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If I only had a brain………
Meninges –membranes between bone and tissue
protecting brain and spinal cord
3 layers of meninges:
Dura mater-white fibrous CT, blood vessels
and nerves, attaches to inside of cranial cavity,
forms periosteum
Arachnoid mater-middle, weblike, no blood
vessels
Pia mater-innermost, thin, contains nerves
and blood vessels, hugs organs
Cerebrospinal fluid-between arachnoid and pia
mater, fill ventricles
Brain—3 lb mass
100 billion multipolar neurons
3 portions
1. Cerebrum-largest, nerve centers for
sensory and motor, higher mental
functions
 Halves are cerebral hemispheres,
connected by nerve fibers—corpus
callosum, separated by longitudinal
fissure
 Ridges are convolutions (gyri)
 Shallow grooves=sulci
 Deep grooves=fissures
 Lobes: Frontal (motor areas),
parietal, temporal, occipital, insula
 Outermost portion-cerebral cortex
 Nerve fibers cross over—motor area
on right controls left skeletal
muscles
 Hemisphere dominance—one side
of cerebrum controls certain
functions—Left hemi dom. In 90%
of people.
2. Cerebellum-centers for voluntary muscle
mvmt.
 Posture, position of body parts
3. Brain stem-connect parts of nervous
system and regulate visceral (organ)
activities
 Midbrain-reflex centers
 Pons-relays impulses
 Medulla Oblongata-cardiac, vasomotor,
and respiratory centers
4. Diencephalon-contains
Thalamus-sensation awareness
Pituitary gland-growth hormones and
reproductive hormones
Hypothalamus-regulates visceral activity,
overall homeostasis
Limbic system-controls emotions
Spinal cord
-Nerve column from foramen magnum to
intervertebral disk between L1 and L2 vertebrae
-31 segments (spinal nerves)
White matter-myelinated fibers
Gray matter-unmyelinated nerve fibers and
neuron cell bodies
Function of spinal cord:
1. Conducts nerve impulses
2. Center for spinal reflexes
Ascending tracts carry info to brain
Descending tracts carry info from brain
Peripheral Nervous system –nerves that branch
off CNS, divided into Somatic and Autonomic
Somatic N.S.-Connects CNS to skin and skeletal
muscles for conscious activity
Autonomic Nervous systemControls automatic processes, connects to
viscera (organs)
Regulates processes to keep body functioning
2 divisions
Sympathetic division-prepares body for stress
(fight or flight)
Parasympathetic-active under ordinary, restful
conditions, restores rest after stress
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