Download Deconstructing the Nervous System

Chapter 48
Neurons
 Single, functional unit of nervous tissue
 Communication between
 Long-distance is electrical

Pulse to receive, transmit, and regulate
 Local is chemical
 One cell to another
 Communication within
 Movement of ions = electrical
 Groups organized into brains
 Smaller = ganglia
Information Processing
 Sensory input (to)
 Sensors
 External or internal info
 Integration
 Immediate context
 Experience
 Motor output (from)
 Effector cells
 Muscle or gland activity
Vertebrate Nervous System
Nervous System
Integration
Info in & out
Central Nervous
System (CNS)
Brain
Peripheral Nervous
System (PNS)
Spinal Cord
Sympathetic
(Fight or flight)adrenergic
Autonomic
(involuntary)
Somatic
(voluntary)
Parasympathetic
(Rest and digest)cholinergic
Incredible Edible Neuron
 1 cookie
 1 long licorice




piece
5-8 short
licorice
pieces
4 fruit roll-up
pieces
Scoop of
sprinkles
1 gobstopper
Neuronal Types
Resting Membrane Potential
 Difference in electrical
charge across PM
 K+ and Na+ ions
 Not sending signals
 K + higher in, Na + higher
out
 Na + /K + pumps maintain
(3 out/2 in)
 Charge moves with ions
 Selectively permeable
channels
 Many K + open, few Na +
 -60 mV - -80mV
Graded Responses
 Magnitude varies with
stimulus strength
 Not actual signal
 Hyperpolarization
 Inside more (-)
 (+) ions out or (-) in
 Depolarization
 Inside less (-)
 Na+ channels open
Action Potentials
 Massive change in
membrane potential
 Positive feedback signal
 Carry information
 All-or-nothing
 Threshold (-55mV)
reached
 Magnitude independent
of strength
Generating Action Potentials
rising
falling
resting
undershoot
Propagating Action Potentials
 Capable of regeneration
 Identical at all positions
 Travels in 1 direction
down axon only
 Refractory period when
Na+ channels inactive
Action Potential Speed
 Diameter and resistance
 Myelin sheath
 Nodes of Ranvier limit exposed axon

AP’s not generated = saltatory conduction
Synapses
 Information, not AP, is transmitted
 Electrical (escape)
 Chemical (most)
 Neurotransmitter into synaptic vesicles at terminal
 AP signals exocytic release
 Diffuse across synaptic cleft
 End result varies
Neurotransmitter Classes
 Acetylcholine
 Excite muscle cells, inhibit cardiac
 Nicotine and botulinum (botulism and botox)
 Biogenic amines
 Epi & NE: emotions, dreaming, & awaking
 DA & 5-HT: sleep, temperature regulation, and emotion

Prozac & SSRI’s
 Amino acids
 GABA (inhibitory) & glutamate (excitatory)
 Neuropeptides
 Supstance P: perception of pain & endorphins
 Gases