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The Brain
The brain is a combination of two
types of cells, glial cells and neurons
The brain consists of 100 billion
neurons and 1012 total cells
Neurons
• Cells in the brain that communicate with
each other
• Neurons are “born” early in life
• Do not regenerate
Glial Cells
• Provide support for neurons
– Structure support
– Metabolic and nutritional support
• Can replace themselves
• Serve to clean up the brain, removes dead
tissue and foreign objects
• Play a large role in neural development
• May even be communicating with neurons
• Role is expanding with new research
Glia and Neurons
Many different types of neurons
Pyramidal neuron
Purkinje neuron
Parts of the Neuron
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Neurons communicate in two ways
Electrical signal: within a neuron
Chemical signal: between neurons
Electrical signal is sent from one part of the
neuron to the other: The signal travels from the
dendrite through the cell body to the axon
– Dendrites receive the signal from another neuron
– Axons send the signal to other neurons
• Chemical signal is sent from the axon of one
neuron to the dendrite of another neuron
Properties of the Neuron
• Neurons contain many ions and are charged
A- are large protein ions that always
stay inside the cell
K+ is potassium. At rest it is mostly
inside the cell
Cl- is chloride. It exists both inside
and outside the cell
Na+ is sodium. It exists primarily
outside the cell
• When the cell is at rest (i.e., not doing anything),
it has a charge of -70 mV. This is called the
resting potential.
• Because of the cell properties, many forces are
acting on the cell.
• 1. Diffusion - substances tend to move from
areas of high concentration to areas of low
concentration.
• 2. Like charges repel each other and opposite
charges attract
• Charges stay the way they are because of the
cell membrane. It is selectively permeable. It
does this by ion channels.
• Normally the membrane closes Na+
channels
• However, if the membrane is given an
electrical charge, it causes the membrane
to lose some permeability
• This opens the sodium channels
• If this electrical charge is large enough,
the flood gates will open (depolarize)
• Change in charge is potentiated down the
length of the neuron
• This wave of charge is called the action
potential
Sodium / Potassium Pump
• Once sodium has rushed in, the cell
quickly regains its composure
(hyperpolarize)
• Active process in which sodium is
removed from the cell
• Sodium is exchanged for potassium
• Requires metabolic activity
• Returns charge inside cell to -70 mV
• Refractory period-neuron cannot fire
Communication Between Neurons
• When the action potential
reaches the terminal button, it
causes a release of chemicals
called neurotransmitters
• These neurotransmitters are
dumped into the synapse, the
space between the axon of one
neuron and the dendrite of
another
• Neurotransmitters come into contact with
membrane of the other neuron
• Receptors on the dendrite detect the
neurotransmitter
• NT binds to the receptor
• This causes a temporary change in the
membrane, allowing a little sodium inside
the cell
• This small charge is called the graded
potential
• This is passed on to the axon and it
summates
• Myelin – a layer of proteins that are
wrapped around the axon.
• Two functions: to protect the axon, and to
speed up transmission
• Without myelin, neural transmission is
inefficient
• Multiple Sclerosis – an autoimmune
disorder in which the myelin is destroyed.
– Fatigue, pain, motor disorders, cognitive
disorders, etc.
Removal of Neurotransmitter
• After the NT is initially released, the
chemical must be removed
• This is done in a couple of different ways
– Biochemical breakdown of the NT using
enzymes
– Reuptake: NT is pulled back into the
presynaptic button and packaged to be
released again
Types of Neurotransmitters
• Excitatory
– Glutamate
– Acetylcholine
• Inhibitory
– GABA
– Norepinephrine
• Both
– Dopamine
– Serotonin
Effects of Drugs
• Psychopharmacology- the study of how
drugs affect behavior
• Nearly all drugs work by affecting
neurotransmitter release
Effect of Prozac
Prozac is an example of a SSRI – a selective
serotonin reuptake inhibitor
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Hives
inability to sit still
itching
restlessness
skin rash
Less common Chills or fever
joint or muscle pain
Rare Anxiety
cold sweats
confusion
convulsions (seizures)
cool pale skin
diarrhea
difficulty with concentration
drowsiness
dryness of the mouth
excessive hunger
fast or irregular heartbeat
headache
increased sweating
increased thirst
lack of energy
mood or behavior changes
overactive reflexes
purple or red spots on the skin
racing heartbeat
shakiness or unsteady walk
shivering or shaking
talking, feeling, and acting with excitement and activity you cannot control
trouble with breathing
unusual or incomplete body or facial movements
unusual tiredness or weakness
Incidence not known Abdominal or stomach pain
agitation
back or leg pains
bleeding gums
blindness
blistering, peeling, or loosening of the skin
bloating
blood in the urine or stools
bloody, black, or tarry stools
blue-yellow color blindness
blurred vision
chest pain or discomfort
clay-colored stools
constipation
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sore throat
sores, ulcers, or white spots on the lips or in the mouth
stopping of heart
sudden shortness of breath or troubled breathing
sudden weakness in the arms or legs
sudden, severe chest pain
swelling of the face, ankles, or hands
swollen or painful glands
thoughts of killing oneself
tightness in the chest
tiredness
twitching, twisting, or uncontrolled repetitive movements of the tongue, lips, face, arms, or legs
unconsciousness
unpleasant breath odor
unusual bleeding or bruising
unusual drowsiness, dullness, tiredness, weakness, or feeling of sluggishness
unusually pale skin
use of extreme physical or emotional force
vomiting of blood
yellow eyes or skin
Some fluoxetine side effects may not need any medical attention. As your body gets used to the medicine these side effects may disappear. Your health care professional may be able to
help you prevent or reduce these side effects, but do check with them if any of the following side effects continue, or if you are concerned about them:
More common Decreased appetite
Less common or rare Abnormal dreams
breast enlargement or pain
change in sense of taste
changes in vision
feeling of warmth or heat
flushing or redness of the skin, especially on face and neck
frequent urination
hair loss
increased appetite
increased sensitivity of the skin to sunlight
menstrual pain
stomach cramps, gas, or pain
unusual secretion of milk, in females
weight loss
yawning
Incidence not known Cracks in the skin
loss of heat from the body
painful or prolonged erections of the penis
scaly skin
swelling of the breasts or breast soreness in both females and males
unusual milk production
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continuing vomiting
cough or dry cough
dark urine
decreased urine output
decreased vision
depression
difficulty with breathing
difficulty with swallowing
dizziness or lightheadedness
eye pain
fainting
fast, pounding, or irregular heartbeat or pulse
general body swelling
high fever
hives, itching, puffiness or swelling of the eyelids or around the eyes, face, lips, or tongue
hostility
indigestion
irregular or slow heart rate
irritability
large, hive-like swelling on the face, eyelids, lips, tongue, throat, hands, legs, feet, or sex organs
light-colored stools
loss of appetite
loss of bladder control
muscle twitching
nausea
nightmares
noisy breathing
nosebleeds
pain in the ankles or knees
painful, red lumps under the skin, mostly on the legs
pains in the stomach, side, or abdomen, possibly radiating to the back
pinpoint red spots on the skin
rapid weight gain
red or irritated eyes
red skin lesions, often with a purple center
redness, tenderness, itching, burning, or peeling of the skin
severe muscle stiffness
severe sleepiness
slurred speech
• Alcohol
– Activates GABA receptors-inhibitory
• Nicotine
– Activates acetylcholine receptors-stimulatory
– Changes overall number of ACH receptors
• Cocaine
– Blocks reuptake of dopamine– Stimulates release of dopamine– Anesthetic effect on cells
– Dopamine can be both, stimulatory here
• Amphetamine / Methamphetamine
– Similar to cocaine with no anesthetic effect
• Crack
– Exactly like cocaine, just more efficient
• Heroin
– Activates opiate receptors-inhibitory
• Marijuana
– Activates cannabinoid/THC receptors (similar
to opiate)-inhibitory
• Ecstasy (MDMA)
– Selectively destroys neurons that release
serotonin
– Serotonin is dumped out when the cell dies
– Increases overall body temperature
Divisions of the Nervous System
• Central Nervous System: Includes
Brain and Spinal Cord
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Peripheral Nervous System: All other
neural tissue. Specifically, the periphery.
This includes muscles, the skin, and
even the organs
• PNS broken down into two parts
1. Somatic nervous system: nerve fibers
that send sensory information to the
central nervous system AND motor nerve
fibers that project to skeletal muscle.
2. Autonomic nervous system – Controls
the "insides" (the "viscera") of our body,
like the heart, stomach and intestines
- functions in an involuntary, reflexive
manner
- does things like constrict blood vessels,
dilate pupils, and even makes our heart
beat fast on a roller coaster, etc.
-Has two components
- A. Sympathetic nervous system:
- B. Parasympathetic nervous system
• Sympathetic NS- Regulates “Fight or
Flight”
– Prepares the body during stressful situations
– Increases heart beat, blood pressure, speeds
breathing, slows digestive function
• Parasympathetic NS – Regulates "rest and
digest"
– Keeps the body running calmly
– Shuts down the sympathetic NS when the
situation becomes less stressful
Parts of the CNS
• Spinal Cord: Two types of material,
white matter (Axons) and grey matter
(cell bodies)
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”
• Spinal cord relays sensory and motor
information to and from the brain
• Controls reflexes
– Ex. Knee jerk reflex, pain reflex
• Afferent neurons: neurons that send their
signal TOWARDS the spinal cord
• Efferent neurons: neurons that send their
signal AWAY from the spinal cord
• Reflex involves two neurons, one afferent
and one efferent
• Reflexive action takes place before it is
sent to the brain
• Allows for extremely efficient processing
Parts of the Brain
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3 major divisions
1. Hindbrain:
Cerebellum; Pons;
Medulla
2. Forebrain: Cortex,
amygdala,
hippocampus,
thalamus,
hypothalamus
3. Midbrain
Anatomical classification
• Cerebral
hemispheres
• Diencephalon
– Thalamus
– Hypothalamus
• Brain stem
– Midbrain
– Pons
– Medulla
• Cerebellum
• Spinal cord
Hindbrain
• Cerebellum: Extremely large area, millions
of neurons
– Responsible for coordination of movement
– Plays a role in learning (muscle memory)
– Also some role in cognition
• Pons
– Important for sleep and especially dreaming
• Medulla
– Controls all vital functions of the body
including breathing and heart rate
Cerebellum
Two major hemispheres: three lobes each
Anterior
Posterior
Floculonodular
Separated from brain stem by 4th ventricle
Vermis: midline lobe connecting
hemispheres
Outer cortex of gray
Inner branching white matter, called
“arbor vitae”
Brain stem
 Midbrain
 Pons
 Medulla
oblongata
Forebrain
• Thalamus
– Primary relay station of the brain
– Almost all sensory information passes through
before going elsewhere
• Hypothalamus
– Regulates autonomic nervous system
– Regulates hormones, Feeding, Fighting,
Fleeing, and sexual behavior
• Amygdala
– Responsible for many aspects of emotion
– Emotional learning
• Hippocampus
– Especially important for learning and memory
– Resolving conflict
• Cerebral Cortex
– Does just about everything
– Many think that the cortex is what makes
humans the way they are
– Cortex is broken up into 4 lobes:
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Frontal lobe: the front of the brain
Temporal lobe: side, the temples
Parietal lobe: kinda middle portion
Occipital Lobe: very back
• Frontal lobe
– Important for planning
– Thinking / decision making
– Primary motor cortex: Generation of
movement
– Broca’s area: Production of Speech
• Temporal lobe
– Audition
– Wernicke’s area: Language comprehension
• Parietal lobe
– Somatosensory function (touch, vibration,
pain, pleasure)
– Combination of all senses with vision
• Occipital lobe
– Vision: Primary visual cortex
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
Cerebral hemispheres: note lobes
 Divided by longitudinal fissure into right &
left sides
 Central sulcus divides frontal from parietal
lobes
Two Halves of the Brain
• Brain is actually two
different halves. It is
split down the middle,
with the right and left
side being very
similar to the other
• The two hemispheres
are connected by the
corpus callosum: a
bunch of axons
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
 Third ventricle
 In diencephalon
 Connections
 Interventricular foramen
 Cerebral aqueduct
 Fourth ventricle
 In the brainstem
 Dorsal to pons and top of medulla
 Holes connect it with subarachnoid space
• Each side of the brain controls the
opposite side of the body.
– Ex. Moving right arm controlled by the left
side of the brain.
• Systematic differences in right vs. left.
• Most language and music on the left.
– Somewhat different for left-handed people
• The right hemisphere more involved with
visual imagery and creativity.
Split-brain Patients
• Sometimes the corpus callosum of a
person is cut. It is often surgically cut in
patients with severe epilepsy.
• Allows for the study of the role of each
hemisphere
Studying the Brain with Animals
• Lesioning of the brain
– Electrical lesions- electricity is passed through
an electrode until neurons die
– Chemical lesions- inject chemicals like acid to
kill neurons
• Injection of drugs
• In Vitro analysis: “In the Lab” – brain tissue
is removed, isolated, and studied on its
own. Individual neurons can be studied
• In Vivo analysis: “In the Living” – the brain
is studied in an intact animal
Studying the Brain of Humans
• EEG: electroencephalogram – electrodes
are placed on the scalp.
– It records the electrical activity of neurons.
– Problem: It records from thousands of
neurons at a time; not very precise
EEG printout
• “CAT” scan: Computerized tomography
– Computer enhanced 3-D X-Rays
– Not much resolution, still life
• MRI: Magnetic resonance imaging – uses
magnetic fields to get brain scans
– Just get a picture
• PET scan: Positron Emission Tomography
– patients are injected with radioactive glucose.
The scanner tracks where the glucose moves
to. This is used as an indicator of neural
activity.
- Has problems: very expensive, resolution is
fairly low.
• Functional MRI (fMRI) – Registers
changes in the metabolism of cells
– Get 3-D picture of real time brain activity
– Very expensive
Sensory areas
Posterior to central sulcus
 Primary somatosensory
cortex: postcentral
gyrus of parietal lobe
(allows conscious awareness of
sensation and the ability to
localize it: where the sensation is
from)
 Somatosensory
association area:
behind it
(understanding of what is being
felt: the meaning of it)
From special sense organs
 Sight: occipital lobe
 Primary visual cortex (17)
 Handles info from
contralateral retina (right ½
of visual field is on left side)
 Map of visual space
 If damaged: functionally
blind because no conscious
awareness of sight
 Visual association area
(18 & 19)
 Face recognition is usually
on the right side
 Hearing: temporal lobe
 Primary auditory area (41)
 Auditory association area
(22)
 Smell (olfactory sense): uncus
 Deep in temporal lobe along medial surface