Brain contributes to homeostasis by receiving sensory input, integrating new and stored information, makes decisions, and causes motor activities.

Brain is control center for registering sensations, correlating them with one another and with stored information, making decisions, and taking actions.

Brain is center of intellect, emotions, behavior, memory and directs our behavior toward others.

Brain is 80% of intracranial contents; other 20% is blood and cerebrospinal fluid (CSF)

100 billion neurons and 10 - 50 trillion neuroglia make up brain

Each neuron forms 1000 synapses with other neurons; total number of synapses = thousand trillion (1015)

Mass of 3 lb in adult

Brain size varies among individuals

Brains of male are on average 10% larger than females, due to differences in average body size

NO correlation with size of brain and intelligence!!!!!!!!!!

Brain stem

Brain stem

Continuous with the spinal cord

Consists of the medulla oblongata, pons and midbrain.

Posterior to brainstem

Second largest part of the brain

Diencephalon (“through brain”)

Superior to brainstem and surrounded by cerebrum

Consists primarily of thalamus and hypothalamus 

Cerebrum (“brain”)

Largest part of the brain

“Thinking cap”

1)  Cranial bones

2)  Cranial meninges (and dural folds)

3)  Cerebrospinal fluid

Only 1 in 8 cranial trauma (head injury from impact from another object) cases results in serious brain damage due to above

Blood-brain barrier

Inner layer of dura mater that extends into cranial cavity forming a sheet that dips inward and then returns

Provide additional stabilization and support to brain

Contains dural sinuses: large collecting veins that drain venous blood from brain to internal jugular veins of neck

separates two hemispheres of cerebrum 

Contains superior and inferior sagittal sinuses

separates cerebrum from cerebellum

Contains transverse sinus

Clear, colorless liquid 

80 -150 ml (3 - 5 oz.) in adult

Contains glucose, proteins, urea, ions, and some WBCs

Mechanical protection

Chemical protection

Circulation

CSF in subarachnoid space in brain and spinal cord acts as a shock-absorbing medium

Buoys the brain so it “floats” in the cranial cavity

networks of capillaries (microscopic blood vessels) in the walls of the ventricles. 

Sites of CSF production

Blood plasma is drawn from the choroid plexuses through the ependymal cells into the ventricles to produce CSF

Abnormalities in the brain such as tumors, inflammation, or developmental malformations can interfere with drainage of CSF from ventricles into the subarachnoid space

When excess CSF accumulates in the ventricles, CSF pressure rises (not good because it compresses and can damage delicate nervous tissue)

In a baby whose fontanels have not closed, the head/skull swells (there is some “give”) due to increased pressure

In adults, hydrocephalus may occur after head injury, meningitis, obstruction by tumors, etc. and quickly can become life-threatening and must be surgically treated immediately to relieve pressure since the skull bones have already fused

In an adult, the brain represents 2% of total body weight but the brain consumes 20% of oxygen and glucose used (even when body is at rest)!!!!!!!!!!

Neurons have high demand for energy and synthesize ATP almost exclusively from aerobic respiration! 

Glucose and oxygen are not stored in the brain, so supply of both must be continuous from the blood!

Low blood glucose level = mental confusion, dizziness, convulsion and possible loss of consciousness

Cerebrovascular accident (CVA) or stroke

Occurs when blood supply to portion of brain is shut off

Affected neurons die within minutes

Brief slowing of brain blood flow = unconsciousness

1 or 2 min = impairs neuronal function

4 min = permanent injury

Protects brain from harmful substances and pathogens by preventing passage of many substances from blood into brain tissue

Consists of tight junctions that seal together the endothelial cells of brain capillaries

Processes of astrocytes press up against capillaries and secrete chemicals that maintain permeability of tight junctions

Water-soluble substances such as glucose and most ions can cross BBB

Lipid-soluble substances can cross BBB more easily: O2, CO2, alcohol and most anesthetic agents

Proteins and most antibiotic drugs do NOT pass through!

Trauma and inflammation can damage BBB (leaky

Continuous with superior part of spinal cord

Forms inferior part of brainstem

Begins at foramen magnum and ends at inferior border of pons

Contains ascending (sensory) and descending (motor) tracts (continuation of spinal cord tracts)

At junction of medulla oblongata with spinal cord, pyramids (corticospinal (motor) tracts) cross over (left to right or right to left)

This is why each side of the brain controls voluntary movements on the opposite side of the body!!!!!!!!

cross over (left to right or right to left)

This is why each side of the brain controls voluntary movements on the opposite side of the body!!!!!!!!

 part of the respiratory center that adjusts basic rhythm of breathing

Injuries to the back of the head or upper neck that injure the medulla can be fatal especially if respiratory center is damaged

Alcohol overdose also suppresses respiratory center and may result in death

Vomiting, swallowing, sneezing, coughing and hiccupping

Superior to medulla and anterior to cerebellum

Links cerebellum to brain stem, cerebrum, and spinal cord

Contains sensory and motor tracts

Contains nuclei: pneumotaxic area and apneustic area of the respiratory center that along with medullary rhythmicity area in medulla helps to control breathing

Superior to pons and inferior to diencephalon

Contains nuclei and sensory and motor tracts

Contains cerebral aqueduct, CSF-filled channel, which connects the third and fourth ventricles

“Headquarters” of the reticular activating system “RAS”  

Contains colliculi (“little hills”): four rounded elevations on posterior side

coordinate reflex movements of the head, eyes, and trunk in response to visual stimuli

Tracking moving images (watching a moving car) and scanning stationary images (reading a book

coordinate movements of the head, eyes, and trunk in response to auditory stimuli

Startle reflex: sudden movement of head, eyes, and trunk when you are surprised by a loud noise

Mixture of gray & white matter that extends from upper part of spinal cord, throughout brain stem, and into lower part of diencephalon; includes the RAS

Involved in awakening from sleep (arousal) and maintaining consciousness

Alerts cerebral cortex to incoming sensory input from eyes, ears and skin (but not nose!)

Bright light, touch/pressure on skin, sound of alarm clock

No RAS activity → low cerebral cortex activity = sleep

Activation of RAS → high cerebral cortex activity = arousal/wakefulness

Occupies inferior and posterior part of cranial cavity

Makes up 1/10 of brain mass but has ½ of neurons in brain!

In superior or inferior views, divided into two cerebellar hemispheres

Contains cerebellar cortex: outer layer of gray matter

Contains arbor vitae (“tree of life”): deeper white matter

Smoothes and coordinates contractions of skeletal muscles esp. for complex movements (dancing, gymnastics, speaking, etc.)

Regulates posture and balance (equilibrium)

disruption of muscle coordination caused by damage through trauma or disease to cerebellum

May result in staggering or abnormal walking movements; changed speech pattern

Too much alcohol inhibits activity of cerebellum – will show signs of ataxia, e.g. slurred speech, staggering, can’t touch nose with finger if eyes closed

Thalamus

Makes up 80% of diencephalon

Consists of paired masses of gray matter lateral to upper part of 3rd ventricle; contains several nuclei

Final relay point and filter for most sensory impulses (except olfaction) from brain stem and spinal cord to cerebral cortex 

Axons of sensory neurons form synapses on dendrites and cell bodies of thalamic neurons, which in turn send their axons to the appropriate part of the cerebral cortex

Inferior to the thalamus

Composed of dozen or so nuclei in four major regions

Contains suprachiasmatic nucleus: 

Lies superior to optic chiasm (point of crossing of optic nerves)

Receives input from retina of eye

Serves as body’s internal biological clock and establishes circadian rhythms: patterns of biological activity e.g. sleep-wake cycle that occurs in a cycle of 24 hours

Major regulator of homeostasis in body  - it is part of the nervous system and endocrine system!!!!!!

Controls and integrates many visceral activities (e.g. contraction of smooth and cardiac muscle, secretion of glands) via autonomic nervous system

Produces hormones and regulates endocrine activities via pituitary gland

Involved (as part of limbic system) in emotional and behavioral patterns (rage, pleasure, pain, aggression, sexual arousal)

Regulates body temperature

Regulates food intake (feeding and satiety centers)

Regulates fluid intake (thirst center)

Regulates circadian rhythms

Small region inferior and posterior to thalamus

Contains pineal gland which is the size of a pea and is part of the endocrine system

Secretes hormone melatonin (synthesized from serotonin)  which contributes to setting of circadian rhythms

Visual input from eyes (retina)→stimulates suprachiasmatic nucleus of hypothalamus→stimulates pineal gland secretion of melatonin 

Darkness/night = increase in melatonin secretion = sleepiness

Light/day = decrease in melatonin secretion = awake

SAD (seasonal affective disorder): type of depression that affects people in winter months, when day length is short

May be due to oversecretion of melatonin

Use full-spectrum bright light therapy upon arising

Secretes hormone melatonin (synthesized from serotonin)  which contributes to setting of circadian rhythms

Visual input from eyes (retina)→stimulates suprachiasmatic nucleus of hypothalamus→stimulates pineal gland secretion of melatonin 

Darkness/night = increase in melatonin secretion = sleepiness

Light/day = decrease in melatonin secretion = awake

SAD (seasonal affective disorder): type of depression that affects people in winter months, when day length is short

May be due to oversecretion of melatonin

Use full-spectrum bright light therapy upon arising

Seat of intelligence”

Divided by longitudinal fissure into left and right cerebral hemispheres

Contains cerebral cortex: outer layer of gray matter 

Few mm thick; contains billions of neurons 

Rolls and folds upon itself

Each fold or convolution is called a gyrus (sing.); gyri (pl.)

Deepest grooves between folds = fissures

Shallower grooves between folds = sulci (pl.); sulcus (sing.)

Gray matter extends into sulci so the total area of cerebral cortex is much greater than is apparent on surface

Contains cerebral white matter: deep to the corte

Contains primary motor area of cerebral cortex

Contains primary somatosensory area of cerebral cortex

Each hemisphere is divided into four lobes and are named after the bones that cover them: frontal lobe, parietal lobe, temporal lobe and occipital lobe.

descending and ascending tracts between cerebrum and lower parts of CNS (thalamus, brain stem, cerebellum or spinal cord)

Ascending tract (example): thalamus to cerebral cortex

Descending tract (example): corticospinal tract

Three nuclei (masses of gray matter) deep within each cerebral hemisphere near the thalamus.

Involved with subconscious control of skeletal muscle tone and coordination of learned movement patterns.

Provide pattern and rhythm for moving trunk and proximal limb muscles

Influences many aspects of cortical function including sensory, limbic, cognitive, and linguistic functions.

Disorders of basal ganglia can affect body movements, cognition, and behavior.

Basal nuclei inhibited by dopamine-secreting neurons in substantia nigra of midbrain

Damage to substantia nigra = more active basal nuclei

Progressive disorder of the CNS that typically affects its victims around age 60 (can strike at younger age)

Neurons that extend from substantia nigra of midbrain to the basal nuclei and release dopamine degenerate.

Symptoms include uncontrollable shaking (tremors) and muscle rigidity (stiffness)

Cause is unknown but toxic environmental chemicals such as pesticides, herbicides, and carbon monoxide are suspects

Boxers are at higher risk due to repeated blows to the head.

So far, no treatments can cure or slow course of PD

Levodopa (precursor of dopamine) – works for short time

Surgery

Neural stem cells/tissue

Not an anatomical structure

Functional grouping of nuclei and tracts between cerebrum and diencephalon

Functions:

1)  “Emotional brain” as it governs emotional aspects of behavior such as pleasure, pain, docility, affection, fear, and anger

Plays a role in the drive or motivation of why you do something 

2)  Links conscious, intellectual functions of cerebral cortex with unconscious and autonomic functions of brainstem

3)  Facilitates memory storage and retrieval

receive sensory information that has been relayed from peripheral sensory receptors through lower regions of the brain

Involved in perception, the conscious awareness of a sensation

Primary somatosensory area: postcentral gyrus of parietal lobe

Receives nerve impulses for touch, pressure, vibration, itch, tickle, taste, temperature, pain, and proprioception (joint and muscle position) and is involved in perception of these somatic sensations

Allows you to “pinpoint” where somatic sensations originate e.g. so you know where on your body to swat that mosquito

Receives visual information; involved in visual perception

Primary auditory area: temporal lobe

Receives information for sound; involved in auditory perception

Primary olfactory area:  temporal lobe

On medial aspect of temporal lobe (can’t see in picture)

Receives impulses for smell via olfactory nerve and is involved in olfactory perception

Primary gustatory area: parietal lobe

At base of postcentral gyrus

Receives impulses for taste and is involved in gustatory perception and taste discrimination

Primary motor area: precentral gyrus of frontal lobe

Each region controls voluntary contractions of specific muscles or groups of muscles

Electrical stimulation of any point in primary motor area causes contraction of specific skeletal muscles fibers on opposite side of body

Broca’s speech area: frontal lobe

Involved in articulation of speech

Localized in left cerebral hemisphere of most people

Neural circuits established between Broca’s speech area, premotor area and primary motor area activate muscles of larynx, pharynx, mouth, and breathing muscles to enable to speak your thoughts

People who have brain damage in this area can have clear thoughts but cannot form words – aphasia (non-fluent)

Somatosensory association area: posterior to and receives input from primary somatosensory area

Allows you to determine exact shape and texture of an object by feeling it

Stores memories of past somatic experiences – so you can recognize objects such as a pencil simply by touching it

Receives sensory impulses from primary visual area and thalamus

Essential for recognizing and evaluating what is seen – so you can recognize a spoon simply by looking at it

Auditory association area: temporal lobe

Allows you to recognize a particular sound as speech, music, or noise

Wernicke’s area: left temporal and parietal lobes

Interprets the meaning of speech by recognizing spoken words

It is active as you translate words into thoughts

People with brain damage in Wernicke’s area can still speak but cannot arrange words in a coherent fashion (fluent aphasia or “word salad”)

Prefrontal cortex: anterior portion of frontal lobe

Well-developed in primates, especially humans

Numerous connections with other areas of cerebral cortex, thalamus, hypothalamus, limbic system, and cerebellum

Make-up of person’s personality, intellect, complex learning abilities, recall of information, reasoning, mood, planning for the future, development of abstract ideas, initiative, judgment

A person with bilateral damage to pre-frontal cortex has personality changes and typically becomes:  rude, inattentive, moody, less creative, cannot plan for the future, cannot anticipate consequences of rash or reckless words or behavior, etc.

The brain is almost symmetrical on its right and left sides

However subtle anatomical differences between the two hemispheres do exist

Both cerebral hemispheres share the performance of many physiological functions

However, each hemisphere also specializes in performing certain unique functions = hemispheric lateralization

12 pairs; part of PNS

Each cranial nerve has a name & roman numeral number

Numbers indicate order, from anterior to posterior, in which the nerves arise from the brain

Name designates a nerve’s distribution or function

Involved with sensory and motor functions of head and neck region (Exception: vagus (X) nerve!!!!!)

Cranial nerves are either sensory, motor or mixed nerves (contains axons of both sensory and motor neurons)

Cell bodies of sensory neurons are located in ganglia outside of brain

Cell bodies of motor neurons lie in nuclei within th

Olfactory (I) Nerve

Sensory nerve

Sense of smell (olfaction)

Olfactory (I) Nerve

Sensory nerve

Nerve of vision 

Ganglion cells in the retina of each eye join to form an optic nerve, which passes through optic foramen of sphenoid bone, forms the optic chiasm, and then optic tracts; terminates in the thalamus.

From thalamus, axons extend to primary visual area (in occipital lobes) of cerebral cortex 

Motor nerve

Originates in the midbrain

Controls extrinsic eye muscles to move the upper eyelid (levator palpebrae superioris) and eyeball (superior, inferior, and medial rectus, and inferior oblique) 

Motor nerve 

Smallest of the 12 cranial nerves

Originates in the midbrain

Controls extrinsic eye muscle (superior oblique) that moves the eyeball down and to the side

Abducens (VI) Nerve

Motor nerve

Originates from pons & innervates lateral rectus muscle

Causes abduction of the eyeball (lateral rotation)

Largest cranial nerve

Mixed nerve

Has three branches: ophthalmic, maxillary and mandibular

Sensory portion: ends at pons; deals with sensation of touch, pain and temperature over face, anterior scalp and teeth

Motor portion: originates from pons; motor axons of mandibular branch supply muscles of mastication (chewing) e.g. temporalis, masseter

Dental work:

For anesthesia of upper teeth – apply drugs to branches of maxillary nerve

For anesthesia of lower teeth - apply drugs to branches of mandibular nerve

Mixed nerve

Sensory portion extends from the taste buds of the anterior two-thirds of the tongue

Sensory function: taste

Motor portion arises from pons 

Motor function:  innervates muscles for facial expression e.g. zygomaticus major

Originates in the inner ear and ends in the brain

Two branches:

Vestibular branch: carries impulses for equilibrium

Cochlear branch: carries impulses for hearing

Mixed cranial nerve

Sensory axons carry signals from taste buds of posterior one-third of the tongue

Sensory function: Taste and somatic sensations (touch, pain, temperature) from posterior one-third of tongue

Motor neurons arise from the medulla and innervate a muscle in pharynx

Motor function: elevates the pharynx during swallowing and speech

Mixed cranial nerve

Widely distributed from head, neck, thorax and abdomen

Sensory axons originate and deal with sensations from most visceral organs of the thoracic and abdominal cavities; ends in medulla and pons

Motor neurons arise from medulla and supply muscles in throat and neck involved in swallowing, coughing and vocalization

Motor (autonomic/parasympathetic) neurons arise from medulla and innervate visceral organs of thoracic cavity (heart, lungs, esophagus) and abdominal cavity (stomach, pancreas, liver, small and large intestines)

Involved in smooth muscle contraction & relaxation in organs of GI tract; slowing of heart rate; secretion of digestive fluids

Motor nerve

Motor axons arise in anterior gray horn of first five segments of cervical portion of spinal cord

Innervates sternocleidomastoid and trapezius muscles to coordinate head movements

Motor nerve

Originates in medulla and innervates muscles of the tongue

Motor function: movement of tongue for speech and swallowing

Responsible for “Sticking out your tongue”

Anatomical and physiological changes begin by age 30 and accumulate over time

Reduction in brain size and weight

Reduction in number of neurons and synapses

Decrease in blood flow to brain

Increase in neurofibrillary tangles (masses of neurofibrils inside cell body and axon of neurons) and plaques (extracellular accumulation of fibrillar proteins)

Hearing, balance, vision, smell, and taste become less sensitive

Reaction rates, reflexes, and precision of motor control is slowed

Memories of recent past more difficult to make

Anatomical and physiological changes begin by age 30 and accumulate over time

Reduction in brain size and weight

Reduction in number of neurons and synapses

Decrease in blood flow to brain

Increase in neurofibrillary tangles (masses of neurofibrils inside cell body and axon of neurons) and plaques (extracellular accumulation of fibrillar proteins)

Hearing, balance, vision, smell, and taste become less sensitive

Reaction rates, reflexes, and precision of motor control is slowed

Memories of recent past more difficult to make

Degenerative CNS changes including memory loss, anterograde amnesia (can’t remember recent past), and emotional disturbances

Alzheimer’s disease (AD) is most common form of senility

Progressive disorder of loss of higher-order cerebral function

Symptoms appear at 50 – 60 years or later

Neurofibrillary tangles and abnormal plaques are found in areas of brain associated with memory, emotion, and intellectual function (cause or secondary effect?)

Genetic factors play a role, but inflammation (from diet & other environmental factors plays a bigger role)

NO CURE!!!!

Vitamin B-12 (made by bacteria!)

Sublingual methylcobalamin (500 ug/day) 

Bloodwork (serum B-12, methylmalonic acid, and homocysteine)

Vitamin D 

Sunlight and/or supplement (2000 IU/day for adult)

Bloodwork (25-hydroxy (OH) vitamin D) (aim for 35-55 ng/ml)

Essential Fatty Acids (docoshexaenoic acid (DHA), eicospentaenoic acid (EPA)

Food sources (DHA & EPA – fish); DHA (egg yolks)

Alpha-linolenic acid (precursor to DHA) found in walnuts, flax and hemp seeds, & some dark green leafy vegetables

DHA/EPA supplement: get from algae (that’s where the fish get it from)

Whole food plant-based diet (Anti-inflammatory)

Diet high in vegetables, fruits, beans, fat source (raw nuts and seeds: pumpkin, sunflower, chia, hemp, sesame, flax), avocados), whole grains (brown and black rice, wild rice, quinoa, amaranth, teff, millet, buckwheat, oats)

GOMBBS (Joel Fuhrman, M.D., “Eat to Live”) Greens (leafy vegetables), Onions (and Garlic), Mushrooms, Beans, Berries, Seeds (and Nuts) 

Minimize animal products, processed or refined foods (manufactured food in bags, cans, bottles, etc.), salt, sugar, oils 

These foods promotes inflammation!!!!!

Poor foods = poor moods!

Exercise every day!

Aerobic especially, but include strength and weight training, and stretching exercises (Pilates, yoga, Tai Chi)

A review of more than 100 studies, published in the Journal of Applied Physiology (2012), revealed that both aerobic and resistance/strength training are important for maintaining cognitive and brain health in old age.

Exercise increases gray and white matter and blood flow to the brain, growth in hippocampus region, stimulates neural stem cells to become neurons, strengthens interconnections between neurons, and protects them from damage

Aim to be lean and muscular

Be a lifelong learner or student 

Learn a new language, skill, or musical instrument and do thinking activities (crossword puzzles, card games, etc.) 

Be a lifelong socializer: Create healthy relationships with family, friends, colleagues, community

Sleep: 7 – 9 hours/night

Meditation

Studies have found brains of long-term meditators were larger, contained more gray matter, had stronger neuronal connections between brain regions, and less age-related brain atrophy

Don’t smoke

Minimize or don’t drink alcohol