Download Slide 7.45b

THE NERVOUS SYSTEM
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
 Functions of the Nervous System
 Sensory input – gathering information
 Uses sensory receptors to monitor changes
(stimuli) occurring inside and outside the
body
 Integration
 To process and interpret sensory input and
decide if action is needed
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
SLIDE 7.1A
SLIDE 7.1B
Functions of the Nervous System
 Motor output
 A response to integrated stimuli
 The response activates muscles or glands
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings



“Cell Glue”
Generally assist, segregate, and
insulate neurons
Neuroglia can replicate but cannot
conduct

Overproduction of
Schwann cells
 Nervous Tissue: Neurons
 Neurons = nerve cells
 Cells specialized to transmit messages –
can conduct but cannot replicate
 Have 3 specialized characteristics
 Longevity: with nutrition, can live as long
as you do
 Amitotic: unable to reproduce
themselves (so cannot be replaced)
 High metabolic rate: require continuous
oxygen & glucose (due to lots of activity)
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
SLIDE 7.8

Neuroglia divide. Neurons do not.

Most brain tumors are “gliomas.”

Involve the neuroglia cells, not the neurons.

As neuroglia grow out of control, they press on the neurons
impairing their function

Why is the plasma membrane (neurolemma) of a neuron so
important?

It is the site of electrical signaling –
plays a crucial role in cell to cell
interactions during development as
well
 Major Regions of Neurons
 Cell body
 Contains the metabolic/biosynthetic center
of the cell (location of the nucleus)
 Does not contain centrioles (reflects
amitotic nature) but has the other
organelles
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SLIDE 7.8
 Neuron Anatomy
 Dendrites
 hundreds per cell –
diffusely branched
– close to cell body
 Receptive sites
conduct impulses
toward the cell
body
 Immense surface
area for reception
Figure 7.4a
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
SLIDE 7.10
 Neuron Anatomy
 Axons
 Transmit
impulses away
from cell body
 Vary in length
and diameter
 Larger diameter
= faster
conduction
Figure 7.4a
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
SLIDE 7.10
 Neuron Anatomy
 Axons
 Axon collaterals
– right angle
branches
connecting other
neurons
 Axon terminals
located at end of
axon branches
Figure 7.4a
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
SLIDE 7.10
 Axon terminals
 Contain vesicles with
neurotransmitters –
chemicals which
transmit electrical
impulses
 Axonal terminals are
separated from the next
neuron or effector by
the Synaptic cleft
 Synapse -junction between
nerves
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
SLIDE 7.11
 Myelin Sheath
 Function:
 Protects & insulates
fibers
 Increases speed of
transmission
 Formed by Schwann
Cells (add to notes)
Figure 7.5
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
SLIDE 7.12
 Functional Classification of
Neurons
 Sensory (afferent)
 Nerve fibers that carry information from
sensory receptors to the central nervous
system (CNS)
 Ends of dendrites associated with
specialized receptors – know examples in
your notes!
Figure 7.1
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
 Ends of dendrites are associated with
specialized receptors
 Cutaneous receptors: pressure, pain,
heat, cold
 Proprioceptors: muscles & tendons:
amount of stretch or tension
 Specialized receptors in sense
organs: sight, hearing, smell, taste,
equilibrium
 Functional Classification
 Motor (efferent) division
 Nerve fibers that carry impulses from the
central nervous system to muscles &
glands
Figure 7.1
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
SLIDE 7.3B
 Association or Interneurons
• Responsible for integration & reflex – connect motor & sensory
neurons
• Make up over 99% of neurons
Study for quiz!!!
 Functional Properties of Neurons
Two major functional properties
of neurons resulting in
electrochemical event
Irritability - ability to respond to
stimuli & convert it into a nerve
impulse
Conductivity – ability to transmit an
impulse to other neurons, muscles,
or glands
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
SLIDE 7.17
 Synapse – know the diagram
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
SLIDE 7.11
 Stages of the Chemical Event
 The action potential (electrical signal)
reaches the axon terminals
 Neurotransmitter is released into the synaptic
cleft when the vesicle fuses with the
membrane (presynaptic neuron)
 NT diffuses across the cleft and binds to the
receptors on the dendrite of the next neuron
(postsynaptic neuron)
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
SLIDE 7.21
 Stages of the Chemical Event
 An action potential is started in the next
neuron (or muscle or gland)
 In order to prevent continuous stimulation, NT
is removed from the synapse through:
 Re-uptake
 Enzymatic breakdown
 Synapse Animation
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
SLIDE 7.21
Development Aspects of the
Nervous System
 As you learn:
Axon terminal gets wider so
more NT can be released (more
surface area)
Synaptic cleft get narrower
More NT gets across to
receptors
Faster & more efficient process
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide
Reflex Activity – page 438
 Reflex: rapid predictable motor
response to stimuli that the body is
programmed to do
Unlearned, unpremeditated,
involuntary
 Withdrawal from pain
Learned or acquired reflexes result
from repetition or practice.
 Example: experienced driver drives a car
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
SLIDE 7.58
Reflex Activity
 Two types:
Autonomic: regulate the activity of
smooth muscles, the heart, and
glands
Examples: salivary reflex, pupilary
reflex, digestion, blood pressure
Somatic reflexes: skeletal muscle
reflexes
Example: knee jerk reflex
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
SLIDE 7.58
Know your diagram
 Regeneration
 Mature neurons are incapable of
mitosis. However, PNS axons can
regenerate if cell body is not destroyed.
 The uninjured cell body gets larger in
order to synthesize proteins needed for
regeneration
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
SLIDE
7.14B
 Regeneration
 Axons regenerate at a rate of 1.5 mm/day
 The greater the distance between severed
nerve endings, the less chance of
recovery. Axonal sprouts may grow into
surrounding areas and form a mass called
a neuroma.
 Surgical realignment can help. Retraining
may be necessary once the connection is
completed
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
SLIDE
7.14B

Acoustic
neuroma MRI
 Regeneration
 PNS vs CNS
In PNS axon regeneration,
macrophages clean out the debris
from the injury.
Schwann cells will form a tunnel of
neurolemma to guide severed nerve
ending together. A growth factor is
also released
In CNS – No Schwann cells to do this.SLIDE
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
7.14B
Don’t forget to complete your Quiz review for EC
 Memorize the info on the chart provided - you need to
understand how it all fits together
 Classification of the Nervous System
 Central nervous system (CNS)
 Brain & Spinal cord
 Integrative & control centers
 Peripheral nervous system (PNS)
 Cranial & Spinal Nerves (outside the brain
and spinal cord)
 Communication lines between the CNS and
the rest of the body
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
SLIDE 7.2
 Distribution of Cranial Nerves
Figure 7.21
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
SLIDE 7.59
 Spinal Nerves
Figure 7.22a
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
SLIDE 7.64
 Functional Classification of the
Peripheral Nervous System
 Motor (efferent) division
 Two subdivisions
 Somatic nervous system = voluntary
Conducts impulses to skeletal
muscles
 Autonomic nervous system = involuntary
Conducts impulses to cardiac muscle,
smooth muscle, & glands
Figure 7.1
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
SLIDE 7.3C
 Functional Classification of the
Peripheral Nervous System
 Autonomic nervous system
 Has 2 subdivisions
 Sympathetic division
Fight or flight system
Speeds up HR, respiration rate,
increases cardiac output, deactivates
digestive system
 Parasympathetic division
Resting system
Activates digestive, slows other
systems
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
 Organization of the Nervous
System
Figure 7.2
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
SLIDE 7.4
Protection of the CNS
 Scalp, hair, and skin- Cushions
 Bone: Skull and vertebral column
– Surrounds & Protects
 Meninges – membranes fig 7.16
Figure 7.16a
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Meninges
 Epidural space:
 Found around spine only-contains fat
& CT
 Dura mater – “tough mother”
 Double-layered external covering
fused together except where dural
sinuses are enclosed
 Dural sinuses – venous blood
collected from brain and shunted into
internal jugular vein
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
SLIDE
7.45A
Meninges
 Subdural space
Contains serous fluid
 Arachnoid layer
 Middle layer
 Spider web-like
 Subarachnoid space
 Contains CSF & major arteries &
veins
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
SLIDE
7.45B
Meninges
 Pia mater:
“little mother”
 Internal layer
of delicate CT
 Clings directly
to the surface
of the brain
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
SLIDE
7.45B
Blood Brain Barrier
 Function: ensures
stable environment by
endothelial tight
junctions(the least
permeable capillaries
of the body)
 Excludes many
potentially harmful
substances and
metabolic waste
products
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
SLIDE 7.48
Blood Brain Barrier
 Useless against some substances
 Fats and fat soluble molecules
 Respiratory gases
 Alcohol
 Nicotine
 Anesthesia
 Medical Implication (add to notes):
Hard to get antibiotics through BBB
so hard to treat brain infections
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
SLIDE 7.48
Blood Brain Barrier
 Not identical in all regions
In the hypothalamus region, the
BBB is almost non-existent so
chemical composition of blood
can be monitored
 Different in newborns vs. adult
 Kernicterus: description on next
page
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
SLIDE 7.48
 Hemoglobin is released into blood as RBC’s
recycle
 Hemoglobin breaks down into bilirubin which is
normally cleared from the body by the liver
 Newborns have an immature liver so bilirubin
will build up and cause jaundice of body and of
brain
 Infant will have diminished reflexes, lethargy,
reduced muscle tone, and a high pitched
abnormal cry as external symptoms.
UV light treatment
helps dissolve
excess bilirubin.
Cerebrospinal Fluid
 Function:
Support, protect, & exchange of
materials
Forms a watery cushion to
protect the brain
Circulates to monitor levels of
CO2, O2 , pH – triggers feedback
mechanism if necessary
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SLIDE 7.46
Cerebrospinal Fluid
 Similar to blood plasma
composition
 Location: subarachnoid space and
4 ventricles in brain and central
canal of SC
 Formed by the choroid plexus
(network of capillaries) in brain
ventricles: seeps from capillaries
into ventricles
 ~800 ml formed daily
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SLIDE 7.46
 Choroid plexus  lateral (1st & 2nd) ventricles 
interventricular foramen  3rd ventricle  cerebral aqueduct
 4th ventricle  subarachnoid space & central canal of SC
Hydrocephalu
s•Define: something blocks
SLIDE 7.47B
circulation/drainage of CSF, fluid
accumulates & puts pressure on brain
•Adult:skull bones are fused, fluid
compresses BV and soft brain tissue –
result is brain damage
•Child:skull bones not fused, head may
enlarge, brain damage still a
possibility
•Treatment: insert a shunt to go around
blockage
Figure 7.17b
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
 Shunt drains excess fluid
from ventricles into
abdominal cavity where
body can reabsorb it.
 Pressure then does not
build up in the brain
Brain Development (CNS)
 CNS develops from the embryonic
neural tube
 The neural tube becomes the brain
and spinal cord
 The opening of the neural tube
becomes the ventricles
 Malformations of neural tube lead to
several defects such as spina bifida
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Major Regions of the Brain
 Cerebral
hemisphere
 Diencephalon
 Brain stem
 Cerebellum
Figure 7.12
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
SLIDE 7.27
Cerebrum
 The
surface is
made of
ridges
(gyri) and
grooves
(sulci)
 Purpose:
triple
surface
area
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 7.13a
SLIDE
7.28B
Lobes of the Cerebrum
 Fissures (deep sulci) divide the
cerebrum into lobes
Longitudinal fissure: separates
2 hemispheres
Transverse fissure: separates
cerebellum
Lateral fissure:on side of brain
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
SURFACE LOBES OF THE CEREBRUM
FRONTAL LOBE
PARIETAL LOBE
OCCIPITAL LOBE
TEMPORAL LOBE
Lobes of the Cerebrum
Figure 7.15a
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
SLIDE
7.29B
The Cerebrum
 Cerebral cortex:
 Gray matter: cell bodies
 1/16” thick, ~40% of brain mass
 Voluntary motion
 Higher order thinking skills
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
SLIDE 7.30
Sensory and Motor Areas of
the Cerebral Cortex
Figure 7.14
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SLIDE 7.31
Layers of the Cerebrum
 White matter
 Fiber tracts
inside the
gray matter
 Example:
corpus
callosum
connects
hemispheres
& allows
them to
communicate
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 7.13a
SLIDE
7.33B
Layers of the Cerebrum
 Basal nuclei – internal islands of
gray matter w/in white matter
 Indirectly helps initiate and
control slow stereotyped muscle
movement
 When impaired, postural
disturbances, muscle tremors
uncontrolled contractions result
Figure 7.13a
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
SLIDE
7.33C
Diencephalon
 Sits on top of the brain stem
 Enclosed by the cerebral
hemispheres
 Made of three parts
 Thalamus
 Hypothalamus
 Epithalamus
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
SLIDE
7.34A
Brain Stem
 Attaches to the spinal cord
 Rigidly programmed
automatic behaviors
necessary for survival
 Parts of the brain stem
 Midbrain
 Pons
 Medulla oblongata - If
damaged severely, death
will result
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
SLIDE
7.38A
Cerebellum
 Two hemispheres with convoluted
surfaces
 Provides involuntary smooth,
coordinated body movements
 Likened to the control system of an
automatic pilot to constantly
monitor and adjust muscle
functioning
 Ataxia
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
SLIDE
7.43A
You need to have a basic description &
understanding of the following disorders –
so read everything but copy down every
blue detail
DEVELOPMENTAL ASPECTS OF THE
NERVOUS SYSTEM
 Cerebral palsy
 Lack of oxygen to developing (in
utero) infant
 May be caused by: mother who
smokes, mother who gets German
measles, problems during labor &
delivery, etc.
Cerebral palsy
symptoms
Alzheimer’s Disease
 Progressive degenerative brain
disease
 Mostly seen in the elderly, but may
begin in middle age(early onset)
 Structural changes in the brain
include abnormal protein deposits
(plaques) and twisted fibers within
neurons
 Victims experience memory loss,
irritability, confusion and ultimately,
hallucinations and death
 Age 50s to 60s
 Degeneration of dopamine releasing neurons in nuclei of brain
stem – cause is unknown
 Tremors, stiff facial expression, slow in movement
 Treatment: L-dopa, deep brain stimulation through implanted
electrodes
 Dominant genetic disorder
 Degeneration of basal nuclei and cerebral cortex
 Strikes during middle age – usually fatal within 15 years
 Wild, jerky motions
 Treated with drugs that block dopamine but no cure
Disorders
 Meningitis
Inflammation of the meninges
Can be bacterial or viral
Bacterial is worse due to the
toxins excreted by bacteria
 Encephalitis
 Brain inflammation
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
SLIDE
7.45B
Traumatic Brain Injuries
 Cerebral edema
 Swelling from the inflammatory
response
 May compress and kill brain tissue
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
SLIDE 7.49
Cerebrovascular Accident
(CVA)
 Commonly called a stroke
 The result of a ruptured blood vessel
or a clot in a BV supplying a region of
the brain
 Ischemia: Tissue death – lack of 02 Brain tissue supplied with oxygen
from that blood source dies
 Loss of some functions or death may
result
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
SLIDE 7.50
 Transient ischemic attacks
 Last from 5-50 minutes
 Symptoms: numbness,
temporary paralysis,
impaired speech
 Not permanent BUT
warning sign of impending
stroke
 Demyelinating disorder – form scleroses (hardened deposits)
 Autoimmune
 Onset 20-40 years of age –more common in women
 Incurable – treatments based on slowing progression
 Hemiplegia
 Paralysis of left or right side of body – due to brain injury/stroke
rather than spinal cord injury
 Approximately 17 inches long and extends from the foramen
magnum to the 1st/2nd lumbar vertebrae.
 It is about the size (diameter) of your thumb for most of its
length
 Meningeal coverings extend to the 4th sacral vertebrae
 Purpose: to obtain a CSF sample for testing
 Location: level of L4 or L5 - since spinal cord ends at L1 or L2 –
this reduces the chance of puncturing the spinal cord
 Patient must remain lying down for 6-12 hours since withdrawal
of fluid decreases internal pressure which may cause an
excruciating headache until body regulates itself.
 Flaccid paralysis – No voluntary muscle motion possible –
muscles will atrophy
 Spastic paralysis – affected muscles stay healthy due to reflex
activity but motions are involuntary and uncontrolled
 Quadriplegic: all four limbs are affected
 Paraplegic: only the legs are affected
 Spina bifida-incomplete formation of vertebrae – folic acid
reduces risk
 Occulta-no external manifestations
 Cystica-saclike cyst protrudes from spine
 Meningocele-cyst contains meninges & CSF
 Myelomeningocele-cyst also contains portions of spinal cord and
nerve roots
 Milder forms of SB
Occulta
Cystica
FETAL SURGERY
Study proves
benefits of spina
bifida surgery
(02/10/11)