1. The Human Nervous System
Central Nervous
System
(CNS)
Peripheral Nervous
System
(PNS)
Brain
Spinal Cord
Sensory
(afferent)
Motor
(efferent)
Autonomic Nervous
System (ANS)
(involuntary)
Somatic Nervous
System
(voluntary)
Sympathetic Nervous
System
Parasympathetic Nervous
System

2. Spinal Cord Communication pathway between the brain and the body.
Allows signals to pass down to control body function and up to inform the brain of what is happening in the body

3. Anatomy of the Spinal Cord
Cord lies within the spinal column
Consists of nerve cells and bundles of nerves (31 pairs)
Cord is enlarged in the region of the neck and lower back
Cervical enlargement: C3-L2 -> origin of nerves to the upper limbs
Lumbar Enlargement: L9-L12 -> origin of the nerve supply to the lower limbs and pelvis
Conus medullaris: cone shaped end of the spinal cord
Cauda equina: bundle of nerve roots in the lower part of the spinal column

5. Spinal Tracts
Tract: collection of nerve axons which all have the same origin, destination, and function
Ascending tract: carry sensory information from the body to the brain.
Descending tracts: carry signals from the brain to the body. They are involved with the control of movement

6. Spinal Tracts

7. Spinal Nerves 31 pairs of nerves Each nerve has two roots
Grouped by region
Each nerve has two roots
Anterior (ventral) root: contains the axons of motor nerves which send impulses to control muscle movement
Dorsal root: contains axons of sensory nerves which send sensory information from the body into the spinal cord on its wat to the brain

8. Stop and think… What happens when you accidently touch a hot plate?
What are two human reflexes that you can think of?

10. Sympathetic and Parasympathetic Divisions
Sympathetic- “fight-or-flight”- rapid heart rate; deep breathing; dry mouth; cold, sweaty skin; dilated pupils
During vigorous physical activity- constricts blood vessels, bronchioles dilate, liver releases more glucose to blood, all nonessential activities are slowed
Parasympathetic- “resting & digesting”- keeps body E use as low as possible as it directs vital activities (digestion, elimination of wastes, etc)
Blood pressure & heart rate regulated at low normal levels while gastrointestinal tract actively digests

11. Sensory Receptors
Specialized to respond to changes in environment (stimuli)
Mechanoreceptors- touch, pressure, vibration, stretch
Thermoreceptors- temp
Photoreceptors- light E
Chemoreceptors- chemicals in solution
Nociceptors- pain receptors- respond to potentially damaging stimuli

12. Reflex Arc Highly specific neural pathways- 5 components Reflex Arc
1) Receptor- site of stimulus action
2) Sensory neuron- transmits afferent impulses to CNS
3) Intergration center- always in CNS
may be 1 synapse
between sensory
& motor neuron
or multiple synapses
with chains of
interneurons
4) Motor neuron-
transmits efferent
impulses
5) Effector- muscle fiber or gland that responds

13. Reflexes Intrinsic (inborn) reflexes Acquired (learned) reflexes
Usually rapid, predictable motor response to stimulus
Many cases we are aware of reflex, some go without awareness (visceral reflexes are regulated by lower regions of CNS- brain stem & spinal cord)
Acquired (learned) reflexes
Result from practice & repetition
Pavlov’s Dog (conditioned reflexes)

14. Types of Reflexes Spinal Reflexes
Superficial reflexes- elicited by gentle cutaneous stimulation
Plantar reflex- elicited by drawing a blunt object downward along lateral aspect of the plantar surface
Normal response: Downward curling of toes, tests integrity of spinal cord from L4 to S2
Babinski’s sign- great to dorsiflexes & smaller toes fan laterally
Seen in infants up to about 1yr, nervous system is not completely mylineated yet
Plantar Reflex
Babinski’s sign- damage on right side
Babinski’s sign- Infant

15. Peripheral Nervous System

17. http://classes. midlandstech