Nerves and Movement

Question 1

Define central nervous system.

Answer 1

The complex of nerve tissues that control the activities of the body. Comprised of the brain and spinal cord.

Question 2

Define peripheral nervous system.

Answer 2

Neuron system apart from brain and spinal cord. Carries signals from receptors to the spinal cord and brain. Motor neurons carry signals from the CNS to its effectors.

Question 3

Define dendrites.

Answer 3

Main apparatus for receiving signals from other cells.

Question 4

Define axon.

Answer 4

Main conducting unit of the neuron, across which the electrical signal is carried.

Question 5

Define myelin sheath.

Answer 5

Protects axon and prevents interference between axons as they pass along bundles. Makes conduction faster.

Question 6

Define node of ranvier.

Answer 6

Speeds up propagation of action potential and saves energy.

Question 7

Define axon terminals.

Answer 7

Facilitates conveying of electronic messages between neurons.

Question 8

Define saltatory conduction.

Answer 8

The nerve impulse jumping from one node of ranvier to the next.

Question 9

Define continuous conduction.

Answer 9

Conduction along the axon without jumping. Much slower than saltatory conduction.

Question 10

What is resting potential in neurons?

Answer 10

The electrical potential across the membrane of a neuron that is not conducting an impulse. Is used to repolarize a neuron inbetween impulses. It is negative in neurons.

Question 11

Explain the Na+/K+ pump in neurons.

Answer 11

3 Na+ ions are pumped out for every two K+ ions pumped in by active transport.

Question 12

When does the K+ channel open and in what direction are ions moving?

Answer 12

-Closed during depolarization -Open during repolarization, allowing K+ to diffuse out of the membrane, making membrane potential decrease before it is restored.

Question 13

When does the Na+ channel open and in what direction are ions moving?

Answer 13

-Opening leads to depolarization as Na+ diffuses across its concentration gradient into the neuron. This leads to reversing the charge imbalance across the membrane, making it positive.

Question 14

How is a resting potential maintained in a neuron? Why is it negative?

Answer 14

-Na+/K+ pump creates a charge imbalance by pumping out more Na+ than it pumps in K+. -Organic proteins in the membrane are also negatively charged.

Question 15

Define action potential.

Answer 15

Depolarization and repolarization of the neuron to conduct an electrical impulse.

Question 16

Outline an action potential, starting at the resting potential.

Answer 16

-Resting potential maintained through Na+/K+ pump -Depolarization is triggered by the arrival of an action potential. -Voltage-gated Na+ channels open if change in membrane potential rises above threshold. Charge imbalances switched as Na+ diffuse into the neuron. -Na+ diffusion triggers K+ channels to open, causing K+ to rush out of the neuron, causing repolarization.

Question 17

Resting potential: How is the internal potential? Where are the sodium ions? Where are the potassium ions? What membrane proteins are used?

Answer 17

-Internal potential is negative -Sodium ions are outside -Potassium ions are inside -Na+/K+ pump is used

Question 18

Action potential: How is the internal potential? Where are the sodium ions? Where are the potassium ions? What membrane proteins are used?

Answer 18

-Internal potential positive -Sodium ions inside -Potassium ions outside -Voltage-gated channels

Question 19

Define hyperpolarization.

Answer 19

When the neuron becomes more negative than its resting potential before returning to it.

Question 20

How is the one-way direction of a nerve impulse maintained?

Answer 20

-Na+ diffuse outwards and in the opposite direction of the pulse while Na+ inside the neuron diffuse along with the pulse.

Question 21

Outline the process of synaptic transmission.

Answer 21

-Nerve impulse reaches pre-synaptic membrane. -Depolarization of pre-synaptic membrane-> Ca2+ to diffuse into the neuron. -Influx of Ca2+ causes vesicles containing neurotransmitter to move to pre-synaptic neuron and then bind with it -Neurotransmitters released to synaptic cleft by exocytosis -Neurotransmitters diffuse across cleft and bind to receptors on post-synaptic membrane -Binding causes adjacent sodium channels to open, causing an action potential.

Question 22

What is acetylcholine?

Answer 22

Neurotransmitter used in synaptic transmission

Question 23

Explain the antagonistic nature of the action of muscles.

Answer 23

As one muscle contracts, the other releases, producing opposite movements at a joint.

Question 24

What are skeletal muscle fibres also called?

Answer 24

Striated muscle.

Question 25

Define sarcolemma.

Answer 25

Plasma membrane surrounding fibre,

Question 26

Define sarcoplasmic reticulum.

Answer 26

Modified version of endoplasmic reticulum, sending electrical signal down muscle

Question 27

What is the functional unit of the myofibril?

Answer 27

The sacromere.

Question 28

Describe the sliding filament theory of muscle contraction.

Answer 28

-During muscle contraction, myosin filaments pull the actin filaments inwards towards the center of the sarcomere, shortening the sarcomere and thus the whole muscle fibre -Myosin filament heads bind to actin filaments, creating cross-bridges through which they exert a force, causing the contraction.

Question 29

What role does Ca2+ have in controlling muscle contractions?

Answer 29

Released by sarcoplasmic reticulum when a muscle fibre receives a signal from a motor neuron. Bind to troponin, causing tropomyosin to move, thus exposing actin’s binding site.

Question 30

What role does tropomyosin have in controlling muscle contractions?

Answer 30

Blocks binding sites on actin

Question 31

What role does troponin have in controlling muscle contractions?

Answer 31

Causes tropomyosin to move

Question 32

Outline the contraction of skeletal muscle.

Answer 32

-Action potential initiated in muscle cell membrane. -Sarcoplasmic reticulum reacts to action potential by releasing Ca2+ ions. -ATP binds to myosin heads and causes them to break cross-bridges by detaching from the binding sites. -Hydrolysis of ATP to ADP and phosphate provides energy for heads to swivel outwards away from the center of the sarcomere -Energy stored in myosin head when it was cocked causes it to swivel inwards towards the center of the sarcomere, moving the actin filament a small distance. -Calcium ions pump back into the sarcoplasmic reticulum so the regulators protein moves and covers the binding sites on actin.

Question 33

What is the role of sinovial fluid in the joint?

Answer 33

Lubricates the joint.

Question 34

What is the role of cartilage in the joint?

Answer 34

Covers the bones and prevents friction.

Question 35

What is the role of the joint capsule?

Answer 35

Seals the joint and helps prevent dislocation.