CNS: structure and function Flashcards
What are the functions of the nervous system?
- control of the internal environment
- voluntary control of movement
- spinal cord reflexes
Describe the peripheral nervous system
Neurons outside the CNS
Describe the sensory division
afferent fibres transmit impulses from receptors to CNS
Describe the motor division
efferent fibres transmit impulses from the CNS to effector organs
What 2 types of input make up sensory nervous system?
somatic sensory
visceral sensory
What 2 types of input make up motor nervous system?
somatic motor
autonomic motor
What does the axon (nerve fibre) do?
- carries APs away from cell body
- covered by Schwann cells (forms discontinuous myelin sheath)
What does it mean if the axon diameter is larger or there is increased myelin sheath?
greater speed of neural transmission
When a cell is polarised, does it have a positive or negative charge?
Negative.
–5 to –100 mv
-40 to –75 mv in neurons
What is the magnitude of a resting membrane potential determined by?
- Permeability of plasma
membrane to ions. - Difference in ion concentrations
across membrane
* Na+, K+, C, and Ca+2
What ions plays most important role in generating resting membrane potential?
Na+ (greater conc on outside of cell) and K+ (greater conc on inside of cell)
How is resting membrane potential achieved?
Maintained by sodium-potassium pump
–Potassium tends to diffuse out
of cell
–Na+/K+ pump moves 2 K+ in
and 3Na+out
AP occurs when a stimulus of sufficient strength depolarizes the cell, how?
Opens Na+ channels, Na+ diffuses into cell (inside becomes more positive)
What is the all-or-none law?
Once a nerve impulse is initiated, it will travel the length of the neuron
What are the 2 ways in which excitatory postsynaptic potentials can promote depolarization?
1) Temporal summation - Rapid, repetitive excitation from a single excitatory presynaptic neuron
2) Spatial summation - Summing EPSPs from several different presynaptic neurons.