anatomy and physiology of neurosensory
TRANSCRIPT
Nervous SystemAnd Neurological
Disorders: A Nursing Management Perspective
1. Which of the following is a component of the midbrain?
A. Cerebral hemisphere
B. Tegmentum
C. Cerebellum
D. Medulla oblongata
2. Which of the following is an insulating substance for the neuron?
A. Schwann cells
B. Myelin
C. Neuroglial cells
D. Node of Ranvier
3. Which of the following neurotransmitters is released from the postganglionic parasympathetic axon terminal?A. AcetylcholineB. EpinephrineC. NorepinephrineD. Dopamine
4. Which of the following best describes successive, rapid impulses recieved from a single neuron on the same synapse?
A. Temporal summationB. Spatial summationC. ActuationD. Facilitation
5. Which of the following is not part of the meninges surrounding the brain?
A. Dura mater
B. Anterior fossa
C. Pia mater
D. Endosteal layer
The Nervous System• A physical organ system like any other
• The master controlling and communicating system of the body
3 Important Functions of the Nervous System:
• It receives information from the environment and inside the body.
• It interprets the information it receives.
• It makes the body respond to the information.
Nervous System
Figure 11.1
Overview and Organization of the Nervous System
Central Nervous System (CNS)
Brain Spinal Cord
Peripheral Nervous System (PNS)
Sensory Neurons
Motor Neurons
Somatic Nervous System• voluntary movements
via skeletal muscles
Autonomic Nervous System
• organs, smooth muscles
Sympathetic- “Fight-or-Flight”
Parasympathetic - maintenance
The Nervous System
Cells of the Nervous System
A Review of the Structure
The Neuron Basic units of the nervous system
Receive, integrate, and initiate body response
Operate through electrical impulses
Provide an instant method of cellular communication with other neurons through chemical signals
The Neuron• Organization
– Billions of Neurons (estimates of 100 billion)– Very complex interconnections– Create systems/circuits that can function
independently (parallel processing)– “Simple decisions” passed to “higher” levels for
that add additional information to create generate more complex decisions (hierarchical processing)
– Very expensive - less than 2% of weight but uses 20% of energy
Functional Classification of NeuronsFunctional Classification of Neurons Sensory (afferent) neurons
Carry impulses from the sensory receptors Cutaneous sense organs Proprioceptors – detect stretch or tension
Motor (efferent) neurons Carry impulses from the central nervous
systeM Interneurons (association neurons)
Found in neural pathways in the central nervous system
Connect sensory and motor neurons
16
More nerve terms p. 277
nerve fibers Dendrites and axions
nerve A bundle of dendrites and axions
nucleus(plural: nucleii)
A group of neuron cell bodies INSIDE the brain and spinal cord
ganglion(plural: ganglia)
A group of neuron cell bodies OUTSIDE the brain and spinal cord
synapse The space connecting one neuron to another
neurotransmitter A chemical which transmits an electrical impulse from one neuron to the next
Glial cells
• 100 billion neurons• 10x more glial cells than neuros• Glial cells
– Support neurons (literally, provide physical support, as well as nutrients)
– Cover neurons with myelin– Clean up debris– “Housewives”
Types of Supporting Cells of the Nervous System
• Astrocytes
• Microglia (CNS)
• Ependymal cells (CNS)
• Oligodendrocytes(CNS)
• Regulate external environment (ions, etc.)• Most abundant glial cell • May contribute to blood-brain barrier and to synapses
Astrocytes
Nervous Tissue: Nervous Tissue: Support CellsSupport Cells Microglia (CNS)
Spider-like phagocytes Remove debris
Ependymal cells (CNS) Line cavities in the
brain and spinal cord Circulate
cerebrospinal fluid
Nervous Tissue: Nervous Tissue: Support CellsSupport Cells
Oligodendrocytes(CNS)
Produce myelin sheath around nerve fibers in the central nervous system
Neuron Anatomy and Neural Communication
Neurons
The largest part of a typical neuron is the cell body. It contains the nucleus and much of the cytoplasm.
Cell body
Neurons
Axon of anotherneuron
Dendrites of another neuron
Dendrites Cell BodyMyelinSheath
Axon
Synapse
NeuronsCell Body
The Nucleus in the Center
Neurons
Dendrites
The main apparatus for receiving signals
Neurons
Axon The main conducting unit of the neuron
Action Potential
Neurons
Myelin Sheath
The main conducting unit of the neuron
Myelin Sheath– Fatty material made by
glial cells– Insulates the axon– Allows for rapid
movement of electrical impulses along axon
– Nodes of Ranvier: gaps in myelin sheath where action potentials are transmitted
– Speed of neural impulse Ranges from 2 – 200+ mph
3 Functions of the Neuron
Reception1.3.
2.
Transmission
Conduction
Neuron Function
• Electrical Activity– Used to transmit signal
within neuron• Chemical Activity
– Used to transmit signal between neurons
– Synapse – small gap that physically separates neurons
Neuron Function• Electrical Activity
– Resting Potential• Inside negative (-70 mV)
compared to outside• Inside has high K+ (negativity
comes from proteins & other negative ions)
• Outside has high Na+
• Forces at work– Electrical– Diffusion
Neuron Function
• Chemical (Neurotransmitter) Activity– Leads to graded potentials in neuron
• Excitatory NTs – causes depolarization in neuron• Initiatory NTs – causes hyperpolarization in neuron
Neuron – Excitation & Inhibition
Neuron - Synapse
Synapse Types
• Multiple ways of connecting– Examples
• Axon to Dendrite – excite or inhibit neuron• Axon to Axon Terminal – moderate NT release• Axon to Extracellular Space or blood – potential for
diffuse effects
Synapse Types
Synapse Function
• Neurotransmitter cycle in Axon Terminals– Synthesis– Storage– Release– Inactivation– Reuptake– Degradation
• Neural transmission problems if cycle disrupted (e.g., drugs) at any step
Synapse Function
Synapse Function
What is a Neurotransmitter?
• A substance that is released at a synapse by a neuron and that effects another cell, either a neuron or an effector organ, in a specialized manner
• This seems clear, but application becomes fuzzy
Neurotransmitter• Neurotransmitter is made by the
pre-synaptic neurone and is stored in synaptic vessels at the end of the axon.
• The membrane of the post-synaptic neurone has chemical-gated ion channels called neuroreceptors.
• These have specific binding sites for neurotransmitters.
Chemical Synaptic Transmission
• 4 steps:– Synthesis of transmitter– Storage & release of transmitter– Interaction of transmitter with
receptor in postsynaptic membrane
– Removal of transmitter from synaptic cleft
Classifying Neurotransmitters
• Once divided into 2 classes:– Cholinergic – use acetylcholine
(ACh)
– Adrenergic - use norepinephrine or epinephrine
Cholinergic Synapses
• Acetylcholine is a common transmitter.
• Synapses that have acetylcholine transmitter are called cholinergic synapses.
• This is an electron micrograph of synapses
between nerve fibres and a neurone cell body.
Central Nervous System:“CNS”
Brain
Brain• The body’s control
center.• Receives messages
from and sends messages to all organs and tissues of the body.
• It controls both voluntary and involuntary activities.
• A mass of billions of neurons.
• These neurons are surrounded by cells called glia, or glial cells, which support (hold the neurons in place) and supply them with nutrients.
Usual pattern of gray/white in CNS
• White exterior to gray• Gray surrounds hollow
central cavity• Two regions with additional
gray called “cortex”– Cerebrum: “cerebral
cortex”– Cerebellum: “cerebellar
cortex”
_________________
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Gray and White Matter
• Gray Matter is in the innermost layer– External and outer
portion of the Cerebrum is Cortex
– Cerebrum and cerebellum have
• Inner gray: “brain nuclei” (not cell nuclei)– Clusters of cell bodies
Remember, in PNS clusters of cell bodies were called “ganglia” More words: brains stem is caudal (toward tail)
to the more rostral (noseward) cerebrum
Major Parts of the Adult Brain
• Cerebrum• Diencephalon• Brainstem• Cerebellum
• Cerebrum– It is the
largest part of the brain.
– It is the seat of human intelligence.
Cerebral cortex• Executive functioning capability• Gray matter: of neuron cell bodies, dendrites,
short unmyelinated axons– 100 billion neurons with average of 10,000 contacts
each• No fiber tracts (would be white)• 2-4 mm thick (about 1/8 inch)• Brodmann areas (historical: 52 structurally
different areas given #s)• Neuroimaging: functional organization
(example later)
Cerebral cortex• All the neurons are interneurons
– By definition confined to the CNS– They have to synapse somewhere before the
info passes to the peripheral nerves• Three kinds of functional areas
– Motor areas: movement– Sensory areas: perception– Association areas: integrate diverse
information to enable purposeful action
Cerebral hemispheres: note lobes
divides frontal from
parietal lobes
Divided the lobes into right & left sides
Each half of the cerebrum deals with the opposite side of the body:•The left half of the cerebrum controls the right side of the body.•The right half of the cerebrum controls the left side of the body.
Note the lobes, fissures and sulci.
Speech Speech andand movement movement
Taste and Taste and touchtouch
Hearing and smellHearing and smellSight Sight
Ventricles
• Central cavities expanded• Filled with CSF (cerebrospinal fluid)• Lined by ependymal cells (these cells
lining the choroid plexus make the CSF: see later slides)
• Continuous with each other and central canal of spinal cord
In the following slides, the ventricles are the parts colored blue
• Lateral ventricles– Paired, horseshoe shape– In cerebral hemispheres– Anterior are close, separated only by thin
Septum pellucidum
12
• Third ventricle– In diencephalon– Connections
• Interventricular foramen• Cerebral aqueduct
3
• Fourth ventricle– In the brainstem– Dorsal to pons and top of medulla– Holes connect it with subarachnoid space
4
Subarachnoid space
• Aqua blue in this pic• Under thick
coverings of brain• Filled with CSF also• Red: choroid plexus
(more later)
________
Surface anatomy • Gyri (plural of
gyrus)– Elevated ridges– Entire surface
• Grooves separate gyri– A sulcus is a
shallow groove (plural, sulci)
– Deeper grooves are fissures
Lateral sulcus
Parieto-occipital sulcus
Transverse cerebral fissure
• Smell (olfactory sense): uncus– Deep in temporal lobe along medial surface
• fMRI: functional magnetic resonance imaging
• Cerebral cortex of person speaking & hearing
• Activity (blood flow) in posterior frontal and superior temporal lobes respectively
Motor areas Anterior to central sulcus
• Primary motor area– Precentral gyrus of
frontal lobe (4)– Conscious or
voluntary movement of skeletal muscles
• Primary motor area continued– Precentral gyrus of frontal lobe– Precise, conscious or voluntary movement of
skeletal muscles– Large neurons called pyramidal cells– Their axons: form massive pyramidal or
corticospinal tracts • Decend through brain stem and spinal cord• Cross to contralateral (the other) side in brainstem• Therefore: right side of the brain controls the left
side of the body, and the left side of the brain controls the right side of the body
Motor areas – continued• Broca’s area (44): specialized motor
speech area – Base of precentral gyrus just above lateral sulcus
in only one hemisphere, usually left– Word articulation: the movements necessary for
speech– Damage: can understand but can’t speak; or if can
still speak, words are right but difficult to understand
Motor areas – continued• Premotor cortex (6): complex movements
asociated with highly processed sensory info; also planning of movements
• Frontal eye fields (inferior 8): voluntary movements of eyes
Homunculus – “little man”• Body map: human body spatially represented
– Where on cortex; upside down
Association Areas
Remember…• Three kinds of functional areas
(cerebrum)1. Motor areas: movement2. Sensory areas: perception
3. Association areas: everything else
Association Areas
• Tie together different kinds of sensory input
• Associate new input with memories• Is to be renamed “higher-order
processing“ areas
Prefrontal cortex: cognition
Executive functioninge.g. multiple step problem solving
requiring temporary storage of info (working memory)
This area is remodeled during adolescence until the age of 25 and is very important for well-being; it coordinates the brain/body and inter-personal world as a whole
Social skillsAppreciating humorConscienceMoodMental flexibilityEmpathy
IntellectAbstract ideasJudgmentPersonalityImpulse controlPersistenceComplex ReasoningLong-term planning
Wernicke’s area
– Junction of parietal and temporal lobes
– One hemisphere only, usually left– (Outlined by dashes)– Pathology: comprehension
impaired for written and spoken language: output fluent and voluminous but incoherent(words understandablebut don’t make sense; as opposed to theopposite with Broca’sarea)
Region involved in recognizing and understanding spoken words
Basal ganglia• Cooperate with cerebral cortex in controlling
movements• Communicate with cerebral cortex, receive input
from cortical areas, send most of output back to motor cortex through thalamus
• Involved with stopping/starting & intensity of movements
Transverse section
• Internal capsule passes between diencephalon and basal ganglia to give them a striped appearance– Caudate and lentiform sometimes called
corpus striatum because of this
Basal ganglia• Cooperate with cerebral cortex in controlling
movements• Communicate with cerebral cortex, receive input
from cortical areas, send most of output back to motor cortex through thalamus
• Involved with stopping/starting & intensity of movements
• “Dyskinesias” – “bad movements”– Parkinson’s disease: loss of inhibition from substantia
nigra of midbrain – everything slows down– Huntington disease: overstimulation
(“choreoathetosis”) – degeneration of corpus striatum which inhibits; eventual degeneration of cerebral cortex (AD; genetic test available)
– Extrapyramidal drug side effects: “tardive dyskinesia”• Can be irreversible; haloperidol, thorazine and similar drugs
Basal ganglia• Note relationship of basal ganglia to
thalamus and ventricles
Transverse section again
Diencephalon (part of forebrain)Contains dozens of nuclei of gray matter
• Thalamus• Hypothalamus• Epithalamus (mainly pineal)
Thalamus (egg shaped; means inner room)
Coronal section
Hypothalamus
Coronal section
Diencephalon – surface anatomyHypothalamus is between optic chiasma to and including
mamillary bodies
• Olfactory bulbs• Olfactory tracts• Optic nerves• Optic chiasma
(partial cross over)• Optic tracts• Mammillary bodies
(looking at brain from below)
Diencephalon – surface anatomyHypothalamus is between optic chiasma to and including
mamillary bodies
(from Ch 14: cranial nerve diagram)
Hypothalamus• “Below thalamus”• Main visceral control center
– Autonomic nervous system (peripheral motor neurons controlling smooth and cardiac muscle and gland secretions): heart rate, blood pressure, gastrointestinal tract, sweat and salivary glands, etc.
– Emotional responses (pleasure, rage, sex drive, fear)– Body temp, hunger, thirst sensations– Some behaviors– Regulation of sleep-wake centers: circadian rhythm
(receives info on light/dark cycles from optic nerve)– Control of endocrine system through pituitary gland– Involved, with other sites, in formation of memory
Hypothalamus(one example of its functioning)
Control of endocrine system through pituitary gland
Epithalamus• Third and most dorsal part of diencephalon• Part of roof of 3rd ventricle• Pineal gland or body (unpaired): produces melatonin
signaling nighttime sleep• Also a tiny group of nuclei
Coronal section
Brain Stem
• Midbrain• Pons• Medulla
oblongata
__Cerebral peduncles____Contain pyramidal motor tracts
Corpora quadrigemina:
XVisual reflexesXAuditory reflexes
Midbrain
______Substantia nigra(degeneration causes Parkingson’s disease)
_______Periaqueductal gray (flight/flight; nausea with visceral pain; some cranial nerve nuclei)
__Middle cerebellar peduncles_
Pons
3 cerebellar peduncles__
Also contains several CN and other nuclei
(one to each of the three parts of the brain stem)
Dorsal view
Medulla oblongata
Dorsal view
_______Pyramids
____pyramidal decussation
With all the labels….
Brain Stem in mid-sagittal planeNote cerebral aqueduct and fourth ventricle*
*
*
Cerebellum Separated from brain stem by 4th ventricle
Functions of cerebellum• Smoothes, coordinates & fine
tunes bodily movements• Helps maintain body posture• Helps maintain equilibrium• Also some role in cognition• Damage: ataxia, incoordination,
wide-based gait, overshooting, proprioception problems
Functions of cerebellum• How?
– Gets info from cerebrum re: movements being planned
– Gets info from inner ear re: equilibrium
– Gets info from proprioceptors (sensory receptors informing where the parts of the body actually are)
– Using feedback, adjustments are made
Functional brain systems(as opposed to anatomical ones)
Networks of distant neurons that function together
Limbic system
Reticular formation
Limbic system (not a discrete structure - includes many brain areas)
Limbic system continued
• Called the “emotional” brain• Is essential for flexible, stable, adaptive
functioning• Necessary for emotional balance, adaptation to
environmental demands (including fearful situations, etc.), for creating meaningful connections with others (e.g. ability to interpret facial expressions and respond appropriately), and more…
Reticular formationRuns through central core of medulla, pons and midbrain
• Reticular activatingsystem (RAS): keeps the cerebral cortex alert and conscious
• Some motor control
Brain protection
1. Skull2. Meninges3. Cerebrospinal
fluid4. Blood brain
barrier
The Skull• The brain is contained
in the rigid skull, which protects it from injury.
• The major bones of the skull are the frontal, temporal, parietal, and occipital bones.
• These bones join at the suture lines
Meninges - DAP1. Dura mater:
2 layers of fibrous connective tissue, fused except for dural sinuses
– Periosteal layer attached to bone– Meningeal layer - proper brain
covering2. Arachnoid mater3. Pia mater
Note superiorsagittal sinus
Dura mater - dural partitionsSubdivide cranial cavity & limit movement of brain
• Falx cerebri– In longitudinal fissure; attaches to crista
galli of ethmoid bone• Falx cerebelli
– Runs vertically along vermis of cerebellum
• Tentorium cerebelli– Sheet in transverse fissure between
cerebrum & cerebellum
• Arachnoid mater– Between dura and arachnoid:
subdural space– Dura and arachnoid cover brain
loosely– Deep to arachnoid is subarachnoid
space• Filled with CSF• Lots of vessels run through (susceptible to
tearing)– Superiorly, forms arachnoid villi: CSF
valves• Allow draining into dural blood sinuses
• Pia mater– The Inner most
membrane, thin, transparent layer, that hugs the brain following convolutions
Cerebral Circulation
• Brain arteriesBrain arteries–Two Internal Two Internal
carotid Arteriescarotid Arteries–Two Vertebral Two Vertebral
ArteriesArteries
Brain arteries Brain arteries
Circle of Willis
Blood-Brain Barrier
• Tight junctions between endothelial cells of brain capillaries, instead of the usual permeability
• Highly selective transport mechanisms• Allows nutrients, O2, CO2• Not a barrier against uncharged and lipid
soluble molecules; allows alcohol, nicotine, and some drugs including anesthetics
Cerebrospinal Fluid CSF
• Made in choroid plexuses (roofs of ventricles)– Filtration of plasma from
capillaries through ependymal cells (electrolytes, glucose)
• 500 ml/d; total volume 100-160 ml (1/2 c)
• Cushions and nourishes brain• Assayed in diagnosing
meningitis, bleeds, MS
CSF circulation: through ventricles, median and lateral apertures, subarachnoid space, arachnoid villi, and into the blood of the superior sagittal sinus
CSF:-Made in choroid plexus-Drained through arachnoid villus
• Hydrocephalus: excessive accumulation
Brain, sagittal sec, medial view
1. Cerebral hemisphere
2. Corpus callosum 3. Thalamus 4. Midbrain 5. Pons 6. Cerebellum 7. Medulla
oblongata
Pons & cerebellum, sagittal section, medial view
1. Midbrain 2. Cerebellum 3. Pons 4. Medulla oblongata 5. Inferior colliculus 6. Superior
medullary velum 7. Fourth ventricle
You don’t need to know #s 5 & 6)
The Spinal Cord
Central Nervous System
Spinal CordSpinal Cord Extends from the
medulla oblongata to the region of T12
Below T12 is the cauda equina (a collection of spinal nerves)
Enlargements occur in the cervical and lumbar regions
Spinal Cord AnatomySpinal Cord Anatomy Central canal filled with cerebrospinal
fluid
Figure 7.19
Spinal Cord
• It is the link between the peripheral nervous system and the brain.
• Functions1. Sensory and motor innervation of entire
body inferior to the head through the spinal nerves
2. Two-way conduction pathway between the body and the brain
3. Major center for reflexes
East Coast Physical Therapy 123
What is a reflex?
East Coast Physical Therapy 124
Stretch reflex
The Reflex ArcThe Reflex Arc
Reflex – rapid, predictable, and involuntary responses to stimuli
Reflex arc – direct route from a sensory neuron, to an interneuron, to an effector
Simple Reflex ArcSimple Reflex Arc
Slide 7.24
East Coast Physical Therapy 127
The Withdrawal Reflex
• Previously known as the Flexor Reflex
• Involves multiple levels and synapses1.Painful stimulus detected2.Ipsilateral extensors inhibited3.Ipsilateral flexors excited4.Limb is withdrawn5. Contralateral extensors excited
East Coast Physical Therapy
The Startle Reflex•Known as the Moro Reflex in infants• Is associated with withdrawal in the pain reflex•Frequently involved in PTSD as a hyper-arousalresponse to stimuli• Likely to upregulate the ANS
Types of Reflexes Types of Reflexes and Regulationand Regulation Autonomic reflexes
Somatic reflexes
Components of the Spinal Cord• H” shaped on cross section• Dorsal half of “H”: cell
bodies of interneurons• Ventral half of “H”: cell
bodies of motor neurons• No cortex (as in brain)
Hollow central cavity (“central canal”)
• Gray matter surrounds cavity
• White matter surrounds gray matter.
Dorsal (posterior)
white
gray
Ventral (anterior)
Central canal______
Spinal cord anatomy• Gray commissure with central canal• Columns of gray running the length of the spinal
cord– Anterior (ventral) horns (cell bodies of motor neurons)
– Posterior (dorsal) horns (cell bodies of interneurons)
• Lateral horns in thoracic and superior lumbar cord
**
**
Spinal Cord Organization
Gray matter of the Spinal Cord• Gray Matter is
consisting mostly of cell bodies of neurons under myelinated nerve fibers.
• Occurs in the Cortex of the brain, basal ganglia, and Central portion of H-shaped in the spinal cord.
gray
White matter of the spinal cord(myelinated and unmyelinated axons)
• Ascending fibers: sensory information from sensory neurons of body up to brain
• Descending fibers: motor instructions from brain to spinal cord– Stimulates contraction of
body’s muscles– Stimumulates secretion
from body’s glands
Major fiber tracts in white matter of spinal cord
Damage: to motor areas – paralysis to sensory areas - paresthesias
sensorymotor
Major ascending pathways for the somatic senses
2 Spinocerebellar tract: proprioception from skeletal muscles to cerebellum of same side (don’t cross)
2 Dorsal column: discriminative touch sensation through thalamus to somatosensory cortex (cross in medulla)
2 Spinothalamic tract: carries nondiscriminate sensations (pain, temp, pressure) through the thalamus to the primary somatosensory cortex (cross in spinal cord before ascending)
(thousands of nerve fibers in each)
Descending Tractsa) Pyramidal tracts: • Lateral corticospinal – cross
in pyramids of medulla; voluntary motor to limb muscles
Ventral (anterior) • 2- corticospinal – cross at
spinal cord; voluntary to axial muscles
b) The Rubrospinal/ Reticulospinal Tract (An Extrapyramidal Tract): conduct impulses which involved the involuntary muscle movement
Protection:3 meninges:• dura mater (outer) arachnoid mater (middle)• pia mater (inner)3 potential spaces epidural: outside dur subdural: between dura & arachnoid subarachnoid: deep to arachnoid
• Dura mater• Arachnoid mater• Pia mater
Spinal cord coverings and spaces
http://www.eorthopod.com/images/ContentImages/pm/pm_general_esi/pmp_general_esi_epidural_space.jpg
• The bones of the vertebral column surround and protect the spinal cord and normally consist of:– 7 cervical, – 12 thoracic,– 5 lumber vertebrae, – 5 sacrum (a fused mass
of five vertebrae), and terminate in the coccyx.
Vertebral Column
Vertebral Column• Nerve roots exit from the
vertebral column through the intervertebral foramina (openings).
• The arch is composed of two pedicles and two laminae supporting seven processes.
• The vertebral body, arch, pedicles, and laminae all encase the vertebral canal.
Reminders ….• Enhancement Hours: 8 hours• Enhancement Time: 8 am – 4pm• Break Time:
– Am: 10: 00 – 10: 15 – Pm: 3:00 – 3:15 pm
• Enhancement Topics:– Peripheral Nervous System Review– Nenrological Assessment– Diagnostic Tests and Nursing Responsibilities– Nursing Pharmacology– Pain, Temperature, and Sensory Function
•
Enhancement Diagnostic Test
NeuroAnatomy and Physiology
1. Which of the following is true regarding Broca’s area?A. Responsible for receptive speechB. Responsible for motor speechC. Results in the inability to hearD. Is often found in the right cerebral
hemisphere
2. Which of the following is a cellular structure that selectively inhibits substances from entering the brain?A. Circle of WillisB. Vertebral arteryC. Blood-brain barrierD. Nucleus pulposus
3. Which of the following is not part of the peripheral nervous system?A. BrainB. Somatic nervous systemC. Afferent pathwaysD. Cranial nerves
4. Which of the following is true regarding the cerebellum?A. Makes up fibers of the corticospinal tractB. Maintains balance or postureC. Controls respirationD. Location of cranial nerves V through VIII
5. Which of the following is a function of the thalamus?A. Major integrating center for afferent
impulseB. Maintenance of internal environmentC. Voluntary visuomotor movementsD. Movements of the auditory system
6. Which of the following is responsible for structural support within a cell?A. Nissl substanceB. DendritesC. MicrofilamentsD. Microtubules
7. A patient experiences a brain injury and the medulla oblongata is affected. Which of the following would you least expect to occur due to this injury?A. Alterations in heart rateB. Alterations in respirationsC. Alterations in blood pressureD. Alterations in balance and posture
8. If a male client experienced a cerebrovascular accident (CVA) that damaged the hypothalamus, the nurse would anticipate that the client has problems with:
A. body temperature control. B. balance and equilibrium. C. visual acuity.D. thinking and reasoning.
Central Nervous System (CNS)
Brain Spinal Cord
Peripheral Nervous System (PNS)
Sensory Neurons
Motor Neurons
Somatic Nervous System• voluntary movements
via skeletal muscles
Autonomic Nervous System
• organs, smooth muscles
Sympathetic- “Fight-or-Flight”
Parasympathetic - maintenance
The Nervous System
The Peripheral Nervous System
• the cranial nerves,
• The spinal nerves,
• the autonomic nervous system.
CRANIAL NERVES
12 Nerves of Cranial
Spinal nerves
• 31 pairs attached through dorsal and ventral nerve roots
• Lie in intervertebral foramina
Ventral Root Ganglion
Dorsal Root Ganglion
Division of 31 Spinal Nerves based on vertebral locations
• 8 cervical• 12 thoracic• 5 lumbar• 5 sacral• 1 coccygeal• Cauda equina
(“horse’s tail”)
pain, temperature, touch, and position sense from the tendons, joints, and body surfaces; or visceral
From Spinal Cord
To the Body
Overview of Nervous System
Copyright © 2007, 2006, 2001, 1994 by Mosby, Inc., an affiliate of Elsevier Inc.
Peripheral Nervous System: AUTONOMIC NERVOUS SYSTEM
• Main function is to maintain internal homeostasis.• Two subdivisions of ANS:
– The sympathetic system (activated by stress, prepares body for “fight or flight” response).
– The parasympathetic system (conserves, restores, and maintains vital body functions, slowing heart rate, increasing gastrointestinal activity, and activating bowel and bladder evacuation).
Divisions of the autonomic nervous system
The Autonomic Nervous System• Has two neurons in a series extending
between the centers in the CNS and the organs innervated.
• The first neuron, the preganglionic neuron, is located in the brain or spinal cord, and its axon extends to the autonomic ganglia.
• There, it synapses with the second neuron, the postganglionic neuron, located in the autonomic ganglia, and its axon synapses with the target tissue and innervates the effector organ.
Fig. 11.40 – ANS preganglionic parasympathetic fibers arise from the brain and sacral region of the spinal cord.
Craniosacral division,
75%
Parasympathetic Responses
Sympathetic Division of Motor NervesTHORACOLUMBAR DIVISION
Neurotransmitters• Acetylcholine functions to maintain
HOMEOSTASIS.
• Preganglionic fibers are cholinergic and secrete acetylcholine:
• Postganglionic parasympathetic and sympathetic fibers of sweat glands are also cholinergic.
• Norepinephrine and epinephrine function to respond to STRESS
• All other postganglionic sympathetic fibers are adrenergic and secrete norepinephrine
Neurotransmitter Receptors• Acetylcholine binds to two cholinergic
receptors:– muscarinic receptors: effector cells at
parasympathetic postganglionic terminals – VISCERAL
– nicotinic receptors: synapses between pre- and postganglionic fibers and at neuromuscular junctions of skeletal muscles - SOMATIC
• Epinephrine and norepinephrine bind to two adrenergic receptors:- alpha and beta receptors, which give different responses at the target organ
Increased blood pressure
Increased peripheral resistance
Vasoconstriction
Contraction of arteriolar
smooth muscles
Increased strength of
contraction of heart
Release of epinephrine and norepinephrine
Sympathetic activation
Adrenal medulla activation
Increased blood sugar
Increased lactic acid
Release of free fatty acids
Glycogenolysis in the liver
Glycolysis in muscle
Peripheral vasoconstriction
Stimulation of receptors of
muscle vasculature
Stimulation of receptors of bronchiole vasculature
Metabolic effects
Sympathetic activation
Increased venous return
Shifts cardiac output to muscles
Increased cardiac output
Vasodilation
Increased blood flow to
muscles
Increased bronchodilation
Increased oxygenation
Increased release of epinephrine
Breakdown of adipose tissue
SYMPATHETIC RESPONSES
Comparison of Somatic and Autonomic Comparison of Somatic and Autonomic Nervous SystemsNervous Systems