Neuroscience: Conduction and Synapses

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Questions and Answers

What is the primary focus of the subdiscipline of Human Physiology?

The genetic basis of diseases

The functions of an organism and its parts (correct)

The structure of cells

The evolutionary history of species

Which of the following subdisciplines is NOT mentioned as part of Human Physiology?

Psychosociology (correct)

Neurophysiology

Cardiovascular Physiology

Exercise Physiology

What is the primary factor that increases conduction velocity in myelinated axons compared to unmyelinated axons?

Longer axon length

Fewer ion channels under myelin (correct)

Higher temperature of the axon

Presence of more ion channels under myelin

What is the process called when an action potential jumps between Nodes of Ranvier?

Saltatory conduction Signup and view all the answers

Which ion influx triggers exocytosis of synaptic vesicles at the axon terminal?

Ca2+ Signup and view all the answers

What happens first in the process of neurotransmitter release at a chemical synapse?

The action potential depolarizes the axon terminal Signup and view all the answers

How does saltatory conduction compare to continuous conduction regarding efficiency?

Saltatory conduction is more efficient than continuous conduction Signup and view all the answers

What role do voltage-gated Ca2+ channels play in neurotransmitter release?

They allow Ca2+ to enter the axon terminal Signup and view all the answers

What is the primary function of a synapse?

To facilitate communication between neurons or target tissues Signup and view all the answers

What does the term 'saltat' mean in relation to saltatory conduction?

To jump Signup and view all the answers

What triggers the exocytosis of synaptic vesicle contents?

Calcium ions entering the cell Signup and view all the answers

What happens after neurotransmitters diffuse across the synaptic cleft?

They bind to receptors on the postsynaptic cell Signup and view all the answers

What ion primarily enters the neuron to induce depolarization after neurotransmitter binding?

Sodium (Na+) Signup and view all the answers

Why does neurotransmitter release typically occur in a one-way direction?

Only presynaptic neurons release neurotransmitters Signup and view all the answers

What is the effect of excitatory neurotransmitters on the postsynaptic neuron?

They generate an excitatory postsynaptic potential (EPSP) Signup and view all the answers

What characterizes the inhibitory postsynaptic potential (IPSP)?

It leads to a decrease in the postsynaptic neuron’s membrane potential Signup and view all the answers

What defines the direction of a concentration gradient for a substance such as CO2?

From an area of high concentration to low concentration Signup and view all the answers

What is the role of the axon terminal in neurotransmitter release?

It undergoes depolarization to open voltage-gated channels Signup and view all the answers

What characterizes passive transport across a plasma membrane?

Substances move down their concentration or electrochemical gradient Signup and view all the answers

Which statement is true regarding the electrical gradient for K+ ions?

It always favors the movement of K+ ions into the cell Signup and view all the answers

Which type of ion channels are opened when the presynaptic neuron is depolarized?

Voltage-gated Ca2+ channels Signup and view all the answers

What does Fick's law of diffusion explain?

The calculation of diffusion rate based on concentration difference Signup and view all the answers

What is the definition of an electrochemical gradient?

A combination of electrical and chemical forces on ions Signup and view all the answers

What is one of the primary roles of cell signaling in the body?

To coordinate body activities and maintain homeostasis. Signup and view all the answers

Which factor does NOT influence the rate of diffusion?

The size of the cell membrane Signup and view all the answers

Which type of cellular communication allows for rapid communication between neighboring cells?

Gap junctions. Signup and view all the answers

In which type of transport is cellular energy required?

Active transport Signup and view all the answers

Which of the following statements about passive transport is incorrect?

It requires specific transport proteins for all molecules Signup and view all the answers

What is a step involved in the process of cellular communication through extracellular messengers?

Binding of chemical messenger to a receptor. Signup and view all the answers

How do cell-to-cell binding interactions primarily function?

Through the binding of surface molecules. Signup and view all the answers

What is a consequence of a disturbance in extracellular chemical signaling?

It could disrupt the cellular response. Signup and view all the answers

Which of the following examples represents an extracellular chemical messenger?

Erythropoietin (EPO). Signup and view all the answers

Predict the impact of increased receptor affinity on cellular communication.

Increased specificity of signal activation. Signup and view all the answers

What mechanism involves the direct connection of cells through proteins for communication?

Gap junctions. Signup and view all the answers

Study Notes

Conduction Velocity

Myelinated axons have fewer ion channels under the myelin sheath, resulting in faster conduction than unmyelinated axons.
Saltatory conduction, the process of action potential jumping between nodes of Ranvier, is more efficient than continuous conduction, requiring less ATP.
The term "saltat" means leaping, referring to the jumping nature of the action potential during saltatory conduction.

Synapses

A synapse represents the communication point between neurons or between a neuron and a target tissue.

Chemical Synapses: Neurotransmitter Release

An action potential arriving at the axon terminal triggers the release of neurotransmitters.
The depolarization of the axon terminal opens voltage-gated Ca²⁺ channels, allowing calcium to enter the cell.
Calcium entry triggers the exocytosis of synaptic vesicle contents, releasing neurotransmitters into the synaptic cleft.
Neurotransmitters diffuse across the synaptic cleft and bind with receptors on the postsynaptic cell, activating chemically-gated Na⁺ channels.
Sodium ions rush into the postsynaptic cell, depolarizing the membrane and potentially generating an action potential.

Neuron Function

Neurotransmitters released from the presynaptic neuron can either excite or inhibit the postsynaptic neuron.
Excitatory postsynaptic potentials (EPSPs) depolarize the postsynaptic neuron, increasing the likelihood of an action potential.
Inhibitory postsynaptic potentials (IPSPs) block depolarization, decreasing the likelihood of an action potential.

Physiology

Physiology is the study of the functions of an organism and its constituent parts.
Human physiology focuses on the workings of the human body.
Sub-disciplines of physiology include neurophysiology, cardiovascular physiology, respiratory physiology, exercise physiology, and pathophysiology.

Gradients Across the Plasma Membrane

Concentration gradient: Difference in the concentration of a chemical between two regions, such as inside and outside of a cell.
Electrical gradient: Difference in electrical charges between two regions, such as across the plasma membrane.
Electrochemical gradient: The combination of both electrical and chemical forces acting on ions.

Classification of Membrane Transport

Passive transport: Movement of substances across the plasma membrane without cellular energy input, going down the concentration or electrochemical gradient.
Active transport: Movement of substances across the plasma membrane requiring cellular energy, such as ATP, going against the concentration or electrochemical gradient.

Diffusion

Diffusion is a type of passive transport where particles randomly move from an area of higher concentration to an area of lower concentration.
Factors influencing diffusion include the steepness of the concentration gradient, temperature, mass of the diffusing particle, surface area, and diffusion distance.
Fick's law of diffusion describes the rate of diffusion.

Cell Signaling

Cells communicate with each other to coordinate body activities and maintain homeostasis.
Types of cellular communication include gap junctions, cell-to-cell binding, and communication through extracellular chemical messengers.

Gap Junctions

Gap junctions are formed by connexins, membrane proteins that create tunnels called connexons connecting neighboring cells.
Gap junctions allow for rapid diffusion and communication between cells.
Examples of cells with gap junctions include neurons and muscle cells.

Cell-to-Cell Binding

Cell-to-cell binding involves surface molecules on two different cells interacting with each other.
An example is the interaction between leukocytes and their targets during immune responses.

Extracellular Messengers

Extracellular chemical messengers are the most common type of communication.
They orchestrate a wide variety of responses.
Steps include binding of the messenger to a receptor on the downstream cell, signal transduction, and cellular response.

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Description

This quiz explores the conduction velocity of myelinated versus unmyelinated axons and the efficient process of saltatory conduction. Additionally, it covers the role of synapses in neuron communication and the mechanics of neurotransmitter release at chemical synapses.