Transcript Ch. 8 AP PP 2- Brain - Kalp-resources

THE HUMAN BRAIN
THE AMAZING BRAIN!!!
- the brain contains about 35 billion neurons!
- all of our dreams, passions, memories,
and plans are the result of brain activity
- the brain contains about 98% of the neural
tissue of the body
- average brain weighs about 3 pounds
- male brains are about 10 percent larger than
female brains, but larger brains don’t
indicate more intelligence!
DIVISIONS OF THE BRAIN
There are 6 major regions of the adult brain:
1. Cerebrum
2. Diencephalon
3. Midbrain
4. Pons
5. Medulla oblongata
6. Cerebellum
SOME QUICK FACTS:
1. CEREBRUM
- Can be divided into paired CEREBRAL
HEMISPHERES
- conscious thoughts, sensations, intellectual
functions, memory storage and retrieval,
and complex movements originate here
2. DIENCEPHALON
- hollow, connected to cerebrum
- its sides form the THALAMUS, which
contains relay and processing centers for
sensory info
- HYPOTHALAMUS (floor of diencephalon) is
connected to the pituitary gland
- hypothalamus contains centers involved with
emotions, autonomic function, and hormone
production
- pituitary gland links the nervous and
endocrine systems
3. MIDBRAIN
- along with pons and medulla oblongata,
forms the BRAIN STEM
- nuclei in the midbrain process visual and
auditory info and generate involuntary motor
responses
- also contains centers that maintain
consciousness
4. PONS
- acts like a bridge to connect the
cerebellum to the brain stem
- contains nuclei involved with somatic and
visceral motor control
- also connected to medulla oblongata
5. MEDULLA OBLONGATA
- attached to spinal cord
- relays sensory info to thalamus and other
brain stem centers
- contains centers that regulate heart rate,
blood pressure, respiration, and digestive
activities
6. CEREBELLUM
- adjusts voluntary and involuntary motor
activities on the basis of sensory info and
stored memories of previous movements
Ventricles
The brain has a central passageway that
expands to form 4 chambers- VENTRICLES
- Each hemisphere contains a large
LATERAL VENTRICLE
* there is no direct connection between the
2, but an opening called the interventricular
foramen allows each to communicate with
the THIRD VENTRICLE
- The midbrain has a slender canal called the
mesencephalic aqueduct which connects
the third ventricle with the FOURTH
VENTRICLE
* in the medulla oblongata, the fourth
ventricle narrows and becomes continuous
with the central canal of the spinal cord
Cerebrospinal Fluid (CSF)
Surrounds and bathes exposed surfaces of
CNS
- cushions delicate neural structures
- supports- the brain floats in CSF
- can be drawn to diagnose injury,
infection, or disease
- produced at CHOROID PLEXUS, a network
of capillaries that extend into each ventricle
- entire volume of CSF is replaced every 8
hours
Cerebrum
The cerebrum is the largest region of the
brain, and the site where conscious thought
and intellectual functions originate
- contains gray and white matter
STRUCTURE OF CEREBRUM
CEREBRAL CORTEX- covers superior and
lateral surfaces of cerebrum
- this outer surface forms a series of elevated
ridges or GYRI, which are separated by
shallow depressions called SULCI, or
deeper grooves called FISSURES
The 2 HEMISPHERES are separated by a
deep longitudinal fissure
- extending laterally from the longitudinal
fissure is a deep groove called the
CENTRAL SULCUS
Each hemisphere can be divided into lobes
- named after overlying bones of skull
- in each lobe, some regions are concerned
with sensory info. and others with motor
commands
Each hemisphere receives sensory info. from
and sends motor commands to opposite
sides of the body
MOTOR AND SENSORY AREAS
OF CORTEX
The central sulcus separates motor and
sensory portions of the cortex
- PRECENTRAL GYRUS- surface is the
primary motor cortex
* here neurons direct voluntary movements
by controlling somatic motor neurons in the
brain stem and spinal cord
- POSTCENTRAL GYRUS- contains primary
sensory cortex
* neurons here receive somatic sensory
information from touch, pressure, pain, and
temperature receptors
Other sensations arrive at other portions of
the cortex:
- visual cortex
- gustatory cortex (taste)
- auditory cortex
- olfactory cortex (smell)
ASSOCIATION AREAS OF THE
CORTEX
Sensory and motor regions of the cortex are
connected to association areas that interpret
incoming data or coordinate a motor
response
SOMATIC SENSORY ASSOCIATION AREA
- monitors activity in the primary sensory
cortex
- allows you to recognize a very light touch
SOMATIC MOTOR ASSOCIATION AREA
- responsible for coordinating learned
movements
CORTICAL CONNECTIONS
Regions of cortex are interconnected by the
white matter below
- the white matter interconnects areas within a
single cerebral hemisphere and links the 2
hemispheres across the CORPUS
CALLOSUM
PROCESSING CENTERS OF
CORTEX
There are “higher-order” integrative centers that
receive information through axons from many
different association areas
- these areas control extremely complex
motor activities and perform complicated
analytical functions
1. GENERAL INTERPRETIVE AREA
- receives info. from all sensory association
areas
- is present only in 1 hemisphere (usually left)
- damage to this area effects ability to
interpret what is read or heard
2. SPEECH CENTER
- regulates patterns of breathing and
vocalization needed for normal speech
- damage can cause difficulty speaking even
when you know which words to use; or
talking constantly but using the wrong words
3. PREFRONTAL CORTEX
- coordinates info. from association areas
of the entire cortex
- performs abstract functions like predicting
future consequences of events or actions
- damage leads to problems in estimating
time relationships between events
A QUICK LESSON ON MEMORY….
FACT MEMORIES are specific bits of
info.
- such as the color of a stop sign
SKILL MEMORIES are learned
behaviors
- such as tying your shoes
2 Classes of memories:
1. SHORT–TERM- do not last long, but
can be recalled immediately
- Ex: phone number
2. LONG-Term- remain for much longer
* the conversion from short to long
is called MEMORY CONSOLIDATION
* most long-term memories are stored
in the cerebral cortex
AMNESIA- loss of memory from
disease or trauma
- type of memory loss depends on the
regions of the brain affected
Basal Nuclei
The basal nuclei direct activities that are outside
of our conscious awareness
- they are masses of gray matter that lie below
the lateral ventricles and within the white matter
of each cerebral hemisphere
COMPONENTS:
1. Caudate Nucleus
2. Lentiform Nucleus- lies below caudate nucleus
* globus pallidus
* putamen
3. Amygdaloid body- lies below the
lentiform nucleus
The basal nuclei are involved with the
subconscious control of skeletal muscle
tone and coordination of learned
movement patterns
- they do NOT begin a movement, but
provide pattern and rhythm once a
movement is started
http://www.colorado.edu/kines/Class/IPHY3730/image/figure5-31.jpg
Limbic System
The LIMBIC SYSTEM includes the olfactory
cortex, several basal nuclei, gyri, and
tracts along the border of the cerebrum
and diencephalon
FUNCTIONS:
1. Establishing emotional states and
related behavioral drives
2. Linking conscious functions of cerebral
cortex with unconscious functions of brain
stem
3. Long-term memory storage and retrieval
* damage to HIPPOCAMPUS that
occurs in Alzheimer’s interferes with
memory storage and retrieval
The limbic system also includes
hypothalamic centers that control:
- emotional states- rage, fear, sexual
arousal
- reflex movements that can be consciously
activated (chewing, swallowing)
http://general.rau.ac.za/psych/Resources/Honours/Neuropsych/Downloads/downloadstr/Lect2opt/limbic%20system.jpg
Diencephalon
The DIENCEPHALON provides switching and relay
centers that integrate conscious and
unconscious sensory info. and motor
commands
3 COMPONENTS:
1. EPITHALAMUS
- forms roof of diencephalon
- contains PINEAL GLAND- endocrine structure
that secretes the hormone MELATONIN
2. THALAMUS
- final relay point for all ascending sensory info.
other than olfactory that will reach our
conscious awareness
- acts as a filter, passing on to the primary
sensory cortex only a small portion of arriving
sensory info.
- also plays a role in coordinating voluntary
and involuntary motor commands
3. HYPOTHALAMUS
- contains important control and integrative
centers in addition to those associated
with the limbic system
MANY DIVERSE FUNCTIONS:
- subconscious control of skeletal
muscle contractions associated with
rage, pleasure, pain
- adjusting activities of autonomic centers of
pons and medulla oblongata (heart rate,
blood pressure)
- secreting hormones
- producing behavioral drives involved in
hunger and thirst
- regulating normal body temperature
Midbrain
The MIDBRAIN contains 2 pairs of sensory
nuclei or COLLICULI dealing with processing
of visual and auditory sensations
- SUPERIOR COLLICULI- controls reflex
movements of eyes, head, and neck in
response to visual stimuli (flash of light)
- INFERIOR COLLICULI- control reflex
movements of head, neck and trunk to
Descending bundles of nerve fibers make up
the CEREBRAL PEDUNCLES
The midbrain contains the RETICULAR
FORMATION, which regulates many
involuntary functions
- contains the reticular activation system
(RAS) which directly affects the activity
of the cerebral cortex
http://www.stanford.edu/group/hopes/rltdsci/trinuc/f_f10midcereb.jpg
Pons
The PONS links the cerebellum with the
midbrain, diencephalon, cerebrum, and
spinal cord
Cerebellum
The CEREBELLUM is an automatic
processing center
2 IMPORTANT FUNCTIONS:
1. Adjusting postural muscles of body to
maintain balance
2. Programming and fine-tuning movements
controlled at conscious and subconscious
levels
- the cerebellum compares motor commands with
proprioceptive info. (position sense) and performs
adjustments needed to make movement smooth
- tracts that link the cerebellum with these different
regions are the CEREBELLAR PEDUNCLES
- cerebellum can be permanently damaged by trauma,
stroke, and drugs- produce ATAXIA (disturbance in
balance)
Medulla Oblongata
The MEDULLA OBLONGATA connects the
brain with the spinal cord
- all communication between the brain and
spinal cord involves tracts that ascend or
descend through the medulla oblongata
* CARDIOVASCULAR CENTERS- adjust
heart rate, strength of cardiac
contractions, and flow of blood
* RESPIRATORY RHYTHMICITY CENTERSset basic pace for respiratory movements
PEREPHERAL NERVOUS SYSTEM
PNS
The PERIPHERAL NERVOUS SYSTEM
(PNS) is the link between the neurons
of the central nervous system (CNS)
and the rest of the body
- all sensory information and motor
commands are carried by axons of
the PNS
- these axons, bundled together and
wrapped in connective tissue, form
PERIPHERAL NERVES
Cranial nerves originate from the brain
and spinal nerves connect to the spinal
cord
- the PNS also contains both the cell
bodies and the axons of sensory
neurons and motor neurons of the
autonomic nervous system
Cranial Nerves
There are 12 pairs of CRANIAL NERVES
that connect to the brain
- they are numbered according to
their position along the
longitudinal axis of the brain
- you will label and identify the functions
of these nerves
Spinal Nerves
There are 31 pairs of spinal nerves that
can be grouped according to the region
of the vertebral column from which they
originate
- 8 pairs of cervical nerves
- 12 pairs of thoracic nerves
- 5 pairs of lumbar nerves
- 5 pairs of sacral nerves
- 1 pair of coccygeal nerves
Each pair of spinal nerves monitors a
specific region of the body surface
known as a DERMATOME
- dermatomes are clinically important
because damage or infection of a spinal
nerve or dorsal root ganglia will
produce a characteristic loss of
sensation in specific parts of the skin
http://anatomy.med.umich.edu/modules/spinal_cord_module/Files/SC_cnspnsimg.jp
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http://www.stephblog.com/dermatomes.jpg