Download The Brain

The Brain
Lesson 1
I. Studying the brain
A. Patients with brain damage
1. Phineous Gage- railroad worker- 1848- tamping iron went through his head- severed connections
between limbic system and frontal cortex
2. Paul Broca- performed autopsy on brain of patient named Leborgne(aka Tan) who had lost the
capacity for speech with no paralysis of the articulatory tract and no loss of verbal comprehension or
intelligence. Broca’s area
3. Carl Wernicke- found a second brain area involved in processing language in the temporal lobe in
the left cererbral hemisphere
B. Gunshot wounds, strokes
C. Producing lesions-surgical removal, severing of neural connections or destruction by chemical or electrical
applications.
D. EEG-( electroencephalogram) electrodes are attached to the scalp to measure the electrical currentsamplified tracing of the activity of a region of the brain – used to study the brain during states of arousal such as
sleeping and dreaming to detect abnormalities and to study cognition
II. Imaging techniques
A. CAT Scans-(computerized axial tomography) - Computerized enhanced x-ray technique (3D x-rays) that
can provide images of the internal structures of the brain- can reveal abnormalities associated with blood clots,
tumors, and brain injuries- size and shape of structures
B. MRI- magnetic resonance imaging- detailed image of the brain or other body parts through strong
magnetic field that aligns the atoms that spin in the brain- Constructs images more detailed than PET or CAT
C. FMRI- takes snapshots of the brain in action- studies both the function and structure of the human brain.
D. PET scans- positron emission tomography- computerized image of the brain and other organs at workSubject receives an injection of a radioactive isotope that acts as a tracer in the bloodstream- how it is
metabolized in the brain reveals the parts of the brain that are more active than others. We can determine which
parts of the brain are involved in particular functions.
E. Optical imagining- new- fiber optic light and a special camera attached to a surgical microscope
Lesson 2- The neuron
I. Neuron- allow the nervous system to carry out its complex signaling tasks efficiently- cells that are specialized
to rapidly respond to signals and quickly send signals of their own.
***Glial Cells- account for 90% of the cells in the adult human brain- Greek word for “glue”- glial cells
act as glue that hold neurons together- support the nervous system by nourishing neurons, removing their
waste products and assisting in communication with each other.
A. Major parts of the neuron
1. Cell Body- soma- main body of the cell- house the nucleus which contains the cell’s genetic
material, and carries out the metabolic or life sustaining functions of the cell.
2. Dendrite- fibers that receive signals from the axons of other neurons and carry those signals to the
cell body.
3. Axon- conducts outgoings messages to other neurons- in the brain they are a few thousandths of
and inch- spinal cord to toes- several feet long.
4. Myelin Sheath- fatty layer of cells that insulate many axons- helps speed up transmission of neural
impulses.- allows muscles to move more efficiently and smoothly- process not complete until about 12 years
old- why kids get better at performing motor skills- MS caused by the destruction of the myelin sheath5. Synapse- tiny gap between neurons.
B. Neurotransmitters-communication between neurons and across the synapse through chemical messengers
1. Acetylcholine- ACh- has an excitatory effect on skeletal muscles, stimulating them to contractinvolved in memory formation and has inhibitory effects on the heart- Curare- SA Indians use it for huntingenters animals blood- blocks receptors for ACh- locking it out and causing paralysis- dies from suffocationBlack widow the opposite- stimulates ACh- trigger intense muscle contractions- causing convulsions that may
lead to death.
2. Monoamines
a. Dopamine- involved in controlling muscle contraction and learning, memory and emotional
functioning- related to schizophrenia (don’t know if it is too much dop. In areas of the brain, too many dop.
Receptors or dop receptors that are overly sensitive- Parkinsons- dop producing cells are destroyed or become
impaired.
b. Norepinephrine- chemical cousin to the hormone adrenalinec. Serotonin- regulates emotional responses, feelings of satiation after eating and sleeping.
3. Endorphins- body’s natural pain killers- - deaden pain by locking out pain messages- also promote
feelings of well being and pleasure4. Amino Acids- Glutamate involved in memory and keeping CNS aroused. – GABA regulates nervous
activity by preventing neurons from overly exciting their neighbors
II. Neural impulses (electric)- complex electrochemical reaction
A. Resting potential- stable negative charge when the cell is inactive
1. Axon is filled and surrounded by fluids containing electrically charged atoms and molecules called
ions- Positively charged sodium and potassium atoms flow back and forth across the cell membrane but they
do not cross at the same rate- there is a slightly higher concentration of negatively charged ions inside the cell
2. -70 millivolts- charge
If the voltage remains constant- the cell is quiet- when the neuron is stimulated channels in
the cell membrane open, briefly allowing positively charged ions to rush in- so then the
neuron’s charge is less negative, or even positive- which allows for an:
B. Action Potential- very brief shift in a neuron’s electrical charge that travels along an axon- you have a
voltage spike- this voltage change races down the axon
After the AP- the channels that allowed the sodium in- close up- sometime is needed for
them to open up again for the neuron to fire
1. Absolute refractory period- minimum length of time after an a.p. during which another a.p. cannot
happen. Not long- 1 or 2 milliseconds- some drugs can produce longer times of unresponsiveness- dentistnovocaine
2. All or none- either the neuron fires or it doesn’t- like a gun- you can’t half fire a gun- the strength
of the stimuli doesn’t matter in if it fires or not- what it will do is a stronger stimuli will cause a rapid volley of
neural impulses. – Thicker axons transmit impulses more rapidly than thinner ones
C. Synapse
1. Synaptic cleft- microscopic gap between the terminal button of one neuron and the cell membrane
of another neurona. presynaptic- neuron that send the message
b. postsynaptic- neuron that receives the signal
2. Neurotransmitters- NT’s are stored in small sacs called synaptic vesicles- the arrival of an action
potential at the axon’s terminal button triggers the release of the NT
D. Postsynaptic signals
1. Postsynaptic potential- a voltage change at a receptor site on a postsynaptic cell membrane- do not
follow the all or none- but instead are graded- vary in size- and they increase or decrease the probability of a
neural impulse in the receiving cell in proportion to the amount of voltage change
a. excitatory PSP- positive voltage change that increases the likelihood that the postsynaptic neuron
will fire action potentialsb. Inhibitory PSP- negative voltage shift that decrease the likelihood that the postsynaptic neuron
will fire action potentials2. Reuptake- process by which NTs are sponged up from the synaptic cleft by the presynaptic
membrane.
Specific nt’s work at specific kinds of synapses- it is like a lock and key- it has to fit to make it work
Agonist- is a chemical that mimics the action of a NT (nicotine is an ACh agonist)
Antagonist- a chemical that opposes the action of a nt- block the action of the nt- by occupying their receptor
sites- rendering them useless- (curare is an antagonist- it blocks the action of ACh
III. How the impulses travel
A. Receptor cells- in sensory organs that detect physical or chemical changes
B. Sensory (afferent)- transmit impulses from sensory receptors(the environment) to the spinal cord or
brain
C. Interneuron- located entirely within the brain and spinal cord intervenes between sensory and motor
neurons- they receive info from sensory neurons or other interneurons- they send signals to other interne. Or
motor neurons
D. Motor (efferent)- carry info away from the spinal cord and brain toward the body parts that are suppose
to respond
E. Reflexes- simplest from of behavior- involves an impulse conduction over few neurons- include papillary
reflex, knee jerk and blinking reflex
Lesson 3- organization of the nervous system
I. Peripheral nervous system- outside the midline of the NS- carries sensory info to and motor info away from
CNS
A. Somatic Nervous system- Controls voluntary muscle movement- skeletal muscles
B. Automatic Nervous system- controls involuntary muscle movement- smooth muscles- cardiac, kidneys
1. Sympathetic nervous system- results in responses the prepare the body for stressful events
2. Parasympathetic nervous system-stimulation results in maintenance of homeostasis calming
following sympathetic stimulation
II. Central nervous system- spinal cord and brain
A. Spinal cord- protected by meninges (membrane)- sensory fibers enter and motor fibers exit composed
mainly of interneurons, and glial cells- also a fluid- cerebrospinal fluid
B. Brain- consistency of soft-serve yogurt or semi-soft cheese covered by meninges (dura, arachniod, pia
matter) Brain evolved from more primitive parts to advanced parts- inside out
1. Reptilian brain- central core- brainstem- basic life functions
a. Medulla Oblongata- basic life support- heart, respiration, body temp, swallowing- controls
vomiting, (why they used to hang people when the neck is broken it severs the medulla)
b. RAS or reticular formation- arousal- awake- screens incoming information and arouses the
higher centers when something happens that needs their attention.
c. pons- translates to bridge- to cerebral hemispheres to cer. Cortex- bridge between cer. Cortex and
cerebellum
d. cerebellum- translates into “little brain”- balance, coordination- procedural memories- if
damaged you would be clumsy and uncoordinated- trouble holding a pencil- riding a bike or
walking
2. Old mammalian brain- limbic system- emotional behavior- some memory and vision
a. Septum- may be associated with rageful behavior and hypersensitivity
b. hippocampus- means horse- related to short term to long term memory- makes a decision to
imprint a memory and transfer it to LTM
c. amygdala- emotional center- especially negative ones- feeding fighting and ones needed for self
preservation- evaluates information for fight and flight- damage to a rats one they forget to
be afraid- in humans they don’t recognize fear in themselves or others
d. hypothalamus- means beneath- five f’s- fight, flight, feeding, Fahrenheit, sexual activity
(fornification)
e. thalamus- means inner chamber- serves as a relay station for sensory input (except smell)contains pineal gland (endocrine system)
3. New mammalian brain- neocortex- high level thought- cortex means bark- holds almost 3/4ths of
all the cells in the human brain- the convolutions allow us to hold the billions of neurons we
have- other mammals it is more smooth
a.Gyri, - rolls- form the folding out portion of the neocortex- sulci- valleys in the convolutions,
fissures- cracks deeper than sucli- very visible- divide the brain
b. Frontal lobe- human cognition, judgment, sense of humor, problem solving, planning1. Motor cortex- movement originates here
2. Broca’s area- expressive language- broca’s aphasia- can’t talk but can think
c. Parietal lobe1. sensory cortex- aka somatosensory cortex- information regarding stimulation from the body2. Wernicke’s area- receptive language- they can hear words, but can’t put the sentences together
d. Occipital lobe- vision- not marked by a fissure- process visual information- visual cortex there
e. Temporal lobe- has auditory cortex- hearingf. Corpus callosum- band of fibers that connect the two hemispheres- allows the right and left
hemisphere to communicate with each other.
Lesson 4- Lateralization of function of the human brain
I. Left hemisphere specialization
A. Speech and language functioning- almost all right handed people and 2/3rd of left handed people show
this specialization in their left hemisphere
1. Wernicke’s area- receptive auditory language functioning is located here. Damage results in
Wernicke’s aphasia- characterized by the outward form of normal speech without coherence
resulting from the inability to comprehend written and spoken language
2. Broca’s area- expressive language is localized there- damage to this area results in Broca’s aphasia
characterized by inability to convert ideas, perceptions and intended messages into smoothly
articulate patterns of speech with appropriate syntax.
B. Contralateral representation- Left somatosensory cortex registers tactile sensations from the right side of
the body- Left motor cortex initiates movement in right side- left temporal cortex receives auditory
information from the right ear- left occipital lobe processes visual information from the right visual field
from both retinas
II. Right hemisphere specialization
A. Spatial functions- pattern recognition, processing visual configurations- plays dominant role in making
fine discrimination among colors
B. Musical functions- variation in tonation- right temporal damage can result in monotone speechdiscrimination and memory of musical passages is right hemisphere
C. Contralateral representation- right sensory cortex- left side sensation- motor cortex initiates movement
in the left side- temporal from left ear- occipital lobe processes visual information from the left visual
field from both retinas
Lesson 5- Endocrine system
I. Comparison of endocrine and neural
A. Hormones- secreted into the blood- neurons- signals sent over a neural network
B. Time- endocrine may take minutes to hours- neural fraction of second to minutes
C. Long lasting- endocrine longer lasting
D. Overlap- some neurotransmitters are chemically identical to hormones, some neurons release signal
molecules into the bloodstream and some cells in the endocrine glands transmit signals through the
blood and to neurons.
II. Hormones
A. Steroids, peptides, amino acids- three general types
B. Active in small amounts
III. Endocrine glands in the brain
A. Pineal gland- lies in the thalamic region- produces melatonin which is involved in the regulation of
circadian rhythms- controlled by light-dark cycles- associated with seasonal affective disorder
B. Hypothalamus- secretes at least nine hormones that stimulate or inhibit the secretion of hormones by the
pituitary.
C. Pituitary- once considered the master gland- because it is the source of hormones that stimulate
reproductive organs, the adrenal cortex and thyroid. Produces growth hormone (somatotropin) which
stimulates the growth of boneIV. Other glands
A. Thyroid- h shaped gland in the neck- contains thyroxine which stimulates and maintains metabolic
activates and is regulated by hypothalamusB. Parathyroid- pea-sized glands generally embedded in the thyroid- helps maintain calcium level in the
blood necessary for normal functioning of neurons by stimulating release of calcium from the bone
C. Adrenal- lies atop the kidneys
1. Cortex- our layer- is the source of steroid hormones- cortosil affect carbohydrate, protein and lipid
metabolism are regulated by ACTH (a hormone produced in pituitary gland)
2. Medulla- core- secrete adrenaline and noradrenalin which increase blood sugar- increase rate and
strength of heartbeat- stimulate respiration and dilate respiratory passages- reinforces sympathetic
nervous system effects
D. Pancreas- dorsal to stomach- regulates blood sugar- imbalances are associated with diabetes and
hypoglycemia
E. Ovaries and testes- reproduction and secondary sex characteristics- estrogen, progesterone, androgens
(such as testosterone) – smaller quantities of estrogens and androgens are produced by the gonads of
opposite sex