Download Unit Eight - Objectives 1-6

Anatomy & Physiology I
Unit Eight
Spinal Cord
Anatomy
Spinal Cord Anatomy
The Reflex
Arc
The Reflex
Arc
The Brain
The brain is the major integrating
organ of the CNS
Millions of stimuli to the brain each
day elicit coordinated and
integrated responses
The Brain
The brain is divided into three major
components:
= cerebrum
= cerebellum
= brainstem
The Brain
The cerebrum is the component of
the brain that is the seat of sensory
perception, language, memory,
thoughts, comprehension and
conscientiousness
Anatomically it is divided into two
halves called cerebral hemispheres
The Brain
The cerebral hemispheres are
separated by a deep groove called
the longitudinal fissure
The cerebral hemispheres are
connected at the bottom of the
longitudinal fissure by a thick
bundle of nerve tissue called the
corpus callosum
The Brain
The cerebrum is marked by thick
folds called gyri (gyrus)
The gyri are separated by shallow
grooves called sulci (sulcus)
This folding and convoluting
markedly increases the surface area
of the cerebrum
The Brain
The Brain
Some sulci, such as the central
sulcus, are more prominent and
divide the cerebral hemispheres
into four lobes that are anatomically
and functionally distinct
The Brain
The lobes are named for the cranial
bone under which they are found:
* frontal
* parietal
* occipital
* temporal
The Brain
The frontal lobe is concerned with
planning, memory, mood, thinking,
emotion and motivation
The parietal lobe is concerned with
sensory reception & integration of
taste, some vision and somesthetic
sensation (temperature, touch,
stretch, pain,
The Brain
The occipital lobe is the principle
vision center of the brain
The temporal lobe is concerned with
hearing, smell, learning, memory,
visual recognition and emotional
behavior
The Brain
The Brain
Cerebral white matter makes up
most of the volume of the cerebrum
and is composed of myelinated
nerves that communicate and
coordinate with other parts of the
brain
The Brain
Cerebral gray matter is found in
three places:
> cerebral cortex
> basal nuclei
> limbic system
The Brain
The Brain
The cerebral cortex is the outer layer
of the hemispheres and constitutes
approximately 40% of the brain
It is extensively associated with
sleep, memory, cognition, emotion,
sensation, motor control and
language
The Brain
The basal nuclei gray matter buried
in white matter that are involved in
motor control through a feedback
circuit that plans and executes
movements
The limbic system is an important
center for emotion and learning,
such as gratification and aversion
The Brain
The primary motor control in the
cerebral cortex is found in the frontal
lobe and precentral gyrus
The motor association area of the
frontal lobe plans movements and
behaviors, while the primary motor
cortex of the precentral gyrus sends
out messages that carry them out
The Brain
Motor control in the
cerebral cortex
The Brain
Sensory control in the
cerebral cortex
The Brain
Association areas in the
cerebral cortex
The Brain
The cerebellum is located inferior to
the posterior side of the cerebrum
It is the central
area for motor
coordination,
equilibrium
and time
keeping
The Brain
The brainstem is the shaft-like
structure that connects the cerebrum
& cerebellum to the spinal cord
Located in it are a variety of centers
that control respiration, heart rate,
blood pressure, and involuntary
actions such as coughing,
swallowing & sweating
The Brain
The brainstem also acts as a relay
system between the cerebrum &
cerebellum and the spinal cord
All but the first cranial nerves
originate from the brainstem
The Brain
It is comprised of
four segments:
~ diencephalon
~ midbrain
~ pons
~ medulla
oblongata
The Brain
The diencephalon is made up of
three structures:
- thalamus
- hypothalamus
- epithalamus
The Brain
The thalamus is largely a relay
center, filtering somesthetic &
special sense messages sent from
the body to the cerebral cortex
It also plays a key role in motor
control by providing communication
between the cerebral cortex and
basal nuclei
The Brain
The thalamus also involved in the
memory and emotional functions of
the limbic system
The hypothalamus is a major control
center for the ANS and acts as the
coordinator between the nervous
and endocrine systems
The Brain
The hypothalamus produces seven
hormones that directly influence the
release of hormones from the
pituitary gland, a major component
in the endocrine system
The Brain
Some of the visceral functions of the
hypothalamus are:
* hormone secretion
* thermoregulation
* ANS control
* food & water intake
* sleep & waking
* memory & emotions
The Brain
The epithalamus is comprised
mainly of the pineal gland that is
most active before the age of 7
Its functions are still unclear, but
may help regulate puberty and may
be the seat of some mood disorders
The Brain
The pituitary gland is attached
inferiorly to the hypothalamus and is
a part of the endocrine system
It is divided into two lobes and
secretes eight hormones that control
a variety of body functions
The Brain
Anterior pituitary hormones:
* FSH (follicle stimulating hormone)
* LH (luteinizing hormone)
* TSH (thyroid stimulating hormone)
* ACTH (adrenocorticotropic
hormone)
* PRL (prolactin)
* GH (growth hormone)
The Brain
Posterior pituitary hormones
(stored):
* ADH (antidiuretic hormone)
* OT (oxytocin)
The secretion of pituitary hormones
are strongly subject to the control of
the brain & hypothalamus
The
Brain
The Brain
The optic chiasm is formed by the
crossing of the optic nerves just
inferior to the hypothalamus and
anterior to the pituitary gland
The Brain
The Brain
The midbrain is a short section of the
brainstem with a variety of functions:
~ anchors the cerebrum to the
brainstem
~ contains the cerebral aqueduct
~ relays inhibitory signals to the
thalamus
The Brain
The midbrain is a short section of the
brainstem with a variety of functions:
~ controls eye movements with the
cranial nerves III & IV
~ contains a major portion of the
reticular formation
The Brain
The Brain
The reticular formation is a loosely
organized web of gray matter that
runs through the entire brainstem
and into the cerebrum
It functions in cardiovascular
control, pain modulation, sleep &
consciousness, and habituation
The Brain
The pons functions as a relay center
from the cerebrum to the cerebellum
and medulla oblongata, sends
information to the thalamus, and
contains respiratory centers
Cranial nerve V arises in the pons
The Brain
The medulla oblongata contains
ascending and descending tracts
that carry information for the control
of skeletal muscles
The medulla oblongata also contains
important motor centers that play a
major role in cardiac, vasomotor and
respiratory control
The Brain
Cranial nerves VI, VII & VIII arise
from the junction between the
medulla and the pons
The Brain
The Brain
The skull is protected externally by
the skull and internally by three
layers of membrane called the
meninges
The three meninges layers are:
+ dura mater
+ arachnoid mater
+ pia mater
The Brain
The Brain
The ventricles are four chambers
found internally in the brain that are
filled with cerebrospinal fluid (CSF)
The CSF provides buoyancy,
protection and chemical stability for
the brain
The Brain
The CSF is continually moving
through the ventricles and central
canal and is daily renewed by the
brain
The ventricles are lined with a
network of capillaries called the
choroid plexus, which is in turn
covered with ependymal cells
Brain Nutrition
The brain is only 2% of the body weight, but receives 15%
of the blood and consumes 20% of the oxygen and glucose
Due to the high demand for ATP in neurons, they must
have large amounts of oxygen and glucose
Brain Nutrition
Because of the high demand for oxygen and glucose, the
brain must be adequately supplied with blood at all times
If blood flow to the brain is interrupted for even short
periods of time it can result in unconsciousness, brain
damage or death
Brain Nutrition
The main arteries that supply the brain:
* R. & L. internal carotid arteries
* R. & L. vertebral arteries
* basilar artery (formed from the joining
of the R. & L. vertebrals)
* posterior cerebral arteries (from by
the division of the basilar artery)
* cerebral arterial circle (circle of
Willis)
Brain Nutrition
Anastomosis - a merging or
joining of blood vessels,
nerves or lymphatic vessels
Brain Nutrition
Brain Nutrition
Even with its oxygen and glucose needs, the brain must be
protected from antibodies, macrophages, pathogens, etc. in
the blood
The choroid plexus and brain capillaries are the two
potential points of entry
Brain Nutrition
The brain capillaries are composed of tightly joined
endothelial cells which ensure that anything leaving the
blood must pass through the cells
This arrangement is called the blood-brain barrier
Brain Nutrition
The capillaries of the choroid plexus are surrounded by
ependymal cells that have tight junctions creating a similar
barrier
The brain barrier system is highly permeable to O2, CO2,
glucose, water, nicotine, alcohol, caffeine & anesthetics
Cranial Nerves
Olfactory Nerve (I)
Sense of smell
Sensory
Cranial Nerves
Optic Nerve (II)
Sense of sight
Sensory
Cranial Nerves
Oculomotor Nerve (III)
Eye & eyelid movements, pupil
constriction, focusing
Motor
Cranial Nerves
Trochlear Nerve (IV)
Eye movements
Motor
Cranial
Nerves
Trigeminal Nerve (V)
Touch, temperature & pain
sensation of the face, mastication
Mixed
Cranial Nerves
Abducens Nerve (VI)
Lateral eye movements
Motor
Cranial Nerves
Facial Nerve (VII)
Taste, facial expressions, secretion
of tears, saliva & mucus
Mixed
Cranial Nerves
Vestibulocochlear Nerve (VIII)
Hearing and equilibrium
Sensory
Cranial
Nerves
Glossopharyngeal Nerve (IX)
Touch, taste, pressure & pain
sensation of the tongue & pinnae,
swallowing & gagging
Mixed
Cranial
Nerves
Vagus Nerve (X)
Taste, hunger,
fullness, swallowing,
speech, heart rate,
digestive secretion &
motility
Mixed
Cranial
Nerves
Accessory Nerve (XI)
Swallowing, head, neck & shoulder
movements
Motor
Cranial
Nerves
Hypoglossal Nerve (XII)
Tongue movements of speech, food
manipulation & swallowing
Motor
Brain Diseases
A stroke is an event in which blood
flow has be lost to any part of the
brain due to blockage or
hemorrhage
Brain Diseases
The interruption of blood flow
leads to necrosis of the nervous
tissue
A stroke is also known as apoplexy
or a cerebrovascular accident
(CVA)
Brain Diseases
Hydrocephalus is abnormal
accumulation of CSF in the
ventricles of the brain due to
blockage that prevents
reabsorption
Brain Diseases
Since fluids do not compress,
excessive accumulation can result
in compression and damage to
nerve tissue of the brain
It can be relieved by inserting
shunts to drain the fluid
Brain Diseases
Cerebral palsy is a condition which
results in muscular incoordination
due to damage to motor areas of
the brain
The damage is usually caused
during fetal development, birth or
in infancy
Brain Diseases
Damage can be caused by:
+ prenatal rubella infection
+ drugs
+ exposure to radiation
+ oxygen deficiency during birth
or early infancy
+ hydrocephalus
Brain Diseases
Alzheimer’s disease is associated
with acetylcholine deficiency
It onset is slow, can be ambiguous
and cannot be reversed
The brain atrophies causing
confusion, loss of memory, and
moodiness
Brain Diseases
Parkinson’s disease results in a
progressive loss of motor function
due to the degeneration of
dopamine releasing neurons
Dopamine is an inhibitory
neurotransmitter, that aids in the
control of muscle contractions
Brain Diseases
Meningitis is the inflammation of
the meninges, caused by viral or
bacterial infection
Viral forms are dangerous, but the
bacterial forms can be lethal
The brain swells, the ventricles
enlarge and the brainstem may
hemorrhage