Flashcards in Vertebrates 13 - Nervous system Deck (22)
Divisions of the PNS
Afferent, Efferent: Somatic, Autonomic: Sympathetic and parasympathetic
Efferent; Afferent; Somatic
Away from brain; toward the brain; skeletal muscles
Sympathetic and parasympathetic
They are antagonists and oppose each other
Outnumber neurons, small. Support, development (form first and help neurons grow), function (some conduction, myelination)
Glial cell types
Oligodendrocytes and astrocytes (CNS), Schwann cells (PNS). Schwann and oligoden. are pretty similar and mke myelin. Astrocytes affect signaling b/w neurons and release growth factors
Sensory, motor, interneurons.
Characteristics of neurons
Post-mitotic, membrane proteins respond to voltage (excitable). Pass signals at synapses (chem or elec). Intricate connection patterns.
General neuron structure
Dendrites: all around cell body, short, input; Soma: cell metabolism; Axon hillock: where axon leaves cell body, action potential begins here; Axon: myelinated and non, signal travel, usually only one. Synaptic terminals/boutons: end of axon, signal passed on; synapse: where two neurons communicate
Amphioxus (cephalochordata) nervous system
Hollow dorsal nerve cord, no distinct brian, only 20000 neurons. Neuromuscular junction unique: muscles send projections to nerve cord (backwards!). No myelin. Simple photo-, chemo- and mechanoreceptors. Scattered.
Lampreys nervous system
Simple brain. Diffuse autonomic nervous system (ex. heart rate control, but no distinct nerves). No myelin. Elec and chem synapses. Smallest brain/body mass ratio.
Sharks nervous system
Brain/body mass ratio > bony fish, reptiles, amphibians. Autonomic NS more distinct. Myelin. Separate taste and smell receptors
Bony fish nervous system
Diverse brains, lateral line, Mauthner nerve cells (for escape - called C-start). Cerebrum mostly for smell
NS similar to fish. Cerebrum not well developed, mostly for smell. Similar nerves modified for limbs. Cerebellum less complex than fishes because it is coordinating in 2 planes.
Small brain/body ratio, but more developed cerebrum because it coordinates more there. thalamus important to relay info.
Brain/body ratio high. Cerebrum enlarged. Decreased sensory nerves (touch, smell - not as needed, sight more important). Cerebellum large and highly folded (more coordination
Brain/body ratio highest. Larger area in frontal and occipital lobes. High speed conduction (myelin)
Blue Whale NS
Largest brain (9-10kg), cerebrum highly folded, inferior colliculi enlarged (better sound sense)
Folding in brains
Creates more surface area, more rooms for layers. (wouldn’t fit it some animals’ heads!)
Brain/body mass ratio
Log/log graph, above line is high, below is low. Generally the larger the smarter. Humans, chimps, crows, porpoise are smart, lampreys, eels are dumb
Determining brain/body mass ratio in extinct species
Measure the size of the brain case. Troodon (velociraptor) considered smart, sauropods dumb.
Conundrums of brain/body mass ratio
Stingrays and dogfish have high ratio, but don’t seem to be intelligent. Smaller cerebrum and larger medulla or cerebellum responsible for this.