Nervous Systems

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3

Slide 19

The brain and spinal cord contain

Gray matter, which consists of neuron cell bodies, dendrites, and unmyelinated axons.

White matter, which consists of bundles of myelinated axons.

Slide 20

Glia in the CNS

Glia have numerous functions

Ependymal cells promote circulation of cerebrospinal fluid.

Microglia protect the nervous system from microorganisms.

Oligodendrocytes and Schwann cells form the myelin sheaths around axons.

Slide 21

Glia have numerous functions

Astrocytes provide structural support for neurons, regulate extracellular ions and neurotransmitters, and induce the formation of a blood-brain barrier that regulates the chemical environment of the CNS

Radial glia play a role in the embryonic development of the nervous system.

Slide 22

Glia in the vertebrate nervous system

Oligodendrocyte

Microglial

cell

Schwann cells

Ependy-

mal

cell

Neuron

Astrocyte

CNS

PNS

Capillary

(a) Glia in vertebrates

(b) Astrocytes (LM)

VENTRICLE

50 µm

Slide 23

The Peripheral Nervous System

The PNS transmits information to and from the CNS and regulates movement and the internal environment.

In the PNS, afferent neurons transmit information to the CNS and efferent neurons transmit information away from the CNS.

Cranial nerves originate in the brain and mostly terminate in organs of the head and upper body.

Spinal nerves originate in the spinal cord and extend to parts of the body below the head.

Slide 24

peripheral nervous system

Efferent

neurons

Locomotion

Motor

system

Autonomic

nervous system

Afferent

(sensory) neurons

PNS

Hearing

Circulation

Gas exchange

Digestion

Hormone

action

Enteric

division

Sympathetic

division

Parasympathetic

division

Slide 25

The PNS has two functional components: the motor system and the autonomic nervous system.

The motor system carries signals to skeletal muscles and is voluntary.

The autonomic nervous system regulates the internal environment in an involuntary manner.

Slide 26

The PNS autonomic nervous system has sympathetic, parasympathetic, and enteric divisions