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

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

Neurons the cells composing the nervous system.
There are more than 10 billion nerve cells in the human body.

Neurons are composed of:

A cell body containing the nucleus. Two types of threadlike extensions: Dendrites - fingerlike projections from the cell body that receive impulses from other neurons and carry them to the cell body. Axon - an elongated extension of the cell body that carries impulses away from the cell body. The end of the axon is divided into fingerlike projections called axon terminals.

Registered Nurse

Nerves groups of related neurons. Your body contains nerves of different sizes that carry nerve impulses at different speeds.

Nerves are organized into two major subsystems in your body:

The central nervous system:

The human brain:

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.

Cerebrum:

• Contains 75% of your neurons.
• Composed of two equal hemispheres.
  • Frontal lobe reasoning, speech, movement, and emotions
  • Parietal lobe touch, pressure, temperature, and pain
  • Temporal lobe hearing and memory
  • Occipital lobe vision
• All cerebrum function areas

• Located at the lower back of the head.
• Controls muscle coordination and balance.

• Connects the cerebrum with the spinal cord.
• The 3 main sections of the Brain Stem:
  • Midbrain - controls reflexes and changes pupil size.
  • Medulla oblongata - controls heart rate, breathing rate, and flow of blood through the blood vessels.
  • Pons - relays signals between the cerebrum and the cerebellum.

• The limbic system - composed of the Thalamus and Hypothalamus. These structures work together to regulate emotions.
• The reticular formation - a network of nerves running through the brain stem and the thalamus. These nerves filter incoming sensory impulses, enabling a person to sleep.

12 cranial nerves connecting the brain directly to the other organs of the head.

The spinal cord: 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 dura mater (outer layer): consists of connective tissues, blood vessels, and nerves.
• The arachnoid layer (middle layer): elastic and weblike.
• The pia mater (inner layer): contains nerves and blood vessels.
• Cerebrospinal fluid, a clear watery liquid, separates the middle and inner layers and cushions the brain and spinal cord from shock.

The peripheral nervous system:

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

• Ganglion - a mass of nerve cells outside the central nervous system.
• Receptors - nerve cells that receive information from internal and external stimuli.
• Conductors - nerve cells that transmit information from receptors to the central nervous system.
• Effectors - nerve cells that receive information from the central nervous system and transmit to the body. These cells activate muscles and glands.

Autonomic nervous system controls involuntary actions.

• Sympathetic Nervous System - controls internal organs during high stress activity.
• Parasympathetic Nervous System - controls internal organs during normal activity.

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:

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. 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. Repolarization: When the cell membrane becomes depolarized, K+ automatically leave the cell until the cell is back to its resting state. 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. 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: Stimulate the action potential in a second cell. Inhibit the action potential in the next cell. 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 yourreaction time.

Play NeuroscienceHangman.

T h e   F i v e   S e n s e s   The sense of touch is associated with the skin. Different areas of the body have different numbers of touch receptors. This diagram 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. Lab # 2 No two people have exactly the same fingerprints, but there are only seven basic types. This diagram shows the three parts of the ear. Your ear can distinguish more than 300,000 tones. For more information. This diagram shows the olfactory region of the nose and brain. For more information. This diagram shows the location of taste areas on the tongue. For more information.         Together, your eyes produce a sterioscopic view of the world. Study this diagram of the workings of the human eye. 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. Your eye can distinguish nearly 8 million different colors. Blinking causes your eyes to be closed 30 minutes every day. For more information. The brain must interpret the messages sent to it by your eyes. Because of this, the brain can be fooled by these messages. There are no curved lines in the picture. Neither of these objects can exist. Use this website to check your color vision. Use this website to learn about stys.

Day 1-2 Assignment - Nervous System & Drugs (Test Your Concept Understanding) What are the two possible actions of neurotransmitters? How fast can nerve impulses move in your body? What part of the brain is responsible for sleep? Look closely at the diagram of vision on this page. Why don't we see things upside down? What is the largest portion of the brain? Study this webpage about the basic concepts of the sense of touch. Our skin recognizes several different types of tactile or "touch" sensations. List five types. Write a paragraph explaining the difference between rapidly-adapting receptors and slowly-adapting receptors. 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:

• TeensHealth - The Nemours Foundation
• Medical Dictionary - MedicineNet
• Anatomy Links - DV Biology
• Health Links - DV Biology
• Sensory Anatomy - George Washington University
• Human Brain Dissection - University of Iowa
• The Human Brain - Marymount College
• The Spinal Cord - Global Anatomy
• Vertebrate Nervous System - George Washington University
• Spinal Cord Injuries - Science On The Edge
• Nervous System - University of Kansas Medical Center
• Nervous System Images - University of Virginia
• Neuroanatomy Links - University Medical School, Debrecen, Hungary
• Embryo Development - University of Pennsylvania Health System
• Cerebrovascular Center - The Cleveland Clinic Foundation
• Neuroscience For Kids - University of Washington
• The ChemoReception Web - - Links compiled by Frederic A. Spangler, Ph.D.

The gap between nerve cells is called a synapse.