Neuroscience Action Potentials and Graded Potentials

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Questions and Answers

What primarily determines the amplitude of a graded potential?

The distance from the trigger zone

The type of ion channels involved

The duration of the stimulus

The strength of the stimulus (correct)

Which statement describes action potentials accurately?

They can vary in frequency but not amplitude

Action potentials occur in a single, fixed amplitude

They can only occur if the membrane potential reaches a threshold (correct)

They consist of phases of hyperpolarization and depolarization

During which phase of an action potential does the membrane potential become more positive?

Resting phase

Hyperpolarization

Repolarization

Depolarization (correct)

What type of channels are primarily involved in grading potentials?

Mechanically gated or ligand-gated ion channels Signup and view all the answers

How do graded potentials propagate?

They exhibit decremental conduction over short distances Signup and view all the answers

What occurs during repolarization of an action potential?

The membrane potential becomes more negative Signup and view all the answers

What is a key difference between graded potentials and action potentials?

Graded potentials can be initiated at any part of the neuron Signup and view all the answers

What type of channels are responsible for the generation of action potentials?

Voltage-gated channels for sodium and potassium Signup and view all the answers

What triggers ligand-gated channels to open in neurons?

Binding of a chemical ligand Signup and view all the answers

Which of the following channels opens in response to mechanical stimuli?

Mechanically gated channels Signup and view all the answers

What primarily determines the resting membrane potential in a non-conducting neuron?

Selective permeability and ion distribution Signup and view all the answers

Which of the following statements about graded potentials is true?

Graded potentials result from the opening of mechanically or ligand-gated ion channels. Signup and view all the answers

What is a characteristic of voltage-gated channels?

They open when the membrane potential changes. Signup and view all the answers

Which of the following best explains why the inside of a non-conducting neuron is negative?

Anions within the cell are unable to leave. Signup and view all the answers

How do Na+/K+ pumps contribute to the resting membrane potential?

They create a higher concentration of Na+ outside the cell. Signup and view all the answers

Which statement regarding the distribution of ions across the plasma membrane is correct?

The distribution of ions is uneven across the membrane. Signup and view all the answers

What is a necessary condition for repair in the peripheral nervous system (PNS)?

Intact cell body Signup and view all the answers

Which of the following is NOT a step involved in the repair process of the PNS?

Neurogenesis Signup and view all the answers

What is a primary characteristic of multiple sclerosis?

Destruction of myelin sheath Signup and view all the answers

Which symptom is most commonly associated with depression?

Lack of interest in activities Signup and view all the answers

What class of medication is commonly used to treat depression?

Selective serotonin reuptake inhibitors (SSRIs) Signup and view all the answers

What initiates the episodes of epilepsy?

Abnormal synchronous electrical discharges Signup and view all the answers

What causes excitotoxicity in the central nervous system?

High levels of glutamate Signup and view all the answers

What is a symptom of seasonal affective disorder (SAD)?

Mood changes related to seasons Signup and view all the answers

What is the typical amplitude of action potentials?

Typically about 100 mV Signup and view all the answers

How does the refractory period differ between graded potentials and nerve impulses?

Graded potentials have no refractory period Signup and view all the answers

Which factor does NOT affect the propagation speed of action potentials?

Distance from the heart Signup and view all the answers

Which statement best describes graded potentials?

They can be both hyperpolarizing and depolarizing Signup and view all the answers

What is a key characteristic of action potentials during propagation?

They maintain their strength while traveling Signup and view all the answers

Which characteristic distinguishes nerve impulses from graded potentials?

They only consist of depolarizing phases Signup and view all the answers

How does the diameter of an axon influence the propagation of action potentials?

Larger diameter axons propagate faster Signup and view all the answers

What happens to action potentials during the trigger zone?

They begin to propagate along the axon Signup and view all the answers

What is the primary result of summation in the context of neurotransmitter release?

It increases the likelihood of creating a nerve impulse. Signup and view all the answers

What distinguishes spatial summation from temporal summation?

Spatial summation involves multiple presynaptic neurons, whereas temporal summation involves one neuron firing multiple times. Signup and view all the answers

Which neurotransmitter is classified as a small molecule neurotransmitter?

Amino acids Signup and view all the answers

What is the primary role of endorphins in the nervous system?

Inhibit pain impulses. Signup and view all the answers

Which of the following neuropeptides is primarily associated with pain perception?

Substance P Signup and view all the answers

Which neurotransmitter is likely to play a role in memory and learning, according to its classifications?

Enkephalins Signup and view all the answers

What could be a potential function of dynorphins in the nervous system?

They may control pain and register emotions. Signup and view all the answers

Which of the following is NOT considered a small molecule neurotransmitter?

Substance P Signup and view all the answers

What is the primary function of gap junctions in electrical synapses?

To synchronize the activity of a group of cells Signup and view all the answers

What characterizes a chemical synapse as opposed to an electrical synapse?

It involves the release of neurotransmitters Signup and view all the answers

Which type of postsynaptic potential is associated with depolarization?

Excitatory postsynaptic potential Signup and view all the answers

What is the role of ionotropic receptors at chemical synapses?

To bind neurotransmitters and open ion channels Signup and view all the answers

How can neurotransmitters be removed from the synaptic cleft?

By diffusion, enzymatic degradation, or uptake into cells Signup and view all the answers

What is a characteristic of metabotropic receptors?

They are coupled to a separate ion channel via G proteins Signup and view all the answers

What typically happens to a postsynaptic neuron that receives multiple excitatory inputs simultaneously?

It can become depolarized Signup and view all the answers

Which of the following statements about neurotransmitter action at chemical synapses is correct?

Neurotransmitters cause either excitatory or inhibitory graded potentials Signup and view all the answers

Study Notes

Nervous Tissue Overview

The nervous system maintains homeostasis, controlling conditions within healthy limits.
Learning about the different branches and cell types is important.

Nervous System Overview

Neurons (nerve cells) are electrically excitable, transmitting information through action potentials.
Sensory neurons receive information from receptors (e.g., in skin).
Interneurons (in brain or spinal cord) process information.
Motor neurons transmit signals to effectors (e.g., muscles). The diagram on page four displays these components.

Nervous System Organization

The central nervous system (CNS) comprises the brain and spinal cord.
The peripheral nervous system (PNS) includes cranial nerves, spinal nerves, enteric plexuses, and sensory receptors. A diagram on page six illustrates this.

Functions of the Nervous System

Sensory function: Detects sensory stimuli.
Integrative function: Processes sensory information and decides on appropriate actions.
Motor function: Initiates actions in response to the integrative functions.

Nervous Tissue Histology

Neurons, the conducting cells, and nerve neuroglia, the supporting cells.

Neurons (Structure and Types)

Neurons are electrically excitable cells.
Action potential is the nerve impulse.
Neurons are characterized by their processes; multipolar, bipolar, and pseudounipolar.
Diagrams on pages twelve and thirteen depict the parts of a neuron including the dendrites, cell body, axon and axon terminal.

Neuron Types

Sensory (afferent) neurons carry information to the CNS.
Motor (efferent) neurons carry signals from the CNS.
Interneurons (association neurons) connect sensory and motor neurons, processing information.

Neuroglia (Supporting Cells)

Neuroglia are not electrically excitable.
They make up about half the volume of the nervous system.
They are capable of dividing.
There are six main types, four in the CNS (astrocytes, oligodendrocytes, microglia, ependymal cells) and two in the PNS (satellite cells and Schwann cells). Page twenty details these.

Myelination

Myelin sheath is produced by Schwann cells (PNS) and oligodendrocytes (CNS) surrounding axons. Myelination increases propagation of action potentials, increasing speed. Pages twenty-three and twenty-four show diagrams of myelinated axons.

White Matter vs. Gray Matter

White matter consists of myelinated axons.
Gray matter consists of neuron cell bodies, dendrites, and unmyelinated axons.

Electrical Signals in Neurons

Excitable cells communicate via action potentials or graded potentials.
Action potentials transmit signals over short and long distances
Graded potentials transmit signals over short distances.

Ion Channels in Neurons

Leak channels alter between open and closed states
Ligand-gated channels open/close according to chemical stimulus.
Mechanically gated channels open according to mechanical stimulation
Voltage gated channels open/close according to membrane potential.

Postsynaptic Potentials

Excitatory postsynaptic potentials (EPSPs) are depolarizations—increasing the chances of an action potential.
Inhibitory postsynaptic potentials (IPSPs) are hyperpolarizations—decreasing the chances of an action potential.

Neurotransmitters

Small molecule neurotransmitters (e.g., acetylcholine, amino acids, biogenic amines, ATP/purines, nitric oxide, carbon monoxide) and neuropeptides (e.g., substance P, enkephalins, endorphins, etc.) are released at chemical synapses to transmit signals.
Pages 75-80 detail the various neurotransmitters, and their functions.

Summation

Summation is the addition of postsynaptic potentials (EPSPs and IPSPs) to determine if an action potential will occur.
Spatial summation refers to the simultaneous input from multiple sources on a postsynaptic neuron.
Temporal summation refers to the addition of sequential inputs received from a single source.

Neural Circuits

Neural circuits are groups of neurons that perform specific information processing.
Examples include simple series, diverging, converging, reverberating, and parallel after-discharge circuits (pages 81-84).

Regeneration

The nervous system can exhibit plasticity, changing in response to experience.
Regeneration of neurons in the CNS is limited, compared to the PNS, primarily due to inhibitory neuroglial influences and lack of growth cues.

Neural Disorders

Multiple sclerosis is an autoimmune condition that destroys myelin sheaths.
Depression is a neurological condition with various types, including major depression, dysthymia, bipolar disorder, and seasonal affective disorder.
Other disorders like epilepsy and excitotoxicity—damage to neurons from excessive excitation are also mentioned. Pages 89-92 detail these disorders.

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Description

Test your understanding of action potentials and graded potentials in neuroscience. This quiz covers key concepts such as membrane potentials, channel types, and the differences between graded and action potentials. Perfect for students looking to solidify their knowledge of neuronal function.