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
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
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
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
• 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
• 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
Brachial Plexus
C-5 through T-1
Innervates muscles and skin of arms, forearms & hands
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