The Biological Foundations of Behavior

• The nervous system: the most complicated system in human body where billions of interconnected cells radiate all over the body.

• Specialized Cells of nervous system include:

1. Receptor cells: Embedded in sense organs, (seeing – hearing – smelling – tasting – touching). receive various types of stimulation from environment, which are then transmitted to the brain.

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2. Effector cells: Brain sends motor signals to the effector cells embedded in muscles and glands.

3. Neurons: Specialized to conduct signals from one part to another, (connect receptor cells to effector cells).

4. Nerve: long, fibrous parts of many neurons bundled together, and run through the bodies.

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Division of nervous system:

• 1- Central Nervous System (CNS): consists of brain and spinal cord.

• 2-Peripheral Nervous System (PNS): Branching out from the CNS and leading to all parts of the body.

•  Neurons from PNS convey signals from receptor cells to the spinal cord and brain (afferent pathway).

• neurons transmit messages from brain and spinal cord to effectors cells (efferent pathway).

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• *Efferent pathway has two divisions:

• Somatic nervous system: it controls actions that are under voluntary control.

• Autonomic nervous system: control muscles of internal organs ( the heart, intestine, blood vessels) and glands, usually automatic or involuntary.

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• Autonomic nervous system has two divisions: (opposite effects).

a. Sympathetic nervous system:

• In emergency situations as meeting a snake, lead to increase blood sugar, heart rate and blood pressure, and inhibiting digestion (Fight- Flight- Fright response)

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b. Parasympathetic Nervous System:

•-Dominates under relaxation conditions and tends to conserve body's energy.

•-After eating large meal, it works to aid digestion, at the same time decreasing heart rate and blood flow to skeletal muscles

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Division of the nerves system(Look in your book please)

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Composition of neuron cell:

• A- Cell body: the life support center of the cell.

• B- Dendrites: receive messages transmitted from other neurons (antenna of neurons).

• C- Axons: carries neural signals to affect the muscle fibers

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Types of neuron

1- Sensory neurons: carry information form sense organs to the brain & spinal cord.

2-Motor neurons: carry signals from brain and spinal cord to muscles and glands.

3-Inter-neurons: connect neuron to other neurons .

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Brain• Structurally the brain is divided into the

cerebrum, cerebellum, brain stem, and limbic system.

• (1) CEREBRUM

• The cerebrum is divided into two hemispheres:

• (2) CEREBELLUM: center for coordination of movements and postural adjustments.

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(3) Brain Stem: Includes the midbrain, Pons, and medulla oblongata.

•Medulla oblongata: contains vital centers for respiration and cardiovascular functions.

(4) Limbic System: located above the brain stem that includes:

- The hypothalamus is involved in temperature regulation, appetite control, endocrine function…etc.

•  Hippocampus is involved in emotional arousal and memory.

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Neurotransmission:

- Neurons communicate information with one another by sending electrochemical messages from neuron to neuron.

•Neurotransmitters:

- Chemical substances manufactured in the neuron, aid in the transmission of information throughout the body.

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Major Neurotransmitters in Psychology

1-Dopamine:(excitatory).

-Control of complex movements, motivation, cognition, and regulation of emotional responses.

2 Nor epinephrine (Noradrenalin) :

•plays a role in changes in attention, learning and memory, sleep and wakefulness, and mood regulation.

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Major Neurotransmitters in Psychology…cot.

3- Epinephrine (adrenaline):

- Controls fight-or-flight response in anxiety disorders.

4- Serotonin: (inhibitory):

- Control of sleep ,wakefulness, emotions and sexual behavior.

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Major Neurotransmitters in Psychology…cot.

5- Gamma-Amino Butyric Acid (GABA):

- Drugs that increase GABA function used to treat anxiety and induce sleep.

 

6- Acetylcholine: (excitatory or inhibitory).

- affect the sleep/wake cycle and to signal muscles to become active.

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Sensation and Perception• Sensation:

(The process where by stimulation of receptor cells like eye, nose, ear …etc., send nerve impulses to the brain, where they register a touch, sound, color …etc).

• Perception:

- (process where the brain interprets sensation giving them order and meaning).

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Sensation and Perception…cont.

- Without sensation: perception couldn’t occur, without perception sensations without meaning.

- Impaired perception cause (illusion).

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Stimulus

(Any form of energy (sound, light, heat, and pressure) to which an organism is capable of responding).

•Stimuli and sensation have a cause and effect relationship.

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Factors affects stimulus detection:

- (1) The intensity of stimulus.

- (2) Background noise interfere with stimulus detection.

- (3) Motivation (rewards or punishments).

-(4) Prolonged constant stimulation: lead to sensory adaptation.

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How do perceptual processes develop?

1. Empiricist view of perceptual development:

- Babies enter the world with little or no ability to see depth, form, and perceptual constancy’s.

- Infants learn adult like perceptions on the basis of cues the environment provides.

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2. Nativist view of perceptual development:

•Not all perceptual process are learned, some arise from the way our sensory system work, e.g. feeling of hunger or diaper wetting.

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• 3- Interactionism view of perceptual development:

- Through the interaction of both biological factors & experience perceptual process develop.

- what we see, hears, feel, and so forth, is partly the results of how our sensory systems are programmed and partly the result of what we are exposed to.

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Expectations and perceptions

• Psychologists have studied two ways in which learning and experience mold our expectations which in turn shape our perception

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1-Perceptual set:

- A frame of mind that “sets” a person to perceive things in a certain way.

- We perceive what we think we should perceive.

- Perceptual sets establish expectations that guide our perception

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* Example (illusion): person who was bitten by snake in the dark in specific area. The sight of snake become a perceptual set for this person. When he see a rope in the same area under similar conditions establish an expectation of snake this expectation guide his perception, so he perceive the rope as a snake.

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• 2- Perceptual schema:

• Mental representation of objects and events against which incoming data are compared and interpreted. 

- General knowledge of the world in the form of schemas also shape our expectations and hence our knowledge.

- Example: How quickly people process the information in photos with a real world scenes as a city street or a kitchen. When people view such scenes for only a second, they can remember almost half of the objects that scenes contain.

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