Neural and Hormonal Systems Will Explain Why We FEEL…… Pain Strong Sick Nervous

Overview Course introduction Neural Processing: Basic Issues Neural Communication: Basics Vision, Motor Control: Models

It all Starts with the Neuron

Neuron Structure Neurons do NOT touch each other- the space in between is call the synapse.

Synapse site of communication between two cells formed when an axon of a presynaptic cell “connects” with the dendrites of a postsynaptic cell

Synapse axon of presynaptic neuron dendrite of postsynaptic neuron bipolar.about.com/library

Synapse a synapse can be excitatory or inhibitory arrival of activity at an excitatory synapse depolarizes the local membrane potential of the postsynaptic cell and makes the cell more prone to firing arrival of activity at an inhibitory synapse hyperpolarizes the local membrane potential of the postsynaptic cell and makes it less prone to firing the greater the synaptic strength, the greater the depolarization or hyperpolarization

How a Neuron Fires It is an electrochemical process Electrical inside the neuron Chemical outside the neuron (in the synapse in the form of a neurotransmitter). The firing is call Action Potential.

The All-or None Response The idea that either the neuron fires or it does not- no part way firing. Like a gun Take a look -

Steps of Action Potential Dendrites receive neurotransmitter from another neuron across the synapse. Reached its threshold- then fires based on the all-or-none response. Opens up a portal in axon, and lets in positive ions (Sodium) which mix with negative ions (Potassium) that is already inside the axon (thus Neurons at rest have a slightly negative charge). The mixing of + and – ions causes an electrical charge that opens up the next portal (letting in more K) while closing the original portal. Process continues down axon to the axon terminal. Terminal buttons turns electrical charge into chemical (neurotransmitter) and shoots message to next neuron across the synapse.

Action Potential Take a look -

How Neurons Communicate

Transmission of information Information must be transmitted within each neuron and between neurons

The Membrane The membrane surrounds the neuron. It is composed of lipid and protein.

The Resting Potential There is an electrical charge across the membrane. This is the membrane potential. The resting potential (when the cell is not firing) is a 70mV difference between the inside and the outside. inside outside Resting potential of neuron = -70mV

Neurotransmitters Chemical messengers released by terminal buttons through the synapse. We should know at least 4 types and what they do. Take a look -

Ion concentrations Cell Membrane in resting state K+ Na+ Cl- K+ A- Outside of Cell Inside of Cell Na + Cl-

The Cell Membrane is Semi-Permeable

Resting Potential At rest the inside of the cell is at -70 microvolts With inputs to dendrites inside becomes more positive if resting potential rises above threshold an action potential starts to travel from cell body down the axon Figure shows resting axon being approached by an AP

Depolarization ahead of AP AP opens cell membrane to allow sodium (NA+) in inside of cell rapidly becomes more positive than outside this depolarization travels down the axon as leading edge of the AP

Repolarization follows After depolarization potassium (K+) moves out restoring the inside to a negative voltage This is called repolarization The rapid depolarization and repolarization produce a pattern called a spike discharge

Finally, Hyperpolarization Repolarization leads to a voltage below the resting potential, called hyperpolarization Now neuron cannot produce a new action potential This is the refractory period

Acetylcholine Its function is motor movement and maybe memory. To much and you will…. Not enough and you will…. Lack of ACH has been linked to Alzheimer’s disease.

Dopamine Its function is motor movement and alertness. Lack of dopamine is associated with Parkinson’s disease. Overabundance is associated with schizophrenia.

Serotonin Function deals with mood control. Lack of serotonin has been linked to depression. Take a look -

Endorphins Function deals with pain control. We become addicted to endorphin causing feelings.

Agonists and Antagonists

Drug Effects How about a mouse party?

Types of Neurons Sensory Neurons Motor Neurons Inter Neurons

Neurons and Synapses Types of Neurons SensoryMotor Interneurons

Sensory Neurons (Afferent Neurons) Take information from the senses to the brain.

Spinal Cord Brain Sensory Neuron Sensory Neurons INPUT From sensory organs to the brain and spinal cord. Drawing shows a somatosensory neuron Vision, hearing, taste and smell nerves are cranial, not spinal

Spinal Cord Brain Sensory Neuron Motor Neuron Motor Neurons OUTPUT From the brain and spinal cord To the muscles and glands.

Motor Neurons (Efferent Neurons) Take information from brain to the rest of the body.

Spinal Cord Brain Sensory Neuron Motor Neuron Interneurons Interneurons carry information between other neurons only found in the brain and spinal cord.

Inter Neurons Take messages from Sensory Neurons to other parts of the brain or to Motor Neurons.

Divisions of the Nervous System Take a look -

Sympathetic Nervous System Flight or Fight Response

A Simple Reflex

A Simplified Neural Network Neurons that learn to work together as a team.

The Endocrine System A system of glands that secrete hormones. Similar to nervous system, except hormones work a lot slower than neurotransmitters. Neurotransmitters Hormones

The Major Endocrine Glands