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What does a gene do?
code for specific proteins
How many kinds of protein molecules is the human body constructed of?
70,000
What are the 4 nucleotides?
adenine, thymine, cytosine, guanine
What does DNA stand for?
deoxyribonucleic acid
What are bases of DNA?
long sequences of the nucleotides that provide the blueprint for genetic inheritance
What are genes?
vertical sequences of DNA
What are alleles?
alternate forms of genes
What happens when proteins combine with other bodily products and the environment?
increases the probability of a given behavior or attribute
What are epigenetics?
field which explores how gene expression is influenced by environmental events (experiences, nutrition, stress) and even passed on to successive generations
What are genes arranged on?
chromosomes
How many chromosomes do humans have?
46 chromosomes, arranged in 23 pairs
What are the first 22 pairs of chromosomes called?
autosomes (homologous chromosomes)
What are homologous chromosomes?
the two members of each pair are similar in size, shape, and genetic function
What is the 23rd pair of chromosomes called?
sex chromosome (X or Y)
What are the female sex chromosomes?
XX
What are the male sex chromosomes?
XY
How many chromosomes do sperm and ova have?
½ the normal pair
What is genotype?
total genetic endowment inherited by an individual
What is phenotype?
observable and measurable characteristics and traits of an individual
What is phenotype a product of?
the interaction of the genotype and the environment
What is range of reaction?
genes provide our possibilities (the limits); the environment sets our actualities
What are homozygous alleles?
alleles that are alike
What are heterozygous alleles?
alleles that are not alike
What is a dominant allele?
allele whose characteristics are reflected in the phenotype even when part of a heterozygous genotype
What are examples of dominant alleles?
tongue rolling, Huntington’s disease
What is a recessive allele?
allele whose characteristics do not tend to be expressed when part of a heterozygous genotype
What are examples of recessive alleles?
sickle-cell anemia, PKU (phenylketonuria)
What is sickle-cell anemia?
recessive allele; changes the shape of red blood cells
What is PKU (phenylketonuria)?
recessive allele; unable to break down phenylalanine (amino acid found in milk and foods high in protein)
What are codominant alleles?
condition in which individual, unblended characteristics of two alleles are reflected in the phenotype
What are examples of codominant alleles?
AB blood type
What alleles are in blood type?
A, B, O
What blood type alleles are dominant?
A, B
What blood type alleles are recessive?
O
What are polygenic characteristics?
phenotype characteristic influenced by two or more genes
What are examples of polygenic characteristics?
skin color, height, reactiveness
What is important about sex-linked disorders?
the Y chromosome does not have a corresponding allele, so if the male inherits a recessive allele on the mother’s X chromosome, the effects will be apparent
What are examples of sex-linked disorders?
hemophilia, red-green color blindness, baldness
What is the nervous system?
a highly complex communication system of cells that function to coordinate and direct an organism in its interactions with its environment
What are neurons?
specialized cells which receive information and transmit it to other cells by conducting electrochemical impulses
What is the basic unit of the nervous system?
neurons
Approximately how many neurons does the adult human brain have?
100 - 200 billion (closer to 80 billion)
What is a nerve?
a bundle of axons (either sensory or motor) existing outside the CNS
What are the types of neurons?
sensory, motor, interneuron
What is a sensory neuron?
carry information from sensory organs to the central nervous system
What is a motor neuron?
receives excitation from other neurons and conducts impulses from soma in spinal cord to muscle or gland cells
What is an interneuron?
can receive information from sensory neurons and can send it to motor neurons or other interneurons
Where are interneurons located?
between sensory and motor neurons
What are most of the neurons in the human nervous system?
interneurons
What is the cell body or soma?
structure of the cell that contains the nucleus; much of cellular metabolism occurs in the soma
What is the dendrite?
thin, widely branching fiber that emanates from a neuron; receives information
What is the axon?
single fiber extending from a neuron; sends information
What is the axon hillock?
a swelling of the soma, at the point which the axon begins; beginning of the action potential
What is the myelin sheath?
a fatty material that insulates neurons; speeds up action potential
How much faster is a myelinated neuron versus an unmyelinated neuron?
10 times faster
What are the nodes of Ranvier?
short, unmyelinated sections of axon between myelin; area of myelinated axon at which the action potential occurs
What are the terminal buttons?
the swellings at the tip of an axon; the point from which neurotransmitters are released
What are terminal buttons also known as?
axon terminal; end buttons
What is electrical communication?
communication WITHIN the neuron; how information travels between dendrites to the terminal buttons
What is resting potential?
the resting state of the neuron
What happens during resting potential?
the inside of the neuron is more negative than the outside of the neuron due to the difference in concentration of ions
What ions are part of resting potential?
sodium (Na+) and potassium (K+)
Where does the threshold of excitation occur?
at the axon hillock
What is the threshold of excitation?
the excitatory and inhibitory changes in the membrane of the dendrites and soma are “added” together, and if the electrical charge at the axon hillock is high enough to reach the minimum level needed to start an action potential, the ion channels will open
What is action potential?
the movement of ions down the axon of a neuron; the depolarization of the axon
What is the “all-or-nothing” principal?
action potentials either occur or do not occur; it does not become stronger or weaker with time/repetition
What is chemical communication?
communication BETWEEN neurons (or other cells)
What is the synapse?
point of communication between two neurons or between a neuron and a muscle
Where is the synapse?
the space between neurons
What is an excitatory synapse?
neurotransmitter makes it more likely for positive ions (Na+) to move into the neuron
What is an inhibitory synapse?
neurotransmitter makes it more likely for negative ions (Cl-) to move into the neuron or for positive ions (K+) to move out of the neuron
What is a neurotransmitter?
chemical released at a synapse
What are receptor sites?
areas of a neuron that have protein embedded into the membrane
What happens at receptor sites?
when a neurotransmitter attaches to the active site of a receptor, it can directly open a channel or it can have slower, more long term effects
What does “lock and key” mean?
the neurotransmitter (key) has a specific shape that fits exactly into the receptor site (lock); only if there is a perfect fit between the neurotransmitter and the receptor site will the membrane of the receiving cell be altered
What are the steps at the synapse?
the neuron synthesizes neurotransmitters
the neuron transports these neurotransmitters to the axon terminals
an action potential causes the release of the neurotransmitters from the terminal buttons
the released molecules attach to receptors on the receiving cell and alter its activity
the molecules separate from their receptors and (in some cases) are converted into inactive chemicals
in some cells, as many as possible of the neurotransmitters are reabsorbed and recycled
What are the steps to neural communication?
a neuron receives stimulation at the receptor sites on its dendrites or cell body
this makes Na+ channels either more likely (excitatory) or less likely (inhibitory) to open
if there is enough positive charge to reach threshold at the axon hillock, an action potential is started
the action potential flows down the entire axon
at the axon terminal buttons, the action potential causes vesicles of neurotransmitters to bind to the cell membrane
the vesicles open, releasing neurotransmitters into the synapse
the neurotransmitters cross the synapse and bind onto receptor sites on the receiving cell
if the neurotransmitters are excitatory, Na+ channels open, increasing the positive charge; if they are inhibitory, it is less likely the channels will open
the receiving neuron adds up the charges at its own axon hillock; if it reaches threshold, an action potential occurs
the process repeats
What are the major neurotransmitters?
dopamine, serotonin, norepinephrine/adrenaline, acetylcholine, gaba, glutamate, endorphins
What is dopamine?
pleasure transmitter; stimulant
What is serotonin?
mood transmitter; hallucinogen
What is norepinephrine/adrenaline?
fight-or-flight neurotransmitter; stimulant
What is acetylcholine?
learning neurotransmitter; stimulant
What is GABA?
calming neurotransmitter; depressant
What is glutamate?
memory neurotransmitter; mild hallucinogen and depressant
What are endorphins?
euphoria neurotransmitter; depressant
What are the two main divisions of the nervous system?
central nervous system (CNS) and peripheral nervous system (PNS)
What makes up the CNS?
the brain and spinal cord
What makes up the PNS?
nerves outside the brain and spinal cord
What are the two main divisions of the PNS?
skeletal (somatic) NS and autonomic NS
What is the skeletal (somatic) NS?
nerves that carry sensory information to the CNS and motor information from the CNS muscles
What is the VOLUNTARY nervous system?
skeletal (somatic) NS
What is the autonomic NS?
nerves that regulate the internal organs
What is the INVOLUNTARY nervous system?
autonomic NS
What are the two main division of the autonomic NS?
sympathetic NS and parasympathetic NS
What is the sympathetic NS?
nerves that activate the internal organs for vigorous activity
What is “fight-or-flight” associated with?
the sympathetic NS
What happens during “fight-or-flight?”
increased heartbeat, blood pressure, respiration rate, sweating, diverts blood from internal processes such as digestion to the extremities; leading to an increased ability to fend off or run away from danger
What is the parasympathetic NS?
nerves innervating the internal organs; tend to conserve energy
What is “day-to-day housekeeping” associated with?
the parasympathetic NS
What happens during “day-to-day housekeeping?”
decreased heartbeat, blood pressure, respiration rate, sweating, directs blood to internal processes such as digestion
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