2. Learning Objectives
1. Name and describe the parts of a neuron and explain their functions
2. Describe the supporting cells of the central and peripheral nervous
systems and explain the blood-brain barrier.
3. Briefly describe the neural circuitry responsible for a withdrawal reflex
and its inhibition by neurons in the brain.
4. Describe the measurement of the action potential and explain the
how the balance between the forces of diffusion and electrostatic
pressure is responsible for the membrane potential.
5. Describe the role of ion channels in action potentials and explain the
all-or-none law and the rate law.
6. Describe the structure of synapses, the release of the
neurotransmitter, and the activation of postsynaptic receptors.
7. Describe postsynaptic potentials: the ionic movements that cause
them, the processes that terminate them, and their integration.
8. Describe the role of autoreceptors and axoaxonic synapses in
synaptic communication and describe the role of neuromodulators
and hormones in nonsynaptic communication
3. Cells of the Nervous Sytem
Neurons
Receive and
transmit information
Glia
Support neurons
Do NOT transmit
information
Endothelial Cells
Capillaries
3
4. Cells of the Nervous System
Neurons transmit information
Classification
Sensory Neurons
Motor Neurons
Interneurons
6. Neurons
Multipolar neuron
one axon and many
dendrites
most common in CNS
Bipolar neuron
one axon and one dendrite
sensory systems
Unipolar
one stalk that divides into two
branches
Somatosensory system
16. Measuring Electrical Potentials of
Axons
Electrode
used to apply
electrical stimulation
and record electrical
potentials.
Microelectrode
used to record
activity of individual
neurons.
17. Measuring Electrical Potentials of
Axons
Membrane Potential
electrical charge
across a cell
membrane
difference in electrical
potential inside and
outside the cell.
Resting Potential
membrane potential of
a neuron at rest
approximately -70 mV
Outside the cell
Inside the cell
19. The Membrane Potential: Balance
of Two Forces
Diffusion
Molecules move
from regions of high
to low
concentrations
Electrolytes
Ions
Cations (+)
Anions (-)
Electrostatic
pressure
Like charges repel,
opposite charges
attract
The force of diffusion
The force of electrostatic
pressure
20. The Membrane Potential: Balance
of Two Forces
High Concentration
Sodium (Na+)
Chloride (Cl-)
Low Concentration
Potassium (K+)
High Concentration
Potassium (K+)
Low Concentration
Sodium (Na+)
Chloride (Cl-)
Extracellular Fluid Intracellular Fluid
22. The Membrane
Ion channel
A specialized protein molecule that permits specific
ions to enter or leave the cell.
Voltage-dependent ion channel
An ion channel that opens or closes according to the
value of the membrane potential.
25. Conduction of the Action
Potential
All-or-none law
Rate Law
Speed of signal
Saltatory Conduction
26. Communication Between
Neurons
synaptic transmission
the transmission of messages from one neuron to
another through a synapse
these messages are carried by neurotransmitters,
chemicals diffuse across synapses.
31. Release of Neurotransmitters
Synaptic vesicles
A small, hollow, beadlike structure found in the
terminal buttons
contains molecules of a neurotransmitter
fuse with the membrane and then break open,
spilling their contents into the synaptic cleft.
32. Activation of Receptors
Neurotransmitter binds with postsynaptic
receptor
Opens neurotransmitter dependent ion
channels (allows ions to flow in or out)
Ionotropic receptor (fast and direct)
Metabotropic receptor (slow and indirect)
G Protein
Second messenger
33. Postsynaptic Potentials
Excitatory postsynaptic potential (EPSP)
Depolarizes postsynaptic membrane
Inhibitory postsynaptic potential (IPSP)
Hyperpolarizes postsynaptic membrane
Effect likelihood a neuron will fire an action
potential
34. Termination of Postsynaptic
Reuptake of neurotransmitter by transporter
molecules
Enzymatic deactivation
Acetylcholine
Acetylcholinesterase
35. Neural Integration
Involves the effects of EPSP’s and IPSP’s on
the likelihood a neuron will fire an action
potential
36. Autoreceptors
Presynaptic receptors
respond neurotransmitters released by that
neuron
Metabotropic
regulate internal processes like neurotransmitter
synthesis
37. Axoaxonic Synapses
Alter amount of neurotransmitter released
Presynaptic inhibition
Presynaptic facilitation
Pictured here is (a) a bipolar neuron, primarily found in sensory systems (for example, vision and audition) and (b) a unipolar neuron, found in the somatosensory system (touch, pain, and the like).
