Fig. 49-1

Chapter 49Chapter 49Nervous Systems

Functional magnetic resonance imaging (MRI) can be used to construct a 3-D map of brain activity

Fig. 49-2

(e) Insect (arthropod)

Segmentalganglia

Ventralnerve cord

Brain

(a) Hydra (cnidarian)

Nerve net

Nervering

Radialnerve

(b) Sea star (echinoderm)

Anteriornerve ring

Longitudinalnerve cords

(f) Chiton (mollusc) (g) Squid (mollusc)

Ganglia

Brain

Ganglia

(c) Planarian (flatworm)

Nervecords

Transversenerve

Brain

EyespotBrain

(d) Leech (annelid)

Segmentalganglia

Ventralnervecord

Brain

Spinalcord(dorsalnervecord)

Sensoryganglia

(h) Salamander (vertebrate)

a knee-jerk reflex

Whitematter

Cell body ofsensory neuron indorsal rootganglion

Spinal cord(cross section)

Graymatter

Hamstringmuscle

Quadricepsmuscle

Sensory neuron

Motor neuronInterneuron

Fig. 49-4Peripheral nervoussystem (PNS)

Cranialnerves

Brain

Central nervoussystem (CNS)

GangliaoutsideCNS

Spinalnerves

Spinal cord

The CNS is composed of the brain and spinal cordThe peripheral nervous system (PNS) is composed of nerves and ganglia

Fig. 49-5

Whitematter

Ventricles

Gray matter•cerebrospinal fluid neuron cell bodies, dendrites, and unmyelinated axons

–bundles of myelinated axons

Fig. 49-6

Oligodendrocyte

Microglialcell

Schwann cells

Ependy-malcell

Neuron AstrocyteCNS PNS

Capillary (a) Glia in vertebrates

(b) Astrocytes (LM)

VENTRICLE

Glia have numerous functions ◇ Epidermal cells promote circulation of cerebrospinal fluid

◇ Microglia protect the nervous system from microorganisms

◇ Oligodendrocytes and Schwann cells form the myelin sheaths around axons

◇ Astrocytes provide structural support for neurons, regulate extracellular ions and neurotransmitters, and induce the formation of a blood-brain barrier that regulates the chemical environment of the CNS

◇ Radial glia play a role in the embryonic development of the nervous system

Oligodendrocyte

Microglialcell

Schwann cells

Ependy-malcell

Neuron Astrocyte

CNS PNS

Capillary

(a) Glia in vertebrates

VENTRICLE

(b) Astrocytes (LM)

Fig. 49-7-2

Efferentneurons

Locomotion

Motorsystem

Autonomicnervous system

Afferent(sensory) neurons

PNS

Hearing

CirculationGas exchange DigestionHormone

action

Entericdivision

Sympatheticdivision

Parasympatheticdivision

carries signals to skeletal muscles and is voluntary

antagonistic effects

fight-or-flight” response “rest and digest

controls activity of the digestive tract, pancreas, and gall bladder

The Peripheral Nervous System

Fig. 49-8

Stimulates glucoserelease from liver;inhibits gallbladder

Dilates pupilof eye

Parasympathetic division Sympathetic division

Action on target organs:

Inhibits salivary gland secretion

Accelerates heart

Relaxes bronchiin lungs

Inhibits activityof stomach and

intestines

Inhibits activityof pancreas

Stimulatesadrenal medulla

Inhibits emptyingof bladder

Promotes ejaculation and vaginal contractions

Constricts pupilof eye

Stimulates salivarygland secretion

Constrictsbronchi in lungs

Slows heart

Stimulates activityof stomach and

intestines

Stimulates activityof pancreas

Stimulatesgallbladder

Promotes emptyingof bladder

Promotes erectionof genitals

Action on target organs:

Cervical

Sympatheticganglia

Thoracic

Lumbar

Synapse

Sacral

Fig. 49-8a

Dilates pupilof eye

Parasympathetic division Sympathetic division

Action on target organs:

Inhibits salivary gland secretion

Constricts pupilof eye

Stimulates salivarygland secretion

Constrictsbronchi in lungs

Slows heart

Stimulates activityof stomach and

intestines

Stimulates activityof pancreas

Stimulatesgallbladder

Action on target organs:

Cervical

Sympatheticganglia

Fig. 49-8b

Stimulates glucoserelease from liver;inhibits gallbladder

Parasympathetic division Sympathetic division

Accelerates heart

Relaxes bronchiin lungs

Inhibits activityof stomach and

intestines

Inhibits activityof pancreas

Stimulatesadrenal medulla

Inhibits emptyingof bladder

Promotes ejaculation and vaginal contractions

Promotes emptyingof bladder

Promotes erectionof genitals

Thoracic

Lumbar

Synapse

Sacral

Table 49-1

Fig. 49-9

Pons (part of brainstem), cerebellum

Forebrain

Midbrain

Hindbrain

Midbrain

Forebrain

Hindbrain

Telencephalon

Telencephalon

Diencephalon

Diencephalon

Mesencephalon

Mesencephalon

Metencephalon

Metencephalon

Myelencephalon

Myelencephalon

Spinal cord

Spinal cord

Cerebrum (includes cerebral cortex, white matter,basal nuclei)

Diencephalon (thalamus, hypothalamus, epithalamus)

Midbrain (part of brainstem)

Medulla oblongata (part of brainstem)

Pituitarygland

Cerebrum

Cerebellum

Central canal

Diencephalon:

Hypothalamus

Thalamus

Pineal gland(part of epithalamus)

Brainstem:

Midbrain

Pons

Medullaoblongata

(c) Adult(b) Embryo at 5 weeks(a) Embryo at 1 month

Fig. 49-9ab

Forebrain

Midbrain

Hindbrain

Midbrain

Forebrain

Hindbrain

Telencephalon

Telencephalon

Diencephalon

Diencephalon

Mesencephalon

Mesencephalon

Metencephalon

Metencephalon

Myelencephalon

Myelencephalon

Spinal cord

(b) Embryo at 5 weeks(a) Embryo at 1 month

Fig. 49-9c

Pons (part of brainstem), cerebellum

Spinal cord

Cerebrum (includes cerebral cortex, white matter,basal nuclei)

Diencephalon (thalamus, hypothalamus, epithalamus)

Midbrain (part of brainstem)

Medulla oblongata (part of brainstem)

Pituitarygland

Cerebrum

Cerebellum

Central canal

Diencephalon:

Hypothalamus

Thalamus

Pineal gland(part of epithalamus)

Brainstem:

Midbrain

Pons

Medullaoblongata

(c) Adult

Fig. 49-UN1

•The brainstem has three parts: the midbrain, the pons, and the medulla oblongata

• The midbrain contains centers for receipt and integration of sensory information

• The pons regulates breathing centers in the medulla

• The medulla oblongata contains centers that control several functions including breathing, cardiovascular activity, swallowing, vomiting, and digestion

Arousal and Sleep- reticular formation

• The brainstem and cerebrum control arousal and sleep

• The core of the brainstem has a diffuse network of neurons called the reticular formation

• This regulates the amount and type of information that reaches the cerebral cortex and affects alertness

• The hormone melatonin is released by the pineal gland and plays a role in bird and mammal sleep cycles

Fig. 49-10

Input from touch,pain, and temperaturereceptors

Reticular formation

Eye Input from nervesof ears

Fig. 49-11

High-frequency waves characteristic of wakefulness

Lefthemisphere

Time: 0 hours

Low-frequency waves characteristic of sleep

Righthemisphere

Location Time: 1 hour

Sleep is essential and may play a role in the consolidation of learning and memory

Dolphins sleep with one brain hemisphere at a time and are therefore able to swim while “asleep”

Fig. 49-UN2

The cerebellum

---is important for coordination and error checking during motor, perceptual, and cognitive functions---It is also involved in learning and remembering motor skills

Fig. 49-UN3

The diencephalon develops into three regions: the epithalamus, thalamus, and hypothalamus

---The epithalamus includes the pineal gland and generates cerebrospinal fluid from blood

---The thalamus is the main input center for sensory information to the cerebrum and the main output center for motor information leaving the cerebrum

---The hypothalamus regulates homeostasis and basic survival behaviors such as feeding, fighting, fleeing, and reproducing

Diencephalon

Biological Clock Regulation by the Hypothalamus

• The hypothalamus also regulates circadian rhythms such as the sleep/wake cycle

• Mammals usually have a pair of suprachiasmatic nuclei (SCN) in the hypothalamus that function as a biological clock

• Biological clocks usually require external cues to remain synchronized with environmental cycles

Fig. 49-12

Beforeprocedures

RESULTS

Cir

cad

ian

cyc

le p

eri

od

(h

ou

rs)

After surgeryand transplant

hamsterWild-type hamster

Wild-type hamster withSCN from hamster

24

20

23

22

21

19

hamster with SCNfrom wild-type hamster

•The cerebrum develops from the embryonic telencephalon

The cerebrum has right and left cerebral hemispheres

---Each cerebral hemisphere consists of a cerebral cortex (gray matter) overlying white matter and basal nuclei

---In humans, the cerebral cortex is the largest and most complex part of the brain

---The basal nuclei are important centers for planning and learning movement sequences

---A thick band of axons called the corpus callosum provides communication between the right and left cerebral cortices

---The right half of the cerebral cortex controls the left side of the body, and vice versa

Cerebrum

Fig. 49-13

Corpuscallosum

Thalamus

Left cerebralhemisphere

Right cerebralhemisphere

Cerebralcortex

Basalnuclei

Evolution of Cognition in Vertebrates

• The outermost layer of the cerebral cortex has a different arrangement in birds and mammals

• In mammals, the cerebral cortex has a convoluted surface called the neocortex, which was previously thought to be required for cognition

• Cognition is the perception and reasoning that form knowledge

• However, it has recently been shown that birds also demonstrate cognition even though they lack a neocortex

Fig. 49-14

Thalamus

Cerebralcortex

Pallium Cerebrum

Thalamus

CerebrumCerebellum

Cerebellum

MidbrainMidbrain

HindbrainHindbrain

Human brainAvian brain

Avian brainto scale

Concept 49.3: The cerebral cortex controls voluntary movement and cognitive functions

• Each side of the cerebral cortex has four lobes: frontal, temporal, occipital, and parietal

• Each lobe contains primary sensory areas and association areas where information is integrated

Thalamus directs different types of inputs to distinct locations

Primary sensory areas association areasthe frontal association area (plan actions and movement) motor cortex (at the rear of the frontal lobe) brain stem Spinal cord

Fig. 49-15

Speech

Occipital lobe: visual

Vision

Temporal lobe: auditory

Frontal lobe: olfactory information

Parietal lobe: somatosensory input, tastes

Somatosensoryassociationarea

Frontalassociationarea

Visualassociationarea

Reading

Taste

Hearing

Auditoryassociationarea

Speech

Smell

Mo

tor

cort

exS

omat

osen

sory

cor

tex

Thalamus directs different types of inputs to distinct locations

Primary sensory areas association areasthe frontal association area (plan actions and movement) motor cortex (at the rear of the frontal lobe) brain stem Spinal cord

Information Processing in the Cerebral Cortex

• The cerebral cortex receives input from sensory organs and somatosensory receptors (touch, pain, pressure, temperature, and the position of muscles and limbs)

• Specific types of sensory input enter the primary sensory areas of the brain lobes

• Adjacent areas process particular features in the sensory input and integrate information from different sensory areas

• In the somatosensory and motor cortex, neurons are distributed according to the body part that generates sensory input or receives motor input

Fig. 49-16

Primarysomatosensory cortex

Frontal lobe

Pharynx

Parietal lobe

TeethGumsJaw

Tongue

Lips

Face

Nose

EyeThum

bFingers

Hand

ForearmE

lbo

wU

pp

er arm

Head

Neck

Tru

nk

Hip

Leg

Genitals

Abdominalorgans

Primarymotor cortex

Tongue

Toes

Jaw

Lips

Face

Eye

Brow

Neck

FingersH

andW

ristF

orearmE

lbo

wS

ho

uld

er

Tru

nk

Hip

Kn

ee

Thumb

Neurons are distributed in an orderly fashion

Fig. 49-16a

Primarymotor cortex

Tongue

Toes

Jaw

Lips

Face

Eye

Brow

Neck

FingersH

andW

ristForearmE

lbo

wS

ho

uld

er

Tru

nk

Hip

Kn

ee

Thumb

Fig. 49-16b

Primarysomatosensory cortex

Pharynx

TeethGumsJaw

Tongue

Lips

Face

Nose

Eye

Thumb

FingersH

andForearmE

lbo

wU

pp

er arm

He

ad

Ne

ck

Tru

nk

Hip

Le

g

Genitals

Abdominalorgans

1. 失去說話的能力稱做「失語症」。古希臘人發現，腦部損傷會導致失語症。 幾世紀以後， 1836 年 Marc Dax 描述了一組不能適當地講話的的病患。 Dax 報道所有這些患者他們的腦子的左邊都有損傷。 1861 年又過了四分之一世紀以後，保羅˙布洛卡（ Paul Broca ）描述了只能說一個字‘’ Tan‘’ 的一名患者

2. 1876 年 卡爾˙韋尼克（ Karl Wernicke ）發現對腦子的另一個區域的損傷也會造成語言問題。 「韋尼克氏區」（ Wernicke's area ）是在布洛卡區比較後方集下方的位置。 實際上， 韋尼克氏區是在顳葉後方的位置。 布洛卡區和韋尼克氏區由神經纖維束「 arcuate fasciculus 」連接稱。 arcuate fasciculus 損傷導致的病症叫做「傳導失語症」。

Generating words

Max

Speaking words

Hearing words

Seeing words

Min

Broca’s area: left frontal lobe comprehend speech but not the ability to speak

Wernicke’s area: understsnding language but unable to speak (left temporal lobe)

Reading w/o speaking

Generates verbs

language and speech

Lateralization of Cortical Function

• The corpus callosum transmits information between the two cerebral hemispheres

• The left hemisphere is more adept at language, math, logic, and processing of serial sequences

• The right hemisphere is stronger at pattern recognition, nonverbal thinking, and emotional processing

• The differences in hemisphere function are called lateralization

• Lateralization is linked to handedness

Emotions

• Emotions are generated and experienced by the limbic system and other parts of the brain including the sensory areas

• The limbic system is a ring of structures around the brainstem that includes the amygdala, hippocampus, and parts of the thalamus

• The amygdala is located in the temporal lobe and helps store an emotional experience as an emotional memory

Fig. 49-18

ThalamusHypothalamus

Prefrontalcortex

Olfactorybulb

Amygdala Hippocampus

Concept 49.4 Changes in synaptic connections underlie memory and learning

• Two processes dominate embryonic development of the nervous system– Neurons compete for growth-supporting factors in order to survive– Only half the synapses that form during embryo development survive into

adulthood`

• Neural plasticity describes the ability of the nervous system to be modified after birth

• Changes can strengthen or weaken signaling at a synapse

Fig. 49-19

(a) Synapses are strengthened or weakened in response to activity.

N2

(b) If two synapses are often active at the same time, the strength of the postsynaptic response may increase at both synapses.

N1

N2

N1

Memory and Learning

• Learning can occur when neurons make new connections or when the strength of existing neural connections changes

• Short-term memory is accessed via the hippocampus

• The hippocampus also plays a role in forming long-term memory, which is stored in the cerebral cortex

Long-Term Potentiation

• In the vertebrate brain, a form of learning called long-term potentiation (LTP) 長期增益現象 involves an increase in the strength of synaptic transmission

• LTP involves glutamate receptors

• If the presynaptic and postsynaptic neurons are stimulated at the same time, the set of receptors present on the postsynaptic membranes changes

Fig. 49-20

(c) Synapse exhibiting LTP

Mg2+

Na+

(a) Synapse prior to long-term potentiation (LTP)

(b) Establishing LTP

NMDA receptor(open)

Glutamate

StoredAMPAreceptor

NMDAreceptor(closed)

Ca2+

1

3

3

2

14

2

1. Depolarizes Mg2+ removed

2. Respond to glutamate an influx of Na+ and Ca2+

3. Ca2+AMPA glutamate receptors inserted into the postsynaptic membrane

Long-term potentiation in the brain

1. Glutamate release Na+ influx depolarization

2. Depolarization

3. Mg2+ removed

4. AMPA and NMPA receptor trigger postsynaptic potentials

Mg2+ blocked NMDA glutamate receptor

AMPA (α-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate)

AMPAAMPA (α-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate) is a compound that is a specific agonist for the AMPA receptor, where it mimics the effects of the neurotransmitter glutamate.[

NMDA (N-methyl-D-aspartic acid) is an amino acid derivative acting as a specific agonist at the NMDA receptor, and therefore mimics the action of the neurotransmitter glutamate on that receptor. In contrast to glutamate, NMDA binds to and regulates the above receptor only, but not other glutamate receptors

Concept 49.5: Nervous system disorders can be explained in molecular terms

• Disorders of the nervous system include schizophrenia, depression, Alzheimer’s disease, and Parkinson’s disease

• Genetic and environmental factors contribute to diseases of the nervous system

Schizophrenia

• About 1% of the world’s population suffers from schizophrenia

• Schizophrenia is characterized by hallucinations, delusions 錯覺 , blunted emotions, and other symptoms

• Available treatments focus on brain pathways that use dopamine as a neurotransmitter

Fig. 49-21

Genes shared with relatives ofperson with schizophrenia

12.5% (3rd-degree relative)

100%

50% (1st-degree relative)

25% (2nd-degree relative)

50

40

30

20

10

Ris

k o

f d

evel

op

ing

sch

izo

ph

ren

ia (

%)

Relationship to person with schizophrenia

Fra

tern

al

twin

Iden

tica

l tw

in

Ch

ild

Gra

nd

chi l

d

Fu

ll s

ibli

ng

Par

ent

Hal

f si

bli

ng

Nep

hew

/nie

ce

Un

cle/

aun

t

Fir

st c

ou

sin

Ind

ivid

ual

,g

ener

al p

op

ula

tio

n

0

Depression• Two broad forms of depressive illness are known: major

depressive disorder and bipolar disorder

• In major depressive disorder, patients have a persistent lack of interest or pleasure in most activities

• Bipolar disorder is characterized by manic (high-mood) and depressive (low-mood) phases

• Treatments for these types of depression include drugs such as Prozac and lithium

Drug Addiction and the Brain Reward System

• The brain’s reward system rewards motivation with pleasure

• Some drugs are addictive because they increase activity of the brain’s reward system

• These drugs include cocaine, amphetamine, heroin, alcohol, and tobacco

• Drug addiction is characterized by compulsive consumption and an inability to control intake

• Addictive drugs enhance the activity of the dopamine pathway

• Drug addiction leads to long-lasting changes in the reward circuitry that cause craving for the drug

Fig. 49-22

Nicotinestimulatesdopamine-releasingVTA neuron.

Cerebralneuron ofreward pathway

Opium and heroindecrease activityof inhibitoryneuron.

Cocaine andamphetaminesblock removalof dopamine.

Rewardsystemresponse

Ventral tegmental area

Near the base of the brain :VTA is a part of the midbrain. It consists of dopamine, GABA, and glutamate neurons

Reward system

• In neuroscience, the reward system is a collection of brain structures which attempts to regulate and control behavior by inducing pleasurable effects

• The mesolimbic pathway transmits dopamine from the ventral tegmental area (VTA) to the nucleus accumbens. The VTA is located in the midbrain, and the nucleus accumbens in the limbic system. The "meso-" prefix in the word "mesolimbic" refers to the midbrain, or "middle brain", since "meso" means "middle" in Greek.

• The mesocortical pathway transmits dopamine from the VTA to the frontal cortex. The "meso-" prefix in "mesocortical" refers to the VTA which is located in the midbrain, and "cortical" refers to the cortex.

---Malfunctions of the mesocortical pathway are associated with schizophrenia

It is known to be involved in modulating behavioral responses to stimuli that activate feelings of

reward (motivation) and reinforcement through the neurotransmitter dopamine.

Alzheimer’s Disease

• Alzheimer’s disease is a mental deterioration characterized by confusion, memory loss, and other symptoms

• Alzheimer’s disease is caused by the formation of neurofibrillary tangles and amyloid plaques in the brain

• A successful treatment in humans may hinge on early detection of amyloid plaques

• There is no cure for this disease though some drugs are effective at relieving symptoms

Fig. 49-23

Amyloid plaque 20 µmNeurofibrillary tangle

Parkinson’s Disease

• Parkinson’s disease is a motor disorder caused by death of dopamine-secreting neurons in the midbrain

• It is characterized by difficulty in initiating movements, muscle tremors, slowness of movement, and rigidity

• There is no cure, although drugs and various other approaches are used to manage symptoms

Fig. 49-UN5

Cerebrum

Thalamus

Hypothalamus

Pituitary gland

Forebrain

Cerebralcortex

Midbrain

Hindbrain

Pons

Medullaoblongata

Cerebellum

Spinalcord

Fig. 49-UN6

You should now be able to:

1. Describe the structures and functions of the following brain regions: medulla oblongata, pons, midbrain, cerebellum, thalamus, epithalamus, hypothalamus, and cerebrum

2. Describe the specific functions of the brain regions associated with language, speech, emotions, memory, and learning

3. Explain the possible role of long-term potentiation in memory storage and learning

4. Describe the structures and functions of the following brain regions: medulla oblongata, pons, midbrain, cerebellum, thalamus, epithalamus, hypothalamus, and cerebrum

• Describe the specific functions of the brain regions associated with language, speech, emotions, memory, and learning

• Explain the possible role of long-term potentiation in memory storage and learning

• Describe the symptoms and causes of schizophrenia, Alzheimer’s disease, and Parkinson’s disease

8. Explain how drug addiction affects the brain reward system