sensory input motor input sensory receptor effector integration

sensory input motor input sensory receptor effector integration

Central Nervous System (CNS) • brain • spinal cord Peripheral Nervous System (PNS) • cranial nerves • spinal nerves

CNS brain spinal cord NS PNS (spine & cranial nerves) SNS (voluntary) ANS (involuntary) • Sensory (afferent) • Motor (efferent) Sympathetic Parasympathetic

CNS PNS brain cranial nerves spinal cord spinal nerves

dendrite cell body Myelin sheath axon Synapse

Schwann Cells Axon Nodes of Ranvier

unipolar bipolar Dorsal root eye, ear, & olfactory ganglion cells multipolar most abundant type in CNS

sensory neuron interneuron motor neuron sensory receptors effector

Ca 2+ Presynaptic neuron Postsynaptic membrane Synaptic vesicles containing neurotransmitters

• • • Acetylcholine- slows heart rate; PNS Glutamate- most prevalent neurotransmitter in the brain Aspartate- in CNS GABA- inhibitory neurotransmitter Glycine- inhibitory neurotransmitter Norepinephrine- awakening from deep sleep tyrosine Epinephrine- increase heart rate Dopamine- movement of skeletal muscles Seratonin- sensory perception, temp regulation, mood, sleep Nitric oxide- may play a role in memory and learning Enkephalin- inhibit pain impulses by suppressing release of substance P Substance P- enhances perception of pain

Converging circuit • same source • Pacinian corpuscles -- pressure • different sources • control of respiration Diverging Circuit • permits broad distribution of a specific input • types • A. amplification • B. divergence into multiple tracts

Parallel after-charge circuit • several neurons process same information at one time • each chain has a different number of synapses, but eventually they all reconverge on a single output • output neuron may go on firing for some time after input has ceased • important in withdrawal reflexes • longer-lasting output from small period of pain

Reverberating Circuit • axons extend back toward the sources of an impulse and further stimulate the presynaptic neuron • helps maintain consciousness, muscular coordination, normal breathing, short term memory. . .

Integration center Affe rent (sen sory ) synapses Effe r) o t o (m t n e r

chromatolysis Wallerian degeneration

Myelin sheath cell body axon chromatolysis Shwann cell Wallerian degeneration Regeneration tube