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NEURAL COMMUNICATION

How does one neuron communicate with another? Original belief was that axons and dendrites were fused

Cajal noticed gaps between nerve cells Sherrington noticed interruptions in the neural pathways

Synapse (Synaptic gap, synaptic cleft) Space between sending axon and receiving dendrite “Protoplasmic kisses” Neurotransmitters (chemical messengers)

Released by axon Attach to receptor sites in the dendrite

Lock and key Unlocks channels to send ions into the axon, thus sending signal to the

next Excess neurotransmitters are reabsorbed into the sending neuron

(reuptake)

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SYNAPSE

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ACHETYLCHOLINE AND ENDORPHINS

Acetylcholine Key role in learning and memory Messenger between every motor neuron and muscle

causes muscle contraction Poisons that affect Ach

Curare can block reception of Ach and in effect paralyze an animal Botulin stops release of Ach from sending neuron Black widow spider venom causes synaptic flood of Ach

Endorphins Discovery of opiates attaching to receptors in areas linked to mood

and pain (Snyder 1973) Endorphins are the key to the opiate lock (endogenous morphine)

Adrenaline Runners’ high

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HOW DRUGS AND OTHER CHEMICALS AFFECT NEUROTRANSMITTERSDrugs often mock neurotransmitters Neurons are flooded Body shuts down production

Detox problems Lingering side effects Addiction

Agonists excite the neuron Antagonists inhibit the neuron

Some scientists attempt to create drugs that mimic neurotransmitters that are out of balance

Blood-brain barrier keeps most unwanted chemicals out L-dopa as a treatment for Parkinsons

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THE NERVOUS SYSTEM

The Nervous Sytem: The body’s primary information system Central nervous system: the brain and spinal chord The peripheral nervous system: links central nervous system with sense

receptors, muscles, and glands Nerves: the motor axons that carry the information

Optic nerve: million axons bundled together into a single cable carrying information from each eye (Mason and Kandel (1991)

Three types of neurons Sensory neurons: sends information from the body’s tissues and

sensory organs to the brain Interneurons: allow internal communication for the central nervous

system Motor neurons: sends information from the central nervous system

to the body’s tissues

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THE PERIPHERAL NERVOUS SYSTEM

Somatic Nervous System: Controls the movement of skeletal muscles

Autonomic Nervous System: controls the glands and the muscles of internal organs

Sympathetic Nervous System: arouses people for defensive action Accelerate heartrate Slow digestion Raise blood sugar Dilate arteries Cool with perspiration

Parasympathetic Nervous System: opposite of sympathetic nervous system

Slows heartrate Speeds digestion Lowers blood sugar Dilate arteries

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THE CENTRAL NERVOUS SYSTEM

Spinal cord and Brian Information superhighway Reflexes: automatic responses

Simple pathway is one motor and one sensory neuron Knee-jerk pain (often felt AFTER the reflex) Effects of severing spinal cord

No feeling below the point of injury Reflexes still occur without the brain registering the pressure sensor Sexual response

Genitals are still reflexive (Goldstein 2000) No reaction to sexual imagery (Kennedy and Over 1990, Sipski et al 1999)

Neural Networks Brian receives information, interprets it, and decides responses

300 trillion cortical-synaptic connections (Rachmachadran and Blakesly 1998) Neural networks: clustered work groups

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THE ENDOCRINE SYSTEM

Endocrine System: the body’s second communication system

Hormones originate in one tissue and use the bloodstream to affect other tissues Glands secrete hormones (another form of chemical messenger) Much slower than the nervous system Adrenal glands (top of kidneys

Produce epinephrine and norepinephrine to control arousal Provide surge of energy when needed

Pituitary Gland Controlled by the hypothalamus Releases hormones that influence growth Influences release of other hormones from other glands “master gland” Triggers release of sex hormones

Feedback loop: Brain -> pituitary -> other glands -> hormones -> brain

Distinction often fuzzy, as sometimes neurotransmitters can act like hormones (Agnati et al 1992, Pert 1986

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EXIT TICKET AND HOMEWORK

Exit Ticket What are neurons and how do they transmit information? How does a neuron communicate with other cells to influence

behavior? What are the elementary components of our nervous system? What are the functional divisions of our nervous system? How does the endocrine system deliver its messages?

Homework: Complete diagram packet Read Pages 68-75 Be prepared for Quiz

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