neuron lect1 -handout
TRANSCRIPT
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Cognitive & Biopsychological Cognitive & Biopsychological PerspectivesPerspectives
Structure & Functioning of NeuronStructure & Functioning of Neuron
(Neuron 1)(Neuron 1)
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Structure & Functioning of Neuron
To provide a basic understanding of:
• The structure of the neuron
• Transmission of the neural impulse along the neuron
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NERVOUS SYSTEM
Central Nervous System (CNS)
Peripheral NervousSystem (PNS)
BRAIN SpinalCord
Somatic System(Motor & Sensory)
Voluntary
Autonomic Nervous System (ANS)
Sympathetic
Parasympathetic
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Side View
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Structure of the
Neuron
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Structure of Neuron
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The Neuron
• Resting Potential
• Threshold
• Action Potential
• ‘All or none’ law
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The Neuron
• Sodium ions (Na+)
• Potassium ions (K+)
• Chloride ions (CL-)
• (Also, Protein ions An-)
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Resting Potential
Axon
- - - - - -
- - - - - - -
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Distribution of Negative Ions
Axon
CL- CL- CL- CL-
An- CL- An- An-
An- An- CL-
CL- CL- CL- CL-
An- Trapped inside axon
CL- greater concentration outside axon than inside
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Distribution of Positive Ions
Axon
Na+ Na+ Na+ Na+ K+
Na+ K+ K+ K+
K+ K+ Na+ K+ K+
Na+ Na+ K+ Na+ Na+
K+ greater concentration inside axon than outside
Na+ greater concentration outside axon than inside
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Resting Potential
The resting potential is maintained by:
1. Selectively Permeable Membrane
2. Sodium – Potassium Pump
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Resting Potential
Axon
Na+ Na+ Na+ Na+ K+
Na+ K+ K+ K+
K+ K+ Na+ K+ K+
Na+ Na+ K+ Na+ Na+
3 Sodium ions (Na+) pumped out for every 2 Potassium ions (K+) drawn in
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Propagation Propagation of the action potential refers to the transmission of the action
potential along the axon.
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Propagation
Axon
+
+ + + - - - - -
+ + + - - - - - - +
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Propagation
Axon
- - + + + - - - -
- - - + + + - - -
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Propagation
Axon
- - - - - + + +
- - - - - - + + +
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Saltatory Conduction Saltatory conduction is the transmission of the impulse from node to node
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"All or None" law If the threshold is reached the neuron will 'fire' (ie a neural impulse will occur) if it is not reached the neuron will not fire
• Therefore, the size and shape of the action potential are independent of the intensity of the stimulus that initiated it
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Refractory Period
For a few milliseconds following a neural impulse the membrane is temporarily unexcitable and the axon cannot be fired again regardless of the strength of the stimulus.
This interval is known as the
Absolute Refractory period
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Refractory Period
Following the Absolute Refractory period
• there is a short period of time just before the membrane returns to normal during which the neuron will fire but a stronger than normal stimulus is required
• This period of time is called the
Relative Refractory period
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Neuron Plasticity & Age
The structure of the neuron is fairly ‘plastic’, that is the fibres of the
neuron can increase or decrease their branching pattern as a function of
age, experience and chemical influences.
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Dendritic Growth
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Glia (Neuroglia)
• Glia are the other main component of
the nervous system besides neurons • Occupy about the same total space as
neurons • They do not transmit information
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Glia Functions
• Remove waste
• Fill space left by dead neurons (form scar tissue)
• Build the myelin sheath
- Schwann cells (PNS) - Oligodendrocytes (CNS)
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Spinal Research Raisman (1997)
• Olfactory cells from the nose (although CNS cells) can regenerate and form functional connections after damage
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Spinal Research Raisman (1997)
• Studies using Schwann sheath, found although they provide guidance to a regenerating spinal cord, the cord can not make the connection at the other end into the oligodendrocyte
• Olfactory cells were able to make that connection.
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EEG
Electroencephalograph (EEG)Machine that records the electrical activity of the brain via electrodes placed on the surface of the scalp
Electroencephalogram (EEG)Trace or record of the electrical activity of the brain
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Brain Waves
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References
Carlson, N. (2010). Physiology of Behavior, (10th
ed). London: Allyn & Bacon.
Kalat, J. (2009). Biological Psychology, (10th ed).
Belmont, California: Wadsworth.
Pinel, J.P. (2008). Biopsychology, (7th ed).
London: Allyn & Bacon.