Transcript File

Chapter 6: The Nervous System
Lesson 6.1
Overview of the
Nervous System
Agenda & Key Points
• organization of the nervous system
– two major divisions
– the efferent nerves-subdivisions
• nervous tissues
– Neuroglia-support and protection
– Neurons-transmitting information (nerve impulses)
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Organization of the Nervous System
• two major divisions
– central nervous system (CNS)
– peripheral nervous system (PNS)
• Autonomic-(Cardiac & Smooth)
– Parasympathetic-routine involuntary
– Sympathetic-high alert
• Somatic- (Skeletal)
– sensory receptors ( special nerves- pressure, pain and
temp)
• afferent (sensory) nerves- From PNS to CNS
• efferent (motor) nerves- From CNS to PNS
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Two Major Divisions
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The Efferent Nerves (Motor Nerves)
• somatic nervous system
– Voluntary
– skeletal
• autonomic nervous system
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Involuntary
Smooth and cardiac
Sympathetic -6.4 (fight or flight)
Parasympathetic -6.4 ( rest and digest)
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Nervous Tissues
• neuroglia
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also known as glial cells
support the neurons
protect the neurons
Types:
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Astrocytes- between neurons and capillaries ½ of all glials
Microglia- disposals
Ependymal cells- line, cover and protect cavities
Oligodendrocytes- produce myelin in CNS
• Schwann cells- produce myelin in PNS
• Satellite Cells- cushion and support
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Neuroglia
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Nervous Tissues
• Neurons-transmit nerve impulses
• Neuron Anatomy
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Cell body-nucleus and mitochondria
Axon-sends info away from cell body
Dendrites-collect and transport stimuli
Myelin sheath-fatty insulation to increase rate on
impulse transmission ( white vs gray matter)
– Neurilemma-external covering of schwann cells
– Nodes of ranvier-uninsulated gap between schwann cell
– Synapse-gap between axon terminals and muscles or
other neurons (neuromuscular junction if muscles)
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Neuroglia
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Neuron Types by Function
• sensory neurons
– send impulses toward CNS
• motor neurons
– send impulses away from CNS
• interneurons
– bridges between neurons
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Neuron Structures
• bipolar
– one axon
and one
dendrite
• unipolar
– one axon
– PNS
• multipolar
– one axon and
many dendrites
– CNS, Motor and
interneurons
– (eyes and nose)
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Review and Assessment
Match these words with 1–4 below: sympathetic
nervous system, myelin, synapse, axon.
1. high alert
2. transmits impulses away from cell body
3. fatty insulating material
4. gap between neurons
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Chapter 6: The Nervous System
Lesson 6.2
Transmission of
Nerve Impulses
Agenda and Key Points
• Neurons are irritable too!
• action potentials
– change in cell membrane charge
• impulse transmission
– charge change travels along axon
• reflexes
– response to stimulus
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Action Potentials
• Conductivity-ability to transmit nerve impulses
• Polarized-difference in charge inside the cell
(negative), Sodium outside, Potassium inside
• Depolarized-(positive), flood of sodium ions inside
• Nerve impulse-wave of depolarization (action
potential) all or none
• Repolarized-return to original state
• Refractory Period-between impulse and
repolarization (fatigue). Can’t respond
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Impulse Transmission
• Speed of transmission: 1-119 m/s
– Myelin sheath- any impulse>1m/s
– Diameter of axon
– Body temperature- warmer=faster
• Saltatory conduction-jump overs
– Faster transmission
– Nodes of Ranvier (myelin)
• transmission at synapses
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gap junctions
neurotransmitter
excitatory effect-acetylcholine
inhibitory effect-endorphins
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Reflexes
• somatic
– stimulate skeletal muscles, voluntary
• autonomic
– stimulate involuntary muscles, cardiac/smooth
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Chapter 6: The Nervous System
Lesson 6.3
Functional Anatomy of the
Central Nervous System
Agenda and Key points
• Brain (2.25-3.25 lb, 100 billion neurons)
• Cerebrum
– 2 hemispheres
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diencephalon
brain stem
cerebellum
meninges
blood-brain barrier
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Cerebrum
• cerebral cortex- outer surface=gray matter, inner= white matter
– Convolutions= wrinkles
• Gyrus- raises
• Sulcus- grooves
• Fissure- deep grooves
– lobes
– Frontal• broca’s area (L)
• primary motor cortex- coordination
– parietal
• primary somatic sensory cortex-sensory info
– Occipital
• vision
– Temporal
• Speech, hearing, vision, memory
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Cerebrum
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Diencephalon
• Thalamus
– Relay station
– Sleep and awake
• Hypothalamus
– Pearl sized
– Metabolism, heart rate, bp, pain and pleasure
• epithalamus
– Pineal gland and sleep hormones
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Brain Stem
• Midbrain – most superior part of brain stem
– Sensory and motor impulses
– Vision, hearing, motor, temperature, sleep cycle
• Pons- middle of brain stem
– Breathing regulation
• medulla oblongata- most inferior
– Heart rate, blood pressure, breathing
– Reflexes for cough, sneeze and vomiting
• As long as the brain stem is functional, the body
will live (with hydration and nutrition)
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The Brain
• Cerebellum
– Below occipital lobe
– Balance and
coordination, body
position
• blood-brain barrier
– Lots of blood flow (2025% at any given time)
– Capillaries are
impermeable to many
substances
– Water, glucose and
amino acids can pass
– So can alcohol, nicotine
and anesthetics
• Meninges- protective
membranes
– dura mater
– Tough, double layered.
Inner layer extends to
spinal cord
– arachnoid mater
– Web-like
– Underneath is CSF
– pia mater
– Delicate. Attaches
directly to brain
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Meninges
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Spinal Cord
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Chapter 6: The Nervous System
Lesson 6.4
Functional Anatomy
of the Peripheral
Nervous System
Functional Anatomy of the Peripheral
Nervous System
•
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nerve structure
cranial nerves
spinal nerves and nerve plexuses
autonomic nervous system
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Nerve Structure
• endoneurium
– covers axons
• perineurium
– bundles fascicles
• epineurium
– wraps nerves
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Cranial Nerves
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Spinal Nerves and Nerve Plexuses
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31 pairs
dorsal root
ventral root
dorsal ramus
ventral ramus
plexuses
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Autonomic Nervous System
• preganglionic and postganglionic neurons
• sympathetic nerves
– fight-or-flight action
• parasympathetic nerves
– resting or digesting action
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Review and Assessment
Match these words with 1–4 below: efferent,
ganglion, optic, perineurium.
1. wraps fascicles
2. motor
3. a cranial nerve
4. enlarged junction
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Chapter 6: The Nervous System
Lesson 6.5
Injuries and Disorders of
the Nervous System
Injuries to the Brain and Spinal Cord
• traumatic brain injury
• cerebral palsy
• spinal cord injury
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Traumatic Brain Injury
• violent impact to head
– mild
– moderate
– severe
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Cerebral Palsy
• damage to brain
– before birth
– during birth
– during infancy
• motor function impairment
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Spinal Cord Injuries
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C1–C3: usually fatal
C1–C4: quadriplegia
C5–C7: paralysis of lower extremities
T1–L5: paraplegia
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Common Diseases and Disorders of the
CNS
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meningitis
multiple sclerosis
epilepsy
Parkinson’s disease
dementia and Alzheimer’s disease
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Review and Assessment
Match these words with 1–4 below: quadriplegia,
multiple sclerosis, dementia, cerebral palsy.
1. inflammation destroys myelin sheath
2. loss of memory and thinking
3. loss of function below the neck
4. may begin before birth
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