Subdivisions
• CNS - central– Brain and spinal cord enclosed in
bony coverings
• Peripheral Nervous System– Nerve = bundle of nerve fibers in
connective tissue– Ganglion = swelling of cell bodies in
nerve
Brain
Cranial Nerves
Autonomic (involuntary) motor nerves
Somatic (voluntary) Sensory Nerves
Spinal Nerves
PNS
Spinal Cord
Fundamental Types of Neurons
• Sensory (afferent)– Receptors detect changes in body
and external environment– Information transmitted to brain or
spinal cord
• Interneurons (association neurons)– link sensory & motor pathways in CNS– 90% of our neurons are interneurons– Process, store & retrieve info
Fundamental Types of Neurons
• Motor (efferent) neurons– Send signals out to muscles and
gland cells– Organs that carry out responses
called effectors
Fundamental Types of Neurons
Fundamental properties of neurons
• Excitability (irritability) – Ability to respond to changes in the body
and external environment called stimuli
• Conductivity– Produce traveling electrical signals
• Secretion– When electrical signal reaches end of nerve
fiber, a chemical neurotransmitter is secreted
Neuron structure
• Cell body = perikaryon = soma– Single, central nucleus– Cytoskeleton of microtubules &
neurofibrils
• Vast number of short dendrites• Single Axon (nerve fiber) arising
from soma– Covered in Schwann cells
Schwann cells
• Myelin coated
• Neurilemma– Outer layer of SC– Brain/Spinal Cord do not have
• Nodes of Ranvier• Glia - “glue” that holds nerons together
Multiple sclerosis
• Myelin disorder– Myelin loss/oligodendrocyte damage– = demyelinization of white matter in
CNS– Hard, plaque-like lesions -->
inflammation– Nerve conduction impaired– More common women 20-40yrs
Nerves• Groups of peripheral nerve fibers
(axons) - like cables– Covered in myelin = look white
• Axons in CNS (tracts) = white matter• Gray matter - unmyelinated dendrites
and axons
Endoneurium -tissue that wraps axons
Fascicles - groups of wrapped axons
Perineurium - tissue that wraps fascicles
Epineurium - tough, fibrous sheath that covers whole nerve
Reflex Arcs
• 2 neuron arc: sensory & motor neurons– “Knee jerk”– Receptor of sensory neuron--> ganglion near
spinal cord --> motor neuron -->muscle
• 3 neuron arc: sensory, interneurons & motor neurons– “Withdrawal reflex”– Receptor of sensory neuron--> ganglion near
spinal cord --> interneuron --> motor neuron -->muscle
Divisions of the Brain
• Brainstem• Medulla oblongata• Pons• Midbrain
• Cerebellum• Diencephalon• Hypothalamus• Thalamus
• Cerebrum
http://www.youtube.com/watch?v=snO68aJTOpM
Brainstem
• Medulla oblongata• Enlarged, upward extension of spinal cord• Powers vital centers
• Cardiac, respiratory, vasomotor
• Pons• Works with medulla - complex reflexes
• Midbrain• governs basic behaviors like eating and
walking• Work with pons - sleep, arousal
Cerebellum• Essential in normal movements
– Precise, smooth movements– Walking, drawing, hammering a nail
– processes input from other areas of the brain, spinal cord and sensory receptors to provide precise timing for movements
Diencephalon
• Hypothalamus– Impulses control glands, muscles, organs
• Heartbeat, intestines, vasomotory• ADH, RH
• Thalamus– Dumbbell-shaped– Produces sensations– Sensations with emotions– Arousal, alertness, activity
Cerebrum
• Largest part of brain• Gyri - ridge• Sulci - grooves
– Fissure - deep sulci• Basal ganglia
– Gray matter in white matter– Automatic movements
Cerebrum• Corpus callosum -
connects left and right hemispheres
• Cerebral Cortex - layer of gray matter covering the cerebrum
Peripheral Nervous System (PNS)
• Made up of– Cranial nerves
• 12 pairs• conduct impulses from face/body to brain
– Table 9-2 p.921
– Spinal nerves• 21 pairs• Conduct impulses from body to spinal
cord
Peripheral Nervous System (PNS)
• Dermatomes - skin areas that map to a spinal cord region– Can use this
to detect region of cord injury
Peripheral Nerve Disorders
• Neuritis - inflammation of nerves• Sciatica - neuritis of sciatic nerve• Neuralgia - nerve pain• Bell’s palsy• Herpes zoster
Autonomic Nervous System
• From spinal cord/brainstem to tissue– Cardiac muscle tissue– Smooth muscle tissue– Glandular epithelial tissue
• Regulates involuntary functions– Heartbeat/intestines/gland secretions
Autonomic Nervous System
• Divisions of the ANS:
– Sympathetic nervous system• Emergency system: “fight or flight”
– Vasoconstriction, increased heart rate, decreased peristalsis
• Norepinephrine (NE)
– Parasympathetic nervous system• Normal daily functions
– Peristalsis, secretion of digestive juices/insulin• Acetylcholine (Ach)
1. Action Potential2. Vesicles Fuse3. NT released4. NT crosses synapse5. Binds with receptors6. New Action Potential Fires7. Reuptake of NT
Nerve Impulse
Other NTs (are many more):• Dopamine• Epinephrine• Serotonin• Histamine