Nervous Sys Review Flashcards by Julie T

Sensory input
integration
motor output

functions of the nervous system

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Info gathered by sensory receptors about internal and external changes

sensory input

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interpretation of sensory input

integration

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activation of effector organs (muscles and glands) produces a response

motor output

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this system includes: brain and spinal cord, integration and command center

Central Nervous System

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paired spinal and cranial nerves carrying msgs to and from the CNS

PNS : peripheral nervous system

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sensory_(afferent) division

Somatic afferent fibers—convey impulses from skin, skeletal muscles, and joints
Visceral afferent fibers—convey impulses from visceral organs

motor_(efferent) division
* Transmits impulses from the CNS to effector organs

2 functional divisions of the PNS

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Somatic (voluntary ) nervous system
* Conscious control of skeletal muscles
Autonomic (_involuntary ) nervous system (ANS)

Visceral motor nerve fibers
Regulates smooth muscle , cardiac muscle, and glands
Two functional subdivisions
- sympathetic
- parasympathetic

motor divison of PNS

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neurons- excitable cells that transmit signals
neuroglia- supporting cells

astrocytes (CNS)
microglia (cNS)
ependymal (CNS)
oligodendrocytes(CNS)
satellite cells (PNS)
schwann cells (PNS)

2 principal cell types

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Most abundant , versatile , and highly branched glial cells
Cling to neurons , synaptic endings, and capillaries
Support and brace neurons
Help determine capillary permeability
Guide migration of young neurons
Control the chemical environment
Participate in information processing in the brain

astrocytes

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Small, ovoid cells with thorny processes
Migrate toward injured neurons
Phagocytize microorganisms and neuronal debris

microglia

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Range in shape from squamous to columnar **
May be ciliated
Line the central cavities of the brain and spinal column
Separate the CNS interstitial fluid from the cerebrospinal fluid in the cavities

ependymal cells

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Branched cells
processes wrap CNS nerve fibers, forming insulating myelin sheaths

oligodendrocytes

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surround neuron cell bodies in the PNS

satellite cells

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Surround peripheral nerve fibers and form myelin sheaths
Vital to regeneration of damaged peripheral nerve fibers

schwann cells (neurolemmocytes)

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Electrical signaling
Cell-to-cell interactions during development

plasma membrane functions of neurons

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biosynthetic center of a neuron
Spherical nucleus with nucleolus
Well-developed golgi_ apparatus
rough ER called nissl bodies (chromatophilic substance)
axon hillock
clusters of cell bodies are called nuclei in the CNS, ganglia in the Pns

cell body (soma)

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cone shaped area from which axon arises

axon hillock

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tracts in the CNS
nerves in the CNS

these are bundles of processes

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Short, tapering, and diffusely branched
receptive(input) region of a neuron
Convey electrical signals toward the cell body as graded potentials

dendrites

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long axon - nerve fibers
occasional branches -axon callaterals
numerous terminal branches - telodendria
knoblike axon terminals - synaptic knobs or boutons
- secretory region of neuron
- release neurotransmitters to excite or inhibit other cells

the axon

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conducting region of neuron
generates and transmits nerve iimpulses(action potentials) away from the cell body

axons functions

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molecules and organells are moved along axons by motor molecules in 2 directions :

anterograde- toward axonal terminal
- ex.mitochondria, membrane components, enzymes
retrograde- toward cell body
- ex. organelles to be degraded, signal molecules, viruses, adn bacterial toxins

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segmented protien lipoid sheath around most long diameter axons functioning to

protect/insulate the axon
increase speed of nerve impulse transmission

myelin sheath

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peripheral bulge of Schwann cell cytoplasm

neurilemma

* myellin sheath gaps between adjacent Schwann cells * Sites where axon collaterals can emerge

nodes of ranvier

* Formed by processes of oligodendrocytes , not the whole cells * Nodes of ranvier are present * No neurilemma * Thinnest fibers are unmyelinated

myelin sheaths in CNS

* schwann cells * neurilemma * nodes of ranvier

myelin sheaths in PNS

Dense collections of myelinated fibers

white matter

Mostly neuron cell bodies and unmyelinated fibers

gray matter

3 types of structural classifcation of neurons

1. multipolar 2. bipolar 3. unipolar (pseudounipolar)

* 1 axon and several dendrites * most abundant * motor neurons and interneurons

multipolar neuron

* 1 axon and 1 dendrite * rare retinal neurons

bipolar neurons

* single, short process that has two branches: * peripheral process—more distal branch, often associated with a sensory receptor * Central process—branch entering the CNS

unipolar (pseudounipolar)

1. sensory (afferent) -transmits impulses from sensory receptors toward the CNS 2. motor(efferent)- carry impulses from the CNS to effectors 3. interneurous(association)- shuttle signals thru CNS pathways

functional classifications of neurons

* NUERONS are highly irritable * Respond to adequate stimulus by generating an action potential (nerve impulse; traveling action potential) * Impulse is always the same REGARDLESS of stimulus

neuron function

Proteins serve as membrane ion channels Two main types of ion channels: 1. leakage(nongated) channels—always open 2. Gated channels (three types): * Chemically gated (ligand-gated) channels—open with binding of a specific neurotransmitter * Voltage-gated channels—open and close in response to changes in membrane potential * Mechanically gated channels—open and close in response to physical deformation of receptors

role of membrane ion channels

\_\_\_\_\_\_ \_\_\_\_\_\_\_changes when: * Concentrations of ions across the membrane change * Permeability of membrane to ions changes

membrane potential

changes in emmebrane potential are signals used to receive, integrate, and send info * 2 types of signals are:

1. graded potentials -incoming short distance signals 2. action potentials- long distance signals of axons

\_\_\_\_ \_\_\_\_are classified according to: * Diameter * Degree of myelination * speed of conduction

nerve fibers

Group _____ fibers Large diameter, myelinated somatic sensory and motor fibers Group ____ fibers Intermediate diameter, lightly myelinated ANS fibers Group ____ fibers Smallest diameter,unmyelinated ANS fibers

A, B, C

a junction that mediates info transfer from one neuron to another or to an effector cell * presynaptic neuron—conducts impulses toward the synapse * postsynaptic neuron—transmits impulses away from the synapse

the synapse

* Axodendritic—between the axon of one neuron and the dendrite of another * Axosomatic—between the axo\_ of one neuron and the soma of another Less common types: * axoaxonic(axon to axon) * Dendrodendritic (dendrite to dendrite) * dendrosomatic\_(dendrite to soma)

types of synapses

electrical synapses are less cmmon than chemical * neurons are electrically couple joined by gap junctions * communication is very rapid whetierh uni/bidirectional * important in embryonic nervous tissue and some brain regions chemical synapses sepcialized for release and reception of neurotransmitters and composed of * presnpatic terminal of the presynaptic neurons containing synatpic vesicles * postsynaptic region on the postynaptic neuron

difference between electrical and chemical synapses

* fluid filled space separating the presynaptic and postysynaptic neurons * prevents nerve impulses from direectly passing form 1 neuron to the next

synaptic cleft

\_\_\_\_\_\_\_\_ \_\_\_\_\_\_ is terminated by * degradation by enzymes * reuptake by astrocytes or axon terminal * Diffusion away from the synaptic cleft

neurotransmitter effect

The rate-limiting step of neural transmission--neurotransmitter must be released, diffuse across the synapse, and bind to receptors (0.3-5.0ms)

synaptic delay

* Most neurons make two or more neurotransmitters, which are released at different stimulation frequencies * 50 or more neurotransmitters have been identified * Classified by chemical structure and by function

neurotransmitters

* Released at neuromuscular junctions and some ANS neurons * Synthesized by enzyme choline acetyaltransferase * degraded by the enzyme acetylcholinesterase (AChE)

acetycholine

* 3 to 40 amino acids * Present in CNS and PNS; some function as hormones * Excitatory and inhibitory; depending on receptor * enkphalins, endorphins, dynorphins , substance P * opioid peptides= thought to be natural painkillers

neuropeptides

\_\_\_ ____ \_\_\_\_ systems are known to play an important role in motivation , emotion, attachment behavior , response to stress and pain , and the control of food intake.

brain opioid peptide

* Catecholamines * Dopamine, norepinephrine (NE), and epinephrine * indolamines * Serotonin and histamine * Broadly distributed in the brain * Play roles in emotional behaviors and the biological clock

biogenic amines include:

* GABA—Gamma ()-aminobutyric acid * glycine * aspartate * Glutamate

amino acids

* substance P * Mediator of pain signals * endorphins * Act as natural opiates ; reduce pain perception * Gut-brain peptides * Somatostatin and cholecystokinin

peptides (neuropeptides)

* Act in both the CNS and PNS * produce fast or slow responses * induce Ca2+ influx in astrocytes * Provoke pain sensation

purines such as ATP

* nitric oxide (NO) * Synthesized on demand * activates the intracellular receptor guanylyl cyclase to cyclic GMP * Involved in learning and memory * carbon\_ monoxide (CO) is a regulator of cGMP in the brain

gases and lipids

* lipid soluble; synthesized on demand from membrane lipids * Bind with G protein–coupled receptors in the brain * Involved in learning and memory

endocannabinoids

* neurotransmitter effects may be excitatory(depolarizing) and or inhibitory (hyperpolarizing) * determined by receptor type of postsynaptic neuron * gaba and glycine uaually inhibitory

functional classification of neurotransmitters

* Excitatory at neuromuscular junctions in skeletal muscle * Inhibitory in cardiac muscle

acetylcholine

1. action potential arrives at axon terminal 2. voltagegated Ca channels opena dn Ca enters the axon terminal 3. Ca entry causes synaptic vesicles to release neurotransmitter by exocytosis 4. neurotransmitter diffuses across teh synaptic cleft and binds to specific receptors on the postsynaptic membrane 5. binding of neurtransmitter opens ion channels resultin graded potentials 6. neurotramitter effects are terminated by reuptake thru transport proteins; enzymatic degradation or diffusion away from the synapse

info transfer across chemical synapses

1. Cerebral hemispheres 2. Diencephalon (epithalamus , thalamus, hypothalamus ) 3. Brain stem (midbrain, pons, and medulla) 4. cerebellum

adult brain regions

* Similar pattern with additional areas of gray matter * Nuclei in cerebellum and cerebrum * Cortex of cerebellum and cerebrum

brain

* central cavity surrounded by a gray matter core * External white white composed of myelinated fiber tracts

spinal cord

* connected to one another and to the central canal of the spinal cord * Lined by ependymal cells * contain cerebralspinal fluid * 2 c shaped lateral ventricles in cerebral hemispheres * 3rd ventricle in diencephalon * 4th ventricle

ventricles in brain

Ridges (gyri), shallow grooves (sulci), and deep grooves (fissures)

surface markings of cerebral hemispheres

Separates the precentral gyrus of the frontal lobe and the postcenral gyrus of the parietal lobe

central sulcus

* 40% of the mass of the brain * Thin (2–4 mm) superficial layer of gray matter * Each hemisphere connects to contrallateral side of the body * Site of conscious mind: awareness, sensory perception, voluntary motor initiation, communication, memory storage, understanding

cerebral cortex

* motor areas—control voluntary movement * sensory areas—conscious awareness of sensation * Association areas—integrate diverse information * conscious behavior involves entire cortex

functional areas of cerebral cortex

* Primary (somatic) motor cortex * Premotor cortex * Broca’s area * frontal eye field

motor areas of cerebral cortex

* Large pyramidal cells of the precentral gyri * Long axons -\> pyramidal (corticospinal) tracts * Allows conscious control of precise, skilled , voluntary movements * Motor humunculus : upside-down caricatures representing the motor innervation of body regions

primary motor cortex

* In the postcentral gyri * Receives visual information from the skin, skeletal muscles, and joints * Capable of spatial discrimination : identity of body region being stimulated

primary somatosensory cortex

* Primary visual (striate) cortex * Extreme posterior tip of the occipital lobe * Most of it is buried in the calcarine sulcus * Primary visual cortex from the retina

visual areas

* surrounds the primary visual cortex * Uses past visual experience to interpret visual stimuli (e.g., color, form, and movement) * Complex processing involves entire posterior half of the hemisphere

visual association area

gustatory cortex

region involved in percieing taste stimuli located in the insula just deep to the temporal lobe

visceral sensory area

posterior to gustatory cortex ; involved in conscious perception of visceral sensations like full bladder, upset stomach

system of peripheral nerves that regulate cardiac and smooth muscle and secretion by the glands

ANS

\_\_\_\_\_\_ regulates activity by controlling the activity of centers in the brain stem and spinal cord, influencing blood pressure, rate and force of heartbeat, digestive tract motility, eye pupil size, and others

hypothalamus

* Most dorsal portion of the diencephalon; forms roof of the third ventricle * extends from poterior border and visible externally is pineal gland and secretes melatonin a

epithalamus

* Similar structure to spinal cord but contains embedded nuclei * Controls automatic behaviors necessary for survival * Contains fiber tracts connecting higher and lower neural centers * Associated with 10 of the 12 cranial nerves

brain stem

* Forms part of the anterior wall of the fourth ventricle * Fibers of the pons * Connect higher brain centers and the spinal cord * Relay impulses between the motor cortex and the cerebellum * Origin of cranial nerves V (trigeminal ), VI (abducens), and VII (vestibulocochlear ) * Some nuclei of the reticular formation * Nuclei that help maintain normal rhythym of breakting

pons

* Joins spinal cord at foreman magnum * Forms part of the ventral wall of the 4th ventricle * Contains a choroid plexus of the fourth ventricle * Pyramids—two ventral longitudinal ridges formed by pyramidal tracts * Decussation of the pyramids—crossover of the corticospinal tracts * associated with cranial nerves VII, X, XII

medulla oblongata

* autonomic reflex center maintiaing homeostasis * functional groups such as cardiovascular , respiratory centers, and other centers regulating vomiting, hiccuping swallowing, coughing and sneezing

medulla oblongata functions

* 11% of brain mass * Dorsal to the pons and medulla * provides precise timing and appropriate patterns of skeletal muscle contraction * Two hemispheres connected by vermis * Folia—transversely oriented gyri * Arbor vitae—distinctive treelike pattern of the cerebellar white matter

cerebellum

* Cerebellum receives impulses from the cerebral cortex of the intent to initiate voluntary muscle contraction * Signals from proprioceptors and visual and equilibrium pathways continuously “inform” the cerebellum of the body’s position and momentum * Cerebellar cortex calculates the best way to smoothly coordinate a muscle contraction * A “blueprint” of coordinated movement is sent to the cerebral motor cortex and to brain stem nuclei

cerebella processing for motor activity

* Recognizes and predicts sequences of events during complex movements * Plays a role in nonmotor functions such as word association and puzzle solving

cognitive function of the cerebellum

networks of neurons that work together and span wide areas of the brain * limbic system * reticular system

brain systems

* Structures on the medial aspects of cerebral hemispheres and diencephalon * encircles brain stem

limbic system

recognizes angry or fearful facial expressions, assesses danger, and elicits the fear response

amygdala

* Records electrical activity that accompanies brain function * Measures electrical potential differences between various cortical areas

electroencephalogram (EEG)

* Patterns of neuronal electrical activity * Generated by synaptic activity in the cortex * Each person’s brain waves are unique * Can be grouped into four classes based on frequency measured as Hertz (Hz)

brain waves

State of partial unconsciousness from which a person can be aroused by stimulation

sleep

* Cover and protect the CNS * Protect blood vessels and enclose venous sinuses * Contain cerebrospinal fluid (CSF) * form partitions in the skull

meninges

dura mater arachnoid mater pia mater

meninge layers

* strongest meninx * 2 layers of fibrous connective tissue (around the brain) to separate to form venous sinuses

dura mater

* Middle layer with spiderweb like extensions * Separated from the dura mater by the subdural space * subarachnoid space contains CSF and blood vessels * arachnoid villi protrude into the superior sagittal sinus and permit CSF reabsorption

arachnoid mater

fold dippin into the longitudinal fissure btwn the cerebral hemispheres

falx cerebri

small midline partition runnning along the vermis of the cerebellum

falx cerebllii

horizontal dural fold over cerebellum and in the transverse fissure

tentorium cerebelli

Layer of delicate connective tissue that clings tightly to the brain

pia mater

1. choroid plexus of each ventricle produces CSF 2. CSF flows thru the ventricles and into the subarachnoid space via the median and lateral apertures 3. CSF flows thru the subarachnoid space 4. CSF is absorbed into the dural venous sinuses via the arachnoid villi

formation, location and circulation of CSF

* hangs from the roof of each ventricle * clusters of capillaries enclosed by pia mater and a layer of ependymal cells

choroid plexus

\_\_\_\_\_\_\_ is sensory ; as _______ is to motor

ascending; descending

gray commissure encloses the ___ \_\_\_

central canal in spnal cord

ventral horns mainly house cell bodies of somatic mortor neurons that send their axons out to the skeletal muscles via the ventral rootlets that fuse together to become the ___ \_\_\_

ventral roots

afferent fibers carrying impulses from peripheral sensory receptor form the ___ \_\_\_\_ of th espinal cord that fan out as dorsal rootlets

dorsal roots

cell bodies of the associated sensory neurons are found in an enlarged region of the dorsal root called the ___ \_\_\_ \_\_-

dorsal root ganglion

spinal gray matter has the following 4 zones

1. somatic sensory 2. visceral sensory 3. visiceral (autonomic motor) 4. somatic motor

\_\_\_ is assocaited with nerves in the PNS, whereas nuclei are collections of neuron cell bodies in the CNS

ganglia

1. axon becomes fragmented at the injury site 2. macrophages clean out the dead axon distal to the injury 3. axon sprouts or filaments grow thru a regenration tube formed by schwann cells 4. axon regenerates a new myelin sheath forms

regeneration of a nerve fiber in a peripheral nerve

1. olfactory-smell 2. optic-vision 3. oculomotor- eye movement 4. trochlear- innervates extrinsic eye muscle 5. trigeminal- largest, suppulies face and motor fibers to mastication 6. abducens- extrinsic eye muscle abducts eyeball to turn laterally 7. facial- 8. vestbulocochlear- hearing and balance/auditory 9. glossopharyngeal - tongue and pharynx 10. vagus- swalllowing 11. accessory- spinal accessory nerve 12. hypoglossal- under tongue

cranial nerves

* 8 pairs of cervical nerves * 12 pairs of thoracic nerves * 5pairs of lumbar nerves * 5 pair of sacral nerves

spinal nerves

contain motor (efferent)fibers that arise from ventral horn motor neurons and extend to and innervate the skletal muscles

ventral roots

contain sensory (afferent) fibers that arise from sensory neurons in dorsal root ganglia and conduct impulses from peripheral receptors to the spinal cord

dorsal roots

buried deep in the neck under the sternocleidomastoid muscle ; the central rami of the first 4 cervical nerves for the looping ____ \_\_\_\_

cervical plexus

runs inferiorly tru thorax and supplies both motor and sensory fibers to the diaphragm

phrenic nerve of cerviical plexus

situated partly in the neck and partly in the axilla gives rise to virtually all the nerves that innervate the upper limb

brachial plexus

branches off the posterior cord and runs posterior to the surgical neck of the humerous

axillary nerve of brachial plexus

branches of the medial cord of the plexus

ulnar nerve of brachial plexus

arises from spinal nerves and lies within the psoas major muscle

lumbar plexus

largest terminal nerve of lumbar plexus running deep to the inguinal ligament to enter the thigh and then divides into large branches

femoral nerve

enters the medial thigh via the obturator foramen and innervate the adductor muscles

obturator nerve

largest branch of sacral plexus , thickest and longest nerve in body supplying lower limb

sciatic nerve

innervates the muscles and skin of the perineum and helps stimulatre erection and control urination

pudendal nerve

* mobilizes the body during activity; is the “fight-or-flight” system * Promotes adjustments during exercise, or when threatened * blood flow is shunted to skeletal muscles and heart * bronchioles dilate * Liver releases glucose

sympathetic division role of ANS

* Promotes maintenance activities and conserves body energy * Its activity is illustrated in a person who relaxes ,reading, after a meal * blood pressure, heart rate, and respiratory rates are low * gastrointestinal\_ tract activity is high * pupils\_ are constricted and lenses are accommodated for close vision

parasympathetic division of ANS