Block 3: Muscular System - Lecture 3.4

Question 1

What side of the brain controls skeletal muscle on the right side of the body?

Answer 1

left side of the brain

Question 2

What side of the brain controls skeletal muscle on the left side of the body?

Answer 2

right side of the brain

Question 3

What are the locations that a signal travels in order to control cross bridge cycling?

Answer 3

1) Primary Motor Cortex
2) Upper Motor Neuron
3) Axon
4) Spinal Cord
5) Neuron
6) Lower Motor Neuron
7) Muscle Contraction

Question 4

What are the basic steps in muscle excitation to muscle contraction?

Answer 4

1) Electrical Signal from the Nervous System
2) Electrical Signal from a Muscle Cell
3) Calcium released from Sarcoplasmic Reticulum
4) Calcium binds to Troponin
5) Cross Bridge Cycling
6) Calcium goes back to Sarcoplasmic Reticulum

Question 5

When an electrical signal is sent from the nervous system during excitation and contraction, where is it transmitted?

Answer 5

transmitted down a motor neuron

Question 6

When an electrical signal is sent from a muscle cell during excitation and contraction, where is it transmitted?

Answer 6

transmitted and spread through muscle fibers

Question 7

What triggers calcium to be released from the Sarcoplasmic Reticulum during excitation and contraction?

Answer 7

triggered by an electrical charge

Question 8

When calcium binds to Troponin during excitation and contraction, what happens?

Answer 8

allows shape change of tropomyosin

Question 9

Where does calcium go after the Cross Bridge cycling is finished?

Answer 9

calcium goes back to the sarcoplasmic reticulum, where calcium is stored

Question 10

Because skeletal muscle contraction is voluntary, what does it require to make muscles move?

Answer 10

it requires a signal from the central nervous system

Question 11

Where are upper motor neurons located and what is their job?

Answer 11

• located in the brain
• allows for communication through the body

Question 12

Where are lower motor neurons located and what is their job?

Answer 12

• located in the spinal cord
• forms neuromuscular junction
• allows for communication through the body

Question 13

What are the three main parts of a motor neuron?

Answer 13

1) Cell Body (Soma)
2) Axon
3) Axon Terminal

Question 14

What is the job of an Axon in a motor neuron?

Answer 14

propagate info
a. aka carries electrical signals

Question 15

What is the job of an Axon Terminal in a motor neuron?

Answer 15

forms synapses with other cells
a. muscle fibers!

Question 16

What are the components of a Motor Unit?

Answer 16

1) Motor Neuron
a. one neuron can control one or many fibers
2) Fibers that it controls

Question 17

What are the steps to Neuromuscular Junction Excitation?

Answer 17

1) Action potential at the synaptic end bulb causes an opening of voltage calcium channels
2) Synaptic vessels that contain ACh undergo exocytosis
3) ACh is released into the synaptic cleft and binds to ACh receptors on the sarcolemma
4) ACh receptors open to allow sodium to enter, which generates an action potential
5) ACh is broken down to Acetate and Choline by AChE

Question 18

What are the steps to Excitation-Contraction Coupling?

Answer 18

1) Action potential runs along the sarcolemma and continues into T-tubules
2) Calcium is triggered released from sarcoplasmic reticulum
3) Calcium diffuses into sarcoplasm and myofibrils
4) Calcium binds to troponin on thin-filaments, allowing myosin binding sites to become exposed
5) Cross bridges form, tension is generated, and contraction begins

Question 19

How does the concentration gradient of calcium change when it is released from the sarcoplasmic reticulum?

Answer 19

travels down concentration gradient
a. increases calcium concentration in cytosol of muscle cells

Question 20

What protein allows calcium back into the sarcoplasmic reticulum during muscle relaxation?

Answer 20

calcium ATPase pumps through primary active transport

Question 21

What are the steps to Relaxation?

Answer 21

1) When action potentials stop arriving at the NMJ, the trigger to release calcium stops
2) Active calcium transporters in the sarcoplasmic reticulum membrane pump calcium back into the sarcoplasmic reticulum and the cytoplasmic calcium concentration decreases
3) Calcium comes off troponin and myosin binding sites on actin get covered by tropomyosin
4) Cross bridge cycling stops and muscle tension drops

Question 22

What is Titin’s role during muscle relaxation?

Answer 22

brings sarcomere back to resting position