Copyright Notice! This PowerPoint slide set is copyrighted by Ross Koning and is thereby preserved for all to use from plantphys.info for as long as that.

Copyright Notice!This PowerPoint slide set is copyrighted by Ross Koning and is thereby preserved for all to use from plantphys.info for as long as that website is available. Images lacking photo credits are mine and, as long as you are engaged in non-profit educational missions, you have my permission to use my images and slides in your teaching. However, please notice that some of the images in these slides have an associated URL photo credit to provide you with the location of their original source within internet cyberspace. Those images may have separate copyright protection. If you are seeking permission for use of those images, you need to consult the original sources for such permission; they are NOT mine to give you permission.

Biology:life study of

What is Life?Cellular Structure: the unit of life, one or many

Growth: cell enlargement, cell number

Evolution: long term adaptation

Behavior: short term response to stimuli

Reproduction: avoid extinction at death

Metabolism: photosynthesis, respiration, fermentation, digestion, gas exchange, secretion, excretion, circulation--processing materials and energy

Movement: intracellular, movement, locomotion

Properties of Life

Neuron

Structure and Function

The leaves of Mimosa pudica are touch responsive using pulvini (pressure-based movement)

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This stimulus (touch) causes an action potential!

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The neural network in a Hydra

This system is not centralized and thus local stimulation gives mostly local response.

©1996 Norton Presentation Maker, W. W. Norton & Company

A slightly more centralized nerve system in jellyfish:

Neural ring around opening of medusa is the “central” system for coordinating swimming motions

Peripheral nerves connect to cnidoblast, so when a nematocyst is fired, a signal goes back to the nerves in the mouth to direct it to potential prey

©1996 Norton Presentation Maker, W. W. Norton & Company

In flatworms there is an evolutionary progression from:

…a nerve net as in the hydra.

…to a cephalized system with two major longitudinal nerves.

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The nerve system in round worms has less than 300 nerves, but a complex map with a centralized area and a large ventral nerve

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In earthworms, the two ganglia are dorsalized, but connect to the major ventral nerve cord.

The first few segments have many sensory neurons

The rest of the segments have individualized nerve connections

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This is the sea slug, Aplysia, a marine mollusc

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The morphology of a sea slug:

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The sea slug’s gills are vulnerable to fish attack at the siphon:

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After the touch by the fish, the siphon is “instantly” withdrawn into the mantle:

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This cartoon shows the nerve system that operates in this touch response:

Sensory nerves connect sensors to motor neurons at the ventral nerve cord…with sufficient signal, the motor neurons fire, muscles contract and the siphon and gills are withdrawn.

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The squid giant neuron has been heavily studied:

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Insect larvae have double-ganglia in the anterior segments and a dual ventral nerve cord extending to the posterior segments

http://www.anselm.edu/homepage/jpitocch/genbios/33-33-InsectAnatomy-L.gif

Insects have a ventral nerve cord is a double item with ganglia along its length. A large ganglion in the head segments serves as the brain.

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The basic form of neurons (nerve cells):

These are invertebrate neurons.

You can tell because the cell body is outside the path of electrical flow from dendrite to axonic synapse.

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In a simple system, many sensory neurons receive touch information. Some send “I am touched” signals, others are sending “I am not touched” signals.

The interneuron receives the conflicting information and, with sufficient positive inputs,responds by sending a signal to the target motor neuron

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The interneuron can receive inputs from many sensory or other neurons.

The sensory synaptic terminals can connect with the dendrites or the cell body of the interneuron.

Again, when sufficient information exceeds a threshold, the interneuron sends a signal down its axon

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Here is a SEM of a cell body in Aplysia with many synaptic connections:

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These synaptic connections are indirect:

The electrical stimulus travels down the axon.

The synaptic vesicles release transmitter substances across the synaptic cleft.

Receptors in the post-synaptic cell membrane receive the transmitters and respond…

…if a nerve cell, by sending an electrical action potential down the cell

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Here is the TEM of the synapse, corresponding with the cartoon:

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GABA

sero-tonin

acetyl choline

Differential responses to inputs is explained by different transmitter substances being released

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In vertebrate neurons, the cell body is IN the information pathway:

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A motor neuron synapses on several muscle fibers (cells)

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The neuro-muscular junction: Acetyl Choline

presynaptic membrane

postsynaptic membrane

synaptic cleft

vesicles containing acetyl choline

exocytosis

H3C-COO-CH2-CH2-N+(CH3)3

muscle cell responds with contraction

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A pectoral reflex arc:

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A pelvic reflex arc:

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Reflex arcs are connected to the CNS too: OUCH! (late!)

The beauty of the reflex is that you take defensive action BEFORE it registers in your brain that you have a problem!

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Nor-epinephrine

Fright

Fight

Flight

Acetyl-choline

Calming

Autonomic Nerve System-“self-naming” systemOperates without conscious thoughtInvolves opposing nerve systems instead of opposing muscles

HO-HO-

-CHOH-CH2-NH2 H3C-COO-CH2-CH2-N+(CH3)3