BIOGEOSPHERE
Bilingual Biology and Geology
I.E.S. "J.S.Elcano (Sanlúcar Bda.)
4.1. The somatic nervous
system
Nerves can be classified in two ways:
- By the direction of nerve impulse transmission:
§ Sensory nerves
They transmit the information from the sense organs.
They are formed only by sensory neurons.
§ Motor nerves
They transmit orders to effector organs (muscles).
They are formed only by motor neurons.
§ Mixed nerves
They transmit sensations and orders.
They are formed by sensory and motor neurons.
- By the nerve centre from which they emerge:
- Cranial nerves
They come from the encephalon.
There are 12 pairs.
They can be sensory or motor nerves.
They innervate the head and neck.
- Spinal nerves
They come from the spinal cord.
There are 31 pairs.
All of them are mixed nerves.
They innervate trunk, legs and arms.
ACTIVITIES
After reading the text, copy and answer the following questions into your notebook:
Remember: you must make complete sentences.
4.2. Describe the main differences between sensory and motor nerves.
What is a mixed nerve?
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Eva Mª
López Rodríguez
Departamento
Biología y Geología
IES " J. S. Elcano"
Sanlúcar de Barrameda