Neurons Chapter 8: Cellular and Network Properties

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Questions and Answers

What is nervous tissue and where is it found in the body?

Nervous tissue is the tissue made of neurons and glial cells. It is found in the brain, spinal cord, and nerves.

What is the 'signal' sent by neurons?

Neurons send electrical signals known as action potentials.

How does 'disequilibrium' contribute to the ability of a neuron to function?

Disequilibrium allows for the generation and transmission of electrical signals in neurons.

Where are most interneurons found?

Both brain and spinal cord Signup and view all the answers

What is neurogenesis?

Neurogenesis is the process of generating new neurons in the brain throughout life. Signup and view all the answers

Neurons are excitable tissue that can send electrical signals.

True Signup and view all the answers

Neurons carry ________ signals.

electrical Signup and view all the answers

What are the two basic types of electrical signals discussed in the content?

Graded Potentials and Action Potentials Signup and view all the answers

What opens in response to the presence of Acetylcholine (ACh) in chemically gated ion channels?

Na+ gates Signup and view all the answers

Graded potentials lose strength as they move through the cell due to cytoplasmic resistance.

True Signup and view all the answers

Action potentials result from the movement of constant ion flow, which generates a wave of __________.

current Signup and view all the answers

Match the following neurotransmitters with their respective receptors:

Acetylcholine (ACh) = Nicotinic receptors Norepinephrine = Adrenergic receptors Signup and view all the answers

What is spatial summation?

Two or more neurons simultaneously firing and having an additive effect. Signup and view all the answers

Describe temporal summation.

Summation occurring when graded potentials overlap in time and have an additive effect. Signup and view all the answers

What is presynaptic facilitation?

It favors the release of neurotransmitter. Signup and view all the answers

Define long-term potentiation (LTP).

Activity at a synapse induces sustained changes in the quality or quantity of connections. Signup and view all the answers

What key element is involved in potentiation in the context of LTP?

Glutamate. Signup and view all the answers

Do all signals across a synapse cause an action potential on the post-synaptic membrane?

No Signup and view all the answers

How could you inhibit a neuron from generating an action potential?

Block neurotransmitter receptors Signup and view all the answers

Can you teach an old dog a new trick?

Yes Signup and view all the answers

Study Notes

Neurons: Cellular and Network Properties

Organization of the Nervous System

Nervous tissue is composed of neurons and glial cells
The central nervous system (CNS) consists of the brain and spinal cord
The peripheral nervous system (PNS) consists of nerves outside the CNS and brain
The PNS has two divisions: sensory (afferent) and motor (efferent)

Cells of the Nervous System

Neurons are the functional units of the nervous system, carrying electrical signals
Glial cells provide support and structure, outnumbering neurons 5:1
There are four types of glial cells in the CNS: astrocytes, oligodendrocytes, microglia, and ependymal cells
Glial cells have different functions, such as wrapping around axons to form myelin sheaths and providing support to neurons

Neuron Anatomy

A neuron consists of a cell body (soma), dendrites, and an axon
Dendrites receive incoming signals, while axons carry outgoing signals
Axons are covered by a myelin sheath, which insulates and speeds up signal transmission
Multipolar neurons have multiple dendrites, while unipolar and bipolar neurons have one or two dendrites, respectively

Synapses

A synapse is the region where an axonal terminal meets a target cell
Synapses can be chemical or electrical, and are not fixed for life
Chemical synapses involve the release of neurotransmitters from the presynaptic cell to the postsynaptic cell

Axonal Transport

Axonal transport is the process of moving materials along the axon
Anterograde transport moves materials from the cell body to the axon terminal, while retrograde transport moves materials in the opposite direction
Neural fatigue can occur when axonal transport is disrupted, preventing the transmission of signals

Electrical Signals in Neurons

Neurons are excitable tissue, able to generate electrical signals
Membrane potential is influenced by the concentration gradient of ions and membrane permeability
The Goldman-Hodgkin-Katz equation calculates the membrane potential based on the contribution of all ions that can cross the membrane

Membrane Potential

Resting membrane potential is the membrane potential of a resting cell
Graded potentials are temporary, localized changes in resting potential, caused by a stimulus
Action potentials are electrical impulses that propagate along the axon to the synapse
Ion movement creates electrical signals, with very few ions moving to create large changes in membrane potential

Ion Channels and Gated Ion Channels

Ion channels are named for the primary ion that passes through them
Gated channels control ion permeability, and can be mechanically gated, chemically gated, or voltage-gated
Threshold voltage varies from one channel type to another, and activation and inactivation rates also vary

Action Potentials

Action potentials are brief, large depolarizations that allow for rapid signaling over long distances
Conduction is the high-speed movement of an action potential along an axon
Action potentials are all-or-none, with a wave of electrical signal at constant amplitude

Generation of an Action Potential

Na+ and K+ move across the membrane during action potentials
Action potentials begin when a graded potential reaches the trigger zone and depolarizes to threshold
Voltage-gated Na+ channels open, allowing Na+ to flow into the cell, and then close, allowing K+ to flow out of the cell

Axonal Na+ Channels

Axonal Na+ channels have two gates: activation and inactivation gates
Action potentials will not fire during the absolute refractory period, due to the resetting of voltage-gated Na+ channels

Speed of Conduction

Axon diameter affects the propagation speed of action potentials
Larger diameter axons have faster propagation speeds
Myelination also increases the speed of conduction

Demyelination Disorders

Demyelination can occur due to various factors, such as heavy metal poisoning, bacterial toxins, and autoimmune disorders
Multiple sclerosis is a demyelinating disorder affecting the CNS
Guillain-Barré syndrome is a demyelinating polyneuropathy affecting the PNS### Ion Channels and Action Potentials
Ion channels for graded potentials allow for varying degrees of opening, whereas those for action potentials are all-or-none.
Action potentials occur in axons and are essential for long-distance communication.
They are all-or-none because a single action potential always results in the same amount of neurotransmitter release.

Myelin and Motor Neurons

Myelin insulates axons and increases the speed of action potential propagation.
If all motor neurons lost their myelin, muscle activity would be severely impaired.

Cell-to-Cell Communication in the Nervous System

Neurons communicate at synapses, which can be electrical or chemical.
Electrical synapses use gap junctions to pass electrical signals.
Chemical synapses use neurotransmitters that cross synaptic clefts and bind to specific receptors.

Neurotransmitters and Receptors

Acetylcholine (ACh) binds to cholinergic receptors, including nicotinic and muscarinic receptors.
Nicotinic receptors are ionotropic and found on skeletal muscles and in the autonomic division of the PNS and CNS.
Muscarinic receptors are metabotropic and found in the CNS and on target cells for the autonomic parasympathetic division of the PNS.

Amines and Adrenergic Receptors

Adrenergic neurons secrete norepinephrine, while the adrenal medulla secretes epinephrine.
Adrenergic receptors bind norepinephrine and epinephrine and are G protein-coupled receptors.

Synaptic Communication and Neurotransmitter Release

Stronger stimuli result in more neurotransmitter release, but a single action potential always releases a constant amount of neurotransmitter.
Action potentials code duration and magnitude in the frequency of action potentials produced.

Integration of Neural Information

Divergence occurs when one neuron sends signals to multiple neurons, while convergence occurs when multiple neurons send signals to one neuron.
Synaptic plasticity refers to changes in activity at synapses and can be short-term or long-term, enhancing or reducing synaptic activity.

Postsynaptic Responses

Slow synaptic potentials involve G-protein coupled receptors and second messengers.
Fast synaptic potentials involve opening of ion channels.
Excitatory postsynaptic potentials (EPSPs) are depolarizing, while inhibitory postsynaptic potentials (IPSPs) are hyperpolarizing.

Pathways and Integration of Information

Spatial summation occurs when two or more neurons simultaneously fire and have an additive effect.
Temporal summation occurs when graded potentials overlap in time and have an additive effect.
Synaptic activity can be modified by modulatory neurons, presynaptic facilitation, or presynaptic inhibition.

Long-Term Potentiation (LTP) and Synaptic Transmission

LTP alters synapses and is responsible for acquired behaviors, and is likely involved in learning and memory.
Glutamate is a key element in potentiation, and disorders of synaptic transmission are responsible for many diseases, including Parkinson's disease, schizophrenia, and depression.

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Description

This quiz covers the properties of neurons, including their cellular structure, electrical signals, and cell-to-cell communication in the nervous system. It also explores the integration of neural information transfer and disequilibrium's role in it.