• What attributes of genes (e.g., heterozygous vs. homozygous; dominant vs. recessive) determines what type of protein, and thus trait, will be expressed?o Homozygous: genes on each chromosome are identicalo Heterozygous: genes on each chromosome are differento Dominant: expressed trait will show through in either homozygous or heterozygous condition (Rr, RR)o Recessive: expressed trait will only show through in homozygous condition (rr)• What types of natural and experimental procedures can be used to differentiate between genetic and environmental influences on behavior?o Studies using genetically modified animals (i.e., knockout mice)o Twin studies Monozygotic: identical genetic code Dizygotic: fraternal, as genetically similar as typical siblingso Adoption studieso Gene association studies• What are neurons specialized to do?o Neurons are cells specialized to receive and transmit informationo They are individual entities, but work as a group (with the help of glial cells) to make up the nervous system• Name the parts of neurons that enable this specialization.o Have cell body (soma) just like any other cell.o Branching extensions specialized to receive and transmit signals. Dendrites: receive information• May be equipped with spines to increase surface area Axon: sends information• May be coated in a myelin sheath so information can be conducted faster• Spaces between myelin called nodes of Ranvier Presynaptic terminals: end of axon where electrical action turns chemical.• What forces act on what types of ions to affect their distribution inside and outside the cell? -- for example, why does Na+ "want" to go into the cell but why "can't" it?o The composition of the cell membrane makes it semi-permeable: Non-charged particles (ex., O2) can diffuse through Charged particles (ex., ions) need help from a channel Big charged particles (ex., proteins) can’t pass at allo Concentration gradient Particles in solution don’t stay clustered together with chemicals of the same type – they diffuse and distribute equally in the solution.• Example: food coloring moves through a plant’s stem up to the flowers Ions on the outside of the cell membrane ‘want’ to mix with ions on the inside of the cell, but the semi-permeable nature of the membrane prevents that.o Electrical gradient Particles with opposite charges attract one another, and particles with like charges repel each other• Example: magnets Positive ions on the outside of the cell membrane are drawn to the negative ions on the inside of the cell, but their movement is blocked by the semi-permeable nature of the membrane.o Ions are subject to both electrical and concentration gradients Example: sodium (Na+) and potassium (K+) ions want to mix because of their different chemical nature, but repel one another due to their similar electrical natures• What protein complex on the cell membrane actively restores and maintains this distribution, and how?o Changing the membrane potential If the charge differs on either side of the membrane, the membrane is said to be polarized. If it becomes more polarized (i.e., the charge of the inside of the cell gets even more different from the outside), the cell is said to be hyperpolarized. If it becomes less polarized (i.e., the charge of the inside of the cell gets closer to that of the outside), the cell is said to be depolarized. The neuron responds to anything that changes the permeability of the membrane (i.e., opens channels) and/or changes the concentration of ions or charge across the membrane• Electrical current: artificial stimulation with an electrode• Environmental energy: light, pressure – sensory systems• Chemical energy: neurotransmitters, drugs• What must happen for a neuron to reach its threshold of excitation, and what happens when it does?o Depolarization past a neuron’s threshold opens voltage-gated Na+ and K+ channelso A neuron can take only so much depolarization Its “limit” is called its threshold of excitationo The threshold is based on what voltage it takes to open voltage-gated ion channels.• Describe how two neurons communicate across a chemical synapse -- how does this differ from electrical synapses?o Though each neuron is an independent unit, they do not exist in isolation. Groups of neurons are linked together in a circuit-like fashion to get info from one area of the body to another.o An electrical signal cannot jump from one separate neuron to another.o The ‘message’ must be reconfigured into a form that can move across the space between neurons This space between individual neurons is referred to as a synaptic cleft.o Chemicals released by the presynaptic cell can diffuse across the gap to the postsynaptic cell. This functional area between two neurons is referred to as a synapse (hence pre- and postsynaptic).o Neurotransmitters Chemicals that are released into the synapse at the axon of a presynaptic cell after a single action potential and, based on activity at a receptor, have an effect on the membrane potential of the postsynaptic cell.o Order of events at chemical synapses Synthesis and storage Release Activation of receptors Elimination• What ion is directly responsible for the movement of neurotransmitters into the synaptic cleft?o Depolarization from action potential opens voltage-gated calcium (Ca++) channels in presynaptic terminal.o Calcium influx results in exocytosis of vesicles – neurotransmitter bursts out of end of presynaptic terminal.o Neurotransmitter diffuses across synapse.• Define and give examples of temporal and spatial summation.o Temporal summation: recurrent small stimulation to the same place.o Spatial summation: small stimulation to multiple areas.• What effect do EPSPs and IPSPs have on the membrane potential of a neuron?o Excitatory postsynaptic potential (EPSP) Graded depolarization Results from an influx of sodium ions Increases probability of an action potentialo Inhibitory postsynaptic potential (IPSP) Graded hyperpolarization Results from influx of chloride ions or efflux of potassium Decreases probability of an action potential• Describe in what ways drugs can act at receptors in order to mimic or block natural neurotransmitter action (e.g., serve as agonists or antagonists – be prepared for examples).o Agonist: increases, enhances, facilitates, or mimics natural
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