独中高中生物Chapter 13 Part 2

13.2 Composition
and structure of
nervous system

Objectives
• To comprehend the structure and functions of brain.
• To comprehend the structure and functions of spinal cord.
• To comprehend the composition and functions of peripheral nervous
system.
• To understand the functions of autonomic nervous system.
• To comprehend the formation and meaning of reflex action.
• To understand the differences of non-conditioned and conditioned
reflexes.

Importance of nervous system
• Nervous system is an important
human regulatory system.
• It regulates the endocrine system内
分泌系统 and sensory organs感觉器官.
• The purpose is to maintain
homeostasis.

central nervous system
• The central nervous system is
the complex of nerve tissues
that controls the activities of
the body.
• In vertebrates, the CNS
comprises of
• the brain (in the skull)
• the spinal cord脊髓 (in the
vertebral column)

13.2.1.1 The
structure and
function of brain

沟回
裂
间脑
丘脑下丘脑
中脑
脑桥
延髓脑干击碎
小脑
大脑
Brain stem
• Cerebrum大脑
• Cerebellum小脑
• Diencephalon间脑
• Thalamus丘脑
• Hypothalamus下丘脑
• Brain stem脑干
• Midbrain中脑
• Pons脑桥
• Medulla延髓

独中高中生物Chapter 13 Part 2

Cerebrum
• Latin cerebrum ‘brain’
• The principal and largest part of the
brain in vertebrates.
• Human cerebrum is divided into left and
right cerebral hemispheres半球 by a
fissure裂.
• The two cerebral hemispheres are joined
by a bundle of nerve fibers (axons) called
corpus callosum胼胝体.
• Latin corpus ‘body’ + callosum ‘tough’
• enables communication between the
hemispheres
cerebral hemispheres corpus callosum

Surface of the cerebrum
• Outermost layer of cerebral hemisphere is
known as cerebral cortex大脑皮层.
• Cerebral cortex is folded into
• sulcus沟 (pl. sulci) – depression
• Latin sulcus "furrow“
• gyrus回 (pl. gyri) – ridge
• Greek guros ‘a ring’
• The sulci and gyri create a larger surface
area to house the soma of the neurons as
the volume of the skull is limited.

Grey matter灰质
• The cerebral cortex皮层 houses the
grey matter.
• The grey matter contains
numerous cell body of
unmyelinated neurons.
• The grey matter serves to process
information in the brain.
• It appeared to be in a light grey
colour with yellowish or pinkish
hues
The grey matter and white matter are also present in the
brainstem, cerebellum, and the spinal cord.

White matter白质
• The subcortical cerebral medulla髓层
contains white matter.
• The white matter contains relatively few
cell bodies and is composed of
myelinated axon tracts.
• The white matter relay and coordinating
communication with other neurons.
• It appeared whitish.

Regions of the cerebral cortex
Cerebral cortex is divided into
• frontal lobe额叶
• parietal lobe顶叶
• occipital lobe枕叶
• temporal lobe颞叶

Frontal lobe
• The frontal lobe, located at the front
of the brain, is separated from the
parietal lobe the central sulcus, and
from the temporal lobe by the lateral
fissure deep sulcus.
• Frontal cortex is related to
• conscience良心,
• cognition,
• emotion and emotional-based memory,
and
• voluntary motor movement.

Regions of the frontal lobe
• Pre-central sulcus region
contains the primary motor
cortex, which controls
voluntary movements of
specific body parts.
• The motor speech area is a
region in the frontal lobe of the
dominant hemisphere, usually
the left, that linked to speech
production movement.
lateral sulcus

Parietal lobe
• from Latin paries, pariet- ‘wall’
• The parietal lobe is positioned
behind the frontal lobe and
central sulcus and above the
occipital lobe.
• The parietal lobe integrates and
processes sensory information
received by our stimuli
receptors.

Somatotopic
organisation of
the
sensorimotor
cortex.
• Movement and sensation of each
part of our body are reflected at
the motor area and sensory area of
cerebral cortex.
• Somatotopic is the point-for-point
correspondence of an area of the
body to a specific point on the
central nervous system.

Association
areas
• The association
area of the
cerebral cortex
translates, analysis
and stores input
information.
• They assist in the
activities of motor
area and sensory
area.
Central sulcus

Occipital lobe
• Latin ob ‘behind’ + caput ‘the
head’.
• The occipital lobe is the
visual processing center.

Temporal lobe
• The temporal lobe is located
beneath the lateral fissure on
both cerebral hemispheres of the
mammalian brain.
• The temporal lobe is involved in
processing sensory input with the
auditory (hearing), olfactory
(smell) and gustatory (taste)
centres.
• The temporal lobe is also essential
for long term memory retention,
language comprehension, and
emotion association.

Effects of damage to the motor cortex
• If the motor cortex or
the spiral cord is
damaged, the voluntary
movement of the body
will be lost completely,
leading to local or
systemic paralysis瘫痪.

Effects of damage to both the motor cortex
and the sensory cortex
• Damage to the motor cortex
and sensory cortex may lead a
persistent vegetative state持续
性植物状态（植物人）, i.e. to a
wakeful 清醒（眼睛睁开）
unconscious缺乏意识 state that
lasts longer than a few weeks.
• PVS patients’ have functioning
brain stem, hence reflective
movements such as breathing
and blood pressure is
maintained, and can open
their eyelids occasionally and
demonstrate sleep-wake
cycles.
• PVS patients completely lack
cognitive function.

Lateralised nature of brain function
• The lateralisation of brain function
is the tendency for some neural
functions or cognitive processes to
be more dominant in one
hemisphere than the other, e.g. the
motor speech area is generally
developed on the left hemisphere.
• The left hemisphere controls
the right side of the body.
• While the right hemisphere
coordinates the left side of the
body,

Cerebellum
• Latin cerebellum "little brain”
• The human cerebellum is a separate
structure attached to the bottom of
the brain, tucked underneath the
cerebral hemispheres.
• Structurally similar to cerebrum with
sulcus and gyrus to increase the
surface area for grey tissue.
• The human cerebellum does not
initiate movement, but contributes to
coordination in fine movement of
skeletal muscle, equilibrium, posture,
and motor learning in humans.

Structure of diencephalon
Diencephalon includes
• Thalamus
• Hypothalamus
• Third ventricle (surrounded by thalamus)
• Pineal body
• Posterior pituitary gland
Pineal body
13.3.1.6 ventricle

Thalamus丘脑
• from Greek thalamos "inner chamber,
bedroom"
• The thalamus serves as the great
sensory receiving (except olfaction) and
coordination area and relays sensory
information to the cerebral cortex.

Hypothalamus下丘脑
• Hypothalamus is the lowermost
structure of the diencephalon.
• Hypothalamus maintains
homeostasis by regulating the
endocrine secretion, autonomic
function and emotions and drives.
• Sleep
• Hydration and osmoregulation
• Ingestion
• Body temperature

Pineal body松果体
• The pineal gland (aka pineal body) is a
small endocrine gland in the vertebrate
brain that produces melatonin褪黑素,
which modulates sleep patterns.
• Melatonin production is stimulated by
darkness and inhibited by light.
• Mammals received light stimuli from
the eyes as the pineal body is covered
by the skull.
• In some animals, the pineal body is
directly connected to a parietal eye顶眼.

Posterior pituitary gland脑垂体后叶
• The posterior
pituitary gland is
located at the base of
the diencephalon.
• The posterior pituitary
gland stores and
releases hormones
(oxytocin 催产素 and
antidiuretic hormone)
directly into the blood.

Summary
Diencephalon includes
• Thalamus – relay information for cerebral
cortex
• Hypothalamus – maintain homeostasis and
secretes hormone
• Third ventricle
• Pineal body – secretes melatonin
• Posterior pituitary gland – stores and releases
oxytocin and ADH

Brainstem脑干
• The brainstem (or brain stem) is
the posterior part of the brain,
adjoining and structurally
continuous with the spinal cord.
• The brain stem includes
• Midbrain中脑,
• Pons脑桥, and
• Medulla oblongata延髓.
• The fourth ventricle is located
behind the pons and the
medulla.

Structure of the cerebellum and the
brainstem

Function of the brain stem
• Controls the flow of
messages between the
brain and the rest of the
body
• Controls basic body
functions such as
breathing, swallowing,
heart rate, blood
pressure, consciousness,
and whether one is awake
or sleepy.

Midbrain
• The midbrain is located
between the diencephalon
and the pons.
• The midbrain is associated
with the reflex center of
visual and hearing.
• It is also associated with
motor control, sleep/wake,
arousal (alertness), and
temperature regulation.

Pons
• pl. pontes, from Latin pons ‘bridge’, (in full)
‘bridge of Varolius’, named after C. Varoli
(1543–75), Italian anatomist.
• Pons is located in between midbrain and
medulla oblongata.
• The pons serves as a message station.
• It helps relay messages from the cortex
and the cerebellum.
• Most of the ascending tract from spinal
cord or descending tract from cerebrum
must pass through here to carry out
exchange.

Ascending tracts and descending tracts
• The ascending tracts are the
neural pathways by which sensory
information from the peripheral
nerves is transmitted to the
cerebral cortex.
• The descending tracts are
the pathways by which motor
signals are sent from the brain to
lower motor neurones.
ascending tract descending tract

Medulla oblongata
• Latin medulla ‘pith or marrow’ +
oblongata “elongated”
• Medulla oblongata connect to
pons and the spinal cord.
• It is the important control center
for autonomic (involuntary)
functions, for examples, breathing,
circulation, swallowing, vomiting,
sneezing, secretion of digestive
juice etc.

Lost of brain stem function
• Lost of the functions of the brain
stem will lead to lose of cellular
function quickly and organismal
death.
• Brain death is the complete loss
of brain function (including
involuntary activity controlled by
the brain stem necessary to
sustain life) and only life support
equipment would keep the
heartbeat and ventilation呼吸
going.

13.3.1.6
Ventricles and
cerebrospinal
fluid

The ventricular脑室system
• from Latin ventriculus, diminutive
of venter ‘belly’.
• The ventricular system is a set of four
interconnected cavities in the brain
• lateral ventricles (2) in the cerebrum
• the third ventricle is in the diencephalon
between the right and left thalamus;
• the fourth ventricle is located at the back
of the pons and upper half of the medulla
oblongata of the hindbrain.
• The third and fourth ventricles are
joined together by the cerebral
aqueduct中脑水管.

Functions of the ventricles
• The ventricles are concerned with the
production and circulation of cerebrospinal
fluid (CSF)脑脊液.
• Cerebrospinal fluid is secreted by choroids
plexus found on the upper part of third and
fourth ventricles.
• A plexus (pl. plexuses) (Latin "braid") is a
branching network of vessels or nerves.

Functions of the cerebrospinal fluid
• The CSF maintain the internal pressure within
the skull.
• The CSF is necessary for chemical stability, and
the provision of nutrients for brain.
• The CSF helps to protect the brain from jolts
and knocks to the head.
• The CSF also provides buoyancy and support to
the brain against gravity.
• This allows the brain to grow in size and weight
without resting on the floor of the cranium, which
would destroy nervous tissue.

Objectives
• To comprehend the structure and functions of spinal cord.

Spinal cord脊髓
• The spinal cord is a long, thin, tubular
bundle of nervous tissue and support
cells located in the vertebral column椎管.
• Spinal cord extends from the medulla
oblongata in the brainstem to the first
lumbar vertebral第一腰椎.
• The spinal cord is essential in the
communication of the brain with the
sensory organs and the effectors.
• The spinal cord also involves in basic
reflex activities.

Structure of spinal cord
• The spinal cord is made up
of grey and white matter.

Dorsal vs ventral
Dorsal
• from Latin dorsum ‘back’.
Ventral
• from Latin venter, ventr-
‘belly’.

Grey matter
• Grey matter is the site of neural cell
bodies to aggregate.
• Grey matter travels down the spinal
cord distributed in three grey columns
that are presented in an "H" shape.
• Ventral horn前角
• Dorsal horn侧角
• Lateral horn后角
• Lateral horns are found in the
abdomen胸腰 and sacrum骶 region.
Back / posterior
Front / superior

Functions of the grey matter
• Ventral horn connects to the
ventral root腹根 and contains motor
neurons.
• Dorsal horn connects to the
dorsal root背根 and synapses with
to the sensory neurons.
• The lateral horn is primarily
involved with activity in the
sympathetic交感神经 division of the
autonomic motor system自主神经.

White matter
• The spinal cord white
matter contains ascending
(sensory) and descending (motor)
tracts.
• The white matters contain
myelinated axons that connect the
brain, the sensory organs and the
effectors.

Reflex arc反射弧
• A reflex arc is a neural pathway that
controls a reflex, where spinal cord
received sensory information from
the receptor and generate response
for the effector organ(s).
• In a reflex arc, an action potential
never travels to the brain for
processing and so results in a much
quicker reaction.
• Reflex arc is made up of receptor,
sensory neuron, motor neuron and
effector

Process of reflex arc
1. A stimulus (A) is
encountered
2. The signal from that
stimulus will travel up the
sensory neuron (B, in
green) to the spinal
column (C).
3. The signal will likely pass
through a short
interneuron (D, in purple).

Process of reflex arc (cont.)
4. Response is generated
and the signal travels
down a motor neuron (E,
in blue) to the origin of
the signal.
5. Then, a contraction of the
muscles (F, in red) is
triggered, moving the
bone (G).

Two types of reflection
• somatic reflex躯体反应
• autonomic reflex自主反应
autonomic reflex

somatic reflex
• Also known as spinal reflex髓反射
• affecting skeletal muscles
• possible to overwrite with the
cerebrum as the sensory neuron
and the motor neuron are joined
to the cerebrum with the
ascending and descending tracts
• e.g. knee-jerk, heat avoidance,
defense reflex, grasping reflex,
hand retraction

autonomic reflex
• affecting inner organs (glands
and smooth muscles)
• generally not requires an
interneuron
• the autonomic nerve is
connected to the ventral root
of spinal nerves
• e.g. peristalsis, sweating, and
pupil constriction, blinking
and tearing in bright light

Summary
• The spinal cord is essential in the communication of the brain with
the sensory organs and the effectors.
• The spinal cord is made up of grey matter (ventral horn, dorsal horn,
lateral horn) and white matter.
• The spinal cord also involves in basic reflex activities.
• The autonomic reflex affects inner organs (glands and smooth
muscles) and generally does not require an interneuron.
• The somatic reflex affects skeletal muscles.

独中高中生物Chapter 13 Part 2

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