Transcript The Mammalian Brain

The Mammalian
Brain
9.3 The Central Nervous
System
p. 427 - 434
The Central Nervous System
• Consists of the brain and the spinal cord.
These organs are protected by:
•
1) skull and vertebrae
•
2) cerebrospinal fluid cushions the
brain and spinal cord
•
3) meninges are protective membranes
that surround the CNS
The Spinal Cord
• Contains interneurons that link the sensory and
motor pathways. These neurons carry
information to and from the brain. The spinal
cord contains 31 segments, each of which has a
pair of spinal nerves.
• The spinal cord contains white matter (bundles
of myelinated axons of sensory and motor
neurons), and grey matter (unmyelinated
interneurons and the dendrites of motor
neurons).
• Cerebrospinal fluid = surrounds
CNS (brain and spinal cord); acts as
a sock absorber and transport
medium (nutrients, chemicals,
removal of wastes, etc) is a
connection between CNS and
endocrine system
The Brain
• The human brain contains three distinct
areas: the forebrain, the midbrain, and the
hindbrain.
– is protected by the skull and meninges (a
protective three layer thick membrane that
surrounds the brain and spinal cord)
– meninges controls which chemicals can
ultimately reach the brain
• The meninges
(membrane) covers
the surface of the
cerebrum
• The most common
symptoms of
meningitis are
headache and neck
stiffness associated
with fever
• Meningitis is
diagnosed using a
technique called
lumbar puncture
• The meninges is composed of 3 membranes;
• the dura mater, the tough outer membrane that
adheres to the skull
• The arachnoid, the weblike middle layer that
reabsorbs cerebrospinal fluid;
• And the pia mater, the innermost layer that contains
many blood vessels and closely covers the brain and
spinal cord
Which region is responsible for vision?
Which is responsible for hearing?
Sections of the Brain
Forebrain:
– reason, intellect, memory, language, and personality
– information on right side does not = info on left
– generally on right (visual patterns or spatial
awareness)
– generally on left (verbal skills)
– hemispheres are joined by a bundle of nerves called
corpus collosum = allows communication between
hemispheres
Sections
Function
Olfactory lobes
(x2) process information about smell
Cerebrum
2 hemisphere; largest and most developed
coordinates sensory info & motor actions
largest and most developed
divided into four (4) lobes (see below)
Cerebral Cortex
surface of cerebrum
made of grey matter
highly folded (deep folds = fissures)
Why is the frontal lobe called frontal?
What forms the largest
part of the brain?
• cerebrum is
composed of
2
hemispheres
Why are we smarter than fish?
• We share a common ancestor
• However, our forebrains are much larger
(cerebrum: speech, reasoning, memory, and
personality)
“an elephant
never forgets”
• The cerebrum (area
of memory) is well
developed in the
elephant
• The elephants
cerebrum is larger
than humans
• The increased
surface area allows
more nerve cells,
which in turn allows
for more learning
and a greater range
of behaviours.
• The grey matter of
the human cortex is
less than 5 mm thick,
but in mass makes
up more than 80% of
the brain.
• The central fissure extends from the top of each
cerebral hemisphere to the lateral fissure
Midbrain:
• located directly below cerebral cortex
• relay center for eye and ear reflexes
Sections
Function
Thalamus
 integrative center connecting many different
parts of the brain together
Hypothalamus
 master control center of automatic nervous
system (ANS)
 integrates the ANS and endocrine system
Hippocampus
 short term memory
Basal Ganglia
 many parts; responsible for crude motor
movements
 injury leads to rigidity, Parkinson’s and
Huntington’s disease
 mediates emotional feelings
 mediates between forebrain & hindbrain
The Hindbrain:
Sections
http://outreach.mc
b.harvard.edu/ani
mations/brainanat
omy.swf
Function
Medulla Oblongata




Pons “bridges”
 acts as relay station by sending nerve
messages between the cerebellum and
medulla
Cerebellum
 controls limb movements, balance and muscle
tone
 e.g. walking, hand-eye coordination, etc)
joins spinal cord to cerebellum
controls involuntary muscle action
coordinating centre for the ANS
e.g breathing, heart rate, blood vessel activity,
swallowing, vomiting, digestion…)
• Cerebellum
• What does
convoluted
mean?
• Damage to the
cerebellum can
lead to: loss of
coordination of
motor
movement
• brain stem
• basic
attention,
arousal, and
consciousnes
s
• The frontal lobe:
• higher intellect, foresight
and judgment, primary
motor area and motor
area for speech
• In 1890, psychiatrist
Gottlieb Burckhardt
removed pieces of the
frontal lobes of six
patients in a psychiatric
hospital in Switzerland.
• The parietal lobe:
• touch,
temperature, and
taste, and
association areas
for emotions,
reading, and
interpreting speech
• Temporal:
• smell, hearing
and auditory
association
areas
Occipital:
vision and
visual
association
areas
• The corpus
callosum
• contains nerve
fibers that
connect the
right and left
sides of the
brain
• The corpus callosum is white because it
consists of myelinated nerve fibres.
Sheep
• The medulla oblongata
• controls heart and breathing rates and
vasomotion (the dilation and constriction of
blood vessels) to ensure blood is distributed
more to active tissues than inactive ones.
sheep
• The pons is an important relay center for
sensory and motor nerve fibers connecting the
medulla oblongata and the cerebellum
• The pons also stimulates exhalation during
prolonged inhalation of breath-holding.
• The hypothalamus is an important center for the
homeostatic regulation of several activities.
• It produces the hormones oxytocin and antidiuretic
hormone secreted by the posterior pituitary gland.
• Other functions include the regulation of body
temperature, water retention, appetitie, digestive
secretions, sexual activity, and emotions such as fear
and rage.
PRACTICE!!!
1. List the four regions of the cerebral
cortex and state the function of each.
a) Frontal lobe: motor areas control movement of
voluntary muscles (e.g., walking and speech).
Association areas are linked to intellectual activities
and personality.
b) Temporal lobe: Sensory areas are associated with vision
and hearing. Association areas are linked to memory and
interpretation of sensory information.
c) Parietal lobe: Sensory areas are associated with
touch and temperature awareness. Association
areas have been linked to emotions and interpreting
speech.
d) Occipital lobe: Sensory areas are associated with vision.
Association areas interpret visual information.
3. Name the different parts of the brain on page 434 and give
functions.
• T- cerebrum: stores sensory information and
initiates voluntary motor activities
• S-pons: acts as a relay station by sending
nerve messages between the cerebellum and
the medulla
• R- medulla oblongata: site of autonomic nerve
control
• V- cerebellum: coordinates muscle movent
4. A physician makes an incision completely through the
corpus callosum. How might this affect the patient?
• The right and left sides of the brain will not be
able to communicate.
• “the left hand does not know what the right
hand is doing”
• Has been considered as a treatment for severe
cases of epilepsy
Phineas P. Gage (July 9?, 1823–May 21, 1860) was a
railroad construction foreman now remembered for his
incredible survival of an accident which drove a large
iron rod through his head, destroying one or both of his
frontal lobes.
Magnetic resonance imaging
(MRI), or Nuclear magnetic
resonance imaging (NMRI)
Brain Anatomy and
Function