action potentials animal systems

MO Figure

Action Potentials

Mike Hollingshead/Science Source

Figure 1

Membrane ion channels

Include sodium (Na+), potassium (K+), and calcium (Ca2+) ion channels.

Figure 2

Membrane potentialElectrical potential difference across the cell membrane caused by different concentrations of K+, Na+, and Cl- ions on each side of the membrane. Membrane potential of neurons is usually between -60 and -80 mV.

Figure 2a

Figure 2b

Figure 3

The action potentialSmall changes in membrane potential (graded potentials) can be depolarizing or hyperpolarizing. A depolarizing potential that exceeds a threshold becomes an action potential.

Figure 4

The action potential

During an action potential, membrane potential changes as a result of ion flow through voltage-gated Na+ channels, voltage-gated K+ channels, and the Na+/K+ pump.

Figure 4

Figure 5

The membrane depolarization during an action potential triggers action potentials in adjacent regions of an axon. Depolarization spreads down the length of the axon as a result.

The action potential

Figure 5a

Figure 5b

Figure 5c

Figure 6

Saltatory conduction

Some axons are myelinated by insulating glial cells. Ion channels are only present at the nodes of Ranvier between glia. Electrical current jumps from node to node, increasing the speed of neural transmission.

Figure 6

Figure 6a

Figure 6b

MO Figure

Neurons and SynapticCommunication

Photo Researchers, Inc./Science Source

Figure 1

Figure 2

Postsynaptic potentialsA signal from a presynaptic neuron may induce an inhibitory (IPSP) or excitatory (EPSP) potential in the postsynaptic neuron. An IPSP causes a hyperpolarization and makes a new action potential less likely to form. An EPSP causes a depolarization and increases the likelihood of a new action potential.

Table 2a

Neurotransmitters

Table 2b

Table 2c

Figure 3

GABA

g-aminobutyric acid (GABA) is an inhibitory neurotransmitter that triggers opening of Cl- channels in the postsynaptic

neuron, which hyperpolarizes its membrane.

MO Figure

Structure and Function of theVertebrate Nervous System

Bartolommeo Eustachi, Tabulae Anatomicae, 2nd edition. Amsterdam, 1722.

Figure 1

The nervous system

Subdivided into the central nervous system (CNS) and peripheral nervous system (PNS).

Figure 2

White and gray matter

CNS contains both white and gray matter. White matter consists of myelinated axons. Gray matter consists of

unmyelinated axons, dendrites, and cell bodies.

Figure 2a

Figure 2b

Figure 3

The peripheralnervous system (PNS)

Includes sensory and motor neurons and the autonomic nervous system (ANS).

Figure 4

The autonomicnervous system

Contains antagonistic sympathetic and parasympathetic divisions.

Figure 5

Regions of the brain

Subdivided into forebrain, midbrain, and hindbrain regions.

Figure 6

The cerebral cortex

Includes the frontal, parietal, temporal, and occipital lobes.

Figure 7

MO Figure

The Human Brain:Language, Memory, and fMRI

Photo via Wikimedia Commons. Originally published by Fowlers & Wells.

Figure 1

Brain language centers

Broca’s area is important for speech. Wernicke’s area is important for language comprehension.

Figure 2

Functional MRI (fMRI)

Colors indicate sites of brain activity.

© 2008 Nature Publishing Group deCharms, R. Applications of real-time fMRI. Nature Reviews Neuroscience 9, 720–729 (2008) doi:10.1038/nrn2414. Used with permission.

Figure 3

Functional MRI (fMRI)

These images were collected during a visual memory test. Red/yellow areas indicate regions with increased activity, and blue indicates decreased activity. Yellow indicates moderate activity.

© 2009 Nature Publishing Group Dickerson, B. and Eichenbaum, H. The Episodic Memory System: Neurocircuitry and Disorders. Neuropsychopharmacology 35, 86–104 (2009) doi:10.1038/npp.2009.126. Used with permission.

Figure 4

Protein and brain activity

fMRI revealed that high-protein breakfasts (HP, dark blue) reduce brain activity in regions associated with food motivation and reward pathways compared to normal-protein breakfasts (NP, light blue).

Figure 5

Aplysia

This sea slug with large, easily accessible neurons, is a good model organism in neurobiology to study the links between

specific neurons and behavior.

Martin Shields/Science Source.