the adult brain is composed of
100 billion neurons and 1000 billion neuroglia
the brain consists of _____ major parts
four
parts of the brain
1. brain stem (control center)
2. diencephalon
3. cerebrum
4. cerebellum
the brain accounts for ____% of body weight
2
how long can neurons be deprived of oxygen before there is brain damage?
4 minutes
what protects the brain?
1. cranium
2. meninges (three membranes that surround brain and spinal cord)
3. cerebrospinal fluid
meninges
1. dura mater
2. arachnoid
3. pia mater
dura mater
tough fibrous membrane
arachnoid
middle membrane. Contains CSF.
pia mater
inner delicate membrane, cradles brain.
what is between the skull and duramater
epidural space
what is between duramater and arachnoid space?
subdural space
the area between the arachnoid and pia mater is called...
subarachnoid space
contains CSF
CSF
produced by choroid plexes
choroid plexes
ependymal cells, supportive tissue, and associated blood vessels
contains glucose, proteins, ions, WBCs
what are the duties of the CSF?
1. deliver nutrients to brain and remove waste
2. allow brain to float in cranium
3. shock absorber
choroid plexus is located in
ventricles
ependymal cells
line CSF circulatory pathway and help with movement
Arachnoid Villi
finger like extentions of the arachnoid that pass the CSF back into the blood through the superior sagittal sinus
hydrocephalus
CSF pathway is blocked due to tumor or inflammation
can result in expansion and brain damage
Treat with shunt
Blood supply of the brain...
trace path
circle of willis
at base of brain
branches of internal carotid artery and vertebral artery join to form
what can pass rapidly from blood into brain cells?
glucose, O2, CO2, water, and most lipid soluble substances like alcohol, caffeine, nicotine, anesthesia, and heroin
Blood Brain Barrier
prevents substances from entering brain. Formed by capillaries that are less permeable than others. Endothelial cells are tight. Astrocytes selectively pass substances
what can't pass the BBB?
proteins and many antibiotics
what areas lack BBB
3rd and 4th ventricles
HIV and meningitis get into brain here b/c there is no tight junction
brain stem
medulla oblongata
pons
midbrain (cerebral peduncles, corpora quadrigemina, nuclei)
medulla oblongata
continuation of spinal cord forming the inferior portion of the brain stem. all ascending tracts (sensory) and decending tracts (motor) connect the spinal cord and brain
the medulla oblongata is where ______ of the tracts occur
decussation
crosses over from right to left and vice versa to allow for contralateral control of the body
the medulla oblongata (m.o.) is involved with ________ functions
involuntary
gray matter
contains nuclei
pyramids on m.o. contain
descending nerve tracts
loives
protrude from anterior surface of nerve tracts on m.o.
contain nuclei of cranial nerves V, IX-XII
regulate balance, coordination, and modulation of the sound from the inner ear
involuntary controls of the m.o.
1. cardiovascular center (regulates force and diameter of vessels)
2. medullary rhythmicity center (adjusts rhythm of breathing)
3. vomiting, coughing, sneezing, hiccuping center
pons means
bridge
pons
area that connects medulla to other portions of the brain as well as connecting cerebrum to cerebellum. Composed of ascending and descending tracts
the pons is the ______ and ______ center
sleep/respiratory
midbrain
contains cerebral peduncles, corpora quadragemina, and nuclei
cerebral peduncles
descending fiber tracts which are motor tracts
corpora quadragemina
four bodies on posterior side of brain
2 superior coliculi and 2 inferior coliculi
superior coliculi
involved with reflex movement of eyes, head, and neck in response to visual stimuli
inferior coliculi
involved with reflex movment of head in response to auditory stimuli
nuclei
red and substantia nigra
red nuclei
involved with unconscious regulation and coordination of motor activityes
substantial nigra
involved with maintaining muscle tone and coordination movments
major pathology associated with nuclei
parkinsons
what occurs with parkinsons
tremor of extremities and head, rigidity of muscle
dopamine is inhibitory neurotransmitter that is produced by substantia nigra and decreases with parkinsons because nuclei degenerate
how do we treat parkinsons?
administer precursor of dopamine: L dopa
why don't we administer dopamine to treat parkinsons?
it can't pass the BBB
L dopa can, and then it converts to dopamine by the CNS neurons
diencephalon
areas surrounding third ventricle
includes thalamus and hypothalamus as well as pineal gland
thalamus
principal relay area for sensory input going to cerebral cortex for interpretation
Important in learning awareness and emotions like fear, rage, mood
hypothalamus
maintains homeostasis
centers deal with rage, aggression, thirst, hunger, temperature, pleasure, fullness
pineal gland
size of a pea
secretes melatonin
the pineal gland is a/an __________ gland
endocrine
the pineal gland is involved with
the wake and sleep cycle and possibly the onset of puberty
cerebellum
lower posterior of brain
lateral hemispheres
contains flocculonodular lobes and vermis
flocculonodular lobes
balance and eye movement
lobes are connected by vermis
vermis
area in the center that resembles a worm.
arbor vitae
Resembles a tree
arrangement of white and gray matter
involved with balancing and receives input from receptors in muscles, tendons, joints, and eyes
injury to cerebellum results in...
clumsy, disorganized movement
signs of cerebellar disease
intention tremors, dysdiadochokinesia, nystagamus, dysarthria, ataxia
cerebrum
composes most of brain
two hemispheres connected by fiber tracts.
contains gyri and sulcus
largest fiber tract is called
corpus callosum
gyri
increases surface area of brain to allow for more space for neurons
only found in higher animals
sulcus
increases surface area of brain to allow for more space for neurons
only found in higher animals
the cerebrum is mostly _____ matter with thin layer of ______ matter on the surface
white/grey
cerebral cortex
contains billions of unmyelinated neurons that are associated with a higher thinking an performance (reading and speaking)
the cerebrum can be anatomically divided into ____ different lobes
five
lobes of cerebrum
1. frontal (knowledge-when you protect your head with your hands you instinctively protect this portion of your brain!)
2. parietal (sensory center)
3. temporal (auditory center)
4. occipital (vision center)
5. insula (internal) inside temporal
limbic system
includes amygdala and hippocampus which are involved with memory, reproduction, nutrition, survival instinct
basal ganglia
composed of caudate, lentiform, subthalamic and substantia nigra nuclei
involved in action selection, reinforcement, and reward learning
the most widely studied part of the brain by neurologists and neuroscienists is the...
basal ganglia
the limbic system and basal ganglia are ____ ______ entities
two different
cerebral fissure
separates cerebrum longetudinally
central sulcus
divides brain into anterior (motor) and posterior (sensory)
lateral fissure
divides frontal and parietal from temporal and occipital lobes
cranial nerves
there are 12 pairs that arise from the base of the brain and innervate the facial region
some are sensory or motor and others are mixed (both)
nervous system is involved with most body functions and receives _____ input through _____ in the ______
sensory/receptors/PNS
sensory input from PNS travel through _____ neurons to the _____
sensory/CNS
sensory input is then processed in the CNS at the _____ ____ and/or _____ level
spinal cord/brain
motor outflow
originate in the CNS
taken by motor neuronsto the PNS
sensory input stimultes
reasoning, memory, planning, emotional response
sensation
conscious awareness of stimuli received by sensory receptors
received from external and internal receptors in PNS
sensory receptors generate ____ _____ when stimulated that will travel along neurons to the _____
action potential/CNS
types of sensory receptors
1. mechanoreceptors
2. chemoreceptors
3. thermoreceptors
4. photoreceptors
5. nocioceptors
mechanoreceptors
respond to mechanical stimuli such as compression, bending, stretching
Ex. merkel's disks: superficial touch and pressure
Ex. Pacinian: deep pressure
chemoreceptors
respond to chemical molecules that become attached to receptors on membranes
ex. smell McDonalds nearby
thermoreceptros
respond to changes in temperature
photoreceptors
respond to light
nocioceptors
pain receptors:
respond to overstimulation (and sometimes understimulation) of mechanical, chemical, thermal, or light stimuli
work with others to maintain homeostasis
The only sensory receptor that can respond to more than one type of stimulus is ________
Nocioceptors
types of recpetors based on location
three thpes:
exteroreceptors
viceroreceptors
proprioceptors
exteroreceptors
associated with skin
outside of body: hair and skin
viceroreceptors
associated with organs
refer pain to different location
proprioceptors
associated with joints and tendons
ex. golgi tendon organ associated with a tendon and these receptors respond to increased tension on it
response to a sensory receptor
interaction of a sensory receptor with its specific sensory stimulus will cause the receptor to establish an action potential. AP travels along sensory neurons toward CNS
CNS interprets the sensory stimulus and a motor response is produced
accomodation
decrease in sensitivty to a stimulus
ex. jump in pool and your thermoreceptors eventually stop telling you it's too cold because you have adjusted to the stimulus
what is the only sensory receptor that doesn't accomodate?
nocioreceptors
sensory nerve tract
pathways that go from spinal cord to the brain, carrying specific information
names indicate where they begin and end
spinothalamic tract
begins at different levels inside the spinal cord. AP that enter this tract will go to the thalamus. Neurons will synapse and the information will be taken to the cortex for interpretation
anterior spinothalamic tract
LST: carries info regarding pain and temperature
AST: carries info regarding light touch, tickle, itching
tracts involve four neuron sequence from PNS receptors to cortex
Decussation occurs at the _______ tracts, meaning sensation is found on the opposite side of the body
spinothalamic tract
two point discrimination test
pins on different areas of body and tell where they are
if wrong, could be nervous system problems
sensory areas of the cerebral cortex
from the thalamus the sensory AP goes through sensory pathways to primary sensory areas located in postcentral gyrus
homunculus
organized: each sensation has a specific place in the brain
mechanoreceptors=touch receptors
what are the types of touch receptors?
1. meissners corpuscles
2. pacinian corpuscles
3. merkels disks
4. hair follicle receptors
meissners corpuscles
dendrites in connective tissue in dermal papillae of skin
concentrated in fingertips, tongue, soles of feet
help determine texture of objects
respond to SOFT DEEP TOUCH
Fast adaptation
pacinian corpuscles
oval, composed of dendrites in connective tissue
deep in subcutaneous layer under dermis
respond to DEEP PRESSURED TOUCH
fast adaptation
merkels disks
detect LIGHT SUPERFICIAL TOUCH and PRESSURE
located superficially in epidermis
Hair follicle receptors
respond to LIGHT TOUCH
extremely sensitive
thermal receptor
free nerve endings in skin
separate for hot vs. cold
fast adaptation
pain receptors
two kinds:
1. somatic: from receptors in skin, skeletal muscle, joints, tendons. Easily placed where pain and injury are.
2. visceral: results from receptors in viscera. Referred pain makes finding actual source of pain hard. Ex. heart attack
phantom pain
amputees
neuron pathway that carried AP still present carry AP to cerebral cortex and is interpreted as originating in the lost limb.
Spontaneously occurring after surgery by fade with time.
taste area
inferior end of postcentral gyrus
receives info from tongue
olfaction
inferior frontal lobe
auditory
superior temporal lobe
visual
occipital lobe
two sensory areas in cortex
primary and association
primary sensory area
perception, identification of stimulus and localization
association sensory areas
Rely on former experiences with stimulus and pass judgement important or can it be ignored
ex. face in crowd
motor areas of cerebral cortex
1. precentral gyrus in primary motor cortex
2. premotor area
3. motor tracts
4. motor neurons
the motor areas control...
control effector organs
ex. muscles, tendons, joints, glands, organs
precentral gyrus
primary motor cortex
AP coming from this area of the brain will control many voluntary movements
influence from premotor area of brain offers organization to movement
premotor area is present in the ____ of the ____ _____
front/precentral gyrus
responsible for organization of movement
apraxia
difficulty or hesitncy in movement
pathology of precentral gyrus
what are the two types of motor nerves?
1. upper motor neuron: connects cerebrum to lower motor neuron (brain stem or spinal cord)
2. lower motor neuron (runs from brain stem or spinal cord to the skeletal muscles through the PNS)
broca's area
motor speech area located in inferior part of frontal lobe and is in charge of complex movements of mouth and throat necessary for speech to occur.
wernicke's area
sensory speech area in nearby parietal lobe that is responsible for understanding and formulating speech
aphasia
absence or defective speech
lesion in speech cortex
prefrontal
cerebral cortex
most anterior portion of the frontal lobe
appears where much of the personality is
qualities such as motivation, intelligence, abstract ideas, judgement, empathy, conscience
leison changes personalithy
electroencephalogram (EEG)
there is electrical activity in skeletal muscle, nerves, heart, and brain
records electrical activity in the brain. AP sensed by electrodes placed on the scalp and brain waves are generated
aging of the nervous system
as we age there is a decline in sensory and motor function
size and weigh of the brain is decreased that leads to slower reflexes, decrease in short term memory and changes in sleep patterns
long term memory is not affected and is actually improved
alzheimer's disease
mental deterioration. Loss of number of acetylcholine neurons resulting in decrease in size of brain and collections of granular structures (amyloid plaques) on the cortex
decreases intelligence, memory, and mood changes seen
left hemisphere
important for speech, written language, numerical and scientific skills and reasoning
right hemisphere
more important for musical and artistic awareness, space perception, insight, analytical, and imagination
usually one hemisphere will _____ and will lead to right or left handedness
dominate
can you have a brain without a dominate side?
Yes. But it causes learning problems.
Cerebrovascular accident (CVA/Stroke)
neurons of a portion of the brain will die due to lack of blood flow and therefore lack of oxygen to that area.
Caused by blockage within vessels going to the area (thrombosis or embolism) or a hemorrhage
infarct
death of cells due to lack of blood supply
symptoms: paralysis of side of body, opposite the cerebral infarct
is there prevention for clots?
Yes: a daily dose of aspirin may decrease risk of developing clots in blood
concussion
slight milk brain injury
bleeding and tearing of verve fibers
recovery likely with some memory loss
contusion
more severe TBI
nervous tissue destruction (doesn't regenerate)
cerebral edema
swelling from inflammatory response
may compress and kill brain tissue
subdural hematomoa
blood beneath dural space
CVA
stroke
ruptured blood vessel
damages tissue
alzheimers disease
progressive degenerative brain disease: microglial cells
abnormal protein deposits and twisted fibers within neurons
memory loss, irritability, confusion, hallucinations, and death