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.
What do inhibitory postsynaptic potentials cause?
Hyperpolarization (more negative resting memb potential)..
- Neurons with more negative memb potential resist depolarization
What are the 2 types of mechanoreceptors?
- Muscle spindles
- Golgi tendon organs
Define propriception
The sense of the body’s position in space based on specialized receptors that reside in the muscles, tendons and joint.
What are proprioreceptors?
sensors that provide information about joint angle, muscle length, and muscle tension, which is integrated to give information about the position of the
limb in space.
What do muscle spindles respond to, and consist of?
Respind to changes in muscle length.
Consist of:
- Intrafusal fibres
- Gamma motor neurons
What is the function of the muscle spindle?
To assist in the regulation of movement and maintain posture.
What do Golgi tendon organs do?
Monitors force development in muscle
- prevents muscle damage during excessive force generation
Stimulation of GTO does what?
Results in reflex relaxation of muscle
- inhibitory neurons send inhibitory postsynaptic potentials to muscle alpha motor neurons
What may the ability to voluntarily oppose GTO inhibitioin be related to?
Gains in strength with training due to increased tendon stiffness
