14 - Central
Nervous
System
The Brain
Taft College Human Physiology
Development of the Brain
• The brain begins as a simple
tube, a neural tube. The tube
or chamber (ventricle) is
filled with cerebrospinal fluid.
The cerebrospinal fluid
serves to cushion the brain
and spinal cord.
Nervous Tissue
Chamber (ventricle)
filled with fluid
called cerebral
spinal fluid.
CSF serves to
cushion brain.
Development of the Brain
• At 3-4 Weeks - we see further development of the brain and can see
the major divisions of the forebrain, midbrain, and hindbrain become
apparent.
• By 5 weeks • 1. Forebrain becomes the telencephalon and diencephalon.
• a. The telencephalon will become the cerebrum = (Cerebral Hemispheres)
• b. The diencephalon will become the thalamus, and hypothalamus.
• 2. Midbrain becomes the mesencephalon = Midbrain
• 3. Hindbrain becomes the metencephalon and myelencephalon.
• a. The metencephalon becomes the pons, and cerebellum.
• b. The myelencephalon becomes the medulla oblongata.
Oblongata
Development of the Brain
• With greater development, we begin to see extensive
convolutions of the cerebrum above, and the cerebellum
below.
Component Structures of the
Brain
• Telencephalon - Cerebrum –
• Function: the cerebrum perceives information,
directs motor responses, is the center of
intellect, memory, language, and consciousness.
The cerebrum is
subdivided by
convolutions.
In terms of the
convolutions,
Grooves or depressions
are called a sulcus or
fissure.
Rounded or elevated
portions of the
convolutions are called a
gyrus .
Component Structures of the Brain
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Cerebrum –
It is important to note that the convolutions are not a random pattern.
The longitudinal fissure divides the cerebrum into right and left halves called
cerebral hemispheres.
Within each of the hemispheres, the fissures divide the cerebrum further into
lobes.
The lobes of the cerebrum are located on its outer surface known as the
cerebral cortex. (Cortex means bark)
The cerebral cortex is the gray matter of the cerebrum. It consists of
approximately 12 to 15 billion nonmyelinated neuron cell bodies.
Component Structures of the Brain
• Lobes of the Cerebral Cortex
• The lobes of the cerebral cortex are named for the bones
of the cranium that overlay them.
• Functions:
• 1. Frontal Lobe -- the frontal lobe is a primary motor area,
also known as the somatomotor area. It is responsible for
voluntary movement. It is also responsible for speech in
part.
• 2. Parietal Lobe -- the parietal lobe is a general sensory
area. Therefore it is completely afferent in its function.
• 3. Occipital Lobe -- the occipital lobe is primarily
responsible for vision. It is sometimes called the visual
cortex.
• 4. Temporal Lobe -- the temporal lobe is the auditory
area. It is of primary importance for hearing and some
speech. It is sometimes called the auditory cortex.
Component Structures of the Brain
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Frontal Lobe = Motor/Speech
Parietal Lobe = Sensory
Occipital Lobe = Vision
Temporal Lobe = Hearing and Speech
Sensory
Motor/Speech
Hearing
Vision
Speech
• As stated earlier, the fissures that can be seen on the lobes of the
cerebral cortex, are not a random pattern.
• The fissures serve to separate areas of the brain with different
functions.
• About 100 different functions have been isolated for different
convolutions of the brain.
• How? This was originally done by inserting electrodes into
different parts of the brain and monitoring the activity of the brain.
• New equipment, is less invasive. MRI computers can now monitor
the slight temperature changes that take place in the brain as blood
flows into areas that become active during different activities.
Functional
Areas of the
Brain
White Matter of the Cerebrum
• The white matter of the cerebrum is located beneath the cerebral
cortex. It consists largely of myelinated fibers bundled into large
tracts.
• 1. Commissural Fibers –Commissural fibers serve to connect the 2
cerebral hemispheres.
• They make up a structure called the corpus callosum.
• Function: Coordinates actions on one side of the body with actions
on the other.
• 2. Projection Fibers - Projection fibers serve to connect the
cerebral cortex to the lower brain and spinal cord. They tie the
cerebrum to the rest of the nervous system and to the receptors and
effectors of the body.
• 3. Association Fibers Association fibers serve to connect the
lobes within a hemisphere.
Corpus
Callosum
White Matter of the Cerebrum
• Basal Ganglia
• The white matter of the cerebrum contains several
groups of nuclei called the basal ganglia (caudate,
putamen, nucleus accumbens, globus pallidus,
substantia nigra, subthalamic nucleus).
• Function: controls motor function, regulates muscle
tone, and coordinates rhythmic movements on a
minute to minute basis (e.g. arm swinging while
walking). Works with cerebellum to coordinate
smooth movement with the cerebrum. Disturbances
in function lead to disease.
– Parkinson’s disease -The substantia nigra, part of the basal
ganglia located below the thalamus, has been implicated in
Parkinson’s disease also known as shaky palsy, due to loss
of dopamine secretion.
– Parkinson’s disease appears in people in the age group of
50 to 65 and causes tremors of the limbs, slow movements,
and postural changes.
Examples of basal ganglia (nuclei) in the white matter of the brain
Asymmetry of the Brain
• The brain can be thought of as 2 hemispheres
connected by a bundle of nerve fibers called the corpus
callosum.
• Sensations from one side the body are most commonly
perceived in the cerebral hemisphere on the opposite
side of the body.
• For example: Vision of the left eye is controlled by the
right hemisphere, and vice versa.
• The 2 cerebral hemispheres are asymmetrical in some
structure and function.
• If the left temporal lobe of the brain is damaged, you will
commonly observe language difficulties.
• If the right temporal lobe is damaged, there are no such
difficulties.
• In dyslexia (difficulty in reading), the left temporal lobe is
typically smaller than a right.
Asymmetry of the Brain
• The 2 hemispheres of the cerebrum have the following
responsibilities:
• Left hemisphere
Right hemisphere
Speech
Visual -- spatial relationships
Language
Dreaming
Analytical problem solving
Musical ability
• A right handed person will have a larger left temporal lobe, left
occipital lobe, and right frontal lobe.
• 90% of people are left hemisphere dominant & (right handed).
• A left handed person usually is right hemisphere dominant
and shows no asymmetry (may be ambidexterous).
Diencephalon —
Thalamus and Hypothalamus
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Thalamus - The thalamus is a relay center
for sensory information going to the
cerebrum.
The upper portion of the thalamus is called
the epithalamus that contains the pineal
gland. The pineal gland secretes melatonin,
a hormone, that controls sleepiness and
biological rhythms.
Hypothalamus – The hypothalamus is
extremely important.
It controls many vegetative functions.
That is, functions that are not under
voluntary control.
The hypothalamus is of primary importance
in the maintenance of homeostasis.
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It is an integrating center for important homeostatic functions
and serves as an important link between the autonomic
nervous system and the endocrine system.
Many axons extend to sympathetic and parasympathetic
nuclei in the brain stem and spinal cord.
Pineal
Functions of Hypothalamus=
Homeostasis
• 1. Control of pituitary gland & ANS
– It secretes several hormones that influence the pituitary gland.
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2. Temperature regulation.
3. Control of appetite.
4. Water balance and intake.
5. Gastric secretion.
The hypothalamus is also involved in emotion as a part
of the limbic system.
• The limbic system is important in the expression of fear,
rage, and instinctual sexual behavior. The limbic system
has special neurotransmitters called endorphins which
are natural opiates that lessen pain and stress.
Mesencephalon or Midbrain
• The midbrain serves a relay center
between the forebrain and hindbrain.
Contains the cerebral aqueduct which
connects the 3rd and 4th ventricles.
Metencephalon —
Pons and Cerebellum
• Pons - The pons relays motor information from
the cerebrum to the cerebellum.
• Cerebellum – The cerebellum is the center for
motor coordination of body movements.
• It is important in maintaining equilibrium and in
the coordination of antagonistic muscles.
Myelencephalon — Medulla Oblongata
• The medulla oblongata is sometimes called the brain stem.
However, the brain stem includes the midbrain, the pons, and the
medulla oblongata.
• The medulla oblongata serves to regulate some vital and nonvital
body functions.
• Vital functions
Nonvital Functions
Respiration center
Sneezing
Heart rate (cardiac center)
Coughing
Blood vessel diameter (vasomotor center)
Vomiting
Swallowing
• *The medulla oblongata is where the crossing of fiber tracts
(decussation) takes place and is responsible for the right side of the
brain controlling what takes place on the left side of the body and
vice versa.
Reticular formation
• The reticular formation is found within the
brain stem and regulates consciousness,
that is, whether you are awake, sleeping,
or dreaming. This is called the reticular
activating center (RAS). The RAS
responds to ears (alarm clock), eyes (light
of morning), or painful stimuli which
arouse the cortex.
THE FEMALE BRAIN
Exam 2 - Next Meeting
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1. Bring Scantron form 882-e
2. #2 Pencil
3. Thinking Caps
Format of Exam 2
75Pts. - Pages 9-15 in Syllabus
50 Pts. Multiple choice
10 Pts. Matching
15 Pts. Essay 5 Pts each.
Write on 3 from 8 possible topic choices.