chapter 38 nervous system. learning objectives describe the evolution of nervous system list the...
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Chapter 38
Nervous System
Learning Objectives
Describe the evolution of nervous system List the functions and location of the cerebrum,
thalamus, hypothalamus, midbrain, cerebellum, pons, medulla oblongata, basal nucleii, amygdala and hippocampus of the limbic system
Differentiate the somatic and autonomic systems
Diagram the spinal reflex circuit Differentiate functions of the left and right
hemisphere
Learning Objectives
Diagram the lobes of the cerebrum according to function and anatomy
Discuss the process of memory Debate the existence of consciousness Explain the various types of neurological
disorder incidence and symptoms
Invertebrate Nervous Systems (1)
Simplest nervous systems: The nerve nets of cnidarians
Echinoderms have modified nerve nets, with some neurons grouped into nerves
Invertebrate Nervous Systems (2)
Flatworms, arthropods, and mollusks have a simple central nervous system (CNS)Ganglia in the head region (brain)
Peripheral nervous system (PNS) Nerve cords from central ganglia to rest of body
Fig. 38.1c, p. 869
c. Planarian (flatworm)
Eyespot
Ganglia
Longitudinal nerve cords
Fig. 38.1d, p. 869
d. Arthropod (grasshopper)
Dorsal ganglia
Ventral ganglion
Ganglia of ventral nerve cord
Fig. 38.1e, p. 869
e. Mollusk (octopus)
Ganglia associated with internal organs
Optic lobe
Frontal lobes
Lobed brain
Eye
Chordate Nervous Systems
CNS Large brain located in the headHollow spinal cord
PNS All the nerves and ganglia connecting CNS to the
rest of the body
Development in Vertebrates
Vertebrate embryoAnterior end of neural tube develops into brain Rest develops into spinal cord
Embryonic brain enlarges into forebrain, midbrain, and hindbrainDevelop into adult structures
Fig. 38.2a, p. 870
Regions in 4-week embryo
Regions in 5-week embryo
Regions in adult
Functions in adultNeural tube
Telencephalon Telencephalon (cerebrum)
Higher functions, such as thought, action, and communication
Forebrain Diencephalon ThalamusCoordinates sensory input and relays it to cerebellum
Hypothalamus Center for homeostatic control of internal environment
Midbrain Mesencephalon Midbrain Coordinates involuntary reactions and relays signals to telencephalon
Hindbrain Metencephalon CerebellumIntegrates signals for muscle movement
Pons Center for information flow between cerebellum and telencephalon
MyelencephalonMedulla oblongata
Controls many involuntary tasks
Fig. 38.2e, p. 870
Hemisphere of cerebrum
Hypothalamus
Thalamus
Brain stem: Midbrain
Cerebellum
Spinal cord Central canal
Adult brain regions
Pons
Medulla oblongata
The Peripheral Nervous System
Somatic system controls skeletal musclesVoluntary body movements Involuntary muscle contractions that maintain
balance, posture, muscle tone
Autonomic system controls involuntary functions Sympathetic systemParasympathetic system
Fig. 38.4, p. 872
Parasympathetic Division Sympathetic Division
Constricts pupil; adjusts eye for near vision
EyesDilates pupil; adjusts eye for far vision
Optic nerveEyes
Cranial nervesStimulates secretion
Salivary glands Salivary
glands Inhibits secretion
Vagus nerveDecreases
heart rate Heart Heart Increases heart rate
Constricts bronchioles (airways)
LungsLungs Dilates
bronchiolesStimulates stomach activity
StomachStomach Inhibits stomach
activityInhibits glucose release
LiverLiver
Stimulates glucose release
Stimulates activity
IntestinesIntestines Inhibits activity
Stimulates contraction (emptying)
Bladder Bladder Relaxes bladder muscles
Stimulates penile or clitoral arousal
Chain of sympathetic
ganglia
Genitals GenitalsInhibits penile or clitoral arousal
Spinal nerves
The Spinal Cord
Carries signals between the brain and the PNS
Its neuron circuits control reflex muscular movements and some autonomic reflexes
Fig. 38.5, p. 873
1 A pain receptor in the finger stimulates an afferent neuron.
2 The afferent neuron transmits the impulses to the spinal cord.
3 Interneurons integrate the information. Interneuron
connections leading to brain
Integrating interneurons in spinal cord
Stimulus Ganglion
Spinal nerve
Central canal
Gray matter
White matter
Response Biceps muscle (flexor) contractsHand
withdrawn
4 One efferent neuron stimulates the flexor muscle to contract.
Effector5 The other efferent neuron sends inhibitory signals that keep the extensor muscle from contracting.6 The flexor contracts,
withdrawing the hand from the pain.
Triceps muscle (extensor) relaxes
Major Brain Structures
Cerebrum
Brain stemMedulla Pons Midbrain
Thalamus and hypothalamus
Structures of the Cerebrum
Right and left cerebral hemispheresConnected by corpus callosum
Cerebral cortex Thin gray matter covering core of white matter
Basal nucleiCollections of gray matter deep in telencephalon
Protecting the CNS
Cerebrospinal fluid provides nutrients and cushions the CNS
A blood-brain barrier allows only selected substances to enter the cerebrospinal fluid
Fig. 38.6, p. 874
Layer of cerebrospinal fluid between meninges
Ventricles
Central canal of spinal cord
Cerebral cortex (gray matter)
White matter
Corpus callosum
Basal nuclei (gray matter)
ThalamusVentricles
Right cerebral hemisphere
Left cerebral hemisphere
Functions of the Brain Stem
Gray-matter centers in pons and medulla control involuntary functions
Centers in midbrain coordinate responses to visual and auditory sensory inputs
Reticular formation Receives sensory inputs from the bodySends outputs to cerebral cortex that help maintain balance,
posture, muscle toneRegulates states of wakefulness and sleep
Fig. 38.8, p. 875
Midbrain
PonsCerebellum
Reticular formation
Medulla
Fig. 38.7, p. 875
Front of brain
Functions of the Cerebellum
Integrates sensory inputs to coordinate body movementsPositions of muscles and jointsVisual and auditory information
The Telencephalon’s Subcortical Gray-Matter Centers Thalamus
Receives, filters, and relays sensory and motor information to/from regions of cerebral cortex
Hypothalamus Regulates basic homeostatic functions of body Contributes to endocrine control of body functions
Basal nuclei Affect fine-tuning of body movements
The Limbic System
StructuresParts of thalamus, hypothalamus, basal nuclei Amygdala and hippocampus
FunctionsControls emotions Influences basic body functions controlled by
hypothalamus and brain stem
Fig. 38.9, p. 876
Cerebrum
Thalamus Gathers sensory information before distribution to higher areas
Basal nuclei
Olfactory bulbs
Hypothalamus Amygdala Controls emotions, activates “fight or flight” self-preservation reactions
Hippocampus Involved mainly with memory
The Cerebral Cortex
Primary somatosensory areas Register information on touch, pain, temperature,
and pressure from all parts of the bodyRight cerebral hemisphere receives sensory
information from left side of body and vice versa Primary motor areas control voluntary
movements of skeletal muscles
Fig. 38.11, p. 878
Front
Primary somatosensory area of left hemisphere
Primary motor area of left hemisphere
Back
Cross-sectional view Cross-sectional view
Left hemisphere
Lefthemisphere
Association Areas of Cerebral Cortex Integrate sensory information and formulate
responses passed on to primary motor areas Wernicke’s area
Integrates visual, auditory, other sensory information into comprehension of language
Broca’s area Coordinates movements of lips, tongue, jaws,
other structures to produce sounds of speech
Fig. 38.10, p. 877
General motor association area
Primary motor area
Frontal Association area(planning,personality)
Primary somatosensory area
General sensory association area
Parietal lobeFrontal
lobeTaste
Wernicke’s area (understanding language)
Visual association area
SmellTemporal lobe
Occ
ipita
l lo
be
Broca’s area (expressing language)
Primary visual cortex (visual input)
Auditory area (hearing input)
Auditory association area
Facial recognition area (on inner side of cortex)
Cerebellum
Brain stem
Lateralization of the Cerebral Hemispheres Left hemisphere functions
Spoken and written language, abstract reasoning, precise mathematical calculations
Right hemisphere functionsNonverbal conceptualizing, mathematical estimation, intuitive
thinking, spatial recognition, artistic and musical abilities
Equal functionsLong-term memory and consciousness
Memory
Storage and retrieval of a sensory or motor experience or thought
Short-term memory involves temporary storage of information
Long-term memory is essentially permanent
Learning
Modification of a response through comparisons made with information or experiences stored in memory
Consciousness
Awareness of ourselves, our identity, and our surroundings
Varies through states from full alertness to sleep
Controlled by the reticular activating system
Fig. 38.13, p. 882
Awake (beta waves)
Eyes closed, relaxed (alpha waves)
Dozing (theta waves)
Deep sleep (delta waves)
Time (sec)
Major Diseases of the Brain
Autism Spectrum Disorder ADHD Alzheimer’s Disease/Dementia Schizophrenia
Autism Spectrum Disorder
In 2006, 1% or one child in every 110 was classified as having an ASD
Males: 1:70; females: 1:315. Increased 57% from 2002
(Rice, December 18, 2009 / 58(SS10);1-20).
ASD
People with autistic disorder usually have significant language delays, social and communication challenges, and unusual behaviors and interests
People with Asperger syndrome usually have some milder symptoms of autistic disorder. They might have social challenges and unusual behaviors and interests. However, they typically do not have problems with language or intellectual disability.
ADHD
4.5 million children 5-17 years of age have ever been diagnosed with ADHD as of 2006.
3%-7% of school-aged children suffer from ADHD. Some studies have estimated higher rates in community samples
Boys (9.5%) are more likely than girls (5.9%) to have been diagnosed with ADHD. Diagnosis of ADHD increased an average of 3% per year from 1997 to 2006
(http://www.cdc.gov/ncbddd/adhd/data.html)
Types of ADHD
Predominantly Inattentive Type: Lack of organization or finish a task, Unable to pay attention to details, or to follow instructions or conversations. Easily distracted or forgets details of daily routines.
Predominantly Hyperactive-Impulsive Type: fidgets and talks a lot. hard to sit still for long (e.g., for a meal or while doing homework). Smaller children may run, jump or climb constantly. Feels restless and has trouble with impulsivity. May interrupt others a lot, grab things from people, or speak at inappropriate times Combined Type: Symptoms of the above two types are equally present in the person
Alzheimer’s Disease/Dementia
About 5% ages 65-74 year old About 50% over 80 years old An estimated 5 million Americans have Alzheimer’s
disease. This number has doubled since 1980 It is expected to be as high as 13.4 million by 2050 Individuals with Alzheimer’s disease make up less than
13 percent of the Medicare population, yet they account for 34 percent of Medicare spending.*
How old will you be in 2050? Who is paying the bill?
Schizophrenia
Affects 1.1 percent of the population Onset usually after age 18 Later in women Often addicted to nicotine and other
substances Genetically linked
Symptoms
Positive: Hallucinations (voices are common) Delusions (religious or alien, or authority) Thought disorders Movement disorders Negative: Absence of pleasure, planning, enjoyment (affect),
speaking, etc. Cognitive defects: Little understanding, trouble focusing, and little memory