Exam 2 Study Guide Flashcards
(75 cards)
Describe the divisions of the nervous system and the subdivisions of the peripheral nervous
system
the nervous system splits into the central nervous system (CNS) and the peripheral nervous system (PNS). the CNS includes the brain and spinal cord. the PNS includes cranial nerves, spinal nerves, and ganglia. the subdivisions of the peripheral nervous system are the somatic nervous system and the autonomic nervous system. the autonomic nervous system splits into the sympathetic division and the parasympathetic division
What are the 2 types of nervous system cells? What is their role?
the two types of nervous system cells are neurons and neuroglia. neurons are electrically excitable cells that transmit electric signals. neruoglia (glial cells) are “helper” cells that have many functions to support neurons
Understand the functions of astrocytes, microglia, ependymal cells, oligodendrocytes,
Schwann cells, and satellite cells
astrocytes: most abundant, cover capillaries, support, brace, anchor neurons to nutrient supply, guide migration of new neurons, control chemical environment
microglia: small, ovoid cells with spiny processes, phagocytes monitor neuron health
schwann cells (neurolemmocytes): maintain the myelin sheath around PNS nerve cells
satellite cells: surround neuron cell bodies with ganglia
Understand the function of sensory, interneurons, and motor neurons
sensory (afferent neurons): detect changes in body and environment, information transmitted to brain and spinal cord
interneurons: between sensory and motor pathways in CNS, 90% of neurons, process, store, retrieve information
motor (efferent) neurons: send signals out to muscles and gland cells, organs that carry out response = effectors
Describe the anatomy of the textbook neuron and understand the role of anatomies in signal
transmission
dendrites are the receptive region, the soma is the cell body and receptive region, the nissl bodies are similar to the rough ER, the axon hillock is the summing center of impulse, the axon is the long conducting process (any arm like extension)
axon terminals: secretion of NT
What is the resting membrane potential of an electrically excitable cell? What generates
this membrane potential?
it is the potential difference across the plasma membrane (-70 mV), it is generated by different concentrations of Na+, K+, Cl-, and protein anions (A-)
Understand how electrical and chemical gradients create the electrochemical gradient.
How does this gradient impact how ions like sodium and potassium will move during signal
transmission?
ions will flow down their chemical gradient (high to low) and will also flow down their electrical gradient (move to the area of opposite charge). the potassium and sodium want to be on the opposite of their charge.
Differentiate between the different types of ion channels
passive, or leakage: always open
chemically (ligand) gated: open with binding of specific neurotransmitter
mechanically gated: open and close due to physical deformation
voltage-gated: open and close in response to membrane potential
Describe the features of a graded potential and how/where they are propagated.
Differentiate between the 2 types of graded potential
graded potentials are short-lived, localized changes in membrane potential. they begin in the dendrites of a neuron. they decrease in intensity with distance from initial site. magnitude varies directly with strength of stimulus, if graded potential strong enough it can initiate an action potential.
excitatory postsynaptic potential (EPSP): causes local depolarization, increases membrane potential (closer to causing action potential), in favor of action potential
inhibitory postsynaptic potential (EPSP): causes local membrane hyperpolarization, more negative, inhibits action potential
Understand how summation of graded potentials can lead to an action potential
if the sum of the graded potentials is of sufficient voltage then an AP is generated at the axon hillock, if their collective voltage is less than the threshold value, then no AP is generated
What is an action potential? What threshold is needed to reach AP? How does an AP differ
from a graded potential?
an action potential is a short reversal of membrane potential total amplitude of 100 mV, if the threshold of -55 mV is reached, an AP is propagated down the axon. it is only generated by muscle cells and neurons and does not decrease in strength over distance, it is an all or nothing response
Describe (in detail) the steps involved with propagation of an action potential including the resting, depolarization, repolarization, and hyperpolarization phases, particularly with
respect to the sodium and potassium gated channels
resting state: sodium and potassium channels are closed, each sodium channel has two voltage regulated gates; the activation gate (closed in resting state) and the inactivation gate (open in resting state)
depolarization phase: sodium permeability increases and the membrane potential reverse, sodium gates open and potassium gates close and threshold is reached for the critical level of depolarization
repolarization: sodium inactivation gates close, membrane permeability to sodium goes back down to resting levels, as sodium gates close, voltage-sensitive potassium gates open, potassium exits and internal negativity of resting neuron is restored
hyperpolarization: potassium gates remain open, excessive efflux of potassium, efflux causes hyperpolarization of the membrane (undershoot), neuron insensitive to stimulus and depolarization
What is a refractory period? What are the 2 types of refractory periods in nerve cells? When does each occur? How do they differ?
a brief period after an action potential during which the neuron cannot fire another action potential
absolute refractory period: time from opening of sodium activation gates until closing of inactivation gates - prevents generation of AP and ensures that each AP is separates and enforces one-way transmission of nerve impulses
relative refractory period: interval following absolute refractory period when sodium gates are closed, potassium gates are open and repolarization is occurring. the threshold level is elevated, allowing strong stimuli to increase frequency of AP events
Identify how signal intensity is determined with an AP
AP occurs completely or not at all
Understand what factors influence rate of signal conduction velocity
it widely varies among neurons and it is determined by the diameter of the axon (a larger diameter means a faster impulse) and the presence of a myelin sheath causes the impulse speed to increase dramatically
What is myelin and what is its role? How is the myelin sheath formed?
myelin is the fatty, white, segmented sheath around many long axons. it’s function is protection, electrical insulation, and increases the speed of electric impulses. it is formed as schwann cells form and wrap around the axon in a coil
Describe how saltatory conduction occurs and understand why this leads to faster signal
transmission
it happens in myelinated axons and it is where the current only passes at the nodes of Ranvier (gaps in the myelin sheath), voltage gated sodium channels are concentrated at these nodes and AP is triggered only at these nodes as they jump from node to node. it is faster than conduction along unmyelinated axons
What is a synapse? What is the difference between a presynaptic and postsynaptic neuron?
presynaptic neurons conduct impulses toward the synapse, postsynaptic neurons transmit impulses away from the synapse
Describe (in detail) the process by which signals are transmitted at the synapse. This
includes release of NT from the axon terminal, binding on the postsynaptic neuron, and
what occurs on the postsynaptic neuron. What happens to NT released into a synapse
Identify several different types of neurotransmitters
Describe how acetylcholine is produced, released and degraded at the synaptic terminal
Understand the relationship between the catecholamines and where they are synthesized. How do the synapses of dopamine and norepinephrine differ? How are they the same?
What is sensation and perception of stimuli? What are the 3 parts involved with sensation
of a stimulus?
Describe the different types of sensory receptors based upon the stimulus they respond to
