Download Neuroscience & Behavior The Nervous & Endocrine Systems

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Francis Gall: ill-fated theory that claimed bumps on the skull
could reveal our mental abilities and our character traits.
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The branch of psychology concerned with the links between
biology and behavior.
Biological Psychologists =
Behavioral Neuroscientists =
Neuropsychologists =
Behavior Geneticists =
Physiological Psychologists =
Biopsychologists
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Neurons: basic building block of
the nervous system
Three types of neurons:
 Sensory neurons: carry
information from the sensory
receptors (touch, taste,
auditory, visual, smell) to the
CNS.
 Interneurons: CNS neurons
that communicate between
the sensory and motor
neurons. Our complexity
resides mostly in our
interneuron systems.
 Motor Neurons: carry
outgoing information from
the CNS to muscles or
glands
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Dendrites: the extensions of the cell body (cyton) that receive
impulses and conduct them toward the cell body.
Axon: extension of the neuron that conducts the impulse toward
the terminal branches.
Some axons are insulated by a
layer of fatty tissue called the
myelin sheath which
segmentally encases the
fibers of many neurons.
The myelin sheath increases
the speed at which the
impulse moves down the
axon from one neuron to the
next.
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Nodes of Ranvier: spaces between segments of myelin; also help to
increase the speed of the impulse down the axon
Schwann cells: produce the myelin sheath; important in maintaining
neuron health
 The myelin sheath continues to be laid down until around age 25.
Neural efficiency, judgment, & self-control increases during this
time.
 Multiple sclerosis (MS): the myelin sheath degenerates, slowing
down communication to the muscles, eventually ending in the loss
of muscle control.
Terminal branches: the ending branches from the axon, the tips
of which contain terminal buttons .
 enable the impulse to be carried via chemicals called
neurotransmitters across the gap (synapse) between to
adjacent neurons or to effectors (muscles or glands).
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Sensory information is picked up by sensory receptors and
converted to electrochemical impulses that travel in one
direction from dendrites to terminal branches
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Neurons generate electricity from chemical events, which involves
the exchange of ions (electrically charged atoms).
Resting Potential: the fluid interior of a resting neuron has an
excess of negatively charged ions while the fluid on the outside of
the axon has an excess of positively charged ions.
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Resting potential is associated with a charge of -70 mV.
Threshold: the level of stimulation that will trigger the neuron to
fire
 A neuron will reach threshold and be ready to fire an impulse
at -55 mV causing an action potential
Action Potential: a neural impulse (brief electrical charge that
moves down the axon)
Propagation of an
Action Potential
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Depolarization: More sodium gates open and sodium ions move
into the interior of the axon. This part of the axon now has a
greater positive charge inside the axon relative to the outside.
This causes the next sodium gate to open, moving the impulse
rapidly down the axon.
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Repolarization: As the action potential moves swiftly down the
axon, the potassium channels of the first section open, allowing
K+ ions to move out of the cell. This causes a change in
electrical charge back to the resting potential
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Refractory Period: time it takes for a neuron to regain resting
potential and have the ability to fire again
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Adjacent neurons are separated by gaps called synapses (also
known as synaptic clefts).
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At the end of terminal branches are terminal buttons, which
contain vesicles that manufacture chemical messengers called
neurotransmitters.
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Neurotransmitters carry the impulse across the synapse and
bind to receptor sites on the dendrites of the adjacent neuron,
influencing whether this next neuron will fire or not.
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The sending neuron usually reabsorbs excess neurotransmitter
molecules. This process is known as REUPTAKE.
action potentials
crossing the divide
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Saltatory conduction: When an axon is myelinated, conduction speed
is increased since depolarization jump from node to node.
Excitatory Signals: stimulate the neuron to move toward action
potential
Inhibitory signals: inhibit the neuron from firing.
The sum total of excitatory & inhibitory signals will determine if a
neuron will fire and at what rate.
All-or-none response: either the neuron reaches threshold and fires or
it does not
Intensity of a stimulus is detected by
MORE neurons firing at once and to
fire more often. This does NOT affect
the action potential’s strength or speed.
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Glutamate: major excitatory neurotransmitter involved in
information processing throughout the cortex and especially
memory formation in the hippocampus.
 Both schizophrenia & Alzheimer’s may involve glutamate
receptors.
Antagonists: inhibit or block the receptor sites preventing the
neurotransmitters from binding to the receptor sites.
 Ex: curare – blocks ACh receptors, causing paralysis
Agonists: mimic neurotransmitters, so they are excitatory, binding
to its receptor sites to produce the effects of the neurotransmitter.
 Black Widow venom is an agonist – it floods synapses with ACh,
causing violent muscle contractions, convulsions, and even
death.
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The body’s speedy
electrochemical
communication network,
consisting of the nerve cells of
the central and peripheral
nervous systems.
Central Nervous System (CNS):
brain and spinal cord
Peripheral Nervous System
(PNS): consists of the
autonomic and somatic
nervous systems.
 links the CNS with the
body’s sense receptors,
muscles, and glands.
 links the CNS to the rest of
the body.
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Somatic Nervous System: controls voluntary movements of
the skeletal muscles.
Autonomic Nervous System (ANS): controls the smooth
involuntary muscles and cardiac muscle of the heart. The
ANS is divided into:
 Sympathetic Nervous System: stimulation results in
responses that help your body to deal with stressful
events through such changes as the dilation of your
pupils, release of glucose from the liver, dilation of
bronchi, inhibition of digestive functions, increase in heart
and breathing rates, release of adrenalin from the
adrenal glands, & inhibition of tear glands.
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Parasympathetic Nervous
System: calms the body down
following sympathetic arousal
by:
 Restoring digestive
functions
 Pupils return to normal
size
 Stimulating tear glands
 Decreasing heart &
breathing rates
 Shut down production of
adrenalin
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Brain: has the consistency of
soft-serve yogurt; covered by
membranes called meninges
and is housed in the skull
Spinal cord: protected by
meninges and the spinal
column of bony vertebrae.
 Starts at the base of the
back and extends to the
base of the skull where it
joins the brain.
 The spinal cord is composed
mainly of interneurons and
glial cells (more on these
cells later), which are bathed
by cerebrospinal fluid
produced by the glial cells.
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The central nervous system consists of neurons and glial
cells.
Neurons constitute about half the volume of the CNS and
glial cells make up the rest.
Glial cells provide support and protection for neurons.
The four main functions of glial cells are:
 surround neurons and hold them in place
 supply nutrients and oxygen to neurons
 form insulating sheath around neurons that speed
conduction
 destroy and remove dead neurons
CNS: Spinal Cord
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Spinal Cord: information highway connecting the peripheral
nervous system to the brain
Composed of interneurons
Sensory neurons carry information to the interneurons
spinal cord which routes sensory input to the interneurons
brain for interpretation; the response is carried from the
interneurons of the brain and spinal cord to motor neurons
that end in the effectors which are muscles or glands
 effectors carry out the response directions from the brain.
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Reflexes are simple, automatic, inborn responses to
sensory input.
Examples include the simple knee jerk response and the
simple pain pathway.
Reflex Arc: sensory (afferent) neurons received the stimulus from
your sensory receptors to the spinal cord which immediately
responds with an inborn
protective response to the
motor (efferent) neurons to
react.
 At the same time, the sensory
receptors send the stimulus
to the brain for further
interpretation and response.
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The brain is made up of clusters of neurons called neuron
networks.
With experience, networks can learn as feedback strengthens or
lessens connections that produce certain results.
Each neural network is connected with other neural networks to
perform various tasks.
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A second communication system made up of glands that secrete
hormones into the bloodstream
Hormones are chemical messengers that are mostly manufactured by
the endocrine glands, which are most often produced in one part of
the body and then sent through the blood to affect tissue in other
parts of the body,
Comparison of Endocrine and Nervous Systems:
o Both secrete chemical messengers (neurotransmitters and
hormones) that activate receptors elsewhere in the body
o Hormones are slow in delivery; they must build up in the blood
before they can effect a response. Neuronal response is almost
instantaneous.
o Once a stimulus is over, neuron communication stops. Hormone
shutdown is gradual, slowing with the decrease of hormone levels
in the blood.
Gland
Location
Hormone
Function
Pineal Gland
Pine cone shaped, located midline in the
center of the brain between the 2
cerebral hemispheres
Melatonin
Regulate circadian rhythms (wake, sleep); associated with seasonal
affective disorder
Hypothalamus
Below the thalamus - only brain tissue
with endocrine function
Pituitary Gland
Master Gland; pea shaped located
above the midline to the ear in the core
of the brain
Produces hormones that stimulate or inhibit secretion of hormones from
the pituitary gland
Thyroid Stimulating Hormone (TSH)
Stimulates the thyroid gland to produce thyroxin
Adrenocorticotrophic Hormone (ACTH)
Stimulates the adrenal cortex (outer part) to secrete a group of steroid
hormones called glucocorticoids.
Follicle Stimulating Hormone (FSH)
In females, stimulates the maturation of a follicle and egg inside the
ovary. In males, stimulates sperm production.
Luteinizing Hormone (LH)
Stimulate ovulation in females and the formation of the corpus luteum
from the empty follicle
Antidiuretic Hormone (ADH) (Vasopressin)
Produced by the hypothalamus and secreted by the pituitary. Acts on the
kidneys to increase water retention by decreasing the amount of water
released in the urine.
Human Growth Hormone (HGH)
Increases growth of long bones of the body
Thyroid Gland
2 lobed, located on top of the trachea in
the front neck area
Thyroxin (requires iodine intake)
Stimulates and maintains metabolic activities; lack of thyroxin in
children can cause mental retardation
Parathyroids
Patches of tissue located on the thyroid
Parathormone
Maintains calcium levels in the blood which is necessary for the normal
functioning of neurons.
Adrenal Glands
Pair of glands located on top of the
kidneys
Adrenal Cortex (outer layer):glutocorticoids such as cortisol
Control the body's use of sugar and also help regulate biological
functions during stressful moments.
Adrenal Medulla(inner layer or core): adrenaline (epinephrine) and
norepinephrine
Flight or fight response
Featherlike organ located behind the
stomach, contains the Islets of
Langerhans – specific cells (alpha and
beta cells) that secrete hormones to
regulate blood sugar
Insulin
Decreases blood sugar levels up encouraging the cells and liver to
absorb glucose from blood – imbalances in insulin can lead to diabetes
Glucagon
Increases blood sugar levels by releasing glucose from the liver –
imbalances can lead to hypoglycemia
Ovaries
Pair of glands located near the uterus at
the end of the fallopian tubes
Estrogen
Secondary sex characteristics - breast development, ancillary hair, and
widening of hips. Also involved in thickening of the uterus lining during
the follicle stage of the menstrual cycle.
Testes
Pair of glands located in the scrotum
Testosterone
Secondary sex characteristics - deepening voice, broadening shoulders,
ancillary hair. Also responsible for sperm production
Pancreas