The Brain

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The Brain

• Anatomy and Physiology

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Membranes cover the brain and spinal cord

• Membranes are called meninges
• Three layers dura mater, arachnoid mater, and
  pia mater
• Dura mater is outer, arachnoid is middle, pia is
  innermost.

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Meninges
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Meninges
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Meninges

• Between the arachnoid and pia maters is the
  subarachnoid space, which contains cerebrospinal
  fluid.
• A series of spaces in the brain, called
  ventricles, also contain cerebrospinal fluid.

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Cerebrospinal Fluid

• Is secreted by specialized capillaries of the
  dura mater layer. These special tissues are
  called choroid plexuses.
• The fluid circulates through the ventricles and
  is reabsorbed into the blood

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Cerebrospinal Fluid

• The pressure remains fairly constant, as fluid is
  secreted and absorbed continuously
• The brain and spinal cord float in the fluid,
  which supports and protects them
• Also controls ions and carries waste to blood

Pressure can be measured, and samples of fluid
can be taken to diagnose infections
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Meningitis
Meninges become inflamed, may be viral or
bacterial
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Major Regions of the Brain

• Cerebrum largest part sensory and motor
  functions, higher reasoning skills
• Diencephalon processes sensory info
• Cerebellum coordinate voluntary muscle
• Brain Stem regulates visceral activities

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Cerebrum

• Divided into lobes
• Lobes are named after the skull bones they
  underlie
• Two hemispheres divided by corpus callosum
• Convoluted surface
• Outermost part is the cerebral cortex

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Cerebrum
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Cerebrum
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Cerebral Cortex
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Diencephalon

• Located between cerebral hemispheres and above
  the midbrain
• Contains the thalamus, hypothalamus, optic
  tracts, posterior pituitary gland, pineal gland

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Diencephalon
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Brain Stem

• Connects cerebrum to the spinal cord
• Consists of midbrain, pons, medulla oblongata

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Functions of Brain Stem

• Relay center
• Reflex center
• Medulla oblongata contains regulatory centers for
  heart rate, constriction and dilation of blood
  vessels, respiration

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Cerebellum

• Reflex center for integrating sensory information
  concerning the position of body parts
• Coordinates complex skeletal muscle movements

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Hemisphere Dominance

• Everyone uses both hemispheres in basic functions
• Right side controls motor functions of the left
  side left side controls motor functions of the
  right side. (stroke)

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Hemisphere Dominance

• Most people have a dominant hemisphere, although
  you can be equally right and left brained
• Right brained or left brained refers to which
  hemisphere is dominant
• Determines your manner of thinking they are not
  the same!

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Hemisphere Dominance

• Left Brain thinkers are
• Logical and sequential
• Rational
• Analytical
• Objective
• Look at the parts

• Right brain thinkers are
• Random
• Intuitive
• Holistic
• Synthesizing
• Subjective
• Look at wholes

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Hemisphere Dominance

• Right brains often choose as careers
• Athletes
• Entrepreneurs
• Sales
• Artist
• Musician
• Craftsman
• dancer

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Hemisphere Dominance

• Left brains often choose careers in
• Law
• Accounting
• Science
• Medicine

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Cranial Nerves

• Twelve pairs of cranial nerves arise from the
  inferior side of the brain
• 1st pair comes from cerebrum
• Other 11 pairs originate from brain stem
• Lead to parts of the head, neck, and trunk

Each nerve has a name and a roman numeral
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A Career Cut Short by Spinal Cord Injury
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The Spinal Cord

• Two functions conduct nerve impulses reflex
  center
• Is part of the CNS
• Is a nerve column going down from brain into the
  vertebral column
• Ends near the 1st or 2nd lumbar vertebrae
• Surrounded by meninges, which continue below the
  L1 and L2 vertebrae

Where would you do a spinal tap to collect CSF
without damaging the spinal cord?
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Spinal Cord

• A cross section shows a core of gray matter
  surrounded by white matter
• Gray matter unmylenated axons and neuron cell
  bodies
• White matter masses of mylenated axons

Notice the three layers of meninges
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Spinal Cord

• The white matter contains 3 sections of
  longitudinal bundles called nerve tracts
  (posterior, anterior, and lateral)
• Ascending tracts of nerves carry sensory
  information to the brain
• Descending tracts carry motor impulses to muscle
  or glands

posterior
lateral
Anterior
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Spinal Nerve Tracts
Posterior section of white matter contains only
ascending nerve tracts The anterior and lateral
sections of white matter contain both ascending
and descending nerve tracts
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Spinal Nerves

• Coming off the spinal cord are 31 pairs of spinal
  nerves
• Grouped and labeled according to the level of
  vertebrae they come from
• These nerves are part of the PNS

C1-C8 T1-T12 L1-L5 S1-S5
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Spinal Nerves

• The 31 pairs branch out to serve various parts of
  the body
• Which nerve serves which parts of the body can be
  seen on a dermatome map

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Autonomic vs Somatic nervous Systems

• Somatic motor pathways of PNS that lead to the
  skin and skeletal muscles
• Autonomic happens without conscious
  effortmaintains homeostasis by regulating smooth
  muscles, blood pressure, breathing rate, heart
  rate, etc.

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Two Divisions of Autonomic

• Sympathetic, which prepares the body for
  stressful, emergency situations
• Parasympathetic, which is most active during
  ordinary, restful conditions, and returns the
  body to normal conditions after the emergency

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Autonomic Nerve Fibers

• Are arranged slightly differently than somatic
  nerve fibers
• A pathway from the brain or spinal cord to the
  skeletal muscle contains two neurons instead of
  just one

Page 241 in your textbook
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Autonomic Nerve Fibers

• The first neuron leaves the brain or spinal cord
  and joins with a mass of neurons called a
  ganglion. This neuron is preganglionic. The
  second neuron that leaves the ganglion is called
  postganglionic

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Autonomic Neurotransmitters

• Acetylcholine is the neurotransmitter secreted by
  preganglionic fibers of both the sympathetic and
  parasympathetic divisions. The postganglionic
  fibers of the parasympathetic also secrete
  acetylcholine
• Norepinephrine is the neurotransmitter secreted
  by the postganglionic fibers of the sympathetic
  division.

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Autonomic Control

• Brain and spinal cord control most of its
  activities
• Medulla oblongata receives sensory impulses and
  send motor responses
• Hypothalamus regulates body temp, hunger, thirst,
  water and electrolyte balances.
• Other brain areas control autonomic system during
  emotional stress