Unit 6 Nervous System
1. Functions of the Nervous System
a. Sensory – Incoming Signals
b. Motor – movement
c. Integrative – in brain and spinal cord only (processors/ relay terminals)
2. Parts of a Neuron
a. Soma – cell body
b. Dendrite – receives messages
c. Axon – sends messages out
d. Myelin – helps speed up messages, made up of Schwann Cells – like a coating
of insulation similar to the plastic that covers wires
3. Divisions of the Nervous System
a. Central Nervous System – control center, coordinates body functions
i. Brain
ii. Spinal Cord
b. Peripheral Nervous System – carries messages to and from the CNS, contains
motor and sensory neurons
i. Somatic
1. Cranial and spinal nerves
2. Reflexes – automatic responses to stimuli
3. Body functions – sensory and motor
ii. Autonomic
1. Involuntary
2. 2 division
a. Sympathetic – Fight or Flight Response, speeds up reactions
b. Parasympathetic – counteracts sympathetic, returns body to
normal, slows down heart rate
iii. Enteric
1. Intestines
2. Directly controls the gastrointestinal system
4. Brain
a. Weighs approximately 3lbs
b. 4 parts
i. Brain stem
1. 3 parts – continuous with the spinal cord
a. Medulla oblongata
b. Midbrain
c. Pons (Bridge)
ii. Diencephalon – contains 2 parts
1. Thalamus – principle relay station for sensory impulses and
cognition
2. Hypothalamus – maintains homeostasis
a. Control of the Autonomic Nervous System
b. Control of the pituitary gland
c. Regulation of emotional and behavioral patterns
d. Regulation of eating and drinking
e. Control of body temperature
f. Regulation of circadian rhythms and states of consciousness
iii. Cerebrum
1. 4 Lobes
a. Frontal Lobe – reasoning, movement, higher level cognition,
language
b. Parietal Lobe – pressure, touch, pain, somatosensory cortex
(sensory processing)
c. Temporal Lobe – Primary Auditory Cortex, Hippocampus
(memories)
d. Occipital Lobe – Interpreting visual information
2. Cerebral Cortex
a. Sensory – Temporal Lobe
i. Primary Somatosensory Area – receives nerve impulses
for touch, proprioception, pain and temperature
ii. Primary Visual Area – vision
iii. Primary Audiotory Area – hearing
iv. Primary Gustatory Area – taste
v. Primary Olfactory Area – smell
b. Motor – Cerebellum
i. Primary Motor Area – movement
ii. Broca’s Speech Area – Frontal Lobe – speech
production – for 97% of people, Broca’s area is located
in the left frontal lobe
1. Aphasia – inability to speak
2. Agraphia – inability to write
3. Word deafness – inability to understand spoken
words
4. Word blindness – inability to understand written
words
c. Association Areas of the Cerebral Cortex
i. Somatosensory Association Area – interprets and
integrates somatic senses
ii. Visual Association Area – takes past visual experiences
and relates them to current visual experiences recognition
iii. Auditory Association Area – speech, music or noise
1. Wernicke’s Area (temporal and parietal lobes) –
interprets the meaning of speech by translating
words into thoughts
iv. Common Integrative Area – receives, integrates and
relays sensation impulses
v. Premotor Area – motor sequences – such as the ability
to write
vi. Frontal Eye Field Area – controls voluntary scanning
movement of the eyes
3. Cerebrum and Memory
a. Memory – ability to recall thoughts
b. Controlled by the Limbic System, stored in the temporal lobe
c. Short-term – lasts seconds to hours
d. Long-term – days to years
4. Cerebum – Hemispheric Lateralization
a. 2/3 population – a region of the frontal lobe is 50% larger on
the left side than on the right side
b. Left Hemisphere – controls the right side of the body
(movements), spoken and written language, numerical/
scientific skills, reasoning
c. Right Hemisphere – controls the left side of the body
(movements), Musical, artistic, spacial perception, pattern
perception, mental images of sight, sound, touch, smell and
taste
iv. Cerebellum
1. 2nd largest portion of the brain
2. Compares intended movements by the motor areas with what is
actually happening
3. Balance and coordination
4. Ataxia – disruption of muscle coordination
5. Spinal Cord Protection
a. 4 layers – from outside in
i. Wall of the Vertebral Canal (bone)
ii. Meninges – 3 layers of connective tissues that protect the brain and
spinal cord
1. Dura mater, Arachnoid, Pia Mater
iii. Cerebrospinal Fluid
iv. Vertebral Ligaments
b. Meninges
i. Dura Mater – outermost, durable “tough mother” – continuous with
cranial dura mater
1. Epidural Space – located between the dura mater and the
vertebral column – location of where epidruals are administered
for pain relief during childbirth
ii. Arachnoid (middle layer, named because of its delicate spider’s web
arrangement of collagen and elastic fibers) – continuous with cranial
arachnoid
iii. Pia Mater (inner layer, transparent with collagen and elastic fibers,
adheres to the surface of the spinal cord and brain, very delicate) –
continuous with cranial pia mater
1. Subarachnoid Space – between the arachnoid and the pia mater –
where cerebrospinal fluid circulates. Cerebrospinal fluid may be
removed from the subarachnoid space between the 3rd/4th/5th
lumbar vertebrae by a Spinal Tap.
2. Spinal Tap – may be performed to introduce medicine, anesthetics
or to remove fluid which would relieve pressure in the spinal cord
6. 12 Cranial Nerves
Name
Olfactory
Optic
Occulomotor
Trochlear
Trigeminal
Vestibulococchlear
Glossopharyngeal
Abducens
Facial
Vagus
Accessory
Motor, Sensory, Both
Sensory
Sensory
Motor
Motor
Mixed
Sensory
Motor
Motor
Mixed
Mixed
Motor
Hypoglossal
Motor
Function
Smell
Vision
Eye movement
Eye movement
Facial movements
Equilibrium, Hearing
Swallowing
Eye Movement
Facial Expressions
Swallowing and Talking
Movement of head, neck,
back and throat
Tongue Movement
7. Vision
a. Eye Anatomy to Know
i. Cornea, lens, retina (white part of eye), iris (colored part of eye), pupil,
rods, cones, sclera, choroid coat, vitreus humor, aqueous humor
ii. Lacrimal Glands – secrete tears that destroy bacteria
iii. Visual Pathway - Cornea – Lens – Retina – Rods and Cones – Optic
Nerve – Optic Tract - Optic Chiasm – Optic Radiations - Primary Visual
Cortex in the Occipital Lobe
b. Vision Facts
i. Emmetropic Eye – normal vision, normal shape
ii. Myopic Eye – nearsighted, distant objects are blurry
iii. Hypermetropic Eye – farsighted, near objects are blurry
iv. Rods process – black and white (light)
v. Cones process – color
8. The Ear
a. Outer Ear
i. Pinna – Auricle
ii. External Auditory Canal
b. Middle Ear
i. Tympanic Membrane
ii. Eustacian Tube – connects middle ear to the throat
1. Equalizes pressure during yawning or swallowing
iii. 3 bones
1. Malleus (hammer)
2. Incus (anvil)
3. Stapes (stirrup)
c. Inner Ear
i. Cochlea
ii. Vestibulocochlear Nerve
iii. Semicircular Canals – balance
d. Auditory Pathway - Auricle – External Auditory Canal – Tympanic Membrane
– Malleus – Incus – Stapes – Oval Window – Cochlea – Choclear Nerve –
Medula Oblongata – Pons – Midbrain – Thalmus – Temporal Lobe of the
Cerebral Cortex