Focused cards Flashcards
- How do genes yield traits (how does genotype become phenotype)? That is, what are the biological processes that lead to synthesis of cell proteins such as receptors and ion channels? If two people differ on a particular trait as adults (e.g., neuroticism, intelligence), what are genetic mechanisms that could explain inherited vs. environmental influences on this particular trait?
DNA –> transcription –> mRNA –> Translation –> proteins (receptors, ion channels, some nerve transmitters) –> TRAIT
EX: Dr craft is risk averse (similar to her biological parents), whereas Alfred is bold & fearless (I, E Dr craft is higher than Alfred on neuroticism)
The gene that encodes (leads to the synthesis of) GABA* contributes to neuroticism;
Perhaps Dr craft inherited a type of GABA gene (w/ a particular DNA sequence) that makes only a modest amount of GABA
*GABA= inhibitory neurotransmitter
Alfreds “GABA gene” is very proficient, but craft’s GABA gene is less so
Thus, Alfred’s neurons make a lot of GABA, whereas Crafts makes less.
This results in lower neural firing in Alfreds brain (especially amygdala) than in crafts.
Calmer amygdala=calmer person.
*Amygdala is the brain area highly active during fear.
- Describe two mechanisms at the DNA level that can result in increased or decreased gene expression (i.e., that can turn genes on or off) after conception.
Life events can modulate the extent to which genes are activated.
Mechanisms include:
- DNA methylation: methyl group binds to a segment of DNA less gene expression (less transcription) – or ^ if demethylation occurs
- Histone remodeling: the core around which DNA wraps changes shape >> modulates gene expression or modulates extent of transcription
- Can “selective breeding” be used to improve performance on a maze task in rats? Is the performance of “maze-dull” vs. “maze-bright” rats similarly altered: (a) if they are raised by parents who perform differently on this task? (b) if they are raised in an “enriched environment”?
Rearing rats in an enriched enviroment equalized maze performance between the two populations!
Environment altered the gene expression
- What is the genetic basis of PKU (phenylketonuria)? How can environmental (dietary) adjustment compensate for this gene abnormality?
Genetic basis at birth?
Gene coding for enzymes that converts phe to tyr is not functional, so little tyr
This the brain cannot synthesize dopamine (DA made from tyr)
Thus abnormal brain development (frontal lobe dopamine activity crucial for cognition)
Can altered diet (envir factor) compensate for gene disorder?
Yes low phenylalanine foods ca help overcome this
Phe > tyresine > low dopamine(5-ht)
Needs low phenyl foods and high tyresine
- symptoms include vomiting, seizures, hyperactivity, intellectual disability, irritability, and brain damage
- lack phenylalanine hydroxylase, an enzyme required to convert phenylalanine to tyrosine
- phenylalanine accumulates in the body; and levels of dopamine, a neurotransmitter normally synthesized from tyrosine, are low
- Leads to abnormal brain development
- Why were heritability estimates from early twin studies misleading (i.e., why did early twin studies overestimate trait heritability)? How can epigenetic studies of monozygotic twins be used to help us better understand how environment influences traits/disease as we age?
A relatively select (non-diverse) sample of identical twins raised apart vs. together
Comparison of monozygotic twins’ epigenetic differences as they age (periodic DNA sampling to screen for methylations, histone modifications)
Comparison of disease discordant monozygotic twins> epigenetic differences between them may lead to discovery of genes underlying disease.
- Describe the basic divisions of the nervous system (what they’re called, where they’re located, what they do).
The central nervous system (CNS) functions as the processing center for the nervous system. It receives information from and sends information to the peripheral nervous system.
The nervous system has three broad functions: sensory input, information processing, and motor output.
The peripheral nervous system (PNS) is the division of the nervous system containing all the nerves that lie outside of the central nervous system (CNS). The primary role of the PNS is to connect the CNS to the organs, limbs, and skin.Jun 4, 2020
The 4 main functions of the nervous system are: Reception of general sensory information (touch, pressure, temperature, pain, vibration) Receiving and perceiving special sensations (taste, smell, vision, sounds) Integration of sensory information from different parts of the body and processing them
- Describe the functions of the sympathetic and parasympathetic nervous systems, including some physiological effects of sympathetic NS activation (and what types of events activate it).
Sympathetic vs parasympathetic NS
Fight or flight ie energy expending vs rest and digest (energy conserving)
- How well protected is the CNS compared to the PNS (describe protective mechanisms)? Can your CNS and PNS neurons repair themselves if they are damaged? If so, how?
NS Protection/injury
CNS is well protected by the skull + meninges
Also the vertebrae.
Cerebrospinal fluid. (CSF)
Cusions brain and spinal cord
CSF produced in ventricles (chambers) of the brain.
PNS not as well protected
… but nerves typically deep within limbs, & PNS neurons regenerate to greater extent (axons regrow, as long as soma intact)
What events cause NS injury?
What determines extent of disability
After peripheral nerve injury? If it can regenerate
After spinal cord injury? Extent and location, lower the better
- What is the blood brain barrier (BBB), physically? What purpose does the BBB serve?
Immunological protection:
Blood brain barrier (BBB)
Prevents most large molecules (e.g bacteria) from entering brain.
- What do the terms dorsal/ventral, lateral/medial, anterior/posterior, and rostral/caudal refer to? [Try describing where different parts of the body/brain are located relative to one another, using these terms]
Thus, anterior and posterior indicate front and back; rostral and caudal, toward the head and tail; dorsal and ventral, top and bottom; and medial and lateral, the midline or to the side. Nevertheless, the comparison between these coordinates in the body versus the brain can be confusing.
- Label the major parts of a neuron and describe the function of each part. Describe the major types of proteins that are embedded in a neuron’s lipid bilayer membrane.
Cell membrane
The semipermeable membrane that encloses the neuron `
Cell body
The metabolic center of the neuron; also called the soma
Dendrites
The short processes emanating from the cell body, which receive most of the synaptic contacts from other neurons
Axon hillock
The cone-shaped region at the junction between the axon and the cell body
Axon
The long, narrow process that projects from the cell body
Myelin
The fatty insulation around many axons
Nodes of Ranvier
The gaps between sections of myelin
Buttons
The button-like endings of the axon branches, which release chemicals into synapses
Synapses
The gaps between adjacent neurons across which chemical signals are transmitted
Cell wall= lipid bilayer with proteins embedded in it.
Ion channels: regulate cation+/anion flow in or out of the cell
Receptors: nt bind to them to signal excitation (+, ^ firing) or inhibition (- firing).
Transporters: actively move important molecules in and out of cell (e.g NA+/K+ transporter, nt transporter)
- Name and describe the functions of 4 types of glial cells (3 in CNS, 1 in PNS).
Glial cells, (Glia)
CNS: all encased in bones
Oligodendrocytes: produce myelin sheath paddles (octopus cns
Microglia: respond to injury, disease (clean up, trigger inflammation); regulate synapse formation and elimination
Astrocytes: part of the BBB; regulates blood flow.
PNS:
Schwann cells: ARE myelin sheath; direct axonal regrowth after injury.
- Name and identify on whole-brain and mid-sagittal views (see below) the major parts of the hindbrain, midbrain and forebrain, and describe at least one function of each structure. What behavior/experience might be changed if each structure was damaged?
Hindbrain
- Medulla; autonomic, basic life support functions ( breathing, heartbeat, digestion, swallow cough vomit sneeze)
- Pons: soma of “reticular activating” neurons, responsible for wakefulness/alertness.
a. alertness, sleep/wake cycle: locus ceruleus (norepinephrine relasing)
Sleep/wake cycle: raphe (5-HT (serotonin)- releasing)
- Cerebellum: motor coordination/balance (execution of learned motor sequences, largely unconcius during execution); some cognitive functions.
Midbrain
- Tectum (“roof”, dorsal)
- Superior colliculus: visual coordination of movement ( particularly reflexive movement of the head)
- Inferior colliculus: sound localization; auditory coordination of movement (includes reflexive movement of the head)
- Tegmentum (“floor, ventral)
- Periaqueductal Gray (PAG): pain modulation, freezing behavior (opiods bind here)
- Ventral Tegmental area (VTA): pleasure/motivated behavior (Dopamine-releasing)
- Substantia Nigra: speed of movement ( Dopamine releasing)
Forebrain
- Thalamus: sensory motor “relay/coordination station” … Nuclei for vision, audition, somatosensation.
- Hypothalamus: 4Fs (sympathetic NS activation starts here)
- Basal Ganglia: habitual movement (cannot see this from a whole brain and mid sagittal view) lateral to the thalami. Damage: disease (Tourette’s, OCD also associated with function of basal ganglia
- Amygdala: emotion, particularly fear, anger
- Hippocampus: episodic, declarative learning/memory (Damage? HM (Anterograde memory formation couldn’t happen) Jimmie G, Alzheimer’s)
- Cerebrum (cerebral cortex/Cerebral hemispheres:
Occipital lobe: simple visual perception
Parietal lobe: somatosensory (touch) perception (anterior); Complex visual perception(posterior)
Temporal lobe: complex visual perception; auditory perception
Frontal lobe: decion making/reasoning (prefrontal cortex= PFC; anterior) planning and execution of conscious movement (motor cortex: posterior)
Somatotopic arrangement: Primary motor cortex (frontal lobe) ; primary somatosensory cortex (parietal lobe)
- Motor and sensory systems are said to be mostly “crossed over” – what does this mean?
Crossover of motor and sensory pathways
- primary motor cortex axons> crossover at medulla> control muscles on other side of body
Somatosensory neurons on one side of body> Axons crossover in spinal cord > ascend to thalamus, somatosensory cortex on other side of the brain
Visual and auditory neurons also mostly crossover to one side of the brain
- Explain how the membrane potential of a neuron is maintained at rest (in a “polarized” state, approx. -70 mV).
- Resting membrane potential
- “potential”=difference in electrical charge from inside to outside of axon (neuron)
- At rest, -70 mv, because fewer cations+ inside than outside. (How is this negative state maintained? Pump moves 3+ out for every 2+ in) Cation+ channels closed so cations cant flow back in
- What cations are involved?
Na+: more outside than inside axon, so concentration gradient OUT.
K+: more inside than outside axon, so concentration gradient IN
NA+ OUT, K+ IN
Resting potential: neuron is POLARIZED, “poised like a stretched rubber band”
