooth muscle slow acting or fast acting?

Is it under voluntary control?

Answer 21

1. Smooth muscle is slow acting and uses little energy.
2. Smooth muscle is under involuntary control

Question 22

What is the functional unit of skeletal muscle?

Answer 22

Sarcomere

Question 23

Describe sarcomeres in more detail.

Answer 23

Sarcomeres span protein complexes called z-lines and are primarily.

Question 24

Explain the structure of myosin.

Answer 24

1. Myosin Filament is composed of myosin molecules packed in a bundle
2. Each myosin molecule consists of two polypeptide chains, each with a club shaped region
3. The double heads face outward from the center of the filament, and point towards the z-line
4. The heads act as binding sites for ATP and interact with the myosin filaments during muscle contraction

Question 25

Explain the structure of Actin.

Answer 25

1. The actin filaments are made of a backbone of double stranded actin twisted into a double helix.
2. The double helix has two actin-binding proteins called tropomyosin and troponin which cover the myosin binding sites when the muscle is at rest.
3. The actin filament complexes extend outward from both sides of the z-line and overlap the myosin bundles

Question 26

Explain how contraction works.

Answer 26

1. The club shaped heads of the myosin filaments attach and release from the actin filaments
2. This ratcheting action draws the actin past the myosin and pulls the z-line together.
3. When the muscle contracts, all the sarcomere units shorten
4. When the connections between the filaments release, the sarcomeres lengthen

Question 27

How is muscle contraction controlled?

Answer 27

Muscle cells contract in response to nerve control and stimulation.

1. Skeletal muscles are innervated by motor neurons whose cell bodies are located in the CNS (brain and spinal cord)
2. Each cell body leads to a motor axon that leaves the brain and spinal cord and branches to terminal points on a muscle.

Question 28

What is the neuromuscular junction?

Answer 28

The neuromuscular junction is the place where the motor axon ends on (not touching) the muscle fiber.

Question 29

What separates the nerve ending from the muscle fiber?

Answer 29

The synaptic cleft (space)

Question 30

Explain the process of a nerve signal causing a muscle contraction.

Answer 30

1. The neuron stores acetylcholine in small synaptic vesicles near the cleft.
2. When the signal or action potential reaches the synapse, the acetylcholine is released and acts as a chemical neurotransmitter
3. Acetylcholine binds to receptor sites on the muscle fibers which release calcium
4. Calcium enables contraction by exposing the myosin binding sites on actin filaments