PSY 340 - EXAM 2

Biological Psychology ch 4, ch 7, ch 8

DNA

• double-stranded helix w 4 bases: Adenine, guanine, cytosine, and thymine

  • Model for RNA

RNA

• Bases include: adenine, guanine, cytosine, and uracil 

• Order of RNA = proteins 

Epigenetics

changes in gene expression without changes in DNA, experiences alter gene activity due to how tightly DNA is wrapped around (cherry study example)

Monozygotic twins

1 egg, 1 sperm

semi-identical

1 egg, 2 sperm

dizygotic twins 

2 eggs, 2 sperms

Ways of estimating heritability

• compare monozygotic and dizygotic twins

• compare adopted children with their biological and adoptive parents

• identify genes associated with behavior

Human chimeras

people w double DNA

Artificial selection

the process where humans selectively breed plants and animals for desired traits

lamarckian evolutionary ideas

organisms evolve by acquiring characteristics during their lifetime through the use or disuse of body parts and then passing those traits to their offspring

social behavior and evolutionary theory

Evolutionary theory explains social behavior by asserting that behaviors such as cooperation, altruism, and even fear are inherited predispositions that helped our ancestors survive and reproduce

Brain growth

Homeobox genes guide body/brain formation

CNS begins forming neural tube at 2 weeks

Hindbrain, midbrain, forebrain are distinct at 7 weeks

Failure of neural tube closure —> Spina bifida

Steps of Neuronal Development

1. Proliferation - new cells form

2. Migration - guided by immunoglobulins & chemokines

3. Differentiation - axon & dendrites form

4. Myelination - glia add myelin

5. Synaptogenesis - new synapses form

olfactory receptors

G-protein-coupled receptors (GPCRs) that detect volatile chemical molecules, enabling the sense of smell by initiating an electrical signal that is sent to the brain for perception and emotional response

Pathfinding by axon

axons seek specific connections and follow chemical gradients

experiment done by Sperry —> cut optic nerve —> rotate eye 180 —> nerve regrown —> frog sees things upside down and reversed

neuronal survival requires

• them forming a synapse w target

• release neurotransmitters into synapse w target 

• receives a neurotrophin (NGF and BDNF)

necrosis

the death of most or all of the cells in an organ or tissue due to disease, injury, or failure of the blood supply.

Gastrulation

fundamental process of early animal embryonic development where the simple, single-layered blastula reorganizes into a multi-layered embryo, the gastrula

teratogens

environmental factors that damage the fetus (EX: fetal alcohol syndrome) 

cortical differentiation

the process by which progenitor cells mature into specialized neurons of the cerebral cortex

enriched environment results in

• more dendritic branching

• thicker cortex

• more finely tuned neurons

• more axon/dendrite sprouting

Ischemic stroke 

blood clot

hemorrhage stroke

ruptured artery

Loss of normal blood flow to brain area results in

• cell death (immediate or penumbra)

• edema (swelling)

• impaired Na/K pump

• release of glutamate from glia which overstimulates the cell

Reducing harm from a stroke

• immediate treatment (ischemic = tPA; reduce overstimulation = cooling) 

• increasing stimulation (stimulants/physical therapy) limits diaschisis (reduced activity of surviving neurons) 

• Regrowth of PNS axon

• Collateral sprouting (nearby neurons grow branches to replace synapses left vacant by a damaged axon) 

• Denervation supersensitivity (remaining receptors become more sensitive) 

smooth muscle

internal organs

skeletal (striated) muscles

movement

cardiac muscles

heart

neuromuscular junction

synapse of motor neuron with muscle fiber

ACh is releases —> muscle contracts

wout ACh —> muscle relaxes

Movement in two directions

antagonistic muscles required (flexor/extensor)

Fast twitch muscle fibers

fast contractions, easily fatigued, anaerobic, few mitochondria, good for sprinting

slow twitch muscle fibers

slow contractions, resistant to fatigue, aerobic, many capillaries, good for endurance

Proprioceptors 

receptors sensitive to body position & movement

stretch reflex

a simple involuntary muscle contraction that occurs when a muscle is stretched.

muscle spindle

detects stretch

sends feedback to motor neuron to contract —> basis for stretch reflex

golgi tendon organ 

detects increase in muscle tension

sends inhibitory signals —> prevents excessive contraction

protects muscle from damage

Reflexes 

involuntary movement (knee jerk —> tap stretches muscle spindle and feedback jerks leg up) 

Infant reflexes 

rooting, grasp, babinski

Ballistic movement

very rapid, once started cannot be altered (quick punch)

Feedback-sensitive movement

adjusted during execution (threading a needle)

Movement Pattern Generation (Central Pattern Generators)

Located in spinal cord

produces rhythmic outputs (walking, breathing)

Movement Pattern Generation (Motor Programs)

Fixed sequences of movement

automatic, can be disrupted if you consciously think abt them

Generation of Movement

stimulate motor cortex —> elicits complex movements, not isolated muscle twitches

outcome-based activation: motor cortex codes for goal/outcome, not each muscle individually

Anosognosia

neurological condition where a person is unaware of their own physical or mental deficits

Posterior parietal Cortex

converts visual info —> motor commands

Integrates vision & proprioception

damage —> difficulty visually guiding movement

Supplementary motor cortex

organizes rapid sequences of movement

important for learned, habitual sequences

Premotor cortex

prepares movement

receives info about target location and body position

Prefrontal cortex

planning, evaluating consequences

damage —> poorly planned, impulsive, inappropriate movement

Saccades

rapid eye movement

antisaccade task

requires looking away from a stimulus

needs inhibitory control, depended on prefrontal cortex and basal ganaglia

mirror neurons

activate while performing an action, watching someone perform the same action, hearing action-related sounds, OR being reminded of an action

functions: imitation learning, understanding intentions, modify based on learning/practice

Amyotrophic Lateral Sclerosis

motor neuron degeneration

progressive weakness

Lateral Corticospinal tract

Origin: Primary motor cortex & red nucleus

Crosses at pyramids of medulla (decussation)

Controls fine movement of hands, fingers, and toes

Damage —> loss of find motor control

Medial Corticospinal tract

Origins: motor cortex, tectum, reticular formation, and vestibular nucleus

Bilateral connections

Controls posture & trunk movement

Damage —> impaired waking, bedding, and standing

Cerebellum

Functions: timing, balance, attention shift, and habit formation

Structure: Purkinje cells (flat, receive input from parallel fibers)

Damage —> symptoms similar to drunkenness

Basal Ganglia

Structure: caudate nucleus, putamen, globus pallidus

Functions: initiate/inhibit movement, combine steps into smooth automatic sequences, habit learning

Parkinson’s Disease

Characteristics: progressive death of neurons in substantia nigra —> decreased dopamine —> impaired movement initiation

Symptoms: rigidity, tremors, slow movement, cognitive slowly, depression

Biomarkers: DOPA decarboxylase

Causes: genetics (alpha-synuclein abnormalities), exposure to toxin, damaged mitochondria

Treatment: L-DOPA, Deep Brain Stimulation, Neurotrophies, Cell transplants, smoking & caffein

Huntington’s Disease

Characteristics: sever neurodegenerative disorder, onset age 30-50

Brain areas affected: caudate nucleus, putamen, globus pallidus, cortex

Cause: dominate gene on Chromosome 4, expansions of CAG repeats

Homeostatic Theory

sleep restores depleted resources

sleep rebound: after deprivation you sleep longer and deeper

Adaptive Theory

sleep conserves energy

body temp drops & activity decreases

evolutionary theory: being still during vulnerable hours protects you

Memory Enhancement

Hippocampus replays learning patterns during sleep.

Sleep improves consolidation of memories.

Endogenous Cycle of Sleep

Generated internally, independent of environment

Types of Endogenous Cycles of Sleep

Circannual

Circadian

Circannual

yearly rhythms (migration, hibernation).

Circadian

daily rhythms (sleep, temperature, hormones)

Zeitgeber

External cue that resets the biological clock.

Primary zeitgeber = LIGHT

Jet lag

Westward travel → phase delay (easier).

Eastward travel → phase advance (harder).

Jet lag = stressful therefore —> increases cortisol

Shift Work

Many shift workers never fully adjust.

More light helps adjust circadian rhythm

Melatonin

Released by pineal gland 2–3 hours before sleep.

Increases drowsiness.

Acts as an internal zeitgeber, feeding back to the Suprachiasmatic Nucleus

Suprachiasmatic Nucleus

Sets circadian rhythm.

Continues rhythmic firing even in tissue culture → internal clock

blind individuals (with intact melanopsin ganglion cells) can regulate sleep cycles

Retinohypothalamic pathway

Light → Retina → SCN

Specialized retinal ganglion cells send light signals to SCN

These cells do NOT contribute to vision

Contain melanopsin; respond to overall brightness.

Genes of Circadian Rhythm

Period (PER) and Timeless (TIM)

PER/TIM levels rise during evening → induce sleepiness.

When high, they inhibit their own production (negative feedback loop).

Mutated PER gene → altered sleep rhythm.

Coma

low arousal, low awareness

Vegetative State

arousal present, no awareness

Minimally Conscious

limited, inconsistent awareness.

Locked-in Syndrome

awareness intact, almost no movement

Brain Dead

no measurable brain activity

Sleep cycle

~90 minutes

1. Stage 1 (light sleep)

2. Stage 2 (sleep spindles & K-complexes)

3. Slow-wave sleep (SWS)

4. Stage 2

5. REM sleep

Polysomnography

a painless overnight test that monitors your body's activity during sleep to help diagnose sleep disorders measured w EEG and eye movement

REM Sleep Characteristics

Rapid eye movements.

High brain activity.

Postural muscles relaxed (sleep paralysis).

Dreams more vivid during REM.

REM Sleep Neurotransmitters

ACh increases → triggers REM

Serotonin & norepinephrine interrupt REM

REM Sleep Functions

Memory storage.

Oxygenation of corneas (prevents drying)

Reticular Formation

Lesions → decreased arousal

Pontomesencephalon

Part of reticular formation

Releases ACh & glutamate → increases cortical arousal

Some cells release GABA (regulating transitions)

Locus Coeruleus

In pons and releases norepinephrine

Responds to meaningful events (alerting system)

Mostly silent during sleep

Hypothalamus

SCN controls circadian rhythms.

Releases histamine → arousal.

Releases orexin/hypocretin → maintains wakefulness

Basal Forebrain

Projects to thalamus & cortex.

Releases GABA → sleep-onset inhibition.

Releases ACh → cortical activation.

Adenosine

Byproduct of metabolism.

Accumulates during day → produces sleepiness.

Declines during sleep.

Caffeine blocks adenosine receptors.

Brain Function During REM Sleep

Areas showing increased activity: Pons, Limbic system, Parietal & temporal cortices

Areas showing decreased activity: Primary visual cortex, Motor cortex, Dorsolateral prefrontal cortex

PGO waves

electrical signals in the brain strongly associated with REM sleep and are thought to be a major component of dreams

Pons —> Lateral Geniculate Nucleus —> Occipital cortex

Activation Synthesis Hypothesis

Dreams begin in pons.

Brain creates a story to make sense of random signals.

Neurocognitive Hypothesis

Dreams = thinking under unusual conditions.

Minimal sensory input.

High activity in: Emotion, Memory, & Inferior parietal lobule areas

Default Mode Network involved.

Onset Insomnia

Phase delayed → difficulty falling asleep.

Termination insomnia

Phase advanced → waking too early.

Caffeine

Stimulant → mimics sympathetic activation.

Major cause of insomnia.

Keep < 400 mg/day, less during pregnancy.

Sleep Apnea

Inability to breathe while asleep.

Associated with obesity.

Treated with CPAP.

Narcolepsy

Sudden attacks of sleepiness.

Caused by loss of orexin-producing hypothalamic cells.

Treatment: stimulants like Ritalin.

Periodic Limb Movement Disorder

Involuntary limb movements.

Treated with tranquilizers.

REM Behavior Disorder

Acting out dreams (failure of REM paralysis).

Caused by too little GABA → pons fails to inhibit motor neurons.

Lucid Dreaming

Aware you are dreaming.

Brain remains in REM pattern.