brain basics. gross brain anatomy forebrain midbrain hindbrain (brainstem = midbrain + hindbrain -...
Post on 17-Jan-2016
254 Views
Preview:
TRANSCRIPT
Brain Basics
Gross Brain Anatomy
Forebrain
Midbrain
Hindbrain
(Brainstem = Midbrain + Hindbrain - Cerebellum)
Hindbrain
• Medulla• Pons• Cerebellum
Medulla Oblongata• caudal end of brainstem; rostral end (towards the face) of spinal cord
• connects rest of brain to spinal cord (lots of myelinated tracts)
• life support functions (heart rate, respiration) – recall connection to the control of blood pH!
• Autonomic nervous control
Pons
• ventral side of cerebellum
• levels of consciousness, sleep,
• arousal, control of autonomic functions,
• sleep, relay info to cerebellum
Cerebellum• coordination of voluntary
movement
• learning motor behaviors
• involved in cognition
• timing of motor output• http://www.youtube.com/watch?v=TCisaP09yFU
Midbrain• rostral end of brainstem: reticular activating system, superior/inferior
colliculi (involved with eye and ear reflexes)
• arousal, wakefulness
• source cells for some important neurotransmitters
Forebrain
• Cerebral Cortex• Thalamus• Hypothalamus• Basal Ganglia• Limbic System
Thalamus
• relays information from diverse areas to cerebral cortex
• integrates sensory information
• regulates sleep-wakefulness
Hypothalamus• homeostatic control (e.g. body
temperature, sex drive, food and water intake)
• regulates autonomic and endocrine systems (via communication with pituitary gland
• Infundibulum connects hypothalamus to pituitary glands
Basal Ganglia• voluntary movement, posture,
routine behaviours (habits), cognitive-emotional functions
• Dopaminergic nerve tracts are lost in this area in Parkinson’s Disease (leads to involuntary movements
Limbic System
• Medial Forebrain Bundle– collection of various nerves
running upstream through midbrain
– involved in reinforcement
• Hippocampus
• Amygdala
• Nucleus Accumbens
Hippocampus• medial side (towards middle) of temporal lobe
• consolidation of short term memory into more permanent memory (memory “builder” but not a “storehouse”)
• recollection of spatial relationships
• http://www.pbs.org/wgbh/nova/body/how-memory-works.html
Amygdala
• inferior medial temporal lobe
• emotional feelings, fear, behavior, perception
Cerebral Cortex
Frontal lobe
Parietal lobe
Occipital lobe
Temporal lobe
Occipital Lobe
• vision
Parietal Lobe
• body sensation (touch, pain, etc.)
• speech reception
• spatial relationships
Temporal Lobe
• hearing
• memory
• emotion
• vision
Frontal Lobe
• planned motor behavior
• speech production
• higher cognition
• social reasoning
BRAIN ON DRUGS?
Nucleus Accumbens
• very important in reinforcement and addiction
• regulation of movement
• cognitive aspects of motor control
Neurons “communicate” with each other using neurotransmitters
Neurotransmitters convey “messages” across the synapse
Dopamine/Opioids: Brain’s incentive reward systems
Activation of reward center produces a “wanting” and “liking” response
Natural events activate these reward systems
0
50
100
150
200
0 60 120 180
Time (min)
% o
f B
asal
DA
Ou
tpu
t
NAc shell
Empty
Box Feeding
Di Chiara et al., Neuroscience, 1999.
FOOD
MountsIntromissionsEjaculations
Fiorino and Phillips, J. Neuroscience, 1997.
Natural Events Elevate Dopamine Levels
100
150
200
DA
Con
cen
trat
ion
(%
Bas
elin
e)
15
0
5
10
Cop
ulation
Freq
uen
cy
SampleNumber
1 2 3 4 5 6 7 8
SEX
Female Present
Some drugs activate your reward systems since they act on the same receptors
Drugs make your brain really happy…..
Normal Brain Brain on Drugs
BUT only when your brain is on drugs.
0100200300400500600700800900
10001100
0 1 2 3 4 5 hr
Time After Amphetamine
% o
f B
asal
Rel
ease
DADOPACHVA
Accumbens AMPHETAMINE
0
100
200
300
400
0 1 2 3 4 5 hrTime After Cocaine
% o
f B
asal
Rel
ease
DADOPACHVA
AccumbensCOCAINE
0
100
150
200
250
0 1 2 3 4 5hrTime After Morphine
% o
f B
asal
Rel
ease
Accumbens
0.51.02.510
Dose (mg/kg)
MORPHINE
0
100
150
200
250
0 1 2 3 hrTime After Nicotine
% o
f B
asal
Rel
ease
AccumbensCaudate
NICOTINE
Di Chiara and Imperato, PNAS, 1988
Effects of Drugs on Dopamine Release
Repeated use of drugs trigger compensatory processes and saturate the brain’s reward systems
individual can become conditioned/habituated/adapted to the intense level of drug-induced pleasure (develops tolerance or sensitization)
the normal level of natural rewards are no longer experienced as very pleasurable, and
after chronic use, the brain’s reward systems becomes so changed that nothing is pleasurable – not even the drugs!
Brain on drugs after tolerance
Brain on drugs for an extended
period
Chronic drug taking ….reorganizes the liking and wanting systems
… drugs may no longer be pleasurable but you still want them…
Drugs can change your brain so that natural events are no longer pleasurable
Normal
Addicted
The brain now has a disease… it’s a different brain under constant stress
When the “switch” gets flips depends on ….
your brain chemistry….
your drug history….
your drug history….
and other factors
Even 80 days following detox, a methamphetamine user’s dopamine transporter system (right) hasn’t
recovered to normal levels (left)
Normal
Cocaine Abuser (10 da)
Cocaine Abuser (100 da)
Cocaine has long lasting effects
At high enough doses, Ecstasy destroys nerve fibers
Mu receptor distribution5HT1a receptor distribution
top related