AP Bio Unit 11
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katiemcd95 on February 29, 2012
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74 terms
Terms | Definitions |
|---|---|
 dendrite | short fiber that conducts toward the cell body of the neuron |
| cell body | largest part of a typical neuron; contains the nucleus and much of the cytoplasm |
| axon | long nerve fiber that conducts away from the cell body of the neuron |
| terminal branches | branched end of axon that contains neurotransmitters, forms junction with other cells |
| synaptic knobs | distal tips of axon; stores and release neurotransmitters that passes info over to next neuron |
| neurotransmitter | transmits nerve impulses across a synapse (i.e. dopamine, acetylcholine) |
| myelin sheath | a layer of fatty tissue encasing a neuron's axon that speeds transmission |
| Schwann cell | any cell that covers the nerve fibers in the peripheral nervous system and forms the myelin sheath |
| nodes of Ranvier | small gaps in the myelin sheath of medullated axons |
| resting potential | the potential difference between the two sides of the membrane of a nerve cell when the cell is not conducting an impulse (Na+/K+ pumps must run continuously to restore & maintain this) |
| action potential | the local voltage change across the cell wall as a nerve impulse is transmitted ("wave of depolarization" that travels from dendrite to axon of the neuron) |
| voltage gated channel | A specialized ion channel in the membrane of a neuron that opens or closes in response to changes in membrane potential |
| synaptic vesicle | spherical sac containing neurotransmitters that are released in the synapse |
| homeostasis | metabolic equilibrium actively maintained by several complex biological mechanisms that operate via the autonomic nervous system to offset disrupting changes |
| feedback control | the ability of a neuron to to respond to stimuli and regulate the amount of neurotransmitters/reuptake/receptors (CHECK THIS) |
| set point | the point at which life processes are regulated, often through adjustments made by the integrator (control center-brain) |
| sensor | receives information- i.e. baroreceptors detecting a decrease in blood pressure when standing up |
| integrator | receives information from a sensor and makes decisions accordingly |
| effector | carries out the response- i.e. smooth muscles in constricting blood vessels to lower blood pressure |
| response | result from an integrator to help maintain homeostasis- carried out by an effector |
| sensory receptors | these detect changes in the environment and stimulate neurons to send nerve impulses to the brain (located at dendrites) |
| central nervous system | the portion of the vertebrate nervous system consisting of the brain and spinal cord (kind of like the "middle step" between sensing&responding) |
| peripheral nervous system | the section of the nervous system lying outside the brain and spinal cord |
| sensory neuron | a neuron conducting impulses inwards to the brain or spinal cord from sensory receptors |
| motor neuron | a neuron conducting impulses outwards from the brain or spinal cord (usually to muscles) |
| voluntary (somatic) nervous system | information sent out to skeletal muscles is part of this |
| involuntary (autonomic) nervous system | information sent out to smooth muscles of organs and cardiac muscle of the heart |
| sympathetic nervous system | opposes physiological effects of the parasympathetic: reduces digestive secretions; speeds the heart; contracts blood vessels "fight or flight" |
| parasympathetic nervous system | opposes physiological effects of the sympathetic nervous system: stimulates digestive secretions; slows the heart; constricts the pupils; dilates blood vessels "rest and repair" |
| saltatory conduction | Rapid transmission of a nerve impulse along an axon, resulting from the action potential jumping from one node of Ranvier to another, skipping the myelin-sheathed regions of membrane. |
| spinal cord | a major part of the central nervous system which conducts sensory and motor nerve impulses to and from the brain |
| spinal nerve | any of the 31 pairs of nerves emerging from each side of the spinal cord (each attached to the cord by two roots: ventral and dorsal) |
| interneuron | "association neuron"- , a neuron that carries nerve impulses from one neuron to another, located in the CNS |
| monosynaptic reflex | Reflex pathway with only one synapse between the sensory and motor neurons (ex: knee-jerk). |
| polysynaptic reflex | reflex that has at least one interneuron placed between the sensory afferent and the motor efferent, thus having a longer delay between stimulus and response |
| presynaptic membrane | the specialized membrane of the axon terminal of the neuron that transmits information by releasing neurotransmitters |
| presynaptic receptor | receptor that recovers neurotransmitters |
| postsynaptic membrane | effector cell or neuron that is the reciever of the neurotransmitter (part of the synapse- membrane) |
| postsynaptic receptor | a receptor molecule in the postsynaptic membrane of a synapse that contains a binding site for a neurotransmitter (gated channel or signal molecule) |
| transporters | pumps that recover neurotransmitters through active transport |
| calcium ion channels | pathway in the plasma membrane through which calcium ions enter and leave |
| excitatory neurotransmitter | neurotransmitter that triggers activity (depolarization) through opening Na+ gated channels |
| inhibitory neurotransmitter | neurotransmitter that opens channels that allow Cl- to diffuse into neurons which "hyperpolarizes" the synapse (more sodium needed to make neuron positive- disables "trigger") |
| acetylcholine | neurotransmitter that triggers muscle contraction (excitatory) |
| GABA | amino acid that serves as a major inhibitory neurotransmitter |
| spatial summation | the accumulation of neurotransmitters through the contribution of several neurons at a synapse (see, hear, smell, remember monster) |
| temporal summation | multiple neurotransmitters through the same neuron (rapid fire from same sensory input source), causes response differently but usually as effectively as spatial |
| synaptic integration | The summation of the inhibitory and excitatory signal received by a post-synaptic neuron which occurs because a neuron receives many signals, provides a basis for "decision-making" |
| dopamine | neurotransmitter that stimulates the "pleasure center" of the brain- cocaine blocks transporters that recover this back at the presynaptic membrane & destroys postsynaptic receptors |
| serotonin | neurotransmitter that affects mood, hunger, sleep, and arousal |
| neuromuscular junction | the junction between a nerve fiber and the muscle it supplies |
| sarcolemma | the plasma membrane of muscle fibers |
| T tubule | t-shaped extension of the muscle cell plasma membrane that protrudes deeply into the muscle cell |
| sarcomere | one of the segments into which a myofibril is divided (each one shortens during muscle contraction- separated by z-lines) |
| sarcoplasmic reticulum | the smooth ER of a muscle fiber, stores and releases calcium into sarcoplasm after nervous stimulation |
| myofibrils | bundles of proteins that include actin and myosin- one unit is a sarcomere |
| z-line | A dark thin protein band to which actin filaments are attached in a striated muscle fiber, marking the boundaries between adjacent sarcomeres |
| actin | protein that mainly makes up the thin filaments in striations in skeletal muscle cells |
| myosin | protein that makes up the thick filaments in striations in skeletal muscle cells |
| H zone | The region at the center of an A band of a sarcomere that is made up of myosin only. The H zone gets shorter (and may disappear) during muscle contraction |
| striations | skeletal and cardiac muscles have these (contain sarcomeres) |
| myosin head | A projection from a myosin filament that forms cross bridges with binding sites on actin filaments |
| tropomyosin | covers myosin binding sites on the actin molecules, removed when calcium bonds with troponin to expose this site for muscle contraction |
| troponin | a regulatory protein that is a component of the thin filament. When calcium ions (Ca2+) bind to troponin, it undergoes a change in shape; this conformational change moves tropomyosin away from myosin-binding sites on actin molecules, and muscle contraction subsequently begins as myosin binds to actin |
| cross-bridge binding site | consists of an attachment between a myosin head and a binding site on actin |
| cross-bridge binding cycle | process of ATP changing the direction of myosin heads- energy from ATP moves the myosin head to the cross-bridge binding site on actin, bond is broken when another ATP comes and the cycle is repeated again |
| motor unit | motor neuron and all the muscle fibers it innervates |
| recruitment | the process of recruiting more motor units for stronger muscle contraction |
| summation | the addition of individual twitch contractions produced by stimulating the muscle rapidly enough so that one contraction is not finished before another begins; repeated action potentials are necessary to fully contract a muscle fiber |
| skeletal muscle | a muscle that is connected at either or both ends to a bone and so move parts of the skeleton; striated, cells continuous (fibers) |
| cardiac muscle | muscle of the heart; striated, fibers interconnected, cells marked by separations **nerve impulse can start at one spot and connect to all muscle cells for efficiency |
| smooth muscle | a muscle that contracts without conscious control and found in walls of internal organs such as stomach and intestine and bladder and blood vessels (excluding the heart); not striated, separate cells |
| muscle fatigue | inability of of a muscle to contract when stimulated caused by lack of oxygen, energy, and increased lactic acid (interferes with enzymes that control the cross-bridge binding cycle) |
| oxygen debt | lack of oxygen so oxidative phosphorylaton cannot take place (final electron acceptor); required to break down accumulated lactic acid (turn back into pyruvate & recover) |
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