Download nerve net

The Nervous System
Regulation
• The control and coordination of life activities
– All organisms use chemicals to regulate life
activities
– Multicellular animals have NERVE CONTROL
– Allow for organisms to maintain HOMEOSTASIS
• Stimulus:
– Any change in the external or internal
environment that initiates a RESPONSE
• Response:
– A change in BEHAVIOR
• Stimuli are detected by RECEPTORS
– Sensitive to a particular type of stimulus
• Ex. EyesLight, EarsSound
• Effectors:
– Organs that produce a response to a stimulus
• Ex. Muscles and Glands
Neuron
• Specialized cells which are responsible for
transmitting IMPULSES from one part of the body
to another
• Impulse:
– Electrical and chemical changes that travel through
neurons
– Causes the release of NEUROTRANSMITTERS from
terminal branches
– **Neuron-Nerve-Ganglia-Brain
• Made up of 4 main parts
Dendrites
(Receptors)
• Cell branches that receive impulses from other
neurons or from receptors
Cyton
• The cell body
– Contains a nucleus
Axon
• The branch of the cell that transmits impulses
away from the cyton
Myelin Sheath
• The fatty insulation covering produced by the
Schwann cells.
• Nodes of Ranvier – Area of no myelin
*
Node of
Ranvier
*
*
Myelin
Schwann Cell
Terminal Branches
• Responsible for:
– transmitting impulses to the dendrites of other
neurons
– Transmitting impulses to effectors
Synapses
• Junction between adjacent nerve cells
• Some nerve cells have junctions with muscles
or glands
– Chemicals released stimulate contraction of the
muscle, or secretion by the gland
Neurotransmitters
• Chemicals that are secreted by the terminal
branch into the synapse between neurons
• Carry impulses from one cell to the next
– Ex. Acetylcholine and Noradrenaline
• Amoeba – No true nervous system
• Paramecium
– System of FIBRILS that transmit impulses to cilia
• Regulates LOCOMOTION and INGESTION
• Some species of Protozoans have EYESPOTS
• Receive stimuli and generate impulses to produce a
response
• Hydra
– Contain specialized cells similar to neurons, but do
not have a central nervous system
– Cells connect to form a NERVE NET
• Impulses travel in any direction
• Earthworm
– Has neurons organized into distinct structures and
organs which form a TRUE NERVOUS SYSTEM
• Brain:
– Mass of ganglia located on the dorsal side of the worm, near
the head
• Ventral Nerve Cord
– Main nerve
– Connected to the brain and runs along the length of the
animal on the ventral side (Belly)
• Nerve Branches
– Series of smaller nerves that branch to all parts of organism
– Impulses are generated by receptors and travel through the
nerves to reach muscles and glands
• Grasshopper
– Similar nervous system to earthworm
– Has SENSORY ORGANS
• Eyes
• Tympanum- Detects sound
• Antennae- Sense and Touch
A Lateral view
B Dorsal view
1 Antenna
2 Brain (cerebral ganglion)
3 Compound eye
4 Tympanum
5 Ganglion
6 Beginning of the Dorsal Nerve Cord
7 Segmental nerves
9 Ventral nerve cord