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

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

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

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

Spinal Tracts

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

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

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

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

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

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)

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

Peripheral Nervous System

http://www.aqnt.com.au/images/SRA_Graph.gif

http://classes. midlandstech http://classes.midlandstech.edu/carterp/Courses/bio210/chap13/210_figure_13_20_labeled.jpg

http://2.bp.blogspot.com/-Hdz81mh8s70/VeQGZKHIz-I/AAAAAAAAA6E/yy7XPPMIEw4/s1600/babinski.jpg https://classconnection.s3.amazonaws.com/467/flashcards/941467/png/picture26-13F5AA29F40344BC330.png