nervous system
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Nervous System
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The Nervous System
Two main divisions– Central Nervous System
(CNS) includes the brain and spinal cord
– Peripheral Nervous System (PNS) contains nerves which carry info between the CNS and other organs
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Central Nervous System
The brain receives impulses and sends impulses back to the body
The spinal cord connects the brain to the body
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CNS: The Brain (UP 5)
3 major regions– Cerebrum– Cerebellum– Brainstem
Cerebrum
Cerebellum
Brainstem
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CNS: The Cerebrum Largest part of the brain Involved in voluntary activities, intelligence,
and consciousness Divided into 4 lobes
– Frontal - personality– Temporal - auditory
– Parietal - senses – Occipital - visual area
Parietal
Occipital
Frontal
Temporal
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CNS: Cerebellum & Brainstem
Cerebellum – balance and coordination
Cerebellum
Brainstem includes the pons and medulla oblongata– Involuntary functions
– heart rate, breathing
Brainstem
Medulla Oblongata
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PNS: Peripheral Nervous System All nerves that are NOT part of the brain
or spinal cord Two major divisions of the PNS:
– Sensory division sends impulses from sense organs (ears, nose, etc.) to the CNS
– Motor division send impulses from the CNS to the muscles or glands
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PNS: Motor Divisions Motor division is then divided into the
autonomic and somatic nervous systems
Somatic System – regulates activities under conscious control such as muscle movement– Also involved with reflexes
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Autonomic Nervous System Regulates automatic, involuntary
actions– Parasympathetic Nervous System
decreases heart rate and stimulates digestion; “rest and digest”
– Sympathetic Nervous System increases heart rate; “fight or flight”
These systems have opposite effects
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Neuron Structure (UP 83)
Cell Body
Cytoplasm
Nucleus
Dendrites
MyelinAxon
Muscle (effector)
End Brush Motor End Plate
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Neurons Three types:
– Sensory: carry impulses from sense organs to CNS
– Motor: carry impulses from CNS to muscles/glands
– Interneurons: connect motor and sensory neurons
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Neural Impulses Impulses move along a neuron due to
electrical changes in the membrane
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Neural Impulses (UP 83)
Membrane is polarized, more negative inside
Na+ ions enter; membrane depolarizes
Repolarization follows depolarization
Impulse travels the axon
–http://highered.mcgraw-hill.com/olc/dl/120107/bio_d.swf
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Neural Impulses Resting potential – polarized state,
negative charge inside membrane Threshold –minimum stimulus needed
to activate a neuron Action potential – depolarization &
repolarization of membrane Myelin increases rate of impulse
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Synapses Location where one neuron
transfers an impulse to a cell– Neuron to neuron– Neuron to muscle/gland
Chemicals called neurotransmitters carry signals across a synapse– Acetylcholine and serotonin
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Synapses
http://www.bishopstopford.com/faculties/science/arthur/synapse.swf
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Reflex Arc Reflexes prevent injury Impulse travels from sensory neuron
interneuron motor neuron
http://www.sumanasinc.com/webcontent/anisamples/nonmajorsbiology/reflexarcs.html
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Reflex Arc (UP 84)
Association Neuron
(interneuron)
Sensory Neuron
Cell Body (Sensory Neuron)
Motor Neuron
Receptors (on dendrites)
Synapse
Synapse
Effector (muscle)Motor End Plates
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Animations
Action Potential– http://highered.mcgraw-hill.com/olc/dl/120107/bio_d.swf
– http://outreach.mcb.harvard.edu/animations/actionpotential.swf
Chemical Synapse– http://www.bishopstopford.com/faculties/science/arthur/synapse.swf
– http://highered.mcgraw-hill.com/olc/dl/120107/anim0015.swf– http://outreach.mcb.harvard.edu/animations/synaptic.swf
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Electroencephalogram (EEG) Records electrical activity of the brain Diagnosis of neurological diseases: stroke,
epilepsy, tumors, and sleep disorders
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EEG Activity
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Behavior Impacts EEG
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EEG During Seizures
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Diagnostic Techniques MRI – Magnetic Resonance Imaging uses
radio waves and VERY powerful magnets to create images of the brain
Used to image soft tissue, not bone or teeth
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MRI of the Brain
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CT Scan Computerized Tomography 3-D x-ray image based on tissue density
– Bone appears white, liquids/gases are black, and various tissues are grey
Used to diagnose tumors
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PET Scan Positron Emission Tomography Creates images based on the detection of radiation particles Used to detect tumors, seizure disorders, and evaluate
patients with memory loss
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Brain Death Irreversible cessation of brain activity for 24
hours so that cardiopulmonary function must be maintained by machine