Campbell Biology Chapt 48 Part I

Front 1

Neurons

Back 1

Neve cells

Transmit info within body

2 types of signaling:

1. Electrical signals (long distance) and 2. chemical signals (short distance)

Front 2

Ganglia

Back 2

Clusters of neurons

Complex organization of neurons is a brain

Interpreting signals in the nervous system involves sorting a complex set of paths and connections

Front 3

Dendrites

Back 3

Highly branched extensions the revive signals from other neurons

Front 4

Most of organelles in neurons are in

Back 4

Cell body

Front 5

Axon

Back 5

Typically much longer extension that transmit signal to other cells at synapses

Front 6

Axon hillock

Back 6

Cone shaped base of axon

Where cell body turns into the axon

Important bc this is where the cell decides if it is going to send message or not

Front 7

Synapse

Back 7

Space between a axon and another cell

Synaptic terminal of one axon passes info in form of chemical message (NTs)

Front 8

Presynaptic cell vs postsynaptic cells

Back 8

Giver to receiver

Can be a neuron, muscle, or gland cell

Front 9

Glia or glial cells

Back 9

Nourish neurons or insulated cells (myelin sheath)

Form blood brain barrier

Will clean up NTs to modify signaling

Outnumbers neurons like 10:1

Front 10

3 stages of processing info

Back 10

1. Sensory input: sensory neurons (external or internal stimuli such as stretch receptors in bladder or light tough and smell)

2. Integration: interneurons (analyze and interpret)

3. Motor output: motor neurons (signals to motor cells to contract or glandular activity)

Front 11

Nervous system

Back 11

Central nervous system (CNS): integration takes place, includes brain and spinal cord

Peripheral nervous system (PNS): carries info in and out of CNS. Neurons of PNSwhen bundled together form nerves (sensory and motor)

Front 12

Membrane potential

Back 12

A voltage (difference in electrical charge) across its plasma membrane

Front 13

Resting potential

Back 13

The membrane potential of a neuron not sending a signal (-60 to -80 mV)

Front 14

Action potential

Back 14

Changes in Membrane potential

This is the signal for transmitting or processing info

Front 15

Formation of resting potential

Back 15

In most at resting potential:

Concentration of K is higher inside cell and concentration of Na is higher outside the cell

These concentration gradients represent chemical potential energy

Front 16

Sodium potassium pumps

Back 16

Use energy of ATP to maintain these K and Na gradients across the plasma membrane

Pumps 3 Na into extracellular space and 2 K into intracellular space

Sets up concentration gradient

Front 17

Ion channels

Back 17

Opening in plasma membrane for a specific ion across the membrane converting chemical potential to electrical potential

A neuron at rest, has many open K channels and fewer Na channels open (K diffuses out of cell)

This contributes to -70 mV

Front 18

Build up of negative charge inside cell

Back 18

Equals major source of membrane potential

Front 19

Equilibrium potential

Back 19

Membrane voltage for a particular ion at equilibrium and can be calculated using the Nernst equation

At equilibrium, electrical/chemical gradients are balanced

Equilibrium potential of K is negative (-90mV) while EQ of Na is positive (+62mV)

Front 20

A

Back 20

A

Front 21

Voltage Gated ion channels and ligand ion gated channels

Back 21

Open or close in response to a stimuli (in voltage, respond to change in voltage)

Ligand ion channel: something binds and opens or close it

Front 22

Hyperpolarization

Back 22

Increase in magnitude of the membrane potential

Brings the potential towards -90mV (= K Equilibrium)

When gated potassium channels open, K diffuses out making inside of cell more negative

Front 23

Depolarization

Back 23

A reduction in the membrane potential

Opening other channels (like sodium)

Brings potential to +62mV (= Na equilibrium)

Front 24

Graded potentials

Back 24

Changes in polarization where the magnitude of the change varies with the strength of the stimulus

These are not action potentials but do have effect on generation of nerve cells

As long as Sub threshold, little effect

Front 25

Action potentials

Back 25

If graded potentials cross threshold, then action potential occurs

Depolarization shifts the membrane potential sufficiently leading to change in membrane voltage

All or nothing, Transmits signals over long distances, constant magnitude

Results from voltage gated ion channels opening or closing after hitting -55 mV (threshold)

Front 26

Generation of action potential (5 steps)..step 1

Back 26

Resting state

Gated Na and K ion channels are closed. More open K than Na

Leak channels are open

Front 27

Step 2

Back 27

Depolarization

Action potential is generated

Voltage gated Na channels open first and Na flows into cell

Front 28

Step 3

Back 28

Rising phase

Threshold is crossed and membrane potential increases

Gets more positive inside the cell and when it hits -55mV

Front 29

Step 4

Back 29

Falling phase

Never hit Na +62 bc..

Voltage gated ion channels inactivate (plug hole to stop Na ions coming in)

voltage gated K channels open ad K flows out of out of cell

Front 30

Step 4

Back 30

Falling phase

Never hit Na +62 bc..

Voltage gated ion channels inactivate (plug hole to stop Na ions coming in)

voltage gated K channels open ad K flows out of out of cell

Front 31

Step 5

Back 31

Undershoot phase

Membrane permeability to K is at first higher than at rest

Voltage gated K channels close

Resting potential is restored

Front 32

Refractory period

Back 32

After action potential, 2nd cannot happen due to “ball and chain” on voltage gated Na channels remain inactivated

Front 33

Conduction of action potential

Back 33

Axon hillock (site of generated action potential)

An electrical current depolarizes the neighboring region of the axon membrane

Travel in only one direction: toward synaptic terminals

Inactivated Na channels behind the zone of depolarization prevent action potential from traveling backwards (refractory period)

Front 34

The rate which action potentials are produced in a neuron is proportional to...

Back 34

Input signal strength

ie: sound is triggered or not (all or nothing), but higher volume of sound triggers faster action potential

Front 35

Mutations in gated ion channels

Back 35

Gated ion channels and action potentials are important in nervous system

Mutation in these genes that encode ion channels can lead to disorders of nervous system, brain, muscle, heart

ie: mutation in Na channels in skeletal muscle can create myotonia (too much contraction) or in brain can lead to epilepsy

Front 36

The fatter the axon diameter...

Back 36

The faster the action potential is

Front 37

Myelin sheath

Back 37

In vertebrates, axons are insulated by myelin which causes an action potentials speed to increase

Made by glia (oligodendrocytes in CNS and Schwann cells in PNS)

Deficiency in forming myelin sheath leads to multiple sclerosis and Guilin barre

Front 38

Nodes of ranvier

Back 38

Gaps in melon sheath (exposed plasma membrane) where voltage gated Na channels are restricted too

Allows for saltatory conduction

Front 39

Saltatory conduction

Back 39

Jumping btw nodes

Rapid signal conduction inside myelinated portion of axon

Makes the conduction move faster bc not taking time to open more Na channels