Chapter 10, Section 1

Nervous System IBasic Structure and Function

Organization of Nervous System

Central Nervous System (CNS)• Brain & Spinal Cord

Peripheral Nervous System (PNS)• 12 Pairs of Cranial Nerves

• 31 Pairs of spinal nerves

Sensory Division = afferent

• Delivers information from periphery to CNS

Motor Division = efferent

• Carries impulses to muscles or glands (effectors)

Divisions of Peripheral Nervous System

Somatic Nervous System

• carries information to skeletal muscle

• Voluntary Control

Autonomic nervous System

• carries information to smooth muscle, cardiac muscle, and glands

• Involuntary Control

Subdivisions of the Motor

Division

Figure 10.2. (a) overview of nervous system. CNS is grey, PNS is yellow. (b) CNS

receives sensory input from PNS, and sends motor output to PNS. Somatic division of PNS

is under voluntary control, while the autonomic division is under involuntary control.

Subdivision of autonomic nervous system

Sympathetic Division

• Increases response to a stressful situation

• “Fight or Flight”

Parasympathetic Division

• Maintains normal body functions at rest

Components of Nervous System

Neurons

• Integrate, regulate, and coordinate

body functions

• Functions

• Receive information - sensory

• Conduct impulses - motor

Neuroglia (neuro “glue”)

• Provide neurons with nutritional,

structural, and functional support

• Conduct impulses - motor

• Connect neurons - integrative

Neurons

Neurons vary in shape and size

3 Components of a neuron

1. Dendrites receive impulse1. Dendrites receive impulse

2. Call body (soma)

3. Axon – transmits impulse away from

the cell body

Components of a neuron

Dendrites – a cell may have one or many

• Conducts information to cell body

• Dendritic Spines

•Additional contact points on some

dendrites for other neurons

• Increase the number of synapses

possible by a neuron

Cell Body – Soma

• Cytoplasm, Mitochondria, Golgi Apparatus

• Nissl Bodies (rough ER)

• Nucleus with nucleolus

Axon – each neuron has only 1 axon

• Axon Hillock

• Extension of soma into axon

• Trigger Zone – initiates nerve impulse (Action Potential)

• Collaterals – Branches of an axon

• Axon terminal + Synaptic Knob – Specialized ending of axon

Components of a neuron

• Synaptic Cleft - gap at synapse

•Neurofibrils

•Microtubules that support long axons

•Aid in axonal transport

(transport of biochemicals from soma to axon terminal)

Myelin Sheaths greatly enhance the speed of impulses

• Schwann Cells wrap around the axons in a jelly-roll fashion to form myelin

•Myelin Sheath

• thick fatty coating of insulation,

• formed from layers of Schwann cell’s membrane

•Myelination greatly increases the speed of a nerve impulse

• Neurolemma

• outermost layer of Schwann cell that contains the nucleus and cytoplasm.

Myelination of Axons in PNS

• outermost layer of Schwann cell that contains the nucleus and cytoplasm.

• Nodes of Ranvier

• Gaps between Schwann Cells - Site of impulse conduction

Myelination of Axons in PNS

Figure 5. TEM micrograph of a

myelinated and unmyelinated axon.

Figure 10.4 a myelinated axon.

Myelination of Axons in CNS

• Oligodendrocyts

•Myelinate neurons in Central Nervous System

• 1 Oligodendrocyte may myelinate several axons

•White Matter

•Myelinated axons in the CNS

• Grey Matter

• Unmyelinated tissue in the CNS• Unmyelinated tissue in the CNS

• Includes dendrites, somas, and unmyelinated axons

End of Chapter 10, Section 1