Chapter 4.1: Neural Conduction and Synaptic Transmission

Dopamine

Substantia nigra make a chemical called ___, which they deliver to another part of the brain (striatum). the amount of they can deliver goes down (Parkinson’s disease).

Membrane potential

• understanding how neurons work—and how they malfunction is

• Electrical difference inside and outside of the cell - intracellular and extracellular, there is a positive and negative charged ions.

Dopamine

Substantia nigra make a chemical called ___, which they deliver to another part of the brain (striatum). the amount of they can deliver goes down (Parkinson’s disease).

Membrane potential

• understanding how neurons work—and how they malfunction is

• Electrical difference inside and outside of the cell - intracellular and extracellular, there is a positive and negative charged ions.

Potassium and Sodium Ions

Two elements that are involved in nerve impulse conduction

Sodium Ions (Na)

are greater in the extracellular fluid (outside)

Potassium (K)

is greater in intracellular fluid (inside)

electrode inside and outisde

To record a neuron’s membrane potential, it is necessary to position the tip of ____ of the neuron.

Zero

When both electrode tips are in the extracellular fluid, the voltage difference between them is

70 mV

• when the tip of the intracellular electrode is inserted into a neuron, a steady potential of about ___ is recorded

• This indicates that the potential inside the resting neuron is about ___ less than that outside the neuron.

Positivity outside and negativity inside

Neuron is said to be in resting membrane potential, when there is ____ and ____ the cell.

Resting potential

• The RMP or polarized state is measured to be -70 mV intracellularly

• This steady membrane potential of about −70 mV is called the

Polarized

In its resting state, with the −70 mV charge, a neuron is said to be ___

Ions

The salts in neural tissue separate into positively and negatively charged particles called

Sodium ions (Na+)

In resting neurons, there are more ___ ions outside the cell and more ions inside.

Potassium ions (K+)

In resting neurons, there are more ions outside the cell and ____ more ions inside.

Ion channels

• These unequal distributions of Na+ and K+ ions are maintained even though there are pores, called

• which is for the passage of particular ions.

Electrostatic pressure and random motion

There is pressure on Na+ ions to enter the resting neurons. This pressure comes in two types:

Electrostatic pressure

• opposite charges attract. The -70 mV charge attracts the positively charged Na+ ions into resting neurons.

Random motion

• The pressure from ___ for Na+ ions to move down from areas of high concentration to areas of low concentration

Closed

The sodium ion channels in resting neurons are ___, thus greatly reducing the flow of Na+ ions into the neuron.

Open

The potassium channels are ___ in resting neurons, but only a few K+ ions exit

Concentration gradient

All ions are in constant random motion. This indicates the movement of the ions in

Alan Hodgkin and Andrew Huxley

• became interested in the stability of the resting membrane potential (1950s)

• Sodium–Potassium pumps

Sodium-Potassium pumps

three Na+ ions inside the neuron for two K+ ions outside.

Neurotransmitters

When neurons fire, they release from their terminal buttons chemicals called ___ and interact with receptor molecules on the receptive membranes of the next neurons.

Depolarize

• the receptive membrane (decrease the resting membrane potential, from −70 to −67 mV).

• lesser negativity - more positive

Hyperpolarize

• it (increase the resting membrane potential, from −70 to −72 mV). Inside becomes more negative than -70mV.

• (Negativity increases - More Negative)

Polarized

• Resting membrane potential (-70mV inside).

Postsynaptic potential

• Neuron transmits message to other.

• It refers to the electrical changes in the postsynaptic neuron as a result from the release of neurotransmitters molecules by presynaptic neuron.

Excitatory or inhibitory

Neurotransmitter and postsynaptic potential can be either

Excitatory Postsynaptic Potentials

they increase the likelihood that the neuron will fire.

Inhibitory Postsynaptic Potentials

they decrease the likelihood that the neuron will fire.

Axon hillock

EPSP and IPSP travels very fast in the axon but as they travel, they become weaker and may not reach the ____ – weak signals, small PSP and strong signals, large PSP.

Less negative

• Any changes in the charge of postsynaptic neuron will fire a neural signal.

• If the chances increased, inside of the neurons become

More positive

• Any changes in the charge of postsynaptic neuron will fire a neural signal.

• If the chances decrease, inside of the neurons become

Rapid and decremental

The transmission of postsynaptic potentials has two important characteristics.

Synapse

is a small gap at the end of a neuron that allows a signal to pass from one neuron to the next.

Action potential

• are nerve signals.

• When neurons transmit signals through the body, part of the transmission process involves an electrical impulse called an

• This process occurs during the firing of the neurons, allows a nerve cell to transmit an electrical signal down the axon toward other cells.

• This sends a message to the muscles to provoke a response.

Depolarization

• Generation is triggered by voltage change in axon hillock. If excitation reached, ion channels opened and allow diffusion of ions.

• Ions increases rapidly the positivity of the cell which caused ___ – nerve cell has an activity already.

• During this period, no other stimulus will be accepted – ability to respond temporarily lost.

Repolarization

bring back the nerve cell in polarized state or RMP

Opening of ion channels of K

Depolarization followed by repolarization (bring back the nerve cell in polarized state or RMP) is caused by the

Resting Potential

When opened, diffusion of potassium happen.

• Increase in cell negativity to go back

Irritability

During repolarization, ___ is being gained so nerve cell stimulates again – stronger.

Negative ions

Charged ions maintain the positive and negative charge balance and the ____ inside the cell are unable to cross the barrier.

Rest

When at ___, the cell membrane of the neuron allows certain ions to pass through while preventing or restricting other ions from moving.

Sodium channels

play a role in generating the action potential activating a transmission along the axon.

Refractory period

• After the neuron has fired, there is a ____ in which another action potential is not possible - nerve cell is unable to fire an action potential

• During this time, the potassium channels reopen and the sodium channels close, gradually returning the neuron to its resting potential.

• Once the neuron has "recharged," it is possible for another action potential to occur and transmit the signal down the length of the axon.

Axon initial segment

Action potentials were generated at the

Absolute Refractory Period

a brief period of about 1 to 2 milliseconds after the initiation of an action potential during which it is impossible to elicit a second one.

Relative Refractory Period

• it is the period during which it is possible to fire the neuron again but only by applying higher-than- normal levels of stimulation.

• Action potential travels in one direction

• Rate of neural firing is related to the stimulation intensity

The refractory period is responsible for two important characteristics of neural activity:

Levodopa

• treatment for Parkinson’s disease

• in pill form

• should be taken along with carbidopa to prevent nausea.

Reptilian stare

prevalent symptoms in Parkinson’s disease characterized by widely opened, unblinking eyes

Neural communication

• How signals are send from cell to cell

• Powerful impact of the message to transmit in other parts of the body.

Reuptake

Improperly absorb neurotransmitter will be absorb again is called