Title: The Brain
1The Brain
2Membranes 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.
3Meninges
4Meninges
5Meninges
- 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.
6Cerebrospinal 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
7Cerebrospinal 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
8Meningitis
Meninges become inflamed, may be viral or
bacterial
9Major 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
10Cerebrum
- 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
11Cerebrum
12Cerebrum
13Cerebral Cortex
14Diencephalon
- Located between cerebral hemispheres and above
the midbrain - Contains the thalamus, hypothalamus, optic
tracts, posterior pituitary gland, pineal gland
15Diencephalon
16Brain Stem
- Connects cerebrum to the spinal cord
- Consists of midbrain, pons, medulla oblongata
17Functions of Brain Stem
- Relay center
- Reflex center
- Medulla oblongata contains regulatory centers for
heart rate, constriction and dilation of blood
vessels, respiration
18Cerebellum
- Reflex center for integrating sensory information
concerning the position of body parts - Coordinates complex skeletal muscle movements
19Hemisphere 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)
20Hemisphere 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!
21Hemisphere 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
22Hemisphere Dominance
- Right brains often choose as careers
- Athletes
- Entrepreneurs
- Sales
- Artist
- Musician
- Craftsman
- dancer
23Hemisphere Dominance
- Left brains often choose careers in
- Law
- Accounting
- Science
- Medicine
24Cranial 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
25A Career Cut Short by Spinal Cord Injury
26The 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?
27Spinal 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
28Spinal 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
29Spinal 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
30Spinal 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
31Spinal 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
32Autonomic 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.
33Two 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
34Autonomic 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
35Autonomic 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
36Autonomic 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.
37Autonomic 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