Chapter12 Flashcards
Central Nervous System
Brain and spinal cord of dorsal body cavity
Peripheral Nervous system
Nerves that extend from brain and spinal corrd and also cranial nerves
Somatic Sensory
Touch, pain, pressure, vibration, temperature, and proprioception in skin (hearing, equilibrium, vision)
Visceral Sensory
Stretch pain, tem, chemical changes, and irritation in viscera, nausea and hunger (taste, smell)
Somatic Nervous System
Motor innervation of all skeletal muscles (Motor (efferent) division)
Autonomic nervious system
Motor innervation of smooth muscle, cardiac muscle, and glands (Motor (efferent) division)
Neuroglia
Small cells that surround and wrap delicate neurons
Neurons
Excitable cells that transmit electrical signals
Astrocytes
Support neurons, capillary, and nueron exchange, guide migration, control chemical environment
Microglial
Monitor neurons, migrate toward injured neurons, phagocytize microorganisms and neuronal debris
Ependymal Cells
Line cavities to form permeable barrier between cerebrospinal fluid (CSF) in cavities and tissue fluid bathing CNS Cells
Olidgodendrocytes
Processes wrap CNS Nerve fibers, forming insulating myelin sheaths
Satellite cells
surround neuron cell bodies in PNS, function similar to astrocytes of CNS
Schwann Cells
Surround PNS fibers and form myelin sheaths in thicker nerve fibers, regeneration of PNS fibers
Tracts
Bundles of neuron processes in CNS
Nerves
Bundles of neuron processes in PNS
Dendrites
Short, tapering, diffusely branched processes, conveys incoming messages toward cell body as graded potential
Anterograde
away from cell body (mitochondria, neurotransmitters)
Retrograde
Toward cell body (organelles to be degraded, signal molecuels, viruses, and bacterial toxins)
Myelin Sheath
Composed of myelin, a whitish, protein-lipid substance, protects and electrically insulates axon, increases speed of nerve impulses
Nodes of Ranvier
Myelin sheath gaps between schwann cells
White Matter
Regions of brain and spinal cord with myelinated fibers
Gray Mater
Neuron cell bodies and nonmyelinated fibers
multipolar
3 or more processes, 1 axon, other dendrites
bipolar
2 processes, 1 axon and 1 dendrite (rare, retina and olfactory)
Unipolar
1 short process, divides T-like, both branches considered axons
Leakage Channels
Always open
Gated
Part of protein changes shape to open/close channel
Chemically gated (ligand-gated)
Channels: open with binding of a neurotransmitter
Voltage-gated
Channels: open and close in response to changes in membrane potential
Mechanically gated
Channels: open and close in response to physical deformation of receptors; sensory
Gated Channels
When open, ions diffuse quickly across membrane along electrochemical gradients
ECF
Higher concentration of NA+, balanced chiefly by chloride ions (Cl-)
ICF
Higher concentration of K+, balanced by negative charged protein
Na+ Channels Have 2 voltage-Sensitive gates
Activation Gates: closed at rest, open with depolarization; Inactivation Gates: open at rest; block channel once it is operational
Threshold
For axon to fire, depolarization must reach threshold
Axon Diameter
Larger diameter fibers = less resistance to current flow so faster
Saltatory Conduction
30x faster, Voltage-gated Na+ channels are located at myelin sheath gaps. Electrical signal appears to jump rapidly from gap to gap
Synapses
Junctions that mediate information transfer in neurons
Presynaptic Neuron
Neuron conducting impulses toward synapse
Postsynaptic Neuron
Neuron transmitting electrical signal away from synapse
Electrical Synapses
Neurons electrically coupled by gap junctions. Communication very rapid, synchronized. Less common but more abundant in embryonic nervous tissue
Synaptic Cleft
30-50 nm wide, prevents nerve impulses from directly passing from one neuron to next, unidirectional
Summate
When Excitatory postsynaptic potential and Inhibitory postsynaptic potential together can influence a postsynaptic neuron
Biogenic Amines
Broadly distributed in brain. Play roles in emotional behaviors and biological clock
Acetylcholine (Ach)
Released at neuromuscular junctions and by some CNS and ANS neurons. Degraded by enzyme acetylcholinesterase
Peptides: Substance P
Mediator of pain signals
Peptides: Endorphins
Beta endorphin, dynorphin and enkephalins. Act as natural opiates; reduce pain perception
Peptides: Gut-Brain peptides
Somatostatin and cholecystokinin
Direct Action
neurotransmitter binds to and opens ion channels. Promotes rapid responses by altering membrane potential
