NERVOUS SYSTEM

On womens' history month (March), remembering Dian Fossey, known for studies of gorillas, conservation efforts, and confrontation with poachers. She was murdered on Dec. 26, 1985.

Campbell and Reece Chapter 48
There is considerable interest at the organismal level (later in this chapter), but this lecture will start with cell physiology

Since metazoans have division of labor (with different organs), there must be a means of integration:
(1) hormones (covered already); and
(2) nervous system
hormones are wasteful since not all cells are target
N.S. more discreet

100,000,000,000 (100 billion) neurons (many connections [synapses])
TRANSPARENCY Fig. 48.13 b lots of connections per cell

TRANSPARENCY Fig. 48.1 - stimulus -> organism -> response
Energy-(Receptor-Nervous System-Muscle, Gland)-Effect

Lots of cell types - Golgi technique shows all the detail of the processes and branches of the cell
TRANSPARENCY Fig. 48.4

TYPICAL CELL-spinal motor neuron TRANSPARENCY (Fig. 48.2)
The cell has a nucleus but there is no mitosis (in the adult mammalian CNS = brain & spinal cord).
But, of course, the nucleus orchestrates protein synthesis which is especially important in such an elaborate cell.
Dendrite, soma, axon, synapse, vesicle - integration of information
The giant axon of the squid has been especially useful in research as to how axons quickly carry electrical potential changes over substantial distances

Membrane review - TRANSPARENCY Fig. 5.12 phospholipids
TRANSPARENCY Fig. 8.6 membrane fluid mosaic of lipids and proteins

measuring potentials with electrodes
The oscilloscope (computer), alternatively the polygraph, is a means of measuring voltage as a function of time.
TRANSPARENCY (Fig. 48.6 a) Voltage is potential difference (-70 mV inside negative), and think of "potential" in the physics sense as "potential energy" for now.

TRANSPARENCY Fig. 48.7
Na+ is relatively concentrated outside the cell
K+ is relatively more concentrated inside the cell
Energy (delivered by ATP) pumps these ions TRANSPARENCY Fig. 8.15
TRANSPARENCY (Fig. 44.12) salt pumping was important in osmoregulation; this reminder is that marine (salt water) birds pump out salt through nasal gland.

The imbalance of potassium through the membrane which is selectively permeable to K+ creates the Resting potential -70 mV (inside negative)
Basically, all cells, not just nerve cells, have such a potential
Receptors make little potentials called generator potentials
Synapses (cell connections) make small potentials which are graded potentials
Nerve and muscle are "excitable" (responsive, a basic property of life), and, in particular, they generate big all-or-none potentials called action potentials or spikes which travel down axons real fast.
TRANSPARENCY Fig. 48.9
Na+ permeability increases - action potential (spike)
Channels open and close
all-or-none - binary code +55 mV

TRANSPARENCY Fig. 48.10
action potential triggers the action potential ahead of it on the axon, thus it propagates
there is a refractory period - moves one way -
think of a fuse as an analogy

TRANSPARENCY Fig. 48.11 - Myelin speeds up action potential to 120 m/s = 269 mph
(slower than light or electricity, but adequate considering body size)
think of sticks of dynamite set at distances each setting each other off rather than a slow fuse
Polio damages myelin in peripheral nervous system
Multiple sclerosis (Anette Funicello, Montell Williams, Richard Prior) damages myelin in the central nervous system
Schwann cell makes myelin in thePNS
Oligodendrocyte makes myelin in the CNS

Neurochemistry

Axons carry all or none spikes - binary code of n.s.
vs. Synapse (and receptors) -graded potentials- excitation and inhibition are then integrated.
TRANSPARENCY Fig. 48.12 of vesicles and synapse
Receptor molecules- very important- here the receptor is a channel, but there are receptors which work like the membrane receptors for hormones which work through a second messenger system.
Ca2+ comes in to trigger synaptic vesicle release blocked by botulism
(Ca2+ is very important, recall there are 3 hormones, parathormone, thyrocalcitonin and vitamin D to regulate calcium)
TRANSPARENCY (Fig. 48.13 a) [again] there are excitatory and inhibitory synapses
Here's how they work
TRANSPARENCY Fig. 48.14
EPSP=excitatory postsynaptic potential, IPSP= inhibitory postsynaptic potential

TRANSPARENCY TABLE 48.1
Transmitters: (like hormones, more discreet) amines, peptides
also amino acids, nucleotides, nitric oxide, carbon monoxide
Synthesis, breakdown, reuptake, diffusion

For instance, look back to the hormone chapter (TRANSPARENCY Fig. 45.12) to show synthesis of norepinephrine (noradrenalin) and epinephrine (adrenalin) from the amino acid tyrosine. Note that there are some steps missing in this diagram (tyrosine -> l-DOPA -> dopamine -> norepinephrine -> epinephrine), though the chemical formulas are correct and informative.

Transmitter, location -drug (disease)
Acetylcholine (parasympathetic nervous system, muscle) atropine blocks, nicotine stimulates, organophosphates (nerve gas) blocks break down
Noradrenalin (sympathetic nervous system), caffeine & amphetamine (speed) potentiate
Dopamine (Parkinsons**, Schizophrenia)
Serotonin - LSD, Prozac used for depression, the "soma" (Aldus Huxley - Brave new world) of psychiatry
Glutamate (amino acid used in brain) (Toxicity from over stimulation)
Gamma amino butyric acid (an unuaual amino acid) - inhibitory
Endorphins, Enkephalins (peptide) opiates*
? cannabis
NO nitric oxide

*opium, poppy, morphine, codeine, heroin, narcotic analgesics,
strategy of look for receptors, what is "endogenous" transmitter

**a common health problem usually affecting people over 50, usually not genetic, causes tremor, lose emotion (affect), stone (expressionless) face, Mohammed Ali, Michael J. Fox, Pope

Organization of the nervous system


stimulus - response TRANSPARENCY to show reflexes like the knee-jerk reflex (Fig. 48.3)
Reflex arc- synaptic delay
Gray- cells, synapses; White-myelinated axons
reflex overseen by volition
afferent - toward the CNS, efferent- away from the CNS

Vertebrate CNS (brain and spinal cord)
TRANSPARENCY (Fig. 48.19 c)
- PNS - Sensory
Motor systems- Somatic for Striated (Skeletal) muscle
TRANSPARENCY Fig. 48.18 Autonomic (for smooth muscle and glands) - Sympathetic Parasympathetic (Details are discussed extensively)
TRANSPARENCY Neural crest cell -> sympathetic neuron and adrenal medulla cell (shows developmentally the obvious functional relatedness of sympathetic neurons and adrenalin secreting hormonal cells)

Here is a good place for TRANSPARENCY Fig. 48.17 - peripheral n.s. has sensory and motor portions. Motor has somatic and autonomic. Autonomic has sympathetic and parasympathetic.

Brain function (these statements will be oversimplifications)
back to TRANSPARENCY 48.19 d
medulla - fundamental functions like respiration
cerebellum - motor control
hypothalamus - motivation
thalamus - relay for sensory signals
TRANSPARENCY Fig. 48.27 - limbic system - smell, emotion, learning, very complex
cerebral cortex TRANSPARENCY Fig. 48.24
localization of function- like motor, vision, audition, speech

Review of some fundmental points:
Brain - O2 dependence (CPR)
glucose dependence (insulin shock)
no mitoses (why stroke is so damaging)

In finishing, let me get a little philosophical:

Scientists tend to be somewhat reductionistic (emphasizing a "nothing but" attitude) and mechanistic (describing mechanisms from molecular to cellular). At the other extreme, holism contends that the whole is more than the sum of the parts. While the components are awesome, the richness of human experience would seem to be more than just a lot of sodium channels. In general, the human beings that live inside scientists' brains sometimes believe in something more, but many of them do not express their convictions with much eloquence. One exception in my opinion is Roger Sperry who won a Nobel Prize in Physiology and Mecicine in 1981 for "functional specialization of the cerebral hemispheres," but who also wrote some papers on the mind-brain and on free will. In explaining how phenomena may not be entirely explained by the simple physical laws, he espouses a philosophy of somewhat like holism in which "emergent properties," still lawful but beyond laws like conservation of momentum come about as more complex organisms evolve:

A fundamental premise of materialistic science holds that a complete explanation of brain function is possible in purely objective physiological and biophysical terms.

In other words, in the world view of materialist science, real mental freedom to act and choose is only an illusion, and the whole value-rich world of inner subjective experience gets set aside as some kind of passive, impotent by-product, an epiphenomenal correlate, or just an interior aspect of the one prime material brain process.

The resultant view of human nature and the kinds of values that emerge are hardly uplifting.

All of us would prefer to think that we are more than mere puppets of environmental reinforcement and our brain's physiology and that the inner experience we live with most of our waking life is something real and of some material consequence.

At stake are central key concepts that directly involve fundamental convictions regarding the nature of man's inner being, physical reality, the meaning of existence, and related matters of ultimate concern.

...recall that a molecule in many respects is the master of its inner atoms and electrons. The latter are hauled and forced about in chemical interactions by the overall configurational properties of the whole molecule. At the same time, if our given molecule is itself part of a single-celled organism such as paramecium, it in turn is obliged, with all its parts and partners, to follow along a trail of events in time and space determined largely by the extrinsic overall dynamics of Paramecium caudatum. When it comes to brains, remember that the simpler electric, atomic, molecular, and cellular forces and laws, though still present and operating, have been superceded by the configurational forces of higher-level mechanisms. At the top, in the human brain, these include the powers of perception, cognition, reason, judgment, and the like, the operational, causal effects and forces of which are equally or more potentent in brain dynamics than are the outclassed inner chemical forces.

Evolution keeps complicating the universe by adding new phenomena that have new properties and new forces that are regulated by new scientific principles and new scientific laws--all for future scientists in their respective disciplines to discover and formulate. Note also that the old simple laws and primeval forces of the hydrogen age never get lost or cancelled in the process of compounding the compounds. They do, however, get superceded, overwhelmed, and outclassed by the higher-level forces as these successively appear at the atomic, the molecular and the cellular and higher levels.

References:

Mind-brain interaction: mentalism, yes; dualism, no Neuroscience 5, 195-206, 1980
Changing concepts of consciousness and free will Perspectives in Biology and
Medicine 20, 1976, 9-19
Changing priorities Ann Rev. Neurosci, 4, 1-15, 1981

Neuroscience at SLU is centered in Medical school departments of Anatomy and Neurobiology and Pharmacology-Physiology. I teach a Neuro course in Biology. Dr. Anch in Psychology teaches 4 courses in physiological psychology relevant to Neuroscience, PSY-A415-01: Science of Sleep, PSY-A513-01: Advanced Physiological Psychology, PSY-A413-01: Physiological Psychology, and PSY-A414-01: Drugs and Behavior. Dr. Churchill in Psychology is also a neuroscientist, and he teaches PSYA669-03 (Psychopharmacology). Dr. Spaziano's CH-A445 Principles of Medicinal Chemistry is also somewhat relevant to this topic. There is a philosophy professor, Dr. Terzis, who teaches a relevant course PL A-482-01 "Biology and Mind" which is relevant to this topic.

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