Ch. 13 Central Nervous System
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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
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
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.