2. Afferent Division of the Nervous System
Sensory pathways (15-1 to 15-4 & 17)
Efferent Division of the Nervous System
Motor pathways
Somatic Nervous system (15-5)
Autonomic Nervous system (16-1 to 16-7)

3. LECTURE OUTLINE:
Compare Somatic Nervous System (SNS) with Autonomic Nervous System (ANS)
Autonomic Nevous system: Compare Sympathetic divison and Parasympathetic division

4. Efferent Division of Nervous System
The Somatic Nervous System (SNS) 15-5
Also called the somatic motor system
Controls contractions of skeletal muscles
The Autonomic Nervous System (ANS)
Also called the visceral motor system
Controls visceral effectors, such as smooth muscle, cardiac muscle, and glands

5. EFFERENT DIVISION OF NERVOUS SYSTEM
Somatic
Autonomic
Effectors – Skeletal muscles
Effectors – Smooth, Cardiac muscles and glands
Conscious (voluntary) and Unconscious regulation
Unconscious (Involuntary) regulation
Excitatory action – skeletal muscle contracts
Excitatory and Inhibitory action of target tissues
Single synapse
Two synapses – preganglionic and ganglionic neurons
Neurotransmitter- Acetylcholine
Neurotransmitter - Acetycholine by preganglionic neurons and ACh or norepinephrine/epinephrine by postganglionic neurons
Seldom effects long term survival
Critical for homeostasis and survival

6. The Organization of the Somatic Nervous Systems
Upper motor neurons in primary motor cortex
BRAIN
Somatic motor nuclei of brain stem
Skeletal muscle
Lower motor neurons
SPINAL CORD
Somatic motor nuclei of spinal cord
Skeletal muscle
Somatic nervous system 6

7. Preganglionic neurons
The Organization of the Autonomic Nervous Systems
Visceral motor nuclei in hypothalamus
BRAIN
Preganglionic neuron
Visceral Effectors
Smooth muscle
Autonomic nuclei in brain stem
Autonomic ganglia
Glands
Cardiac muscle
Ganglionic neurons
SPINAL CORD
Adipocytes
Autonomic nuclei in spinal cord
Preganglionic neurons
Autonomic nervous system 7

8. 15-5 Somatic Motor Pathways
The Somatic Nervous System (SNS)
Also called the somatic motor system
Provides voluntary (conscious) control over skeletal muscles

9. Somatic Nervous System (SNS)
Always involve at least two motor neurons
Upper motor neuron
Lower motor neuron

10. Somatic Nervous system (SNS)
Upper motor
neurons in
primary motor
cortex
BRAIN
Somatic motor
nuclei of brain
stem
Skeletal
muscle
Lower
motor
neurons
Spinal cord
Figure 14 Section 1 The Functional Anatomy and Organization of the Autonomic Nervous System (ANS)
Somatic
motor
nuclei of
spinal cord
Skeletal
muscle 10

11. Upper Motor Neuron
Pyramidal neurons of Precentral gyrus of frontal lobe
All of these neurons are located in CNS
Descending tracts containing fibers of these neurons go to brainstem or the spinal cord
Fibers decussate: Hence each precentral gyrus controls muscles on the contralateral side of the body
Once reach brainstem or spinal cord, upper motor neuron synapses on the lower motor neuron

12. Lower Motor Neuron
Cell body lies in a nucleus of the brain stem or spinal cord
Axon of lower motor neuron extends outside CNS
Innervates a single motor unit in a skeletal muscle (effector); triggers contraction of muscle
May also be controlled by reflexes based in spinal cord
Destruction of or damage to lower motor neuron eliminates voluntary and reflex control over innervated motor unit

13. Conscious and Subconscious Motor Commands control skeletal muscles by traveling over three integrated motor pathways
Corticospinal pathway
Medial pathway
Lateral pathway

14. Motor Homunculus
Map of primary motor cortex showing control of skeletal muscles
Like sensory homunculus, corresponds point by point with specific regions of the body
Motor area devoted to a specific area is proportional to number of motor units involved in the region’s control

15. Figure 15-8 The Corticospinal Pathway
Motor homunculus on primary motor cortex of left cerebral hemisphere
KEY
Axon of upper motor neuron
Lower motor neuron
To skeletal muscles
Corticobulbar tract
Motor nuclei of cranial nerves
Cerebral peduncle
To skeletal muscles
Midbrain
Motor nuclei of cranial nerves
Medulla oblongata
Decussation of pyarmids
Pyramids
Lateral corticospinal tract
Anterior corticospinal tract
To skeletal muscles
Spinal cord 15

16. Levels of Processing and Motor Control
All sensory and motor pathways involve a series of synapses, one after the other
Spinal and cranial reflexes provide rapid, involuntary, preprogrammed responses that preserve homeostasis over short term
Control the most basic motor activities
Voluntary responses are more complex and require more time to prepare and execute
Nervous system motor disorders may result from problems with neurons, pathways, or a combination of the two

17. Multiple levels of somatic motor control
The flow of information as an individual
begins a movement
Primary
motor
cortex
Motor
association
areas
Cerebral
cortex
Basal
nuclei
As the movement proceeds,
the cerebellum monitors
proprioceptive and vestibular
information and compares
the arriving sensations with
those experienced during
previous movements. It then
adjusts the activities of the
upper motor neurons
involved.
The basal nuclei adjust patterns
of movement in two ways:
1. They alter the sensitivity of the
pyramidal cells to adjust the
output along the corticospinal
tract.
2. They change the excitatory or
inhibitory output of the medial
and lateral pathways.
Other nuclei of
the medial and
lateral pathways
Cerebellum
Corticospinal
pathway
Lower
motor
neurons
Motor activity 17

18. Nervous system disorders
may result from problems with neurons, pathways, or a combination of the two
Parkinson disease
When substantia nigra neurons are damaged or secrete
less dopamine
The substantia nigra from individuals with and
without Parkinson disease
Figure Nervous system disorders may result from problems with neurons, pathways, or a combination of the two
Normal substantia nigra
Diminished substantia
nigra in Parkinson patient 18

19. Amyotrophic Lateral Sclerosis (ALS)
Commonly known as Lou Gehrig’s disease
Progressive degenerative disorder
Affects upper and lower motor neurons in the spinal cord, brain stem and cerebrum
Atrophy of associated skeletal muscles
Stephen Hawkings

20. Cerebral palsy (CP)
Refers to a number of disorders that affect voluntary motor performance
Appears during infancy or childhood and persists throughout life
Cause may be:
Trauma associated with premature or stressful childbirth
Maternal exposure to drugs (including alcohol)
Genetic defect that causes improper motor pathway development

21. Preganglionic neurons
The Organization of the Autonomic Nervous Systems
Visceral motor nuclei in hypothalamus
BRAIN
Preganglionic neuron
Visceral Effectors
Smooth muscle
Autonomic nuclei in brain stem
Autonomic ganglia
Glands
Cardiac muscle
Ganglionic neurons
SPINAL CORD
Adipocytes
Autonomic nuclei in spinal cord
Preganglionic neurons
Autonomic nervous system 21

22. The Autonomic Nervous
Sympathetic division
Increases alertness, metabolic rate, and muscular abilities
Parasympathetic division
Reduces metabolic rate and promotes digestion
Enteric division:
Extensive network in digestive tract walls
Influenced by sympathetic and parasympathetic division but also under local control

23. Responses to Increased Sympathetic Activity
“Fight or Flight”
Increased blood glucose level for ATP production
Increased metabolic rate
Increased respiratory rate and respiratory passageways dilate
Increased heart rate and blood pressure
Increased blood flow to skeletal muscle, cardiac muscle, and liver
Heightened mental alertness
Sweat glands activated
Increase in pupil size (dilation)
Effects widespread and long lasting due to divergence of neuron connections and release of norepinephrine and epinephrine by adrenal medulla
Decreased blood flow to GI tract. Reduced digestive and urinary functions

24. Sympathetic Motor Division: Thoracolumbar
Preganglionic neurons are cholinergic neurons-release Ach
- Preganglionic fibers are short: extend from thoracolumbar region; synapse in ganglia near spinal cord
Ganglionic neurons are mostly adrenergic –release NE (some E/ACh)
- Postganglionic fibers are long and synapse at effectors
Exception: Adrenal medulla -release to bloodstream

25. Sympathetic (thoracolumbar) division of the ANS
KEY
Preganglionic fibers
Postganglionic fibers
Ganglionic neurons in
the sympathetic chain
and collateral ganglia
exert their effects
through innervation
of peripheral target
organs.
Hormones released
into circulation
Ganglionic Neurons
Target Organs
Sympathetic Chain Ganglia
consists of a series of
interconnected ganglia
located on either side of the
vertebral column.
Visceral effectors
in thoracic cavity,
head, body wall,
and limbs
Preganglionic
Neurons
Lateral gray
horns of
spinal
segments
T1-L2
Collateral ganglia,
located within the
abdominopelvic cavity,
include the celiac, superior
mesenteric, and inferior
mesenteric ganglia.
Visceral effectors
in abdomino-
pelvic cavity
Adrenal medulla
(endocrine organ).
Organs and
systems
throughout the
body
Ganglionic neurons in
the adrenal medullae
affect target organs
throughout the body
through the release of
hormones into the
general circulation. 25

26. Sympathetic (thoracolumbar) division
Eye
PONS
Salivary
glands
Sympathetic nerves
Cervical
sympathetic
ganglia
Superior
Middle
Heart
Inferior T1 T1
Splanchnic
nerves
Cardiac and
pulmonary plexuses
Celiac ganglion
Lung
Superior mesenteric
ganglion
Liver and
gallbladder
Stomach
Spleen
Pancreas
Large
intestine
Postganglionic fibers to
spinal nerves (innervating
skin, blood vessels, sweat
glands, arrector pili
muscles, adipose tissue)
Small
intestine L2
Inferior
mesenteric
ganglion L2
Adrenal
medulla
Spinal
cord
Sympathetic
chain ganglia
Kidney
Ovary
Coccygeal
ganglia (Co1)
fused together
Penis
Uterus
Urinary bladder
Scrotum
KEY
Preganglionic neurons
Ganglionic neurons 26

27. Responses to Increased Parasympathetic Activity
“Rest & Digest”
Decreased metabolic rate
Restore body energy stores
Decreased airway diameter (bronchoconstriction)
Decreased heart rate and blood pressure
Increased secretion by salivary and digestive glands
Increased motility and blood flow in digestive tract
Increased digestion, urination, defecation
Decreased pupil diameter (constriction)

28. Parasympathetic Motor Division: Craniosacral
Preganglionic neurons are cholinergic neurons-release Ach
- Preganglionic fibers are long: extend from craniosacral region; synapse in ganglia close to target organs
Ganglionic neurons are cholinergic neurons-release Ach
- Postganglionic fibers are short and synapse at effectors

29. Parasympathetic (Craniosacral) Division of ANS
Preganglionic Neurons
Ganglionic Neurons
Target Organs
N III
Nuclei in brain stem
Ciliary ganglion
Intrinsic eye muscles (pupil and lens shape)
N VII
Pterygopalatine and submandibular ganglia
Nasal glands, tear glands, and salivary glands
N IX
Otic ganglion
Parotid salivary gland
N X
Intramural ganglia
Visceral organs of neck, thoracic cavity, and most of abdominal cavity
Nuclei in spinal cord segments S2–S4
Pelvic nerves
Visceral organs in inferior portion of abdominopelvic cavity
KEY
Intramural ganglia
Preganglionic fibers
Postganglionic fibers 29

30. Pterygopalatine ganglion
The innervation of the parasympathetic division on
one side of the body; the innervation on the opposite
side (not shown) follows the same pattern
KEY
Preganglionic neurons
Ganglionic neurons
Pterygopalatine ganglion
Lacrimal gland
Eye
Ciliary ganglion
PONS
VII
III
Submandibular
ganglion
Salivary glands IX
Otic ganglion
Vagus nerve (X),
which provides
about 75 percent
of all parasympa-
thetic outflow
Heart
Cardiac plexus
Lungs
Celiac plexus
Spinal
cord
Liver and
gallbladder
Stomach
Inferior mesenteric
plexus
Spleen
Pancreas
Hypogastric
plexus
Large
intestine
Preganglionic
fibers in the
sacral segments
of the spinal cord,
which carry sacral
parasympathetic
output
Small
intestine
Rectum S2
Kidney S3 S4
Penis
Uterus
Ovary
Scrotum
Urinary bladder
Figure 14.3 30

31. Sympathetic Parasympathetic CNS PNS Preganglionic neuron
Figure Summary: The Anatomical Differences between the Sympathetic and Parasympathetic Divisions
Sympathetic
Parasympathetic
CNS
Preganglionic neuron
PNS
Preganglionic fiber
KEY
Sympathetic ganglion
Neurotransmitters
Acetylcholine
Norepinephrine or
Epinephrine
Ganglionic neurons
Circulatory system
Postganglionic fiber
Parasympathetic ganglion
TARGET 31

32. Sympathetic and Parasympathetic Division
Most vital organs receive instructions from both sympathetic and parasympathetic divisions
Organs that receive impulses from both sympathetic and parasympathetic fibers are said to have dual innervation. For example; Heart, lungs, pupil
Two divisions commonly have opposing effects For example:
Parasympathetic: ACh release decreases heart rate
Sympathetic: NE release accelerates heart rate

33. Differences Between Somatic and Autonomic Nervous Systems
Central
nervous system
Peripheral nervous system
Effector organs
Acetylcholine
Somatic nervous system
Skeletal
muscle
Acetylcholine
Norepinephrine
Smooth muscle
(e.g., in stomach)
Sympathetic
division
Ganglion
Acetylcholine
Epinephrine and
norepinephrine
Autonomic
nervous
system
Blood
vessel
Glands
Adrenal medulla
Acetylcholine
Cardiac
muscle
Parasympathetic
division
Ganglion
KEY:
Preganglionic
axons
(sympathetic)
Postganglionic
axons
(sympathetic)
Myelination
Preganglionic
axons
(parasympathetic)
Postganglionic
axons
(parasympathetic)
Figure 7.27

34. Regulation of the ANS
Simple reflexes from spinal cord provide rapid and automatic responses
Complex reflexes coordinated in brainstem, especially medulla oblongata
Contains centers and nuclei involved in:
Salivation
Swallowing
Digestive secretions
Peristalsis
Urinary function
Highest level of regulation by hypothalamus: Master controller of ANS