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Nervous System
What are the functions of the
nervous system?
1) Detect stimuli
(environment & self)
2) Conduct impulses, integrate,
evaluate impulses (stimuli),
memory
3) Respond (movements,
maintain homeostasis etc.)
http://asymptotia.com/wp-images/2007/08/homer-simpsonwallpaper-brain-1024.jpg
Nervous System
What are the Structural/functional units of the Nervous
System?
• Nerve cells ~ Neurons
• Maintaining cells ~ Glial
cells
Neuron anatomy:
Neuron cell body
Dendrites
Axons
Nervous System
What are the different types of Neurons?
Structural types:
Functional types:
Multipolar
Association ~
Interneurons
Bipolar
Unipolar
Afferent ~ Sensory
neurons
Efferent ~ Motor
neurons
Nervous System
What are the types of glial cells and what tasks do they
accomplish?
Astrocytes:
control substances
entering/leaving CSF
Associated with
blood-brain barrier
which is formed by
endothelial cells of
blood vessels.
Nervous System
What are the types of glial cells and what tasks do they
accomplish?
Ependymal cells:
Line the ventricles
(cavities) of CNS,
create cerebral
spinal fluid and aid
in its circulation.
Nervous System
What are the types of glial cells and what tasks do they
accomplish?
Microglia:
Small specialized
macrophages that
attract to areas of
damage in the CNS
and phagocytize
debris
Nervous System
What are the types of glial cells and what tasks do they
accomplish?
Oligodendrocytes:
Cells in the CNS that
have multiple
extensions that wrap
around multiple
axons forming
myelin sheaths.
Nervous System
What are the types of glial cells and what tasks do they
accomplish?
Schwann cells:
Cells in the PNS that
wrap around single
axons forming
myelin sheaths.
The gaps in between
Schwann cells are
called Nodes of
Ranvier
Nervous System
The Brain: development…
Our central nervous
system has humble
origins early in our
development (by 3rd
wk.)
A plate (neural plate) of
cells develop crests
(neural crests) that rise
and eventually meet and
fuse leaving the hollow
dorsal nerve cord & and
ventricles of our CNS
Nervous System
The Brain: development…
Swellings around 3 continuous
chambers are precursors to
forebrain (prosencephalon),
midbrain (mesencephalon) and
hindbrain (rhombencephalon)
Further differentiation results in
5 brain parts:
Telencephalon
Diencephalon
Mesencephalon
Metencephalon
Myelencephalon
Nervous System
The Brain: development…
Telencephalon
Diencephalon
Mesencephalon
Metencephalon
Myelencephalon
http://classes.edowner.net/Z20H/Week%203/slides/Necturus-brain-ventral-view.html
Nervous System
How is the Nervous System organized?
Brain
Spinal cord
Nerves
Sense organs
Central Nervous
System (CNS)
Peripheral Nervous
System (PNS)
43
(12 cranial & 31 spinal nerves)
Nervous System
The Brain: the big picture…
The basic components of
the CNS include the:
• Cerebrum
• Diencephalon
• Cerebellum
• Brain stem
• Spinal cord
Nervous System
The Brain: from the outside in…
The brain and spinal cord are
protected by meninges
3 layers:
Dura mater ~ outermost,
tough, continuous with
periosteum
Arachn oid mater ~ middle
layer, spider-web appearance
Pia mater ~ innermost layer,
not visible to naked eye
Nervous System
The Brain: from the outside in…
100-160ml of CSF circulates
throughout the ventricles,
down the central canal of the
spinal cord and throughout the
subarachnoid space.
CSF is reabsorbed back into
blood primarily at the venous
sinuses found within the dura
mater.
Nervous System
The Brain: from the outside in…
Ventricles are comprised of 4 major
cavities:
1&2 ~ Right and Left Lateral
ventricles
3rd ventricle space within thalamus
4th ventricle between cerebellum
and brainstem
channel connecting 3rd and 4th
cerebral (mesencephalon)
aqueduct and if blocked can result
in hydrocephaly
Nervous System
The Brainstem: Medulla oblongata
Most inferior portion, functions
as a conduction pathway
(descending motor neuron
pathways decussate here)
Contralateral/Ipsilateral
Reflex centers for:
regulating heart rate
blood vessel diameter
coughing, sneezing
breathing
swallowing
Nervous System
The Brainstem: Pons
Superior to Medulla
oblongata.
Contains more ascending
and descending pathways.
Relays information from
cerebrum to cerebellum.
Also includes sleep and
respiratory centers.
Nervous System
The Brainstem: Midbrain
Small section superior to
the pons.
Part of the auditory
pathways and visual
reflexes
Also involved in regulating
muscle tone/activity and
coordination
Nervous System
The Diencephalon: Thalamus
“Gateway to cerebral cortex”
Most sensory stimuli project
to the thalamus, which in turn
projects to the cerebrum.
Thalamus also influences
moods and activities
associated with strong
emotion.
(Two concepts: Sensory
integration and Mood)
Nervous System
The Diencephalon: Hypothalamus
Major control center of
autonomic nervous system
and endocrine system.
Centers associated with:
* Food/H2O intake
* Thermoregulation
* Cardiovascular regulation
* Hormone secretion
* Sleep/waking
* Emotional behavior
Nervous System
The Brain: Cerebrum (bumps and grooves)
The sulcus dividing
frontal and parietal lobes
is Central Sulcus.
Ridges on either side are
Pre & Post gyri
Motor
Pre CS ~ motor cortex
Post CS ~ somatic
sensory cortex
Sensory
Nervous System
The Brain: Cerebellum
Responsible for balance,
muscle tone and
coordination
Fine motor coordination
due to comparator
function… compares
intended movements with
actual movements
Can also “learn” complex
movements
Nervous System
Does the brain have any peripheral nerves?
Nervous System
Does the brain have any peripheral nerves?
Nervous System
Does the brain have any peripheral nerves?
Nervous System
Does the brain have any peripheral nerves?
Nervous System
Does the brain have any peripheral nerves?
Nervous System
Does the brain have any peripheral nerves?
Nervous System
Does the brain have any peripheral nerves?
Nervous System
Does the brain have any peripheral nerves?
Nervous System
Does the brain have any peripheral nerves?
Nervous System
Does the brain have any peripheral nerves?
Nervous System
Does the brain have any peripheral nerves?
Nervous System
Does the brain have any peripheral nerves?
Nervous System
Why is the tongue innervated the way it is?
Depends on
ontogenetic
&
phylogenetic history
Anterior = 1st arch = V
Taste buds = 1st 2nd arch = VII
(for fish)
Posterior buds = 3rd arch = IX
Muscles are myotomal = XII
Nervous System
What is the anatomy of the spinal cord?
Spinal cord is link between brain
and PNS
Spinal cord ends ~ L2 vertebra but
trailing nerves form Cauda equina
Enlargements for regions
innervating limbs (Cervical and
Lumbar)
Regions of convergence/divergence
called plexuses
Nervous System
How are the layers of the meninges arranged?
The dura mater
extends down the
vertebral foramen.
There is a subdural
space that is largely
a “potential space”
The arachnoid and
pia maters are
arranged similarly
as in the cranium.
Nervous System
How does spinal cord form denote function?
Spinal cord
contains white
and gray matter
gangli
(Remember the
significance of each?)
Spinal cord w/ distinct anterior and posterior formations,
including “horns” of gray matter.
Posterior horn contains neuron cell bodies that synapse
with afferent neurons.
Anterior horn contains neuron cell bodies that send
efferent axon
Lateral horns ~ autonomic neuron cell bodies
Nervous System
What are the various spinal reflexes and how do they work?
Crossed
extensor
(withdrawal 3)
reflex:
1)
2)
3)
Nervous System
What is the association between cutaneous sensation and spinal
nerves?
Spinal nerves innervate
specific regions of the body
and are mapped out on a
Dermatomal map
Predict the possible site of
nerve damage for a patient
who suffered whiplash and
developed anesthesia in
the left arm, forearm and
hand!