Brain Facts

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Brain Facts

• The adult human brain weighs about 3 pounds
  (1,300-1,400 g).
• The adult human brain is about 2 of the total
  body weight.
• The elephant brain weighs about 6,000 g.
• The cat brain weighs about 30 g.
• The human brain has about 100,000,000,000 (100
  billion) neurons.
• The octopus brain has about 300 million neurons.
• The total surface area of the cerebral cortex is
  about 2500 sq. cm (2.5 ft2)
• The world record for time without sleep is 264
  hours (11 days) by Randy Gardner in 1965
• The record for time awake is attributed to Mrs.
  Maureen Weston. She apparently spent 449 hours
  (18 days, 17 hours) awake in a rocking chair.

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• Nervous System
• Includes
• Brain
• Spinal Cord
• Nerves

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Nerve Cells

• Neurons _____billion
• Glia ________ nerve cells ____ billion
• Astrocytes
• Microglia
• Ependymal cells
• Oligodendrocytes
• Schwann cells

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Nerve Cells Glia
Lines fluid cavities in brain
In brain
Supports PNS nerves unmyelinated
Forms myelin sheath around CNS nerves
Around peripheral nerve myelinated
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Nerve Cells Neurons

• Dendrites
• carries impulse to _____ _________
• axon
• carries impulse to _______ extends the whole
  distance to the organ that it supplies
• cell body
• has nucleus
• usually located in brain or spinal cord
• neurolemma
• thin membrane around axon
• functions in _______________
• of neuron
• brain and spinal cord
• have no neurolemma therefore
• damage is permanent

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• Myelin Sheath
• ____________ the neuron
• fatty covering formed by ___________ cells
• Nodes of Ranvier
• gap between Schwann cells
• serves as points along the neuron for generating
  a _________
• signals jumping from node to node travel hundreds
  of times _________ than signals traveling along
  the surface of the axon.
• allows your brain to communicate with your toes
  in a few thousandths of a second.
• Insulation permits the nervous system to exercise
  _______ control over muscles.
• The reason that babies cannot smile or move
  precisely at birth is that the insulation for
  their nerve fibers is not completely developed.
  As the insulation does develop in a child, they
  can smile and move with greater coordination and
  precision.

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• _______________ ________________
• deterioration of myelin sheath
• slows down or blocks messages between your brain
  and your body
• involves glia and not neurons

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Structural Classification of Neurons
____polar
_____polar
_______polar
Sensory neurons
Sensory neurons
Majority of neurons Interneurons or motor neurons
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Types of neurons

• Sensory (afferent)
• Receives stimulus and sends info to brain
• Unipolar and bipolar
• Motor (efferent)
• Carries signal from brain to effector muscles
• multipolar
• Interneuron

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Synaptic Transmission

• ____________ Synapse ____________
  Synapse

Synaptic knob Synaptic cleft Plasma
membrane Neurotransmitter
Gap junctions Cardiac cells, some smooth muscle
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• Membrane Potential difference in electrical
  charge across the plasma membrane
• Resting MP - Only Na slowly diffusing through
  channels no action potential yet
• -70mV

Na/K Pump

• Active Transport
• Embedded in plasma membrane
• Pumps Na _____ ___ the cell (neuron)
• Pumps K ______ the cell (neuron)
• Ratio is uneven 3Na2K
• Need to keep a slight imbalance in order to
  maintain resting potential

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Action Potential
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Chemical Synapse

1. Synaptic knob receives action potential, and Ca2
   channels open to allow extracellular Ca2 to
   diffuse into presynaptic cell
2. Ca2 triggers exocytosis of neurotransmitters
   from the vesicles in the knob
3. Neurotransmitters diffuse into synaptic cleft and
   bind to receptor molecules in membrane of
   postsynaptic neuron causing Na and K gates to
   open and create local potential
4. Local potential moves towards axon where action
   potential begins

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Mechanisms To Produce Action Potential

• Resting Potential (-____ mV)
• 2. Stimulus triggers Na channels to open
  and allow Na into cell (Depolarization)
• 3. As threshold potential (-____mV) is
  reached, more Na influx, membrane depolarized
  more
• 4. At action potential peak, Na gates close
  (____ mV)
• 5. K gates open, K diffuses out
  (Repolarization)
• Brief period of hyperpolarization
• (too much K outflow), membrane potential is
  restored with ions in resting position

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Refractory Period

• Brief period where membrane resists stimulation
• 0.5 ms after threshold, will not respond to
  stimuli

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Threshold and All-or-None

• Threshold - stimulus must have a certain minimum
  intensity to cause a neuron to fire
• smaller, or weaker, stimuli do not provoke a
  response
• the stimulus causes channels to open and there
  must be enough of them opened to depolarize the
  membrane
• increasing a stimulus above threshold does not
  result in a larger response - this is
  all-or-nothing.
• If all stimuli above threshold cause a neuron to
  fire, how do we detect different intensities of
  stimuli?
• temporal summation - frequency of stimulation - a
  neuron fires more or less often. A warm object
  sends less frequent impulses to the brain
• spatial summation - area of stimulation - more
  neurons fire
• different thresholds - not all neurons have the
  same threshold. A warm object may trigger only a
  few neurons while a hot object provides a
  stimulus above the threshold of more neurons,
  causing them to fire

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Neurotransmitters

• More than __ known neurotransmitters
• Classified by function and chemical structure
• Excitatory vs. inhibitory
• Function determined by postsynaptic receptors
• Types
• Acetylcholine (Ach)
• Amines
• Neuropeptides

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Neurotransmitters Classification
Direct Stimulation Second
Messenger Stimulation
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NeurotransmittersACh

• Acetylcholine is its own class
• Synthesized from acetate and choline
• Junctions with motor effectors
• Muscles, glands
• Found in many parts of the brain
• Excitatory or inhibitory
• Involved in __________
• _______ Ach at NM junction causes Myasthenia
  Gravis
• Without this transmitter nerves cannot make
  muscles contract and do work
• muscular weakness.

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NeurotransmittersAmines

• Synthesized from _______ ___________
• Found in various regions of brain
• Affect __________, ___________, motor control
• Neurotransmitters
• Serotonin
• Histamine
• Catecholamines
• Dopamine
• Epinephrine
• Norepinephrine

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NeurotransmittersAminesSerotonin

• Mostly _____________
• Involved in mood, emotions, sleep
• ____seratonin causes depression or anxiety
• mood disorder serotonin and or norepinephrine.
• Antidepressant/antianxiety drugs (SSRIs) such as
  Effexor, Prozac, and Zoloft make more of these
  neurotransmitters available to the brain.
• LSD binds to serotonin receptors and blocks the
  inhibitory effect which leads to hallucinations
  (acid trip)

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NeurotransmittersAminesDopamine

• Mostly __________
• Emotions, body temp regulation, water balance
• _____ dopamine ( norepinephrine) in ADHD
• _____ dopamine has been linked to Parkinson's
  disease
• NM junction transmission results in a tremors
• treated with the drug L-dopa which adds dopamine
  to the brain. Too much L-dopa can result in
  schizophrenic-like symptoms
• _____ dopamine has been linked to schizophrenia
• thought disorder
• incurable, but drug treatment often allows the
  disease to be controlled.
• Drugs used to treat schizophrenia, such as
  Thorazine, Haldol and Clozaril make less dopamine
  available to the brain.

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NeurotransmittersAminesEpinephrine
Norepinephrine

• Inhibitory and Excitatory
• Epinephrine hormone
• Norepinephrine adrenaline

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NeurotransmittersNeuropeptidesEndorphines

• Mostly _______
• Act like opiates to block _______
• Block neurotransmitter receptor sites in the
  brain so neurons relaying messages from sensory
  neurons don't fire
• Heroine, codeine, and morphine are chemically
  similar to endorphins and have the same effect

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Myomas

• ___oma - common type of brain tumor that is
  usually benign but may still be life-threatening
• Glioblastoma multiforme highly
  __________________ form of an astrocytic tumor

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CNS

• Outer Coverings
• Brain
• cranial bones
• Spinal Cord
• vertebrate
• Inner Coverings
• ________________
• Dura mater
• Arachnoid membrane
• Pia mater

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Meninges

• Dura Mater
• Outer layer
• _________, white fibrous tissue
• Arachnoid Membrane
• Middle layer
• _______________, cobwebby
• ____ Mater
• Inner layer (adheres to outer surface of brain
  and spinal cord)
• Transparent
• Contains blood vessels

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Meninges Spaces

• Epidural Space
• Between dura mater and bony covering of brain and
  spinal cord
• Supportive cushion of ___
• Subdural Space
• Between dura mater and arachnoid membrane
• Lubricating serous _______
• Subarachnoid Space
• Between arachnoid and pia mater
• Contains cerebrospinal fluid (_____)

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Falx cerebri extension of dura mater that
extends vertically to separate two hemispheres
Epidural Space
Subdural Space
Dura Mater
Subarachnoid Space
Arachnoid Membrane
Pia Mater
Arachnoid
Dura
Pia
sc
vertebrate
Epidural Space
Subdural Space
Subarachnoid Space (contains CSF)
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___________________

• infection/swelling of meninges
• caused by infection with viruses, bacteria, or
  other microorganisms
• may also arise due to certain drugs or other
  diseases.
• potentially life threatening due to the
  inflammation's proximity to the brain and spinal
  cord it is therefore a medical emergency
• symptoms
• headache and neck stiffness
• Fever, confusion or altered consciousness
• inability to tolerate light (photophobia) or loud
  noises (phonophobia).
• Sometimes, especially in small children, only
  nonspecific symptoms may be present, such as
  irritability and drowsiness.
• If a rash is present, it may indicate a
  particular cause of meningitis (meningococcal
  bacteria
• diagnosed by a spinal tap
• must be treated promptly with antibiotics and
  sometimes antiviral drugs
• In some situations, corticosteroid drugs can also
  be used to prevent complications from overactive
  inflammation.
• can lead to serious long-term consequences such
  as deafness, epilepsy, hydrocephalus and
  cognitive deficit, especially if not treated
  quickly.
• Some forms of meningitis may be prevented by
  immunization

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CSF

• Provides supportive, protective cushioning
• Reservoir of circulating fluid
• Monitored by brain to detect changes in internal
  environment
• Located in subarachnoid space and within cavities
  and canals of brain and spinal cord
• Average adult has ____ ml of CSF

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Hydrocephalus

• ______ _______
• Sometimes in the unborn child, the drainage canal
  for CSF becomes stopped up.
• The fluid builds up and the pressure causes the
  brain to expand like a balloon.
• Causes the child to have a very large head and to
  be mentally retarded
• Accompanies diseases (spina bifida, brain tumor,
  blood clots)
• Possible coma or death

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Spinal Cord

• Within spinal cavity (vertebral column)
• Extends from foramen magnum to L1
• Reflex center
• Dorsal nerve root
• carries sensory info _______ spinal cord
• Ventral nerve root
• carries motor info _____ of spinal cord
• Interneurons in s.c. ________ matter
• Spinal nerve single mixed nerve on each side of
  s.c where dorsal and ventral nerve roots join

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Spinal Cord

• Gray Matter
• Extends length of s.c
• Consists of _____ ________ of interneurons and
  motor neurons
• Spinal reflex centers located here
• Incoming sensory, outgoing motor
• White Matter
• Surrounds gray matter
• Consists of _________

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Spinal Cord
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Brain

• One of largest organs in adults
• ____ lbs
• 6 major divisions
• Medulla oblongata
• Pons ____________
• Midbrain
• Cerebellum
• Diencephalon
• Cerebrum

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BrainstemMedulla Oblongata

• ________ part of brainstem
• Attaches brain to s.c. just above foramen magnum
• Reticular Formation arousal, sleep
  (damagedcoma) Reticular Activating System
• Controls breathing, heart rate and the activities
  of the gut
• Coordinates swallowing, yawning, hiccuping,
  vomiting, coughing and sneezing
• Injury often causes ______

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BrainstemPons

• Between medulla and midbrain
• motor control and sensory analysis
• Regulate _____________

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BrainstemMidbrain

• Above pons, below cerebrum
• Auditory and visual centers
• Muscular control

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Cerebellum

• 2nd largest part of brain
• Numerous ______ (grooves) and _______ (raised
  area)
• Acts with cerebral cortex to produce skilled
  movements (____________)
• Controls skeletal muscles for balance
• Controls _________
• Subconscious level automatic processor
• Impulses travel from cerebellum to cerebrum and
  muscles to coordinate movement

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Diencephalon

• Between cerebrum and midbrain
• Consists of
• Thalamus
• Hypothalamus
• Optic chiasma
• Pineal body

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DiencephalonThalamus

• Major _____ station for sensory impulses on their
  way to cerebral cortex
• Sensations
• Conscious recognition of pain, temperature, touch
• Relay sensory info (except smell) to cerebrum
• ___________ of pleasant and unpleasantness
• Complex reflexes

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DiencephalonHypothalamus

• Below thalamus
• Links mind and body
• Regulates and coordinates autonomic activities
• Synthesizes hormones secreted by pituitary gland
• ________ balance
• Regulates __________
• Maintains normal body
• ________________

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DiencephalonPineal Body

• Regulates bodys biological clock
• Produces some hormones
• __________

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Cerebrum

• Cerebral cortex, cerebral tracts, cerebral
  nuclei.
• Four general functions
• Consciousness
• Language
• Emotions
• Memory
• ______ (bumps) and _________ (shallow grooves)
• ______________ deep grooves, divides lobes
• Longitudinal fissure divides hemispheres
• Central sulcus between frontal and parietal
  lobes
• Lateral fissure between temporal and parietal
  lobes
• Parietooccipital fissure between occipital and
  parietal lobes
• Outer surface made up of ___ layers of gray
  matter
• Largest and uppermost

Parietooccipital fissure
Lateral fissure
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Frontal lobe

• Prefrontal ______________
• And adaptation of the personality to events and
  experiences
• Foresight and imagination
• Sense of self
• Frontal
• main motor areas (originate movement that is
  coordinated elsewhere)
• _____________ Area speech production

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Parietal lobe

• Principle ___________area
• Touch
• Proprioception
• Lesions cause sensory losses
• Involvement in cognition
• Receptive speech loss

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Temporal lobe

• Cognition
• Emotion
• Memory
• Auditory
• _______________ area speech comprehension

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Occipital lobe

• _________
• Visual processing and visual association
• Involved in eye movement

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Limbic System

• emotion, behavior, 
• long term memory, and olfaction
• Set of brain structures that forms the inner
  border of the cortex
• Corpus callosum connects left and right
  hemispheres
• ______________ long-term memory cognitive maps
• ______________ reward, fear, mating

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____________Hemisphere
_____________Hemisphere

• Language
• Dominating hand movements
• Reasoning (tangible data)
• Positive emotion

• Hearing
• Touch
• Spatial relationships
• Nonsymbolic data
• Art
• Spiritual
• Negative emotions

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busy wave
EEG/ECG Electroencephalogram
relaxed wave
drowsy wave
deep sleep wave
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CNS Disorders

• _____________ loss of speech
• Hemiplegia, paraplegia, triplegia, quadriplegia
  paralysis
• Cerebral palsy crippling disease involving
  permanent damage to motor control areas of the
  brain
• __________________
• Alzheimers inherited form of dementia
• Huntingtons Disease affects memory in middle to
  late adulthood, causing cortex lesions
• AIDS
• Seizures
• ___________________

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Somatic Nervous System

• Contraction of _________ muscles
• Skeletal muscle somatic effector
• All _____________ motor pathways outside of CNS
• Neurotransmitter ______

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Reflexes

• All voluntary motor pathways outside of CNS
• Reflexes
• Action resulting from nerve impulse passing over
  a reflex arc
• Predictable response to stimuli
• ____________ Reflex
• Visceral
• Contraction of smooth or cardiac muscle
• Secretion of glands
• ____________ Reflex
• Contraction of skeletal muscles

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Somatic Reflexes

• Contraction of skeletal muscles
• Reflexes deviate from normal in certain
  conditions
• Reflex testing is valuable diagnostic tool
• Patellar Reflex extension of lower leg
• Achilles Reflex extension of foot
• ____________________ Reflex extension of big toe
• Present until age 1.5
• If present after, indicates damage to
  corticospinal fibers
• Plantar Reflex flexion of all toes and slight
  turning in of foot
• Corneal Reflex wink when touch cornea
• Abdominal Reflex stroke side of abdomen causes
  drawing in of abdominal wall

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Knee-Jerk (Patellar) Reflex
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Autonomic Nervous System

• ________________/Visceral body functions
• Cardio, resp, dig, urogen
• Maintain homeostasis by regulating heartbeat,
  smooth muscle contraction, glandular secretions
• Conduct impulses from CNS to autonomic effectors
• Two divisions
• Sympathetic
• Parasympathetic

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Autonomic Conduction Pathway
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Parasympathetic Nervous System
Sympathetic Nervous System

• Feed-or-Breed
• Rest-and-Repose
• Counteracts Sympathetic

• Fight-or-Flight
• Allows body to function under stress

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ANS Neurotransmitters

• Norepinephrine (adrenaline)
• ________________ fibers
• release norepinephrine in postsynaptic
  sympathetic neurons
• Acetylcholine (ACh)
• ________________ fibers
• release ACh in presynaptic sympathetic neurons
• release ACh in pre and post parasympathetic
  neurons

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Norepinephrine

• Affects visceral effectors by binding to
  adrenergic receptors
• Alpha receptor blood vessels __________
• Beta receptor blood vessels ____________
• Inhibiting action of norepinephrine
• MAO (monoamine oxidase) enzyme that breaks up
  norep that are taken up by synaptic knobs

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ACh

• Binds to cholinergic receptors
• Nicotinic receptors
• Muscarinic receptors
• Inhibiting action of Ach
• acetylcholinesterase

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