Biological Bases of Behavior

Topics: Nervous system, Neuron, Brain Pages: 11 (1677 words) Published: November 19, 2013
1. Biological psychologists are gaining a better understanding of our experiences of sights and

sounds, meanings and memories, pain and passion. Franz Gall invented phrenology, a popular

theory that claimed that bumps on the skull reveal our mental abilities and our character traits.

Although wrong, this information revealed that various brain regions have specific functions.

2. A neuron consists of a cell body and branching fibers:The dendrite fibers receive information

from sensory receptors or other neurons, and the axon fibers pass that information along to other

neurons. Sensory neurons send information from the body’s tissues and sensory organs inward

to the brain and spinal cord, which process the information. Motor neurons carry outgoing

information from the central nervous system to the body’s tissues.Interneurons in the central

nervous system communicate internally and intervene between the sensory inputs and the motor

outputs. The axons of some neurons are encased by a myelin sheath, which helps speed their

impulses. A neural impulse, or action potential, fires when the neuron is stimulated by signals

from the senses or when triggered by chemical signals from neighboring neurons. Received

signals trigger an impulse only if the excitatory signals minus the inhibitory signals exceeds a

minimum intensity called the threshold. The neuron’s reaction is an all-or-none response. During

the resting potential, the fluid interior of the axon carries mostly negatively charged atoms(ions),

while the fluid outside has mostly positively charged atoms.Then, the first bit of the axon is

depolarized (its selectively permeable surface allows positive ions in), and the electrical impulse

travels down the axon as channels open, admitting ions with a positive charge. When these

channels close, others open and positive ions are pumped back out, restoring the neuron to its

polarized state.

3. When electrical impulses reach the axon terminal, they stimulate the release of chemical

messengers called neurotransmitters that cross the junction between neurons called the

synapse. After these molecules traverse the tiny synaptic gap (cleft) between neurons, they

bind to receptor sites on neighboring neurons, thus passing on their excitatory or inhibitory

messages.The sending neuron, in a process called reuptake, normally absorbs the excess

neurotransmitter molecules in the synaptic gap.

4. The brain’s endorphins, natural opiates released in response to pain and vigorous exercise,

explain the “runner’s high” and the indifference to pain in some injured people.

When the brain is flooded with opiate drugs such as heroin and morphine, it may stop producing

its own natural opiates, and withdrawal of these drugs may result in intense discomfort until the

brain resumes production of its natural opiates.

5. Neurons communicating with other neurons form our body’s primary system, the nervous

system. The brain and spinal cord form the central nervous system (CNS).The peripheral nervous

system (PNS) links the central nervous system with the body’s sense receptors, muscles, and

glands.The axons carrying this PNS information are bundled into the electrical cables we know

as nerves. The somatic nervous system of the peripheral nervous system enables voluntary

control of our skeletal muscles.The autonomic nervous system of the peripheral nervous system

is a dual self regulating system that influences the glands and muscles of our internal organs.The

sympathetic nervous system arouses; the parasympathetic nervous system calms. Reflexes,

which are simple, automatic responses to stimuli, illustrate the spinal cord’s work.

6. The endocrine system’s glands secrete hormones, chemical messengers produced in one tissue

that travel through the bloodstream and affect other tissues, including the brain. In a...
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