Anatomy_Concepts_Ch12-15 Flashcards
functions of the nervous system
it uses its millions of sensory receptors to monitor changes occurring both inside and outside the body. each of these changes is called a stimulus, and the gathered information is called sensory input<br></br>it processes and interprets the sensory input and makes decisions about what should be done at each moment, amprocess called integration<br></br>it dictates a response by activating the effector organs, our muscles or glands; the response is called motor output
classification of neurons
structural classification: multipolar neurons, bipolar neurons, unipolar neurons (pseudounipolar neurons)<br></br>functional classification: sensory neurons, motor neurons, interneurons
neuroglia functions
provide a supportive scaffolding for neurons<br></br>cover all nonsynaptic parts of the neurons, thereby insulating the neurons and keeping the electrical activities of adjacent neurons from interfering with each other
neuron/nerve fiber/nerve
a neuron is a nerve cell<br></br>a nerve fiber is a long axon<br></br>a nerve is a collection of axons in the PNS
regeneration of an axon in a peripheral nerve
1) the axon becomes fragmented at the injury site<br></br>2) macrophages clean out the dead axon distal to the injury<br></br>3) axon sprouts, of filaments, grow thorugh a regeneration tube formed by Schwann cells<br></br>4) the axon regenerates, and a new myelin sheath forms
corticle pathway (slower) which follows the spinal pathway works how?
1) parallel processing. simultaneouly, the nerve impulses travel on an axon branch that extends into the white matter. this ascending axon carries the nerve impulses to the brain.<br></br>2) integration in gray matter. multiple interneurons process the nerve impulses to localize the stimulus, identify its source, and plan a resonse. this complex process enables you to feel the pain<br></br>3) voluntary motor response. a nonreflexive motor response is initiated in the gray matter and transmitted down a descending axon in the white matter to stimulate somatic motor neurons
spinal pathway works how?
withdrawal reflex. a painful stimulus triggers nerve impulses in a sensory neuron, which initiate the polysynaptic withdrawal reflex
somatic sensory (SS) sensory components
general: touch, pain, pressure, vibration, temperature, and propreoception from the skin, body wall, and limbs<br></br>special: hearing, equilibrium, and vision
visceral sensory (VS) sensory components
general: stretch, pain, temperature, chemical changes, and irritation in viscera; nausea and hunger<br></br>special: taste and smell
somatic motor (SM) motor components
motor innervation to skeletal muscles
visceral motor (VM; autonomic) motor components
motor innervation to smooth muscle, cardiac muscle, and glands
functional class–neuron type according to direction of impulse conduction: multipolar
most multipolar neurons are interneurons that conduct impulses within the CNS, integrating sesory input or motor output; may be one of a chain of CNS neurons, or a single neuron connecting sensory and motor neurons<br></br>some multipolar neurons are motor neurons that conduct impulses along the efferent pathways from the CNS to an effector (muscle/gland)
functional class–neuron type according to direction of impulse conduction: bipolar
essentially all bipolar neurons are sensory neurons that are locate in some special sense organs. for example, bipolar cells of the retine are involved with the transmission of visual inputs from the eye to the brain (via an intermediate chain of neurons)
functional class–neuron type according to direction of impulse conduction: unipolar (pseudounipolar)
most unipolar neurons are sensory neurons that conduct impulses along afferent pathways to the CNS for interpretation. (these sensory neurons are called primary or first-order sensory neurons)
structural class–neuron type according to the number of precesses extending from the cell body: multipolar
many processes extend from the cell body; all are dendrites except for a single axon
structural class–neuron type according to the number of precesses extending from the cell body: bipolar
two processes extend from the cell body, one is a fused dendrite, the other is an axon
structural class–neuron type according to the number of precesses extending from the cell body: unipolar (pseudounipolar)
one process extends from the cell body and forms central and peripheral processes, which together comprise and axon
relative abundance and location in human body: multipolar
most abundant in body. major neuron type in the CNS
relative abundance and location in human body: bipolar
rare. found in some special sensory organs (olfactory mucosa, eye, ear)
relative abundance and location in human body: unipolar (pseudounipolar)
found mainly in the PNS. common only in dorsal root ganglia of the spinal cord and sensory ganglia of cranial nerves
primary brain vesicles
prosencephalon (forebrain)<br></br>mesencephalon (midbrain)<br></br>phombencephalon (hindbrain)
secondary brain vesicles
presencephalon divides in to the telencephalon (endbrain) and the diencephalon (through-brain)<br></br>mesencephalon remains undivided<br></br>rhombencephalon divides into the metencephalon (afterbrain) and the myelencephalon (brain most like the spinal cord)
telencephalon
develops two lateral swellings that look like large mouse earse . these become the large cerebral hemispheres, together called the cerebrum
diencephalon
develops three main divisions: the thalamus, the hppothalamus, and the epithalamus
mesencephalon
forms the midbrain
metencephalon
ventral part becomes the pons, and the dorsal roof develops into the cerebellum
myelencephalon
forms the medulla oblongata
four parts of the brain
1) brain stem (medulla oblongata, pons, and midbrain)<br></br>2) cerebellum<br></br>3) diencephalon<br></br>4) cerebrum (composed of the two cerebral hemispheres)
functions of the brain stem
it acts as a passageway for all the fiber tracts running between the cerebrum and the spinal cord<br></br>it is heavily involved with the innervation of the face and head; 10 of the 12 pairs of crainal nerves attach to it<br></br>it produces the rigidly programmed, automatic behaviors necessary for survival<br></br>it integrates auditory reflexes and visual reflexes
four pairs of cranial nerves attach to the medulla
vestibulocochlear nerve (crainal nerve VIII)<br></br>glossopharyngeal nerve (cranial nerve IX)<br></br>vagus nerve (cranial nerve X)<br></br>hypoglossal nerve (cranial nerve XII)
brain nuclei in the reticular formation form three columns of gray matter on each side that extend the length of the brain stem
1) the midline raphe nuclei, which are flanked laterally by<br></br>2) the medial nuclear group and then<br></br>3) the lateral nuclear group
“nuclei in the medulla’s reticular formation are involved with visceral activities:”
the cardiac center adjusts the force and rate of the heartbeat<br></br>the vasomotor center regulates blood pressure by stimulating or inhibiting the contraction of smooth muscle in the walls of blood vessels, thereby constricting or dilating the vessels<br></br>the medullary respiratory center controls the basic rhythm and rate of breathing
several cranial nerves attach to the pons
trigeminal (cranial nerve V)<br></br>abducens (crainal nerve VI)<br></br>facial (cranial nerve VII)
each cerebellar hemisphere is subdivided into three lobes:
large anterior and posterior lobes, and the small flocculonodular lobe
information is processed by the cerebellum in the folliwing way:
the cerebellum receives information from the cerebrum on the movements being planned<br></br>the cerebellum compares these planned movements with current body position and movements<br></br>the cerebellum sends instructions back to the cerebral cortex on how to resolve any differences between the intended movements and current position
functions of the hypothalamus
control of the autonomic nervous system<br></br>regulation of body temperature<br></br>regulation of hunger and thirst sensations<br></br>regulation of sleep-wake cycles<br></br>control of the endocrine system<br></br>control of emotional responses<br></br>control of motivational behavior<br></br>forrmation of memory
five major lobes of each cerebral hemisphere:
frontal lobe, parietal lobe, occipital lobe, temporal lobe, insula
information is processed through regions of the cerebral cortex in the following hierarchical manner
- sensory information is received by the primary sensory cortex, and the arrival of this information results in awareness of the sensation<br></br>2. the information is relayed to the sensory association area that gives meaning to the sensory input<br></br>3. the multimodal association areas receive input in parallel from multiple sensory association areas, integrating all of the sensory input to create a complete understanding of the sensory information. these regions also integrate sensory input with past experience and develop a motor response<br></br>4. the motor plan is enacted by the motor cortex
primary somatosensory cortex
receives information from the geeral somatic senses (touch, pressure, vibration, pain, and temperature from the skin and proprieception from the muscles and joints) and enables conscious awareness of these sensations
sensory homunculus
”"”little man””, map of the primary sensory cortex”
contralateral projection
the right cerebral hemisphere receives its sensory input from the left side of the body and the left cerebral hemisphere receives its sensory input from the right side of the body
somatosensory association cortex
lies posterior to and communicates with the primary somatosensory cortex, integrates sensory inputs (touch, pressure, and others) into a comprehensive understand of what is being felt
primary visual cortex
“posterior and medial part of the occipital lobe, much of it buried within the deep carcarine sulcus (““spur-shaped””), receives visual information that originates from the retina of the eye, exhibits contralateral projection”
visual association area
surrounds that primary visual cortex and covers much of the occipital lobe, continues the processing of visual information by analyzing color, form, and movement
primary auditotry cortex
functions in censcious awareness of sound, in relation to loudness, rhythm, and pitch, located on teh superior edge of the temporal lobe, primarily inside the lateral sulcus
auditory association area
lies just posterior and lateral to the primary auditory area, permits the evaluation of a sound
sensory areas
somatosensory areas<br></br>visual areas<br></br>auditory areas<br></br>vistibular (equilibrium) cortex<br></br>gustatory cortex<br></br>olfactory cortex<br></br>visceral sensory area
motor areas (list)
“primary motor cortex<br></br>premotor cortex<br></br>frontal eye field<br></br>Broca’s area”
multimodal association areas (list)
posterior association area<br></br>anterior association area<br></br>limbic association area
basal nuclei (parts)
“caudate ““tail like”” nucleus, putamen ““pod””, globus pallidus ““pale globe”””
meninges (functions)
cover and protect the CNS<br></br>enclose and protect the blood vessels that supply the CNS<br></br>contain the cerebrospinal fluid
meninges (list)
from external to internal: dura mater, arachnoid mater, and pia mater
cerebrospinal fluid (functions)
CSF provides a liquid medium that surrounds and gives buoyancy to the CNS. the brain and spinal cord actually float in the CSF, which prevents these delicate organs from being crushed under their own weight.<br></br>the layer of CSF surrounding the CNS resists compressive forces and cusions the brain and spinal cord from blows and jolts.<br></br>CSF helps to nourish the brain, to remove wastse produced by neurons, and to carry chemical signals such as hormones between different parts of the central nervous system. although similar in composition to the blood plasma from which it arises, CSF contains more sodium and chloride ions and less protein.
CSF circulation
1) CSF is produced by the choroid plexus of each ventricle<br></br>2) CSF flows through the ventricles and into the subarachnoid space via the median and lateral apertures. Some CSF flows through the central canal of the spinal cord.<br></br>3) CSF flows through the subarachnoid space<br></br>4) CSF is absorbed into the dural venous sinuses via the arachnoid granulations
spinal cord (functions)
1) through the spinal nerves that attach to it, the spinal cord is involved in the sensory and motor innervation of the entire body inferior to the head.<br></br>2) through the ascending and descending tracts traveling within its white matter, the spinal cord provides a two-way conduction pathway for signals between the body and the brain.<br></br>3) through sensory and motor integration in its gray matter, the spinal cord is a major center for reflexes.
three funiculi
”"”long ropes””: dorsal (posterior) funiculus, ventral (anterior) funiculus, and lateral funiculus”
four zones of spinal cord gray matter
somatic sensory (SS), visceral sensory (VS), visceral motor (VM), and somatic motor (SM)
features of the ascending and descending pathways:
most pathways cross from one side of the CNS to the other, or decussate, at some point along their course<br></br>most pathways consist of a chain of two or three serially linked neurons that contribute to successive tracts along a given pathway<br></br>most pathways are spatially arranged in a specific way, according to the body region they supply. for example, in one ascending tract, the axons transmitting impulses from the superior parts of the body lie lateral to the axons carrying impulses from the inferior body parts<br></br>all pathways are bilaterally symetrical, occuring on both the right and left side of the brain or spinal cord
three main ascending pathways
spinocerebellar pathway, dorsal column pathway, spinothalamic pathway
In the dorsal column pathway:
the axons of first-order neurons, the sensory neurons, enter the spinal cord and send an axonal branch up one of the dorsal white column tracts, either the medial fasciculus gracilis or the lateral fasciculus cuneatus. these axons ascend in the spinal tract to the medulla oblongata.<br></br>in the medulla oblongata, these axons synapse with second-order neurons in the nucleus gracilis or nucleus cuneatus. axons from these brain nuclei form a tract called the medial lemniscus tract, which decussates in the medulla and then ascends through the pons and midbrain to the thalamus.<br></br>third-order neurons originating in the thalamus send axons to the primary sematosensory cortex on the postcentral gyrus, where the sensory information is processed, resulting in awareness of precisely localized sensations.
In the spiothalamic pathway:
the axons of first-order sensory neurons enter the spinal cord, where they synapse on interneurons in the dorsal gray horn.<br></br>axons of the second-order neurons decussate in the spinal cord, enter the lateral and ventral funicula as the spinothalamic tract, and ascend to the thalamus.<br></br>axons from third-order neurons in the thalamus project to the primary somatosensory cortex on the postcentral gyrus, where the information is processed into the consious sensation. the brain interprets the sensory inforamiton carried by the spinothalamic pathway as unpleasant–pain, burns, cold, and so on.
In the pyramidal tracts:
the axons of pyramidal cells, the upper motor neurons, descend from the cerbral motor cortex through the brain stem to the spinal gray matter–mostly to the ventral horns.<br></br>in the ventral horn, the axons either synapse with short interneurons that activate somatic motor neurons or synapse directly on somatic motor neurons, the lower motor neurons.
indirect motor pathways include:
tectospinal tract (from the superior colliculus, the tectum of the midbrain)<br></br>vestibulospinal tract (from the vestibular nuclei)<br></br>rubrospinal tract (from the red nucleus)<br></br>reticulospinal tract (from the reticular formation)<br></br>these tracts stimulate body movements that are subconscieus, coarse, or postural
classification of receptors
functional classification: according to their location or the type of stimulus they detect<br></br>location of receptors (exteroceptors, interoceptors, proprioceptors)<br></br>stimulus type (mechanoreceptors (e.g. baroreceptor), thermoreceptors, chemoreceptors, photoreceptors, nociceptors)<br></br>structural classification: (free nerve endings) and (encapsulated nerve endings surrounded by a capsule of connective tissue)
main types of encapsulated nerve endings
“tactile (Meissner’s) corpuscles<br></br>lamellar (Pacinian) corpuscles<br></br>bulbous corpuscles (Ruffini endings)<br></br>proprioceptors”
types of joint kenesthetic receptors are present within each joint capsule
lamellar (Pacinian) corpuscles<br></br>bulbous corpuscles (Ruffini endings)<br></br>free nerve endings<br></br>receptors resembling tendon organs
I-XII cranial nerves
I. Olfactory<br></br>II. Optic<br></br>III. Oculomotor<br></br>IV. Trochlear<br></br>V. Trigeminal<br></br>VI. Abducens<br></br>VII. Facial<br></br>VIII. Vestibulocochlear<br></br>IX. Glossopharyngeal<br></br>X. Vagus<br></br>XI. Accessory<br></br>XII. Hypoglossal
components of the brachial plexus, from medial to lateral
Vetral rami. the ventral rami from spinal segments C5-T1 form the roots of the brachial plexus<br></br>Trunks. the ventral rami merge to form three trunks<br></br>Divisions. each trunk splits into two divisions, anterior and posterior<br></br>Cords. these six divisions then converge to form three cords
cerebral cortex function (functional area): frontal lobe
“voluntary movement (primary motor cortex)<br></br>planning movement (premotor cortex)<br></br>eye movement (frontal eye field)<br></br>speech production (Broca’s area)<br></br>executive cognitive functions (anterior association area)<br></br>emotional response (limbic association area)”
cerebral cortex function (functional area): parietal lobe
“general somatic sensation (somatosensory cortex and association area)<br></br>spatial awareness of objects, sounds, body parts (posterior association area)<br></br>understanding speech (Wernicke’s area)”
cerebral cortex function (functional area): occipital lobe
vision (visual cortex and association areas)
cerebral cortex function (functional area): temporal lobe
hearing (auditory cortex and association area)<br></br>smell (olfactory cortex)<br></br>object identification (posterior association area)<br></br>emotional response, memory (limbic association area)
cerebral cortex function (functional area): insula
taste (gustatory cortex)
cerebral white matter function (functional area): commissural fibers
connect the corresponding cortices of the two hemispheres
cerebral white matter function (functional area): association fibers
connect the cortex of the different parts of same hemisphere
cerebral white matter function (functional area): projection fibers
connect the cortex to more caudal parts of the CNS
deep cerebral gray matter function (functional area): basal nuclei (ganglia)
control movements in conjunction with the motor cortex
deep cerebral gray matter function (functional area): basal forebrain nuclei
perform major role in arousal, learning, memory, and motor control; rich in cholinergic fibers
deep cerebral gray matter function (functional area): claustrum
function unclear; may integrate information between the cerebral cortex and the limbic system
brain stem: medulla oblongata
contains project fibers<br></br>site of decussation of the pyramids<br></br>relays ascending sensory pathways transmitting impulses from skin and proprioceptors through nuclei cuneatus and gracilis<br></br>relays sensory information to the cerebellum through inferior olivary nuclei<br></br>contains nuclei of cranial nerves VIII-X and XII<br></br>contains visceral nuclei controlling heart rate, blood vessel diameter, respiratory rate, vomiting, coughing, etc.
brain stem: pons
contains projection fibers<br></br>pontine nuclei relay information from the cerebrum to the cerebellum<br></br>contains nuclei of cranial nerves V-VII<br></br>contains reticular formation nuclei
brain stem: midbrain
contains projection fibers (e.g., cerebral peduncles contain the fibers of the pyramidal tracts)<br></br>contains subcortical motor centers (substantia negra and red nuclei)<br></br>contains nuclei for cranial nerves III and IV<br></br>contains visual (superior colliculi) and auditory (inferior colliculi) reflex centers
brain stem: reticular formation–a functional system
maintains cerebral cortical alertness (reticular activating system)<br></br>filters out repetitive stimuli<br></br>helps regulate skeletal and visceral muscle activity and modulate pain
cerebellum: cerebullum
processes input from cerebral motor cortex, proprioceptors, and visual and equilibrium pathways<br></br>provides output to cerebral motor cortex and subcortical motor centers that result in smooth, coordinated skeletal muscle movements<br></br>resposible for balance and posture
diencephalon: thalamus
relays sensory impulses to cerebral cortex for interpretation<br></br>relays impulses between cerbral cortex and subcortical motor centers, including basal nuclei (ganglia) and cerebellum<br></br>involved in memory processing
diencephalon: hypothalamus
chief inegration center of autonomic (involuntary) nervous system<br></br>regulates body temperature, food intake, water balance, thirst, and biological rythms and drives<br></br>regulates hormonal output of anterior pituitary gland<br></br>acts as an endocrine organ producing posterior pituitary hormones AHD and oxytocin
cerebral hemispheres: cortical gray matter
localizes and interprets sensory inputs<br></br>controls voluntary and skilled skeletal muscle activity<br></br>functions in intellectual and emotional processing
cerebral hemispheres: basal nuclei (ganglia)
subcortical motor centers help control skeletal muscle movements
(multi): limbic system–a functional system
includes cerebral and diencephalon structures (cingulate gyrus, hippocampal formation, amygdaloid body, hypothalamus, and anterior thalamic nuclei)<br></br>mediates emotional respnose<br></br>forms and retrieves memories
somatic motor innervation: somatic motor
targets skeletal muscle<br></br>one-neuron pathway<br></br>1) cell body of the somatic motor neuron is located in the ventral horn of the gray matter<br></br>2) a long myelinated axon extends out from the ventral root to innervate skeletal muscle cells. neurotransmitter is acetylcholine
autonomic innervation: sympathetic division of ANS
targets smooth muscle, cardiac muscle, and glands<br></br>two-neuron pathway, synapse in an autonomic ganglion<br></br>1) cell obdies of preganglionic sympathetic neurons are located in the lateral horn of the gray matter from T1 to L2<br></br>2) the myelinated preganglionic axon synapses with the postganglionic neuron in an autonomic ganglion located adjacent to the spinal column. neurotransmitter is acetylcholine<br></br>3) a long nonmylinated postganglionic axon extends from the autonomic ganglion to the target organ. neurotransmitter is norepinephrine<br></br>4) preganglionic sympathetic axons emerge from T8-L1 to innervate the adrenal medulla, a specialized sympathetic ganglion. adrenal medulla cells release epinephrine and nopepinephrine into blood stream
autonomic innervation: parasymathetic division of ANS
targets smooth muscle, cardiac muscle, and glands<br></br>two-neuron pathway, synapse in an autonomic ganglion<br></br>1) cell bodies of preganglionic parasympathetic neurons are located in the gray matter of the brain stem (CN III, VII, IX, X) and the sacral region of the spinal cord (S2-S4)<br></br>2) the myelinated preganglionic axon synapses with the postganglionic neuron in an autonomic ganglion close to or within the target organ. neutotransmitter is acetylcholine<br></br>3) a short nonmylinated postganglionic axon innervates the target organ. neurotransmitter is acetylcholine
preganglionic axons follow one of three sympathetic pathways:
1) the preganglionic axon synapseswith a postganglionic neuron in the sympathetic trunk ganglion at the same level and exits via the gray ramus communicans into the spinal nerve at that level<br></br>2) the preganglionic axon ascends or descends in the sympathetic trunk to synapse in another thrunk ganglion. the postganglionic fiber exits the sympathetic trunk via the gray ramus communicans at the level of the synapse<br></br>3) the preganglionic axon passes through the sympathetic trunk, exits on a splanchnic nerve, and synapses in a collateral ganglion. the postsynaptic fiber extends from the collateral ganglion to the visceral organ via an autonomic nerve plexus
