neurons and neurotransmitters. nervous system –central nervous system (cns): brain spinal cord...
TRANSCRIPT
Nervous System
– Central nervous system (CNS):• Brain• Spinal cord
– Peripheral nervous system (PNS):• Sensory neurons• Motor neurons (somatic and
autonomic)
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Central Nervous System (CNS)Central Nervous System (CNS)
BrainBrain Spinal CordSpinal Cord
Peripheral Nervous System (PNS)Peripheral Nervous System (PNS)
Sensory NeuronsSensory NeuronsMotor NeuronsMotor Neurons
Somatic Nervous System• voluntary movements via
skeletal muscles
Somatic Nervous System• voluntary movements via
skeletal muscles
Autonomic Nervous System• organs, smooth muscles
Autonomic Nervous System• organs, smooth muscles
Sympathetic- “Fight-or-Flight” responses
Sympathetic- “Fight-or-Flight” responses
Parasympathetic - maintenance
Parasympathetic - maintenance
The Nervous SystemThe Nervous SystemThe Nervous System
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.Divisions of the autonomic nervous system
Basic units of the nervous system Receive, integrate, and transmit information Operate through electrical impulses Communicate with other neurons through chemical signals More about neurons and neuronal anatomy later
Neurons
Glial cells
• 100 billion neurons
• 10x more glial cells
• Glial cells– Support neurons (literally, provide physical
support, as well as nutrients)– Cover neurons with myelin– Clean up debris– “Housewives”
• Regulate external environment (ions, etc.)• Most abundant glial cell • May contribute to blood-brain barrier and to synapses
Astrocytes
Sensory (Afferent) vs. Motor (Efferent)Sensory (Afferent) vs. Motor (Efferent)
e.g., skin
e.g., muscle
Gray’s Anatomy 38 1999
sensory (afferent) nerve
motor (efferent) nerve
Neurons that send signals from the senses, skin, muscles, and internal organs to the CNS
Neurons that transmit commands from the CNS to the muscles, glands, and organs
Neurons
Axon of anotherneuron
Axon of anotherneuron
Cell BodyCell BodyDendritesDendrites
AxonAxon
MyelinSheathMyelinSheath
Dendrites of another neuron
Dendrites of another neuron
Neural Anatomy
Dendrite the bushy, branching extensions of a
neuron that receive messages and conduct impulses toward the cell body
Axon the extension of a neuron, ending in
branching terminal fibers, through which messages are sent to other neurons or to muscles or glands
Neural Anatomy and communication
Synapse junction between the axon tip of the sending
neuron and the dendrite or cell body of the receiving neuron
tiny gap at this junction is called the synaptic gap or cleft
Synapse movie
Specific Parts: The Neuron Function
Neurons = 3 functions: Reception, Conduction, Transmission
1.3.
2.
Action Potential
When dendrites stimulated, the delicate balance is altered
Membrane breaks downPositively charged ions rush in
(depolarization)Charge = less negativeCauses release of chemicals from
terminal buttons
Relay Race
• Action Potential starts at dendrite– Through cell body– Down Axon– Axon Terminals
• How does it get to the next cell’s dendrites?
• Neurons don’t touch– Synapse = millionth inch gap– In synapse = vesicles w/ neurotransmitters
» Chemical messengers that transmit info
Communication
• Impulse releases neurotransmitter from vesicles
• Neurotransmitter enters synaptic gap
• Neurotransmitter binds to receptors on the receiving neuron
Myelin Sheath– Fatty material made by glial cells– Insulates the axon– Allows for rapid movement of
electrical impulses along axon– Nodes of Ranvier: gaps in myelin sheath
where action potentials are transmitted– Multiple sclerosis is a breakdown of
myelin sheath– Speed of neural impulse Ranges from 2 –
200+ mph
Neurotransmitters
chemical messengers that traverse 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 it will generate a neural impulse
Neurotransmitters (>60)• Acetylcholine (ACh)
– 1st substance identified as NT– Links motor neurons and muscles (contract or relax)
• e.g. curare vs black widow spider– Also involved in memory, learning, sleep, dreaming
(acetylcholine movie)• Endorphins (the brain’s own morphine)
– 1973 injected rats with morphine– Bound like NTs– Brain had receptors for exogenous substance?
• Brain must produce its own morphine• Released during pain and discomfort