huffman chap 2 pp.ppt biological basis
TRANSCRIPT
Chapter 2Biological Foundations of
Behavior
Lecture Overview
• The Nervous System
• Neurons
• Neural Impulses
• The Brain
• The Spinal Cord
• The Endocrine System
• Genetics
The Nervous System
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
Neurons
• Neurons are cells that transmit information
• Neurons are composed of:– Dendrites: receive neural impulses and
pass it to cell body; information receiver– Cell Body: summarizes information– Axon: extends from cell body; sends
message to adjacent neurons; information sender
Neuron Structure
Neural Impulses:Neural Communication
• Within a neuron, communication occurs through an action potential (neural impulse that carries information along the axon of a neuron).
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.
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
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.
The Synapse
1. Synthesis of neurotransmitter (NT)
2. Storage and transport of NT within vesicles
3. NT Release4. Activation of
postsynaptic receptors5. Termination of
transmitter effect (e.g. reuptake)
Common Neurotransmitters and some of their functions
Acetylcholine (ACh)
• Activates motor neurons controlling skeletal muscles.
• Contributes to the regulation of attention, arousal, and memory.
• Some ACh receptors stimulated by nicotine
Dopamine (DA)• Contributes to control of voluntary movement,
pleasurable emotions.• Decreased levels associated with Parkinson’s
disease• Over activity at DA synapses associated with
schizophrenia • Cocaine and amphetamines elevate activity at
DA synapses
Norepinephrine (NE)
• Contributes to modulation of mood and arousal
• Cocaine and amphetamines elevate activity at NE synapses
Serotonin• Involved in regulation of sleep and
wakefulness, eating, aggression• Abnormal levels may contribute to
depression and obsessive compulsive disorder
• Prozac and similar antidepressant drug affect serotonin circuits
Endorphins
• Resemble opiate drugs in structure and effects
• Contribute to pain relief and perhaps to some pleasurable emotions
• “Runner’s high” may be associated with high endorphin levels
GABA (gamma-aminobutyric acid).
• Destruction of GABA – producing neurons in Huntington’s disease produces tremors and loss of motor control as well as personality changes.
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
Midline Brain View
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
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
Cortical Lobes
Motor and Somatosensory Cortex
Summary of Hemispheric Specializations
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
• CASE STUDY
• Phineas Gage was a railway worker in 19 th century Vermont who survived a bizarre accident: A metre-long iron rod shot through his head, changing him and the study of ...
• www.bbc.co.uk/radio4/science/case_study_20080521.shtml
The Spinal Cord
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
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”
Messinger
Chromosomes
In vitro Ordered by karotyping
Principles of Heredity Transmission
The Genetic Code
Conception is the moment of fertilization, when a sperm penetrates an ovum, forming a zygote.
• The zygote contains 46 chromosomes, consisting of thousands of chemical segments, or genes.
• Genes are hereditary blueprints for development that are passed on unchanged from generation to generation.
• Chromosomes come in matching pairs. (23 chromosomes from each parent.)
The 23rd pair of chromosomes• The sex of the zygote is determined by the 23rd pair of
chromosomes.• For a female sex, both of these sex chromosomes are an X
chromosome.• For a male sex, the 23rd pair consists of one X chromosome and one
Y chromosome.
The purpose of our genes…..• Our genes are responsible for the construction of our enzymes and
other proteins.• These genes are essential in order to form new cells and their
specific functions.• Other genes are accountable for regulating the pace of
development.
Normal human cells contain 23 pairs of chromosomes
During cell division we can identify chromosomes
• Haploid: set of 23 chromosomes• Diploid: normal number of 46 chromosomes• Aneuploidy: less than an even multiple of 23
usually is 45 or 47 and rarely 48,49• Triploidy: 69 chromosomes• Mosaicism• Abnormal in deletion and translocation
Chromosomal and Genetic Abnormalities
• DOWN SYNDROME (TRISOMY 21)
Down Syndrome
• Incidence 1/700• 2/3 of down fetus spontaneously abort• Trisomy 21 in 94% of cases with extra
chromosome from mother mostly(95%)• Risk correlate with maternal age
– <25 y/o 1/1600– >40 y/0 1/80
• 2% are mosaic
Chromosomal and Genetic Abnormalities
EDWARD’S SYNDROME (TRISOMY 18)
Chromosomal and Genetic Abnormalities
PATAU SYNDROME (TRISOMY 13)
Chromosomal and Genetic Abnormalities
TURNER SYNDROME (XO)
Chromosomal and Genetic Abnormalities
KLINEFELTER SYNDROME (XXY)
Chromosomal and Genetic Abnormalities
FRAGILE X SYNDROME
Chromosomal and Genetic Abnormalities
ANGELMAN SYNDROME
Chromosomal and Genetic Abnormalities
PRADER - WILLI SYNDROME
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