U.1 – Biological bases of behaviour

Ch. 4 – Biological Bases of Behaviour 

• Genetics

  • Genetic predisposition: the increased chance of developing a specific trait or condition due to one’s genetic code

• Genetic concepts

  • 46 chromosomes in 23 pairs

  • DNA: Deoxyribonucleic acid

  • Genes: discrete segments that control specific protein production for human traits

    • Dominant

    • Recessive

• Twins

  • Identical twins: monozygous bcuz they develop from one fertilized egg

    • Share the same genetic makeup

    • A study was done by Thomas Bouchard with 100 identical twins who were given up for adoption

• Chromosomal abnormalities

  • Sex is determined by the 23rd pair of chromosomes

    • XY-male

    • XX-female

  • Chromosomes can fail to combine or combine in a weird way

    • Ex: babies with turner’s syndrome are born with only a single X chromosome in the spot where the 23rd pair should be

    • Can cause physical abnormalities

      • Short stature, webbed necks, differences in physical sexual development

    • Klinefelter’s syndrome: XXY

      • Minimal sexual development and extreme personality traits

    • Down syndrome: extra chromosome on the 21st pair

      • Physical characteristics: round face, shorter dingers and toes, slanted eyes far apart, intellectual disability

• Neuroanatomy

  • The study of the parts and function of neurons.

  • Neurons: individual nerve cells; make up the entire nervous system

    • Dendrites: rootlike parts of the cell that stretch out from the cell body

    • Cell body: (soma) contains the nucleus and other parts of the cell needed to sustain its life

    • Axon: a wirelike structure ending in the terminal buttons that extends from the cell body

    • Myelin sheath: a fatty covering around the axon of some neurons that speeds neural impulses. Multiple sclerosis occurs when the myelin sheath deteriorates around neurons, interfering with neural transmission

    • Terminal buttons: (end buttons, terminal branches of axons, synaptic knobs) the branched end of the axon that contains neurotransmitters

    • Neurotransmitters: chemicals contained in terminal buttons that enable neurons to communicate. Neurotransmitters fit into receptor sites on the dendrites of neurons like a key fits into a lock

    • Synapse: the space between the terminal buttons of one neuron and the dendrites of the next neuron

  • How a neuron fires

    • Different parts work in sequence to send a message (neural transmission)

    • Resting potential: a neuron has an overall slightly negative charge (-70mv) because negative ions are within the cell and mostly positive ions are surrounding it

    • Cell membrane → selectively permeable

    • Threshold: enough neurotransmitters are received

    • The cell membrane of neuron B becomes permeable and positive ions rush into the cell (charge changes to +40mv)

    • Action potential: electric message firing → 120m/sec

    • When the charge reaches the terminal buttons of neuron B, the buttons release their neurotransmitters itn othe synapse

    • All or none principle: neuron either fires completely or not

      • If the dendrites of a neuron receive enough neurotransmitters to push the neuron past its threshold, the neuron will fire completely

    • Depolarization: same amount fired each time because the cell fires due to the resting potential of the cell

• Neurotransmitters

  • Chemicals held in the terminal buttons that travel in the synaptic gap between neurons 

  • There are different types:

    • Excitatory: they excite the next cell into firing

    • Inhibitory: they inhibit the next cell from firing

• Nervous system

  • Need 2 sets of wires

    • One to take information to the brain

    • One to take instructions back from the brain to the muscles

  • Sensory neurons: afferent neurons; take information from the senses to the brain

  • Interneurons: information → brain/spinal cord → interneurons (associatation neurons) take messages and send them elsewhere in the brain or onto efferent neurons

  • Motor neurons: efferent neurons take information from the brain to the rest of the body

  • Central nervous system CNS: consists of brain and spinal cord—all the nerves housed within bone

  • Typical peripheral nervous system transmission: toe → neuron → spine (afferent nerves) → spinal cord → brainstem → brain’s sensory cortext THEN motor cortex send impulses → spinal cord → muscles (effrent nerves)

• Side notes: Reflexes: reflex arcs: leg jerking without conscious control

  • Sensory information processed by the spine

  • Another ex: touching hot or cold

  • Has adaptive values  → pass onto children

  • Peripheral nervous system PNS: consists of all the nerves in body that are not part of the CNS → all nerves not in bone

    • Somatic nervous system: controls voluntary muscle movements (motor cortex)

    • Autonomic nervous system: controls the automatic functions of body → heart, lungs, internal organs, glands, etc → stress nerves (fight or flight)

      • Sympathetic nervous system: respond to stress (fight or flight response) it accelerates heart rate, blood pressure, respiration, but conserves resources needed (digestion)

      • Parasympathetic nervous system: opposite job of the above. Carries messages that cause body activities to slow down and return the body to homeostasis 

• Endocrine system: system of glands that secrete hormones that affect many different biological processes in bodies; is controlled by hypothalamus

• Adrenal glands: produces adrenaline (epinephrine) signals the rest of the body to prepare for fight or flight

  • Is connected to heart rate and blood pressure (autonomic nervous system)

• Ovaries and testes: produce sex hormones

  • Extrogen for females

  • Testosterone for males

• Brain (ways of studying it)

  • Accidents: phineas gage was in an accident that damaged the front part of his brain

    • Personality change was one of the symptoms after the accident; more emotional and impulsive

  • Lesioning: removal or destruction of part of the brain

    • Doctors perform this as a treatment option

    • Researchers examine behavior changes after these surgeries to infer the function of that part of the brain

    • Ex: frontal lobotomies for mentally ill

  • Electroencephalogram (EEG): detects brain waves → different stages of dreams are detected

  • Computerized axial tomography (CAT or CT): type of x ray. Uses several x ray cameras that rotate around the brain and combine all the picture into a detailed three-dimensional picture of the brain’s structure

  • Magnetic Resonance Imaging (MRI): uses magnetic fields to measure the density and location of brain material

  • Positron Emission Tomography (PET): lets researchers see what areas of the brain are most active during certain tasks

    • How much of certain chemical parts of the brain are using

    • Higher activity levels are shown through different colors (red → high, blue → low)

  • Function MRI (fMRI): technology that combines elements of the MRI and PET scans → can show details of brain structure with information about blood flow in the brain (brain structure + brain activity)

• Brain Structure/Function

  • Hindbrain

    • located on top of the spinal cord

    • Controls the basic biological functions to live

    • Important structures in it: medulla, pons, cerebellum

  • Medulla (oblongata): controls blood pressure, heart rate, breathing → located above the spinal cord

  • Pons: connects the hindbrain with the midbrain and forebrain → located just above the medulla and toward the front

  • Cerebellum: coordinates habitual muscle movement, such as tracking a target with eyes or moving fingers when playing the saxophone → cerebellum means little brain and is located at the bottom rear of the brain

  • Midbrain

    • Located just above the structure in the hindbrain, but still below areas categorized as the forebrain

    • Coordinates simple movements (muscle movements) with sensory information

    • Reticular formation: netlike collection of cells throughout the midbrain that controls general body arousal and the ability to focus attention (without this people go into a coma)

  • Forebrain

    • Controls what we think of as thought and reason

    • The area includes the thalamus, hypothalamus, amygdala, hippocampus

  • Thalamus: responsible for receiving the sensory signals coming up the spinal cord and sending them ot the appropriate areas in the rest of the forebrain → on top of the brain stem

  • Hypothalamus: controls metabolic functions like body temperature, sexual arousal, hunger, thirst, endocrine system, biological rhythms

  • Amygdala: Structures near the end of each hippocampal arm

    • Vital to experiences of emotion

  • hippocampus: two armlike structures surrounding the thalamus 

    • Vital to memory system → memories are processed through this area and then sent to other locations in the cerebral cortex for permanent storage

    • Memories must pass through this area first 

    • Damage to this area → unable to retain new information

• Cerebral Cortex

• Gray wrinkled surface of the brain

• Thin (1mm) layer of densely packed neurons

• Pruning: The dendrites of the neurons in the cerebral cortex grow and connect with other neurons

• Wrinkles are called fissures

• Smooth brain vs wrinkled brain

• Think of it as 8 different lobes; 4 on each hemisphere

  • Frontal, parietal, temporal, occipital

• Association area: cerebral cortex area that is not associated with receiving sensory information or controlling muscle

  • Responsible for sophisticated thoughts like judgement and humor

• Hemistpheres

  • Cerebral cortex is divided into 2 hemispheres → left and right

  • Left hemisphere: gets sensory messages and controls the motor functions of the right half of the body

  • Right hemisphere: gets sensory messages and controls the motor functions of the left half of the body

  • Hemispheric specialization/ brain lateralization: the left hemisphere dominates language and analytical tasks, while the right hemisphere excels in spatial abilities, emotion, and holistic processing

  • Split-brain patients: patients whose corpus callosum (nerve that connects the two hemispheres) is cut to treat epilepsy → neuropsychologists Roger Sperry and Michael Gazzaniga 

  • Split-brain patients cannot speak about info received exclusively in their right hemisphere

• Frontal lobes: largest areas of the cerebral cortex located at the top front part of the brain behind the eyes

  • Prefrontal cortex: front of the frontal lobe → direct thought process

    • Act as the brain’s central executive, predicting consequences, pursue goals, maintain emotional control

    • Ex: phineas gage

  • Frontal lobe—left hemisphere: language processing

  • Broca’s area: responsible for controlling the muscles involved in producing speech

  • Wernicke’s area located in the temporal lobe

  • Motor cortex: think vertical strip at the back of the frontal lobe

    • Sends signals to muscles, controlling voluntary movements

    • Top of the body is controlled by the bottom of this cortex (vice versa)

• Parietal lobe: located behind the frontal lobe but still on the top of the brain

  • Contains somatosensory cortex: located right behind the motor cortex in the frontal lobe

    • Vertical strip that receives incoming touch sensation from the body

    • Acts similarly to the motor cortex

    • Phantom limb syndrome: if an individual loses a limb, they may still perceive sensation from the lost limb

• Occipital lobe: located at the very back of the brain, farthest from the eyes

  • Contains major eye functions (eye → visual cortex)

  • Impulses from the retinas in our eyes are sent to the visual cortex to be interpreted

  • Impulses from the right half of each retina are processed in the visual cortex in the right occipital lobe (same thing happens with the left side)

• Temporal lobe: process sound sensed by ears

  • Sound waves are processed by the ears → turn into neural impulses → interpreted in auditory cortices

  • Not lateralized: sounds received from either ear is processed in both hemisphere of the brain

  • Second language: located in the temporal lobe

  • Wernicke’s area is involved with linguistic processing through both written and spoken speech

  • Damage to this area would affect the understanding of language

• Brain plasticity

  • Other parts of the brain can adapt to a person's different functions if needed

  • Since dendrites grow throughout one’s life, if one part of the brain is damaged, dendrites might be able to make new connections in another part of the brain that would be able to take over the functions usually performed by the damaged part of the brain

Ch. 5 – States of Consciousness

• Mere exposure effect: occurs when one prefers stimuli one has seen before over novel stimuli, even if one does not consciously remember seeing the old stimuli

• Priming: research participants respond more quickly and/or accurately to questions they have seen before, even if they do not remember seeing them

• Blind sight can demonstrate levels of consciousness: some people who report being blind can nonetheless accurately describe the path of a moving object or grasp objects they say they cannot see

Levels of consciousness

Drugs:

• Psychoactive drugs: chemicals that change the chemistry of the brain + induce an altered state of consciousness

• Placebo effect: expected effects of the drug if they think they ingested it, even if they did not

• blood -brain barrier: The brain is protected from harmful chemicals in the bloodstream by thicker walls surrounding the brain’s blood vessels

• Agonists: Drug molecules mimic naturally occurring neurotransmitters in the brain.

• Antagonists: drugs that block neurotransmitters

• Other drugs prevent natural neurotransmitters from being reabsorbed back into a neuron

  • Ex: Prozac - selective serotonin reuptake inhibitor

• Drugs can cause tolerance or addiction.

  • A physiological change that produces a need for more of the same drug in order to achieve the same effect

• Withdrawal symptoms: headache, dehydration, night sweats

  • Can be psychological, physical, or both

Drug categories:

1. Stimulants: caffeine, cocaine, amphetamines, nicotine

   1. Arouse the autonomic nervous system (heart rate, breathing)

   2. Sense of euphoria

   3. All drugs this category produce withdrawal effects

2. Depressants: alcohol, barbiturates, anxiolytics (antianxiety) → diff name: valium

   1. A euphoric rush + withdrawal effects

   2. Inhibitors of the different brain regions causes behavioral changes

   3. Slow down autonomic nervous system

3. Hallucinogens: LSD, peyote, psilocybin, mushrooms, marijuana

   1. Changes in perception of reality

   2. Sensory hallucination (it’s in the name!), loss of identity, vivid fantasies

   3. Can persist in the body for weeks

   4. Reverse tolerance: second dose may be less than the first but cause the same or greater effects

   5. Less predictable side effects

4. Opiates: morphine, heroin, methadone, codeine, fentanyl

   1. Similar chemical structure as opium → derived from poppy plant

   2. Adonists for endorphins

   3. Painkillers and mood elevators

   4. Drowsiness and euphoria

   5. Fent: very strong that even minute quantities mixed in with other drugs can be lethal

Sleep: one of the states of consciousness

• Sleep cycle

• Circadian rhythm: metabolic and thought process pattern

  • Sleep is a part of this

  • Researchers use eeg (electroencephalogram) to record brain activity during sleep

• As we sleep, we go through multiple stages of consciousness

• Sleep onset: periode of falling asleep

  • Brain produces alpha waves (drowsy but awake)

  • Mild hallucination

• non-REM (NREM)

  • Stage 1 & 2: awake in these stages; brain produces theta waves (high frequency, low-amplitude waves

  • Theta waves get slower and higher in amplitude as we go from wakefulness and through NREM stage 1 & 2.

  • In stage 2, eeg show sleep spindles

    • Short bursts of rapid brain waves

  • Stage 3: delta sleep, deep, slow wave sleep

    • The slower the wave, the deeper you sleep

    • Release delta waves in this stage

    • A person in delta sleep is very difficult to wake up

    • This stage is important to replenish the body’s chemical supplies

    • Release growth hormones in children 

  • Increase exercise to increase sleep

  • Cycle repeats

• REM: rapid eye movement (paradoxical sleep)

  • Brain waves appear active and intense as they do when we are awake

  • Dreams occur in this stage

  • REM rebound: experiencing more and longer periods of REM

  • The more stress experienced during the day, the longer REM sleep will be

  • As we get closer to morning, we spend more time in NREM stages 1 and 2 and in REM sleep and less in NREM stage 3

  • Babies spend more time sleeping but also spend more time in REM sleep

• Sleep disorders

  • Insomnia: most common sleep disorder—affects 10% of the population

    • Can’t sleep at night

    • Is treated by reducing the intake of caffeine or other stimulants, exercising, and maintaining a consistent sleep pattern

  • Narcolepsy: occurring in less than 0.001% of the population

    • Suffer from periods of intense sleepiness and may fall asleep at unpredictable and inappropriate times (REM sleep)

    • Can be treated with medication and changing sleep patterns

  • Sleep apnea: common as insomnia

    • Causes a person to stop breathing for short periods of time during the night and wake up slightly to gasp for air and then sleep continues

    • Overweight men are at a higher risk

    • Can be treated with a respiration machine

  • Night terrors: common in young children

    • Most don’t remember

    • related to somnambulism (sleepwalking)

Dreams

• Dreams are a difficult research area

• Rely of self-reports of other people

• Activation-synthesis theory: explains dreams as a biological phenomenon

  • Brain imaging is used to see the brain activity when someone is sleeping

  • This theory proposes dreams are nothing more than the brain’s interpretations of what is happening physiologically during REM sleep 

• Information processing theory of dreaming: we use dreams to process the events of the day

  • Points out that stress during the day will increase the number and intensity of dreams

  • The function of REM may be to integrate the information processed during the day into our memories

• Consolidation theory: one of the functions of dreams might be to help us encode events and information in our short-term memory into our long term memory

Ch. 6 – Sensation

• Transduction: the signals are transformed into neural impulses

• Neural impulses travel first to the thalamus and then on to different cornices of the brain (sense of smell is an exception to this rule)

• Sensory adaptation: decreasing responsiveness to stimuli due to constant stimulation

• Cocktail party effect: talking with a friend, and someone across the room says your name, your attention will involuntarily switch across the room

• Synesthesia: the activation of one sense, like seeing a colour, activates another sense, like hearing a specific sound - vice-versa

• Prosopagnosia: the inability to recognize faces

Energy sense

Vision

1. Gathering light

   1. Key word: wavelength

In the order of shortest to longest lengths:

Ultraviolet - X-ray - visible - infrared - microwave - radio wave

2. Different wavelengths within the visible light spectrum appear as different hues

In the order of longest to shortest:

Red - orange - yellow - green - blue - indigo - violet (Roy G. Biv)

3. Objects appear that color because they reflect that wavelength

4. Wave amplitude (Height): intensity → higher the wave the more energy it contains and the brighter the color we perceive

2. Within the eye

   1. Reflected light enters the cornea

   2. Cornea then focuses the light

   3. Light goes through the pupil

   4. Iris: muscles that control the pupil

   5. Accommodation: amount of light let in the eye is controlled by the dilation and contraction of the iris

   6. Light that enters the pupil is focused by the len—curved and flexible

   7. Defect in the lens can result in nearsidedness or farsidedness

3. Transduction

   1. Refers to the translation of incoming stimuli into neural signals

   2. Transduction occurs when light activates the neurons in the retina

   3. First layer of the cells is called the photoreceptors

      1. Cones: colors

      2. Rods: black and white

   4. Rods outnumber cones by 20:1

   5. Cones are concentrated toward the center of the retina

   6. Fovea has the highest concentration of cones

   7. Peripheral vision at extremes relies on rods and is mostly in black and white

   8. The information then passes through bipolar cells

   9. Then comes ganglion cells

   10. Axons of the above cells make up the optic nerve which leaves the retina

   11. In optic nerve, there are no rods or cones (blind spot)

   12. The divided optic nerves cross each other → optic chiasm

4. In the brain

   1. The visual cortex of the brain receives the impulses from the cells of the retina, and the impulses activate feature detectors.

   2. David hubel; torsten wiesel discovered groups of neurons in the visual corte respond to different types of visual images

   3. Visual cortex has feature detectors

Color vision:

• Trichromatic theory: hypothesizes that we have three types of cones in the retina and that each type detects a different primary color of light: blue, red, green

  • This theory cannot explain afterimages and color blindness

  • Dichromatism: cannot see either red/green, blue/yellow

  • Monochromatism: black and white

• Opponent process theory: states that the sensory receptors arranged in the retina come in pairs (red/green) (yellow/blue) (black/white)

  • If one sensor is stimulated, its pair is inhibited from firing

  • Explains afterimage and color blindness

Hearing:

• Auditory sense uses waves; vibrations in the air

• Have amplitude and frequency. 

• Amp: height of waves → loudness (decibels)

• Frequency: length of the waves → pitch (megahertz)

• Sound waves → outer ear/pinna → ear canal → eardrum/tympanic membrane → attached to ossicles → hammer/malleus → anvil/incus → stirrup/stapes → oval window → cochlea (has fluid) → basilar membrane → hair cells → corti (neurons activated by the movement of hair cells)

• Fluid moves, hair cells move, transduction occurs

• Corti fires, impulses are then transmitted to the brain through auditory nerve

• Sound localization: determining where the sound originated from the loudness in each ear

Pitch theory:

• Place theory: hair cells in the cochlea respond to different frequencies of sound based on where they are located in the cochlea

• Frequency theory: we sense pitch because the hair cells fire at different rates (frequencies) in the cochlea

Deafness:

• Conduction deafness: occurs when something goes wrong with the system of conducting the sound to the cochlea

• Nerve deafness/sensorial deafness: occurs when the hair cells in the cochlea are damaged, usually by loud noise 

• Hair cells do not regenerate → no treatment

Touch: 

• We have many different types of nerve endings

• Some respond to pressure, temperature, etc.

• Our brain interprets the amount of indentation/temp change = intensity of touch

• Different concentrations of nerve endings around the body

• Pain receptors fire to warn us of potential dangers

• Gate control theory: explains that some pain messages have a higher priority than others

  • Endorphins, or other pain-killing chemicals in the body, swing the gate shut to know there is no pain

  • Natural endorphins = morphine

Chemical sense:

Taste: (gustation)

• Taste receptors are located on papillae

• Taste buds are all over the tongue, inside of the cheeks, roof of the mouth

• Sweet, salty, sout, bitter, umami, oleogutus

• Supertasters have more densely packed taste receptors

• There are also nontaster and medium taster

• Food = taste + smell

Smell: (olfaction)

• Chemical in the air are picked up by our noses to smell

• There are 100 different types of smell receptors

• Olfactory bulb send informations to the brain about smell

• Impulses from all but smell go to the thalamus. For smell it goes to the amygdala, then to the hippocampus (smell triggers memories)

Body senses:

Vestibular sense: 

• Tells us how our body is oriented in space

• Semicircular canals in the inner years play an important part

  • Tubes filled with fluid

  • Wehn the fluid moves, sensors in the canals move

  • Hair cells activate neurons

  • Nausea and dizziness caused when the fluid in these canals is agitated

Kinesthetic sense:

• Kinesthesis gives feedback about the position and orientation of specific body parts

  • Receptors in the muscles and joints send information to brain

  • That and visual feedback keep track of body