BIOL 230-Case Neurons

Lines of Communication Processing • The cone snail kills prey with venom – Ganglia: simple clusters of neurons that disables neurons – Brains: more complex organization of neurons

back to Cell Communication • How does the toxic peptide work?

Neuron Glial cells

Myelin sheath Neuron

Axon Axon

1 BIOL 230-Case Neurons

Axon terminal Axon terminal Dendrite Cell body Dendrite Cell body

Schwann cell

Node of Ranvier Axon hillock

Axon Axon

Na+ K+

Postsynaptic Synaptic +50 neuron terminals of pre- synaptic K+ 5 mM 0 neurons Na+ 150 mM Threshold (mV) -50 1 Membrane potential Resting potential -100 Time OUTSIDE OF CELL Sodium Potassium channel channel 5 µm 5 K+ 140 mM Na+ 15 mM INSIDE OF CELL Inactivation loop 1 Resting state

Figure 48.11-5

Na+ Na+ Na+ K+ K+ K+

4 Falling phase of the action potential +50 3 Rising phase of the action potential +50 3 Rising phase of the action potential +50 Action Action potential potential 3 3 0 0 0

Threshold Threshold Threshold 4 (mV) 2 (mV) 2 (mV) 2 -50 -50 -50 1 1 1 Membrane potential Membrane potential Membrane potential 2 Depolarization Resting potential 2 Depolarization Resting potential 2 Depolarization Resting potential -100 -100 -100 Time Time Time OUTSIDE OF CELL Sodium Potassium OUTSIDE OF CELL Sodium Potassium OUTSIDE OF CELL Sodium Potassium channel channel channel channel channel channel

INSIDE OF CELL INSIDE OF CELL INSIDE OF CELL Inactivation loop Inactivation loop Inactivation loop 1 Resting state 1 Resting state 1 Resting state

2 BIOL 230-Case Neurons

Figure 48.11-5

Na+ Axon Axon K+ Action Plasma Action Plasma potential membrane potential membrane 4 Falling phase of the action potential 3 Rising phase of the action potential +50 Action Na+ Cytosol Na+ Cytosol potential 3 0 Action Threshold 4 +

(mV) potential 2 K -50 1 5 1 Na+ Membrane potential 2 Depolarization Resting potential -100 Time OUTSIDE OF CELL Sodium Potassium K + channel channel

INSIDE OF CELL Inactivation loop 1 Resting state 5 Undershoot

Axon

Action Plasma membrane Synaptic vesicle potential containing neurotransmitter Na+ Cytosol

Action

K + potential

Na+

K + Action K + potential Ligand-gated ion channels

Na+

K +

Parasympathetic division Sympathetic division Action on target organs: Action on target organs: Constricts pupil Dilates pupil of eye of eye What is the effect of Stimulates salivary Inhibits salivary gland secretion gland secretion Constricts Sympathetic Relaxes bronchi ganglia bronchi in lungs Cervical in lungs Parasympathetic Sympathetic (1) Cobratoxin Prevents binding of Slows heart Accelerates heart Ach Stimulates activity Inhibits activity of of stomach and stomach and intestines Ach ¯Heart rate intestines Thoracic Parasympathetic Sympathetic Stimulates activity Inhibits activity Ach ¯ Heart rate ­ Heart rate of pancreas of pancreas Adrenalin Calming Excitatory Stimulates Stimulates glucose Adrenalin ­Heart rate gallbladder release from liver; Lumbar inhibits gallbladder Stimulates adrenal medulla Calming Excitatory Ach is parasympathetic neurotransmitter Promotes emptying Inhibits emptying of bladder of bladder Promotes erection Sacral Promotes ejaculation of genitalia Synapse and vaginal contractions

3 BIOL 230-Case Neurons

Effect on muscles of What if…

• Which is more dangerous? (2) Mamba Blocks Ca2+ channels (2) Mamba Blocks Ca2+ channels Latrotoxin Cobratoxin Conus Conus LD50=20–40 µg/kg LD50=0.1 mg/kg

What if… Effect on muscles What if…

(3) Arabica Binds parasympathetic (4) Dinoflagellate Activates Na+ channels (5) Pufferfish Competitive inhibitor neurotransmitter for Na+ channels

Parasympathetic Sympathetic

Ach ¯ Heart rate ­ Heart rate Adrenalin Calming Excitatory

Effect on heart rate Effect on muscles Effect on heart rate

(6) Botulium Blocks Ach release (7) Krait Blocks Ach receptor (8) Scorpion Blocks K channels Rattlesnake Sea snake open Parasympathetic Sympathetic

Ach ¯ Heart rate ­ Heart rate Adrenalin Calming Excitatory

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Effect on Ach Effect on action potential

(9) Funnel spider Opens K channels Tetanospasmin Blocks GABA release (10) Poison arrow frog Keeps Na channels open

(11) Rays Phosphodiesterase (12) Deadly nightshade Inhibits Ach receptor (13) Calabar bean Inhibits cholinesterase (Atropa belladonna) (Physostigma venenosum)

Parasympathetic Sympathetic Parasympathetic Sympathetic

Ach ¯ Heart rate ­ Heart rate Ach ¯ Heart rate ­ Heart rate Adrenalin Calming Excitatory Adrenalin Calming Excitatory

(14) Curare bark Inhibits Ach receptor (15) Ergot Binds adrenalin (Strychnos toxifera) (Claviceps purpurea) receptors

Parasympathetic Sympathetic

Ach ¯ Heart rate ­ Heart rate Adrenalin Calming Excitatory

Parasympathetic Sympathetic

Ach ¯ Heart rate ­ Heart rate Adrenalin Calming Excitatory

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