Why is is it important for organisms to
respond to their external
environment?
Why is it important for organisms to
respond to their external
environment?
The environment provides many
different stimuli. Organisms respond in
a manner that enables them to
maintain homeostasis.
Regulation (life process) is maintained
by the:
Nervous and Endocrine Systems
Hypothesize which system works the
quickest in response to stimuli.
Regulation (life process) is maintained
by the:
Nervous and Endocrine Systems
Hypothesize which system works the
quickest in response to stimuli.
nervous system- electrochemical
impulses.
endocrine system- hormone release
Functional Cell in the Nervous System
is the
NEURON.
Neurons send Electrochemical Signals
Nervous Tissue Organization
Signal Transmission
is
Electrochemical Impulse.
Chemical in the Electrochemical
…but what’s going on in the axon?
Electrical in the Electrochemical
Resting Potential of a Neuron
Oscilloscope Reading
Action potential is an All-or-Nothing
event once the nerve has been
stimulated past the threshold.
So……How do you explain the
differences in the following pains…
Weak pains? Strong pains? Intense pains?
Its simple……stimulation of more or
less neurons.
Nervous System Organization
Organisms evolved from simple to
complex.
Nervous systems went from being
decentralized to centralized.
Decentralized
Nervous System
Cephalization is accompanied by a
concentration of nervous tissue
(cephalic ganglion or brain) and
feeding mechanisms in the head
region that serves to integrate the
activities of the nervous system.
Phylum: Cnidaria
•Nervous system
•cephalization- not much
•nerve cells scattered around mouth
•no organization or brain
•nerve net cells and sensory cells
•sensitive to chemicals & touch
•coordinate muscle fiber action
•hormone glutathione produces feeding response
Why is a nerve net an inefficient
design for more complex organisms?
Centralized
Nervous System
Why is a nerve net an inefficient
design for more complex organisms?
The entire organism is responding to
stimuli. This is a waste of energy.
Considering the structure of the
Planaria (Platyhelminthes), how would
you describe its nervous tissue
organization?
Phylum: Platyhelminthes
Class: Turbellaria
•well-defined nervous system w/ sense
organs
•ganglia concentrated as simple brain at
head
•sensory cells (statocysts sense gravity,
light sensory cells at eyespots,
chemosensory cells)
•2 nerve cords run length of body
Platyhelminthes are believed to be the
first hunters- organisms that use their
senses to acquire food.
Considering the structure of the
Roundworms (Nematoda), how would
you describe its nervous tissue
organization?
Kingdom: Animalia
Phylum: Nematoda (formerly Aschelminthes)
cross-section
Kingdom: Animalia
Phylum: Nematoda (formerly Aschelminthes)
•nervous system
•sensory structures and ganglia at
head
•nerve ring with ganglia around the
pharynx
•ventral and dorsal nerve cords
Considering the structure of the
Mollusks, how would you describe its
nervous tissue organization?
Heart. Most molluscs have an open circulatory
system. The dorsally located heart pumps
circulatory fluid called hemolymph through arteries
into sinuses (body spaces). The organs of the
mollusc are thus continually bathed in hemolymph.
Nephridium. Excretory organs
called nephridia remove metabolic
wastes from the hemolymph.
The long digestive tract is
coiled in the visceral mass.
Visceral mass
Coelom
Intestine
Gonads
Mantle
Stomach
Mantle
cavity
Shell
Radula
Anus
The nervous
system consists
of a nerve ring
around the
esophagus, from
which nerve
cords extend.
Figure 33.16
Gill
Foot
Nerve
cords
Esophagus
Mouth
Mouth
Radula. The mouth
region in many
mollusc species
contains a rasp-like
feeding organ
called a radula. This
belt of backwardcurved teeth slides
back and forth,
scraping and
scooping like a
backhoe.
Octopus Anatomy
The mantle cavity of a bivalve
Hinge area
Mantle
Coelom
Gut
Heart
Shell
Adductor
muscle
Mouth
Anus
Excurrent
siphon
Palp
Water
flow
Foot
Mantle
cavity
Gill
Incurrent
siphon
Considering the structure of the
Earthworm (Annelid) and the
Grasshopper (Arthropod), how would
you describe its nervous tissue
organization?
Anatomy of the earthworm
Grasshopper Anatomy
Both organisms have cerebral ganglion
that enable them to process
information and respond.
Chordates: Most evolved phyla in the
Animal Kingdom
IncludesFish, Amphibians, Reptiles, Birds, Mammals
Characteristics of Chordates
• Notochord
•an internal skeletal rod that provides support
•lies ventral to the neural tube
• Hollow nerve cord that lies dorsal to the notochord
• Pharyngeal pouches
• Disappear during development in mammals
• linings give rise to many glands in the lymphatic
system: thymus, tonsils, carotid bones,
parathyroid
glands
• Postanal Tail (at some stage of development)
Human Nervous System
Human Nervous System
• Central Nervous System
• Peripheral Nervous
System
Central Nervous System
• Brain
– Sensory information is
received and motor
control is initiated
– Parts of the Brain:
• Brain stem- medulla,
pons, and midbrain
• Diencephalon
• Cerebellum
• Cerebrum
• Spinal Cord
– Sensory information is
received and motor
control is initiated
– Parts of the spinal cord:
• White matter- Myelinated
fibers
• Gray matter- cell bodies
and unmyelinated fibers
The Human Brain
The Brain Stem
• Medulla Oblongota
– Controls many involuntary actions (breathing, heart
rate, organ function, etc.)
• Pons
– Functions in regulating breathing
– Reflex centers for head movements in response to
auditory and visual stimuli
• Midbrain
– Reflex centers for visual, auditory, and tactile
responses
Diencephalon
• Hypothalamus
– Maintains homeostasis and contains centers for
regulating hunger, sleep, thirst, body temp, water
balance and blood pressure
– Contains the pituitary gland (master gland for the
endocrine system)
• Thalamus
– Serves as a relay information for sensory information
– Involved in arousal and higher mental functions
(emotion, memory, etc.)
Cerebellum
• Muscle coordination
– Integrates impulses received from higher centers
to ensure that all of the skeletal muscles work
together to smooth and graceful motions
– Maintains normal muscle tone and maintains
posture
– Coordinates with the inner ear to maintain
balance and body position
Cerebrum
• Largest part of the brain in humans
• Receives sensory input for voluntary
movements
• Higher thought processes (learning, memory,
speech, etc.)
Cerebral Hemispheres
• Frontal lobe: motor,
speech, language
• Temporal lobe:
Auditory
• Parietal lobe:
Somatosensory
processing, taste
• Occipital: Visual
Brain and Spinal Cord
are protected by membranes.
Meninges
Peripheral Nervous System
• Somatic
– Reflexes of the body in
response to sensory
stimuli
• Regulated by the spinal
cord and cranial nerves
– Voluntary Movements
• Regulated by the brain
• Autonomic
– Involuntary actions
• Regulated by the brain
The Reflex Arc involves the action of
the following types of neurons:
How would you build the Reflex Arc?
Autonomic Nervous System
• Sympathetic
• Parasympathetic
These two systems are antagonistic of each other. This
property enables control of involuntary actions
necessary for life functions.
Here is a specific example…..
Heart Rate Regulation