Psych - Chapter 3: Biological Foundations of Behavior

• Action Potential


  A localized area of depolarization of the plasma membrane that travels in a wave-like manner along an axon; the electrochemical signals of the nervous system
• Resting Membrane Potential


  An electrical potential established across the plasma membrane of all cells by the Na+/K+ ATPase and the K+ leak channels. IN most cells, the resting membrane potential is approximately -70 mV with respect to the outside of the cell. Interior negative with respect to the exterior of the cell.
• Na+/K+ ATPase


  3 Na+ out per 2 K+ in. Hydrolysis of 1 ATP; Primary Transport (uses ATP)
• Depolarization


  A change in the membrane potential from the resting membrane potential (-70 mV) to a less negative, or even positive, potential
• Repolarization


  Re-establishing the original resting membrane potential
• Factors that combine to produce repolarization

  1.) Voltage-Gated Na+ Channels inactivate very quickly after they open and remain inactivated until the membrane potential nears resting values again

  2.) Voltage-Gated K+ Channels open more slowly than Na+ channels and stay open longer; they open in response to membrane depolarization. They close once the membrane potential overshoots (-90mV)

  3.) K+ leak channels and the Na+/K+ ATPase continue to function to bring the membrane potential back to resting potential
• Schwann Cells


  Type of glia in the PNS, Supporting cells of the peripheral nervous system responsible for the formation of myelin. No ions can enter or exit a neuron where the axonal membrane is covered in myelin.

  Increase speed of conduction of APs along axon
• Nodes of Ranvier


  Gaps in the myelin sheath to which voltage-gated sodium and potassium channels are confined/concentrated
• 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
• Glial Cells


  Specialized, non-neuronal cells that typically provide structural and metabolic support to neurons.

  Schwann Cells; Oligodendrocytes; Astrocytes; Microglia;

  Ependymal Cells
• Oligodendrocytes


  Type of glial cell in the CNS that wrap axons in a myelin sheath; increases speed of conduction of AP's along axon
• Astrocytes


  CNS, guide neuronal development, regulate synaptic communication via regulation of neurotransmitter levels
• Microglia


  CNS; remove dead cells and debris
• Ependymal Cells


  CNS; produce and circulate cerebrospinal fluid
• Equilibrium Potential


  the membrane potential at which chemical and electrical forces are balanced for a single ion; driving force does not exist. Non net movement across the membrane
• Absolute Refractory Period


  A neuron will not fire another action potential no matter how strong a membrane depolarization if induced. Voltage-Gated Na+ channels have been inactivated and will not be bale to open again until the membrane potential reached the resting potential and these channels have returned to their closed state
• Relative Refractory Period


  the period of time following an action potential, when it is possible, but difficult, for the neuron to fire a second action potential, due to the fact that the membrane is further from threshold potential (hyperpolarized). A greater stimulus if required to open the Voltage-Gated Na+ channels to start an action potential
• Synapse


  the junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron
• Electrical Synapse


  A type of syanpse in which the cells are connected by gap junctions, allowing ions (and therefore an action potential) to spread easily from cell to cell, usually in smooth and cardiac muscle. - compared to chemical synapse.
• Chemical Synapse


  found at the ends of axons where they meet their target cells; APs are converted into chemical signals
• Steps involved in transmission of a signal across a chemical synapse

  1.) AP reached the end of an axon, the synaptic knob

  2.) Depolarization of the presynaptic membrane, VG Ca2+ channels open

  3.) Ca2+ influx into presynaptic cell causes exocytosis of NTMs stored in secretory vesicles

  4.) NTM molecules diffuse across synaptic cleft

  5.) NTMs bind to receptor proteins in the postsynaptic membrane. Receptors are ligand-gated ion channels

  6.) Opening of LG ion channels alter the membrane polarization

  7.) If depolarization of postsynaptic cell reaches threshold of VG Na+ channels, an AP is initiated

  8.) NTMs in the synaptic cleft are degraded/removed to terminate the signal
• Acetylcholinesterase (AChE)


  the enzyme that breaks down acetylcholine in the synaptic cleft. Commonly seen in neuromuscular junctions b/w neuron and skeletal muscle
• Excitatory Neurotransmitter


  A neurotransmitter that depolarizes the postsynaptic membrane. (the receptor is what ultimately determines)
• Inhibitory Neurotransmitter


  A neurotransmitter that hyper-polarizes the postsynaptic membrane. (the receptor is what ultimately determines)
• Temporal Summation


  In which a presynaptic neuron fires APs so rapidly that they EPSPs and IPSPs pile on top of each other. The additive effect might be enough to reach the threshold required to start an AP
• Spatial Summation


  Integration by a postsynaptic neuron of inputs (EPSPs and IPSPs) from multiple sources.
• Motor Neurons


  neurons that carry outgoing information from the brain and spinal cord to organs which can act upon that information, known as effectors (muscles and glands)
• Efferent Neurons


  Motor neurons which carry info away from the central nervous system and innervate effectors
• Afferent Neurons


  Sensory neurons which carry info towards the CNS
• Sensory Neurons


  neurons that receive information from the external world and convey this information to the brain via the spinal cord
• Reflex


  a simple, automatic response to a sensory stimulus
• Muscle Stretch Reflex


  a sensory neuron detects stretching of a muscle which synapses onto another neuron in the spinal cord, whose axon go back to the initially stretched muscle and cause it to contract
• Inhibitory Interneuron


  short neuron which forms an inhibitory synapse with a motor neuron
• Reciprocal Inhibition


  The simultaneous contraction of one muscle and the relaxation of its antagonist to allow movement to take place
• Somatic Division


  The part of the peripheral nervous system that specializes in the control of voluntary movements and the communication of information to and from the sense organs.
• Autonomic Division


  The part of the peripheral nervous system that controls involuntary movement of the heart, glands, lungs, and other organs. Concerned with digestion, metabolism, circulation, perspiration, and other involuntary processes.
• Rhomboencephalon


  the embryonic portion of the brain that becomes the hindbrain. Includes the medulla, pons and cerebellum
• Mesencephalon


  the midbrain; a region of the brain that surrounds the cerebral aqueduct; includes the tectum and the tegmentum and RAS (involved in arousal and wakefulness)
• Prosencephalon


  The embryonic portion of the brain that becomes the forebrain. Includes the diencephalon (thalamus and hypothalamus) and telencephalon (two separate cerebral hemispheres)
• Spinal Cord


  a major part of the central nervous system which conducts sensory and motor nerve impulses to and from the brain. Cite for information integration an processing. Involved in primitive processes such as walking, urination and sex organ function