Download Nervous System

Nervous System
Part 2:
Structures
Central Nervous System Structures
• Brain
• Spinal cord
The Brain
• Operates the body and interprets vast
amounts of information daily
• The average adult human brain weighs 3.1
lbs
• It contains about 100 billion neurons which
function as a unit
• The brain is one of the most mysterious
organs of the body
Parts of the Brain
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Cerebrum
Gyri
Cerebral cortex
Corpus callosum
Diencephalon
Brain Stem
Cerebellum
Cerebrum
• Largest portion of the brain
• Has a highly folded outer layer called the
cerebral cortex
• Underneath the cerebral cortex, are the ridges
or convolutions, called gyri
• It is divided into two hemispheres which are
connected by the corpus callosum
• The corpus callosum is a band of axons that
lies deep in the central groove
• The cerebrum is further divided into 5 distinct
lobes
Cerebral Cortex
• Contains 10-20% of the brain’s total
number of neurons
• Its many folds allow the surface area of
the cortex to fit within the skull
• Different parts of it control information and
sensations from the body and motor
responses
White Matter
• Is the layer beneath the cerebral cortex
• It is composed of myelinated axons
– Myelin is an insulator of neurons
• These axons link regions of the cortex with
each other and with other neural centers
• The crossover of these axons causes
impulses originating in one hemisphere to
be processes by the other half and vice
versa
Left Hemisphere
• Rational & Sequential
• Responds to verbal instructions
• Problem solves by logically and sequentially looking at the
parts of things
• Looks at differences
• Is planned and structured
• Prefers established, certain information
• Prefers talking and writing
• Prefers multiple choice tests
• Controls feelings
• Prefers ranked authority structures
• Is a splitter: distinction important
• Is logical, sees cause and effect
Right Hemisphere
• Intuitive & Simultaneous
• Responds to demonstrated instructions
• Problem solves with hunches, looking for patterns and
configurations
• Looks at similarities
• Is fluid and spontaneous
• Prefers elusive, uncertain information
• Prefers drawing and manipulating objects
• Prefers open ended questions
• Free with feelings
• Prefers collegial authority structures
• Is a lumper: connectedness important
• Is analogic, sees correspondences, resemblances
Lobes of the Brain
• Frontal Lobe- associated with reasoning, planning,
parts of speech, movement, emotions, and problem
solving
• Parietal Lobe- associated with movement, orientation,
recognition, perception of stimuli
• Occipital Lobe- associated with visual processing
• Temporal Lobe- associated with perception and
recognition of auditory stimuli, memory, and speech
• Insula- (Island of Reil) is a lobe deep within the brain
and covered by the other lobes.
– It is believed to be involved with the consciousness and
emotional homeostasis
Diencephalon
• Lies between the cerebrum and the brain stem
• It contains relay centers from information
entering and exiting the brain
• It is divided into two distinct centers:
– Thalamus
– Hypothalamus
• In addition, a set of brain structures called the
limbic system incorporates parts of the thalamus
and hypothalamus, centers in the temporal lobes
and deeper parts of the cerebral cortex
• The limbic system helps govern emotion,
memory and motivation
Thalamus
• Is the uppermost
relay center of the
diencephalon
• It directs most
incoming sensory
signals to the
proper regions of
the cerebral cortex
Hypothalamus
• Helps to maintain
homeostasis
• It also directly and
indirectly controls
much of the body’s
hormone
production
Brain Stem
• Located beneath the diencephalon
• Has three main division:
– Midbrain
– Pons
– Medulla oblongata
• Lying throughout is a diffuse network of
neurons called the reticular formation
– Helps control respiration and circulation
– Helps separate signals that demand attention
from those that are unimportant
Midbrain
• Relays
visual and
auditory
information
Pons
• Relays
communications
between the
cerebral
hemispheres and
the cerebellum
Medulla Oblongata
• Serves as
both a relay
center and a
control center
for heart rate,
respiration
rate, and
other
homeostatic
activities
Cerebellum
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Lies below and behind the cerebral hemispheres
Its surface is highly folded
It helps coordinate muscle action
It receives sensory impulses from muscles,
tendons, joints, eyes and ears, as well as input
from other brain centers
• It processes information about body position
• Controls posture by keeping skeletal muscles in
a constant state of partial contraction
• It coordinates rapid and ongoing movements
Additional Structures
• Cerebrospinal fluid: is a clear bodily fluid that
surrounds the brain and spinal cord
• Has three functions:
– Delivers nutrients to the structures of the nervous
system
– Removes wastes from the brain and spinal cord
– Protects the brain and spinal cord from trauma
• Meninges: is a system of membranes which
envelop the CNS
• They are made up of three layers: pia mater,
arachnoid mater, & dura mater
Spinal Cord
• Is a column of nervous tissue that starts at the
medulla oblongata
• It runs through the vertebral column
• It carries nerve signals back and forth like a
superhighway
• It has an outer sheath of white matter
• Its rigid inner core is made up of gray matter
– Gray matter is composed of dendrites, unmyelinated
axons and the cell bodies of neurons
Peripheral Nervous System
• Constantly interacts with the central
nervous system via 12 pairs of cranial
nerves and 31 pairs of spinal nerves
• Nerves are the bundles axons and
dendrites of many neurons
• Each spinal nerve has a dorsal root and a
ventral root
Nerve Distinctions
• Dorsal roots carry signals to the CNS from
sensory receptors
– Sensory receptors are specialized neurons that detect
a stimulus such as light, pressure, or heat
• Ventral roots contain the axons of motor
neurons, which carry information from the CNS
to muscles and glands
– Motor neurons carry information from the CNS to
muscles and glands
– Interneurons relay information between other neurons