chapter 41: Neural Signaling and Neuron Function Overview

Functional regions of a neuron

receptive region (dendrites and cell body), conducting region (axon), and secretory region (axon terminal)

neuron function

produce and transmit electrical signals (nerve impulses or action potentials)

multipolar neuron

A type of neuron characterized by multiple extensions from the cell body.

cytoplasmic extensions (processes)

dendrites: receive stimulation, conduct toward cell body

axon: conduct impulses away from cell body to effector

axon hillock

sufficient stimulation initiates action potential along axon

myelin sheath

insulating membrane around axon - separate cell

node of ranvier

gap in myelin

axon collateral

branches at end of axon - along length

terminal branches

division at end of axon

synaptic terminal

end of terminal branches, transmits signal to effect

synapse

junction between a synaptic terminal and effector (neuron, muscle, gland)

afferent neurons

sensory neurons

bringing thing in - toward CNS

Major structural types of neurons

pseudounipolar, bipolar, and multipolar.

multipolar

multiple extensions off of cell body

single axon and multiple dendrites

99% of all neurons

bipolar

one axon and one dendrite and cell body between them

eye and olfactory epithelium (nasal cavity)

pseudounipolar

cell body off to side

single short process that splits into two axons

Interneuron (associated neuron)

in CNS (brain and spinal cord)

efferent neuron

Motor neuron

information going out

Glial cells

Supportive cells in the nervous system that perform various functions.

astrocytes

large, star-shaped cells with many processes

anchor neurons and blood vessels in place

transport nutrients and gasses between blood vessels and neurons

regulate extracellular environment of brain

form blood brain barrier

repair damaged tissue

ependymal cells

line internal cavities of the CNS and have cilia

function: produce and circulate of CSF

microglial cells

found near blood vessels

specialized macrophages, remove bacteria and cell debris

CNS

Central Nervous System, consisting of the brain and spinal cord.

PNS

Peripheral Nervous System, consisting of all nerves outside the CNS.

Nerve regeneration

The process by which nerves repair themselves after injury.

Resting potential

The transmembrane potential of a neuron when it is not actively transmitting signals.

Ion channels

Proteins that allow ions to pass through the neuron's membrane.

Action potential

A rapid change in membrane potential that propagates along the neuron.

Sodium voltage-gated channels

Channels that open in response to membrane depolarization, allowing sodium ions to enter the neuron.

Potassium voltage-gated channels

Channels that open to allow potassium ions to exit the neuron, helping to repolarize the membrane.

Positive feedback in nerve conductance

A process where an initial stimulus leads to an amplification of the response.

Negative feedback in nerve conductance

A process that counteracts changes, helping to stabilize the system.

Absolute refractory period

The period during which a neuron cannot fire another action potential, regardless of stimulus strength.

Local potentials

Small changes in membrane potential that occur in a localized area of the neuron.

All-or-none response

The principle that a neuron either fires an action potential or does not, with no intermediate states.

Velocity of an action potential

Factors that influence how fast an action potential travels along a neuron.

Self-propagating action potentials

The ability of action potentials to continue along the neuron without additional input.

Continuous conduction

A type of action potential propagation that occurs along unmyelinated axons.

Saltatory conduction

A type of action potential propagation that occurs along myelinated axons, jumping between nodes of Ranvier.

Nerve to effector synapses

Connections between neurons and their target effectors, such as muscles or glands.

Inhibitory post synaptic potentials (IPSP)

Changes in membrane potential that make a neuron less likely to fire an action potential.

Excitatory post synaptic potentials (EPSP)

Changes in membrane potential that make a neuron more likely to fire an action potential.

Temporal summation

The process where multiple signals arrive at a neuron in quick succession to increase the likelihood of firing.

Spatial summation

The process where signals from multiple neurons arrive at a neuron simultaneously to increase the likelihood of firing.

Neural circuits

Networks of interconnected neurons that process specific types of information.

Convergence of neural circuits

The process where multiple neurons synapse onto a single neuron.

Divergence of neural circuits

The process where a single neuron synapses onto multiple neurons.

Continuous conductance

occurs in unmyelinated axons and is continuous along the length of the axon

Neurolemmocyte

cell that myelinates neurons in PNS

Oligodendrocyte

cell that myelinates neurons in the CNS

Postsynaptic neuron

the neuron leaving a synapse

Presynaptic neuron

the neuron leading up to a synapse (the one coming into the synapse)

Relative refractory period

stage in the repolarization time of an action potential when an additional depolarization event is possible, but the threshold level will be higher than during a resting transmembrane potential

Saltatory conductance

movement of an action potential along a myelinated axon where the action potential only occurs at the nodes

Threshold

electrical value at which the voltage-gated sodium channels will be stimulated to open resulting in depolarization

Transmembrane potential

electrical charge difference across a membrane

Voltage-activated channels

channels that open and close based upon the charge difference across the membrane

Satellite cells

Glial cells that surround the cell bodies of neurons in the PNS and provide supportive functions.

Nuclei

Clusters of neuron cell bodies in the CNS.

Tracts

Bundles of axons in the CNS.

Ganglia

Clusters of neuron cell bodies in the PNS.

Nerves

Bundles of axons in the PNS.

Resting membrane potential

The electrical gradient established by the separation of charges across the plasma membrane, typically around -70mV.

Sodium-potassium pump

Transport mechanism that moves 3 Na+ out and 2 K+ into the cell, requiring ATP.

Graded potentials

Local changes in membrane potential that are reversible and decrease in strength over short distances.

Electrical synapses

Synapses where two cells are connected by protein channels (gap junctions) allowing fast, bidirectional communication.

Chemical synapses

Synapses that involve neurotransmitter release from the presynaptic neuron to the postsynaptic neuron across a synaptic cleft.

Neural integration

The process by which EPSPs and IPSPs are added together to determine if an action potential will be generated.