Anatomy and Physiology of Neurosensory

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

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”

_________________

____________________________

_____________________________

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?


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


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

http://upload.wikimedia.org/wikipedia/en/8/87/Moro.jpg

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

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

Anatomy and Physiology of Neurosensory

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