Warm-Up Look up the definitions of the Central Nervous System vs. the Peripheral Nervous System. Compare these two types of nervous systems. What is a neuron? Draw and label its 3 main parts.

Warm-Up Draw and label the parts of a neuron. Describe saltatory conduction. Explain how a nerve impulse is transmitted across a neuron.

Warm-Up What happens at the synapse? Choose 1 neurotransmitter. Describe its action. What is the role of the following structures in the human brain? Brainstem Cerebellum Cerebrum Corpus callosum

Neurons, Synapses, and Signaling Chapter 37

You must know The anatomy of a neuron. The role of active transport in establishing the membrane potential of a neuron. The mechanisms of impulse transmission in a neuron. How depolarization of the presynaptic cell leads to the release of neurotransmitters. The events at the synapse that allow a presynaptic neuron to communicate with the postsynaptic cell.

Organization of the Nervous System Central nervous system (CNS) = brain & spinal cord Peripheral nervous system (PNS) = nerves throughout body Sensory receptors: collect info from world Eg. Rods and cones in eye, skin receptors, chemoreceptors, thermoreceptors Neuron = functional unit of nervous system

Types of Neurons Sensory neurons: info from body sensors  CNS Interneurons: connect sensory + motor neurons, or local connections between brain + spinal cord Motor neurons: CNS  body (effectors = muscles, glands) Nerves = bundles of neurons Contains motor neurons +/or sensory neurons

Sensory neurons Interneurons Motor neurons

Types of Neurons

Neuron = dendrite + cell body + axon

Neuron cell body: contains nucleus & organelles dendrites: receive incoming messages axons: transmit messages away to other cells myelin sheath: fatty insulation covering axon, speeds up nerve impulses synapse: gap between 2 neurons neurotransmitter: chemical messengers sent across synapse Glia: cells that support neurons Eg. Schwann cells (forms myelin sheath)

Schwann cells and the myelin sheath

BioFlix: How Neurons Work

Membrane Potential: difference in electrical charge across cell membrane

The Na+/K+ pump (using ATP) maintains a negative potential inside the neuron.

Action potentials (nerve impulses) are the signals conducted by axons Resting potential: membrane potential at rest; polarized Na+ outside, K+ inside cell Maintained by sodium-potassium pumps Voltage-gated Na+ channel = CLOSED Nerve impulse: stimulus causes a change in membrane potential Action potential: neuron membrane depolarizes All-or-nothing response Na+ channels open K+ channels open Na+ enters cell K+ leaves cell

Conduction of an action potential

Nerve Impulse Animation

Saltatory conduction speed: 120 m/sec Saltatory conduction: nerve impulse jumps between nodes of Ranvier (unmyelinated gaps)  speeds up impulse Saltatory conduction speed: 120 m/sec

Saltatory Conduction

BioFlix: How Synapses Work

Molecular Mechanism of Synaptic Function HHMI Animation (1:09 min) Molecular Mechanism of Synaptic Function

Signal Transmission

Neurotransmitter released at synapses Axon (presynaptic cell)  Synaptic cleft  Dendrite (postsynaptic cell)  Cell Response

Neurotransmitters Chemicals released from vesicles by exocytosis into synaptic cleft Diffuse across synapse Bind to receptors on neurons, muscle cells, or gland cells Broken down by enzymes or taken back up into surrounding cells Types of neurotransmitters: Excitatory: speed up impulses by causing depolarization of postsynaptic membrane Inhibitory: slow impulses by causing hyperpolarization of postsynaptic membrane

Examples of Neurotransmitters Acetylcholine (ACh): stimulates muscles, memory formation, learning Epinephrine: (adrenaline) fight-or-flight Norepinephrine: fight-or-flight Dopamine: reward, pleasure (“high”) Loss of dopamine  Parkinson’s Disease Serotonin: well-being, happiness Low levels  Depression GABA: inhibitory NT Affected by alcohol

Nervous System Disorders LSD/mescaline – bind to serotonin and dopamine receptors  hallucinations Prozac – enhances effect of serotonin by inhibiting uptake after release Morphine, heroin – bind to endorphin receptors  decrease pain perception Viagra – increase NO (nitric oxide) effects  maintain erection Alzheimer’s Disease (AD) – develop senile plaques, shrinkage of brain tissue

Mouse Party

Mouse Party Group Poster: Drug Neurotransmitter(s) Involved Action of Drug Summary Illustration: