Introduction to the Nervous System

Dallas SmuinMegan Veglia

Learning Objectives1. Students will explain the general structures and functions of the

mammalian nervous system, including the central nervous system, the peripheral nervous system, the cranial nerves, and the ventricular system.

2. Students will utilize the neuron doctrine coined by Santiago Ramon y Cajal to explain how neurons communicate with each other to carry information throughout the nervous system.

3. Students will be able to identify the basic functional unit of the brain and describe the function of the major components of the neuron.

4. Students will describe how scientists and physicians use technology to view the living brain, including CT, MRI, and fMRI.

LO 1: Students will explain the general structures and functions of the mammalian nervous system, including the central nervous system, the peripheral nervous system, the cranial nerves, and the ventricular system.

Structure of Nervous System

• 2 portions:o Central Nervous System (CNS)• Brain, spinal cord

o Peripheral Nervous System (PNS)• All nerve structures outside the CNS that

connect the CNS to the rest of the body• Autonomic

oSympathetic (fight or flight)oParasympathetic (rest and digest)

Structure/Function of CNS (Brain)

• Cerebral hemispheres (Cerebrum)o Structure:• 2 parts: gray and white matter

oGray matter: cell bodiesoWhite matter: axons

• Ventricles—storage spot of nutrition and fluid

• Cerebellum• Brain Stem

Structure/Function of CNS (Brain)

• Cerebral hemisphereso Function: Higher order thinking • Movement• Language• Sensory processing• Smelling (olfaction) • Learning/memory

• Cerebellum• Brain Stem

Structure/Function of the CNS (Brain) continued:

• Cerebral hemispheres• Cerebellum

o Function: • Balance• Some cognitive function i.e. attention and

language• Brain Stem

Structure/Function of the CNS (Brain) continued:

• Cerebral hemispheres• Cerebellum• Brain Stem

o Structure: • Composed of:

oMedulla oblongataoPonsoMidbrain

• Continuation of the spinal cord

Structure/Function of the CNS (Brain) continued:

• Cerebral hemispheres• Cerebellum• Brain Stem

o Function:• Conduction—relays information from brain to

body and body to the brain• CN III-IX emerge from the brainstem• In charge of autonomic nerve control of

major organs (i.e. heart beating, lung breathing)

Ventricular System• Composed of:

o Lateral ventricles CONNECTED VIA interventricular foramen to the:

o Third ventricle CONNECTED VIA cerebral aqueduct to the:

o Fourth ventricle goes to the central canal spinal cord

• CSF is inside ventricleso Function:

• Chemical stability• Protects against minor jolts and knocks to the

head

Structure of PNS• Divided into:

o Autonomic (involuntary) • Sympathetic• Parasympathetic

o Somatic (voluntary) • Motor and sensory innervation • Composed of efferent (EFFECTOR) and afferent

nerves

Cranial Nerves• I—olfactory• II—optic• III—oculomotor• IV—trochlear• V—trigeminal• VI—abducent

• VII—facial• VIII—vestibulocochlear• IX—glossopharyngeal• X—vagus• XI—accessory• XII—hypoglossal

LO 2: Students will utilize the neuron doctrine coined by Santiago Ramon y Cajal to explain how neurons communicate with each other to carry information throughout the nervous system.

Ramon and Cajal • Late 17th century• Discovered “Axonal Growth Cone”

o dynamic, actin-supported extension of a developing neuron seeking its synaptic target

o Nerve cells are “not CONTINUOUS but CONTIGUOUS”

o https://www.youtube.com/watch?v=Wj3C6cLqXzY

LO 3: Students will be able to identify the basic functional unit of the brain and describe the function of the major components of the neuron.

Neuron• Structure: o https://www.youtube.com/watch?v=vyNkAuX29OU

Structure (Continued)• Dendrites (MICROPHONE)

oBranched projections of the neurons that propagate the signal from the previous axon

• Cell body (AMPLIFIER)oNucleus

• Axon (SPEAKER)oAxon (synaptic) terminals oMyelin Sheath

Myelin Sheath • The insulating envelope of myelin that surrounds

the core of a nerve fiber or axon • The myelin sheath facilitates the transmission of

nerve impulses• It is formed from the cell membrane of the

Schwann cell in the peripheral nervous system and from oligodendroglia cells.

• Nodes of Ranvier—gaps in myelin sheath through which the electrical signal “jumps”

WITH SHEATH: 75-80 m/s

WITHOUT SHEATH: 0.5-2 m/s

CLINICAL CORRELATE: Multiple Sclerosis

• Autoimmune demyelinating disease• 30/100,000 people globally (2-2.5 million)• 18,000 deaths in 2012• Symptoms show in late 20s and early 30s• Signs and Symptoms:

o Loss of sensitivityo Change in sensation (tingling, pins and needles)o Muscle spasmso Difficulty with coordination and balance

LO 4:• Students will describe how scientists and

physicians use technology to view the living brain, including CT, MRI, and fMRI.

CT (X-ray Computed Tomography)

MRI (Magnetic Resonance Imaging)

fMRI (Functional MRI)

CT vs MRI