1. Neurons, Synapses, and Signaling
Chapter 48
Neurons, Synapses, and Signaling

2. Information Processing
1) Detection of stimuli (senses) 2) Sensory input (from peripheral to central nervous system) 3) Integration 4) Motor output (effector)

3. Neurons Sensory – can detect changes in/out of the body
Interneuron – process the signal and pass it on to the next neuron
Motor – cause the response: move a muscle, stimulate gland, etc.

4. More Vocabulary
Ganglia – in peripheral nervous system, collection of neuron cell bodies
Nuclei – in the central nervous system, collection of neuron cell bodies

5. Parts of a neuron
Dendrites – receive signal, carry it towards cell body
Nodes of Ranvier – (PNS) the parts of the axon without myelin (between the myelin sheaths)
Cell body – have the nucleus and organelles
Neuroglia – (CNS)
Axon – carries impulse away from the cell body
Astrocytes: surround capillaries in the brain; blood brain barrier
Synapse – space between the neurons
Oligodendrocytes: myelin makers
Schwann cells – (PNS) makes myelin which insulates axon, helping the signal move faster

6. Vertebrates vs Invertebrates
Single longitudinal vertebrae
Spinal cord is dorsally located
Hollow spinal cord
Division of ganglia is not as apparent
Brain controls body more than the spinal cord
Paired longitudinal vertebrae
Spinal cord is ventrally located
Solid spinal cord
Division of ganglia is apparent
Spinal cord can control the body without brain

7. Nerve impulse Electrical signal that depends on the flow of ions
K+ (inside), Na+ (outside), Cl- (outside), Large anions like proteins (inside)
Resting Membrane Potential: -70 mV (more negative outside)
Cells have a higher permeability to potassium (more channels), so when potassium leaves, the inside will become more negative.
Sodium (which was on the outside) moves into the cell to balance the negative/positive difference, the inside becomes more positive.
Sodium-potassium pump restores to resting membrane potential

8. Continued
Two cells that can change membrane potential because of stimulus: neurons and muscle cells.
Hyperpolarizing stimuli- open potassium ion channels (becomes more negative)
Depolarizing stimuli- open sodium ion channels (becomes more positive)

9. All or none
Threshold: if you reach about -50mV, then you have an action potential
Action potential: maximum membrane potential, depolarized to the max
Stimulus
If gentle stimulus, then lower frequency of impulse firing
If harsh stimulus, then higher frequency of impulse firing

10. The whole process now…
Animation: on.com/sites/ /student_view0/chapter 14/animation__the_nerve _impulse.html

11. Transmission
The larger the diameter of the axon, the faster the transmission
Saltatory conduction – myelin aids in faster transmission, because the impulse “jumps” from Node to Node of Ranvier

12. Synapse
Electrical synapse – don’t really need to know, ex. Sticking finger into electrical outlet
Chemical synapse – Calcium ions (in pre-synaptic neuron) help move neurotransmitter in vesicles, neurotransmitters are dumped into the synaptic cleft, sodium ion channels open on post-synaptic neuron. (Animation)
Excitatory post-synaptic potentials = sodium ion channels open
Inhibitory post-synaptic potentials = potassium ion, chloride ion channels open
Summation:
Temporal – dependent on time, needs to be very quick to sum up
Spatial – dependent on space, multiple potentials come in and sum up (or cancel each other if there are excitatory and inhibitory potentials)
Figure 48.16

14. Neurotransmitters Acetylcholine Amino acids
Excitatory in muscles
Amino acids
GABA – most abundant inhibitory neurotransmitter
Endorphins – natural opiates, block out pain
Gases
Nitric oxide – ex. erections in penis