NEURO

Campbell Chapters 48-49

The Nervous System

• Three phrases:
• Sensory input
• Classification/integration
• Motor output

Central Nervous System (CNS)

• Processing
• Brain + Spinal Cord

Peripheral Nervous System (PNS)

• Transporting
• All others (neurons that carry info to CNS)

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Neuron

Axon Hillock

Synapse

Glia - Supporting Cells

• Outnumber neurons
• Oligodendrocytes & Schwann cells: myelination
• Ependymal cells: cerebrospinal fluid circulation
• Astrocytes: information transfer, ion concentrations, blood flow, blood-brain barrier, stem cell
• Radial glia: important in embryonic development, stem cell
• Microglia: immune cells

Brain Anatomy

Membrane Potential

• Charge difference across a membrane
• Potential Energy
• Resting Potential (-60/-80 mV)
• Sodium-Potassium pump
• Ion channels
• Leak channels
• Voltage-gated ion channels

Equilibrium Potential

• Balance of chemical gradient and charge gradient
• E_ion - membrane voltage at equilibrium
• Nernst Equation
• @37ºC, +1 charge

E_ion =

62mV

( )

log

[ion]_outside

[ion]_inside

Changes in Membrane Potential

• Neuron + stimulus = change
• Depolarization - more positive
• Hyperpolarization - more negative
• Graded potential
• Action potential

depolarizations

Action Potential

• “All or nothing”
• Constant magnitude, goes to completion
• Threshold (~-55 mV)
• When voltage-gated ion channels open
• Refractory period

Action Potential

Adaptations

• Faster reaction time = higher fitness

Invertebrates: wider axon → less resistance

Vertebrates: myelin sheath

• Oligodendrocyte - CNS
• Schwann cell - PNS
• Nodes of Ranvier
• Saltatory Conduct

Synapses (Cont.)

Electrical

• Gap junctions
• Coordinated unvaried response
• Ex. Squid escape, Heartbeat

Chemical:

• Neurotransmitters

Postsynaptic Potentials

• Neurotransmitters bind to ligand-gated ion channel → permeable to varying kinds of ions
• Excitatory Postsynaptic Potential (EPSP)
• Inhibitory Postsynaptic Potential (IPSP)
• Summation:
• One EPSP is typically not strong enough to reach the threshold
• Temporal - same synapse
• Spatial - different synapses

Neuronal Plasticity

• Neuronal connections/strength adaptation
• Important in memory/learning
• Long Term Potentiation (LTP): increase in strength of a synaptic transmission
• Glutamate, NMDA, AMPA

Neurotransmitters

Acetylcholine:

- Muscles, memory, learning

- Acetylcholinesterase

- Sarin gas, botulinum toxin, nicotine is similar

Amino acids:

GABA: inhibitory in brain (diazepam)

Glutamate: excitatory neurotransmitter for long-term memory storage

Glycine: inhibitory

Biogenic amines:

- Derived from amino acids

Norepinephrine:

- tyrosine

- excitatory

Dopamine:

- tyrosine

- sleep, mood, etc.

- lack is a cause of Parkinson’s Disease

Serotonin:

- tryptophan

- sleep, mood, etc.

Neuropeptides:

Endorphins:

- decrease pain

- opioids

Gases

Nitrous oxide (NO)

- dilates blood vessel

- Viagra

Carbon monoxide (CO)

- poison

Divisions of the Peripheral Nervous System

Autonomic Nervous System: involuntary, homeostatic

• Sympathetic, parasympathetic, enteric

Somatic Nervous System: voluntary actions, skeletal muscles

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“Rest and Digest” vs. “Fight or Flight”

Disorders

Schizophrenia:

- distorted perceptions of reality

- blocking of dopamine receptors alleviates symptoms

Depression:

- depressed mood for an extended period of time

- Major depressive disorder, most common nervous system disorder

Bipolar Disorder:

- Manic-depressive disorder

- manic and depressive phases

- biogenic amines treatment

Alzheimer’s:

- age-related

- dementia

- amyloid plaques, neurofibrillary tangles

- deterioration of brain tissue

Parkinson’s:

- age-related

- motor-disorder

- treatments include increasing dopamine secretion

Drug Addiction:

- take advantage of the brain’s reward system

- dopamine receptors

- stimulants, depressants

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Skeletal Muscles

THANKS!

Questions?

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