Transcript The Nervous System

The Nervous System (Ch. 9)
Chapters 9 and 10
Terminology
 Neurology: branch of science that deals with the
functioning & disorders of the nervous system
 Plasticity: can change based on experience
 Cranial nerves: emerge from brain
 Spinal nerves: emerge from spinal cord
 Nerve: bundle of axons
 Ganglia: cluster of cell bodies
 Neuron: basic functioning unit of the nervous system
 Neuroglia: smaller, support structures for neurons;
higher in number than the 100 billion neurons in
brain and 100 million neurons in spinal cord
The Nervous System
 Two divisions:
 Central & Peripheral
Central or CNS- brain and
spinal cord
Peripheral or PNS- nerves
connecting CNS to muscles
and organs
• SNS: somatic
• ANS: autonomic
– Sympathetic &
parasympathetic
Central Nervous System
Peripheral Nervous System
Functions of Nervous System
 3 functions
Sensory: detect stimuli
Integrative: analyzes and stores
information
Motor: responds to information
Nervous Pathway
*Remember a
receptor
perceives a
stimulus
Sensory neuron=
Afferent neuron
Receptor
*Effectors are
usually muscles
and glands.
Control
Center
(CNS)
Motor neuron=
Efferent neuron
Effector
Basic Neuron Parts
Neuron Parts
 3 basic parts:
Cell body: integrates stimuli
Dendrites: receive impulse and send to cell
body
Many per neuron
Axon: send impulse away from cell body
onto another neuron or effector
one per neuron
More neuron parts to know
Look on p. 216, figure 9.4
Schwann Cells: cells surrounding the axon
Neurolemma: cell membrane on Schwann cells
Nodes of Ranvier: indentations between Schwann
cells
 Myelin: lipid substance that occupies Schwann cells;
insulates impulse traveling on axon
this substance is the reason why CNS repair is
usually not possible
 Synaptic end bulbs: enlarged part of axon terminal
that secretes neurotransmitters
Synapse = space between neurons
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More neuron parts to know
Neurons can be…
 Myelinated
Myelin is present
Comprises white matter in brain and spinal
cord
Functions in nerve impulse conduction
 Unmyelinated
Myelin is absent
Comprises gray matter in the brain and
spinal cord
Functions in nerve impulse integration
Organization
 Tracts
Bundle of axons in CNS
2 types
Ascending: carry impulses from spinal cord UP
to brain
Descending: carry impulse from brain DOWN to
spinal cord
Works sort of like a 2 way street.
Nervous Impulses
 Action potential = how neurons communicate with one
another
Created by Sodium (Na+) and Potassium (K+) ions
 Polarized membranes: charges are opposite so
potential energy results
 Resting membranes: charges are alike so no energy
results = resting period
 Threshold: level that must be reached in order to send
an impulse
All-or-none principle
 Anesthesia: blocks the Na+ and K+ channels so pain
signals do not reach the CNS
Central Nervous System
Brain
 Brain and Spinal Cord
Spinal
Cord
Neurotransmitters
 Acetylcholine: excitatory (muscle
contraction)
 Norepinephrine: awakening from sleep;
resting
 Epinephrine: fight or flight
 Dopamine: regulates muscle tone
 Serotonin: sensory perception (eg. happiness)
 Endorphins: pain relief
*See Table 9.2 on p. 226
Spinal Cord
 Located in vertebral canal
 Covered in meninges (layers of connective tissue)
3 layers with CSF (cerebrospinal fluid)
Dura mater (outer) = dense, tough, fibrous
Arachnoid mater (middle) = spider-web
Pia mater (inner) = thin
Epidural space between vertebrae & dura mater
• Space for administering epidurals
Subarachnoid space between arachnoid & pia mater
• Space where spinal tap/lumbar puncture is
performed
 16-18 inches long
 Extends from foramen magnum to L2 (then cauda
equina emerges)
Spinal Cord
Reflexes
 Fast, automatic responses
 Follow a pathway called the reflex arc
 Somatic reflexes
Involve skeletal muscle
Ex: patellar reflex (“knee jerk”),
withdrawal reflex
 Autonomic reflexes
Involve smooth and cardiac muscle
Ex: swallowing, urinating, defecating
Spinal Nerves
 31 pairs
Cervical – 8
C1-C8
Thoracic – 12
T1-T12
Lumbar – 5
L1-L5
Sacral – 5
S1-S5
Coccygeal - 1
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Brain
One of the largest organs
Contains 100 billion neurons and 1 trillion neuroglia
Weighs ~ 3 pounds
Covered by same 3 meninges layers + CSF
4 major parts:
Brain stem, diencephalon, cerebrum, cerebellum
 Requires 20% of body’s oxygen
Low O2 = unconsciousness, brain damage
 Requires normal glucose levels
Low glucose = confusion, dizziness, convulsions
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Cerebrospinal Fluid (CSF)
Clear
Colorless
80-150 mL
Delivers nutrients to brain and spinal cord
Removes wastes & toxins from brain and spinal cord
Lubrication
Can be tested through lumbar puncture/spinal tap
Hydrocephalus (water head) can result from too much
CSF
 Made in ventricles on brain
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Brain Stem
 Consists of 3 parts:
Medulla (continuous with spinal cord)
Controls vital signs
Pons (bulges anteriorly)
Regulates rhythmic respiration
Midbrain
Perceives auditory & visual reflexes
Diencephalon
 Consists of 2 parts
Thalamus
Principle relay station for sensory impulses
cognition
Hypothalamus
Controls homeostatic activities
Controls ANS, pituitary gland, body temperature,
emotions, behaviors, eating & drinking (satiety
center), circadian rhythms (sleep-wake cycle)
Cerebellum
 2nd largest portion of the brain
 Consists of 2 hemispheres connected by
arbor vitae
 Controls coordinated movements, posture,
balance
 Protected by occipital bone
Cerebrum
 Largest portion of the brain
 Consists of 2 hemispheres connected by
corpus callosum
 Folds = gyri & grooves = sulci
 Controls coordinated movement, senses
memory, judgement, intelligence
Corpus Callosum
 Major (but not only)
Medial surface of right hemisphere
pathway between sides
 Connects comparable
structures on each side
 Permits data received on
one side to be
processed in both
hemispheres
 Aids motor coordination
of left and right side
Corpus Callosum
Electroencephalogram (EEG)
graphical reading of brain waves to determine normal function
Cranial Nerves – 12 pairs
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I. Olfactory: smell
II. Optic: sight
III. Oculomotor: eye movement
IV. Trochlear: eye movement & proprioception
V. Trigeminal: chewing, touch, pain
VI. Abducens: eye movement
VII. Facial: facial expression
VIII. Vestibulocochlear: hearing & equilibrium
IX. Glossopharyngeal: taste, swallowing
X. Vagus: swallowing, coughing
XI. Spinal Accessory: head & shoulder movement
XII. Hypoglossal: tongue movement
*TABLE 9.6 on p. 246*
12 Cranial Nerves
Cranial nerves continued
 You must know these nerves IN ORDER
 It will be beneficial to know them before
dissection as you will have to label them on
the brain.
 Remember: Oh, Oh, Oh, That Trashy And Fat
Vain Girl’s Van Almost Hydroplaned OR
make up your own study device
Diseases/Disorders
 Parkinson’s: dopamine is slow or no longer
released; causes tremors & possible muscle
rigidity
 Multiple Sclerosis: chronic myelin
degeneration
 Alzheimer’s: causes disabling senile
dementia
 Meningitis: inflammation of meninges
Viral & bacterial
 Cerebrovascular Accident (CVA) = stroke
3rd leading cause of death in the US
Brain scan of stroke patient
 Broca’s Area 
speech
Peripheral Nervous System
2 subdivisions
Autonomic
Nervous system
(ANS)
Somatic Nervous
system (SNS)
Brain
Spinal
Cord
Nerves
Somatic Nervous System
(SNS)
 Utilizes
sensory and
Sensory
motor neurons
Neuron
 Produces
voluntary and
conscious
Skin receptors
movements
Brain
Motor
Neuro
Interneuron
n
Muscle
Autonomic Nervous
System (ANS)
 Controls involuntary functions
heartbeat
blood pressure
respiration
perspiration
digestion
 Can be influenced by thought and emotion
 Two divisions:
sympathetic
parasympathetic
Sympathetic & Parasympathetic
(Have opposing effects on the body)
 Sympathetic
Neurons synapse
with MANY other
neurons =
widespread bodily
responses
Most neurons are
adrenergic (cause
long-lasting
responses)
 Parasympathetic
Neurons synapse
with FEW other
neurons = local
bodily responses
Most neurons are
cholinergic (cause
short-lasting
responses)
Sympathetic division =
Thoracolumbar division
 “ Fight or flight”
response
 Release
adrenaline
(epinephrine) and
noradrenaline
(norepinephrine)
 Impulses come
from thoracic and
lumbar spinal
nerves
 Increases heart
rate and blood
pressure
 Increases blood
flow to skeletal
muscles
 Inhibits digestive
functions
CENTRAL NERVOUS SYSTEM
SYMPATHETIC
Brain
Dilates pupil
Stimulates salivation
Relaxes bronchi
Spinal
cord
Salivary
glands
Lungs
Accelerates heartbeat
Inhibits activity
Heart
Stomach
Pancreas
Stimulates glucose
Secretion of adrenaline,
nonadrenaline
Relaxes bladder
Sympathetic
ganglia
Stimulates ejaculation
in male
Liver
Adrenal
gland
Kidney
Parasympathetic division =
Craniosacral division
“ Rest and
digest” response
Calms body to
conserve and
maintain energy
Lowers
heartbeat,
breathing rate,
blood pressure
 Impulses come
from cranial
nerves and sacral
spinal nerves
 SLUDD
Salivation
Lacrimation
Urination
Defecation
digestion
CENTRAL NERVOUS SYSTEM
PARASYMPATHETIC
Brain
Contracts pupil
Stimulates salivation
Spinal
cord
Constricts bronchi
Slows heartbeat
Stimulates activity
Stimulates gallbladder
Gallbladder
Contracts bladder
Stimulates erection
of sex organs
Summary of autonomic
differences
Sympathetic
division (arousing)
Pupils dilate
Parasympathetic
division (calming)
EYES
Pupils constrict
SALIVATION
Increases
Perspires
SKIN
Dries
Increases
RESPIRATION
Decreases
Accelerates
HEART
Slows
Inhibits
DIGESTION
Activates
Secrete stress
hormones
ADRENAL
GLANDS
Decrease secretion
of stress hormones
Decreases
Paradoxical Fear – p. 251
 Parasympathetic division overrides the
sympathetic division
 Caused during extremely stressful situations
and the body realizes there is no way out/no
way to win