Tuesday, Oct 14 Chapter 2 Quiz – study guide and cards due
Wednesday, Oct 15 in class essay redo 1993 #1
Chapter 2 Neuroscience and Behavior
150 years ago science discovers the brain/body connection
Early 1800’s - Franz Gall - Phrenology - reads the bumps on the skull to reveal mental abilities and character traits
?????? Have we heard this debate before???
Phrenology - Simpson Style
Phrenology 2012 Style
Neural Communication (p. 58)
You couldn’t distinguish between small samples of brain tissue from a human and a monkey
Therefore, we can study neural systems from a monkey brain and learn about a human brain.
Neurons (p. 58)
Neurons (aka nerve cells) are the building blocks of our nervous systems
There are different types of neurons - ex - sensory neurons and motor neurons
Parts of the Neuron (p. 59)
Dendrite - receives messages
Axon - passes information to other neurons
Myelin sheath - fatty tissue insulates axons and speeds up transmission of neural impulses which are electrical signals (aka Action Potential)
Cell body or Soma - the cell’s life support centre
Fatty tissue that insulates the axon and helps speed their impulses.
Multiple sclerosis is a disease in which the myelin sheath degenerates resulting in a slowing of all communication to muscles and the eventual loss of muscle control
See TB page 6 re Guillain Barre syndrome
Action Potential (p. 59)
Neurons fire an impulse - called an Action Potential - when they receive signals from sense receptors stimulated by pressure, heat or light OR when they are stimulated by chemical messages from neighbouring neurons
The Action Potential is a brief electrical charge that travels down the axon
Ions (p. 58)
Neurons exchange electrically charged atoms called ions
Ions are negatively charged or positively charged
Ions are inside and outside of each neuron
Resting Potential (p. 58)
The fluid in a resting axon has an excess of negatively charged ions while the fluid outside the axon has more positively charged ions.
The axon opens and the positively charged outside ions flood into the first chamber of the axon. This depolarizes that part of the axon, causing the axon’s next channel to open, and so on and so on.
After the neuron fires, the neuron enters a resting pause called the REFRACTORY PERIOD where the neuron pumps the positively charged ions back outside. Once the neuron returns to the +outside/-inside state, it can then fire again.
The neuron cannot fire during the refractory period.
Excitatory and Inhibitory Signals (p. 58)
Dendrites receive signals
Signals are either excitatory(turn the neuron on) or inhibitory (turn the neuron off)
A neuron has a THRESHOLD which is a minimum intensity that it needs to turn ON.
If the excitatory - inhibitory signals exceed the threshold, then the neuron will trigger an action potential.
Threshold (p. 60)
Threshold is all or nothing. If a neuron’s threshold is met, the entire action potential will occur at the speed that neuron will normally fire.
Think of it like flushing a toilet - if the excitatory signals (pushing down the lever) minus the inhibitory signals (not pushing the lever) meet the threshold you get a complete flush.
How Neurons Communicate (p. 60)
1850 - Sir Charles Sherrington noticed that neural impulses were taking a long time to travel a neural pathway and he inferred there must be brief interruptions in the transmission
Sherrington named the gap between the neurons the synapse
The Synapse (p 61)
1. AP (electricity) travels from one neuron to another across the synapse
2. When the AP reaches the axon, it stimulates the release of neurotransmitter molecules (chemicals)which cross the synapse.
3. The neurotransmitters bind onto receptors on the dendrites of the next neuron. These neurotransmitters then excite or inhibit a new action potential in this neuron.
4. Excess neurotransmitters are reabsorbed by the sending neuron - this is called REUPTAKE.
Neurotransmitters (p. 63)
There are many types of neurotransmitters
Think of neurotransmitters as brain chemicals
Certain brain neural pathways may use only 1 or 2 types of neurotransmitters
Neurotransmitters have particular effects on our emotions and behavior
Examples of Neurotransmitters (p. 62)
Too little - Curare poison blocks receptors causing paralysis
Too little - Botox paralyses muscles
Too much - Black widow spider floods ACh causing seizures
Released in response to pain and vigorous exercise
Discovered after Pert and Snyder (1973) put a radioactive tracer on morphine and found it traveled to brain areas linked with mood and pain. They concluded that if we have these areas in the brain, we must have neurotransmitters that work in these brain areas.
We do!!!! They are called endorphines.
See page 8 TG
Drugs & Neurotransmitters (p63)
If we flood the brain with drugs like heroine and morphine (opiates) the brain may stop producing its own natural opiate endorphine
If the drugs stop we may be left with no natural opiates - our agonizing pain will persist until our body learns to produce endorphines again or until we get more artificial opiates.
Agonists & Antagonists (p 63)
Various drugs affect the synapse by either exciting or inhibiting neuron firing
Agonists excite neuron firing. They mimic a neurotransmitter or block reuptake. Ex. Morphine mimics endorphine.
Antagonists inhibit a neurotransmitter’s release OR are similar enough to the neurotransmitter to occupy the receptor site but not to simulate the site. Ex. Curare blocks Ach receptors causing paralysis.
Agonists and Antagonists (p.64)
A - neurotransmitter fits receptor site - key
B - agonist (excite) is close enough to the real neurotransmitter - key
C- antagonist (inhibit) is close enough to the real neurotransmitter to occupy receptor but not close enough to be a key
Activity - p. 10 TG
1. Chain of shoulder squeezes timed
2. Chain of ankle squeezes timed
Peripheral Nervous System
Central Nervous System
(self regulated organs/glands)
Nervous System (p. 65)
The central nervous system consists of our brain and spinal cord
Think of it as a lollipop
Peripheral Nervous System (p65)
Links the central nervous system to our sense receptors, muscles and glands
Contains sensory and motor axons bundled into nerves
3 Types of Neurons (p. 65)
1. Sensory Neurons (millions) - send information from tissue and sense organs to brain and spinal cord
2. Interneurons (billions and billions) - central nervous system’s neurons that communicate with other CNS neurons
3. Motor Neurons (millions) - take instructions from the CNS back out to body tissues
Peripheral Nervous System (p 66) 2 parts to this system
Spinal Cord - connects peripheral nervous system to the brain
Reflexes - can be as simple as a single sensory neuron and a single motor neuron communicating via an interneuron in the spine. Therefore, you jerk your hand away from a flame before the pain information reaches the brain
Severed Spinal Cord (p67)
If the spinal cord is severed, you loose all sensation (pleasure and pain) and voluntary movement in the body regions whose sensory and motor neurons connect with the spine below the injury point.
BUT, you may still have reflex - you would exhibit the knee-jerk without feeling the tap
Neural Networks (68)
Neurons cluster into work groups called neural networks.
As a neural network is used over and over the connections between the neurons get stronger and faster and more efficient.
So listen to your mother and practice your piano!!!!
Tools to Study the Brain (70)
CT Scan (xray)
Tools to Study the Brain
Clinical Observation record the results of damage to specific brain areas (after the accident)
EEG record the electrical activity in brain
Microelectrodes can detect the electrical pulse in a single neuron
Tools to Study the Brain (71)
CT Scan xrays the brain
PET Scan displays brain activity by detecting where a radioactive form of glucose goes while the brain performs a task - see p. 71
Tools to Study the Brain
MRI - head is put in magnetic field producing a picture of brain’s sof tissue
Functional MRI - detects blood flow in brain during activity
See bottom p 71
Brain of a Psychopath
Showing Digital Media clip of the psychopath brain (5 minutes)
Lower Level Brain Structures (72) The Brainstem
Begins where the spinal cord enters the skull and swells slightly forming the medulla.
Medulla - heartbeat and breathing
Reticular formation - arousal/filters and relays information
Thalamus - receives information from senses (except smell) and routes it to areas dealing with sight, hearing, taste and touch. Also routes information to cerebellum and medulla. Also slows electrical impulses during sleep and speeds them up during waking.
Pons – connects 2 hemispheres and the medulla with cerebral cortex. Heartbeat and breathing as well as sleep
Extends from the rear of the brain stem
Coordinates voluntary movement (ex walking) and balance without conscious effort
Also enables one type of nonverbal learning and memory
Cerebellum Video (6 min)
Limbic System (74)
Donut shaped system at the border of the brainstem and cerebral hemispheres
Associated with emotions of fear and aggression and food and sex drives
Kluver and Bucy turned an ill-tempered monkey into a mellow monkey by removing it
Stimulating different sites on the amygdala will produce aggression or fear
Don’t try this at home on a human!!!
Limbic System’s Hippocampus (74)
The hippocampus is where we process and form new memories
Memory trick - ends in CAMPUS - where we learn things that we remember
Limbic System’s Hypothalamus (75)
Controls our body maintenance functions such as hunger, thirst, body temperature and sexual behavior
Releases hormones that control the pituitary gland which in turn influences other glands to release their hormones
Is also our pleasure centre
Limbic System’s Hypothalamus - Reward Centre (75)
Olds and Milner (1954) discovered by mistake that putting an electrode in a rat’s hypothalamus caused it to keep returning to the place where it got the electrode. They discovered a Reward Centre. The rat would press a lever 1000’s of times and cross an electrified floor to do it.
Olds and Milner Clip 1 minute
Limbic System’s Hypothalamus (75)
Neurosurgeon has used electrodes to calm violent patients. The patients report mild pleasure.
Blum (1996) believe that addictive disorders like alcoholism may stem from a reward deficiency syndrome - a deficiency in the hypothalamus.
The Cerebral Cortex (77)
Wrinkled surface layer of the cerebral hemispheres
The body’s ultimate control and information processing centre
The more complex the cerebral cortex, the more advanced the animal
The Cerebral Cortex (77)
Think of it like wrinkled toilet paper
It is 1/8th of an inch thick and contains 20 billion nerve cells and 9 times as many GLIAL CELLS that support and nourish the nerve cells
Brain Hemispheres (77)
We have a right and left brain hemisphere each divided into 4 lobes
This area receives the visual information from the visual cortex and recodes it into an auditory form which Wernicke’s area then uses to derive meaning.
If this area is damaged you can speak but not read
Norman Geschwind’s Explanation of How We use Language (83)
Brain Reorganization (84)
Plasticity - the brain can change and reorganize itself following damage
Ex - scientists severed the neural pathways for sensory information coming from the arm to the brain. The area of the sensory cortex shifted its function and began to respond when the monkey was touched on the face
Brain Reorganization (84)
Kempermann and Gage (1999) discover that adult mice and humans can generate new brain cells
Stem cells can develop into any type of brain cell have been discovered in the fetal brain
When stressed, autonomic nervous system orders our adrenal gland to release the hormones epinephrine and norepinephrine (AKA adrenaline and noradrenaline) which increase heart rate, blood pressure and blood sugar.
Part of the fight or flight reaction
Pituitary Gland (95)
Most influential gland
Controlled by the hypothalamus
Releases hormones that affect growth and cause other glands to release their hormones (ex. Sex hormones – estrogen/progesterone F, testosterone)
Nervous System and Endocrine System (95)
These 2 systems affect each other.
Brain --- pituitary --- other glands --- hormones --- brain