Nervous System and Sensory Organs
Biology 171 – Lab 12
Lab Activities
•
•
•
•
Fetal Pig – Spinal Cord
Sheep Brain Dissection
Cow Eye Dissection
Review for Final
• Central Nervous System
(CNS) = Brain and
Spinal Cord
• Peripheral Nervous
System (PNS) = Nerves
Function:
1) Receive sensory input
2) Perform integration
3) Generate motor
outputs
Neurons
Parts:
• Cell body
▫ Contains nucleus and
organelles
• Dendrites
▫ Receive signal,
transmit to cell body
• Axon
▫ Sends signal to other
cells
▫ Insulated by myelin
sheath
Neurons
Types:
• Interneuron
▫ Entirely within CNS
▫ Conduct nerve impulses
between parts of the CNS
• Sensory Neuron
▫ Take nerve impulses from
the sensory receptors to the
CNS.
• Motor neuron
▫ Takes nerve impulses from
CNS to muscles or glands.
▫ Cause muscles/glands to
contract/secrete
The Spinal Cord
• Gray matter (b)
▫ Cell bodies, unmyelinated
fibers
▫ Sensory neurons, motor
neurons, short interneurons
that connect MN and SN
• White matter (c)
▫ Long myelinated fibers of
interneurons, form tracts
▫ Tracts connect the spinal cord
to the brain
▫ Superhighway
The Spinal Cord
• Bundle of nervous tissue
surrounded by vertebral
column
• Main functions:
1) Center for reflex actions
2) Communication between
brain and spinal nerves
Surrounded by vertebrae and
meninges
• Cerebrospinal fluid in central
canal of spinal cord (a)
Reflexes
Sensory receptor  Sensory neurons 
interneurons (spinal cord)  Motor neurons
Reflexes
• Reflex = involuntary and
predictable response to a
stimulus
• Sensory receptor 
Sensory neurons 
interneurons (spinal
cord)  motor neurons
• Consciousness of
stimulus lags behind
response because
information has not
reached the brain by the
time the reaction occurs.
Brain
• Four ventricles: produce cerebrospinal fluid
▫ two lateral in cerebrum
▫ third ventricle in diencephalon (center of brain)
▫ fourth ventricle between cerebrum and pons
Cerebrum
Cerebrum
• Right/left hemispheres
• Longitudinal fissure
• Connected via corpus
callosum
• Cerebral Cortex
• Grooves called sulci;
divide into lobes.
Lobes
• Frontal
▫ Primary motor
▫ Motor speech
Lobes
• Parietal
▫ Primary
somatosensory area
▫ Primary taste area
Lobes
• Occipital
▫ Primary visual area
▫ Visual association
Lobes
• Temporal
▫ Primary auditory
▫ Auditory association
Cerebellum
• Motor coordination
• Tree-like pattern of
white and dark
matter
Brainstem
• Midbrain
 Relay station for
tracts between the
cerebrum and the
spinal cord or
cerebellum
• Pons
 Reflex center
• Medulla
 Reflex center
Diencephalon
• Thalamus
▫ Sides and roof of 3rd
ventricle
▫ Receives sensor input,
integrates info, sends
to cerebrum
▫ “Gatekeeper”
• Hypothalamus
▫ Forms floor of 3rd
ventricle
▫ Integrating center,
regulates homeostasis
Corpus Callosum
Diencephalon
• Pineal Gland
▫ Secretes melatonin
• Pituitary Gland
▫ Secretes hormones
▫ Regulated by
hypothalamus
Comparison of Vertebrate Brains
Comparison of Vertebrate Brains
Sense Organs
Eyes, Ears, Skin
Eye Function
• Photoreceptors: sensory receptors sensitive to
light
• Generate nerve impulses, pass to brain via optic
nerve
Types of Eyes
• Eyespots
▫ Do not form
images; allow for
animal to detect the
direction of light.
▫ Example:
planarians
Types of Eyes
• Compound Eyes
▫ Composed of individual units called ommatidia
▫ Insects, spiders.
Camera-Type Eyes
• Vertebrates and some
molluscs (squid and
octopus)
• Convergent Evolution
▫ Trait evolves separately
on different lineages.
• Single lens focuses an
image onto closely packed
photoreceptors (like film)
Parts of the Human Eye
Three layers:
Parts of the Human Eye
Sclera – fibrous white outer layer,
Choroid – middle layer, brown
pigments, absorbs stray light rays.
Retina – innermost layer,
photoreceptors
Retina
Choroid
Sclera
Sclera
Sclera – fibrous white outer
layer, transparent front is called
the cornea, the “window to the
eye”.
Conjunctiva – thin layer of
epithelial cells forms a mucus
membrane, keeps eye moist.
Covers surface of sclera.
Cornea
Sclera
Conjunctivitis – Pink Eye
• Causes:
▫
▫
▫
▫
Viruses (most commonly)
Allergies
Bacteria
Chemicals
• Typically resolves in 3-5 days.
• Prevention: don’t touch eyes!
Choroid
Iris
Choroid–contains blood vessels
and brown pigment to absorb
stray light rays.
Toward the front of the eye,
thickens and becomes:
Ciliary body – ring-shaped
Iris – muscular diaphragm,
regulates size of the opening of
the eye.
Pupil – opening controlled by
iris.
Lens – attached to ciliary body
by ligaments
Ciliary body
Choroid
Lens, Compartments, and Fluids
Lens – attached to ciliary body
by ligaments. Refracts and
focuses light rays. Divides the eye
into two compartments.
Anterior Compartment:
between cornea and lens. Filled
with aqueous humor, which
provides cushion and
nutrient/waste transport.
Posterior Compartment:
behind lens. Filled with
vitreous humor, which
maintains shape of eye.
Anterior Compartment
Lens
Posterior Compartment
Retina
???
Optic Nerve
Retina – Contains
photoreceptors.
Rod cells – sensitive to light,
but do not sense color.
Cone cells – Require bright
light, sensitive to different
wavelengths of light (color).
Fovea centralis – region of
retina where cone cells are
densely packed.
Sensory fibers form the optic
nerve, which takes nerve
impulses to the brain.
Fovea Centralis
Retina
Focusing the Eye – Visual Accommodation
Abnormalities
Nearsighted = can see near
Farsighted = can see far
Astigmatism = uneven cornea.
Brain Dissection – After cutting
• Find/Identify:
▫ Two lateral ventricles
▫ 3rd and 4th ventricles
▫ Thalamus and
Hypothalamus
▫ Midbrain, pons, medulla
oblongata
▫ Corpus callosum
▫ Cerebrum
▫ Cerebellum – tree pattern
Lab Activities
• Fetal Pig – Spinal Cord
▫ Follow p 116- 119
• Sheep Brain Dissection
▫ Follow p 120 - 124
• Cow Eye Dissection
▫ Follow handout
• Exam Review
Structures to Locate
Spinal Cord (p 116- 119)
Brain (p 120 – 124)
•
•
•
•
•Cerebrum
▫ Frontal, Parietal, Temporal,
Occipital lobes
•Sulci
•Longitudinal Fissure
•Lateral Ventricles (2)
•3rd and 4th Ventricles
•Midbrain
•Pons
•Medulla Oblongata
•Corpus callosum
•Cerebellum
Vertebrae
Meninges
White matter
Grey matter
Cow Eye Dissection
Instructions
Structures to Find
• www.exploratorium.edu/lear
ning_studio/cow_eye/cowe
ye.pdf‎
• Cut around Sclera
• Cornea in front half
•
•
•
•
•
•
•
•
•
•
•
Sclera
Cornea
Pupil
Choroid
Ciliary body
Iris
Retina
Lens
Aqueous humour
Vitreous humour
Optic Nerve
Course Evaluations
•
•
•
•
ONLINE this year!!
https://csi.mce.im/
Use CIX login and password
MUST DO BEFORE DEC 15 11:59 PM