Transcript Powerpoint version

What makes drugs addictive?
Drug tolerance – occurs because the body
tries to maintain homeostasis in presence of
high neurotransmitter levels
What makes drugs addictive?
Repeated drug use causes elevated
dopamine
Body decreases # dopamine
receptors, dopamine prod’n
“Down regulation”
Dopamine receptors
Normal
Abuser
Study showing down regulation
Repeated doses of morphine
reduce # of dendrites in
dopamine neurons
What makes drugs addictive?
Now a higher dose is necessary for ‘high’
Normal ‘happy’ increases in dopamine can’t
stimulate pleasure bc the pleasure center is
badly altered
Endocrine system
Hormones are
transported by the
blood, but only cause
responses in target
cells
Endocrine functions
Regulation of growth and development
Homeostasis - ex: salt/water balance, stress,
metabolism
Reproduction
Types of hormones
Amines use tyrosine (epinephrine and
norepinephrine)
Peptides (oxytocin, vasopressin, GH, insulin,
TSH)
Both types are water soluable
Types of hormones
Steroids - from cholesterol (adrenal cortex,
testis, ovary and placenta). Hydrophobic,
transported by proteins
How do hormones signal cells?
Steroid and thyroid hormones activate genes
Diffuse freely into and out of cells
Receptor proteins are in cytoplasm. Hormone
binds and moves inside nucleus
How do hormones signal cells?
Peptide hormones utilize a 2nd messenger
mechanism
Target cells have specific receptor for
hormone on cell surface, which triggers 2nd
messenger
Comparing the two systems
Nervous system - signals sent via specific
“wiring”
rapid, precise responses
Endocrine system - specificity is at the
receiving end
overall body responses, effect may take
hours
Fig. 5-1, p. 108
Nervous system - divided into central
and peripheral regions
Somatic nerves innervate skeletal
muscles
Autonomic nerves innervate internal
organs
Fig. 5-2, p. 109
Neuroglia
Most CNS cells are glial cells
They provide structure and maintain
interneurons in the CNS
Are capable of dividing, even in
nuclei of
adulthood glial
cells
neuron
Astrocytes:
hold neurons together
establish a blood-brain barrier w/capillaries
repair brain injuries
breakdown some neurotransmitters
take up excess K+ from the brain ECF
 Microglia are the immune defense of the CNS
 Oligodendrocytes form myelin sheaths around
axons
 Ependymal cells line the internal cavities of the
CNS.
Question: How does multiple
sclerosis form?
Multiple sclerosis – immune system targets
oligodendrocytes, causing degeneration of
myelin in CNS
Cranial meninges
Dura mater
Arachnoid
Pia mater
Scalp
Skull
Arachnoid mater
Subarachnoid
space of brain
Brain
Ventricles
Right lateral ventricle
Left lateral ventricle
Third ventricle
Fourth ventricle
Cerebral spinal fluid (CSF)
provides almost neutral balance for brain (it
“floats”)
cushions and nourishes brain
produced by tissue in ventricles
CSF produced in ventricles and resorbed
in venus sinus
Hydrocephalus
Meningitis
Meningitis: infection, inflammation of
meninges - viral or bacterial.
Bacterial infections are quite serious and
can result in encephalitis, brain damage,
death.
Why is it often difficult to
deliver drugs to the brain?
Blood brain barrier
Exists at capillaries that serve the brain
Capillaries have tight junctions
Normal capillary
Lipid-soluble
substances
Astrocyte
processes
Water-lined pore
BBB capillary
Carrier-mediated
transport
Lipid-soluble
substances
Tight junction
What molecules pass through the
blood brain barrier?
Lipid soluble vs. water soluble
Brain infections are generally rare, but
harder to fight when established (antibodies
can’t pass)
Meningitis
How can drugs pass through the
blood brain barrier?
The BBB makes it difficult for drug
treatments to enter brain
Not everything can be small, lipid soluble
Via nanotechnology, engineered
molecules may carry treatments otherwise
water soluble
(posterior)
gray matter
white matter
(anterior)
cortex
Table Cerebral
5.3 (1)
Page 144
Cerebral cortex
Cerebrum
Basal nuclei
Basal nuclei
Cerebrum
 Cerebral cortex is highly convoluted,
outer layer of gray matter. It covers an
inner core of white matter.
 An inner core of basal nucleii are
located deep within the white matter.
Temporal
lobe
Occipital
lobe
Receives “somesthetic” sensations
and proprioreception
Parietal
lobe
Temporal
lobe
Occipital
lobe
Parietal
lobe
Frontal
lobe
Voluntary motor activity, speech, thought
Temporal
lobe
Occipital
lobe
Primary motor
cortex
Somatosensory
cortex
Frontal
lobe
Parietal
lobe
Central
sulcus
Figure 5.11 (2)
Page 149
Sensory homunculus
Left
hemisphere
Temporal lobe
Motor homunculus
If you lose one sense, do others
compensate?
 Auditory ability is enhanced with loss of
vision even for just a few hours
 Mapping can be altered through experience
– “plasticity”
Posterior parietal cortex – transforms visual
information into movement commands
Premotor
cortex
Prefrontal
cortex
Posterior
parietal cortex
Parietal lobe
Frontal lobe
Temporal lobe
Occipital
lobe
Cerebellum
Associative areas:
Prefrontal (association) cortex - plans
voluntary activity, decision-making,
creativity, and personality traits.
Then the pre-motor cortex (w/
neighboring area) will orient the body,
help plan and coordinate movements
Muscle movement
Pre
Areas that communicate to the 1o motor cortex
to control voluntary movement
Premotor
cortex
Prefrontal
cortex
Posterior parietal
cortex
Language areas
 Broca’s area is responsible for speaking
ability.
 Wernicke’s area functions for language
comprehension.
Lateralization of hemispheres

corpus callosum
Diencephalon
 Hypothalamus – Controls much of the
endocrine system via pituitary gland
 Thalamus - performs some sensory
processing, transmits signals to ‘higher’
areas
 Pineal – linked with circadian clock
Diencephalon
Thalamus
Table 5.3 (1)
Page 144
Midbrain
Pons
Midbrain
Brain stem
Pons
Medulla
Cerebellum
Medulla
Cerebellum
Brain stem
Brain stem and cerebellum
Brain stem - Controls basic functions:
breathing, heart rate, digestion, etc.
Cerebellum maintains balance, enhances
muscle tone, and coordinates skilled
muscle activity
Coordination and smooth movements
require additional input
 Cerebellum – compares motor cortex output
with what is happening in body. Important for
acquiring physical skills (procedural memory)
 Basal nuclei – inhibits unwanted movements.
Associated with Parkinson’s disease,
Huntington’s disease
Basal nuclei
 inhibits muscle tone
 selects and maintains purposeful muscle
activity while inhibiting useless movement
 monitors and controls slow, sustained
contractions (posture)
Reticular activating system
Visual
impulses
Reticular
formation
Brain
stem
Auditory
impulses
Spinal cord
Sleep questions
 Why do we sleep?
 How does our physiology change with sleep?
 Interested in delta and theta brain waves in
sleep
 Why can some people fxn on fewer hours of
sleep and others require more?
Sleep physiology and function
Sleep is complex and electrically active
Deep NREM sleep: body repair, build bone, muscle
Rodents deprived of sleep live 3 weeks instead of
normal 2-3 years
BP, body temp, urine filtering, GI motility decrease.
GH increases (cell repair, growth).
Activity, breathing dependent on sleep stage.
 During REM body movement
is inhibited except for face, eyes
Sleep stages
Stages defined by frequency and
amplitude of EEG waves
Theta
Delta
Theta
How long should sleep last?
Humans generally require 7-8 hours of sleep
 10% require more
 5% require less (some have mutation on
DEC2 or BHLHE41 genes). They have
reduced sleep but no less NREM sleep