Chapter 8 Learning Objectives

8.1.1 Map the organization of the nervous system in Detail

Since brain function can not be predicted from neural anatomy

• CNS (central nervous system) = brain and spinal cord

• PNS (peripheral nervous system) = afferent (sensory) + efferent (motor)

  • Efferent → somatic (skeletal muscle) OR autonomic (smooth/cardiac/glands)

    • Autonomic → sympathetic + parasympathetic

• Enteric NS = GI tract, semi-autonomous (can function w/o CNS but regulated by ANS)

8.2.1 Draw and Describe the parts of a neuron and their functions

• Dendrites — receive input

• Cell body — integrates signals, contains organelles

• Axon hillock — trigger zone

• Axon — propagates AP

• Myelin — increases conduction speed

• Nodes of Ranvier — AP regeneration sites

• Axon terminal — releases neurotransmitter

Describe the parts of a synapse and their function

• Presynaptic cell — sends chemical signal

• Synaptic vesicles — store NT

• Synaptic cleft — extracellular gap

• Postsynaptic cell — receives signal via receptors

Name the types and functions of a glial cell

PNS:

• Schwann — form myelin and insulate neuron

• Satellite — support ganglia cell body

CNS:

• Oligodendrocytes: form myelin

• Astrocytes: BBB, ECF regulation, provide ATP source

• Microglia: immune defense

• Ependymal cells: produce CSF + stem cells

Explain in words how the GHK equation relates to the membrane potential of a cell

• GHK predicts membrane potential based on permeability and concentration of K+, Na+, and Cl-

• Vm reflects weighted contribution of each ion → mostly K+ at rest.

Explain relationship between the following terms: current flow

Current is created by flow of ions; it gets faster when more channels open

• Conductance (g) = ability to flow (open channels ↑g)

• Resistance (R) = opposition to flow (closed channels ↑R)

• Ohm’s law: I = g(Vm − Eion)

Compare and contrast graded potentials and action potential

Graded Potentials

Location: Dendrites/soma

Strength:Variable

Channels: Chem/Mech/Voltage

Distance:Decrease

Purpose: Summation; determine if an Action Potential is initiated

Action Potentials

Location: Axon

Strength: All or nothing

Channels: Voltage Gated only

Distance: Doesn’t lose strength when traveling

Purpose: Long distance signaling

Explain the changes in ion permeability and ion flow that take place during an action potential

• Neuron sits with Vm of -70 mV and change of permeability to Na or K alters

• Threshold = -55mV then Na rises

• voltage gated channel Na+ opens and Na+ rushes into cell (depolarizing)

• Peak: +30 mV, Na+ closes and K+ opens

• Falling phase: K+ rises and already open K+ gate rushed K+ OUT of cell (hyperpolarizing)

• Undershoot: -70mV, K+ keep going out

LO 8.3.5 - Describe and compare absolute and relative refractory period

• Absolute: No AP possible (Na+ inactivated)

  • Rising phase and beginning of falling phase

• Relative: Strong GP can trigger AP (hyperpolarized)

LO 8.3.6 Explain role of myelin in th the conduction of action potentials

• Reduces current leak

• Increases membrane resistance

• Enables saltatory conduction (jump node-to-node)

Speeds conduction dramatically

LO 8.4.1 Distinguish between electrical and chemical synapse

• Electrical: gap junctions, fast, synchronized; dosen’t have neuron

  • Postsynaptic cell membrane

• Chemical: NT release, slower, most common, axon terminal

  • Presynaptic Cell

LO 8.4.2 List and give examples of the 7 groups of neurocrine secretions

1. ACh

2. Amines (DA, NE, Epi, serotonin)

3. Amino acids (glutamate, GABA, etc.)

4. Peptides (substance P, endorphins)

5. Purines (ATP, AMP, adenosine)

6. Gases (NO, CO, H₂S)

7. Lipids (endocannabinoids)

LO 8.4.3 Describe different patterns for neurotransmitter synthesis, recycling, release and termination of action

• Synthesized in soma or terminal

• Packaged → vesicles

• Ca²⁺ triggers release

• Termination: enzymes, reuptake, diffusion

• Recycling: uptake → repackaging

LO 8.5.2 — Temporal vs spatial summation

• Temporal: same presynaptic neuron, high frequency

• Spatial: multiple neurons fire simultaneously

LO 8.5.3 — Presynaptic vs postsynaptic inhibition

• Presynaptic inhibition: blocks NT release at one axon terminal

• Postsynaptic inhibition: entire postsynaptic neuron inhibited (global)