Biology Week 28 - Nervous System & Drugs

Day 1 - 2 | Day 3 | Day 4 | Lab 1 | Lab 2 | Weekly Quiz |

  • Nervous system
  • Neuron
  • Dendrite
  • Axon
  • Synapse
  • Nerve
  • Central nervous system
  • Brain
  • Cerebrum
  • Frontal lobe
  • Parietal lobe
  • Temporal lobe
  • Occipital lobe
  • Cerebellum
  • Brain stem
  • Midbrain
  • Medulla oblongata
  • Pons
  • Limbic system
  • Thalamus
  • Hypothalamus
  • Reticular formation
  • Cranial nerves
  • Spinal nerves
  • Dura mater
  • Arachnoid layer
  • Pia mater
  • Peripheral nervous system
  • Ganglion
  • Receptors
  • Conductors
  • Effectors
  • Somatic nervous system
  • Autonomic nervous system
  • Resting state
  • Depolarization
  • Repolarization
  • Neurotransmitters
  • Refractory period
  • Touch
  • Hearing
  • Smell
  • Taste
  • Sight
  • Fingerprint
  • Drug
  • Stimulant
  • Depressant
  • Narcotic
  • Hallucinogen
  • Inhalant
  • Drug abuse
  • Drug addiction
  • Psychological
  • Physical
  • Tolerance
  • Withdrawal
  • Controlled substance

The Nervous System

Can you solve the puzzle?

click to find the answer to today's question What is the gap between nerve cells called?

Read standardized test practice passage #15link to a local webpage and answer the questions.
You have eight minutes to complete the assignment.


A neuron showing the dendrites, cell body, axon, and axon terminals

Neurons link to an Internet Website the cells composing the nervous system.
There are more than 10 billion nerve cells in the human body.

Neurons are composed of:

click for a career
Registered Nurse
Nerves link to an Internet Website groups of related neurons.

Your body contains nerves of different sizes link to a local picture
that carry nerve impulses at different speeds.

Nerves are organized into two major subsystems in your body:

The central nervous system:

The human brain: link to an Internet Website link to an Internet Website link to a local picture

Your brain contains about 1 X 10 11 neurons, making up about 2% of your body weight and using 20% of your body's oxygen. The cortex of the brain is folded into grooves and bumps which increase the surface area of the brain. The total surface area of the brain's cortex is about the same as a full size sheet of newspaper.

The Human Brain Cerebrum:

Cerebellum: Brain stem: Other structures inside the brain: link to an Internet Website

12 cranial nerves link to an Internet Website connecting the brain directly to the other organs of the head.

The spinal cord: link to an Internet Website composed of a column of nerve tissue through the vertebral column.

There are 32 pairs of spinal nerves connecting the spinal cord to the Peripheral Nervous System.

The brain and spinal cord are surrounded by 3 protective layers called meninges:

The peripheral nervous system:

Nerves that connect the central nervous system to the rest of the body.

Somatic nervous system - controls voluntary movement of the skeletal muscles.

Autonomic nervous system link to an Internet Website controls involuntary actions.

How impulses move through nerves:

Impulses move from one nerve cell to another because of a difference in electrical "action potential" caused by ions inside and outside the cell. The cell membrane is selectively permeable to K+ and highly impermeable to Na+.

To simplify the process, think of the following steps:

  1. Resting state:
    • A neuron is not conducting an impulse.
    • The K+ concentration is much higher inside the cell than out.
    • The Na+ concentration is much higher outside the cell than in.
  2. Depolarization:
    • A nerve cell is stimulated.
    • At the point of stimulation, the membrane becomes permeable to Na+ for an instant and they quickly move into the cell.
    • The inner surface of the cell membrane is now more positively charged than the outside.
  3. Repolarization:
    • When the cell membrane becomes depolarized, K+ automatically leave the cell until the cell is back to its resting state.
  4. The impulse travels:
    • This quick movement of ions causes a similar change or wave all across the cell and down the axon.
    • Vertebrate nerves are covered by a myelin sheath with openings called Nodes. The myelin sheath is an insulator and causes the ion exchange to occur only at the nodes which speeds up the process.
  5. Transmission across a synapse:
    • Neurons to not actually touch. The axon terminals of one neuron stop before reaching the dendrite of the next neuron. This gap between the two cells is called a Synapse.
    • Impulses are carried across a synapse by chemical messengers called neurotransmitters.
    • Approximately 30 different neurotransmitters have been identified, but they all do one of two things:
      1. Stimulate the action potential in a second cell.
      2. Inhibit the action potential in the next cell.
  6. Refractory period:
    • The period of time it takes a neuron to return to its resting potential after being stimulated.
    • A neuron cannot be stimulated during this period.
    • This period of time is about 0.0004 of a second.

Test yourlink to an Internet Websitereaction time.

Play Neurosciencelink to an Internet WebsiteHangman.


T h e   F i v e   S e n s e s   link to an Internet Website

The sense of touch is associated with the skin. link to an Internet Website link to a local picture Different areas of the body have different numbers of touch receptors.
  • This diagram link to a local picture shows the areas of the brain responsible for touch. The size of the hands in this drawing indicates a large number of receptors.
  • There is a relationship between touch and pain. link to an Internet Website
Lab # 2
No two people have exactly the same fingerprints, but there are only seven basic types. link to a local picture
This diagram link to a local picture shows the three parts of the ear. link to an Internet Website
  • Your ear can distinguish more than 300,000 tones.
  • For more information. link to an Internet Website
This diagram link to a local picture shows the olfactory region of the nose link to an Internet Website and brain.
  • For more information. link to an Internet Website
This diagram link to a local picture shows the location of taste areas on the tongue. link to an Internet Website
  • For more information. link to an Internet Website link to an Internet Website





Can you solve the puzzle?

Together, your eyes link to an Internet Website produce a sterioscopic view of the world. link to a local picture
Study this diagram of the workings of the human eye. link to a local picture

In the diagram above, notice the exit of the optic nerve to the brain. Any light falling directly on this point does not stimulate the retina, making this point blind. You can use the figure below to demonstrate the blind spot. Cover your right eye. Look at the "+" with the left eye and move your head toward or away from the screen. Although you are looking at the plus mark, concentrate on the spot. At some point in your head movement, the spot will disappear ... it is being projected onto the area of the blind spot where the optic nerve exits the retina. Since the blind spot in each eye is not aimed at the same spot, their images do not overlap. If you uncover your right eye, the spot is projected onto the retina of that eye and you "see" it.

blind spot
  • Your eye can distinguish nearly 8 million different colors.
  • Blinking causes your eyes to be closed 30 minutes every day.
  • For more information. link to an Internet Website link to an Internet Website
The brain must interpret the messages sent to it by your eyes. Because of this, the brain can be fooled by these messages. link to an Internet Website
  • There are no curved lines in the picture. link to a local picture
  • Neither of these objects can exist. link to a local picture link to a local picture
  • Use this website to check your color vision. link to an Internet Website
  • Use this website to learn about stys. link to an Internet Website


Day 1-2 Assignment - Nervous System & Drugs (Test Your Concept Understanding)

  1. What are the two possible actions of neurotransmitters?
  2. How fast can nerve impulses move in your body?
  3. What part of the brain is responsible for sleep?
  4. Look closely at the diagram of vision on this page. Why don't we see things upside down?
  5. What is the largest portion of the brain?
  6. Study this webpage about the basic concepts of the sense of touch. link to an Internet Website
    1. Our skin recognizes several different types of tactile or "touch" sensations. List five types.
    2. Write a paragraph explaining the difference between rapidly-adapting receptors and slowly-adapting receptors.
    3. The fingertips can discriminate two points touching the skin only 2 or 3 millimeters apart while the skin on the back can discriminate two points no closer than 35 to 40 millimeters apart. What two properties of the touch receptors are responsible for this difference?

Research Links:

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The gap between nerve cells is called a synapse.