48.1
-See pg. 1012 for types of nervous systems in various animals.
-Information processing: Three stages of information processing: Sensory input from external stimuli and internal conditions
 sensory neurons, integration (analyzing and processing)  interneurons, and motor output  motor neurons communicate
with effector cells (muscle or endocrine cells). See fig. 48.4
-Dendrites: receive signals
-Axon hillock: where electrical
signals are generated
-Myelin sheath: lipid insulator
-Synapse: site of communication
-Glia (Greek for “glue”) :
astrocytes, radial glia,
oligodendrocytes, Schwann cells
-Astrocytes: structural support, facilitating information transfer, cause blood vessels near active neurons to dilate,
induce the formation of tight junctions between cells of the blood-brain barrier during development
-Radial Glia: form tracks along which newly formed neurons migrate from the neural tube
- Oligodendrocytes (CNS), Schwann cells (PNS): form myelin sheaths around axons
48.2
-Resting potential: The membrane potential of a neuron not transmitting signals, from -60 to -80 mV
-Gated ion channels open or close in response to stimuli, changing the membrane potential: Stretch-gated (respond to stretch),
ligand-gated (respond to chemicals/neurotransmitters), voltage-gated (respond to changes in potential)
48.3
-HYPERPOLARIZATION: Inside of the membrane becomes more negative
-DEPOLARIZATION: Inside of the membrane becomes more positive
-Action Potential: Once depolarizations reach a certain threshold, action potential is produced. ALL OR
NOTHING; magnitude is independent of strength of stimulus. (However, stronger stimuli produce higher
frequencies).
- A stimulus causes some sodium channels to open
-Sodium ions enter and depolarize the cell enough to reach the threshold
-Once the threshold is reached, many more sodium channels open and sodium ions flood the cell
-Once electric potential reaches 40 mV, sodium channels shut down and potassium channels open
-Efflux of K ions causes membrane potential to go down
-Na ions diffuse to next section of axon, sodium channels in that section open, and action potential regenerates.
-Refractory period: During falling phase, Na channels still closed, so action potential frequency is limited
-Conduction Speed: -Greater diameter of axon = faster conduction
-Myelin sheaths: Space efficiency; insulation has the same effect as increasing axon diameter
-Nodes of Ranvier: gaps in the myelin sheath where action potential is generated. Action potential appears to jump
from node to node in a mechanism called saltatory conduction.
48.4
Neuron Communication at Synapses: Two types of synapses: electrical and chemical (most are chemical)
-Chemical synapses: Action potential
stimulates opening of calcium channels.
Calcium releases synaptic vesicles from
microtubules. Neurotransmitters are
released by exocytosis.
Direct Synaptic Transmission: Neurotransmitters bind directly to ion channels and change membrane potential.
-Excitatory postsynaptic potentials (EPSPs) depolarize, Inhibitory postsynaptic potentials (IPSPs) hyperpolarize.
-EPSPs can combine to produce action potentials: Temporal and Spatial summation
Indirect Synaptic Transmission: A neurotransmitter activates a signal transduction pathway involving a second messenger.
Example: norepinephrine (see pg. 1024)
Neurotransmitters: Acetylcholine: most common; excitatory in skeletal muscle cells and inhibitory in cardiac muscle cells
-Biogenic Amines: Derived from amino acids. Examples include epinephrine, norepinephrine, dopamine, serotonin.
-Amino Acids and Peptides: gamma aminobutyric acid (GABA), glycine, glutamate, aspartate.
-Neuropeptides: short chains of amino acids formed by modification of larger proteins. Substance P mediates pain perception
while endorphins decrease pain perception.
-Gases: eg. NO and CO. Synthesized on demand. CO synthesized by heme oxygenase. CO regulates release of hormones from
the hypothalamus and hyperpolarizes smooth muscle cells.
48.5
-Central Nervous System (CNS): brain and spinal cord; Peripheral Nervous System (PNS): everything else
-Central canal and 4 ventricles of brain filled with cerebrospinal fluid filtered from blood  helps supply nutrients and
hormones to different parts of the brain and (in mammals) cushions the brain and spinal cord
-Gray matter: dendrites, unmyelinated axons, neuron cell bodies. White matter: bundles of myelinated axons
-Peripheral Nervous System (PNS): transmits info to and from CNS; helps regulate internal environment
-Somatic and Autonomic Nervous Systems; Somatic communicates with skeletal muscles in response to external
stimuli and Autonomic regulates internal environment (divided into 3 sections: sympathetic, parasympathetic, enteric)
-Sympathetic = arousal and energy generation,
parasympathetic = complete opposite
-Enteric Division: networks of neurons in the
digestive tract, pancreas, and gall bladder
Embryonic Development of the Brain
-The Brainstem: Homeostasis, coordination of movement, and
conduction of info to higher brain centres
-Medulla and pons: info transmission and coordination of
large-scale body movements
-Midbrain: Receipt and integration of sensory info
-Arousal and Sleep: Reticular Formation (Fig. 48.24)
-Medulla and pons have sleep centers,
midbrain has arousal center
-The Cerebellum: Coordination, motor skills; receives sensory info
about bones and muscles, and auditory and visual info
-The Diencephalon: Epithalamus, Thalamus, Hypothalamus; see pg. 1030
-The Cerebrum: Divided into right and left hemispheres, which are connected by the corpus callosum
-Neocortex/Cerebral cortex: outermost layer of cerebrum; most advanced in mammals; convolutions allow
high surface area
48.6
-Cerebral cortex has 4 lobes: frontal, temporal, occipital, and parietal. Each lobe has primary sensory areas and association
areas. Visual info goes to the occipital lobe; auditory to the temporal; somatosensory to the parietal lobe; olfactory to the
frontal.
-Motor commands: Action potentials from primary motor cortex  spinal cord  motor neurons  skeletal muscle cells
-Lateralization of cortical function: Left = language, math, logic, serial processing of info sequences. Right= pattern
recognition, face recognition, spatial relations, nonverbal thinking, emotional processing
-Language and speech: Wernicke's area (hearing words), visual cortex (seeing words), Broca's area (speaking words), frontal
and temporal areas (generating words).
-Emotions: LIMBIC SYSTEM - a ring of structures around the brainstem.
-Interacts with neocortex, mediating primary emotions; attaches emotions to survival; central to behaviours that
distinguish mammals.
-From early age, emotions associated with survival mechanisms; as brain matures and emotions become more
complex, neocortex becomes involved.
-Memory and learning: Short-term memory: unimportant discarded, important moved to long-term memory (requires
hippocampus). Recollection of memories involves transfer from long-term to short-term. Transfer of info is enhanced by
rehearsal, emotions, and knowledge of old data.
-Cellular mechanisms of learning: Sensitization: See Fig 48.31
-Long-term potentiation (LTP): Strength of synaptic transmission increases. See Fig. 48.32