Modules 4 & 6

The Biology of Mind

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Neuron - 100 Billion- Communication System

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Glial cellsCell body (nucleus)DendritesAxonAxon Terminals (terminal buttons)Synaptic cleft

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Communication Within a Neuron

Receptors on Dendrites - Sensory (chemical reactions) - Chemicals from other neurons - Chemicals from endocrine glands - Chemicals from outside sources (e.g., Drugs)

Chemical Messages can be Excitatory or Inhibitory.Effect on dendrite is a summed effect.

- threshold

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Action Potential- all or none law

- digital message (yes/no)- one strength - one speed - one way (dendrite to Axon)

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Inside and outside of neuron are fluid environments.

Fluid chemicals have ionic charges.- sodium and potassium

Resting Potential- inside negative relative to outside.- sodium-potassium pump

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If threshold is reached at dendrite, then an action potentialbegins.

Gates in membrane open allowing sodium to flow in.Inside becomes more positive.Momentary change in charge.Passed along the membrane, carrying message to Axon Terminal.

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Myelin Sheath- Nodes of Ranvier

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Effects of Myelin

Allows action potential to skip along the membrane.- speeds conduction.

Brain neurons have no myelin (appear gray)Sensory and Motor neurons have myelin (appear white)

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Myelin and Multiple Sclerosis

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Terminal BranchesTerminal Button

Neurotransmitters (chemicals) are released into Synaptic space.

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Communication - within neuron (electric potential).- between Neurons (neurochemical).

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Neurotransmitters are cleared from the synaptic space by1) re-uptake into the terminal button2) destroyed by enzymes

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Neurotransmitters effects on behavior depends on which receptor

Acetylcholine (ACh)Motor control (paralysis)Attention and Memory (Alzheimer’s)

DopamineEmotions, learning, memory & Motor controlToo Much SchizophreniaToo Little Parkinson’s

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Serotonin – too little associated with Depression

Endorphins – nature’s pain killer

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Hormones- Chemical Messengers released by endocrine glands into the blood system

- many are identical to neurotransmitters

- have wider reaching, longer lasting effects

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Permanent Effects e.g., puberty

Temporary effects e.g., metabolism (Insulin and Thyroxin)

Hormones also effect mood e.g., premenstrual syndrome

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Hormone Disorders• Diabetes• Thyroid disorders• Depression

Hormones as drugsProblem: They effect a wide range offunctions = large number of side effects.

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Fen/Phen (Redux)- effect hunger drive/increases metabolism - also effects maintenance of heart valve (lethal side effect)

Steroids- effect development of muscles-also effects mood and thought processes in the brain.

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Nervous System

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Nervous SystemCentral Nervous System (CNS)

- Brain and Spinal Cord

Spinal Cord 1.carries messages to & from Brain Sensory Neurons

Sensory info to CNSMotor Neurons from CNS to muscles and glands

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2. Reflexes - fast, automatic actions

Sensory message Interneuron

Motor Message

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Autonomic Nervous System

1) Sympathetic- readies the body for fight or flight

Heart rate Blood Pressure breathing Digestion

2) Parasympathetic- relaxation response

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Module 5

Older Brain StructuresThalamusReticular formation Pons & MedullaCerebellumLimbic systemHypothalamus

* Know the major functions

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Module 6Cerebral Cortex

Sensory- motor functions• use about 20% of cortex.

Association Areas. (thinking, memory . . .)• uses about 80% of cortex

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Localization of Function

Specific areas of the brain have specific functions.

Damage to specific areas produces specific function deficits.

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Ways of studying the brain

1) Lesion studies (done on animals)

2) Case studies of brain damaged individuals. - relate behavior to brain areas.

3) Imaging techniquesCAT scansPET scansFMRI

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Cortex has 2 halves (hemispheres)Each controls opposite side of the body.

Each hemisphere has 4 lobes1) Frontal Lobe - Primary motor cortex (controls movement) - prefrontal cortex (planning of movements and working memory)

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Frontal LobotomiesNerve connections to the prefrontal lobe are severed.

- done to control violence and aggression

Results: loss of ability to plan and carry out even simple tasks.

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2) Parietal Lobe - primary somatosensory cortex Sensations and location of body parts

Unilateral Neglect- can sense the neglected side but fail to to attend to it.

                                                           

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3) Occipital lobe - primary visual cortex

4) Temporal Lobe - primary auditory (hearing) area. - complex aspects or vision - face blindness - motionblindness

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Corpus CallosumBand of Neurons connecting the two hemispheres.

Video

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Split Brain StudiesLeft Hemisphere - Language - critical thought (making sense)

Right hemisphere - spatial ability - face recognition

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Within the left hemisphere there are2 areas for language

Brocas’s area - frontal lobe - production of speech

Wernike’s area - temporal lobe - comprehension of speech

Damage causes aphasia (speech disorder)

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Can a person recover from brain damage?

- neurons are not replaced.

- plasticity of the brain - other parts take over function of damaged parts. - requires retraining