Science Quiz 18.1 - The Nervous System

Functions of the nervous system

• Monitor and control the body’s organs and coordinate their activities

• Sense and respond to stimuli

Main concepts

• The organs and cells of the nervous system have structures that enable them to receive/transmit information

• Hierarchy of organization

  • Central Nervous System (CNS)

  • Peripheral Nervous System (PNS)

PNS

• All non-CNS nerves

• 12 cranial nerves, 31 spinal nerves

• 2 main divisions: somatic nervous system and autonomic nervous system

• Autonomic nervous system has 2 main divisions: sympathetic nervous system and parasympathetic nervous system

Somatic nervous system

Communicates with voluntary muscles

Autonomic nervous system

Communicates with internal organs/glands

Sympathetic nervous system

Mobilizes body systems during increased activity (like stress, fight or flight)

Parasympathetic nervous system

Conserves energy and promotes “housekeeping” during restful periods

Central nervous system

Includes the spine and brain, which has the cerebrum, brain stem, and cerebellum

Spine

Backbone, has stacked vertebrae bones with cartilage cushions in between

Parts of the spine

• Cervical = neck

• Thoracic = chest

• Lumbar = lower back

• Sacrum = tailbone

Spinal cord and nerves

• Protected by vertebrae

• Nerves exit spine through holes called neuroforamen

• 31 spinal nerves exit backbone

• Nerves are bundled neurons

Within a nerve, there are 3 layers of connective tissue

• Endoneurium: surrounds individual neurons

• Perineurium: surrounds bundles of neurons

• Epineurium: outermost layer that surrounds bundles of nerves

Types of neurons

Afferent neurons, interneurons, efferent neurons

Afferent neurons

Receive stimuli and sends impulses to the CNS, also called “sensory neurons”

Interneurons

Connect these neurons in the CNS and integrate flexes, also called “relay neurons”

Efferent neurons

Conduct impulses from the CNS to muscles, glands, etc and carries out response to stimuli, also called “motor neurons”

Structure of a neuron

• cell body (contains organelles)

• dendrite (receives neurotransmitters)

• axon (carries impulses away from dendrites and toward the axon terminal)

• axon terminal (releases neurotransmitters)

• myelin sheath (fatty covering on axon, increases speed of electrical impulses)

• Schwann cells (help maintain functionality of neuron, located on axons)

• nodes of Ranvier (gaps in myelin sheath between Schwann cells)