Transcript chapter 3 powerpoint

Biology and Behavior
Chapter 3
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Neural Communication
The body’s information system is built from
billions of interconnected cells called neurons.
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Neuron
A nerve cell, or a neuron, consists of many
different parts.
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Parts of a Neuron
Cell Body: Life support center of the neuron.
Dendrites: Branching extensions at the cell body.
Receive messages from other neurons.
Axon: Long single extension of a neuron, covered with
myelin sheath to insulate and speed up messages
through neurons.
Axon: Terminals: Branched endings of an axon that
transmit messages to other neurons.
Synapse: Space between the neurons
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How does a Neuron fire?
• Resting Potential: slightly
negative charge.
• Reach the threshold when
enough neurotransmitters
reach dendrites.
• Go into Action Potential.
• All-or-none response.
• Transfer of ions across
axon’s membrane causes
electrical charge.
It is an electrochemical process
• Electrical inside the neuron
• Chemical outside the neuron (in
the synapse in the form of a
neurotransmitter).
• The firing is call Action
Potential.
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The All-or None Response
• The idea that
either the
neuron fires or
it does not- no
part way firing.
• Like a gun
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Steps of Action Potential
• Dendrites receive neurotransmitter from another
neuron across the synapse.
• Reached its threshold- then fires based on the
all-or-none response.
• Opens up a portal in axon, and lets in positive ions
(Sodium) which mix with negative ions (Potassium)
that is already inside the axon (thus Neurons at
rest have a slightly negative charge).
• The mixing of + and – ions causes an electrical
charge that opens up the next portal (letting in
more K) while closing the original portal.
• Process continues down axon to the axon
terminal.
• Terminal buttons turns electrical charge into
chemical (neurotransmitter) and shoots message
to next neuron across the synapse.
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Refractory Period & Pumps
Refractory Period: After a neuron fires an action
potential it pauses for a short period to recharge
itself to fire again.
Sodium-Potassium Pumps: Sodium-potassium
pumps pump positive ions out from the inside
of the neuron, making them ready for another
action potential.
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Action Potential Properties
All-or-None Response: When the depolarizing
current exceeds the threshold, a neuron will
fire. If the depolarizing current fails to exceed
the threshold, a neuron will not fire.
Intensity of an action potential remains the
same throughout the length of the axon.
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Synapse
Synapse [SIN-aps] a junction between the axon
tip of the sending neuron and the dendrite or
cell body of the receiving neuron. This tiny gap
is called the synaptic gap or cleft.
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How Neurons Communicate
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Neurotransmitters
Neurotransmitters
(chemicals) released
from the sending
neuron travel across the
synapse and bind to
receptor sites on the
receiving neuron,
thereby influencing it to
generate an action
potential.
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TYPES OF
NEUROTRANSMITTERS
Acetylcholine (ACH)
• Deals with motor
movement and
memory.
• Lack of ACH has
been linked to
Alzheimer’s disease
and muscle paralysis
Dopamine
• Deals with attention,
motor movement and
alertness.
• Lack of dopamine
has been linked to
Parkinson’s disease.
• Too much has been
linked to
schizophrenia.
Serotonin
• Involved in mood
control.
• Lack of serotonin
has been linked to
clinical depression.
Endorphins
• Involved in pain
control.
Divisions of the Nervous
System
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The Nervous System
Nervous System: Consists of all the nerve cells. It
is the body’s speedy, electrochemical
communication system.
Central Nervous System (CNS): the brain and
spinal cord.
Peripheral Nervous System (PNS): the sensory and
motor neurons that connect the central nervous
system (CNS) to the rest of the body.
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Peripheral Nervous System
• All nerves that are
not encased in bone.
• Everything but the
brain and spinal
cord.
• Is divided into two
categories….somatic
and autonomic.
Somatic Nervous System
• Controls voluntary
muscle movement.
Autonomic Nervous System
• Controls the
automatic functions
of the body.
• Divided into two
categories…the
sympathetic and the
parasympathetic
Autonomic Nervous System (ANS)
Sympathetic Nervous System: Division of the
ANS that arouses the body, mobilizing its
energy in stressful situations.
Parasympathetic Nervous System: Division of
the ANS that calms the body, conserving its
energy.
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Sympathetic Nervous System
• Fight or Flight
Response.
• Automatically
accelerates heart
rate, breathing,
dilates pupils, slows
down digestion.
Parasympathetic Nervous System
• Automatically slows
the body down after
a stressful event.
• Heart rate and
breathing slow down,
pupils constrict and
digestion speeds up.
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The Brain
Brain Structures
• Some scientists
divide the brain up
into three parts.
• Hindbrain
• Midbrain
• Forebrain
Hindbrain
• Structures on top of our spinal cord.
• Controls basic biological structures.
The brain in
purple makes up
the hindbrain.
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Medulla Oblongata
• Located just
above the spinal
cord.
Involved in control
of
• blood pressure
• heart rate
• breathing.
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Pons
• Located just
above the
medulla.
• Connects
hindbrain with
midbrain and
forebrain.
• Involved in facial
expressions,
sleep, and
attention
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Cerebellum
• Located in the back
of our head- means
little brain.
• Coordinates muscle
movements.
Midbrain
• Coordinates simple
movements with
sensory information.
• Contains the
reticular activating
system: arousal and
ability to focus
attention.
• If damaged…Coma
Forebrain
• Thalamus
• Receives sensory
information and
sends them to
appropriate areas of
forebrain.
• Like a switchboard.
• Everything but smell.
Hypothalamus
The Hypothalamus lies
below (hypo) the
thalamus. It directs
several maintenance
activities like eating,
drinking, body
temperature, and
control of emotions. It
helps govern the
endocrine system via
the pituitary gland.
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Hypothalamus
• Maybe most
important structure
in the brain.
Controls and regulates
• Body temperature
• Sexual Arousal
• Hunger
The most powerful
• Thirst
structure in the brain.
• Endocrine System
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Limbic System
• EMOTIONAL
CONTROL CENTER
of the brain.
• Made up of
Hypothalamus,
Amygdala and
Hippocampus.
The Limbic System
The Limbic System is a
doughnut-shaped
system of neural
structures at the border
of the brainstem and
cerebrum, associated
with emotions such as
fear, aggression and
drives for food and sex.
It includes the
hippocampus, amygdala,
and hypothalamus.
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The Limbic System
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Amygdala
• Involved in how
we process
memory.
• More involved in
volatile
emotions like
fear & anger.
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Hippocampus
• Involved in the
processing and
storage of
memories.
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Cerebrum
• Largest part of the
brain
• Surface of brain
called the: cerebral
cortex
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Areas of the Cerebral Cortex
• Divided into 4 lobes
–
–
–
–
Frontal
Temporal
Parietal
Occipital
Frontal Lobes
• Deals with planning, maintaining
emotional control and abstract
thought.
• Contains Motor Cortex: sends
signals to our body controlling
muscle movements.
• Contains Broca’s Area:
responsible for controlling
muscles that produce speech.
• Damage to Broca’s Area is called
Broca’s Aphasia: unable to make
movements to talk. Contains
Broca’s Area.
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Motor and Sensory Cortexes
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Parietal Lobes
• Located at the top
of our head.
• Contains the somatosensory cortex.
• Rest are association
areas.
Temporal Lobes
• Process sound
sensed by ears.
• Not lateralized.
• Contains Wernicke’s
area which
interprets written
and spoken speech.
• Wernike's Aphasia:
unable to understand
language: the syntax
and grammar
Occipital
Lobes
• In the back of our
head.
• Handles visual input
from eyes.
• Right half of each
retina goes to left
occipital lobe and vice
versa.
• Contains Visual Cortex:
interprets messages
from our eyes into
images we can
understand.
The Corpus Callosum
Divides the 2
hemispheres.
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Hemispheres
Divided into to
hemispheres.
• Contralateral
control: right
controls left and vice
versa.
In general,
Left Hemisphere: logic
and sequential tasks.
Right Hemisphere:
spatial and creative 51
tasks.
Hemispheres
• Divided into a left and
right hemisphere.
• Contralateral
controlled- left controls
right side of body and
vice versa.
• Brain Lateralization.
• Lefties are better at
spatial and creative
tasks.
• Righties are better at
logic.
Accidents
Phineas Gage Story
• Personality changed
after the accident.
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Brain Plasticity
• The idea that the
brain, when
damaged, will
attempt to find
news ways to
reroute
messages.
• Children’s brains
are more plastic
than adults.
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Lesions
Brain tumors also lesion brain tissue.
Ways to study the Brain
• Electroencephalogram
(EEG)
• Computerized Axial
Tomography (CAT)
• Magnetic Resonance
Imaging (MRI)
• Positron Emission
Tomography (PET)
• Functional MRI (fMRI)
Electroencephalogram
• Detects brain waves
through their
electrical output.
• Used mainly in sleep
research.
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PET Scan
Courtesy of National Brookhaven National Laboratories
PET (positron emission
tomography) Scan is a
visual display of brain
activity that detects a
radioactive form of
glucose while the brain
performs a given task.
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Positron Emission Tomography
• Measures how
much glucose the
brain uses.
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MRI Scan
MRI (magnetic resonance
imaging) uses magnetic
fields and radio waves to
produce computergenerated images that
distinguish among
different types of brain
tissue.
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Magnetic Resonance Imaging
• More detailed
picture of brain
using magnetic
field to knock
electrons off axis.
• Takes many still
pictures and turns
images into a movie
like production.
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Computerized Axial Tomography
• function3D XRay of the brain.
• Good for tumor
locating
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Functional MRI
Shows the
tissue and
the
function of
the brain
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The Endocrine System
A system of glands that secrete
hormones.
Similar to nervous system,
except hormones work a lot
slower than neurotransmitters.
Hormones
Neurotransmitters
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The Endocrine System
The Endocrine
System is the body’s
“slow” chemical
communication
system.
Communication is
carried out by
hormones
synthesized by a set
of glands.
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Hormones
Hormones are chemicals synthesized by the
endocrine glands that are secreted in the
bloodstream. Hormones affect the brain and many
other tissues of the body.
For example, epinephrine (adrenaline) increases
heart rate, blood pressure, blood sugar and
feelings of excitement during emergency
situations.
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The Major Endocrine Glands
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Pituitary Gland
Is called the “master gland.” The anterior pituitary
lobe releases hormones that regulate other glands.
The posterior lobe regulates water and salt
balance.
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Thyroid & Parathyroid Glands
Regulate metabolic and calcium rate.
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Adrenal Glands
Adrenal glands consist of the adrenal medulla and
the cortex. The medulla secretes hormones
(epinephrine and norepinephrine) during stressful
and emotional situations, while the adrenal cortex
regulates salt and carbohydrate metabolism.
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Gonads
Sex glands are located in different places in men
and women. They regulate bodily development
and maintain reproductive organs in adults.
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