What is the function of the nervous system?
To integrate and control the other body systems through the activities of the central and peripheral nervous systems. The nervous system receives and processes information and sends out signals to the muscles and glands to elicit an appropriate response.
What structures constitute the Central nervous system? And what structures protect them?
The brain and the spinal cord, protected by the skull and the vertebrae, respectively.
How do the central nervous system and the peripheral nervous system interact?
The central nervous system can send/receive signals from the peripheral nervous system, which connnects all parts of the body to the central nervous system.
What does the peripheral nervous system consist of ?
All the nerves of the body that are in the brain or the spinal cord. The peripheral nervous system includes the cranial nerves and(spinal nerves)
2 divisions of the peripheral nervous system
The motor/efferent and the Sensory/afferent
Describe the movement of nerve impulses in the peripheral nervous system.
The peripheral nervous system receives impulses from the sensory organs through the sensory/afferent division and then relays impulses/signals to muscles/glands from the central nervous system through the motor/efferent division.
2 divisions of the efferent division of the peripheral nervous system
Somatic and Autonomic
What does the somatic and autonomic nervous system respectively control?
The somatic nervous system controls the skeletal muscles, joints and skin. The autonomic nervous system controls the smooth muscles of internal organs and the gland.
2 Divisions of the autonomic nervous system
Sympathetic and Parasympathetic
What is the function of the sympathetic nervous system?
The sympathetic nervous system activates and prepares the body for vigorous muscular activity, stress, and emergencies.
What is the function of the parasympathetic nervous system?
The parasympathetic system lowers activity, operates during normal situations, permits digestion, and conserves energy.
List 3 unusual characteristics of neurons.
Neurons (nerve cells) do not undergo mitosis and can last a lifetime.
Can live only for minutes without oxygen
Vary in size and shape
need large amounts of fuel
Descrive the structure and function of the neuron cell body?
The neuron cell body contains all the organelles found in other body cells, except for centrioles, since nerve cells do not undergo mitosis. The cell body synthesizes all nerve cell products.
The cell body produces neurotransmitters which are sent to the axon terminals. These neurotransmitters relay signals across the axon terminal to the dendrites of adjacent cells.
What are the 3 parts of a neuron?
The dendrites, the cell body and the axon
Structure and function of the dendrite
The dendrite are short, branchlike extensions from the cell body that receive information from adjacent nerve cells while conducting these impulses towards the cell body.
Descrive the axon
There is a single axon in each neuron. Axons serve to transmit the signal away from the cell body to the axon terminals and to the dendrites of other nerve cells.
The axon consists of cells similar to the cell body but they lack rough endoplasmic reticulum, so they must depend on the cell body for all necessary proteins.
Composition and function of Schwann cells
Schwann cells are composed mostly of a white fatty layer called the myelin shealth, which is wrapped around the axon. Myelin shealths provide insulation of the nerve fiber and increases the speed of nerve impulses.
Where are the Nodes of Ranvier located and what is their function?
Nodes of Ranvier are located between each myelin shealth on the axon. It is a gap between adjacent Schwann cell insulating sections. At these points the nerve impulse is forced to jump the gap. This increases the speed of the nervous impulse
What important organelle is absent from the neuron cell body and what does the absence of this organelle indicate about activity of the cell body?
The absence of centrioles indicates that there is no cell division activity. Mitosis is not undergone by nerve cells.
What are neurotransmitters?
One of the main functions of the cell body is to manufacture neurotransmitters, which are chemicals stored in secretory vesicles at the end of axon terminals. When neurotransmitters are released by the axon terminal vesicles, they participate in the transmission of the nerve impulse from one neuron to another.
What does a nerve consist of ?
A nerve consists of hundreds of thousands of axons wrapped together in a connective tissue.
What does "ganglia" refer to ?
What about neuroglial cells ?
In the peripheral nervous system the cell bodies of neurons are grouped together in masses called ganglia which are part of a single nerve. The neurons are also accompanied by non-nerve "supporting" cells known collectively as neuroglial cells which include oligodendrocytes, astrocytes, ependymal cells and microglial cells.
What are each of the functions for the non nerve supporting cells AKA the neuroglial cells?
The functions of these supporting cells are as follows: ependymal cells (circulate cerebrospinal fluid and allow fluid exchange between brain, spinal cord and CSF), oligodendrocytes (insulation of central nervous system axons), astrocytes (control chemical environment of neurons) and microglial cells (protect CNS by scavenging dead cells and infectious microoganisms).
How can neurons be classified ?
According to their structure and function
Neurons classified according to structure ?
Structurally, neurons are classified according to the number of extension from their cell body, as multipolar, bipolar and unipolar neurons. Multipolar neurons, the most common type in humans found as motor neurons or interneurons within the CNS, have three or more extensions, one axon and many dendrites. Bipolar neurons, found as receptors cells in the visual and olfactory systems, have two extensions, one axon and one dendrite. Unipolar neurons, found as sensory neurons in the peripheral nervous system, have one extension which branches into two, one central process running to the CNS and another peripheral process running to the sensory receptor.
How are neurons classified according to function ?
Functionally, neurons are classified as sensory or afferent neurons, motor or efferent neurons and association or interneurons. Most sensory neurons are unipolar and carry impulses from receptors in the skin or internal organs toward the CNS. Most motor neurons are multipolar and carry impulses from the central nervous system to muscle fibers or glands. Interneurons are usually multipolar and found within the central nervous system only. They transmit impulses between sensory and motors neurons conveying messages between various parts of the central nervous system, such as from one side of the brain or spinal cord to the other, or from the brain to the spinal cord, and vice versa.
What is the technical term used to describe a nerve impulse and what causes the impulse?
A nerve impulse is called an action potential and is caused by the movement of unequally distributed ions on either side of an axon’s plasma membrane.
An axon's membrane is polarized with a resting potential of -70 mV. Explain what this means and what maintains this resting potential.
The axon plasma membrane is polarized, meaning that one side has a different charge than the other side. This difference called a resting potential means that the charge on the inside of the axon's cell membrane is 70 millivolts less than the outside of the membrane. A sodium- potassium pump using active transport carries ions across the plasma membrane and because three Na+ ions are pumped out as two K+ ions are pumped in a relative positive charge develops and is maintained on the outside of the membrane
Stages of the Action Potential
1. Resting Potential
Describe what happens to the charges on the axon cell membrane during depolarization and what causes this to happen
During the resting phase both sodium and potassium gates that control the relative charges on sides of the membrane are closed. During depolarization the sodium gates open and sodium rushes into the axon and the inside becomes more positive than the outside causing the membrane potential to become more positive.