Chapter 2 Outline: The Biological Basis of Behavior
Hemispherectomies: the removal or the left or right half of the brain. (often used to treat seizures). Improves speech, coordination, ect. The internal environment of the brain is often calmer and their external environment is enhanced and better. The brain is the “master control” of all the body’s functions. Our brains have billions of cells that make up pathways, networks, and back-up systems. The two sides of the brain are similar but NOT identical.
The human brain has plasticity: the ability to adapt to new environmental conditions. The brain responds and changes. (kind of like homeostasis). Psychobiology: the branch of psychology that deals with the biological bases of behavior and mental processes. Neurons: nerve cells
Nervous system central nervous system/peripheral nervous system and the endocrine system which sends messages through the blood. I. Neurons: The Messengers
a. The average human being has 100 billion nerve cells or neurons. b. Neurons are specialized to receive and transmit information. c. Neuron’s cell body is made up of a nucleus, cytoplasm, and the cell membrane. d. All around the neuron are dendrites: short fibers that branch out from the cell body and pick up incoming messages. e. Axon: a single long fiber extending from the cell body; it carries outgoing messages nerve or tract: a bunch of axons bundled together.
Covered by a myelin sheath: white fatty covering found on some axons. “microscopic sausages” Unmyelinated axons are called grey matter.
Provides insulation so information does not interfere with certain neurons and increases the speed at which they are sent. f. Sensory or afferent neurons: neurons that collect messages from sense organs and carry those messages to the spinal cord or brain. g. Motor or efferent neurons: neurons that carry messages from the spinal cord or the brain to the muscles and glands. h. Interneuron or association neurons: neurons that carry information from one neuron to another. i. Glial cells or glia: hold the neurons in place and provide nourishment and remove waste products. Also form the myelin sheath. 1. The Neural Impulse
a. When a neuron is resting, the membrane surrounding the cell forms a barrier between the fluids that are inside and outside of the neuron. Contain ions which are electrically charged particles found on the inside and outside of a neuron. b. Resting potential: more negative ions on the inside than the outside. State of polarization: the condition of a neuron when the inside is negatively charged relative to the outside; when the neuron is at rest. c. Depolarization occurs when the cell membrane is stimulated by an incoming message and pores in the membrane allow the sudden flow of positively charged sodium ions. Sets off a chain reaction
d. Neural impulse/ Action potential: the firing of a nerve cell, travels down the axon. e. Axons with myelin sheaths have quicker reactions than neurons without them. f. Single impulses to do NOT make a neuron fire. They cause a temporary charge called a graded potential. Threshold of excitation: the level an impulse must exceed to cause a neuron to fire. All or none law: neuron either fires at full strength or not at all. Absolute refractory period: a thousandth of a second the neuron will not fire again. Relative refractory period: cell is returning to the resting state, the neuron will fire, but only if the incoming message is stronger than normal. g. A neuron is in touch with hundreds or thousands of other cells at both the dendrites and axon. 2. The Synapse
a. Neurons are separated by a tiny gap called a synaptic space or synaptic cleft. b. Terminal button or synaptic knob: structure at the end of an axon terminal branch. c. Synapse: area composed of the axon terminal of one neuron, the synaptic space, and the dendrite or cell body of the next neuron. For an impulse to move it must cross the synaptic space.
d. Synaptic vesicles: tiny...
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