Nervous system Flashcards
What is the central nervous system?
Brain and Spinal cord
Controls voluntary movements
What is the peripheral nervous system?
-Links organs and CNS
-Neurones outside CNS
-Somatic and Autonomic NS
What IS the Somatic NS?
Neuron pairs bringing impulses from receptor cells to effectors
What is Autonomic NS?
Heartbeat, temperature, breathing
Describe the spinal cord
-Flattened cylinder of nervous tissue
-Passes through and protected by vertebral column
-Where most peripheral nerve originate
What is the route of an impulse during a reflex arc?
-Receptor detect stimulus
-Sensory neuron to relay neuron
-Relay neuron to motor neuron
-Effector responds
What are nerve nets?
-Sense receptors respond to limited number of stimuli
-Nerve nets connect sensory photoreceptors and touch sensitive receptors in tentacles
-Number of effectors is small
-Neurons shorter and of one type
-Impulse slower
Describe the myelin sheath
-Only in vertebrates
-Insulates neurone
-Made out of phospholipids in Schwann cells
How id -70mV action potential achieved?
-3 Na move in, 2K move out
-membrane leaks ions back to original place (more K channels)
-negative proteins, organic phosphates, and nucleic acids found in neurone
What happens during depolarization?
-Partial depolarisation reaches action threshold, Na influx. MP +40
What happens during repolarization?
-Na channel close
-K diffuse out
-MP -80
What happens in hyperpolarization?
Na/K pump restore AP (-70)
What are the features of action potential?
-All or nothing
-Same size
-Brain registers impulse strength by frequency
How does temperature affect speed of nerve transmission?
Increase
How does axon diameter affect speed of nerve transmission?
Increase (less resistance)
