Neuroscience: Neurotransmitters and Synapses

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Questions and Answers

Which neurotransmitters are primarily used in the autonomic nervous system?

Acetylcholine, dopamine, and histamine

Serotonin, epinephrine, and glutamate

Dopamine, serotonin, and norepinephrine

Acetylcholine, norepinephrine, and epinephrine (correct)

What is the first step in the operation of autonomic reflexes?

Integration centers processing sensory information

Effectors responding to motor commands

Receptors detecting changes in the environment (correct)

Efferent neurons transmitting signals to effectors

What effect does sympathetic stimulation have on blood vessels?

It has no significant effect on blood pressure

It decreases vascular resistance by relaxing vascular smooth muscle

It typically causes vasoconstriction, increasing blood pressure (correct)

It causes vasodilation and decreases blood pressure

What is the main function of elastic arteries?

To accommodate blood surge from the heart and maintain blood pressure Signup and view all the answers

What characterizes metarterioles in the circulatory system?

They connect arterioles to capillary beds and regulate blood flow Signup and view all the answers

What occurs when voltage-gated Na+ channels inactivate during repolarization?

Voltage-gated K+ channels open. Signup and view all the answers

How do precapillary sphincters function?

They regulate blood flow into capillary beds based on the body's needs Signup and view all the answers

What is a key structural characteristic of capillaries?

They are single cell thick for efficient exchange Signup and view all the answers

What is the main reason for afterhyperpolarization?

Increased K+ permeability exceeding resting levels. Signup and view all the answers

What role do valves in medium veins play in the circulatory system?

They maintain blood flow toward the heart, preventing backflow Signup and view all the answers

What happens to the h-gate of Na+ channels after depolarization?

It blocks the Na+ channel, causing inactivation. Signup and view all the answers

What is the role of K+ channels during repolarization?

They allow K+ to leave the cell, making the membrane more negative. Signup and view all the answers

How do voltage-gated K+ channels differ from Na+ channels?

K+ channels have one gate that opens slowly, whereas Na+ channels open quickly. Signup and view all the answers

What is the primary effect of excitatory postsynaptic potentials (EPSP) on the postsynaptic membrane?

It increases the likelihood of generating an action potential. Signup and view all the answers

What defines the absolute refractory period?

No stimulus can elicit a new action potential regardless of its strength. Signup and view all the answers

Which neurotransmitter is primarily involved in muscle signaling at the neuromuscular junction?

Acetylcholine Signup and view all the answers

Which type of synapse is characterized by moving the postsynaptic membrane away from the threshold for an action potential?

Inhibitory synapse Signup and view all the answers

What is primarily responsible for the repolarization of the membrane?

K+ efflux through voltage-gated K+ channels. Signup and view all the answers

What process involves the additive effect of multiple synaptic inputs from different presynaptic neurons?

Spatial summation Signup and view all the answers

Why is the closure of voltage-gated K+ channels important after an action potential?

It restores the membrane potential to its resting level. Signup and view all the answers

Which enzyme is responsible for metabolizing acetylcholine in the synaptic cleft?

Acetylcholinesterase Signup and view all the answers

What is the primary role of serotonin in the brain?

Affecting mood and emotions Signup and view all the answers

Which neurotransmitter types are classified as biogenic amines?

Catecholamines and serotonin Signup and view all the answers

What are the two types of inhibitory amino acids?

GABA and glycine Signup and view all the answers

What defines the function of neurotransmitters in neural communication?

They act as chemical messengers transmitting signals across synapses. Signup and view all the answers

What is the primary role of the axon in a neuron?

To send outgoing signals to other neurons. Signup and view all the answers

What occurs when glial cells fail to support neurons adequately?

Neuronal signaling can be disrupted, causing dysfunction. Signup and view all the answers

What determines the membrane potential in a resting neuron?

The relative concentration of potassium and sodium ions. Signup and view all the answers

What is the significance of the Nernst equation in neuroscience?

It calculates the electrochemical equilibrium potential for ions. Signup and view all the answers

What is the approximate equilibrium potential for potassium ions (K+) according to the Nernst equation?

-90 mV Signup and view all the answers

Which components primarily determine the resting membrane potential of a cell?

Concentration of electrolytes and membrane permeability to different ions. Signup and view all the answers

What best describes the function of dendrites in a neuron?

To receive incoming signals from other neurons. Signup and view all the answers

What effect does exercise have on blood flow to muscles?

Blood flow increases due to vasodilation. Signup and view all the answers

What best describes autoregulation in blood flow?

It is the ability of organs to maintain constant blood flow despite perfusion pressure changes. Signup and view all the answers

What local factors can influence vasomotor control?

Metabolic activity, oxygen levels, and pH. Signup and view all the answers

How do local metabolic byproducts typically affect arterioles?

They promote vasodilation to increase blood flow. Signup and view all the answers

What relationship exists between cardiac output and blood pressure?

Increased cardiac output can raise blood pressure if resistance stays constant. Signup and view all the answers

What is the primary role of feedback mechanisms in blood flow regulation?

To adjust blood flow in real-time according to tissue requirements. Signup and view all the answers

What role does the baroreceptor reflex play in arterial circulation?

It adjusts heart rate and vascular resistance in response to blood pressure changes. Signup and view all the answers

What is the primary function of capillaries?

Exchange of materials between tissues and blood. Signup and view all the answers

Study Notes

Neurotransmitters and Neural Communication

Neurotransmitters are chemical messengers that facilitate communication across synapses between neurons.
A synapse is the junction where two neurons transmit information.
Neurotransmitters are released into the synaptic cleft from terminal buttons to relay signals to the next neuron.

Neuron Structure and Function

The axon sends outgoing signals from the neuron, while dendrites receive incoming signals.
Classification of neurons based on structure and function aids in identifying their roles in the nervous system.
Glial cells support neurons and regulate their environment; failure to support can disrupt neuronal signaling.

Membrane Potential

Membrane potential is the voltage difference across a resting cell membrane, typically negative inside.
Charges align along the plasma membrane due to opposite charge attraction.
Key determinants of membrane potential include electrolyte concentrations in extracellular and intracellular fluids and membrane permeability to ions.
Chemical and electrical forces act concurrently on ions across the membrane.
Potassium (K+) permeability plays a crucial role in determining resting potential.

Ionic Equilibrium and Nernst Equation

Electrochemical equilibrium occurs when the concentration gradient and electrical gradient balance, leading to no net ion movement.
The Nernst equation (Eion = 61 log (Cout / Cin)) calculates the equilibrium potential for ions.
Equilibrium potential for K+ is about -90 mV; for Na+ it is approximately +60 mV.

Action Potential Mechanics

The action potential is characterized by Na+ influx causing depolarization; positive feedback leads to more Na+ channels opening.
At peak depolarization, Na+ channels inactivate due to h-gate blockage.
During repolarization, K+ channels open, allowing K+ to exit and restore a more negative membrane potential.
Afterhyperpolarization occurs when K+ permeability surpasses resting levels, leading to potential values more negative than the resting state.

Refraction and Propagation

The absolute refractory period prohibits any stimulus from triggering another action potential.
The relative refractory period allows a stronger-than-usual stimulus to elicit an action potential.
Excitatory synapses (EPSP) depolarize the postsynaptic membrane, while inhibitory synapses (IPSP) hyperpolarize it.
Temporal and spatial summation refer to the additive effects of synaptic inputs over time or from different neurons, respectively.

Neurotransmitter Types and Functions

Major neurotransmitter groups include acetylcholine, catecholamines, and amino acids.
Acetylcholine is significant in both autonomic and somatic nervous systems; synthesized in axon terminals and metabolized by acetylcholinesterase.
Biogenic amines, including dopamine and serotonin, are derived from amino acids and influence mood and emotions.

Neuromuscular Junction (NMJ)

The NMJ involves muscle fibers and α-motor neurons that communicate through the motor endplate.
Nicotinic acetylcholine receptors are prominent at the NMJ.
Key neurotransmitters in the autonomic nervous system include acetylcholine, norepinephrine, and epinephrine.

Vascular Anatomy

Arteries transport oxygenated blood away from the heart; primary types are elastic and muscular arteries.
Elastic arteries handle blood surges while muscular arteries manage distribution and regulate flow.
Arterioles and metarterioles play critical roles in controlling blood flow to capillary beds.

Capillary Structure and Function

Capillaries, being one cell thick, facilitate efficient exchange between blood and tissues.
Three capillary types include continuous, fenestrated, and sinusoidal types; sinusoidal capillaries are found in bone marrow.

Blood Flow Regulation

Local vasomotor control is influenced by metabolic activity and local metabolic byproducts, promoting vasodilation or vasoconstriction as needed.
Baroreceptor reflex regulates arterial circulation by adjusting heart rate and resistance based on blood pressure changes.
Autoregulation allows organs to maintain consistent blood flow amidst fluctuating pressures.

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Description

Explore the critical roles that neurotransmitters play in neural communication and the structure of synapses. Understand how information is transmitted between neurons, including the functions of the axon and synaptic cleft. Test your knowledge on the essentials of neuroscience.