chap 2 biology

• neurons 


  a specialized cell of the

  nervous system that receives and

  transmits messages
• glial cells


  cells that remove dead

  neurons and waste products from the

  nervous system, nourish and insulate

  neurons, form myelin, and play a role

  in neural transmission of messages
• dendrites 


  root-like structures,

  attached to the cell body of a neuron,

  that receive impulses, or incoming

  messages, from other neurons
• axon


  a long, thin part of a neuron

  that transmits impulses to other

  neurons from bulb-shaped structures

  called axon terminals or terminal

  buttons
• myelin 


  a fatty substance that

  encases and insulates axons,

  facilitating transmission of neural

  impulses
• afferent neurons 


  neurons that

  transmit messages from sensory

  receptors to the spinal cord and

  brain; also called sensory neurons
• efferent neurons 


  neurons that

  transmit messages from the brain or

  spinal cord to muscles and glands;

  also called motor neurons
• neural impulses 


  the

  electrochemical discharge of a nerve

  cell or neuron
• polarize 


  to ready a neuron for

  firing by creating an internal negative

  charge in relation to the body fluid

  outside the cell membrane
• resting potential


  the

  electrical potential across the neural

  membrane when it is not responding

  to other neurons
• depolarized 


  to reduce the

  resting potential of a cell membrane

  from about 70 millivolts toward zero
• action potential 


  the electrical

  impulse that provides the basis for

  the conduction of a neural impulse

  along an axon of a neuron
• all or non principle 


  the fact

  that a neuron fires an impulse of the

  same strength whenever its action

  potential is triggered
• refractory period 


  a phase

  following firing during which a

  neuron is less sensitive to messages

  from other neurons and will not fire
• synapse 


  a junction between the

  axon terminals of one neuron and

  the dendrites or cell body of another

  neuron
• neurotransmitters 


  chemical

  substances involved in the

  transmission of neural impulses from

  one neuron to another
• receptor site


  a location on

  a dendrite of a receiving neuron

  tailored to receive a neurotransmitter
• acetylcholine


  a neurotransmitter that controls

  muscle contractions
• hippocampus 


  a structure of

  the brain that is involved in memory

  formation
• dopamine


  a neurotransmitter

  that affects the ability to perceive

  pleasure, voluntary movement, and

  learning and memory; it is involved

  in Parkinson’s disease and appears to

  play a role in schizophrenia
• norepinephrine 


  a

  neurotransmitter whose action

  is similar to that of the hormone

  epinephrine and that may play a role

  in depression
• 1. hypothalamus 2. cerebellum 3. hippocampus 4. prefrontal cortex 5. pituitary gland 6. amygdala 7. brain stem

  
• serotonin 


  a neurotransmitter

  involved in emotional arousal and

  sleep; deficiencies of serotonin have

  been linked to eating disorders,

  alcoholism, depression, aggression,

  and insomnia
• gamma-aminobutyric

  acid (GABA)


  inhibitory

  neurotransmitter that apparently

  helps calm anxiety
• endorphils 


  inhibitory

  neurotransmitters that occur

  naturally in the brain and in the

  bloodstream and are similar to the

  narcotic morphine in their functions

  and effects
• nerves 


  a bundle of axons from

  many neurons
• central nervous system


  the brain and spinal cord
• peripheral nervous system 


  the part of the nervous system consisting

  of the somatic nervous system and the

  autonomic nervous system
• somatic nervous system


  the

  division of the peripheral nervous system

  that connects the central nervous system

  with sensory receptors, skeletal
• autonomic nervous system 


  the division of the peripheral

  nervous system that regulates glands and

  activities such as heartbeat, respiration,

  digestion, and dilation of the pupils
• sympathetic division 


  the branch

  of the ANS that is most active during

  emotional responses, such as fear and

  anxiety, that spend the body’s reserves

  of energy
• parasympathetic division


  the

  branch of the ANS that is most active during

  processes (such as digestion) that restore

  the body’s reserves of energy
• spinal cord 


  a column of nerves

  within the spine that transmits

  messages from sensory receptors

  to the brain and from the brain to

  muscles and glands throughout

  the body
• spinal reflex

  a simple, unlearned

  response to a stimulus that may

  involve only two neurons
• gray matter 


  the grayish neurons

  and neural segments that are

  involved in spinal reflexes
• white matter 


  axon bundles that

  carry messages to and from the brain
• electroencephalograph EEG 


  a method of detecting brain waves

  by means of measuring the current

  between electrodes placed on the scalp
• computerized axial tomography CT scan


  a method of brain imaging

  that passes a narrow X-ray beam

  through the head and measures the

  structures that reflect the beams from

  various angles, enabling a computer to

  generate a three-dimensional image
• positron emission tomography 


  a method of brain imaging that

  injects a radioactive tracer into the

  bloodstream and assesses activity of

  parts of the brain according to the

  amount of glucose they metabolize
• magnetic resonance imaging 


  an imaging

  method that places a person in a

  magnetic field and uses radio waves

  to cause the brain to emit signals

  that reveal shifts in the flow of blood,

  which, when the brain is being

  scanned, indicate brain activity