Nervous system Flashcards
What is the CNS?
Comprised of brain and spinal cord and protected by meninges (protective membrane)
What is the PNS?
Comprised of the somatic nervous system
What is a nerve net?
Consists of short, unmyelinated, relatively slow nerve cells
What is meninges?
Tough protective membrane which surrounds brain and spinal cords
What is the order of the relay, motor and sensory neurones?
Sensory - Relay - Motor
What is the sensory neurone?
Carry nerve impulse from receptor cell to coordinator, either the brain or spinal cord
What is the relay neurone?
Lies in CNS. Receives impulse from sensory and passes to motor neurone
What is the motor neurone?
Carry impulse from coordinator to effector (muscle or glands)
What are dendrons?
Part of axon between the dendrites and the cell body
What are dendrites?
Thin extensions that carry the impulse towards cell body
What are axons?
Long cytoplasmic extensions which transmit impulse away from cell body
What is the role of the receptor?
To detect the stimulus
What is the role of the effector?
The muscle or gland which carries out the response
What is the myelin sheath?
Many Schwann cells that form a multi-layered fatty sheath to speed up impulse
What are Schwann cells?
Cells which surround and insulate neurones
What are Nodes of Ranvier?
Areas along axon where myelin sheath is missing
What is grey matter?
Contains the neuronal cell bodies and unmyelinated neurones
What is a dorsal root ganglion?
Area of spinal cord where cell bodies of sensory neurones are found
What is a ventral root?
Area of spinal cord where the motor neurone exits
What is the cell body?
Part of nucleus which contains the nucleus, RER, numerous mitochondria and other organelles
What are the differences between Hydra and humans?
Hydra: Doesn’t have a CNS, has a nerve net. 1 type of nerve cell. Short cell process. No myelin insulation. Slow conduction speed. Impulse from point of stimulation travel both directions. Few effectors. Few stimuli that can be detected by sensory receptors
Humans: Has CNS. Contains 3 types of nerve cell (sensory, relay, motor). Long cell process. Has myelin insulation. Fast conduction speed. Many effectors. Lots of stimuli that can be detected by sensory receptors
What is the length of a sensory neurone?
Short
What is the length of a relay neurone?
Short
What is the length of a motor neurone?
Long