Transcript Ch. 13 Central Nervous System

Ch. 13 Central Nervous
System
Introduction
 The CNS contains:
– Brain - encased by cranium
– Spinal cord - encased by vertebrae
Coverings of the brain and spinal cord
Meninges membranes between bone and soft tissue
– Dura mater – outermost, contains blood vessels
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Forms periostium of skull bones
Forms partitions between lobes of brain and sinuses
provides resistance to pathogens
Prevents cerebral spinal fluid leaks
– Arachnoid mater – middle. Thin, avascular
– Pia mater – innermost, vascular, thin
– Attached to brain and spinal cord surface.
 Spaces
– Epidural-between dura mater and covering of spinal
cord.
– Subdural – between dura mater/arachnoid mater.
Contains serous fluid
– Subarachnoid – between arachnoid and pia.
Contains cerebrospinal fluid
 Purpose – supportive cushion.
Structure of the Spinal cord
 Description and location
 Structure
– 31 Segments with a pair of spinal nerves in
each segment
– 8 cervical
– 12 thoracic
– 5 lumbar
– 5 sacral
– CX - in coccyx
– Cervical enlargement
– Lumbar enlargement
– Plexus - clump
– Grooves
 Anterior media fissure
 Posterior median sulcus
– White matter – myelinated fibers
– Gray mater - cell bodies and dendrites of
interneurons. (butterfly shaped)
Function of the spinal cord
 Functions
– Transmit impulses
– House spinal reflexes
 Ascending (sensory)
 descending tracts (motor)
 Names of tracts – identify origin and
termination of fibers in tract (ex.
Spinothalamic tract)
The myteries of the human brain
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The brain
 Introduction - largest part of
the nervous system
 100 billion multipolar
neurons.
 Divisions
– Cerebrum – largest/higher
mental functions
– Diencephalon – process
sensory input
– Cerebellum-coordinates
muscular activity
– Brainstemcoordinates/regulates
visceral activities
The cerebrum
 The largest part of the brain
 Surface of the brain is marked by
convolutions, sulci, fissures.
 Lobes of the brain are named
according to the bones they underlie.
 2 hemispheres connected by Corpus
callosum
– Convolutions, sulci, fissures
– Lobes
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Frontal
Parietal
Temporal
Occipital
– Cerebral cortex - thin layer of gray
mater - 75% of cell bodies
Functions of the cerebrum
 Higher brain functions
– Interpretation of sensory input
– Initiating voluntary muscular movement
– Memory
– Integrating information for reasoning
– Consciousness
– Language
– Emotions
Functional regions of cerebral cortex
 Primary motor area-frontal lobes, anterior wall
 Broca’s area coordinates muscular activity for
speech
 Frontal eye field - controls eye and eye lid
movement
 Sensory areas - interpret sensory input,
produce feelings/sensations
 Association areas interpret sensory impulse,
reasoning, judgment, emotions, story memory
 Cross-over - right side controls left side of
body, etc.
 Interpretive areas-located where lobes come
together - higher intellectual processes.
 Damage
– Occipital lob - sight and images
– Temporal lobe - recent memories - inability to
form long term memories.
Hemisphere dominance
 Both cerebral hemispheres receive/analyze
 Most people exhibit dominance of left or right
hemispheres.
 Left hemisphere is dominant in 90%
 Left hemisphere dominance usually results in
being right handed, etc.
 Non dominant hemisphere specialize in nonverbal
function, emotion control/intuitive thinking
Ventricles and cerebrospinal fluid
 Description - series of connective
cavities containing cerebrospinal
fluid. Continuous with the spinal
cord
 Choroid plexuses
– Specialized capillaries that Secrete
cerebrospinal fluid
 Comes from lateral ventricles
 Cerebrospinal fluid
– Nutritive
– Protective
 Pressure - normally constant.
Infection /tumor can increase
pressure - causes damage
Diencephalon
 Location - above brain stem
 Contains:
– thalamus -sorts and directs sensory
information - filters non-essential
information
– Hypothalamus - maintains
homeostasis/ linked to endocrine
system
– Optic tracts and chasmas - connect
sense of sight
– Infundibulum - attachment for pituitary
– Pituitary gland - certain hormone
production.
– Pineal gland - puts you to sleep
– Limbic system - controls emotional
experience and expression
 Guides behavior that increases
chance of survival.
 Consists of
– Midbrain- conveys impulses to and
from other parts of the brain
 Reflex centers
Brainstem
– Pons-between midbrain and
medulla oblongata
 Regulates rate and depth of
breathing
 Transmits impulses between brain
and spinal cord
– Medulla oblongata - transmits
ascending and descending
impulses
– Controls visceral functions cardiac center - heart rate, blood
pressure control, respiratory
center, cough and vomiting
centers, sneezing
– Reticular formation-wakes up the
cerebral cortex
 Decreased activity results in sleep,
increased - wakefulness
 Filters sensory impulses
 If damaged, can’t wake from a
coma.
Cerebellum
 Made of two hemispheres connected in the
middle.
 Cerebellar cortex - gray matter
 Communicates with others parts of cns.
 Integrates sensory information about position of
body parts and coordinates skeletal muscle
activity to maintain posture.
language
Ability to speak/write words and ability to
understand spoken/written words.
Speech center – areas in frontal, parietal,
temporal lobes.
Left cerebral hemisphere contains speech
centers in 90% of population
Aphasias - damage to speech centers - can’t
speak.
Emotions
 Limbic system -known as the “emotional
brain”
 Medial surface of cerebrum and region
called hippocampus
 Connection to olfactory sense
Memory
 Cortex stores and retrieves short and long term
memory
 Repetition is the key to transferring information
from short to long term memory
 If you don’t use it you lose it.
 Closely connected to limbic system
 Forgetting is the atrophy of a neural
connection that was created when learning
took place.