Topic 5: The Physical Basis of Neuronal Function

Neurons are what?

the nerve cells proper.

______ are highly specialized cells that conduct the nerve impulse.

Neurons

The Perikaryon is also called what?

cell body, soma

The Perikaryon (aka; cell body, soma) is ____________

uninucleated

Term for large clusters of RER and free ribosomes that are in Perikaryon.

Nissl or Chromatophilic Bodies

Nissl bodies serve to produce ________ to replace those lost from the nucleoplasm and to repair the nucleolemma.

proteins

What are bundles of intermediate filaments running between the Nissl bodies.

Neurofibrils or Neurofilaments

What do Neurofibrils or Neurofilaments do?

They serve to resist stress on the neuron.

Most perikarya are located in the ______ where they can be protected by the vertebrae and skull.

CNS

Most perikarya are located in the CNS where they can be protected by the ________ and skull.

vertebrae

Those perikarya located outside of the CNS, in the PNS, are grouped together and surrounded by c.t. forming what?

Ganglia

What typically serve as receptive sites, receiving the impulse and conducting it toward its perikaryon.

Dendrites

dendrites are more numerous and show a _______ degree of branching than Axons.

greater

Dendrites contain most of the ________ found in the cell body including extensions of the Nissl bodies.

organelles

What serve as impulse distributors sending the impulse from the perikaryon out to another cell.

Axons

typically axons will have a sheath of insulating material called what?

Myelin

Myelin is produced by ________ cells of the nervous system.

supporting

Axons branch to a much ______ extent than do dendrites but they may have some branches present

lesser

What are rare branches which branch off at 90 angles to the axon?

Axon Collaterals

Many branches occurring at the terminal end of the axon.

Telodendria

Rare branches on Axons.

Collaterals

At the end of the telodendria will be Axon __________.

Terminals

These are knob-like endings of the telodendria.

Axon Terminals (aka; end bulbs, axonal boutons)

Axon terminals synapse with the dendrites of other neurons contain vesicles containing Neurotransmitters called what?

Synaptic Vesicles

Nervous system function: Sensory Input

Using millions of sensory receptors to monitor stimuli in both the external and internal environments.

Nervous system function: Integration

the processing and interpretation of the sensory input.

Nervous system function: Motor Output

the activation of “effector organs” to respond to stimuli.

The effector organs include our what?

muscles and glands

The CNS typically consists of what?

the brain and spinal cord.

The location of the spinal cord will vary between animal groups: Vertebrates

dorsal

The location of the spinal cord will vary between animal groups: Invertebrates including arthropds and annelids.

ventral

What interprets the sensory input, integrates it, and determines a motor response.

Central Nervous System (CNS)

The ____ carries information to and from the ______.

PNS, CNS

What carries sensory information to the CNS from the sense receptors.

The Sensory or Afferent Division

What carries motor information from the CNS from the sense receptors.

The Motor or Efferent Division

What send the impulse towards the CNS from sensory receptors of the PNS.

Sensory Neurons (aka; Afferent Neurons)

What carries the impulse away from the CNS out to the effector organ.

Motor Neurons (aka; Efferent Neurons)

“effector organ” is often, but not limited to, a what?

muscle

What lie between the sensory and motor neurons.

Interneurons (aka; Association Neurons)

Interneurons (aka; Association Neurons) are located only in what?

Central Nervous System

Most neurons are what?

interneurons

What assist in the functioning of the nervous system.

Supporting Cells

The spike initiating zone is usually located on the swollen base of the axon, where it connects to the Perikaryon, called what?

Axonal Hillock

The __________ integrates the incoming signals to determine if it will initiate its own signal.

spike-initiating zone

The action potential will travel the length of the ______, from the spike initiating zone to the axon terminals.

axon

These passive electrical properties:

Resistance and Capacitance

A measure of the degree to which conductor opposes an electric current through that conductor.

Resistance

The ability of a body to store an electrical charge.

Capacitance

The term for this loss in signal strength is what?

Decrement

the ion channels of the axon selectively transmit ________ to allow for conduction of the action potential.

Na+ and K+

The flow of information from a sensory neuron responding to a stimulus to an interneuron, or series of interneurons, to a motor neuron which stimulates an effector organ is termed what?

Neuronal Circuit

Neurons exchange information at a point called what?

Synapse

The neuron that sends the impulse to the synapse is called what?

Presynaptic Neuron

The neuron that receives the impulse at the synapse is called what?

Postsynaptic Neuron

The synapse is usually a Chemical Synapse, but some are ______ Synapses

Electrical

Chemical synapses use ________ to convey information from the presynaptic neuron to the postsynaptic neuron.

Neurotransmitters

The cell membrane of the postsynaptic neuron’s dendrites and perikaryon have _________ channels.

ligand-coated ion

What is the electrical potential difference between two points or the difference in electrical potential energy of a unit charge transported between two points.

Voltage (aka; Electrical Potential Difference)

Passive electrical properties of a cell membrane include:

Capacitance and Conductance

which is a measure of the ability of a cell to store an electrical charge.

Capacitance

which is a measure of the ease at which an electrical current passes through a cell.

Conductance

The passive electrical properties of a cell correspond to particular membrane ________.

elements

The __________ of animal cell membranes is impermeable to ions.

phospholipid bilayer

The cell membrane serves as both an insulator and a diffusion barrier to the movement of certain ions. This allows the cell membrane to serve as what?

electrical capacitor

A ________ forms when two conductors are separated by an insulator (the bilayer).

capacitor

The amount of charge stored on the two sides of the capacitor is measured in what?

farads (F)

A farad is a unit of electrical what?

capacitance

The unit of one farad is defined as the capacitance of a capacitor across which, when charged with one _____ of electricity, there is a potential difference of one volt.

coulomb

What _________ measures of the ability of a cell to store an electrical charge.

Membrane Capacitance

By definition a capacitor is a passive two terminal electrical component used to _____ energy electrostatically.

store

The two terminals are separated by a dielectric/insulator which is __________ of the membrane.

phospholipid bilayer

What is the difference in the electrical potential between the extracellular and intracellular environments.

Membrane Potential

For most animal cells the membrane potential is between ___ mV and ____ mV.

–40, –80

If ion channels cause the membrane potential to be less negative (ex; shift from – 60 mV to – 20 mV) the membrane is said to be what?

Depolarized

If ion channels cause the membrane potential to be more negative (ex; shift from – 60 mV to - 70 mV) the membrane is said to be what?

Hyperpolarized

Ion channels are pore ________ transmembrane proteins.

forming

Ion channels demonstrate _________ in that they only one or very few specific ions to cross.

Ion Selectivity

What are activated by changes in the electrical membrane potential near the ion channel.

Voltage-gated Channels

These channels are responsible for the action potential in neurons.

Voltage-gated Na+ Channels

Type of Channels always open.

Leak

These leak channels are selective for what?

K+

Leak channels are responsible for maintaining the ______ potential of the cell.

resting

Class of transmembrane proteins that open to allow ions (such as sodium, potassium, and chloride to cross in response to a neurotransmitter binding to them.

Ligand-gated Channels

Membrane _________ is a measure of a membrane’s permeability to ions/charge.

conductance

Membrane _______ is a measure of a membrane’s impermeability to ions/charge.

resistance

The relationship between resistance, voltage, and current across a membrane is described by what?

Ohm’s Law

Ohm’s Law states that the voltage drop across a membrane by a current passing through it is directionally _______ to the current multiplied by the resistance of that membrane.

proportional

What is the voltage drop across membrane (in volts)

Delta Vm

what is is the current across membrane (in amperes)

Delta I

what is the electrical resistance of the membrane (in ohms)

R

______ Resistance is the total resistance encountered by a current flowing into or out of a cell.

Input

What is an energy transfer to an electrical circuit per unit of electrical charge (measured in volts).

The electron motive force

The electron motive force is the energy per unit charge that is ______ by an electrical source.

imparted

The __________ allows you to calculate the equilibrium potential for single ions.

Nernst Equation

The Nernst Equation is an equation for calculating electrochemical ________ conditions.

equilibrium

The _________ can calculate the steady state potential for multiple ions.

Goldman Equation

The advantage of the Goldman Equation over the Nernst Equation is?

Nernst Equation only deals with one type of ion per calculation.

NB-> _______ means being able to cross a semipermeable membrane.

Permeant

In addition, the _______ Equation can account for differences in ion concentrations across a cell membrane that are due to active transport.

Goldman