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Terms in this set (45)

• allows body to respond quickly to changes in the environment by gathering information, transmitting, and processing information to determine the best response, and sending information to muscles, glands, and organs so they can respond correctly.

• In Hydra, nerve nets are diffused all over the body to control the contraction of the gastrovascular cavity or the gastrocoel.

• CEPHALIZATION - the onset of cephalization marks a more complex nervous system
• In simple cephalized animals (ex: Planaria) a simple central nervous system or CNS with a small brain and longitudinal nerve cords is present.

• In more complex invertebrates like annelids and arthropods, the nervous system is divided into two regions: the CNS and PNS.
• CNS or Central Nervous System is composed of brain and ventral nerve cords with clusters of neurons called ganglia.
• The rest of the nerves in animal's body is the PNS or peripheral nervous system.

• Central (Brain and Spine) and
• Peripheral (Cranial and Spinal Nerves)
1. Somatic Nervous System (voluntary)
- Relays information from skin, sense organs & skeletal muscles to CNS
- Brings responses back to skeletal muscles for voluntary responses
2. Autonomic Nervous System (involuntary)
- Regulates bodies involuntary responses
- Relays information to internal organs
- Two divisions:
A. Sympathetic nervous system - in times of stress
➢ Emergency response
➢ Fight or flight
B. Parasympathetic nervous system - when body is at rest or with normal functions; Normal everyday conditions

• Basic Cells of the Nervous System:
- Parts of a Neuron
1. Dendrite - receive stimulus and carries it impulses toward the cell body
2. Cell Body with nucleus - nucleus & most of
3. Axon - fiber which carries impulses away from cell body
4. Schwann Cells- cells which produce myelin or fat layer in the PNS
5. Myelin sheath - dense lipid layer which insulates the axon - makes the axon look gray
6. Node of Ranvier - gaps or nodes in the myelin sheath
- Impulses travel from dendrite to cell body to axon

• Three types of Neurons
o Sensory neurons - bring messages to CNS
o Motor neurons - carry messages from CNS
o Interneurons - between sensory & motor neurons in the CNS