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Chapter 2
The Biological Perspective
The Nervous System - An extensive network of specialized cells that
carries information to and from all parts of the body.
Neurons & Nerves: Building the Network
• Neuron –
basic unit (cell) of nervous system and receives and sends
messages within that system
microscopic; 100 billion; 200 types (size / shape)
3 Structures of the Neuron
1. Dendrite – branches that receive information from other neurons & transmits
information toward the cell body (tree like)
2. Soma – Cell body that keeps neuron alive; determines if it will “fire” (transmit info)
3. Axon – extending fiber that conducts impulses away from cell body & transmits
them to other neurons or neural cells
• Glial Cells – grey fatty cells that provide support for the neurons to grow on & around,
deliver nutrients, produce myelin, clean up waste & dead neurons
• Myelin sheath – fatty substance that coats axon to insulate, protect & speed up
impulse
• Nerve – bundles of axon coated in myelin that travel together through the body
Message W/in the Neuron: The Neural Impulse
• Resting potential – when neuron is not firing (- charge inside + outside)
• Action Potential – release of the neural impulse consisting of the
reversal of the electrical charge within the axon
(+ sodium (Na) enters the cell)
• All or nothing – a neuron either fires completely or does not fire at all
Sending the Message to Other Cells: Synapse
Synapse – site of transmission of nerve impulses from one nerve cell to another
– Axon terminal – branches at the end of axon
– Synaptic bulb (knob) – rounded area on the end of the axon terminal
– Synaptic cleft (gap)– space between bulb of one cell and the dendrite of another
– Receptor sites- holes is surface of dendrite; shaped to receive certain neurotransmitters
– Neurotransmitters – chemicals in the synaptic vesicles; when released effect the next
cell
Neurotransmission / Synapse
1- Neuron at rest (- inside + outside)
2 - Neural impulses move down axon;
gate opens; +Na enters cell
voltage changes from (-) to (+)
3- When impulse reach button tip;
must get across synaptic cleft (gap);
synaptic vesicle release neurotransmitter
4- When reaches the other side;
briefly bond w/ receptor sites
(lock & key)
5- Receiving membrane will change;
excite – increase firing (+ voltage)
inhibit –decrease firing (- voltage)
6- Neuron returns to resting state (- voltage)
Action potential - a sequence of gates opening down
the length of the cell (as 2nd gate opens 1st closes)
-multiple +/- messages sent; take average
Synapse
• Excitatory Synapses – synapse at which a neurotransmitter causes the
receiving cell to fire.
• Inhibitory Synapses – synapse at which neurotransmitter causes the
receiving cell to stop firing.
Agonists – chemical substances that mimic or enhance the effects of a
neurotransmitter on the receptor sites of the next cell, increase
in or decreasing the activity of that cell
Antagonists – chemical substances that block or reduce a cells response to
the action of other chemicals or neurotransmitters.
Neurotransmitters (NT)
• Serotonin – Excitatory or inhibitory; involved in mood, sleep and appetite
• Dopamine – Excitatory or inhibitory; control of movement and pleasure
• Acetylcholine – Excitatory or inhibitory; muscle contraction, memory
• Norepinephrine – Mainly excitatory; involved in arousal and mood
• GABA - (gamma-aminobutyric acid) major inhibitory NT; sleep & inhibits movement
• Glutamate – major excitatory NT memory formation, nervous system development
• Endorphins – inhibitory neural regulators; involved in pain relief “ natures opiate”
endorphin rush: “falling in love” / battle field
Cleaning up the Synapse
1) Reuptake - neurotransmitters are take back into the synaptic vesicles
– Cleans up the synapse
– Some drugs inhibit the reuptake like cocaine
– Depression if small amounts of serotonin released
•
•
Medications SSRIs (selective serotonin reuptake inhibitors)
Leaves more serotonin in synapse to elevate mood
2) Enzymes – breakdown neurotransmitters not taken back into vessels
–
Acetylcholine – muscle activity can’t wait for reuptake; enzyme breaks it down
Quiz
1) Which part of the neuron receives messages from other cells?
a)
b)
Axon
Dendrite
c) Soma
d) Myelin
2) Which one of the following is NOT a function of the myelin?
a)
b)
c)
d)
Insulates the axon
Speeds up the neural message
Protects the nerve fiber from damage
Aids in reuptake
3) When the neuron’s action potential is released, _______ ions are
rushing into the axon through openings on the membrane.
a)
b)
Sodium
Potassium
c) Chloride
d) Oxygen
Quiz
4) When the action potential reaches the end of the axon terminals, it
causes the release of
a)
b)
c)
d)
An electrical spark that sets of the next neuron
Positively charged ions that excite the next cell
Negatively charged ions that inhibit the next cell
Neurotransmitters that excite or inhibit the next cell
5) Receiving neurons have special __________ that fit the shape of
certain molecules.
a)
b)
Synaptic vesicles
Gaps
c) Receptor sites
d) Branches
6) Which of the following is associated with sleep, mood and appetite?
a)
b)
Acetylcholine
GABA
c) Serotonin
d) Endorphin
Quick Quiz
a)
Which word in ( ) better fits each of the following definitions?
1.
2.
3.
4.
Basic building blocks f the nervous system (nerves, neurons)
Site of communication between neurons (synapse, myelin sheath)
Opiate-like substance in the brain (dopamine, endorphin)
Chemicals that make it possible for neurons to communicate (neurotransmitters,
hormones)
The Nervous System
1) Central Nervous System (CNS)
2) Peripheral Nervous System (PNS)
The Nervous System
1. Central Nervous System (CNS)
1. Brain – Interprets & stores information & sends orders to muscles glands, &
organs
1. Spinal Cord –long bundle of neurons that carry messages between the body &
brain responsible for fast, life saving reflexes
The Nervous System
2) Peripheral Nervous System (PNS)
Transmits information to and from the central nervous system
All nerves and neurons that are not contained in the brain and spinal cord
but that run through the body itself
1. Somatic nervous system - carries sensory info from the senses to CNS &
from the CNS to the voluntary muscles.
a) Sensory pathways – (Afferent) nerves from sensory organs to CNS
b) Motor pathways – (Efferent) nerves from CNS to the voluntary muscles
2. Autonomic nervous system- controls involuntary muscles, organs & glands
1) Sympathetic nervous system – prepares body to react and expend energy
in time of stress (fight or flight)
2) Parasympathetic nervous system – maintain body functions in relaxed
state; conserves energy; restore to
normal functioning after arousal
The Peripheral Nervous System
Parasympathetic & Sympathetic
Stem cell research: Pro or Con
• Neurogenesis
– production of new neurons from immature stem
cells
• Stem Cells – immature cells that renew themselves; grow into any cell
– Need cells a few days old
• Abortion clinics
• Excess from fertility clinics
The Endocrine Glands
Endocrine Glands – organs produce hormones & release into blood stream
Hormones – produced by endocrine glands; effects functioning of other organs
The Endocrine Glands
a) Pituitary Gland – growth hormones & affects all other glands (Master Gland)
– Oxytocin –enhances uterine contractions during birth; ejection of milk
/nursing
b) Pineal Gland –
– Melatonin – regulate daily biorhythms; promotes sleep
c) Thyroid Gland – regulates metabolism
d) Pancreas - controls levels of sugar in the blood
e) Gonads - Sex glands – development & maintenance of reproductive organs
- Ovaries and testes
androgen – testosterone – male characteristics at puberty
estrogen – female characteristics at puberty
progesterone – lining of uterus in prep for fertilized egg
f) Adrenal Glands
– Adrenal hormones - produced by adrenal glands; emotion and stress
respond to heat; cold; pain; exercise; caffeine; nicotine
Cortisol - ^blood sugar; boost energy; gain weight
Epinephrine – adrenaline; fight or flight; memory
Quiz
1.
If you burn your finger, your immediate reaction will probably involve
all BUT which of the following?
a)
b)
2.
c) Afferent neurons
d) Efferent neurons
If you are typing in the computer keyboard, the sensation of your
fingers touching the keys is most likely communicated by ____ .
a)
b)
c)
d)
3.
The brain
Spinal cord
The autonomic neurons
Motor pathway neurons
Sensory pathway neurons
Autonomic neurons
The neurons of the motor pathway control _______ .
a)
b)
Stress reactions
Organs and glands
c) Involuntary muscles
d) Voluntary muscles
Quiz
4) What type of cell can become other types of cells in the body?
a)
b)
Blood cells
Stem cells
c) Neurons
d) Basal cells
5) Which of the following is NOT a function of the sympathetic division?
a)
b)
c)
d)
Increasing digestive activity to supply fuel for the body
Dilating the pupils of the eyes
Increasing the heart rate
Increasing the activity of the lungs
6) Which of the following would be active if you are sleeping?
a)
b)
Sympathetic division
Parasympathetic division
c) Somatic Division
d) motor division
7) Andrew never really grew to be very tall. The doctor told his parents
that Andrew’s ______ gland did not secrete enough growth hormone.
a)
b)
Pituitary
Adrenal
c) Thyroid
d) Pancreas
The Structures of the Brain
Location of function – brain areas for particular functions
• Brain stem – top of spinal cord ; pons & medulla
• Pons – sleeping; waking & dreaming; left-right body coordination; arousal
• Medulla – some automatic functions; breathing, swallowing & heart rate
functions that are not consciously willed
• Cerebellum – control & coordinate involuntary,
rapid, fine motor movement
Reticular activating system:
Reticular formation
–General attention, alertness and arousal
Structures Under the Cortex
• Limbic System –
structures involved in learning, emotion, memory & motivation
• Thalamus – relays sensory message to the cortex; processes some sensory
info
Traffic officer of the brain – directs to higher area
olfactory bulb (smell)
Structures Under the Cortex
• Hypothalamus
– Hypothalamus – motivational behavior; sleep, hunger; thirst & sex
Structures Under the Cortex
• Amygdala – arousal and regulation of emotions
initial emotional response to sensory info ( danger or threat)
fear and memory of fear
• Hippocampus – “sea horse” in Latin
formation of long term memory
storage of memory for locations objects
The Cortex
• The Cerebrum – higher forms of thinking
largest grain structure
upper part of brain; 2 hemispheres
most sensory; motor and cognitive processes
Cerebral hemispheres – 2 halves of cerebrum (right & left)
Corpus callosum – thick bundle of neurons connecting 2 cerebral hemispheres
Lateralization – specialization of 2 hemispheres for particular operations
Cortex – collection of several thin layers of cells covering cerebrum
higher mental functions & interpret sensory input
1/8” thick – ¾ of all cells in human brain
deep crevices and wrinkles (more neurons) rat-smooth
Grey matter – grey tissue of brain
(White matter – long myelin coved axons)
•
Lobes of the Cortex
Occipital – visual centers
blindness / recognition
•
Parietal – somatosensory cortex
touch, taste & temp
•
Temporal – auditory cortex
hearing &
meaningful speech
Wernicke’s aphasia – use of meaningless words
•
Frontal – higher mental functioning
make plans; think creatively;
fluent speech
Motor cortex
Mirror neurons
Left lobe - Broca’s area – speech
Broca’s aphasia – inability to understand written or
spoken language
Neuron and Brain Lobes
Prefrontal Cortex & Personality
• Phineas Gage
Prefrontal Cortex - personality
• Rats and mice only 3.5%
• Humans – 29%
• Phineas Gage – railroad worker
inch thick – 31/2 foot rod through head
miracle lived; think; speak; remember
Dr. Jekyll / Mr. Hyde change
“not Phineas”
mild mannered to mean & angry
responsible to not work; hold jobs
Right and Left Brain
Right Brain
•
•
•
•
•
•
•
•
•
•
Controls left hand
Non verbal
Spatial visual ability
Facial recognition
Emotional thought
Emotional recognition
Process the whole
Pattern recognition
Musical / artistic
Intuitive
Left Brain
•
•
•
•
•
•
•
•
•
•
Controls right hand
Spoken language
Written language
Reading
Logic
Symbolic
Sequential task
Rational / analytic
Analysis of detail
Math
Split Brain
Split Brain:
is left dominant?
•
Shown composite of photo (a) asked to pick
out the face seen from series of photos (b);
•
Stated; seen face on right side of composite;
•
Yet, pointed with their left hands to the face
that had been on the left
•
2 hemisphere not communicate
•
Verbal left side – only saw right half
•
Mute right side – aware of left half
Quick Quiz
1) Keeping in mind what both sides of the brain are involved in most
activities, which of the following is / are more closely associated with the
left hemisphere?
a)
b)
c)
d)
e)
Enjoying a musical recording
Wiggling the left big toe
Giving a speech in class
Balancing a checkbook
Recognizing a long lost friend
His and Her Brains?
His and Her Brains
• Gender differences (intuition, abilities) are stereotypes
– More alike than different.
• Sex differences; result rather than cause of behavioral differences
– Nature or nurture
• Brain difference not explain behavior or performance
– Difference in brain activity but not ability to complete
– Listen to John Grisham; women left and right temporal; men only left.
1.
Quiz
In which lobe of the cortex do you find the primary auditory area?
a)
b)
2.
Frontal
Parietal
c) Temporal
d) Corpus
A man wakes up and finds that people around him are using words
that make no sense, and they don’t understand him. This is like
_____
a)
b)
4.
c) Occipital
d) Parietal
The higher mental function, such problem solving are found in ____ .
a)
b)
3.
Frontal
Temporal
Wernicke’s aphasia
Broca’s aphasia
c) apraxia
d) spatial neglect
If you were a split brain patient, which would be TRUE?
a)
b)
c)
d)
Objects in your left visual field would be easily named
Objects in you left visual field are invisible
Objects in your right visual field would be easily named
Objects in you right visual fields are invisible
Review
Neurotransmission / Synapse
1- Neuron at rest (- inside + outside)
2 - Neural impulses move down axon;
gate opens; +Na enters cell
voltage changes from (-) to (+)
3- When impulse reach button tip;
must get across synaptic cleft (gap);
synaptic vesicle release neurotransmitter
4- When reaches the other side;
briefly bond w/ receptor sites
(lock & key)
5- Receiving membrane will change;
excite – increase firing (+ voltage)
inhibit –decrease firing (- voltage)
6- Neuron returns to resting state (- voltage)
Action potential - a sequence of gates opening down
the length of the cell (as 2nd gate opens 1st closes)
-multiple +/- messages sent; take average
Neuron
The Brain