The Nervous System

Charles C. Cook, MD

Divisions of the Nervous System

The Central Nervous System

• Brain and Spinal cord

• Processes sensory information

• Produces a response

The Central Nervous System

Peripheral Nervous System

Nerves that connects muscles, receptors, and glands so ….

Sensory nerves sends info from the receptors to the CNS

Motor nerves sends info from the CNS to muscles and glands

Peripheral Nervous System

Peripheral Nervous System Sensory Nerves

Peripheral Nervous System Motor Nerves

Peripheral Nervous System Autonomic Nervous System

PNS that controls internal organs

Autonomic Nervous System

Grouping of Neural Tissue

Nerve

Fibers located outside the CNS, held together by

connective tissue

White matter

Aggregations of myelinated processes of

many neurons

Gray Matter

Contains either nerve cell bodies or bundles of

unmyelinated nerve fibers

Reflexes

Reflex Arcs

Behavioral unit of the nervous system

Structural and functional basis for the simplest involuntary actions

Reflex Behavior

Automatic and unconsciousChanges inside or outside

Maintain HomeostasisHeart rate, breathing rate,

swallowing……

Examples of Reflexes

Protection & Covering of CNS

Cranial Bones

Vertebral Bones

Meninges

Membranes that cover brain and spinal cord

Serve as bacterial barriers

Meninges (cont)

Dura mater (tough mother)

• Outermost layer

• Composition is white fibrous connective tissue, blood vessels and nerves

Meninges (cont)

Dura mater

• Cranium —attached to bone (skull)

• Spinal cord —surrounded by adipose (fatty) tissue

Meninges (cont)

Arachnoid

• Web-like

• Lacks blood vessels

• Located between dura mater and pia mater

Meninges (cont)

Pia mater (gentle mother)• Innermost layer• Attached to organ surface

–Nerves and many blood vessels

Meninges (cont)

Subarachnoid Space

• Fluid filled

• Between arachnoid mater and pia mater

Ventricles and Cerebrospinal

fluid (CSF)

Ventricles

Cavities within the cerebral hemispheres

and brain stem

Cerebrospinal Fluid

Clear watery fluid secreted within ventricles

Circulates within ventricles and subarachnoid space

Protects and supports CNS

Spinal Cord

Structure

Base of skull to 1st lumbar vertebrae

Core gray matter surrounded by white matter

Structure

Give rise to 31Pairs of spinal nerves

Inferiorly, splits into cauda equina

Function

Conduct nerve impulsesCenter for spinal reflexes

Cerebrum

Largest part of the mature brain

Cerebrum structure

Cerebral hemispheres

(Thinking Caps)

Mirrored large masses of the brain

Cerebrum structure

Fissure

Deep furrows

Cerebrum structure(Cont)

Corpus callosum

Nerve fibers that connect hemispheres

Cerebrum structure(Cont)

Exterior - Gray matterInterior - White matter

Cerebral lobes (regions)

Frontal lobeParietal lobeTemporal lobeOccipital lobe

Cerebral Lobes

Frontal lobe

Higher thought processes, reasoning, logic

Planning, concentration, and emotions

Parietal lobe

General sensations (Hot or Cold, Pressure or Pain)

Understanding speech

Temporal lobe

Special sensations (Hearing, Taste, Smell)

Memory of visual and auditory patterns

Occipital lobe

Sight and recognition of objects

Diencephalon

Diencephalon

• Forms central core of forebrain and consists of:

--Thalamus

--Hypothalamus

Thalamus

Relays all sensory impulses to cerebral cortex (except smell)

Understanding speech, light, touch and pressure

HypothalamusControls heart rate, blood pressure, and

body temp. (Autonomic Nervous System)

Receives sensory impulses from internal organs

Connects nervous w/ endocrine system Controls release of regulating hormones

from anterior pituitary gland

Brainstem

Brainstem

• Regions include the following:

--Midbrain

--Pons

--Medulla Oblongata

Midbrain

• Between hypothalamus and the pons

• Visual and auditory reflex centers

Pons

• Separates midbrain/medulla oblongata

• Helps regulate breathing

Medulla oblongata• Continuation of spinal cord

from pons to the base of skull

• Transmits impulses, Contains vital visceral centers

Medulla oblongata

• Cardiac center Vasomotor

center Respiratory

center

Cerebellum• Second largest structure of the brain

• Below the occipital lobes of the cerebrum, posterior to the pons and the medulla oblongata.

• Consists of two hemispheres-connects by a vermis

• Functions primarily in coordination of skeletal muscle movement and maintaining posture

Peripheral Nervous System

(PNS)

Peripheral Nervous System

• Cranial Nerves

• Spinal Nerves

• Plexus

Cranial Nerves

• 12 pair

• All arise from brainstem (Except CN 1 ---Optic Nerve)

• Most are mixed nerves

Spinal Nerves

• 31 pair

• All arise from spinal cord

• All are mixed nerves

• Emerges as Roots

Spinal Nerves

• Cervical Nerves - C1-C8

• Thoracic Nerves - T1-T12

• Lumbar Nerves - L1-L5

• Sacral Nerves - S1-S5

• 1pair of Coccygeal nerves

Plexus

Formed by combining branches of several spinal nerves

(Except in the Thoracic Region)

Cervical Plexus

• C-1 through C-4• Innervates muscles and skin of

neck• Forms Phrenic nerve which

innervates the Diaphragm

Cervical Plexus

Brachial Plexus

C-5 through T-1

Innervates muscles and skin of arms, forearms & hands

Brachial Plexus

Lumbosacral Plexus

T-12 through S-5Innervates lower extremity

Lumbosacral Plexus

Summary

• Divisions of the Nervous System

• Neural Tissue

• Behavior of Reflexes

• Functions of the Central Nervous System

• Functions of Spinal Cord

Summary

• Functions of Cerebrum

• Components of Diencephlon

• Functions of Brain Stem

• Functions of Cerebellum

• Components of Peripheral Nervous System