Transcript Nervous System

Nervous
System
Chapter 9
Functions
•
•
•
•
Stimulate all movement
Receive sensory input
Store and integrate information
Maintain homeostasis
Organization
• Two main divisions:
1. Central Nervous System
(CNS)
a. Brain and spinal cord
b. Command and sensory
integration center.
2. Peripheral Nervous System
(PNS)
a. All nerves that communicate
with spinal cord and cranial
region.
Nice concept
map to review
with! 
Nervous System Cells
Neurons:
carries the nerve impulses, mitosis not
possible after reaching maturity
Neuroglial cells:
supports neurons, does not carry
impulses, mitosis is possible
throughout lifespan
Neuron cell body
Neuroglial cell nucleus
Neuroglial Cells
• Most abundant in CNS
• 5 Major Types:
1. Microglial – phagocytes, protection
2. Oligodendrocytes – forms myelin in CNS
3. Astrocytes – provide support & connection
between neurons and blood supply
4. Ependymal cells – lines cavities (Ventricles)
of brain & spinal cord, helps form CSF, ciliated
5. Schwann cells – forms myelin in PNS
Can you find two neurons in this picture? What
division of the NS is being shown here? What
neuroglial cell is not shown here and why not?
Neurons
• Large in size
• Very high metabolic rate
• Amitotic (no replacing after
destruction), no centrioles
• Extreme longevity…over 100
yrs. possible
• Cell structures:
- cell body, axon, dendrites, myelin
sheath, nodes of Ranvier, nucleus,
axon terminals, end bulbs, synapse
(If myelinated, will have Schwann cells or
Oligodendrocytes attached to axon)
Basic Neuron Anatomy
Impulses move
along a one-way
path!
Dendrites
Cell body
Axon
Neurons Structural Differences
1. Bipolar – rare, found
in retina of eye
2. Unipolar – afferent
(sensory) PNS
3. Multipolar – majority
of all neurons; most in
brain are multipolar.
Neuron Organization
Neuron types: Sensory,
Interneurons, Motor
Neuron Functional Differences
Integrates and coordinates
info from afferent, sends out
response to efferent
Neuron Pathway Types
**Be able to describe the difference between the pathways.
Nerve Impulse
Conduction
Neuron at Resting Potential
Leaky membrane allows Na+ and
K+ ions to diffuse, so Na/K pump is
always working.
• Membrane is
polarized (charged!)
• -70mv inside cell
• Inside more negative
than outside.
• What keeps it neg?
Large, negative
proteins, chloride
ions, and nucleic
acids inside.
Moving Action
Potential
Action potentials are pulselike waves of voltage.
Diffusion and
electrochemical attraction
move ions in/out
Myelinated axons increase
speed of action potential.
Animation
Animation 2
Moving Impulse Along Neuron
a. Resting potential = -70mv
b. Depolarization – reversal of
charges
1. Na+ gates open and enters cell
2. Potential changes to = +35mv
c. Repolarization – reversal of
charges to restore resting pot.
1. Na+ gates shut
2. K+ gates open and leaves cell
d. Hyperpolarization –
1. Too much K+ moved out than
was necessary
e. Refractory period – Fixing
overcorrection with active
transport. Cannot respond to
another stimulus.
1. Na/K+ pumps move Na+ out and
K+ into cell to re-establish
polarity
Animation
Animation 2
Animation 3
Synapse
• Neurotransmitters:
communication
chemicals (50+ types
known!)
• Threshold – minimum
amount of stimulus
needed for
depolarization.
• Reuptake
transporters recycle
neurotransmitters.
Animation
Neuron Communication Video
Neurotransmitters
• Excitatory – Increases activity of
postsynaptic neuron.
• Inhibitory – Decreases activity of
postsynaptic neuron.
More than one type of neurotransmitter can
be released by a single neuron and one neuron
can have synapses with several different
neurons (convergence and divergence), thus, a
single neuron can have receptors for many
different types of neurotransmitters.
Common Neurotransmitters
• Acetylcholine – Excitatory, skeletal muscle
contraction
• Norepinephrine – Excitatory; increase HR.
• GABA – Inhibitory, reduces anxiety.
• Glutamate – Excitatory, involved in learning
and memory.
• Endorphins – Inhibitory, natural opiates.
• Serotonin – Involved in regulating attention,
emotions, mood disorders
• Dopamine – Contributes in voluntary
movement; feel good emotions, Parkinson’s
Drug Effects on
Neurotransmitters
• Pain killers – stop the release or block
receptor sites or increase threshold.
• Caffeine – lowers threshold at synapses
so neurons are more easily excited.
• Zoloft/Prozac/Paxil– keeps serotonin in
the synapse longer; anti-depressants
• Dilantin – increasing effectiveness of
ion transport; treats seizures
Go to Mouse Party for the affects of illegal drugs on
neurotransmitters…
The Brain
Sections 9.11 and 9.13
* Contains approximately
100 Billion neurons
* Weighs about 3 pounds
Meninges: The Coverings
• Three Layers:
1. Dura mater –
outermost, tough,
white
2. Arachnoid mater –
middle, web-like, CSF
in subarachnoid space
3. Pia mater –
innermost, very thinMeningitis: Inflammation of the meninges
on top of brain tissue
and CSF; typical causes are bacteria or
virus; spinal tap needed to diagnose
Get your vaccination before college!
Cerebrospinal Fluid - CSF
• Clear and colorless
• Circulates within the
ventricles and sub-arachnoid
space throughout CNS.
• Produced by the ependymal
glial cells.
• Provides cushioning,
optimum chemical
environment, and
nutrient/waste exchange.
• Hydrocephalus – too much
CSF, blockage usually the
cause, can cause neuron
damage.
Hydrocephalus
Major Brain Structures
• Cerebrum- Divided into 4 lobes:
(frontal, parietal, occipital, temporal)
• Diencephalon:
(thalamus, hypothalamus, epithalamus)
• Brain Stem:
(midbrain, pons, medulla oblongata)
• Cerebellum
Cerebrum
• Two cerebral hemispheres
• Longitudinal fissure separates hemispheres.
• Surface area increased with Gyri (ridges) and
Sulci (creases) or Fissures (deep grooves).
• Connected by the Corpus Callosum
• Function: Intelligence, memory, learning
• Cerebral cortex – gray matter, outermost, all
conscious thinking occurs here
• Olfactory bulb – sense of smell
Parieto-occipital
sulcus
Functions of the Cerebrum
Prefrontal Cortex
Problem Solving, Emotion, Complex Thought
Motor Association Cortex
Coordination of complex movement
Primary Motor Cortex
Initiation of voluntary movement
Primary Somatosensory Cortex
Receives tactile information from the body
Sensory Association Area
Processing of multi-sensory information
Visual Association Area
Complex processing of visual information
Visual Cortex
Detection of simple visual stimuli
Wernicke's Area
Language comprehension
Auditory Association Area
Complex processing of auditory information
Auditory Cortex
Detection of sound quality (loudness, tone)
Broca's Area
Speech production and articulation
Let’s Probe the brain! – find out how scientists
found out where primary motor functions are.
Comparing Human, Dog and Rat
Brains
Diencephalon
Main structures:
1. Thalamus – main relay
station for sensory
impulses (except smell) to
the cerebral cortex.
2. Hypothalamus – regulates
visceral movement (BP, GI
tract, HR), body
temperature, water and
electrolytes, hunger,
thirst, stimulate pituitary,
maintains sleep and wake
patterns.
3. Epithalamus – contains
the Pineal gland which
Brain Stem
Three sections:
1. Midbrain – visual and
auditory reflex centers,
main motor pathway
2. Pons – “bridge”, relays
impulses between:
a. medulla/cerebrum
b. cerebrum/cerebellum
3. Medulla Oblongata –
regulates heart rate,
blood pressure,
respiration, coughing,
sneezing, vomiting,
swallowing
Cerebellum
• 2nd largest part of brain
• Controls muscular
coordination
• Maintains posture
• Allows for smooth,
refined movements
• Involuntary once learned
Brain Disorders and
Diseases
Common Brain Injuries
• Concussion – abrupt, but temporary loss of
consciousness from a blow to the head.
Symptoms: headache, confusion, memory loss, lack of
concentration
• Contusion – bruising of the brain due to trauma,
leaking capillaries, commonly follows a
concussion. Pia mater torn.
Signs: Immediate loss of consciousness, loss of reflexes, decreased
blood pressure, cessation of respiration.
• Laceration – tear of the brain, large vessel
rupture, cerebral hematoma, increased
intercranial pressure.
Brain Tumors
Brain Aneurism
Cerebral thrombosis video
Strokes
Injury Effects
Phineas Gage
Injury re-enactment video
Man who survived a terrible brain
injury in the 1800’s. First
opportunity for scientists to study the
frontal lobe and limbic system
connection. Limbic system is the
emotional region and frontal keeps
the limbic region in control.
CAN YOU READ THIS?
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I was rdanieg. The phaonmneal pweor of the hmuan
mnid, aoccdrnig to a rscheearch at Cmabrigde
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in a wrod are, the olny iprmoatnt tihng is taht the frist
and lsat ltteer be in the rghit pclae. The rset can be a
taotl mses and you can sitll raed it wouthit a
porbelm. Tihs is bcuseae the huamn mnid deos not
raed ervey lteter by istlef, but the wrod as a wlohe.
Amzanig huh? yaeh and yuo Iawlyas tghuhot
slpeling was ipmorantt!
The Spinal Cord
Conus
medullaris
Cauda equina
Spinal Cord
• Functions – to conduct nerve impulses
and serve as the center of spinal
reflexes.
• Anatomy of the spinal cord:
1. Ascending tracts – from sensory to
brain
2. Descending tracts – from brain to
motor
3. Composed of gray and white matter.
4. Central canal contains the CSF.
5. Conus medullaris – end of cord at L1
Nerve structure
of the arm
31 pairs of spinal nerves
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–
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Cervical
Thoracic
Lumbar
Sacral
(What body regions do
these nerves connect
with?)
Dermatome
Map
Check skin sensations
to see what nerve has
been damaged.
Paraplegia – injury
below T1
Quadriplegia – injury
above T1
Cross-Section of Spinal Cord
Afferent impulses travel through dorsal root to cord.
Efferent impulses travel through ventral root to
effector.
Cross-section of Spinal Cord
Orientation of
grey and white
matter is
opposite of the
brain.
Grey matter =
cell bodies
White matter =
myelinated
axons
Reflexes
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Rapid, automatic responses to specific stimuli.
Their purpose is to preserve homeostasis.
Little variability in the responses.
Only a few neurons are needed.
“Wiring” of a single reflex = “Reflex Arc”
Testing somatic reflexes can be used for
diagnostic purposes.
Examples: swallowing, sneezing, vomiting,
and knee jerk.
Reflex Classification
Stretch Reflex: “Patellar reflex”
Muscle spindles = sensory receptors
involved in stretch reflexes
Innate Reflex: “Withdrawal reflex”
Lumbar Puncture or Spinal Tap
Needle inserted
between 3rd and
4th lumbar
vertebrae.
Epidural
Epidural given outside of the dura mater.
Herniated Vertebral Disc
Sciatica
• Compression and/or
irritation of a sciatic
nerve root or the
sciatic nerve itself.
• Symptoms: pain or
numbness in back,
buttock, and/or
parts of the leg and
foot
Spinal Tumor and Herniated Disc
Peripheral Nervous System
Sections 14 and 15
READ TONIGHT!!!
Peripheral Nervous System
PNS
Motor
(Efferent)
Sensory
(Afferent)
Somatic
Skin and
special senses
Somatic
(Voluntary)
Visceral
Skeletal
Muscles
Autonomic
(Involuntary)
Sympathetic
Parasympathetic
General Info
All nerves that branch off the CNS and connect
to other body parts.
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Cranial nerves – 12 pairs
Spinal nerves – 31 pairs
Functions:
1. To receive stimulus input and send to
CNS.
2. To relay the response from the CNS to
the appropriate effector organ.
Nerve
Anatomy
Afferent or Sensory Nerves
1. Picks up stimuli from:
a. internal environment
– visceral nerves
b. external environment
– somatic nerves
2. Sends to CNS for
interpretation
3. Typically unipolar or
bipolar neurons
Somatic nervous system
– All voluntary or conscious
activities
– Nerves connect to skeletal
muscles
– Pathways have one motor neuron
to muscle cells.
– Neurotransmitter: Acetylcholine
Autonomic nervous system
- All involuntary or unconscious activities.
- Maintains internal environment
- Nerves connect to cardiac, smooth
muscle or glands
- Pathways have two neurons synapsing at
a ganglia before effector.
- Neurotransmitters: Acetylcholine or
norepinephrine
- Two divisions counterbalance each other:
Sympathetic and Parasympathetic
Comparing Motor Neurons
Sympathetic
•
prepares for energy-expenditure,
excitement or stressful situations
•
"fight" or take "flight“.
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Nerve fibers originate from the thoracic
and lumbar regions of spinal cord.
Short Pre and Long postganglionic fibers
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Parasympathetic
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Stimulated during calm and relaxing
situations
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"rest" and "digest" .
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Nerve fibers originate from the brain and
sacral region.
Long preganglionic fibers and short post
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Which pathway is
responsible here?
Sympathetic or Parasympathetic
Division of the ANS are
distinguished by:
1. Unique origin sites
a. Sacrocranial vs. Thoracolumbar
2. Different lengths of their fibers
a. Preganglionic (long – Para, short – S)
b. Postganglionic (long – S, short – Para)
3. Location of their ganglia
a. P – close to effector
b. S – close to spinal cord