Lecture 20 - Animal Movement 1

Question 1

Neuronal Signaling: Receptor Cell (3)

Answer 1

Receptor cell receives signal, receptor cell depolarizes, receptor cell releases neurotransmitters

Question 2

Neuronal Signaling: Sensory Neuron (4)

Answer 2

Sensory neuron receives neurotransmitter from receptor cell, sensory neuron depolarizes, action potential propagated along axon of sensory neuron, sensory neuron releases neurotransmitters

Question 3

Neuronal signaling: Interneuron (4)

Answer 3

Interneuron receives neurotransmitters, interneuron depolarizes, action potential propagated along axon of interneuron, interneuron receives neurotransmitters

Question 4

Neuronal signaling: motor neuron (3)

Answer 4

Motor neuron receives neurotransmitters, motor neuron depolarizes, action potential propagated along axon of motor neuron causing muscles to contract

Question 5

How do muscles appear when they are contracted?

Answer 5

Larger

Question 6

Early Hypotheses for muscle contraction

Answer 6

Galen- 2nd Century Roman Physician: Spirits enter muscles from nerves

Rene Descartes - 17th century French philosopher: Fluids from the pineal gland of the brain inflate muscles

Jan Swammerdam - 17th century Dutch anatomist: Muscles do not change volume during contraction (true after experiment done when bubble didn’t move after muscle contraction)

Luigi Galvani - 18th century Italian scientist: discover bioelectricity, proved that electricity causes muscles to contract by stimulating the sciatic nerve to make legs move

Giovanni Aldini - 19th century Italian scientist (nephew of Galvini): reanimated the corpse of convicted murderer George Foster in 1803, caused the eyes and face and other muscles to be contorted and move etc.

Question 7

Muscles

Answer 7

Bundles of muscle fibers

Question 8

Muscle fiber

Answer 8

A single cell composed of several myofibrils

Question 9

Myofibrils

Answer 9

Composed of many sacromeres

Question 10

What is a sacromere?

Answer 10

Part of a myofibril, it is composed of two 2 light bands and a dark band

Question 11

What happens to the sarcomere when the muscle contracts?

Answer 11

The sarcomere shortens

Question 12

What happens to the sarcomere when the muscle relaxes?

Answer 12

The sacromere lengthens

Question 13

What happens to the sarcomere when the muscle relaxes?

Answer 13

The sarcomere lengthens

Question 14

What proteins is a sarcomere composed of?

Answer 14

Actin and myosin

Question 15

Actin

Answer 15

The structural protein that the thin filament is composed of

Question 16

Myosin

Answer 16

The motor protein that the thick filament is composed of

Question 17

The sliding filament model (3)

Answer 17

The muscle contracts, myosin heads move toward the Z disk, the Z disks are pulled closer together

Question 18

How do actin and myosin interact? (6)

Answer 18

Myosin heads bind to actin and catalyzes the hydrolysis of ATP, myosin head is bound to actin subunit. ATP binds to head, then myosin head detaches, after which ATP is hydrolyzed to ADP. The head then binds to the next actin subunit. The energized head is now “cocked”. Pi is released, and then the head pivots and moves the thin filament (power stroke). ADP is then released, and the cycle is ready to repeat itself.

Question 19

What happens when the muscle is relaxed?

Answer 19

Tropomyosin and troponin block myosin binding sites on actin

Question 20

What happens when muscle contraction begins? (3)

Answer 20

Calcium ions bind to troponin, troponin-tropomyosin complex moves, the myosin binding sites are exposed

Question 21

Sarcoplasmic reticulum

Answer 21

Sheets of smooth endoplasmic reticulum in a muscle cell

Question 22

How do neurons initiate contraction? (80

Answer 22

An action potential arrives at the end of the motor neuron’s axon, neurotransmitter acetylcholine is released, acetylcholine binds to acetylcholine receptors on the muscle cell, muscle cell depolarizes, action potential fires in the muscle cell, action potential propogates along the T tubule which is an invagination of the muscle cell membrane, Ca2+ channels open in the sarcoplasmic reticulum, Ca2+ causes the myosin binding sites on the actin filament to be exposed which enables contraction to begin