Transcript 07 Cranial nerves, their functional division into three groups. Organ

I-XII pairs of cranial nerves,
their functional division into three
groups. Organ of vision. Coats of
the eyeball and refractile
environment.
The Brain
• 3 primary divisions:
– Forebrain
• cortex (folded stuff)
• limbic system, etc (stuff around brain stem)
– Midbrain (top of brainstem)
– Hindbrain (bottom of brainstem + cerebellum)
Organ of vision. Coats of the eyeball and refractile environment.
Hindbrain
Medulla
Pons
Cerebellum
Pons
Medulla
Cerebellum
http://wwwunix.oit.umass.edu/~psyc335c/lectures/hindbrain.gif
Medulla:
Controls vital reflexes: breathing,
heart rate, vomiting, salivation,
coughing, sneezing
- Via cranial nerves
Damage to medulla can be fatal
Large doses of opiates can be fatal
b/c suppress activity of
medulla…why…?...b/c receptors
there!
Pons:
Also has cranial nerves
Location of axon decussation
(where axons cross from one side
of the brain to the other…so left
brain controls right body and vice
versa)
Reticular formation: motor control,
arousal, consciousness
Midbrain:
Cerebral aqueduct
More cranial nerves
Superior colliculus (visual info)
Inferior colliculus (auditory info)
Substantia nigra: dopamineproducing cells, structure that is lost
in Parkinson’s Disease
http://en.wikipedia.org/wiki/Midbrain
Brainstem
Medulla
Pons
Midbrain
Some
forebrain
structures
Senses: Information comes in the cranial nerves and eventually ends up in the cortex
Cranial Nerves
Table 4.4, page 87
Olfactory nerve:
Smell
http://www.besthealth.com/besthealth/bodyguide/reftext/images/
cranial_nerves.jpg
Cranial Nerves
Table 4.4, page 87
Optic nerve:
Vision
http://www.besthealth.com/besthealth/bodyguide/reftext/images/
cranial_nerves.jpg
Cranial Nerves
Table 4.4, page 87
Occulomotor
nerve:
Eye movement,
pupil constriction
http://www.besthealth.com/besthealth/bodyguide/reftext/images/
cranial_nerves.jpg
Cranial Nerves
Table 4.4, page 87
Trochlear nerve:
Eye movement
http://www.besthealth.com/besthealth/bodyguide/reftext/images/
cranial_nerves.jpg
Cranial Nerves
Table 4.4, page 87
Trigeminal nerve:
Skin senses from
face
Jaw muscles for
chewing and
swallowing
(muscles of
mastication)
http://www.besthealth.com/besthealth/bodyguide/reftext/images/
cranial_nerves.jpg
Cranial Nerves
Table 4.4, page 87
Abducens nerve:
Eye movements
http://www.besthealth.com/besthealth/bodyguide/reftext/images/
cranial_nerves.jpg
Cranial Nerves
Table 4.4, page 87
Facial nerve:
Taste
Facial
expressions
Crying
Salivation
Dilation of head’s
blood vessels
http://www.besthealth.com/besthealth/bodyguide/reftext/images/
cranial_nerves.jpg
Cranial Nerves
Table 4.4, page 87
Acoustic nerve:
Aka
vestibulocochlear
or statoacoustic
Hearing
Equilibrium
http://www.besthealth.com/besthealth/bodyguide/reftext/images/
cranial_nerves.jpg
Cranial Nerves
Table 4.4, page 87
Glossopharynge
al nerve:
Taste
Swallowing
Salivation
Throat
movements
during speech
http://www.besthealth.com/besthealth/bodyguide/reftext/images/
cranial_nerves.jpg
Cranial Nerves
Table 4.4, page 87
Vagus nerve:
Sensation from
neck and thorax
Control of throat,
esophagus,
larynx
Parasympathetic
nerves to
stomach,
intestines, etc
http://www.besthealth.com/besthealth/bodyguide/reftext/images/
cranial_nerves.jpg
Cranial Nerves
Table 4.4, page 87
Spinal accessory
nerve:
Aka Accessory
nerve
Neck and
shoulder
movements
http://www.besthealth.com/besthealth/bodyguide/reftext/images/
cranial_nerves.jpg
Cranial Nerves
Table 4.4, page 87
Hypoglossal
nerve:
Muscles of
tongue
http://www.besthealth.com/besthealth/bodyguide/reftext/images/
cranial_nerves.jpg
Forebrain
•
•
•
•
•
•
•
Thalamus
Hypothalamus
Pituitary gland
Basal ganglia
Basal forebrain
Hippocampus
Limbic system
Thalamus:
Relay station for all sensory info on its way to brain (except
olfactory info)
Many specialized nuclei (ex: LGN, MGN…don’t have to know
these!)
Hypothalamus
Communicates with pituitary gland to alter hormone release
Involved in feeding, drinking, temperature regulation, sexual
behavior, fighting, arousal (activity level)…4 Fs
Pituitary gland
Endocrine gland (hormone producing)
Attached to base of hypothalamus by stalk
Makes and releases hormones into bloodstream
Basal Ganglia
Motor control, but also
memory and emotional
expression
Lose dopamine neurons in
SN  Parkinson’s Disease
http://www.uni.edu/walsh/basalganglia-2.jpg
thalamus.wustl.edu/ course/cbell6.gif
Lose dopamine neurons in
caudate & putamen 
Huntington’s chorea
Don’t memorize image!!! Just
understand that this is a very
complex system!
Basal forebrain
Anterior and dorsal to
hypothalamus
Important for arousal,
wakefulness, attention
http://memorylossonline.com/summer2003/glo
ssary/basalforebrain.jpg
Lose cells in nucleus
basalis  decreased
attention & intellect (AD,
PD)
Hippocampus
Memory formation
HM: temporal lobes
removed for intractable
epilepsy  no longer
formed new memories
http://www.hermespress.com/Perennial_Tradition/hippocampus.gif
http://www.umassmed.edu/bnri/graphics/crusiofig1.gif
Limbic System
important for motivated & emotional behaviors (eating,
drinking, sexual activity, aggressive behavior)
Ventricles
Contain
cerebrospinal fluid
(CSF)
CSF reabsorbed
into blood vessels,
so continuous
turnover
Protective
Reservoir for
hormones, nutrients
http://mywebpages.comcast.net/epollak/PSY255_pix/ventricles.PNG
Ventricle size can indicate
problems
• Enlarged ventricles
as in Alzheimer’s
patients (cell loss).
• Lack of ventricles
due to tumors etc.
Cortex
• 2 hemispheres
– Communicate via
corpus callosum &
anterior commisure
• 4 lobes
http://pegasus.cc.ucf.edu/~Brainmd1/brmodelc.gif
http://www.urmc.rochester.edu/neuroslides/slides/slide201.jpg
http://trc.ucdavis.edu/mjguinan/apc100/modules/Nervous/grosscns/images/brain10.jpg
6 laminae (layers of cells)
The lobes of the cortex
• Frontal
– Thinking
– Prefrontal cortex
• Planning
• Working memory
• Socially
appropriate
behavior
• Delayed-response
task
• Lobotomies
– Primary motor
cortex
• Broca’s aphasia
The lobes of the cortex
• Parietal
– Sensing
• Primary sensory
cortex
Homunculus
The lobes of the cortex
• Temporal
– Spoken language
comprehension
• Wernike’s aphasia
– Hearing
– Vision
• Movement
perception
• Face recognition
– Emotional
motivational
behavior
The lobes of the cortex
• Occipital
– Vision
• Primary visual
cortex
• Damage
causes
“cortical
blindness”
Functions
• Forebrain
– the cool stuff (thinking, perceiving, big part of emotion)
• Midbrain
– sensory pathways
• Hindbrain
– motor control, reflexes (breathing, heart rate, etc)
Sensory Organs
Sensory Function and Vision…
The General Senses…
• Sensory receptors
– specialized cells that monitor the environment
and relay information to the CNS.
– Free nerve endings are the simplest type:
they are the dendrites of sensory neurons
– Complex receptors (eyes) are housed in
organs
– Some receptors respond to only one kind of
stimulus
All sensory receptors send info to
the CNS via an action potential…
• At the CNS, info is routed according to the
stimulus and its location
• The stronger the stimulus, the higher the
frequency of action potentials
• Some receptors adapt, that is their
sensitivity to a stimulus is reduced if the
stimulus is continually applied (smell)
– The RAS can heighten or reduce awareness
of sensory information
General versus special senses…
• General sense receptors
included those for
temperature, pain,
pressure, touch, vibration
& proprioception (body
position)
• These receptors are very
simple in nature
“Special” senses
• Special senses
monitor vision,
hearing, olfaction,
gustation, and
equilibrium through
specialized sense
organs
• These sense organs
are highly specialized
Tactile receptors…
• May be simple or complex,
superficial or deep, fine
(provide detailed information)
or crude (provide little
information)
• Merkel’s – fine touch and
pressure
• Pacinian – deep pressure
• Meissner’s – fine touch
and pressure in select
areas
• Ruffini – pressure or
distortion in deep dermal
layers
The olfactory organs…
Gustation….taste
• http://www.bbc.co.uk/science/humanbody/body/f
actfiles/taste/taste_ani_f5.swf
• Taste buds are organs containing gustatory &
supporting cells that lie within papillae
• Chemicals contact taste hairs which change the
MP of taste cells & leads to an AP in the sensory
neuron
• 4 primary taste sensations – sweet, salt, sour,
bitter
• Sensory Pathway: sensory receptors>medulla>
thalamus>primary sensory cortex
A complex sensory organ: the eye.
• is surrounded by accessory structures that
act to protect, lubricate, and support it
• is a light, compact, durable, and highly
specialized hollow organ that weighs
about 8 oz and measures 1 inch in
diameter.
• is divided into anterior (aqueous) &
posterior (vitreous) cavities.
• its walls are made of 3 “tunics”
Accessory structures of the eye…
•
•
•
•
•
•
eyelids (palpebrae)
eyelashes & brows
exocrine glands
lacrimal apparatus
Conjunctiva
6 extrinsic occulomotor
muscles:
– the inferior, superior, lateral
and medial rectus muscles
– the superior and inferior
oblique muscles
Eye anatomy…..
• http://www.macula.org
/anatomy/eyeframe.ht
ml
• The hollow eye is divided
into 2 cavities:
• An anterior cavity which
contains aqueous humor
• A posterior cavity which
holds vitreous humor
• Humors act to stabilize
eye shape and provide
nutrients
The Tunics of the eye…
• Fibrous - the sclera &
anterior cornea
• Vascular – contains
blood vessels,
lymphatics, choroid &
intrinsic muscles of the
iris &ciliary bodies (they
support the lens)
• Neural – the retina, it
contains the rods and
cones (photoreceptor
cells), bipolar &ganglion
cells
Retinal organization …
• The retina is made of several cell layers:
– Photoreceptor cells – rods lie along the
periphery & cones lie at the back of the retina
– Bipolar cells synapse with the rods and cones
– Ganglion cells synapse with the bipolar cells
– The axons of the ganglion cells form the optic
nerve
– http://www.macula.org/anatomy/retinaframe.html
http://www.macula.org/anatomy/anatomy.html
• Macula lutea – area on
the retina where the
visual image forms, it
contains only cones with
the greatest numbers at
the fovea centralis
• Optic Disc or “blind spot”
is the area where the
ganglion cell axons exit
the eye to form the optic
nerve