Chapter 3 pt 1

Question 1

neurophysiology

Answer 1

the study of life processes within neurons that use electrical and chemical signals

Question 3

How can information be processed by the nervous system?

Answer 3

• For info to be processed by the nervous system, it must first be gathered (ex. from the sensory system) and then relayed from neuron to neuron
• Each neuron in the chain (circuit) sequentially processes the signals given to them

Question 4

Intercellular communication

Answer 4

• signals travel from one cell to another
• movement of info between cells/neurons

Question 5

Intra-cellular communication

Answer 5

• signals travel within a single cell
• movement of info within cells/neurons

Question 6

Inter-cellular transmission

Answer 6

• Info is transmitted through circuits from neuron to neuron to neuron
• this happens through neurotransmitters, which are chemical messengers
• the sensory neurons release a nt that will then bind to the receptors of the receiving neuron and activate it, this goes down a chain

Question 7

What is a neurotransmitter?

Answer 7

a chemical messenger between neurons

Question 8

Intra-cellular transmission

Answer 8

• info is received- dendrites
• info is integrated and processed- axon hillock
• info is transmitted/conducted- axon
• action potential

Question 9

What is an action potential?

Answer 9

a rapid electrical signal that travels along the axon of a neuron

Question 10

What does the membrane of the neuron look like?

Answer 10

• neurons are surrounded by extracellular fluid, separated from the intracellular fluid by a phospholipid bilayer
• Neuron membranes has a phospholipid bilayer (two layers w phosphate groups w lipid tails that are kind of joined together)… the tails are hydrophobic and are fats
• membrane also contains embedded proteins w hydrophilic (outside) part and hydrophobic (inside) part

Question 11

How do electrical forces act on the membrane?

membrane voltage differential

Answer 11

• The is a membrane voltage differential due to inside of cell being more negatively charged than the space immediately outside of the cell
• This property is not unique to neurons (ex. cardiac cells)
• Ions are dissolved in intracellular fluid, separated from the extracellular fluid by the cell membrane

Question 12

Neuron at rest (not receiving input)

Answer 12

• Concentration of ions is different inside vs. outside the cell
• Na+, K+, Ca2+, and Cl- are very important ions to neurons, as well as negatively charged proteins (most heavily negatively charged particle inside of a neuron)
• Ions are dissolved in intracellular fluid, separated from the extracellular fluid by the cell membrane
• Ions are hydrophilic and lipophobic
• Na+, Ca2+, Cl- are found primarily outside the cell
• K+ and many negatively charged proteins found inside the cell

protiens allow ions to go inside and outside of the cell

Question 13

What two forces cause ions to move through a neuron/ what are the push/pull forces on molecules?

Answer 13

• Concentration force/gradient: ions move from high conecntration to low concentration (think of diffusion through a semi-permeable membrane)
• Electric force: opposite charges attract while like charges repel (think polarity)
• These two forces can collaborate or oppose one another

Question 14

Resting membrane potential

Answer 14

• Rest/resting means in the absence of any other external input (waiting around for things to happen)
• Neuron is around -60 to -70 mV, which is more negative than the outside

Question 15

How is the resting membrane potential maintained?

Answer 15

• Sodium-potassium pumps
• The pump sits in the membrane and uses energy to push ions against their concentration gradient
• Na+/K+=ATPase pump moves sodium and potassium ions… moves 3Na+ ions out and 2K+ ions in for every molecule of energy that is utilized

Question 16

Ions can move across the membrane…

Answer 16

• If the membrane becomes transiently permeable, ions will move in the direction governed by concentration and electrical forces
• Will move down their electro-chemical gradient but charge doesn’t matter as much as concentration
• This is possible because of the opening and closing of ion-selective channels that span the membrane
• K+ reaches equilibrium when the movement out is balanced by the movement in

Question 17

Ligand-gated/ionotropic ion channels

Answer 17

• Axon terminals of other cells secrete chemicals that can regulate the opening of channels
• Channels are found on the membrane just like the ion channels were, generally found in the synaptic areas
• When NT are released, they bind to these channels and open them, allowing ions to flow through

ex. when acetylcholine molecules are present in the synapse the channel will open and ions will be able to flow through

Question 18

What happens when ligand-gated/ionotropic receptors open?

Answer 18

• Ions flow through the respective channel
• The membrane potential around the channel changes
• The membrane potential change travels with the ion
• Ions flow and then travel- as they move, their effect (de- or hyper- polarization) weakens

Question 19

What happens upon a channel opening?

Answer 19

• If cations enter the cell, the membran voltage potential becomes less negative. Depolarizes (less polarized) with excitatory postsynaptic potential
• If anions enter the cell (or cations exit), the membrane voltage potential becomes more negative. Hyperpolarizes (becomes more polarized) with inhibitory postsynaptic potential. IPSP can stop the neuron from firing or make it even more negative than it was before

Question 20

Summation and Integration

Answer 20

• Dendrites may receive contacts from many different neurons
• Summation is the job of combining these signals together
• Integration is the job of translation those signals into a decision to send an output to the next neurons in the chain (circuit) or not: axon hillock does this

Question 21

Two types of summation

Answer 21

Spatial summation- summing of potentials coming from different parts of the cell
Temporal summation- summing of potentials that arrive at the axon hillock at different times

Question 22

What are the neurons summing to?

Answer 22

• Adding up many inputs
• If the sum reaches the threshold potential, the neuron will actually fire (an action potential will begin)
• The axon potential begins at the axon hillock (initial segment of the axon)
• The signal will begin traveling actively through the cell, including down the axon

Question 23

What are action potentials?

Answer 23

• Brief (transient) but large chages in the membrane potential
• They originate at the axon hillock and propagate along the axon

Question 24

What is the action potential threshold?

Answer 24

• The voltage (-40 to -55 mV) required by the membrane to reach before an action potential is generated

Question 25

Depolarization

Answer 25

occurs when the interior of the cell becomes less negative (step 2)

Question 26

Repolarization

Answer 26

* occurs as the membrane potential becomes negative (Step 3 after depolarization)

Question 27

Hyperpolarization

Answer 27

* Occurs when the interior of the membrane potential becomes even more negative than the resting state, relative to the outside. * During this phase the cell is ina refractory period- it cannot generate another action potential

Question 28

How is the strength of a stimulus definied?

Answer 28

By the number of action potentials generated (NOT by the peak height of the action potential!!)