Download The Nervous System

The Nervous
System
Ch. 12-17
The Nervous System Introduction
Composed of
 Brain
 Spinal Cord
 Nerves
 2 Major Subdivisions
 CNS (Central Nervous System)
 Brain, Spinal Cord
 PNS (Peripheral Nervous System)
 Cranial and Spinal Nerves
 2 Major Subdivisions
 Afferent  incoming pathways
 Efferent  Outgoing pathways

Neurons
 Remember

neuron structure:
The Cell Body or Soma
 Contains
a nucleus surrounded by cytoplasm along with all
other organelles found within a cell

The Dendrites
 Extensions
from Cell Body/Soma
 Receives information

The Axon
 Single,
long extension from Cell Body/Soma
 Branch out into telodendria and end at synaptic/axon
terminals
Structure of a Neuron
The Synapse
 Each
synaptic/axon terminal is part of a
synapse
 Site where the neuron communicates with
another cell
 Presynaptic
Cell: sends the message (usually a
neuron)
 Postsynaptic Cell: receives the message (any
cell type)
 After a series of electrical signals is transmitted
through the neuron, the axon/synaptic
terminals release chemicals or
neurotransmitters to the dendrite of another
cell to continue the message
Synaptic Cleft
Synapse
Neuron Video
 http://www.youtube.com/watch?v=r71Ro
Ikftd4
Neuroglia
 Higher
quantity and variation in CNS than PNS
 Central Nervous System
1. Ependymal Cells
2. Astrocytes
3. Microglia
4. Oligodendrocytes
 Peripheral Nervous System
1. Schwann Cells
2. Satellite Cells
CNS Neuroglia
Ependymal Cells
 Line
ventricles in
the brain and
spinal cord
 Aid in producing,
circulating and
monitoring of
cerebrospinal fluid
Microglia
 Removes
cell
debris, wastes, and
pathogens by
phagocytosis
CNS Neuroglia
Astrocytes




Provide structural
support
Regulate ion, nutrient,
and dissolved gas
concentrations
Absorb and recycle
neurotransmitters
Form scar tissue after
injury
Oligodendrocytes
 Myelinate
axons
 Provide structural
framework
PNS Neuroglia
Schwann Cells
 Surround
all axons
 Responsible for
myelination
 Participate in repair
process after injury
Satellite Cells
 Surround neuron
cell bodies
 Regulate gas,
nutrient, and
neurontransmitter
levels
Synaptic Activity
 Messages
move from 1 location to another
in the form of action potentials along
neurons
 Also known as nerve impulses
 Messages move across the synapse
Can
be electrical
Can be chemical (use of neurotransmitter)
Electrical Synapses
 Presynaptic
and postsynaptic cell
membranes are locked together
 Local electrical currents and
directly transferred from cell to cell
=
 very
rapid electrical impulse
 Efficient action potential transfer
from cell to cell
Chemical Synapses
 Presynaptic
and postsynaptic cell
membranes are NOT locked together
 Message not guaranteed to be transferred to
the next cell  dependent on the amount of
neurotransmitters released
 Different
neurotransmitters:
 Acetocholyne:
found at neuromuscular junction
 Norepinephrine: excitatory effect, adrenaline
 Dopamine: Parkinson’s disease (rigidity of
muscles)
 Serotonin: attention, emotion, responsible for
depression
 GABA: reduce anxiety
Spinal Cord and
Spinal Nerves
Chapter 13
Spinal Cord Anatomy
 Posterior/Anterior/Lateral
 Anterior
Horn of Gray matter
Median Fissure
 Posterior Median Sulcus
 Spinal Nerve (Posterior/Anterior Roots)
 Spinal Ganglion
Spinal Cord
Anatomy
 Adult
– 18 inches in length
 Only reaches down to L1-L2
 Spinal Meninges:
specialized membranes
that surround the spinal
cord



Dura Mater
Arachnoid
Pia Mater
 Bacterial
or vial infections of
the Meninges  Meningitis
Meninges
Dura Mater
 Tough, fibrous
outermost layer
 Collagen fibers
 Covered with
blood vessels and
adipose tissue
 Epidural Space
Pia Mater
 Meshwork of
connective tissue
 Dense area of
vessels
Arachnoid
 Filled
with
cerebrospinal fluid
(SPF)—shock
absorber
 Spinal tap
Nerve Plexuses
 Complex
1.
interwoven network of nerves  Plexus.
Cervical Plexus
1.
2.
Brachial Plexus
1.
3.
C5-T1 (muscles of pectoral girdle and upper limb)
Lumbar Plexus
1.
4.
C1-C5 (muscles of neck, thoracic cavity)
T12-L4
Sacral Plexus
1.
L4-S4
Day 2
Refluxes
Chapter 13
Reflexes
 Rapid
automatic responses to a specific
stimuli made by a receptor


Preserve homeostasis
Rapid adjustments
 The


Reflex Arc: wiring of a single reflex
Beings at the receptor
Ends at peripheral effector (ex: muscle
fiber)
Reflexes
 Sensory






Receptors
Proprioreceptors: provide info about body
position and muscle control
Vestibular Receptors: provide a sense of
equilibrium
Cutaneous Receptors: touch, pressure, heat
and cold
Photoreceptors: respond to light
Chemoreceptors: respond to taste
Nocioreceptors: pain receptors
Reflexes
1.
2.
3.
4.
5.

Arrival of a stimulus and activation of receptor (pain)
Activation of a Sensory Neuron (action potential along
axons of neurons  spinal cord)
Information Processing (neurotransmitter released and
sensation related to brain)
Activation of Motor Neuron (axons carry action
potential back towards the origin of pain)
Response of Peripheral Effector (release of
neurotransmitter to skeletal muscle fiber contraction
pulls hand away from pain)
http://www.youtube.com/watch?v=wLrhYzdbbpE
Reflexes
 Receptor


Density
More dense the receptors = more “sensitive” the area
Upon stimulation…
 Phasic:
receptors respond with an initial burst of action
potentials and rapidly decrease, even though stimulus
continues
 Tonic: receptors firing at a constant rate as long as the
stimulus is applied
1.
Lab on reflexes
The Brain and
Cranial Nerves
Chapter 14
Human Brain
 Contains
98% of neural tissue
 Weighs about 3 lbs
 Covered by a neural cortex (superficial layer of
gray matter
 Main Areas




Cerebrum
Cerebellum
Diencephalon
Brain Stem
Cerebrum
 Largest
portion of the brain
 2 hemispheres

Controls thoughts, sensations, intellect, memory,
and complex movements
 Lobes




(correspond with cranial bones)
Frontal
Parietal
Occipital
Temporal
Cerebrum
 Landmarks




Longitudinal fissure (separates the 2 hemispheres)
Central Sulcus (separates the frontal from parietal
lobes)
Lateral Sulcus (separates the frontal from temporal)
Parieto-occipital sulcus (separates the parietal from
the occipital)
 White

Matter
Dense region of axons
Cerebrum
 Motor





and Sensory Areas
Frontal Lobe = Voluntary control of skeletal muscles
Parietal Lobe = conscious perception of touch,
pressure, vibration, pain, temperature, and taste
Occipital Lobe = conscious perception of visual
stimuli
Temporal Lobe = conscious perception of auditory
and olfactory stimuli, speech
All Lobes = Integration and processing of sensory
data and motor activities
stop
Cerebellum
 2nd
Largest portion of the brain
 2 hemispheres
 2 Primary Functions


Adjusting Postural muscles of the body
Programming and fine-tuning movements
Other Major Regions of the Brain
 Diencephalon:


Thalamus: relay and processing centers for sensory
information
Hypothalamus: emotions, autonomic function, hormone
production, body temp regulation
Other Major Regions of the Brain
 Brain



Stem :link between cerebrum and brain stem
Mesencephalon: aka “midbrain”; visual and auditory
information
Pons: sleep & respiration
Medulla Oblongata: regulate heart rate, blood pressure,
digestion
Ventricles of the Brain
 Chambers
fluid (CSF)




filled with cerebrospinal
Lateral Ventricles (2 in each
hemisphere of cerebrum)
Third Ventricle
Interventricular Foramen
(connection between the lateral
ventricles and third ventricle)
Cerebral Aqueduct
 (connection
between the third
ventricle and fourth ventricle)

Fourth Ventricle
 Narrows
cord
and opens into the spinal
Protection and Support
 Protected
1.
2.
by
Bones of cranium: mechanical
protection (car)
Cranial Meninges: anchor (seat
belt)
 Dura
Mater: outer layer
 Arachnoid: middle layer
 Pia Mater: surface of brain
3.
Cerebrospinal Fluid: cushions
against shocks/jolts (air bag)
Cerebrospinal Fluid (CSF)
 Function:



Cushion
Support
Transport
nutrients/chemical
messengers/waste
products
 Formation:

Choroid plexus (in all
ventricles):
specialized cells that
produce CSF
Blood Supply to the Brain
 Brain
requires a tremendous amount of blood
 Receives 15-20% of blood pumped by heart
 Interruption  unconsciousness/irreversible brain
damage
 Dependent on constant supply of oxygen &
glucose
 Receives blood through arteries
Hydrocephalus
 Condition



with infants
Prior to fusion of cranial bones
Excess CSF (due to blockage or constriction
of the meninges)causes the skull to enlarge
Infants suffer some degree of mental
retardation
Cranial Nerves
 Part
of the PNS
 Connected to the brain and branch out
 12 of them
 Attaches the brain near a sensory or
motor neuron
 2 of each
Cranial Nerves
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
Olfactory Nerves smell
Optic Nerves  Vision
Oculomotor Nerves  Eye Movements
Trochlear Nerves  Eye movements
Trigeminal Nerves  Sensory/Motor to face
Abducens Nerves  Motor eye movements
Facial Nerves  Sensory/Motor to face
Vestibulocochlear Nerves  balance/equilibrium and
hearing
Glossopharyngeal Nerves  Sensory/Motor to head
and neck
Vagus Nerves  Sensory/Motor to thorax and
abdomen
Accessory Nerves Motor to muscles of neck and
upper back
Hypoglossal Nerves  Motor for tongue movements
“Oh, once one takes the anatomy final, very good
vacations are heavenly”
Sleep
Conscious/Unconscious
 Conscious
= state of awareness of
external stimuli
 Unconscious = number of conditions,
deep, unresponsive state  drifting into
sleep
Levels of Sleep
2
1.
levels, patterns of brain activity
Slow wave sleep
 Deep
sleep/non-REM sleep
 Entire body relaxed
 Cerebral cortex activity at minimum
 Heart rate, blood pressure, respiratory rate, energy
utilization decline by 30%
2.
Rapid Eye Movement (REM sleep)
 Active
dreaming
 Changes in blood pressure/respiratory rate
 Muscle tone decreases
 Neurons controlling eye muscles stop regulation = eyes
move rapidly as dream events unfold
Sleeping Cycles
 REM
and Deep sleep
alternate throughout
the night
 Starts with Deep sleep =
1.5 hours
 REM last on average 5
minutes
 Determined by an EEG

Electroencephalogram:
graphic record of the
electrical activities of
the brain
Alzheimer’s Disease
 Loss
of cerebral functions
 Symptoms appear around 50-60 years old

Can affect younger individuals but is rare
 Currently
affects 2 million ppl in USA
 100,000 deaths each year
 Chromosome 14, 19, and 21

Majority of Downs Syndrome develop it (21)
Composed of:
 Brain
 Spinal
Cord
 Nerves
Sense of smell activity
Sense of smell options
Cinnamon
Cherry
Orange
Baby
Lemon
Rootbeer
Strawberry
Grapes
Peppermint
powder
Rose
Sense of Smell Key
1. Baby
6. Cherry
powder
7. Root beer
2. Cinnamon 8. Peppermint
3. Rose
9. Orange
4. Lemon
10.Grape
5. Strawberry
Action Potential
= The membrane potential of a neuron that is
conducting an impulse (nerve impulse)
 Action
potential is an all-or-none response

Resting membrane potential (RMP) at -70mV.


Na+ on outside and K+ on inside of cell
Stimulus at dendrites triggers Na+ channels to
open, causing local depolarization.

If the opening is sufficient to drive the interior
potential from -70 mV up to -55 mV, the process
of depolarization continues.

As depolarization reaches threshold of -55mV,
the action potential is triggered and Na+
rushes into cell until membrane potential
reaches +30mV on action potential

Propagation of the action potential at 100
m/sec (which is 225 mph)

Repolarization occurs with K+ exiting the cell
to return to -70mV RMP
Return of ions (Na+ and K+) to their
extracellular and intracellular sites by the
sodium potassium (Na+K+) pump
Continues until RMP is met


 Action
Potential Video
 Video 2