02thebrain-130817073737-phpapp01.pdf

8/9/2019 02thebrain-130817073737-phpapp01.pdf

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Biology & BehaviorThe Brain, The Nervous System & the Glands


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The Neurons and the Neurotransmitters

Neurons

the specialized cells that conduct impulses through the nervoussystem and contain three major parts "a cell body, dendrites, andan axon


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anatomy of a neuroncell body #soma$contains the nucleus and carries out the metabolic, or life"sustaining,functions of a neuron.

dendrites #comes from the Greek word for "tree"$and are the primary receivers of signalsfrom the neurons, they look life the leafless branches of a tree

axon is the slender, tail"like extension of the neuron that transmits signals to thedendrites or cell body of other neurons and to muscles, glands, and other parts of thebody


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works of neurons

a%erent #sensory$neurons relay messages from the senseorgans and receptors "eyes, ears, nose, mouth, and skin ""tothe brain or spinal cord;

e%erent #motor$neurons convey signals from the centralnervous to the glands and the muscles, enabling the body tomove

interneurons #thousand of times more numerous thanmotor or sensory neurons$carry information betweenneurons in the brain and between neurons in the spinal cord


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Glial Cells are specialized cells inthe brain and spinal cord thathold the neurons together,

remove waste products, such asdead neurons, from the brain byengulfing and digesting them, andthey handle other manufacturing,nourishing and cleanup taskssmaller than neurons and make up

more than one"half the volume ofthe human brain

The Synapse is the junctionwhere the axon terminal of asending neuron communicates

with a receiving neuron across thesynaptic cleft.

The Myelin Sheath is a white,fatty coating, wrapped aroundsome axons that acts as insulation


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Neurotransmitters

Neurotransmitter isa chemical substancethat is released intothe synaptic cleftfrom the axonterminal of a sendingneuron, crosses asynapse, and bindsto appropriatereceptors sites on

the dendrites or cellbody of a receivingneuron, influencingthe cell either to fireor not to fire


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why synaptic vesicles can continue topour out

the cell body of the neuron is alwaysworking to manufacture more of theneurotransmitters

unused neurotransmitters in thesynaptic cleft may be broken down intocomponents and reclaimed by the axonterminal to be recycled and used again

the process of REUPTAKE "the

neurotransmitter is taken from thesynaptic cleft back into the axonterminal, intact and ready for immediateuse thus terminating theneurotransmitter's excitatory orinhibitory e%ect on the receiving neuron


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the variety ofneurotransmitters

acetylcholine #Ach$, a neurotransmitterthat exerts excitatory e%ects on theskeletal muscle fibers, causing them tocontract so that the body can move and

has an inhibitory e%

ect on the musclefibers in the heart, which keeps theheart from beating too rapidly

Dopamine #DA$, one of fourneurotransmitters called monoamines,produces both excitatory and inhibitor

e%ects and is involved in severalfunctions, including learning, attention,movement, and reinforcement

Norepinephrine #NE$has an e%ect oneating habits #it stimulates the intake ofcarbohydrates$and plays a major role inalertness and wakefulness.

Epinephrine complementsnorepinephrine by a%ecting themetabolism of glucose and causing thenutrient energy stored in muscles to be

released during strenuous exercise


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Serotonin plays animportant role in regulatingmood, sleep, impulsivity,

aggression, and appetite

Glutamate is the primaryexcitatory neurotransmitterin the brain

GABA #gamma"aminobutyric acid$is themain inhibitoryneurotransmitter in thebrain

Endorphins provide relieffrom pain or the stress ofvigorous exercise andproduce feelings of pleasureand well"being


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The Nervous Systemthe Central Nervous System & the Peripheral Nervous System


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2 divisions of the human nervous system

Central Nervous System #CNS$"composed of brain and the spinal cord

Peripheral Nervous System "connects the central nervous system to allother parts of the body


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why is an intact spinal cord

important to normal functioning?the spinal cord is anextension of the brain that

reaches from the base of thebrain, through the neck, anddown the hollow center ofthe spinal column; it

transmits messages betweenthe brain and the peripheralnervous system


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the brainstem

brainstem is part of the hindbrain that begins at the sitewhere the spinal cord enlarges as it enters the skull, and ithandles functions that are so critical to physical survival thatdamage to it is life"threatening

medulla is the part of the brainstem that controls heartbeat,breathing, blood pressure, coughing, and swallowing

reticular formation #reticular activating system RAS$, plays acrucial role in arousal and attention


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theCerebellum

important to the body's ability to execute smooth, skilled movements

regulates muscle tone and posture

coordinates the series of movements necessary to perform many simple activities without

conscious e%ort

help to heighten ability to focus attention on incoming sensory stimuli and to shiftattention

may increase our e&ciency in acquiring sensory information and discriminating betweensensory stimuli


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the Midbrain

lies between the hindbrain &the forebrain

act as relay stations throughwhich the basic physiologicalfunctions of the hindbrainare linked to the cognitivefunctions of the forebrain

substantia nigra is located in

the midbrain and iscomprised of darkly coverednuclei of nerve cells thatcontrol our unconsciousmotor actions.


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the thalamus & hypothalamus

thalamus has two egg"shaped parts, serves asrelay station for virtuallyall the information that

flows into and out of theforebrain, includingsensory information fromall the senses except smell

hypothalamus regulates

hunger, thirst, sexualbehavior, and a wide

variety of emotionalbehaviors, and internalbody temperature


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the Limbic Systemgroup of structures in the brain,including the amygdala and thehippocampus, that arecollectively involved in emotional

expression, memory, andmotivation.

amygdala plays an important rolein emotion, particularly inresponse to unpleasant or

punishing stimuli

hippocampus is located in theinterior temporal lobes and playsa central role in the storing ofnew memories, the response tonew and unexpected stimuli, andnavigational ability

plays a role in the brain'sinternal representationof space in the form ofneural maps


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the cerebrum

most essential part of the brain is the cerebrum & its cortex

cerebrum is the largest structure in human brain. it is composed oftwo cerebral hemisphere, the left & right which control movement &feeling on the opposing side of the body

corpus callosum connects the two hemisphere and makes possible thetransfer of information and the coordination of activity between them

cerebral cortex is the thin gray outer covering about 1/8 inch thick. itis primarily responsible for the higher mental processes of language,

memory & thinking


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Cerebral cortexgray outer covering about 1/8inch thick and is primarilyresponsible for the highermental processes

contain sensory input areaswhere vision, hearing, touchypressure, and temperatureregister

motor areas, which control

voluntary movement

association areas housememories and are involved inthought, perception, andlanguage


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4 lobes of the cerebral hemisphere

motor cortex "a strip of tissue at the rear of thefrontal lobes that controls voluntary body

movement

plasticity "the brain's capacity to adopt tochanges such as brain damage "of the motorcortex is maintained throughout life

broca's area "involved in directing the pattern of

muscle movement required to produce speechsounds in the left hemisphere of the brain

frontal association areas "involves thinking,motivation, planning for the future, impulsecontrol, and emotional responses

frontal lobes "begin at the front of the brain and extend to the top center of the

skull. they contain the motor cortex, Broca's area, and the frontal associationareas


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the Parietal Lobes "lie

directly behind the frontallobes, in the top middleportion of the brain andare involved in the

reception and processingof touch stimuli

somatosensory cortex,,the site where touch,pressure, temperature,and pain register in thecerebral cortex


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the Occipital Lobes at

the rear of the brain areinvolved in the receptionand interpretation ofvisual information

at the very back ofthe occipital lobesis the primaryvisual cortex, the

site where visionregisters in thecortex


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the Temporal Lobes, located slightlyabove ears, are involved in thereception and interpretation ofauditory stimuli. the site in thecortex where the hearing registers isknown as the primary auditory cortex

wernicke's area "is locatedadjacent to the primaryauditory cortex in the lefttemporal lobe. this is thelanguage area involved in

comprehending the spokenword and in formulatingcoherent written and spokenlanguage


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wernicke's asphasia is a type asphasia resulting from

damage to wernicke's area

wernicke's patient when asked how he wasfeeling, replied " i that there's an awful lot of

mung, but i think i've a lot of net and tunged in alittle wheat duhvayden" #Buckingham & Kertesz,1974$

auditory asphasia#word deafness

$"the person may hearnormally but may not be able to understand spoken

language


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the cerebral hemisphere

Left hemisphere "handles most of the language functions, includingspeaking, writing, reading, speech comprehension, andcomprehension of the written information

Right Hemisphere "#controlling the left side of the body$moreadept at visual spatial relations

auditory cortex in the right hemisphere appears to be farbetter able to process music that the left

augments left hemisphere's language"processing activities'/#figures out what its meant and who says it$#e.g the balancing act$


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the right hemisphere's role

in emotionresponds to the emotional message conveyed byanother's tone of voice

reading and interpreting nonverbal behavior

involve in the expression of emotion through tone ofvoice and facial expression

brain mechanisms responsible for negative emotionsare located in the right hemisphere


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the Peripheral Nervous

System

PNS is made up of all the nerves that connect thecentral nervous system to the rest of the body


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2 subdivisions of the PNS

somatic nervous system "

#1$compose of all the sensory nerves which transmits

information from the sense receptors "the eyes, ears,nose, tongue, and skin ""to the central nervoussystem,

#2$all the motor nerves, which relay messages from

the central nervous system make it possible for youto sense your environment and to move, and they areprimarily under conscious control


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autonomic nervous system "

operates without any conscious control orawareness

transmits messages between the CNS and theglands, the cardiac #heart$muscle, and thesmooth muscles #such as those in the largearteries and the gastrointestinal system$

ANS is further divided into 2 parts "thesympathetic & the parasympatheticnervous system


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sympathetic

nervous systemautomaticallymobilizes thebody's resources,preparing you for

action

parasympatheticnervous systembrings these

heightenedbodily functionsback to normal


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the Endocrine System

Endocrine system isa series of ductless

glands located invarious parts of the

body, thatmanufactured andsecrete the chemicalsubstances knownas hormones, andsecrete them into

the bloodstream,thus a%ecting cellsin other parts of thebody


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