Study Guidance for Nerve, Muscle, and Major Muscle Anatomy (ANP)

Q1. Describe the basic structure of a neuron; include nucleus, cell body, Nissl Bodies, axon, dendrites, synaptic knobs and synaptic vesicles.

Background

Topic: Neuron Structure

This question tests your understanding of the anatomy of a neuron and the function of its main components.

Key Terms:

• Nucleus: The control center of the neuron, containing genetic material.

• Cell Body (Soma): Contains the nucleus and organelles; metabolic center.

• Nissl Bodies: Rough endoplasmic reticulum involved in protein synthesis.

• Axon: Long process that transmits impulses away from the cell body.

• Dendrites: Branch-like extensions that receive signals from other neurons.

• Synaptic Knobs: Swellings at the end of axons that contain synaptic vesicles.

• Synaptic Vesicles: Membrane-bound sacs containing neurotransmitters.

Step-by-Step Guidance

1. Start by drawing or visualizing a typical neuron. Identify the cell body (soma) at the center.

2. Locate the nucleus within the cell body. Remember, this is where the neuron's DNA is stored.

3. Identify the Nissl bodies in the cytoplasm of the soma. These are responsible for synthesizing proteins needed for neuron function.

4. Find the dendrites extending from the cell body. These structures receive incoming signals from other neurons.

5. Trace the axon, which is a single, long projection that carries impulses away from the cell body toward other cells.

6. At the end of the axon, locate the synaptic knobs (axon terminals). These contain synaptic vesicles filled with neurotransmitters.

Try drawing and labeling a neuron diagram to reinforce your understanding before checking the answer!

Q2. Describe the basis for the resting membrane potential of nerve and muscle cells; include the role of K+, Na+, proteins, the Na-K pump, etc.

Background

Topic: Resting Membrane Potential

This question examines your knowledge of how the resting membrane potential is established and maintained in excitable cells.

Key Terms and Concepts:

• K+ (Potassium): Major intracellular cation.

• Na+ (Sodium): Major extracellular cation.

• Proteins: Negatively charged molecules inside the cell.

• Na-K Pump: Active transport protein that moves 3 Na+ out and 2 K+ in per ATP hydrolyzed.

Key Formula:

$E_{m} = \frac{RT}{F} \ln \left( \frac{[K^+]_{out}}{[K^+]_{in}} \right)$ (Nernst equation for K+)

Step-by-Step Guidance

1. Recall that the resting membrane potential is the voltage difference across the cell membrane when the cell is at rest.

2. Understand that K+ ions tend to diffuse out of the cell, while Na+ ions tend to diffuse in, but the membrane is more permeable to K+.

3. Recognize that negatively charged proteins inside the cell contribute to the negative charge within the cell.

4. The Na-K pump actively transports 3 Na+ out and 2 K+ in, maintaining the concentration gradients and contributing to the negative resting potential.

Try explaining the role of each ion and the pump in your own words before checking the answer!

Q3. Understand the principle steps behind the operation of a metabotropic effect and recognize that the bulk of this topic will be addressed in A&P II.

Background

Topic: Metabotropic Receptors

This question introduces you to the concept of metabotropic effects, which involve G-protein coupled receptors and second messenger systems.

Key Terms:

• Metabotropic Effect: A slower, longer-lasting effect on the postsynaptic cell mediated by second messengers.

• G-Protein Coupled Receptor (GPCR): A receptor that activates intracellular signaling cascades.

• Second Messenger: Intracellular molecules (e.g., cAMP) that propagate the signal.

Step-by-Step Guidance

1. Recognize that metabotropic receptors are not ion channels but activate G-proteins when a neurotransmitter binds.

2. Understand that the G-protein then activates or inhibits enzymes, leading to the production of second messengers.

3. These second messengers can open or close ion channels or alter cell metabolism, leading to a slower but longer-lasting effect.

Try summarizing the difference between ionotropic and metabotropic effects before checking the answer!

Q4. Describe the physiology of nerve and muscle impulses (action potential); include resting potential, threshold stimulus, subthreshold stimulus, action potential, depolarization, repolarization, refractory period, and the "all or none" principle.

Background

Topic: Action Potentials

This question tests your understanding of how action potentials are generated and propagated in nerve and muscle cells.

Key Terms:

• Resting Potential: Baseline membrane voltage.

• Threshold Stimulus: Minimum stimulus needed to trigger an action potential.

• Subthreshold Stimulus: Stimulus too weak to trigger an action potential.

• Depolarization: Membrane potential becomes less negative.

• Repolarization: Return to resting potential.

• Refractory Period: Time during which a new action potential cannot be initiated.

• All-or-None Principle: Action potentials either occur fully or not at all.

Step-by-Step Guidance

1. Start by defining the resting membrane potential and what maintains it.

2. Explain what happens when a stimulus reaches threshold and how this leads to depolarization (Na+ influx).

3. Describe repolarization (K+ efflux) and the return to resting potential.

4. Discuss the refractory period and its importance in unidirectional impulse transmission.

5. Summarize the all-or-none principle as it applies to action potentials.

Try outlining the sequence of events in an action potential before checking the answer!

Q5. Describe the synapse and explain the transmission of an impulse across the synapse; include the terms synapse, presynaptic and postsynaptic neuron, neurotransmitter.

Background

Topic: Synaptic Transmission

This question focuses on how neurons communicate at synapses using neurotransmitters.

Key Terms:

• Synapse: Junction between two neurons.

• Presynaptic Neuron: Neuron sending the signal.

• Postsynaptic Neuron: Neuron receiving the signal.

• Neurotransmitter: Chemical messenger released into the synaptic cleft.

Step-by-Step Guidance

1. Identify the presynaptic neuron and its synaptic knob containing synaptic vesicles.

2. Describe how an action potential arriving at the synaptic knob triggers neurotransmitter release.

3. Explain how neurotransmitters cross the synaptic cleft and bind to receptors on the postsynaptic neuron.

4. Discuss how this binding can initiate a new action potential in the postsynaptic neuron.

Try diagramming the steps of synaptic transmission before checking the answer!