UNIT 2 - BIOLOGY PPT 9.19.12.pptx

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Unit 2: Biology

General Facts

• _{Everything psychological is} simultaneously biological. • _{Plato – correctly located the}

mind in the head.

• _{Aristotle (Plato’s student) –} thought the mind was in the heart.

• _{Franz Gall – phrenology in} early 1800s.

General Facts

• _{Different parts of brain do} control different aspects of behavior.

• _{Biological Psychologists –} study links between

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Unit 2: Biology

Neurons (nerve cells)

• _{Sensory – carry messages} from body to brain and spinal cord.

• _{Motor – carry messages} from brain and spinal cord to body.

• _{Interneurons – those within} the brain and spinal cord ONLY.

Neurons

• _{Dendrites – receive messages}

and send impulses toward cell body.

• _{Axon – passes messages along}

to other neurons.

• _{Myelin Sheath – fatty tissue}

that insulates the axon

• _{Multiple Sclerosis results when}

myelin sheath degenerates = eventual loss of muscle

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Neurons

• _{Human brain is more}

complex than a computer, but slower at executing simple responses.

Neurons

• _{Action Potential – a neural} impulse; a brief electrical charge that travels down an axon.

• _{Resting Potential – ions} having a

positive-outside/negative-inside state.

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Neurons

• _{When a neuron fires, axon} opens it’s gates and is

flooded with + charged sodium ions; this

depolarizes that part of atom and causes a chain reaction allowing other positively charged ions inside.

Neurons

• _{Refractory period – a resting} pause when the neuron

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Neural Signals

• _{Excitatory – like a neuron’s} accelerator

• _{Inhibitory – like a neuron’s} brakes

• _{When excitatory minus} inhibitory still meets a minimal threshold, an

action potential is triggered.

Neural Response

• _{A neuron’s reaction is an} all-or-none response: like guns, neurons either fire or don’t fire.

• _{A strong stimulus (a punch} rather than a tap) can trigger more neurons to fire, and fire more often

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How Neurons Communicate

• _{Sherrington – discovered} the synapse (small gap between 2 neurons).

• _{Synapse (synaptic gap,} synaptic cleft) is less than one millionth of an inch wide

• _{When an action potential} (neural message) reaches the knoblike terminals at an axon’s end, it triggers the release of chemical

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• _{Neurotransmitters shoot} across synapse and bind to receptor sites of receiving neuron.

• _{Reuptake – when the}

sending neuron reabsorbs the excess

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Neurotransmitters

• _{Acetylcholine (ACh) –}

enables muscle action, learning, and memory.

• _{Dopamine – influences}

movement, learning, attention, and emotion

• _{Serotonin – affects mood,}

hunger, sleep, and arousal

*See Table 2.1 on pg. 53

• _{Norepinephrine – helps} control alertness and arousal.

• _GABA

(gamma-aminobutyric acid) – a major inhibitory

neurotransmitter.

• _{Glutamate – a major}

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• _{ACh blocked = paralysis} • _{ACh flooding = violent}

muscle contractions,

convulsions, maybe death. (This is the effect of the venom of the black widow spider).

Drugs and Neurotransmission

• _{Morphine is an opiate drug} that elevates mood and

eases pain.

• _{Endorphins = endogenous} morphine (“produced

within”)

• _{Both morphine and}

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Drugs and Neurotransmission

• _{When flooded with opiate} drugs like heroin and

morphine, the brain may stop producing its own natural opiates.

• _{Withdrawal of drug then} leads to intense discomfort. • _{Drugs and other chemicals}

affect the brain at synapses.

Agonists and Antagonists

• _{Agonist – molecule similar} to a neurotransmitter that mimics it’s effects (ex.

Morphine mimics endorphins)

• _{Antagonist – blocks a}

neurotransmitter’s function (ex. Botulin blocks ACh

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Poisons

• _{Botulin – poison can form in} improperly canned food; causes paralysis by blocking ACh release. (also used in smoothing wrinkled skin). • _{Curare – used in poison}

hunting darts; occupies and blocks ACh receptor sites and leaves the animal paralyzed.

Nervous System

• _{Central Nervous System} (CNS) – brain and spinal cord.

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Peripheral Nervous System

• _{Autonomic – controls} self-regulated action of internal organs and glands.

• _{Somatic – controls}

voluntary movements of skeletal muscles; also called skeletal nervous system.

Autonomic Nervous System

• _{Sympathetic (arousing) –} arouses the body,

mobilizing its energy in stressful situations.

• _{Parasympathetic (calming) –} calms the body, conserving it’s energy.

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Central Nervous System

• _{Human have approximately:} 40 billion neurons, each

having 10,000 contacts with other neurons, with about 400 trillion synapses.

Neural Networks

• _{“Neurons that fire together} wire together.”

• _{Neurons network with}

nearby neurons with which they have short, fast

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Neural Networks

• _{Reflex – a simple, automatic} response to a sensory

stimulus, such as a knee-jerk reaction.

• _{Simple pain reflex pathway} runs through spinal cord and right back out; body reacts prior to message ever reaching the brain.

Spinal Cord

• _{Information travels to and} from the brain by way of the spinal cord.

• _{If top of spinal cord was}

severed, you would not feel pain or pleasure.

• _{To produce bodily pain or} pleasure, sensory

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Endocrine System

• _{Endocrine System - The} body’s slow chemical

communication system; a set of glands that secrete

hormones into the bloodstream.

• _{Hormones – chemical}

messengers manufactured by the endocrine system, travel through bloodstream, and affect other tissues.

• _{Endocrine messages are} slower than neural

messages because they travel in the bloodstream; they also tend to outlast the effects of neural messages; effects “linger” in the

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• _{Pituitary gland – “master} gland” of system; controlled by the hypothalamus, the pituitary regulates growth and controls other endocrine glands.

• _{Adrenal glands – sit atop of} kidneys; release epinephrine and norepinephrine

(adrenaline and noradrenaline)

*See Figure 2.11 on pg. 59

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The Brain

• _{Brain + Body = Mind}

• _{The mind is what the brain} does.

• _{By lesioning (destroying)} parts of the brain of a rat, neuroscientists have begun mapping brain functions.

Brain Imaging Techniques

• _{Electroencephalogram} (EEG) – an amplified

recording of the waves of electrical activity that

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• _{PET Scan (Positron Emission} Tomography) – a visual

display of brain activity that detects where a radioactive form of glucose goes while the brain performs a given task.

• _{MRI (Magnetic Resonance} Imaging) – a technique that uses magnetic fields and radio waves to produce

computer-generated images of soft tissue. MRI scans

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• _{fMRI (functional MRI) – a} technique for revealing bloodflow and , therefore, brain activity by comparing successive MRI scans. fMRI scans show brain function. • _{Where the brain is}

especially active, blood goes.

Older Brain Structures

• _{Human brain weighs}

approximately 1/45 of total body weight.

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Brainstem

• In order from top down…

• _{Thalamus – the brain’s sensory}

switchboard, located atop of brainstem.

• _{Reticular formation – nerve}

network in brainstem that helps control arousal.

• _{Pons (part of brainstem) –}

helps coordinate movement.

• _{Medulla (part of brainstem) –}

heartbeat & breathing.

Brainstem

• _{Brainstem is a crossover}

point where most nerves to and from each side of brain connect with the body’s opposite side.

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Cerebellum

• _{Cerebellum means “little} brain” and is located at the rear of the brainstem;

processes sensory input and coordinates movement

output and balance.

Damage to Cerebellum…

• _{Difficulty judging time} • _{Difficulty controlling}

emotions

• _{Difficulty walking, keeping} balance, shaking hands

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Limbic System

• _{“Limbus” means “at the} border” of old brain

structures and newer cerebral hemispheres.

• _{Includes the hippocampus,} amygdala, and

hypothalamus; located in the cerebral hemispheres and associated with

emotions and drives.

Limbic System

• Hippocampus – processes memory.

• _{Amygdala – influences} aggression and fear

• _{Hypothalamus – “hypo” means} “just below”; directs

maintenance activities (eating, drinking, body temp); helps govern endocrine system via pituitary gland; linked to

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Limbic System

• _{Also located in the}

hypothalamus is a reward center or pleasure center.

Brain Structures and Functions

• _{See Figure 2.22 on pg. 67 of} text.

• _{Older brain networks}

sustain basic life functions (in brainstem).

• _{Newer brain networks do} specialized work like

perceiving, thinking, and speaking (in cerebral

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Cerebral Cortex

• _{Cerebral cortex is like the} bark of a tree, covering the brain; made up of

interconnected neural cells, covers cerebral

hemispheres, and is the

body’s ultimate control and information processing

center.

Cerebral Cortex

• _{Glial Cells (Glia) – support,} nourish, and protect

neurons.

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Lobes

• _{4 Lobes in each} hemisphere:

• _{Frontal – behind forehead} • _{Parietal – at top and rear} • _{Occipital – at back of head} • _{Temporal – just above ears}

Localization of Control

• _{The brain devotes more} cortical space to sensitive areas and areas requiring precise control.

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Neural Prosthetics

• _{Placing an electrode on the} motor cortex of a subject has allowed the subject to think of a body movement and the body has

responded.

Visual and Auditory Cortex

• _{Visual Cortex – located in} the occipital lobe at rear of brain; receives input from the eyes.

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Association Areas

• _{These are areas of the}

cerebral cortex that are not involved in primary motor or sensory functions; they are involved in higher

mental functions such as learning, remembering, thinking, and speaking.

• _{Where sensory inputs are} linked with stored

memories.

• _{Association Areas cannot be} neatly mapped.

• _{They are found in all 4 lobes} • _{In Frontal Lobes – A.A.}

enable judgment, planning, and processing new

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• _{Frontal lobe damage can} alter personality (Phineas Gage example – pg. 72). • _{Normally soft spoken Gage}

was now irritable, profane, and dishonest.

• _{Gage’s moral compass was} disconnected from his

behavior.

• _{In parietal lobes, A.A.}

enable mathematical and spatial reasoning.

• _{In the right temporal lobe,} A.A. enable facial

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• _{Complex mental functions} do not reside in any one place.

Plasticity

• _{Plasticity – the brain’s ability} to change, especially during childhood, by reorganizing after damage or by building new pathways based on

experience.

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Plasticity

• _{Blindness or deafness makes} unused brain areas available for other uses. (ex. Some deaf people have enhanced peripheral vision).

• _{It’s possible for an amputee} to experience feeling in the limb that is no longer

connected to the body. Huh?

Neurogenesis

• _{Mice and humans can}

regenerate new brain cells. • _{Master stem cells that can}

develop into any type of brain cell have been

discovered in the human embryo. (Controversy)

• _{Natural promoters: exercise,} sleep, non-stressful but

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Our Divided Brain

• _{Lateralization = hemispheric} specialization

• _{Left hemisphere: reading,} writing, speaking,

arithmetic reasoning, understanding.

• _{Left hemisphere once}

thought of as “dominant” or “major”

Splitting the Brain

• _{Corpus Callosum – large} band of neural fibers

connecting the two brain hemispheres and carrying messages between them. • _{Severing corpus callosum}

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• _{Speech is controlled by the} left hemisphere; when

corpus callosum is severed, something appearing in the left visual field may be

recognized but NOT put into words by the subject.

• _{Right Hemisphere –}

emotion processing and social conduct

• _{Split brain patients can} simultaneously draw two distinct pictures, one with each hand.

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Right-Left Differences

• _{Right Hemisphere –}

perceptual tasks, excels at inferences, modulate

speech to make meanings clearer, sense of self,

• _{Left Hemisphere – speaking,} calculating, processing sign-language for deaf people, quick interpretations of language,

Handedness

• _{90% of us are right-handed} • _{More males than females are}

left handed

• _{Almost all (96%) of}

right-handers process speech in left hemisphere (slightly larger hemisphere)

• _{Only (70%) of left-handers}

process speech in left

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Handedness

• _{Right-handers prevail in all} human cultures.

• _{90% of fetuses such right} thumb.

• _{Either genes or some}

prenatal factors influence handedness.

Handedness

• _{Left-handers have more} reading disabilities,

allergies, and migraines. • _{In Iran, lefties outperform}

righties in all subjects. • _{Lefties more common}

musicians, mathematicians, pro baseball and cricket

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Conclusion

• _{“A brain simple enough to} be understood is too simple to produce a mind able to understand it.”