Nervous System Structure & FunctionDr. Frank Mitloehnerfmmitloehner@ucdavis.edu

Organization of the Nervous System• 1) Central nervous system (CNS)

– Brain– Spinal cord

• 2) Peripheral nervous system (PNS)– Cranial nerves– Spinal nerves– Autonomic nerves

1) Central nervous system

The CNS is involved in:• Transmission of information

(signals)• Memory • Problem-solving • Input-output capability

The Central Nervous System (CNS)

Brain Spinal

Cord

2) Peripheral nervous system

PNS function is:• Transmission of nerve impulses

The Peripheral Nervous System (PNS) PNS = only nerves, NOT spinal cord and brain

Peripheral Nerves

Cranial Nerves

The Peripheral Nervous System is only involved in:

A. Transmission of information (signals)

B. Memory C. Problem-solving D. Input-output capability  

Positron Emission Tomography (PET) Bright spots highlight metabolically active sections of the brain during a language task. The back lights up when the person reads, the middle during active speech and the front when reasoning about the meaning of a word

The Brain

Five divisions:• Telencephalon (cerebral hemispheres)• Dienencephalon (thalamus,

hypothalamus)• Mesencephalon (reflex centers)• Metencephalon (cerebellum, pons)• Myelencephalon (medulla oblongata)

Divisions of the CNS

Which of the following are not a division of the brain?

A. Telencephalon B. BenencephalonC. MesencephalonD. Metencephalon E. Myelencephalon

Lobes of the Brain

• Frontal lobe: reasoning• Parietal lobe: seat of sensory and

motor cortex• Temporal lobe: hearing• Occipital lobe: vision

The Basal Ganglia

The Limbic System

Which of the following is the seat of sensory and motor cortex?

A. Frontal lobeB. Parietal lobeC. Temporal lobeD. Occipital lobe

Properties of the Nervous System

• Nerve function is generally very similar among all mamalian species

• All neurons (nerve cells) make up the nervous system

• Neuron membranes are electrically excitable (receive and send electrical signals)

• The function of the nervous system is: a) to collect information (signals), b) to process those information, c) to generate responses to control behavior

Nerve Cell Terminology• The neuron (nerve cell) consists of the

soma (cell body) and all its processes (dendrites and axons)

• A dendrite is a process that conducts impulses toward the cell body

• An axon (also called nerve fiber) conducts impulses away from the cell body

• The axon is covered by a membrane, called axolemma

Which of the following is the typical direction of flow of information through a cortical neuron?

A. axon; dendrite; cell body; synaptic terminalB. synaptic terminal; dendrite; cell body; axonC. dendrite; cell body; synaptic terminal; axonD. synaptic terminal; cell body; axon; dendriteE. dendrite; cell body; axon; synaptic terminal

Three Types of Neurons

1) Sensory neurons: transmit information of an internal or external stimulus to CNS (pain, temperature, touch…)

2) Interneurons: connect neurons inside the CNS

3) Motor neurons: carry signals from CNS to effector organs like e.g., muscles, or glands

Nerve(bundles of axons)

Spinal Cord

Reflex Arc

The axon can also be surrounded by supporting glial cells (white lipid structure), called myelin sheath. This myelin sheath is interrupted by regular spaced myelin-free gaps, called nodes of Ranvier.

Myelin Sheath

Nodes of Ranvier

Myelin Sheath

• Myelin is a white lipid substance that forms a sheath around the axon

• Serves as an electrical insulator• Nerve cells in the gray matter of

the CNS are not myelinated but the white matter is myelinated

Myelinated Axon

Which of the following is NOT a function of glial cells?

A. Provision of nutrition to the brainB. Insulation of a nerve cell from other

nerve cellsC. The conduction of action potentialsD. Removal of physical debris from the

brainE. Physical support of neurons

Axon Terminal and Synapse• The end of the axon is called axon terminals

• Continuity from one neuron to the next is

provided by the synapse • There is no physical contact between

neurons. They are separated by a gap• This gap between two neurons is called the

synaptic gap or synapse• Signals between two neurons are conducted

by chemical means through the synapse

Synapse and Axon Terminals

Axon Terminals

Synapse

Myelinated Axon

Questions?