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Psych CH 2 Sec 1
31
BIOLOGICAL BASIS OF BEHAVIOR
Chapter 2
How much of our behavior is based on our brain?
The brain houses a complex web or nuerons, synapses, neurotransmitters, & electrical impulses
So what if something happens to our brain?
NERVES
IT'S JUST NERVES
PHINEAS GAGE
Gage is a railroad worker/foreman
Explosives used to blast paths open
Tamping iron used to push explosives down into holes
CHANGES TO THE BRAIN
Rod propells through Gage's head
Gage miraculously lives - gets up to go right back to work
2 months later, returns to the job... but there's something different
Gage's personality becomes more hostile, animalistic, shrewd, and erratic
Damage to his brain left certain functions untouched, others changed
NEURONS
Glial cells - garbage trucks of the nervous system
Insulate neurons as well - myelin
Cells of the nervous system that conduct impulses
They take information like light or temperature and pass that info to the brain
It is in the brain that most of our neurons exist
NERVOUS SYSTEM
Neurons vary on location and function
Most have body, axon, and dendrites
Nucleus is the power source of the neuron
Dendrites receive the message
Axon sends the message along
Messages and Myelin
Messages and Myelin
Axon carries the impulse to the axon terminals
The "end of the line" occurs at other neurons, muscles or glands
These networks become more complex as an individual matures
Myelin insulates the axon providing a smooth neural impulse
Infants develop myelin as they grow
MS patients lose this protective sheathing
Afferent and Efferent Neurons
Afferent and Efferent Neurons
How do you know it hurts when you stub your toe? Afferent neurons (or sensory neurons) carry that message to your spinal cord and brain
Before you can yell (or maybe curse) your efferent (or motor) neurons tell you to pick up your foot and perform a one-legged dance while holding your toe
Your pulse may increase or you may start sweating
It's just + & -
- Neural impulses - messages that travel within neurons
- Ions within and outside the neuron - at rest negatively charged chloride inside
- Stimulus depolarizes the neuron - if not enough stimulus => nothing happens
- If enough stimulus - action potential reached => message sent
THE CONNECTION
The Firing Neuron
Threshold needs to be met in order for the neuron to fire
When the neuron fires the strength of the impulse is constant
This is known as the all-or-none principle
REFRACTORY
REFRACTORY
A time period after the neuron fires when it connot send messages from a stimulus
Only a few thousandths of a second
Space between and axon terminal and the nearest dendrite - synaptic cleft
Not like the arcing of an electrical spark
Neurotransmitter chemicals are released from the axon terminal
These specific neurotransmitters are designed to fit intricately into receptors
This "lock and key" mechanism ensures that the correct neurotransmitter is correctly accepted by the dendrite
The Synapse
Neurotransmitters
Chemical keys to communication
Each fits the receptor site intended
Any neurotransmitter left behind will be reabsorbed by the axon terminal - reuptake
CHEMICAL KEYS
Acetylcholine (ACh)
Can be excitatory and inhibitory
Curare: poison that stops ACh from assisting muscle movement
Dopamine - neurotransmitter involved in pleasure perception, voluntary movement, learning and memory
Drugs like alcohol and nicotine highten levels of dopamine
Decreased levels of dopamine - Parkinson's (loss of muscle control) jerky, uncoordinated movement
Schizophrenia also linked to dopamine - patients have too many receptors - hallucinations through overutilization (too much stimulus)
ACh typically found in the hippocampus
This brain structure is, in part, responsible for memory storage
Alzheimer's sufferers have decreased levels of ACh available to the brain
An experiment decreased the amount of ACh in lab rats; could not remember how to navigate a maze they'd run before
GABA - gamma-aminobutyric acid: an inhibitor
Could be involved in anxiety reduction - combined with alcohol GABA effects can be amplified - loss of inhibition/anxiety
Endorphins - another inhibitor - explains how an athlete can continue with an activity while incurring an injury
These are naturally produced in the brain and prevent pain causing chemicals from reaching their receptors
Morphine is a synthetic endorphine - same "pain dulling" effects
The Take-home...
Neurotransmitters are the microscopic reasons we do what we do, think, feel, etc.
In total, these elements form the basis of everything that occurs within us
But how does all this occur within our body?
Norepinephrine - an excitatory neurotransmitter involved in general arousal, learning and memory, and eating
Can also be a hormone
Artificial stimulants can mimic norepinephrine (cocaine and speed) - can both facilitate the release and block the reuptake
Repeated use can lead to dependency
Serotonin - emotional arousal and sleep
A powerful neurotransmitter; deficiencies can lead to alcoholism, depression and aggression
CHEMICAL KEYS
THE NERVOUS SYSTEM
THE NERVOUS SYSTEM
Central and peripheral
The central nervous system consists of the brain and spinal cord
Where most of the processing happens
The peripheral nervous system "makes the rest work" - these are the outer components (like the mouse, keyboard, moniter)
How do you smile or simply stand up straight?
A combination of both the central and peripheral nervous systems
You scared the Bejesus outta me!!!
AHHH!!!
Think of a time when you were very frightened. List the bodily symptoms you experienced.
Think of a time when you were very calm and relaxed. What sorts of bodily symptoms did you experience then?
THE PARTS...
Parts of the nervous systems
Somatic and Autonomic nervous systems
- Somatic - afferent and efferent neurons
- Transmits sensory messages
- Autonomic - also afferent and efferent but controls glands and internal organ muscles
- Automatic responses - heartbeat, breathing, digestion
- Two divisions - sympathetic and parasympathetic
Sympathetic and Parasympathetic
Sympathetic - excites the organs and nervous system - "fight or flight"
Parasympathetic - calming process to bring the body back to homeostasis
Central Nervous System
Spinal cord - bundle of nerves transmitting messages to the brain
Spinal reflex - unlearned response that happens before the message makes it to the brain
Gray matter - old brain matter
White matter - myelinated sections (association areas)