Final Content

Question 1

What are the main functions of the motor system?

Answer 1

Planning, controlling, and executing voluntary movements; controlling involuntary functions like digestion.

Question 2

Is motor control a top-down or looped system?

Answer 2

It’s a looped system that integrates descending motor plans with sensory feedback.

Question 3

What spinal structures allow for basic motor control without brain input?

Answer 3

Reflex arcs and central pattern generators (CPGs).

Question 4

What brain regions plan and execute voluntary movement?

Answer 4

Motor cortex and premotor cortex.

Question 5

What structures modulate motor cortex activity for coordination and balance?

Answer 5

Basal ganglia and cerebellum.

Question 6

What type of neuron directly causes muscle contraction?

Answer 6

Alpha motor neurons (lower motor neurons).

Question 7

Where are alpha motor neuron cell bodies located?

Answer 7

In the ventral horn of the spinal cord.

Question 8

What is the topographic organization of motor neurons in the spinal cord called?

Answer 8

Somatotopic organization.

Question 9

Why are ventral horns enlarged in cervical and lumbar spinal regions?

Answer 9

They contain more motor neurons for arm and leg movement.

Question 10

What is the neuromuscular junction (NMJ)?

Answer 10

The synapse between an alpha motor neuron and a muscle fiber.

Question 11

What neurotransmitter is released at the NMJ?

Answer 11

Acetylcholine (ACh).

Question 12

What receptors does ACh bind to at the NMJ?

Answer 12

Nicotinic acetylcholine receptors (non-selective cation channels).

Question 13

What enzyme breaks down ACh at the NMJ?

Answer 13

Acetylcholinesterase.

Question 14

What causes muscle weakness in Myasthenia Gravis?

Answer 14

Autoimmune destruction of nicotinic ACh receptors at the NMJ.

Question 15

What is a motor unit?

Answer 15

One alpha motor neuron and all the muscle fibers it innervates.

Question 16

What is a motor pool?

Answer 16

All the motor units that innervate a single muscle.

Question 17

What are the three types of motor units?

Answer 17

Slow, fast fatigue-resistant, and fast fatigable.

Question 18

Which motor units are used for endurance activities?

Answer 18

Slow motor units.

Question 19

What is a muscle twitch?

Answer 19

A brief contraction following a single action potential.

Question 20

What is tetanus in muscle physiology?

Answer 20

Sustained muscle contraction due to rapid action potentials (unfused or fused).

Question 21

What determines graded muscle force?

Answer 21

Frequency of action potentials and motor unit recruitment.

Question 22

What order are motor units recruited in?

Answer 22

From smallest to largest based on force requirements.

Question 23

What are the three main sources of input to alpha motor neurons?

Answer 23

Sensory neurons (proprioception), upper motor neurons (from cortex/brainstem), and spinal interneurons.

Question 24

What is proprioception?

Answer 24

The sense of body position and movement.

Question 25

Through which pathway does proprioceptive information ascend to the brain?

Answer 25

The dorsal column-medial lemniscus tract.

Question 26

Which ion flows into the muscle fiber when acteylcholine acts on the nicotinic receptors? Sodium Potassium Chloride

Answer 26

Sodium

Question 27

Where are the cell bodies of the motor neurons located? Postjunctional folds Ventral horn Dorsal root ganglion

Answer 27

Ventral horn

Question 28

What neurotransmitter is released at the neuromuscular junction? Glutamate Glycine Acetlycholine Dopamine

Answer 28

Acetlycholine

Question 29

How is neurotransmitter action terminated at the neuromuscular junction? By acetycholinesterase By reuptake of acetylcholine by the presynaptic neuron

Answer 29

By acetycholinesterase

Question 30

Where is the cell body of sensory afferents located? Dorsal root ganglion Postjunctional folds Ventral horn

Answer 30

Dorsal root ganglion

Question 31

Why was Aplysia californica an advantageous model organism for studying learning and memory?

Answer 31

It has a simple nervous system (only ~20,000 neurons), large neurons (up to 1 mm in diameter), and simple, accessible anatomy, making it easier to conduct electrophysiological studies.

Question 32

What behavior did Eric Kandel and colleagues study in Aplysia californica to investigate memory?

Answer 32

The gill-withdrawal reflex, a defensive motor response to touch on the siphon.

Question 33

What neural circuit mediates the gill-withdrawal reflex in Aplysia?

Answer 33

Glutamatergic sensory neurons from the siphon synapse on motor neurons controlling the gill.

Question 34

What is habituation in the context of Aplysia’s gill-withdrawal reflex?

Answer 34

A decrease in response strength after repeated, non-threatening stimulation of the siphon, due to reduced glutamate release from the sensory neuron.

Question 35

During habituation, which part of the gill-withdrawal reflex circuit shows decreased activity?

Answer 35

The motor neuron; the sensory neuron’s activity remains the same.

Question 36

What is sensitization in Aplysia’s gill-withdrawal reflex?

Answer 36

An increased gill-withdrawal response following a noxious stimulus (e.g., tail shock) paired with siphon stimulation.

Question 37

Which neurotransmitter is key to the process of sensitization in Aplysia?

Answer 37

Serotonin, released by interneurons in response to tail shock.

Question 38

What is the molecular cascade triggered by serotonin in Aplysia sensitization?

Answer 38

Serotonin → increased adenylyl cyclase → increased cAMP → activation of protein kinase A → increased glutamate release from the sensory neuron.

Question 39

What long-term cellular change results from repeated sensitization in Aplysia?

Answer 39

Gene expression changes lead to synaptic plasticity, including growth of new axon terminals and increased synaptic connections.

Question 40

What is synaptic plasticity?

Answer 40

A change in synaptic strength that can be either an increase or decrease, lasting from minutes to a lifetime.

Question 41

What does LTP stand for and what does it mean?

Answer 41

Long-Term Potentiation; it’s a long-lasting increase in synaptic strength.

Question 42

What does LTD stand for and what does it mean?

Answer 42

Long-Term Depression; it’s a long-lasting decrease in synaptic strength.

Question 43

Can both excitatory and inhibitory synapses undergo LTP and LTD?

Answer 43

Yes, both types can experience either LTP or LTD.

Question 44

What is the primary input to the hippocampus and what pathway does it use?

Answer 44

The entorhinal cortex; it uses the perforant pathway.

Question 45

What cells do entorhinal cortex neurons synapse onto in the hippocampus?

Answer 45

Granule cells in the dentate gyrus.

Question 46

What are the axons from dentate gyrus granule cells called and where do they project?

Answer 46

Mossy fibers; they project to CA3 pyramidal neurons.

Question 47

What are Schaffer collaterals?

Answer 47

Axons from CA3 neurons projecting to CA1 neurons.

Question 48

How is LTP experimentally induced in the Schaffer collateral?

Answer 48

By delivering a high-frequency (100 Hz) tetanus to CA3 neurons and measuring EPSPs in CA1 neurons.

Question 49

What does an increased EPSP amplitude after stimulation indicate?

Answer 49

That LTP has occurred.

Question 50

How long can LTP last in rodents and potentially in humans?

Answer 50

Upwards of a year in rodents; possibly a lifetime in humans.

Question 51

What happens when glutamate binds to AMPA receptors?

Answer 51

The channel opens, allowing Na⁺ in and K⁺ out, causing depolarization.

Question 52

Why does NMDA require both glutamate binding and depolarization to open?

Answer 52

Because its pore is blocked by Mg²⁺ at resting potential, which is expelled upon depolarization.

Question 53

What causes the voltage change that unblocks NMDA receptors?

Answer 53

Na⁺ influx through AMPA receptors.

Question 54

What ions enter through open NMDA receptors?

Answer 54

Na⁺, K⁺, and Ca²⁺.

Question 55

What kinases are activated by calcium influx during LTP?

Answer 55

PKA, PKC, and CaMKII.

Question 56

What are two effects of kinase activation on AMPA receptors?

Answer 56

1. Phosphorylation increases their conductance. 2. Insertion of more AMPA receptors into the membrane.

Question 57

How is LTD induced in the Schaffer collateral?

Answer 57

By applying low-frequency (1 Hz) stimulation for ~15 minutes.

Question 58

What is the result of LTD on postsynaptic EPSPs?

Answer 58

A long-lasting decrease in EPSP amplitude.

Question 59

What does bidirectional plasticity mean?

Answer 59

Synapses can be strengthened (LTP) or weakened (LTD) depending on stimulation.

Question 60

Habituation of the gill-withdrawal reflex in Aplysia is due to: Decreased serotonin release from sensory neurons. Decreased glutamate release from sensory neurons. Increased glutamate release from sensory neurons. Increased serotonin release from sensory neurons.

Answer 60

Decreased glutamate release from sensory neurons.

Question 61

Sensitization of the gill-withdrawal reflex in Aplysia involves: Decreased sensory neuron axon growth. Decreased glutamate release. A weaker withdrawal reflex. Increased serotonin release.

Answer 61

Increased serotonin release.

Question 62

Eric Kandel and his colleagues used Aplysia californica to study learning and memory because: It exhibits a wide range of complex behaviors. It has a simple nervous system with large, easily studied neurons. It has a complex nervous system similar to humans. It is readily available in all parts of the world.

Answer 62

It has a simple nervous system with large, easily studied neurons.

Question 63

Long-lasting plastic changes in Aplysia, resulting from repeated sensitization protocols, involve: Activation of gene expression that results in the remodeling of the synapse. The suppression of gene expression that results in less axons. A decrease in the number of synaptic connections. A decrease in glutamate release.

Answer 63

Activation of gene expression that results in the remodeling of the synapse.

Question 64

What is synaptic plasticity? The degeneration of neural pathways. The ability of neurons to generate electrical impulses. The ability of synapses to change in strength. The process of forming new neurons.

Answer 64

The ability of synapses to change in strength.

Question 65

Which of the following statements about long-term potentiation (LTP) are true? 1. LTP is synonymous with long-term depression (LTD). 2. LTP occurs exclusively in inhibitory synapses. 3. LTP is a prolonged increase in synaptic strength. 4. LTP can persist for various durations, from minutes to a lifetime.

Answer 65

3. LTP is a prolonged increase in synaptic strength. 4. LTP can persist for various durations, from minutes to a lifetime.

Question 66

Long-term depression (LTD) is characterized by: (select all that apply) The immediate cessation of synaptic activity. An increase in synaptic strength. The formation of new synapses. A prolonged decrease in synaptic strength.

Answer 66

A prolonged decrease in synaptic strength.

Question 67

Long-term depression (LTD) at the synapses between CA3 and CA1 neurons can be induced by: A single, strong electrical pulse. Low-frequency stimulation for an extended period. Blocking AMPA receptor activity. High-frequency tetanus stimulation.

Answer 67

Low-frequency stimulation for an extended period.

Question 68

Which of the following statements are true about the role of NMDA receptors in synaptic plasticity? 1. They function independently of voltage changes in the postsynaptic neuron. 2. They block synaptic transmission to prevent excessive neural activity. 3. They require both presynaptic glutamate release and postsynaptic depolarization to open. 4. They allow calcium (Ca²⁺) influx when activated, triggering intracellular signaling for synaptic changes.

Answer 68

3. They require both presynaptic glutamate release and postsynaptic depolarization to open. 4. They allow calcium (Ca²⁺) influx when activated, triggering intracellular signaling for synaptic changes.

Question 69

Synaptic plasticity is essential for: Maintaining constant synaptic strength. Learning and memory formation. Preventing any changes in neural circuits. Immediate reflex actions.

Answer 69

Learning and memory formation.