A & P

• Neural tube forms and sinks below surface
• a. forward end forms brain
• b. back end forms spinal cord
• fluid filled cavity becomes central canal and ventricles
• Cerebral Spinal Fluid (CSF)

• study of nervous system
• is a control system: communicates with and controls other sytems

Brain and Spinal Cord

• Sensory (afferent carry toward) Division
• a. nerve fibers (axons) that convey impulses to the CNS from sensory receptors
• Motor (efferent carry away) Division
• a. transmits impulses from the CNS to effector organs
• b. two subdivisions

• Somatic Nervous System
• a. skeletal muscle
• b. "voluntary nervous system"
• c. somatic motor nerve fibers
• Autonomic Nervous System (ANS)
• a. regulate the activity of smooth and cardiac muscle and glands
• b. "involuntary nervous system"
• c. visceral motor nerve fibers

• Sympathetic Nervous System
• a. "Fight or Flight"
• Parasympathetic Nervous System
• b. slows down body

• Neurons: functional and structural units of NS
• Neuroglia: accessory support and protective cells for neurons, function much like c.t. in other parts of body

Schwann cells- provide insulation on axon

• Astrocyte: interface nerve tissue and blood vessel
• Oligodendrocyte: provide myelin sheath
• Microglia: active and increase in number during inflammation of CNS
• Ependyma: form an epithelial like membrane that is one cell thick and covers inside spaces within brain (ventricles, central canal), important in the blood-brain barrier: choroid plexus= capillary network associated with ventricles

• Cell Body:
• a. makes neurofibrils for transporting material around neuron.
• b. centrosome (mitotic apparatus) missing
• Dendrite:
• a. short, numerous, highly branched fibers from cell body
• b. carry impulses to cell body
• Axon:
• a. usually one, long, larger, uniform in diameter process from cell body
• b. carry impulse away from cell body
• c. hillock-where leaves cell
• d. collateral-branches of axon
• e. ends specialized for synapse with another cell (presynaptic terminal)

• Sensory (afferent): to CNS
• Motor (efferent): away from CNS; to effector (muscle or gland)
• Association (interneuron): totally in CNS, between sensory and motor neurons, 90% are in this catergory

• Unipolar: one process from cell body
• ex. in ganglia of spinal nerves
• Bipolar: two processes from cell body. 1 axon 1 dendrite
• ex. special sensory- eyes, nose, ears
• Multipolar: one axon and may dendrites
• ex. in brain most are this type

Node of Ranvier

Dense collection of myelinated fibers and axon.

Mostly nerve cell bodies and dendrites

• a. collection of neuron fiber inside CNS
• b. collection of neuron fiber outside CNS

c.t around one neuron

c.t. around bundle of neurons

c.t. around all fibers; contains blood vessels, fat

• a. Sensory
• b. Motor
• c. Mixed

nerves originating from spinal cord that communicate with other body parts

originating from the brain that communicate with other body parts

collection of neuron cell bodies outside the CNS

collection of neuron cell bodies inside the CNS

• a junction between two cells
• ex. nerve-nerve, nerve-muscle, nerve-gland

before the gap

after the gap

gap between cells

• Electrical: proteins actually embedded in both cell membranes, provide channels for ion flow.
• Chemical: most fit in this category, axon with synaptic bulb that contain vesicle with neurotransmitters

time required to actually cross cleft (about .5 msec)

depletion of neurotransmitters in vesicles, cannot synthesize fast enough

• competes for Ach receptor sites
• inhibits contraction

combine with acetylcholinesterase and deactivates it: this allows continued contraction and leads to spasm

inhibits Ach release

reduce threshold for excitation and therefore result in facilitation