the nervous system
DESCRIPTION
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 - PowerPoint PPT PresentationTRANSCRIPT
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The Nervous SystemCh. 12-17
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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 Nerves2 Major Subdivisions
Afferent incoming pathwaysEfferent Outgoing pathways
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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
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Structure of a Neuron
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The Synapse Each synaptic/axon terminal is part of a
synapse Site where the neuron communicates with
another cellPresynaptic 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
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Neuron Video http://www.youtube.com/watch?v=r71R
oIkftd4
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Neuroglia Higher quantity and variation in CNS than
PNS Central Nervous System
1. Ependymal Cells2. Astrocytes3. Microglia4. Oligodendrocytes
Peripheral Nervous System1. Schwann Cells2. Satellite Cells
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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
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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
CNS Neuroglia
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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
PNS Neuroglia
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Synaptic ActivityMessages move from 1 location to another
in the form of action potentials along neuronsAlso known as nerve impulsesMessages move across the synapse
Can be electricalCan be chemical (use of neurotransmitter)
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Electrical SynapsesPresynaptic and postsynaptic cell
membranes are locked togetherLocal electrical currents and
directly transferred from cell to cell = very rapid electrical impulse Efficient action potential transfer
from cell to cell
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Chemical SynapsesPresynaptic and postsynaptic cell
membranes are NOT locked togetherMessage not guaranteed to be transferred
to the next cell dependent on the amount of neurotransmitters released Different neurotransmitters:
Acetocholyne: found at neuromuscular junctionNorepinephrine: excitatory effect, adrenalineDopamine: Parkinson’s disease (rigidity of
muscles) Serotonin: attention, emotion, responsible for
depressionGABA: reduce anxiety
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Spinal Cord and Spinal NervesChapter 13
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Spinal Cord Anatomy Posterior/Anterior/Lateral Horn of Gray matter Anterior Median Fissure Posterior Median Sulcus Spinal Nerve (Posterior/Anterior Roots) Spinal Ganglion
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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
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Meninges
Dura Mater Tough, fibrous
outermost layer Collagen fibers Covered with
blood vessels and adipose tissue
Epidural Space
Arachnoid Filled with
cerebrospinal fluid (SPF)—shock absorber
Spinal tap
Pia Mater Meshwork of
connective tissue Dense area of
vessels
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Nerve Plexuses Complex interwoven network of nerves Plexus. 1. Cervical Plexus
1. C1-C5 (muscles of neck, thoracic cavity)2. Brachial Plexus
1. C5-T1 (muscles of pectoral girdle and upper limb)3. Lumbar Plexus
1. T12-L4 4. Sacral Plexus
1. L4-S4
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Day 2
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RefluxesChapter 13
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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)
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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
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Reflexes1. Arrival of a stimulus and activation of receptor (pain)2. Activation of a Sensory Neuron (action potential
along axons of neurons spinal cord)3. Information Processing (neurotransmitter released
and sensation related to brain)4. Activation of Motor Neuron (axons carry action
potential back towards the origin of pain)5. Response of Peripheral Effector (release of
neurotransmitter to skeletal muscle fiber contraction pulls hand away from pain)
http://www.youtube.com/watch?v=wLrhYzdbbpE
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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
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The Brain and Cranial NervesChapter 14
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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
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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
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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
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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
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stop
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Cerebellum 2nd Largest portion of the brain 2 hemispheres 2 Primary Functions
Adjusting Postural muscles of the body Programming and fine-tuning movements
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Other Major Regions of the Brain Diencephalon:
Thalamus: relay and processing centers for sensory information
Hypothalamus: emotions, autonomic function, hormone production, body temp regulation
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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
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Ventricles of the Brain Chambers filled with cerebrospinal
fluid (CSF) 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 and opens into the spinal cord
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Protection and Support Protected by
1. Bones of cranium: mechanical protection (car)
2. 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)
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Cerebrospinal Fluid (CSF) Function:
Cushion Support Transport
nutrients/chemical messengers/waste products
Formation: Choroid plexus (in all
ventricles): specialized cells that produce CSF
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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
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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
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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
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Cranial Nerves1. Olfactory Nerves smell2. Optic Nerves Vision3. Oculomotor Nerves Eye Movements4. Trochlear Nerves Eye movements5. Trigeminal Nerves Sensory/Motor to face6. Abducens Nerves Motor eye movements7. Facial Nerves Sensory/Motor to face8. Vestibulocochlear Nerves balance/equilibrium and
hearing9. Glossopharyngeal Nerves Sensory/Motor to head
and neck10. Vagus Nerves Sensory/Motor to thorax and abdomen11. Accessory Nerves Motor to muscles of neck and
upper back12. Hypoglossal Nerves Motor for tongue movements
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“Oh, once one takes the anatomy final, very good vacations are heavenly”
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Sleep
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Conscious/Unconscious Conscious = state of awareness of
external stimuli Unconscious = number of conditions,
deep, unresponsive state drifting into sleep
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Levels of Sleep 2 levels, patterns of brain activity
1. 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
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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
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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)
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Composed of: Brain Spinal Cord Nerves
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Sense of smell activity
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Sense of smell optionsCinnamonLemonOrangeRootbeerStrawberry
GrapesCherryPeppermintBaby powderRose
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Sense of Smell Key1. Baby
powder2. Cinnamon3. Rose4. Lemon5. Strawberry
6. Cherry7. Root beer8. Peppermint9. Orange10.Grape
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Action Potential= The membrane potential of a neuron that is conducting an impulse (nerve impulse)
Action potential is an all-or-none response
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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
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Action Potential Video Video 2