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Brain Facts
○ There are more neural connections in the brain than there are star s in
our universe
∙The human brain weighs ~3lbs
∙The octopus brain has about 500 million neurons.
○ The total surface area of the cerebral cortex is about 2500 sq. cm (~2.5
ft2)
○ Unconsciousness will occur after 8-10 seconds after loss of blood supply
to the brain.
○ Neurons multiply at a rate 250,000 neurons/minute during early
pregnancy.
○
A total of 400-500 ml of cerebrospinal fluid (CSF) is produced every
day.
∙Cerebrospinal fluid is normally clear and colorless.
∙There are about 13,500,000 neurons in the human spinal cord.
∙The human spinal cord is 45 cm long in men and 43 cm long in women.
∙There are 1,000 to 10,000 synapses for a "typical" neuron.
Brain
• One of largest organs in adults
• 3 lbs
• 4 major divisions
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Medulla oblongata
Pons
Midbrain
Cerebellum
Diencephalon
Cerebrum
Brainstem
Brainstem
Medulla Oblongata
• Lowest part of brainstem
• Attaches brain to s.c. just above foramen
magnum - the hole at base of skull
• Reticular Formation – arousal, sleep
(damaged=coma) [Reticular Activating System]
• Controls breathing, heart rate and the activities
of the gut
• Coordinates swallowing, yawning, hiccuping,
vomiting, coughing and sneezing
• Injury often causes death
Brainstem
Pons
• Between medulla and midbrain
• motor control and sensory analysis
• Regulate respiration
Brainstem
Midbrain
• Above pons, below cerebrum
• Auditory and visual centers
• Muscular control
Cerebellum
• 2nd largest part of brain
• Numerous sulci (grooves) and gyri (raised area)
• Acts with cerebral cortex to produce skilled movements
(coordination)
• Controls skeletal muscles for balance
• Controls posture
• Subconscious level; automatic processor
• Impulses travel from cerebellum to cerebrum and muscles to
coordinate movement
Diencephalon
• Between cerebrum and midbrain
• Consists of
– Thalamus
– Hypothalamus
– Optic chiasma
– Pineal body
Diencephalon
Thalamus
• Major relay station for sensory impulses on their way to
cerebral cortex
• Sensations
– Conscious recognition of pain, temperature, touch
– Relay sensory info (except smell) to cerebrum
• Emotions of pleasant and unpleasantness
• Complex reflexes
Diencephalon
Hypothalamus
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•
•
•
•
•
•
Below thalamus
Links mind and body
Regulates and coordinates autonomic activities
Synthesizes hormones secreted by pituitary gland
Water balance
Regulates appetite
Maintains normal body
temperature
Diencephalon
Pineal Body
• Regulates body’s biological clock
• Produces some hormones
– Melatonin
Cerebrum
• Each hemisphere has 4 lobes
– Frontal
– Parietal
– Temporal
– Occipital
Lateral fissure
Frontal lobe
•
•
Prefrontal: Personality
– 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)
– Broca’s Area: speech production
Parietal lobe
•
•
•
•
Principal sensory area
Touch
Proprioception
Lesions cause sensory
losses
• Involvement in cognition
• Receptive speech loss
Temporal
lobe
•
•
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•
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Cognition
Emotion
Memory
Auditory
Wernicke’s area: speech
comprehension
Occipital
lobe
• Vision
• Visual
processing
and visual
association
• Involved in
eye movement
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
– Hippocampus:
long-term memory;
cognitive maps
– Amygdala:
reward, fear,
mating
Left
Hemisphere
•
•
•
•
Language
Dominating hand movements
Reasoning (tangible data)
Positive emotion
Right
Hemisphere
•
•
•
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Hearing
Touch
Spatial relationships
Nonsymbolic data
– Art
– Spiritual
– Negative emotions
CNS Disorders
•
Aphasia
•
Hemiplegia, paraplegia, triplegia, quadriplegia
•
Cerebral palsy
•
•
Spastic paralysis
CVA (cerebrovascular accident) aka Stroke
•
Dementia
– loss of speech
– paralysis
– crippling disease involving permanent damage to motor control areas of the brain
– blockage or hemorrhage of blood causing neuronal damage
– Alzheimer’s: some types are genetic, others appear environmental in nature,
women are almost twice as likely to get it than men.
– Huntington’s Disease: affects memory in middle to late adulthood, causing cortex
lesions
– AIDS
•
Seizures
– Epilepsy
Reflexes
• All voluntary motor pathways outside of CNS
• Reflexes
– Action resulting from nerve impulse passing over a
reflex arc
– Predictable response to stimuli
– Autonomic Reflex
• Visceral
• Contraction of smooth or cardiac muscle
• Secretion of glands
– Somatic Reflex
• Contraction of skeletal muscles
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
– Babinski 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
Knee-Jerk (Patellar) Reflex