DO NOW

DO NOW

On your paper, label the following parts of the neuron (number you DO NOW sheet: 1, 2, 3, etc.). Do as many as you can!

1

2

3

4

5

67

8

DO NOW

1. Dendrite

5. Axon

6. Myelin Sheath

4. Node of Ranvier

3. Schwann’s Cells

2. Axon terminals8. Cell body

7. Nucleus

Neuroscience and BehaviorPart II

AP Psychology

Ms. Desgrosellier

10.15.2009

Objectives: SWBAT describe how nerve cells communicate. SWBAT explain how neurotransmitters affect behavior,

and outline the effects of acetylcholine and the endorphins.

SWBAT explain how drugs and other chemicals affect neurotransmission, and describe the contrasting effects of agonists and antagonists.

SWBAT describe the nervous system’s two major divisions, and identify three types of neurons that transmit information through the system.

How Neurons Communicate

Neurons are packed so tightly that even with a microscope it is hard to see where one stops and another begins

How Neurons Communicate

Santiago Ramon y Cajal (1852 – 1934) was the first scientist to describe individual nerve cells and concluded that each neuron functioned independently

Sir Charles Sherringotn (1857 – 1952) first noticed that it took a signal a surprisingly long time to travel up a neural pathway, and concluded that there must be an interruption in transmission.

How Neurons Communicate

Synapse: the junction (gap) between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron. The tiny gap at this junction is called the synaptic gap or cleft.

How does information cross this gap?

Neurotransmitters

When the action potential reaches the knoblike terminals at an axon’s end, it triggers the release of neurotransmitters.

Neurotransmitters: chemical messengers that cross the synaptic gaps between neurons. When released by the sending neuron, neurotransmitters travel across the synapse and bind to receptor sites on the receiving neuron, thereby influencing whether that neuron will generate a neural impulse.

Neurotransmitters

They cross the gap in 1/10,000th of a second and bind to receptor sites on the receiving end like a key in a lock.

They unlock tiny channels, allowing ions to enter the receiving neuron and thereby exciting or inhibiting its readiness to fire.

Neurotransmitters are reabsorbed by the sending neuron by reuptake.

How Neurotransmitters Influence Us

Neurotransmitters (NT) affect our moods, memories, and mental abilities.

Are certain NT found only in specific places? What role do they play in influencing us?

Particular neural pathways in the brain may only use one or two NT.

Particular NT may have specific effects on behavior and emotion.

Acetylcholine

Acetylcholine (ACh): a NT that enables learning and memory, and also triggers muscle contraction.

It is also the messenger at every synapse between a motor neuron and a skeletal muscle.

When ACh is released to our muscle cells, the muscle contracts. If ACh is blocked, the muscles cannot contract.

How Neurotransmitters Influence Us

Candace Pert and Solomon Snyder (1973) attached a radioactive tracer to morphine, showing how it is taken up in an animal’s brain.

They discovered that the opiate drug that elevates mood and eases pain bound to receptors in areas linked with mood and pain sensations.

Why would the brain have “opiate receptors” if there weren’t naturally occurring opiates in the brain?

Endorphins

Endorphins: “morphine within” – natural, opiate-like NT linked to pain control and to pleasure.

They are released in response to pain and exercise.

How Drugs and Other Chemicals Alter Neurotransmission

How do artificial opiates (fake endorphins) affect the brain? If they make you feel good, is it a bad idea to take them?

One problem is that when the brain is flooded with opiate drugs, like heroin and morphine, it may stop producing its own natural opiates.

When the drug is withdrawn, the brain is left with no opiates, natural or unnatural.

Mood-altering drugs, like alcohol, nicotine, and heroin, share a common effect: they trigger unpleasant, lingering aftereffects.

How Drugs and Other Chemicals Alter Neurotransmission

Some drugs affect communication at the synapse, by either exciting or inhibiting neurons’ firing.

Agonist molecules excite a neuron and may be similar enough to the NT to mimic its effect or it may block a NT uptake.

E.g. Black widow spider venom: floods synapse with ACh, causing violent muscle contractions, convulsions, and possible death.

How Drugs and Other Chemicals Alter Neurotransmission

Antagonists inhibit – it is a drug molecule that inhibits a NT’s release.

E.g. Botulin can cause paralysis by blocking ACh from the sending neuron.

Or it could be mistaken for a natural NT and occupy its receptor, and could block its effect.

E.g. Curane occupies and blocks ACH receptor sites, leaving the NT unable to affect the muscles, causing paralyzation.

How Drugs and Other Chemicals Alter Neurotransmission

Neurotransmitter research is leading to new therapeutic drugs to treat depression, schizophrenia, and other disorders.

Blood brain barrier (BBB): enables the brain to keep out unwanted chemicals circulating in the blood.

E.g. Can’t give an Parkinson’s Disease patient dopamine for their tremors because it can’t cross the BBB, but you can give them L-dopa, a raw material that the brain converts to dopamine.

DO NOW

Assemble your homework packets to be checked.

Write on your DO NOW sheet: how do neurons communicate across the gap between them (and what is that gap called?)

The Nervous System

Neurons make up our nervous system, our body’s electro-chemical information network made up of all the nerve cells of the peripheral and central nervous systems.

The Nervous System

Two parts:• Central Nervous

System (CNS): the brain and the spinal cord

• Peripheral Nervous System (PNS): the sensory and motor neurons that connect the central nervous system (CNS) to the rest of the body.

The Nervous System Nerves: neural “cables”

containing many axons. These bundled axons, which are part of the PNS, connect the CNS with muscles, glands, and sense organs

E.g. the optic nerve bundles a million axon fibers into a single cable that carries information from each eye to the brain.

The Nervous System

Three types of neurons carry information through the nervous system:• Sensory neurons: neurons that carry

incoming information from the sense receptors to the CNS

• Motor neurons: neurons that carry outgoing information from the CNS to the muscles and glands.

The Nervous System

Three types of neurons carry information through the nervous system:• Interneurons: CNS neurons that internally

communicate and intervene between the sensory inputs and motor outputs.

• We have a few million sensory and motor neurons, but billions and billions of interneurons.

Homework

Read pgs. 54 – 62