Download Chapter 48 p. 1040-1053

Stephanie Bobbitt
Chapter 48) Nervous Systems p. 1040-1053
- Vertebrate Nervous Systems
o Vertebrate nervous systems have central and
peripheral components
 have distinct central and peripheral
elements and lots of cephalization
 CNS: brain (integrative power) + spinal
cord (integrates simple responses and
transmits info to and from brain
 PNS: transmits info to and from cns and
regulates internal environment
 cns derived from embryo’s hollow nerve
cord – brain and spinal cord have fluid
filled spaces
 central canal: part of spinal cord that is
continuous with brain ventricles: spaces
full of cerebrospinal fluid: formed in
brain by blood filtration, conveys
nutrients, hormones, and wbcs across
blood-brain barrier, also a shock
absorbed
 meninges: connective tissues protecting
the brain and spinal cord
 white matter: bundles of axons with
myelin sheath
 gray matter: dendrites, unmyelinated
axons, and nerve-cell bodies (nuclei)
o The divisions of the peripheral nervous
system interact in maintaining
homeostasis
 cranial nerves: made in brain;
innervate organs in upper body; have
motor and sensory neurons
 spinal nerves: made in spinal cord;
innervate entire body; have motor and
sensory neurons
 sensory division: sensory or afferent
neurons that communicate info to
CNS from sensory receptors; motor
division: motor or efferent neurons
that communicate signals from CNS to
effector cells
 somatic nervous system: carries
signals to skeletal muscles in response
to external stimuli; more voluntary
 autonomic nervous system: carries
signals that regulate internal
environment; control smooth and
cardiac muscles and organs; more
involuntary
 sympathetic division: arousal and energy generation (faster heartbeat, liver changes glycogen to
glucose, bronchi dilate, digestion inhibited, adrenaline secreted)
 parasympathetic division: calming and return to self-maintenance
 drop in temperature = hypothalamus signals ANS to constrict blood vessels to lose less heat and
SNS to cause shivering
o
Embryonic development of the vertebrate brain reflects its evolution from three anterior bulges of
the neural tube
 forebrain, midbrain, and hindbrain are obvious when the neural tube differentiates
 more dividedness = more complex integration possible
 cerebrum: center of homeostatic control and integration; from forebrain
 later in development – telencephalon and diencephalon from forebrain, mesencephalon from
midbrain, and metencephalon
and myelencephalon from
hindbrain
 quick growth of telencephalon
makes to halves of cerebrum –
left and right cerebral
hemispheres; has white matter,
internal gray matter, and outer
gray matter (cerebral cortex)
 thalamus, epithalamus, and
hypothalamus develop from
diencephalon
 brainstem from mesencephalon
(midbrain), metencephalon
(pons; also cerebellum), and
myelencephalon (medulla
oblongata)
o
Evolutionary older structures of the vertebrate brain regulate essential automatic and integrative
functions
 The Brainstem
 brainstem function: homeostasis, movement coordination, conduction of information
 The Medulla and Pons
o brainstem centers have nerve cell bodies that send axons to cerebral cortex and
cerebellum, releasing neurotransmitters (norepinephrine, dopamine, serotonin,
acetylcholine) – cause attention, alertness, appetite, and motivation changes
o medulla oblongata: aka medulla; has centers for visceral (automatic) functions
(breathing, swallowing, digestion, etc.)
o pons: similar activities as medulla; ex: have nuclei to regulate medulla breathing centers
o other functions: data conduction (for complex movements like walking); axons carry
instructions from midbrain and forebrain to spinal cord by crossing from one CNS side
to the other while passing through medulla
 The Midbrain
o midbrain: has sensory receipt and integration centers; sends sensory info along neurons
to forebrain parts
o midbrain nuclei are inferior and superior colliculi (part of auditory and visual systems)
 The Reticular System, Arousal, and Sleep
 arousal: state of awareness of external world; counterpart is sleep
 reticular formation: system of neurons pass through brain stem core
 reticular activating system (RAS): regulates sleep and arousal; chooses which info reaches
cerebral cortex – more received = more alert
 brain stem can regulate sleep and wakefulness; serotonin may be neurotransmitter of sleepproduction centers; drinking milk induces sleep since it has tryptophan (makes serotonin)
 electroencephalogram (EEG): records electrical activity in brain
 less mental activity usually means more synchronous brain waves
 sleep may be involved in consolidation of learning and memory
The Cerebellum
 cerebellum: coordination and error
checking; probably involved in
learning and remembering motor
responses
 receives sensory info about joint
position and muscle length, auditory
and visual systems
 receives motor info and provides automatic coordination (ex: hand-eye coordination)
 The Thalamus and Hypothalamus
 epithalamus: has choroids plexus (capillary cluster that makes cerebrospinal fluid) and
pineal gland (has endocrine function)
 thalamus: main sensory input center for cerebrum and output for motor info
 hypothalamus: very important for homeostatic regulation; source of posterior pituitary
hormones and hormones acting on anterior pituitary; has body thermostat
 hypothalamic nuclei: sexual and mating behaviors, fight-or-flight response, pleasure
 The Hypothalamus and Circadian Rhythms
o biological clock: component of circadian rhythms
o suprachiasmatic nuclei (SCN): in mammal’s hypothalamus; acts as biological clock
o external sues for circadian rhythms, like light; ex: when squirrel is only in light or
darkness, their internal clock’s timing is different than normal, so external cues are used
to adjust their rhythms to be 24 hours
The cerebrum is the most highly evolved structure of the mammalian brain
 cerebrum is divided into cerebral hemispheres
 basal nuclei: in white matter of cerebrum; centers for planning and learning movements
 cerebral cortex (gray matter): has neocortex (only in mammals; 6 sheets of neurons)
 bigger surface area of neocortex and size of cerebral cortex = greater cognitive abilities and more
sophisticated movements
 left side of brain control right side of body, vice versa
 corpus callosum: band of fibers (white matter); communicates b/t right and left hemispheres
 cognition: process of knowing (awareness and judgment); cognitive brain functions: learning,
decision making, consciousness, sensory awareness of surroundings
Regions of the cerebrum are specialized for different functions
 four lobes of cerebral cortex: frontal, temporal, occipital, and parietal
 primary motor cortex and primary somatosensory cortex are boundary b/t frontal and parietal;
motor = sends commands to skeletal muscles; somatosensory = receives and partially integrates
signals from touch, pain, pressure, temperature receptors
 Integrative Function of the Association Areas

o
o


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sensory info enters cortex via thalamus  goes to primary sensory areas in lobes (visual 
occipital, auditory  temporal, somatosensory  parietal, olfactory info  inferior region of
frontal)  sent to association areas to be integrated
 bigger neocoretx = bigger association area
Lateralization of Brain Function
 left hemisphere = language, math, logic, serial sequences of info, detail, speed-optimized
activities, etc.; right hemisphere = pattern and face recognition, spatial relations, nonverbal
ideation, emotional processing
Language and Speech
 understand language, but not speak = frontal lobe damage (Broca’s area)

o
read a word out loud = instruction activates visual cortex and Broca’s area, frontal and
temporal activated to attach meaning to words
 Emotion
 limbic system: hippocampus + olfactory cortex + inner cortex’s lobes + some hypothalamus
and thalamus = ring around brain stem; generates emotions by interacting with sensory
areas of neocortex and
other centers
 limbic system responsible
for infant nurturing,
emotional bonding b/t
individuals, laughing,
crying, attaches feelings to
brain stem’s feeding,
aggression, and sexuality
 amygdala: nucleus in
temporal lobe; recognizes
emotion of facial
expressions and lays down
emotional memories
 hippocampus: important
to emotional memory
system
 Memory and Learning
 short-term memory: frontal lobes
 long-term memory: hippocampus and limbic system
 transfer from short-term to long-term = rehearsal, positive/negative emotional states
mediated by amygdala, and associating new data with previous data (ex: easier to learn new
card game if you have played other card games)
 areas of cerebral cortex store and retrieve words and images from mental dictionary
 memorization requires rapid changes in strength of nerve connections
 long-term depression (LTD): postsynaptic cell’s decreased responsiveness to action potential
 long-term potentiation(LTP): enhanced responsiveness to action potentials; associated with
release of neurotransmitter glutamate (binds with receptors to open gated channels that let
in a lot of calcium, which triggers more enzyme activity
 Human Consciousness
 more studies have been done about consciousness, may require understanding whole-brain
activity patterns
Research on neuron development and neural stem cells may lead to new approaches for treating
CNS injuries and diseases
 CNS cannot repair itself when damaged like PNS can
 Nerve Cell Development
 molecular signposts direct the way an axon grows to reach its target cell
 growth cone: responsive region at leading edge of axon; has receptors on its membrane that
bind to signal molecules released by target cells (axon may respond by growing towards or
away from target cell)
 cell adhesion molecules (CAMs): on axon’s growth cone; attach to complementary CAMs on
surrounding cells to provide a track
 nerve growth factor (released by astrocytes) and growth-promoting proteins stimulate
growth of axons
 the basic method of axon guidance is similar b/t many organisms
 Neural Stem Cells
 new nerve cells are made during adulthood in hippocampus
 stimulating minds and exercising bodies may = greater learning capacity
 the new adult cells must come from stem cells; studying stem cells is limited