Transcript The Brain Notes

The CNS
The Brain, Spinal Cord, and
Nerves
Human Anatomy and Physiology
CHS
• In the CNS, the brain helps to control all the body
systems and organs. The brain also allows us to
think, feel, remember, and imagine. The brain
communicates with the rest of the body through
the spinal cord and the nerves. Nerves tell the
brain what is going on in the body at all times.
This system also gives instructions to the body
about what to do and when to do it.
• The spinal cord is a thick bundle of nerves,
connecting your brain to the rest of your body. It
is protected by the backbone and carries
messages to and from your arms, legs, and trunk
of the body.
The Brain
• Appearance: 2 fist-fulls of pinkish gray tissue,
wrinkled like a walnut with the texture of cold
oatmeal.
• It weighs a little over 3 pounds.
• It is made up of 4 major regions.
BRAIN—4 main parts
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Cerebrum ( 2 cerebral hemispheres) –
--largest portion (larger than other 3 together). As it grows, covers
most of brainstem.
--most superior, largest, 85% of mass
--4 lobes
--receives messages about senses, controls speech, learning,
intelligence, and personality. “thinking part”
Diencephalon –superior to brain stem (can only see from cross
section)
• Thalamus
• Hypothalmus
Brain stem /medulla—controls autonomic system; connects
cerebrum to spinal cord.
• Medulla oblongata
• Pons
• Midbrain
Cerebellum – “little brain”—controls balance and movement of
muscles
Cerebrum
Wrinkly, large part of the brain.
Higher mental functioning, problem solving.
CEREBRUM
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Cerebral Cortex – dark outer area consists of
gray matter; contains cell bodies of 75% of all
neurons in the nervous system. This is outermost
tissue layer on the cerebrum and is the most
evolved portion of the brain. This area controls
conscious thought, reasoning, and abstract
mental functioning.
Gyri (gyrus)–elevated regions (bumps)
Sulci (sulcus)– grooves or furrows.
Fissures – deeper grooves; divide brain into
lobes.
Longitudinal fissure – separates brain into Right
and left cerebral hemispheres
Corpus callosum – connects both hemispheres
• Cerebrum has 3 basic regions:
• a superficial (outside) cortex of gray
matter (cerebral cortex),
• an internal white matter,
• and the basal nuclei, islands of gray
matter situated deep within the white
matter.
Gray Matter vs. White Matter
• Gray matter—pinkish-gray color—contains cell bodies, dendrites, and
axon terminals of neurons…so this is where all the synapses are;
nonmyelinated axons.
– Cerebral cortex
– Specialized regions of the brain involved in computation, thinking, memory
storage, muscle control, sensory perceptions, such as seeing and hearing,
emotions, and speech.
• White matter—made of long myelinated axons connecting different parts
of gray matter to each other.
– Diencephalon (between brainstem and cerebellum)
– Relays sensory information from the rest of the body to the cerebral cortex
(allows NS to communicate) , ANS functions, expression of emotions, release
of hormones, and regulation of food and water intake.
– Limbic system
• Youtube video: Gray vs White matter
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www.youtube.com/watch?v=AubAJx7-BcI
The cerebrum is divided into two
hemispheres, right and left.
• Left hemisphere —responsible for speech,
reading, writing, and logical thinking. These
are more linear and analytical functions.
• Right hemisphere —responsible for emotions,
creativity, musical, and artistic ability. These
are more intuitive, creative, and holistic
functioning.
• Cerebral Cortex—speech, memory, logical,
and emotional response, as well as
consciousness, interpretation of sensation,
and voluntary movement.
• White matter of brain lies under cortex and
makes up bulk of cerebrum
– Contains tracts (nerve fibers within the CNS)
inside gray matter.
• Cerebrum is divided into 4 lobes:
– Frontal - forehead
– Temporal – above ears
– Parietal – top sides
– Occipital – back
• Lateral fissure divides temporal lobe from
frontal & parietal lobes
• Central sulcus divides frontal & parietal lobes
• No distinct boundary between parietal &
occipital lobes
• Transverse fissure – separates cerebrum &
cerebellum
Lobes of cerebrum
Functional Areas of Frontal Lobe
• Function: Higher order thinking skills, problem
solving, planning, behavior, attention, creative
thought, judgment, initiative, intelligence,
inhibition, personality, emotional traits and
smell.
• Broca’s Area—coordinated muscle movement
for speech; language production
• Primary motor cortex
– Controls voluntary actions of specific muscles
or groups of muscles on the opposite side of
body; Storage of motor patterns.
Functional Areas of Parietal Lobe
• Functions: Sense of touch, processing visual
information, language, and math; learning
comprehension; body orientation
• Primary somatosensory cortex
– Behind central sulcus in postcentral gyrus
– Receives impulses for touch,
proprioception (self awareness), pain, &
temperature
Functional Areas of Occipital Lobe
• Functions: Visual processing,
recognition, reading.
Functional Areas of Temporal Lobe
• Major Functions: Hearing and speech,
auditory and visual memory, music, fear,
and sense of identity; expressed
behavior.
• Olfactory area – smell
• Auditory area – hearing
• Wernicke Area--
Right and Left Hemispheres
Corpus callosum
• The right and left hemispheres are
connected by the corpus callosum.
• 200 million axons.
• It’s function is to facilitate communication
between the two hemispheres.
• The largest collection of white matter in the
brain—so faster transmission of information.
DIENCEPHALON
• Sits atop the brainstem and is enclosed
by the cerebral hemispheres; the
interbrain.
• (Thalamus, hypothalamus, epithalamus)
– Relay station for sensory impulses to
cerebral cortex (white matter)
– Plays a role in emotions, memory,
awareness and cognition
Thalamus
• Relay station (connections) for sensory
impulses passing upward to the sensory
cortex. As impulses surge through thalamus,
we have a crude recognition of whether the
sensation we are about to have is pleasant or
unpleasant. It is the neurons of sensory cortex
that actually localize and interpret the
sensation.
• Hypothalamus –“under the thalamus”
(controls ANS)
– Controls regulation eating & drinking
(water balance and metabolism/apetite)
– Controls body temperature
– Regulation of consciousness, emotional
and behavior, response to anxiety, diurnal
(circadian) rhythms – synchronizes daynight cycle (sleep patterns)
– Regulates the pituitary gland.
• Epithalamus contain
• Pineal gland (part of endocrine system)—
produces
– Melatonin- sleep/wake patterns, seasonal
functions.
• Choroid plexus (knots of capillaries forming
the cerebrospinal fluid)
• Pituitary Gland—(hangs off hypothalamus)
produces hormones that control many
functions of other endocrine glands.
Limbic System
– Not a structure, but a series of nerve
pathways incorporating structures deep in
the temporal lobe.
– Thalamus, hypothalamus, amygdala,
hippocampus.
– Emotional aspects of behavior; Control and
expression of mood and emotion, processing
and storage of recent memory, control of
appetite and emotional response to food;
thirst, sex, pain, and pleasure centers.
– Produces hormones.
– Linked to depression; some psychiatric
disorders, such as anxiety.
• Amygdala
– almond-shape set of neurons located deep in the brain's medial
temporal lobe.
– integrative center for emotions, emotional behavior, and motivation;
intense emotion, such as panic and fear, panic attacks, pleasure.
Hippocampus
– Forming, organizing, and storing memories.
– Connecting smell and sound to memories.
– Spatial orientation.
– Horseshoe shaped.
– Acts as a memory indexer by sending memories
out to the appropriate part of the cerebral
hemisphere for long-term storage and retrieving
them when necessary.
BRAIN STEM
• About the size of the thumb in
diameter and 3 inches long.
• Connects spinal cord to white matter to
cerebral cortex.
• Regulate visceral functions (autonomic
systems).
Pons
–Pons means “bridge”
–Relaying sensory information;
Connects spinal cord with brain & links
parts of brain with one another by way
of tracts (nerve fibers within the CNS)
–Aid in control of breathing and other
autonomic functions.
–Sleep
• Medulla Oblongata
– Most inferior part of the brainstem.
– Merges into spinal cord.
– Fiber tracts
– Regulates:
• Cardiac center – heart rate
• Vasomotor center – constricts blood
vessels (blood pressure)
• Respiratory center – rate and depth
of breathing
• Swallowing
• Vomiting
• Midbrain
• Cerebral aqueduct—tiny canals that travel
through the midbrain.
• Cerebral peduncles--Convey ascending and
descending impulses.
• Corpora quadrigemina—reflex centers
involved with vision and hearing.
Reticular (Activating) Formation
• Extends entire length of brain stem.
• Receives input from most of the bodies
sensory systems (sight, sound, etc)
• Diffuse mass of gray matter.
– Responsible for maintaining
consciousness & awakening from
sleep; focus.
– Damage to this area can result in
coma.
CEREBELLUM
• White matter tracts are called “arbor vitae”
tree of life. (cauliflower)
• 2 hemispheres, convoluted surface.
• Outer cortex (gray matter) and inner region
(white matter).
• Coordination, balance, and posture;
coordinates sensory input from inner ear and
the muscles to provide accurate control of
position and movement.
• Damage would show loss of muscle tone and
inaccurate movements
• Located in the back of the brain.
Cerebellum
Cerebellar peduncles – connect cerebellum to other parts of brain; convey
impulses.
PROTECTIONS & COVERINGS
• The CNS is protected by:
– Bone – cranium and vertebral column
– Meninges – 3 connective tissue layers located
between the bone and the soft tissue of the
nervous system.
• Dura mater – outermost layer; attached to
periosteum; many blood vessels and nerves.
• Arachnoid mater – “spiderweb” middle layer;
no blood vessels
• Pia mater – inner , nearly transparent
membrane, contains nerves and blood vessels to
nourish cells. Follows contours of brain and
spinal cord.
MENINGES
Meningitis – inflammation
of meninges
Subdural space – fluid filled area between
dura and subarachnoid maters (cerebral
spinal fluid).
Cerebralspinal fluid (CSF) and
ventricles
• Watery “broth” similar to blood plasma surrounding
the outer surface of the brain.
• Provides cushion and protection for fragile nervous
tissue from blows and other trauma.
• The CSF also maintains and controls the extracellular
environment and circulates endocrine hormones.
• Within the brain, there are a number of cavities called
ventricles (4). They are filled with CSF.
• Continually moving through brain and spinal cord.
Changes in CSF indicate meningitis or other brain
inflammation. The test for this is a lumbar (spinal) tap.
• Watch a video of a lumbar puncture:
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https://www.youtube.com/watch?v=yYZxNsnf18Y&feature=youtu.be
Cranial Nerves
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1. Olfactory
2. Optic
3. Oculomotor
4. Trochelear
5. Trigeminal
6. Abducens
7. Facial
8. Vestibulocochlear/Acoustic
9. Glossopharyngeal
10. Vagus
11. Accessory (spinal accessory)
12. Hypoglossal
Cranial Nerve Functions
Spinal Nerves