Chapter 2: Biological Basis

1. Neurons: specialized cells in the nervous system that receives & sends impulses

• sensory (afferent): transmit impulses from sensory system to the brain
• motor (efferent): transmit impulses from brain to muscles & glands 
• interneurons: transmit information between neurons 
  

2. Glial cells

• insulate & support neurons 
• fills in space between neurons 
• create myelin sheath 
• remove waste products 
• provide nourishment 
• prevent harmful substances from entering the brain
  

3. The Neural Impulse

1. Resting potential 
   
2. Action potential:
• Sudden, massive changes in charges of the neuron
• occurs when depolarization reaches threshold of excitation
• ions flow across cell membrane = the neuron fires

3. Absolute refractory period
• immediately after an action potential when another action potential cannot occur

4. Relative refractory period 
• following absolute refractory period 
• neuron only responds to stronger than normal impulse

Transmission Between Neurons

Neurotransmitter examples:

1. Acetylcholine (ACh)

• released @ neuromuscular junctions
• important: arousal & attention
• loss in ACh-producing cells: Alzheimer's disease

2. Dopamine

• learning, memory, emotions
• loss of dopamine-producing cells: Parkinson's disease

3. Serotonin

• abundant in the brain
• sets emotional tone
• low levels = depression

4. Endorphin

• reduce pain
• inhibits neurons that transmit pain impulses

Psychopharmalogy

- most psychoactive drugs & toxins inhibit / enhance synaptic transmission




1. Agonists

• chemical substances – enhances release of neurotransmitters to receptor sites of next cell
• excitatory: increase excitation
• inhibitory: increase inhibition

2. Antagonists

• chemical substances – block / reduces cell response

Neural plasticity

• brain can be altered structurally & chemically by experience

• rat studies: enriched environment = larger neurons + more connections (has also been shown in humans)

• recent research has also shown evidence of neurogenesis (production of new brain cells) in human brains

Nervous system

1. Central nervous system (CNS)

• brain
  - receives & processes sensory information
  - initiates responses
  - stores memories
  - generate thoughts & emotions
• spinal cord
  - conducts signals to & from the brain
  - control reflex activities

2. Peripheral nervous system

• connects CNS to the rest of the body
• efferent neurons – CNS to muscles & glands
  - somatic nervous system (voluntary)
  - autonomic (involuntary)
  *sympathetic division: fight / flight
  *parasympathetic: rest / digest

Studying of the nervous systems

1. Microelectrode techniques

• very small electrodes inserted into individual neurons

• study activity of a single neuron

2. Macroelectrode techniques

• picture of overall activity in the brain

a. Structural imaging

• CT scan (computerized axial tomography)
  *3D image of the brain using x-rays
  
  
• MRI (magnetic resonance imaging)
  *electromagnetic waves to produce images

b. Functional imaging

• EEG
  *electrical activity on scalp from millions of neurons
  *produce continuous picture of brain activity
  
  
• MEG & MSI (magnetic source imaging)
  *localize activities more precisely than EEG
  
  
• PET (photon emission tomography) & SPECT (single photon emission computed tomography)
  *determine location of greatest brain activity
  *radioactive glucose
  
  

• fMRI (functional MRI)
  *shows function & structure
  *measuring blood molecules' movement within the brain
  
  

The Spinal Cord

• connects brain to rest of the body
• carries motor impulses from brain to internal organs & muscles
• carries sensory information from extremities and internal organs to the brain
• controls some protective reflex movements without brain input   

The Human Brain 

The Peripheral Nervous System

1. somatic nervous system

• consists of neurons that transmit nerve impulses between body & brain (afferent & efferent neurons)

2. autonomic nervous system

• sympathetic division
  *active when angry, afraid, aroused
  *fight / flight response
  *increase heart rate & breathing
  *stops digestion 

• parasympathetic division [opposite effects to those of sympathetic]
  *calms body
  *reduces heart rate & breathing
  *restores digestion

The Endocrine System

• helps coordinate & integrate complex psychological reactions
• endocrine glands secrete hormones into the bloodstream
• organize the nervous system & body
• activates behavior (ex: sexual behavior) 

Genes, Evolution & Behavior

1. Genetics

• Heredity: transmission of traits from one generation to the next
• Chromosomes: pairs of thread-like bodies that contain genes
• DNA (deoxyribonucleic acid): organic molecules arranged in a double helix which contains the   code of life

2. Behavior Genetics

• study of behavior from a genetic perspective

3. Human Behavior Genetic

• family studies
  • assume that close family members share more of a trait than non-relatives
  • used to assess the heredity of psychological disorders

• twin studies
  • to determine how heritable a trait / disorder may be
  • identical twins = higher rate of heredity

• adoption studies
  • assess the influence of environment

• molecular genetics
  • direct study of the genetic code

4. Evolutionary Psychology

• Natural selection – survival of the fittest
• looks at the adaptive / survival values of behavior

5. Social implications

• genocides & eugenic
• creation of new categories of people

--by qxchxn