Slide 1
Chapter Two
The Biological Perspective
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Slide 2 Biological Psychology
--branch of psychology concerned with
the links between biology and
behavior.
Neuroscience-
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Slide 3 Neural Communication
Neuron - basic building block of the nervous system.
Components that make up the neuron
• Cell Body- the neurons life support center. Dendrite-branching fibers located on the cell body, that receives information from other neurons.
• Axon-single, slender, fiber extending from the cell body carrying outgoing messages to other neurons, muscles, or glands in the form of neural impulses.
• Tract-group of axons bundled together that carry information to a specific area (i.e. spinal cord tract)
• Myelin sheath- layer of fatty substance made by the oligodendrocytes and schwann cells that insulate certain axons and speeds up the transmission of the neural impulse
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Slide 4 Types of Neurons
• Sensory (afferent) Neurons- neurons that collect messages from sense organs and carry those messages to the spinal cord or brain.
• Motor (efferent) Neurons-neurons that carry messages from the spinal cord or the brain to the muscles and glands
• Interneurons (association) Neurons- neurons that carry messages from one neuron to another.
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Slide 5 Neural Impulse-method of
communication between neurons
• A neural impulse is an electrical
charge that travels down the axon
causing the neuron to fire.
• This electrically charged impulse
allows the neuron to communicate with
other neurons and is called an Action
Potential
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Slide 6 Composition of Intra and Extra-
cellular Fluid• Electrically charged ions on either side of the
membrane. Intra-cellular fluid is predominately negative and extra-cellular fluid is predominately positive in relation to each other.
• Intra-cellular fluid-Higher concentration of:– Negative Ion-(Cation)-A-
– K+
• Extra-cellular fluid-– Na+
– Cl-
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Slide 7 Action Potential
• Resting Potential- small negative electrical charge across the neuron due to the concentration of positive ions on the outside and negative ions on the inside.
• Due to negative electrical charge, the neuron at rest is said to be in a state of polarization.
• Incoming signals from other neurons stimulate receiving neurons at the dendrites through binding of Neurotransmitter.
• When the NT binds, local channels open and briefly change the polarity which results in a graded potential.
• When there are enough graded potentials in succession, channels open allowing positive ions from the outside to enter the interior of the neuron.
• Entrance of the positive ions into the cell body depolarizes the neuron, changing the interior from negative to more positive, setting off a chain reaction that eventually sends an electrical charge (action potential), down the axon.
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Slide 8 Selective Permeability
• Neuron is semi-permeable, meaning some ions can flow freely in and out while other ions cannot due to different types of channels which are open or closed.
• Channels-( open when neuron is at rest)– Both K+ and Cl- channels are open while neuron is at
rest and freely cross the semi-permeable membrane.
– Although the K+ and Cl- ions are free to move in and out of the neuron when it is at rest, whether ions move in or out is influenced by the electrical and concentration of ions.
• Pumps-Na+/K+ pump-3 Na+ ions are pumped out
-2 + ions are pumped in
-helps to maintain the concentration and electrical gradient.
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Slide 9 Voltage gated Channels
• Voltage gated channels are closed when membrane is at rest
• Voltage gated channels begin to open when there is a change in the voltage of the neuron.
• Different voltage gated channels open and close and different times. – Sodium (Na+) channels-open FIRST and more
quickly than K+ initiate depolarization
– Potassium ions (K+)- open later than Na+ gates, but close more slowly-contribute to hyperpolarizationthrough the efflux ( leaving the cell ) of K+ = neuron becomes more negative..
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Slide 10 Propagation of Action Potential
aka. When the Neuron fires.• Neurotransmitters stimulate the neuron via dendrites,
which influence the opening and closing of voltage channels.– Action potential is a sequence of events
– Na+ channels open first, allowing positive ions to rush in and allowing the inside of the neuron to be more positive.
• Graded potential -stimulation via NT is not always enough to open enough gates to cause a change in polarity that is enough to reach threshold. Therefore a brief sudden change in polarity is a graded potential and the neuron remains at rest.
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Slide 11 Action Potential
• Threshold Potential- As more NT stimulates the dendrites, we see a summation of graded potentials, which isisenough to begin the sequence of events that changes the polarity of the neuron when the neuron reaches threshold.
• All or None Response- once the axon reaches threshold it fires, it does not fire at any greater speed or stronger response. It either fires, or it does not.
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Slide 12 Sending the Message to other cells.
• Propagation- the action potential begins at the
axon hillock of the soma and continues down
the axon.
• As Na+ gates open the electrical impulse
continues to travel down the axon.
• As Na+ gates close, no more positive ions can
enter from the Na+ gates.
• K+ gates open later, and stay open longer
which allows K+ to leave the neuron while it has
a positive charge.
• Neuron returns to resting potential
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Slide 13
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Slide 14 C
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Slide 15 Hyperpolarization
• The action potential sequence takes less
than one-thousandth of a second.
• After the action potential fires, the neuron
re-polarizes to its former resting state.
• After the Na+ voltage gated channels
close, the K+ voltage gated channels
remain open, allowing the neuron to be
more negative than resting potential which
is called Hyperpolarization.
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Slide 16 Repolarization
• Absolute Refractory Period- period after the neuron fires when it will not fire again no matter how strong the signal. (Neuron is hyper-polarized)
• Relative Refractory Period-period after firing when the cell is returning to its normal polarized state (negative) and will fire again only if the incoming signal is much stronger than usual.
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Slide 17 Synapse & Synaptic Transmission
• As the action potential travels down the axon it reaches the terminal buttons at the end of the axon.
• Terminal button –tip of the axon from which the neural impulse is released out into the synapse in the form of chemicals called neurotransmitters.
• Synapse- tiny gap between the axon tip of one neuron and the dendrite or cell body of the next neuron.
• Neurotransmitter Release – release of chemicals from axon terminals into the synapse when the neural impulse reaches the end of the axon.
• Vesicles –tiny sacs filled with NT that release the NT into the synapse, where it binds to receptor sites on the receiving neuron.
• Binding of the NT sends a chemical signal which activates the next neuron by binding at the receptor sites.
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Slide 18
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Slide 19 Types of Synapses
• Excitatory Synapse-synapse at which a
neurotransmitter causes the receiving cell
to fire.
• Inhibitory Synapse-synapse at which a
neurotransmitter causes the receiving cell
to stop firing cessation of pain signal.
• It is not the NT that is excitatory or
inhibitory, but rather the synapse to which
the NT binds.
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Slide 20 Drugs and Neurotransmitters
• Drugs are synthesized molecules that are
similar enough in shape to a specific
neurotransmitter, so that the drug can fit into
the receptor site.
• Agonists-chemical substances that can mimic
or enhance the effects of the
neurotransmitters on the receptor site of the
next cell.
• Antagonist-chemical substance that blocks or
reduces the cells response to the action of
other chemicals or neurotransmitters.
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Slide 21 Drug Effects
• AgonistExcitatory synapse
• AgonistInhibitory synapse
• AntagonistExcitatory synapse
• AntagonistInhibitory synapse
• Re-uptake
• Re-uptake inhibitor
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Slide 22 How Neurotransmitters influence Us
• Acetylcholine (Ach)-triggers muscle contraction.
• Dopamine-NT involved with voluntary movement, learning, memory and emotions.
• Serotonin_primarily involved in mood and depression. Also important in regulation of sleep and appetite.
• Endorphins (endogenous morphine)-natural opiate released in response to pain and vigorous exercise
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Slide 23
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Slide 24 Central Nervous system
• Includes all of the neurons in the brain and
spinal cord. Two main areas of the CNS:
– Brain
– Spinal Cord
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Slide 25 Subdivisions of the brain
• Central Core- earliest part of the brain to develop.
– Hindbrain: point where the spinal cord enters the skull. Contains the medulla, pons and cerebellum• Medulla-controls basic body functions such as
breathing, heart rate, and blood pressure.
• Pons- maintains the bodies sleep wake cycle
• Cerebellum-sense of balance and coordinating the bodies actions
– Thalmus-major sensory relay center, integrates and shapes incoming signals
– Hypothalamus-governs hunger thirst, sex drive and body temperature.
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Slide 26
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Slide 27
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Slide 28 Limbic System
• Located on top of and around the central
core.
• Composed of a set of structures that impose
additional controls over instinctive behaviors
regulated by the central core.
• Associated with emotions such as fear and
aggression, and drives such as food and sex
– Hippocampus-formation of new memories
– Amygdala-governs emotions related to self
preservation
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Slide 29 Cerebral Cortex
• More highly developed in humans than in any other animal.
• Literally covers the central core and limbic system
• Divided into two cerebral hemispheres, right and left. Each hemisphere is further divided into four lobes.
• The central fissure runs sideways form ear to ear and separates the primary somatosensory cortex from the primary motor cortex.
• Primary somatosensory cortex-receives sensory messages from the entire body.
• Primary motor cortex-sends messages from the brain to muscles and glands
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Slide 30
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Slide 31 Functional Lobes of the Cerebral Cortex
Four lobes, two in each hemisphere, for example, right and left frontal lobe, etc.
Occipital - Receives and processes visual information. Damage: “blind sight”
Temporal -Regulates hearing, smell, balance and equilibrium, emotion and motivation, some language comprehension and complex visual processing such as recognizing faces. Damage: prosopagnosia
Parietal – Receives sensory information from all over the body and registers these messages in the primary somatosensory cortex. Regulates spatial and mathematical abilities. Damage: neglect.,
Frontal lobe- executive function--receives and coordinates messages from the other three lobes. Also appears to play a key role in personality, motivation, persistence, affect (mood) and character traits such as moral character: Damage: Phineas Gage
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Slide 32 Spinal Cord
• Consists of soft jelly-like bundles of axons, protected by the vertebrae
• Two pathways-descending motor, ascending sensory
• Motor-carries information from the brain controls internal organs, muscles, and autonomic nervous system
• Sensory-carries information from the organs and extremities to the brain.
• Reflex-circuit that does not require input from the brain…sensory fibers send info to the spinal cord where interneurons pass info to motor fibers causing withdrawl reflex, before brain has registered what has happened.
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Slide 33
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Slide 34 Peripheral Nervous system-
• (def). the sensory and motor neurons that
connect the CNS to the rest of the body.
Autonomic
• Sympathetic
• Parasympathetic
Somatic-
•
•
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Slide 35 ENDOCRINE SYSTEM
• (def)-chemical communication system,
slower than electrical, consists of glands that
secrete hormones into the blood- stream.
• Hormones-
• Endocrine glands-
– Thyroid gland -
– Parathyroid-
– Pineal gland-
– Pancreas-
– Pituitary gland-
– Adrenal gland-
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Slide 36
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