1. Central Nervous System (CNS) - brain and spinal cord, which integrate, process, and coordinate sensory input/motor output, and control higher functions such as intelligence, memory, learning, and emotion
2. Peripheral Nervous System (PNS) - all neural tissue outside the CNS,which provide sensory information to the CNS and carry motor commands from CNS to peripheral tissues & systems

1. Afferent division - brings sensory information to the CNS
2. Efferent division - carries motor commands to muscles & glands

• Isolate the neurons
• provide a supporting framework for neural tissue
• help maintain the intercellular environment because neural tissue canot withstand changes that the rest of the body can
• act as phagocytes
• 100 billion neuroglia, which is 5x the number of neurons

• CNS - astrocytes, oligodendrocytes, microglia, and ependymal cells
• PNS -  satellite cells, schwann cells
• Oligodendrocytes & schwann cells have similar function
• Astrocytes/ependymal cells have function similar to satellite cells

• Control the interstitial environment (facilitate exchange of ions/molecules and feet of processes cover most of the neuron surface)
• Maintain blood-brain barrier (feet also cover capillaries so that general circulation concentrations do not upset the delicate balance in the brain)
• Provide 3D framework (reinforcement & support of neurons with microfilaments)
• Repair of damaged neural tissue (structural repairs/scar tissue limit additional damage)
• Guiding neuron development in embryonic brain

• Microglia - remove cell debris, waste, & pathogens by phagocytosis
• Ependymal cells - line brain ventricles and central canal of spinal cord, assist in producing, circulating, and monitoring cerebrospinal fluid

• Satellite cells - surround neron cell bodies in peripheral ganglia, regulate exchange of nutrients & waste products between the cell bodies and extracellular fluid, isolate neurons from stimuli other than those provided at synapses
• Schwann cells - Sheath peripheral axons, responsible for myelination of said axons although all are wrapped in schwann cells whether they are myelinated or unmyelinated 

1. Anaxonic neuron - no anatomical difference between axon and dendrites, found only in CNS
2. Bipolar neuron - dendritic branches fuse into a single dendrite string, which attaches to cell body, axon, and synaptic terminal, rare, with unmyelinated axons                     >--O--<
3. Pseudounipolar neuron - Looks like bipolar, except cell body is off to one side, and both single strings are axons, most sensory neurons of PNS are pseudounipolar
4. Multipolar neuron - Dendrite branches attached to cell body, axon length off back attached to synaptic terminal, most common

Receptors may be either the processes of specialized sensory neurons or cells monitored by sensory neurons The three catagories are:

1. Exteroceptors - provide info about the external environment from touch, temp, pressure, and more complex special senses (sight, smell, hearing) (carried by somatic sensory nerves)
2. Proprioceptors - monitor the position and movement of skeletal muscles and joints (info on internal environment, carried in somatic sensory nerves)
3. Interoceptors - monitor the digestive, respiratory, cardiovascular, urinary, and reproductive systems and provide sensations of deep pressure and pain, as well as taste (info carried by visceral sensory neurons)

1. Sensory neurons (including receptors)

2. Motor neurons (efferent division)

3. Interneurons (situated between sensory & motor neurons)

• The presence of absense of a myelin sheath (myelinated axons conduct impules 5-7 times faes than unmyelinated)
• The diameter of the axon (the larger the diameter, the faster the impulse is conducted)

• Arrival of action potential at terminal boutons trigger release of neurotransmitter from vesicles at the presynaptic membrane
• The neurotransmitter diffuses across the synaptic cleft and binds to receptors on the postsynaptic membrane
• Receptor binding results in a change in the permeability of the postsynaptic cell membrane, and will create either an excitatory (which promotes the generaton of action potentials) or inhibitory (which reduce the ability to generate an action potential) effect
• If the degree of excitation is sufficient, receptor binding may lead to the generation of an action potential in the axon (or sarcolemma if the postsynaptic cell is a skeletal muscle fiber)
• Action potentials are short lived, so inorder to prolong or enhance the effects, additional action potentials must arrive at the synaptic terminal to complete this process

1. Divergence (One cell synapses on two cells, and each of those two cells synapses on another few cells, etc to spread information)
2. Covergence (2 or more cells synapse onto one cell to permit variable control of motor options)
3. Serial processing (One synapses one another single one which synapses on another single one - straight line)
4. Parallel processing (One synapses on 2 or more, which then continue in series)
5. Reverberation (One cell synapses on another cell. This 2nd cell synapses on the first cell & a 3rd cell)

• They are organized into groups, called nuclei, with specific functions.  (Sensory nuclei receive and relay sensory information from peripheral receptors; motor nuclei issue motor commands to peripheral effectors)
• The posterior (dorsal) gray horns contain somatic and visceral sensory nuclei, whereas the anterior (ventral) gray horns contain neurons concerned with somatic motor control, and visceral motor nuclei are located in the lateral gray horns
• (The gray commissures, which connect the each side of horns, contain interneuron axons crossing from one side of the cord to the other)

1. Epineurium (outermost layer)
2. Perineurium - wraps fasicles (bundles of axons within nerve)
3. Endoneurium (innermost wrapping - surround individual axons)

A reflex is an immediate involuntary motor response to a specific stimulus.  A reflex arc is the neural "wiring" of a single reflex, which begins at a receptor and ends at an effector.

The steps involved are as follows:

1. Arrival of stimulus and activation of receptor
2. Activation of a sensory neuron
3. Information processing in CNS
4. Activation of a motor neuron
5. Response by effector

1. Based on their development (innate vs. aquired)
2. Based on the response (somatic vs. visceral)
3. Based on complexity of the circuit (monosynaptic vs. polysynaptic)
4. Based on processing site (spinal reflexes vs. cranial reflexes)

• Cerebrum (largest portion) - conscious thought processes, intellectual functions, memory storage/processing, conscious & subconscious regulation of skeletal muscle contractions
• Diencephalon - Thalmus has relay & processing centers for  sensory info, hypothalmus has centers controlling emotions, autonomic functions and hormore production
• Cerebellum - Coordinates complex somatic motor patterns, adjusts output of other somatic motor centers in brain and spinal cord

 and the brain stem made up of the:

• Mesencephalon - Processing of visual & auditory data, generation of reflexive somatic motor responses, maintainance of consciousness 
• Pons - Relays sensory info to cerebellum & thalmus, subconscious somatic & visceral motor centers
• Medulla oblongata - Relays sensory info to thalmus and to other portions of the brain stem, autonomic centers for regulation of visceral function (cardiovascular, respiratory, and digestive system activities)

• Bones of the skull
• Cranial meninges
• Cerebrospinal fluid
• Blood-brain barrier
• Vessels of cardiovascular system

1. Each hemisphere receives sensory info from & generates motor commands to the opposite side of the body
2. The 2 hemispheres have some functinal differences, although anatomically they look identical

The lobes are names based on the bone that resides on them. They are separated by the sulci/gyri.

• Subconscious control and intergration of skeletal muscle tone
• the coordination of learned movement patterns
• Processing, intergration, and relay of info from the cerebral cortex to the thalamus
• Provide the general pattern and rhythm for movement

• Establishment of emotional states and related behavior
• Linking the conscious, intellectual functions of the cerebral cortex with the unconscious & autonomic functions of other portions of the brain
• Facilitating memory storage and retrieval

• Epithalmus - controls circadian rhythm (day/night cycle)
• Thalamus - final relay point for ascending sensory info, filters info  & passes on a small portion
• Hypothalamus - Coordinates activities of the nervous & endocrine systems (which maintain homostasis), emotional & visceral processes (such as hunger/thirst, sex drive)

• Coordinates involuntary skeletal muscle movement & muscle tone
• Relays info to/from brain and spinal cord
• Sensory & motor nuclei for 4 cranial nerves

• Adjusts the postural muscles of the body
• Programs & fine-tunes  voluntary and involuntary movements  (stores memories of learned movement patterns)

• Relay stations along sensory or motor pathways
• Nuclei of cranial nerves
• Autonomic nuclei (vital functions including respiratory/cardiovascular - if medulla oblongata is severed, patient will likely die) 

Oh, Once One Takes The Anatomy Final, Very Good Vacations Are Heavenly

Olfactory

Optic

Oculomotor 

Trochlear

Trigeminal

Abducens

Facial

Vestibulocochlear 

Glossopharyngeal

Vagus

Accessory

Hypoglossal

1. Olfactory - special sensory (smell)
2. Optic - special sensory (vision)
3. Oculomotor - motor (eye movement)
4. Trochlear - motor (eye movement)
5. Trigemenal - mixed (opthalmic/maxillary = sensory, mandibular = mixed)
6. Abducens -  motor (eye movement)
7. Facial - mixed (sensory & motor)
8. Vestibulocochlear - special sensory (vestibular branch - balance & equilibrium, cochlear branch - hearing)
9. Glossopharyngeal - Mixed (swallowing)
10. Vagus - Mixed (motor is for somatic palate/pharynx and visceral respiratory, cardiovascular and deigestive organs) (only cranial nerve that extends beyond head/neck)
11. Accessory - Motor (palate, pharynx, larynx, sternocleidomastoid, & traps)
12. Hypoglossal - Motor (tongue movements)

• Sensation - sensory info arriving at the CNS
• Perception - conscious awareness of a sensation (many sensations occur without perception)
• General senses - refers to sensations of temp, pressure, pain, touch, vibration, proprioception (body position). General sensory receptors are distributed throughout the body 

• Receptor specificity - Each receptor is sensitive to a specific characteristic sense. For example, a touch receptor is quite sensitive to pressure but relatively insensitive to chemical stimuli
• Receptor field - the area monitored by a single receptor cell.  The larger the field, the poorer our ability to locate a stimuli.

• Tonic receptors - always active, with info sent to CNS based on frequency of action potential
• Phasic receptors - normally inactive, but become active for a short time whenever there is a change in the conditions they are monitoring, with info sent to CNs based on intensity of stimulus.

Adaptation is a reduction in sensitivity in the presence of a constant stimulus.

• Peripheral (sensory) adaptation occurs when the receptors or sensory neurons alter their level of activity.  They respond strongly at first, but thereafter the activity along afferent fibers gradually declines
• Central adaptation involves active receptors but an inhibition of nuclei along a sensory pathway. In essence, the CNS "ignores" the action potential

1. Humans do not have receptors for every possible stimuli (ex. we cannot see heat)
2. Our receptors have characteristic ranges of sensitivity (ex. visible wavelengths of light)
3. A stimulus must be interpreted by the CNS.  Our perception of a particular stimulus is an interpretation and not always a reality (ex. phantom pains on amputee)

Location:

1. Exteroceptors - provide info about the external environment

2. Proprioceptors - monitor body position

3. Interoceptors - monitor conditions inside the body

Nature of stimulus:

1. Nociceptors - respond to a variety of stimuli, usually associated with tissue damage.  Receptor activation causes the sensation of pain
2. Thermoreceptors - respond to changes in temperature
3. Mechanoreceptors - stimulated/inhibited by physical distortion, contact, or pressure on their plasmalemmae
4. Chemoreceptors - monitor the chemical composition of body fluids and respond to the presence of specific molecules

• Unencapsulated receptors are more easily activated (more sensitive), but they cannot give info about the degree of the stimulus (either on or off). Includes free nerve endings, root hair plexus, and merkel cells
• Encapsulated receptors are less sensitive, but once they are activated, they are able to give info about the degree of the stimulus.  They include tactile corpuscles (aka Meissner's - sperm), ruffini corpuscles, and lamellated corpuscle's (aka pacinian - print)

• A specialized neuroepithelium, the olfactory epithelium, which contains the bipolar olfactory receptors, supporting cells, and basal (stem) cells
• An underlying layer of loose connective tissue known as the lamina propria.  This layer contains olfactory glands, which produce a thick, pigmented mucus, blood vessels, and nerves.

Taste buds lie along the sides of epithelial projects called papillae. The 3 types are:

1. Filiform (thread-like)
2. Fungiform (mushroom-shaped)
3. Circumvallate (round walls)

Taste receptors are clustered within individual taste buds

1. External ear - auricle, or pinna (flexible piece which funnels sound), which surrounds the external acoustic meatus.  The tympanic membrane (eardrum) facilitates the passage of sound and ends the external portion
2. Middle ear - tympanic cavity (air-filled space) houses the auditory ossicles (malleous, incus, stapes) which conduct sound, and auditory tube(pressure equalizer)
3. Inner ear - Cochlea (hearing-snail shell) and vestibule (equilibrium - snail head), and semicircular canals (snail antennae)

1. Sound waves arrive at the tympanic membrane
2. Movement of the tympanic membrane causes displacement of the auditory ossicles
3. Movement of the stapes at the oval window establishes pressure waves in the perilymph of the vestibular duct
4. The pressure waves distort the basilar membrane on their way to the round window of the tympanic duct
5. Vibration of the basilar membrane causes vibration of hair cells against the tectorial membrane, resulting in hair cell stimulation and neurotransmitter release
6. Information concerning the region and intensity of stimulation is relayed to the CNS over the cochlear branch of N VIII