© 2004 john wiley & sons, inc. huffman: psychology in action, 7e the nervous system

© 2004 John Wiley & Sons, Inc.Huffman: PSYCHOLOGY IN ACTION, 7E

The Nervous System


Central vs. Peripheral NS


Central Nervous System

• The CNS is composed of the brain and spinal cord

• Spinal cord connects the brain with the PNS– Spinal cord is comprised of cell bodies and

axons that carry messages• Afferent: toward the brain (sensory function)• Efferent: away from the brain (motor function)


Peripheral Nervous System

• The Peripheral Nervous System (PNS) includes all nerves outside the brain and spinal cord– Somatic NS carries sensory messages to

brain and motor commands to the muscles– Autonomic NS regulates automatic body

functions (such as heart rate, breathing)• Sympathetic: “Fight or Flight”• Parasympathetic: dominant when relaxed


The Autonomic Nervous System


The Spinal Cord


Neurons

• Neurons are cells that transmit information

• Neurons are composed of:– Dendrites: receive information and pass it

to cell body– Cell Body: summarizes information– Axon: extends from cell body, carries

electrical potential, sends a chemical message to adjacent neurons

© 2011 The McGraw-Hill Companies, Inc.

Neurons: Structure


Synapses and Neurotransmitters


Synapse

• The synapse is the junction between an axon terminal and an adjacent dendrite or cell body.

• Neurotransmitter (NT) molecules are released from the axon terminal into the synapse when the action potential arrives at the axon terminal.


Neurotransmitters

Neurotransmitters carry information

across the synaptic gap to next neuron.

Acetylcholine• muscle actions, learning, memory• black widow venom ↑ Ach levels • botox (botulin) ↓ Ach levels • Alzheimer’s disease: ↓ Ach levels

GABA • anxiety: ↓ GABA levels


Neurotransmitters

Glutamate– excitatory – learning & memory– involved in many psychological disorders

Norepinephrine– stress and mania: ↑ norepinephrine levels– depression: ↓ norepinephrine levels– regulates sleep states in conjunction with ACh


Neurotransmitters

Dopamine

– voluntary movement– reward anticipation– stimulant drugs: activate dopamine

receptors– Parkinson’s disease: ↓ dopamine levels– schizophrenia: ↑ dopamine levels


Neurotransmitters

Serotonin– regulation of sleep, mood, attention,

learning– depression: ↓ serotonin levels– prozac: ↑ serotonin levels

Endorphins– natural opiates– mediate feelings of pleasure and pain


Resting Potential

Sodium ions are concentrated on the outside of the axon membrane.

Potassium ions are concentrated on the inside of the axon membrane.

Ion channels are closed.

The inside of the axon membrane is more negative that is the outside.


Neurotransmitters

Oxytocin– both a hormone and a neurotransmitter– related to onset of lactation in new mothers– related to attachment/emotional bonds

Note: Drugs can interfere with neurotransmitters

– mimics or enhances NT effects– blocks effects of NT


Action Potential

• Action potential occurs when the membrane potential rapidly shifts from -70 to +40 mV– Ion channels open in the membrane, allowing

sodium ions to enter the axon– Sodium entry shifts the membrane potential

toward a positive value– Potential is restored when other channels open,

allowing potassium ions to exit the axon


The Action Potential


Action Potential Details

• Action potentials vary in frequency (a few pulses per second to a max of 1000 pulses per second)

• APs have a refractory period (about 1 msec)

• AP is “all or none” in nature


Myelin

• Myelin is a fatty, waxy substance coating the axon of some neurons.

• Functions:– Speeds neurotransmission– Insulates neurons from each other– Makes neurotransmission more efficient


Brain imaging technologies

• Positron Emission Tomography (PET)• Makes use of radioactive tracer to measure

cerebral blood flow.


Brain imaging technologies

• Functional Magnetic Resonance Imaging (fMRI)

• Uses electromagnets to measure oxygen levels in brain.


Psychoactive Drugs

• Psychoactive drugs affect the nervous system to alter mood, emotion, and thought

• Psychoactive drugs act by:– Increasing or decreasing release

of neurotransmitters – Stimulating or blocking receptor

sites


Psychoactive Drugs

• Agonists enhance neurotransmitter function

• Antagonists block neurotransmitter function


The Endocrine System

• Hormones are secreted into the blood by the endocrine system

• Hypothalamus controls hormone release


The Endocrine System

Functions of the endocrine system:

1. Maintain homeostasis

2. Regulate reproductive system


Brain: Structure and Function


Brainstem

• Brainstem is a primitive portion of brain– Pons: involved in respiration, sleep

regulation, dreaming– Medulla: involved in life support functions

such as respiration and heart rate– Reticular activating system is an arousal

system within the brainstem


Subcortical Brain Areas

• Corpus callosum: band of axons that interconnects the hemispheres

• Thalamus: sensory relay area

• Limbic system: involved in emotionality

• Hypothalamus: feeding, fleeing, mating, fighting, homeostasis

• Cerebellum: involved in motor control


Limbic System: Seat of Motivation, Emotions


Limbic System


Cerebral Cortex


Cerebral Cortex• Cortex refers to the outer covering of the brain

– Consists of left and right hemispheres

– Cortex is divided into lobes• Frontal: Self-awareness, planning, voluntary movement,

emotional control, speech, working memory• Parietal: Body sensations• Occipital: Vision• Temporal: Hearing, language comprehension

– Localization of function: do discrete circuits carry out different functions?


Cortical Lobes


Language areas: Broca & Wernicke


LeDoux’s two pathways of emotion


Summary of Hemispheric Specializations


Motor and Somatosensory Cortex


Split-Brain Research

• When a split-brain patient is asked to stare straight ahead while a photo of a fork is flashed to his left visual field, he cannot name it.


Split-Brain Research


Behavioral Genetics• Behavioral genetics examines the influence of

genes (versus environment) on behavior• Research strategies:

– Twin studies: compare the concordance (agreement) rates between identical and fraternal twins

– Adoption studies: compare the similarity between adopted children and their biological/adopted parents

– Mutations: examine behaviors in genetically abnormal subjects or in animals in which a specific gene has been “knocked out”


Evolutionary Psychology

• Darwin argued that natural forces select traits that are adaptive for survival– Natural selection: certain traits are passed on

because these traits gave an advantage for survival

• Organisms with these traits are able to reproduce and pass on the trait to their offspring

– Genetic mutations can be beneficial or disastrous

• Evolutionary psychology examines how evolutionary processes impact behavior

© 2004 john wiley & sons, inc. huffman: psychology in action, 7e the nervous system

Documents

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spinal cord slide

relaxed slide

pain slide

structure slide

peripheral ns slide

autonomic nervous system

action potential