Download Nervous System - Northwest ISD Moodle

NERVOUS SYSTEM
March 3, 2016
STRUCTURES OF THE CEREBRUM
Cerebral Hemisphere – 2 large masses which are
essentially mirror images of each other connected
by a deep bridge of nerve fibers called the corpus
callosum; the surface has many convolutions
(ridges) separated by grooves (shallow groove is
called a sulcus and a deep groove is called a
fissure)
CEREBRUM
The lobes of the cerebral
hemisphere are named after
the skull bones they underlie:
 Frontal Lobe
 Parietal Lobe
 Temporal Lobe
 Occipital Lobe
STRUCTURES OF THE CEREBRUM
CEREBRAL CORTEX
thin layer of gray
matter that forms
the outermost
portion of the
cerebrum; contains
nearly 75% of all
the neuron cell
bodies in the
nervous system
MASS OF WHITE MATTER
lies just beneath the
cerebral cortex and
makes up the bulk
of the cerebrum;
bundles of
myelinated fibers
FUNCTIONS OF THE CEREBRUM
FUNCTIONAL REGIONS OF THE CEREBRAL
CORTEX
Primary Motor Areas – lie in the
frontal lobes; fibers cross over in the
brain stem from one side of the brain
to the other (right CH motor area
generally controls skeletal muscles on
the left side of the body and vise versa)
motor speech area
frontal eye field
FUNCTIONAL REGIONS OF THE CEREBRAL
CORTEX
Sensory Areas – located
in several lobes
a. cutaneous senses –
sensations of the skin
b. visual area
c. auditory area
d. taste area
e. smell area
FUNCTIONAL REGIONS OF THE CEREBRAL
CORTEX
Association Area –
neither primarily
sensory or motor;
analyzes and
interprets sensory
experiences and
oversees memory,
reasoning,
verbalizing,
judgment, and
emotion
FUNCTIONAL REGIONS OF THE CEREBRAL
CORTEX
General
Interpretive Area
– complex thought
processing
- also called
Wernicke’s area
HEMISPHERE DOMINANCE
Although both cerebral hemispheres participate in
basic functions, in most people, one side of the
cerebrum is the dominant hemisphere,
controlling other functions (handwriting,
throwing a ball)
HEMISPHERE DOMINANCE
In over 90% of the population,
the left hemisphere is
dominant for language-related
activities of speech, writing,
reading, and for complex
intellectual functions requiring
verbal, analytical, and
computational skills.
HEMISPHERE DOMINANCE
In addition to carrying on basic
functions, the non-dominant
hemisphere specializes in nonverbal
functions, such as motor tasks that
require orientation of body in space,
understanding, and interpreting
musical patterns, and nonverbal visual
experiences, as well as emotional and
intuitive thinking.
CEREBRAL HEMISPHERES
Left Brain and Right Brain
 Inner Surface

White Matter
 Mylenated


Outer Surface: Cerebral Cortex
Gray Matter
 Non-mylenated

CEREBRAL HEMISPHERES
Grooves are called sulcus (plural: sulci)
 Sulci divide the brain into 4 regions or lobes

Frontal
 Parietal
 Occipital
 Temporal

CEREBRAL HEMISPHERES
CEREBRAL HEMISPHERES
Fissures are uniformly positioned
 Divide the brain into Left and Right
Hemispheres
 Neural Communications to and from the right
side of the body are controlled by the left brain
 Neural Communications to and from the left side
of the body are controlled by the right brain

CEREBRAL HEMISPHERES
FRONTAL LOBE
Sectioned off from the rest of the brain by the
central sulcus
 Frontal lobe is involved in a wide variety of
functions:









Motor function
Problem Solving
Memory
Language
Initiation
Judgment
Impulse Control
Social and Sexual Behavior
FRONTAL LOBE
LEFT FRONTAL LOBE

Includes Broca’s Area
Controls tongue and lip movements required for
speech
 Damage in this area in stoke patients produces
difficulty with speaking

BROCA’S AREA
ASSOCIATION CORTEX
Believed to be responsible for intellect
 Located in the most anterior portion of the
frontal lobe

PRIMARY MOTOR CORTEX
Just behind the central sulcus
 Sends neural impulses to the skeletal muscles to
initiate and control the development of muscle
tension and movement


Small regions of the cortex control large/major
body segments


Examples: trunk, pelvis, thigh, arm
Large regions of the cortex control small body
segments
Examples: hands, lips, tongue
 Why is this the case?

PRIMARY MOTOR CORTEX
PARIETAL LOBES
Immediately behind/posterior to the frontal lobes
 Include the primary somatic sensory cortex
 Interprets Sensory impulses received from the
skin, internal organs, muscles, and joints
 The areas with more sensory receptors occupy
larger portions of the sensory cortex

PARIETAL LOBES
OCCIPITAL LOBES
Behind Parietal
 Responsible for vision

TEMPORAL LOBES
The most inferior (directionally speaking)
 Frontal and Parietal lobes are above them
 Involved in







Speech
Hearing
Vision
Memory
Emotion
The region responsible for speech is located at the
intersection of the occipital, temporal and
parietal lobes
TEMPORAL LOBES
TEMPORAL LOBES
CHECK YOUR UNDERSTANDING
1)
2)
3)
List the four major anatomic regions of the
brain.
What are the locations of the four lobes of the
brain?
What are the functions of each?
CEREBROSPINAL FLUID
Cerebrospinal Fluid is secreted by capillaries from
the pia mater.
1)It completely surrounds the brain and spinal
cord. These organs float in the fluid, which
supports and protects them.
2) It also provides a pathway to the blood for waste.
3) This waste function helps to regulate the body’s
pH.
CEREBROSPINAL FLUID OR CFS


The CFS normally produced and circulated
through and around the brain at a steady rate
If something obstructs this flow, the fluid can
accumulate
This puts dangerous pressure on the brain
 Example: brain tumors
 Hydrocephalus (water on the brain)
 High intra-cereberal pressure

CNS ANATOMY

Meninges are membranes that lie between the
bones and soft tissues of the cranial cavity and
vertebral canal. They protect the brain and
spinal cord
MENINGES

They consists of three layers:
1. Dura Mater – outermost layer
 2. Arachnoid Mater – located between the dura and
pia mater

a. Subarachnoid space – lies between the arachnoid and pia
mater and contains the clear watery cerebrospinal fluid
(CFS)
 Allows your brain to “float” in your skull


3. Pia Mater – very thin and contains nerves and
blood vessels that nourish underlying cells of the
brain and spinal cord; hugs the surface of these
organs following their irregular contours, passing
over high areas and dipping into depressions
BRAIN ANATOMY

Divided into specialized regions that may, or may
not, interact with each other to produce a given
action
BRAIN ANATOMY



Central Nervous System starts off as a neural
tube
The Caudal (lower) end of the tube stretches out,
forming the spinal cord
While the cranial end begins to expand, divide,
and enlarge into three primary brain vesicles



Prosencephalon (forebrain)
Mesencephalon (midbrain)
Rhombencephalon (hindbrain)
BRAIN ANATOMY

End up with the
Cerebellum
 Brain Stem
 Interbrain (Diencephalon)
 Cerebral Hemispheres

CEREBELLUM
large mass located
below the occipital
lobes and posterior
to the pons and
medulla oblongata;
two hemispheres
composed largely of
white matter
surrounded by a thin
layer of gray matter;
CEREBELLUM

Helps coordinate muscular activity
CEREBELLUM
communicates with other parts of the CNS by means of
three pairs of nerve tracts called cerebellar
peduncles:
a. inferior peduncle – brings sensory information
concerning the position of the limbs, joints, and other
body parts to the cerebellum
b. middle peduncle – transmits signals from the
cerebral cortex to the cerebellum concerning the desired
positions of the above mentioned parts; after integrating
and analyzing this information the cerebellum sends
correcting information via the superior peduncle
CEREBELLUM
CEREBELLUM
Thus, the cerebellum is a reflex center for
integrating sensory information concerning
position of the body parts and for coordinating
complex skeletal muscle movements.
Damage is likely to result in tremors, inaccurate
movements of voluntary muscles, loss of muscle
tone, a reeling walk, and loss of equilibrium.
BRAIN STEM
a bundle of nerve
tissue that
connects the
cerebrum to the
spinal cord
BRAIN ANATOMY

Brain Stem
Approximately the size of a thumb
 Includes 3 parts

Midbrain
 Pons
 Medulla Oblongata

MIDBRAIN

Relay Station for sensory and motor impulses






Vision
Hearing
Motor Activity
Sleep and Wake Cycles
Arousal (Alertness)
Temperature Regulation
MIDBRAIN
joins lower parts of
the brain stem and
spinal cord with
higher parts of the
brain; contains
centers for certain
visual and
auditory reflexes
PONS

Located immediately below the midbrain

Plays a role in regulating breathing
PONS
rounded bulges on the
underside of the brain
stem; transmits impulses
to and from the
cerebrum and medulla
oblongata and the
cerebrum and
cerebellum; relays
messages from the PNS
to high brain centers and
functions with the
medulla oblongata in
regulating the rate and
depth of breathing
MEDULLA OBLONGATA

Reflex Control
Coughing
 Sneezing
 Vomiting


Regulatory Control
Heart rate
 Breathing
 Blood Pressure

MEDULLA OBLONGATA
a.
All descending and ascending nerve fibers pass
through the medulla oblongata.
It is composed of gray matter surrounded by white
matter and contains centers for controlling
visceral activities:
cardiac center – alters heart rate
b. vasomotor center – certain cells initiate impulses which
stimulate blood vessels to contract (vasoconstriction)
elevating blood pressure; other cells have the opposite
affect – dilating blood vessels (vasodilation) dropping
blood pressure
c. respiratory center – acts with centers in the pons to
regulate the rate, rhythm, and depth of breathing
MEDULLA OBLONGATA
RETICULAR FORMATION
(RETICULAR ACTIVATING SYSTEM)
The reticular formation extends from the upper
portion of the spinal cord into the
diencephalon and is connected to all
ascending and descending fiber tracts.
When sensory impulses are received it
activates the cerebral cortex into
wakefulness.
Without this arousal, the cortex remains
unaware of stimulation and cannot
interpret information or carry out thought
processes.
Decreased activity results in sleep.
Injury to it causes a person to be unconscious
and cannot be aroused, even with strong
stimulation (comatose state).
DIENCEPHALON
The diencephalon is located between the cerebral
hemispheres and above the midbrain.
It is largely composed of gray matter
INTERBRAIN (DIENCEPHALON)
Deep inside the brain
 Enclosed by the Cerebral Hemispheres
 Includes

Thalamus
 Hypothalamus
 Epithalamus

THALAMUS
Relay Station for communicating both sensory
and motor information
 Regulatory Control


States of arousal
Sleep
 Wakefulness
 High-Alert Consciousness

DIENCEPHALON
Thalamus – relay
station for sensory
impulses (except
smell); produces a
general awareness
of certain
sensations, such as
pain, touch, and
temperature
DIENCEPHALON
Hypothalamus – below thalamus; maintains homeostasis by regulating a
variety of visceral activities and by linking the nervous and endocrine
systems; regulates:







heart rate and arterial blood pressure
body temperature
water and electrolyte balance
control of hunger and body weight
control of movements and glandular secretions of
stomach and intestines
production of neurosecretory substances that
stimulate the pituitary gland to secrete hormones
sleep and wakefulness
HYPOTHALAMUS
DIENCEPHALON

Epithalamus: act as a connection between the
limbic system to other parts of the brain. Some
functions of its components include the secretion of
melatonin by the pineal gland (involved in circadian
rhythms) and regulation of motor pathways and
emotions.
DIENCEPHALON
Limbic System – controls emotional experiences and
expression; can modify the way a person acts by
producing such feelings as fear, anger, pleasure,
and sorrow; recognizes upsets in a person’s
physical and psychological condition that might
threaten life; guides a person into behavior that is
likely to increase the chance of survival
LIMBIC SYSTEM
OTHER STRUCTURES OF THE
DIENCEPHALON
1. Optic Tract Optic Chiasma - vision
2. infundibulum – structures in which the
pituitary gland is attached
3. pituitary gland – master gland
4. olfactory bulbs - smell
5. pineal gland – structure that secretes
melatonin, which affects the sleep cycle; the
darker it is the more melatonin is released,
the lighter it is the less melatonin is released
OPTIC TRACTS AND OPTIC
CHIASMA
INFUNDIBULUM
– STRUCTURES IN WHICH
THE PITUITARY GLAND IS ATTACHED
PITUITARY GLAND
OLFACTORY BULBS
PINEAL GLAND
structure that secretes
melatonin, which
affects the sleep
cycle; the darker it is
the more melatonin
is released, the
lighter it is the less
melatonin is
released
EPITHALAMUS
Includes the pineal gland
 Regulates the sleep-cycle hormones that it
secretes

Cortisol
 Melatonin

CHECK YOUR UNDERSTANDING
1)
2)
3)
Name the three structures that make up the
diencephalon and state their functions.
Name the three structures that make up the
brain stem and state the function of each.
Where is the cerebellum located and what is it’s
function?
PERIPHERAL NERVOUS SYSTEM
SOMATIC NERVOUS SYSTEM
The somatic nervous system consists of the cranial
and spinal nerve fibers that connect the CNS
to the skin and skeletal muscles.
It oversees conscious activities (voluntary).
AUTONOMIC NERVOUS SYSTEM
The autonomic nervous system consists of sensory
neurons and motor neurons that run between
the central nervous system (especially the
hypothalamus and medulla oblongata) and
various internal organs such as the:
 heart
 lungs
 viscera
 glands
(both exocrine and endocrine)
AUTONOMIC NERVOUS SYSTEM
The autonomic nervous system is the portion of the
PNS that functions independently
(autonomously/involuntary) and continuously
without conscious effort.
1. It controls visceral functions by regulating the
actions of smooth muscles, cardiac muscles, and
glands.
2. It regulates heart rate, blood pressure, breathing
rate, body temperature, and other visceral activities
that maintain homeostasis.
3. Portions respond to emotional stress and prepare the
body to meet demands of strenuous physical activity
AUTONOMIC NERVOUS SYSTEM
General Characteristics:
1.
regulated by reflexes
2.
typically, peripheral nerve fibers lead
to ganglia outside the CNS where they
are integrated and relayed back to
viscera (muscles and glands) that
respond by contracting, releasing
secretions, or being inhibited
3.
provides the autonomic system with a
degree of independence from the
brain and spinal cord
4.
includes two divisions:
AUTONOMIC NERVOUS SYSTEM
The autonomic nervous system includes two
divisions:
Sympathetic division – prepares the body
for energy-expending, stressful, or
emergency situations (fight-or-flight)
Parasympathetic division – most active
during ordinary, restful conditions;
counterbalances the effects of the
sympathetic division and restores the
body to a resting state following a
stressful experience
SYMPATHETIC DIVISION
The preganglionic motor
neurons of the
sympathetic system
(shown in black) arise in
the spinal cord. They pass
into sympathetic ganglia
which are organized into
two chains that run
parallel to and on either
side of the spinal cord.
SYMPATHETIC DIVISION
The preganglionic neuron may do one of three
things in the sympathetic ganglion:
1.
synapse with postganglionic neurons (shown
in white) which then reenter the spinal nerve
and ultimately pass out to the sweat glands
and the walls of blood vessels near the surface
of the body.
2.
pass up or down the sympathetic chain and
finally synapse with postganglionic neurons in
a higher or lower ganglion

.
SYMPATHETIC DIVISION
3. leave the ganglion by way of a cord leading to
special ganglia (e.g. the solar plexus) in the
viscera. Here it may synapse with postganglionic
sympathetic neurons running to the smooth
muscular walls of the viscera. However, some of
these preganglionic neurons pass right on through
this second ganglion and into the adrenal
medulla (endocrine gland on top of the
kidney). Here they synapse with the highlymodified postganglionic cells that make up the
secretory portion of the adrenal medulla.
SYMPATHETIC DIVISION
 The
neurotransmitter of the preganglionic
sympathetic neurons is acetylcholine (ACh). It
stimulates action potentials in the postganglionic
neurons.
 The neurotransmitter released by the
postganglionic neurons is noradrenaline (also
called norepinephrine).
 The action of noradrenaline on a particular gland
or muscle is excitatory in some cases, inhibitory
in others. (At excitatory terminals, ATP may be
released along with noradrenaline.)
SYMPATHETIC DIVISION
The release of noradrenaline
 stimulates
heartbeat
 raises blood pressure
 dilates the pupils
 dilates the trachea and bronchi
 stimulates glycogenolysis — the conversion of
liver glycogen into glucose
 shunts blood away from the skin and viscera to
the skeletal muscles, brain, and heart
 inhibits peristalsis in the gastrointestinal (GI)
tract
 inhibits contraction of the bladder and rectum
SYMPATHETIC DIVISION
 Stimulation
of the sympathetic branch of the
autonomic nervous system prepares the body for
emergencies: for "fight or flight" (and, perhaps,
enhances the memory of the event that triggered
the response).
 Activation of the sympathetic system is quite
general because a single preganglionic neuron
usually synapses with many postganglionic
neurons; the release of adrenaline from the
adrenal medulla into the blood ensures that all
the cells of the body will be exposed to
sympathetic stimulation even if no
postganglionic neurons reach them directly.
PARASYMPATHETIC NERVOUS SYSTEM
The main nerves of the parasympathetic system
are the tenth cranial nerves, the vagus nerves.
They originate in the medulla oblongata. Other
preganglionic parasympathetic neurons also
extend from the brain as well as from the lower
tip of the spinal cord.
PARASYMPATHETIC NERVOUS SYSTEM
Each preganglionic parasympathetic neuron
synapses with just a few postganglionic
neurons, which are located near — or in —
the effector organ, a muscle or gland.
Acetylcholine (ACh) is the neurotransmitter
at all the pre- and many of the postganglionic
neurons of the parasympathetic system.
However, some of the postganglionic neurons
release nitric oxide (NO) as their
neurotransmitter.
PARASYMPATHETIC NERVOUS SYSTEM
Parasympathetic stimulation causes:
 slowing down of the heartbeat lowering of blood
pressure
 constriction of the pupils
 increased blood flow to the skin and viscera
 peristalsis of the GI tract
PARASYMPATHETIC NERVOUS SYSTEM
The parasympathetic system returns the body
functions to normal after they have been altered
by sympathetic stimulation.
In times of danger, the sympathetic system
prepares the body for violent activity. The
parasympathetic system reverses these changes
when the danger is over.
PARASYMPATHETIC NERVOUS SYSTEM
The vagus nerves also help keep inflammation
under control. Inflammation stimulates nearby
sensory neurons of the vagus. When these nerve
impulses reach the medulla oblongata, they are
relayed back along motor fibers to the inflamed
area. The acetylcholine from the motor neurons
suppresses the release of inflammatory cytokines,
e.g., tumor necrosis factor (TNF), from
macrophages in the inflamed tissue.
PARASYMPATHETIC NERVOUS SYSTEM
Although the autonomic nervous system is
considered to be involuntary, this is not
entirely true.
A certain amount of conscious control can be
exerted over it as has long been demonstrated by
practitioners of Yoga and Zen Buddhism. During
their periods of meditation, these people are
clearly able to alter a number of autonomic
functions including heart rate and the rate of
oxygen consumption. These changes are not
simply a reflection of decreased physical activity
because they exceed the amount of change
occurring during sleep or hypnosis.
AUTONOMIC NERVOUS SYSTEM