THE NERVOUS SYSTEM

THE NERVOUS SYSTEM

• Definition: A network of billions of nerve cells linked together to form the rapid control center of the body.

• Main function: Integrating center for homeostasis, movement, and almost all other body functions.

The nervous system is made of:

The brain The spinal cord

The nerves The senses

BASIC FUNCTIONS OF THE NERVOUS SYSTEM

1. Sensation• Monitors changes/events occurring in and outside the body. Such changes

are known as stimuli and the cells that monitor them are receptors.

2. Integration• Parallel processing and interpretation of sensory information to determine the

appropriate response

3. Reaction• Activation of muscles or glands (typically via the release of neurotransmitters

(NTs))

ORGANIZATION OF THE NERVOUS SYSTEM

1. Central Nervous System• The brain + the spinal cord• The center of integration and control

2. Peripheral Nervous System• Spinal nerves + Cranial nerves • The nervous system outside of the brain

and spinal cord

PERIPHERAL NERVOUS SYSTEM

• Responsible for communication between the CNS and the rest of the body.

• Can be divided into:• Sensory Division: Conducts impulses from receptors

to the CNS • Motor Division: Conducts impulses from CNS to

effectors (muscles/glands)

Can be divided further:• Somatic nervous system

• Autonomic nervous system

MOTOR DIVISION

• Somatic nervous system• VOLUNTARY (generally): Conducts impulses from the

CNS to skeletal muscles

• Autonomic nervous system• INVOLUNTARY (generally): Conducts impulses from the

CNS to smooth muscle, cardiac muscle, and glands.

NERVOUS TISSUE

2 cell types1. Neurons

• Functional, signal conducting cells

2. Neuroglia• Supporting cells

1.

2.

BASIC NERVE CELL STRUCTURE

3 MAIN TYPES OF NERVE CELLS

sensory neuron

relay neuron

motor neuron

SENSORY NEURONS

Carries impulses from receptors e.g pain receptors in skin to the CNS (brain or spinal cord)

RELAY NEURON

Carries impulses from sensory nerves to motor nerves.

MOTOR NEURON

Carries impulses from CNS to effector e.g. muscle to bring about movement or gland to bring about secretion of hormone e.g LH

http://tle.westone.wa.gov.au/content/file/969144ed-0d3b-fa04-2e88-8b23de2a630c/1/human_bio_science_3b.zip/content/002_nervous_control/page_03.htm

The axon is only 10µm in diameter but can be up to 4m in length in a large animal!}

And in humans up to 1m large!

http://www.tokresource.org/tok_classes/biobiobio/biomenu/metathink/required_drawings/index.htm