Neuroscience Chapter on Action Potentials

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary function of action potentials in neurons?

Allow communication over both short and long distances (correct)

Are temporary changes in resting potential

Allow communication over short distances only

Serve as the resting membrane potential

What defines a graded potential?

It propagates along the axon in an all-or-none fashion

It initiates an action potential immediately

It is a temporary and localized change in resting potential (correct)

It is produced by a sustained stimulus

Which process is responsible for releasing neurotransmitters at the presynaptic membrane?

Graded potential generation

Synaptic activity (correct)

Resting membrane potential maintenance

Action potential generation

Which statement about the resting membrane potential (RMP) is true?

It reflects the transmembrane potential of a resting cell. Signup and view all the answers

How does an action potential propagate along the axon?

In a sequential all-or-none fashion Signup and view all the answers

What is the resting membrane potential usually measured at?

-70 mV Signup and view all the answers

Which ions are primarily involved in establishing the resting membrane potential?

Na+ and K+ Signup and view all the answers

What happens to the inside of the cell during depolarization in an action potential?

It becomes more positive. Signup and view all the answers

Which mechanism actively maintains the resting membrane potential?

Sodium-potassium ATPase pump Signup and view all the answers

What type of potentials are described as small deviations from the resting membrane potential?

Graded potentials Signup and view all the answers

What type of neuron transmits sensory information to the central nervous system?

Afferent neurons Signup and view all the answers

What is the term for when graded potentials are added together to increase amplitude?

Summation Signup and view all the answers

Which type of neuroglia is primarily involved in the production and circulation of cerebrospinal fluid (CSF)?

Ependymal cells Signup and view all the answers

Which glial cells make up the myelin sheath in the central nervous system?

Oligodendrocytes Signup and view all the answers

Which statement about an action potential is true?

It follows the all-or-none principle. Signup and view all the answers

Which channels must open to initiate a graded potential?

Ligand-gated or mechanically-gated channels Signup and view all the answers

What is the primary function of motor (efferent) neurons?

Responding to stimuli Signup and view all the answers

How are neurons classified functionally?

By the direction of impulse propagation Signup and view all the answers

Which neuroglial cells in the peripheral nervous system clear cellular debris and support axon regeneration?

Schwann cells Signup and view all the answers

What characteristic distinguishes neuroglia from neurons?

Neuroglia make up about half of the nervous system volume Signup and view all the answers

Which of these functions is NOT associated with the integrative functions of the nervous system?

Responding to stimuli Signup and view all the answers

What type of summation occurs when several presynaptic end bulbs release neurotransmitters simultaneously?

Spatial summation Signup and view all the answers

What is a key difference between the repair capacity of the CNS and PNS?

In the CNS, inhibitory influences from neuroglia hinder repair. Signup and view all the answers

What sequence is correctly associated with the repair process in the PNS?

Chromatolysis, Wallerian degeneration, Regeneration tube Signup and view all the answers

What term describes the nervous system's capability to change based on experience?

Neuroplasticity Signup and view all the answers

Which of the following neurotransmitters is classified as a small molecule neurotransmitter?

Dopamine Signup and view all the answers

What is the threshold membrane potential necessary for the generation of an action potential?

-55 mV Signup and view all the answers

What happens during the rapid depolarization phase of an action potential?

Na+ ions flow into the cytoplasm. Signup and view all the answers

What occurs first in the sequence of generating an action potential?

Depolarization to threshold Signup and view all the answers

What defines the absolute refractory period?

Sodium channels are inactivated, preventing any action potential. Signup and view all the answers

What is a characteristic of action potentials compared to graded potentials?

They maintain their strength as they propagate. Signup and view all the answers

At what membrane potential do K+ channels begin to open during an action potential?

+30 mV Signup and view all the answers

What occurs during the repolarization phase of an action potential?

Na+ channels inactivate and K+ channels open. Signup and view all the answers

What is the final resting membrane potential after an action potential?

-70 mV Signup and view all the answers

What characterizes a chemical synapse compared to an electrical synapse?

It facilitates one-way information transfer. Signup and view all the answers

What is the effect of excitatory postsynaptic potentials (EPSPs) on the postsynaptic neuron?

They depolarize the postsynaptic neuron. Signup and view all the answers

Which of the following factors does NOT affect signal propagation speed in axons?

Signal frequency Signup and view all the answers

How is a neurotransmitter typically removed from the synaptic cleft?

It undergoes enzymatic degradation. Signup and view all the answers

What type of receptor is an ionotropic receptor?

A receptor that immediately opens ion channels. Signup and view all the answers

What happens during the generation of inhibitory postsynaptic potentials (IPSPs)?

The postsynaptic membrane becomes hyperpolarized. Signup and view all the answers

Which property is characteristic of metabotropic receptors?

They activate second messenger systems. Signup and view all the answers

What is the role of gap junctions in electrical synapses?

They connect the cytoplasm of adjacent cells. Signup and view all the answers

Study Notes

Nervous Tissue Overview

Nervous tissue is responsible for communication throughout the body.
The nervous system is organized into two main parts:
- Central Nervous System (CNS): Brain and spinal cord.
- Peripheral Nervous System (PNS): Cranial nerves, and spinal nerves. The PNS also includes enteric plexuses in the small intestine and sensory receptors in the skin.

Functions of the Nervous System

Sensory: Detects changes through sensory receptors.
Integrative: Analyzes sensory information, stores aspects, and makes decisions.
Motor: Responds to stimuli.

Nervous Tissue Histology

Neurons: Electrically excitable cells that transmit signals throughout the body. Key structures include:
- Dendrites: Receive signals.
- Cell body: Contains the nucleus.
- Axon: Transmits signals.
- Axon terminal: Passes signals to next cell.

Structural Classification of Neurons

Multipolar: Many dendrites, one axon. Most common neuron type.
Bipolar: One dendrite, one axon. Found in special sensory organs.
Unipolar: One process, emerging from the cell body, that branches into peripheral and central processes. Most sensory neurons in PNS are unipolar.

Functional Classification of Neurons

Sensory (afferent): Carry impulses toward the CNS.
Motor (efferent): Carry impulses away from the CNS.
Interneurons (association neurons): Located within the CNS; connect sensory and motor neurons.

Neuroglia

Support cells in the nervous system.
Not electrically excitable.
Divided into 6 types:
- 4 types of neuroglia found in the central nervous system (CNS)
  - Ependymal cells: line the central cavities of the brain; help produce and circulate cerebrospinal fluid (CSF)
  - Astrocytes: Most numerous neuroglia in CNS, guide axon regeneration, maintain the blood-brain barrier.
  - Oligodendrocytes: myelinate CNS axons (a type of glial cell).
  - Microglia: Smallest neuroglia in the CNS, act as phagocytes for the defense of the CNS
- 2 types of neuroglia found in the peripheral nervous system (PNS)
  - Schwann cells: myelinate PNS axons; participate in axon regeneration.
  - Satellite cells: surround neuron cell bodies and regulate O2, CO2, neurotransmitters, and nutrients around the neurons.

Myelination of Neurons

Myelin sheath: Formed by Schwann cells (PNS) and oligodendrocytes (CNS).
Myelin insulates axons, speeding up signal conduction.
Nodes of Ranvier: Gaps in the myelin sheath, allow for faster signal transmission (saltatory conduction).

Gray Matter vs. White Matter

Gray matter: Contains neuron cell bodies, dendrites, and unmyelinated axons
White matter: Contains mostly myelinated axons

Electrical Signals in Neurons

Excitable cells communicate via action potentials (AP) or graded potentials (GP).
APs transmit signals over long distances, GPs over short distances.
AP & GPs depend on the resting membrane potential (RMP).

Graded Potentials

Small, localized changes in transmembrane potential.
Can be depolarizing (positive changes) or hyperpolarizing (negative changes).
Strength of the graded potential depends on the stimulus strength.
May sum up to initiate an action potential.

Action Potentials

Rapid, large changes in transmembrane potential.
All-or-none principle (threshold potential must be reached to trigger an action potential).
Consist of: depolarization, repolarization, and sometimes an after-hyperpolarization phase.

Propagation of Action Potentials

Action potentials propagate along the axon.
Propagation speed is influenced by axon diameter and myelination.
Continuous conduction: along unmyelinated axons.
Saltatory conduction: along myelinated axons (speedier)

Signal Transmission at Synapses

Synapse: Junction between neurons or between a neuron and an effector.
- Electrical synapses: fast, direct signal transmission.
- Chemical synapses: one-way signal transmission using neurotransmitters.

Postsynaptic Potentials

Postsynaptic neurons respond to neurotransmitters with either EPSPs (depolarizing) or IPSPs (hyperpolarizing) postsynaptic potentials. Summation of these potentials determines if an action potential is generated.

Neurotransmitters

Chemical messengers that transmit signals across chemical synapses.
Small molecule neurotransmitters: Acetylcholine, amino acids, biogenic amines, ATP and other purines, nitric oxide, and carbon monoxide.
Neuropeptides: More complex molecules.

Removal of Neurotransmitters

Neurotransmitters are removed from the synapse to terminate the signal.
Removal methods: diffusion, enzymatic degradation (e.g., acetylcholine), and uptake into cells.

Summation

Spatial summation: Combining effects of multiple presynaptic neurons releasing neurotransmitter.
Temporal summation: Combining effects of a single presynaptic neuron releasing multiple neurotransmitters.

Regeneration and Repair in Nervous Tissues

The CNS shows limited ability to regenerate.
The PNS shows a much greater potential for regeneration
- Chromatolysis, Wallerian degeneration, and formation of a regeneration tube participate in PNS regrowth
- Inhibitory factors from glial cells, specifically oligodendrocytes, may be responsible at least in part for the poor regeneration seen in the CNS.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Test your knowledge of action potentials, graded potentials, and membrane potentials in neurons. This quiz covers key concepts such as neurotransmitter release, depolarization, and the role of different ions in neuronal function. Perfect for students studying neuroscience or biology.