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The nervous system is a combination of electrical & chemical signals that enable nerve cells to communicate with each other.
3 overlapping functions:1. __________
conduction of signals (light, smell) from sensory receptors to integration centers
2. __________ process by which the information from the environmental stimulation of the sensory receptors is interpreted and associated with appropriate responses of the body
Integration is carried out in the Central Nervous System (CNS) (brain & spinal cord in vertebrates)
3. __________ conduction of signals from the integration center to effector cells that actually carry out the body’s
responses to stimuli
Signals are conducted by nerves.Sensory input and Motor output are carried out in the Peripheral Nervous
System (PNS)
• The spinal cord conveys information from the brain to the PNS
• The __________ also produces reflexes independently of the brain
• A __________ is the body’s automatic response to a stimulus
Nervous system is composed of:
1. __________
(nerve cell) functional unit of the nervous system
transmits signals from one location in the body to another
__________– convey nerve impulses toward the cell body
__________– convey nerve impulses away from the cell body
2. __________
provide structure
protect, insulate and assist neurons
Nervous systems:
1. A nerve net is a series of interconnected nerve cells 2. Sea stars have a nerve net in each arm connected by radial
nerves to a central nerve ring
More complex animals have nerves (bundles that consist of the axons of multiple nerve cells)
3. Nerve Cord
thick bundle of nerves usually extending through the body from the brain
4. Cephalization is the clustering of sensory organs at the front end of the body (anterior)
• Relatively simple cephalized animals, such as flatworms, have a central nervous system (CNS)
Fig. 49-2b
(c) Planarian (flatworm)
Nervecords
Transversenerve
Brain
EyespotBrain
(d) Leech (annelid)
Segmentalganglia
Ventralnervecord
Fig. 49-2c
(e) Insect (arthropod)
Segmentalganglia
Ventralnerve cord
BrainAnteriornerve ring
Longitudinalnerve cords
(f) Chiton (mollusc)
Ganglia
Fig. 49-2d
(g) Squid (mollusc)
Ganglia
Brain
Brain
Spinalcord(dorsalnervecord)
Sensoryganglia
(h) Salamander (vertebrate)
Fig. 49-4Peripheral nervoussystem (PNS)
Cranialnerves
Brain
Central nervoussystem (CNS)
GangliaoutsideCNS
Spinalnerves
Spinal cord
The vertebrate brain is regionally specialized :
• All vertebrate brains develop from three embryonic regions: forebrain, midbrain, and hindbrain
1. Forebrain includes:• Cerebrum
contains the most sophisticated integrating centers• Diencephalon develops into three regions:
– epithalamus includes the pineal gland and generates cerebrospinal fluid from blood
– thalamus - main input center for sensory information and main output center for motor information
– hypothalamus regulates homeostasis and basic survival behaviors such as feeding, fighting, fleeing, and reproducing; circadian rhythms
2. Midbrain:• midbrain contains centers for receipt and integration
of sensory information
• brainstem - coordinates and conducts information between brain centers
3. Hindbrain includes:– The pons regulates breathing centers in the medulla
– The medulla oblongata contains centers that control several functions including breathing, cardiovascular activity, swallowing, vomiting, and digestion
• Cerebellum controls movement and balance
Fig. 49-9c
Pons (part of brainstem), cerebellum
Spinal cord
Cerebrum (includes cerebral cortex, white matter,basal nuclei)
Diencephalon (thalamus, hypothalamus, epithalamus)
Midbrain (part of brainstem)
Medulla oblongata (part of brainstem)
Pituitarygland
Cerebrum
Cerebellum
Central canal
Diencephalon:
Hypothalamus
Thalamus
Pineal gland(part of epithalamus)
Brainstem:
Midbrain
Pons
Medullaoblongata
(c) Adult