The Nervous System: Structure and Control of Movement
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What does the nervous system do?
- Rapid means of internal communication
- Allows us to move about, talk, and co-ordinate the activity of billions of cells
- Maintain homeostasis
What are the 4 functions of the nervous system?
- (1) Control of the internal environment (nervous system works with endocrine system)
- (2) Voluntary control of movement
- (3) Programming of spinal cord reflexes
- (4) Assimilation of experiences necessary for memory and learning
What are the 3 regions that neurons are divided into?
- (1) Cell body
- (2) Dendrites = serve as receptive area that can conduct electrical impulses toward the body
- (3) Axon (nerve fibre) = caries the electrical message away from the cell body toward another neuron or effector organ
What is a synapse?
Contact point between an axon of one neuron and the dendrite of another
What is irritability?
The ability of the dendrites and neuron cell body to respond to a stimulus and convert it to a neural impulse
What is conductivity?
Transmission of the impulse along the axon
What is a nerve impulse?
An electrical signal carried the length of the axon
What is a resting membrane potential?
The electrical charge difference between the inside and outside of the membrane
What are ions?
Elements with a positive or negative charge
What 2 factors determine the magnitude of a resting membrane potential?
(1) Permeability of the plasma membrane to different ion species
(2) The difference in ion concentrations between the intracellular and extracellular fluids
What 2 elements are present in a membrane in the greatest concentration?
Channels regulate ion passage across the plasma membrane
At rest, which channels for ion movement across the plasma membrane are open and which are closed?
- All sodium are closed (movement into the cell)
- Some potassium channels are open (movement out of the cell)
Net loss of positive charges from the inside making the resting membrane potential negative
Explain the sodium/potassium pump.
If potassium continued to diffuse out of the cell, and sodium in, concentration gradients would decrease resulting in loss of the negative membrane potential.
Pump uses energy from ATP to maintain intra/extracellular concentrations by pumping sodium out and potassium in.
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