Overview of The Nervous System
Consists of two parts the Central Nervous System (CNS) and the Peripheral Nervous System (PNS). The CNS has two parts the brain and the spinal cord. The PNS are the rest of the nerves; cranial and spinal nerves, sensory and motor fibers, somatic and autonomic nervous, sympathetic and parasympathetic divisions. The CNS and PNS have three functions: reception of inputs, integration of the inputs (data) and generation of motor outputs.
Nervous Tissue
There are two types of nervous tissue; neurons (which transmit nerve impulses) and neuroglia (which nourish and support the neurons).
Neuron Structure
There are three parts to a neuron: dendrites, the cell body (which contains the nucleus) and the axon.
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The three types of neurons comprise the three functions of the nervous system. Sensory neurons take impulses from the sensory receptors to the CNS. The interneurons integrate the data within the CNS. And the motor neurons take impulses from the CNS to motor effectors.
Myelin Sheath
Is the protective fatty covering on long axons. It also helps with regeneration of these axons if they become severed. And also with conduction of impulses through salutatory conduction.
The Nerve Impulse
The nerve impulse happens when the cell momentarily changes polarity from a negative potential (resting state) to a positive potential (action state).
http://eleceng.ukc.ac.uk/~sd5/pics/research/big/actpot.gif.
The Synapse
The synapse is the junction between neurons. A nerve impulse is transmitted when a neurotransmitter is released into a synaptic cleft. Excitation or inhibition happens when a neurotransmitter binds to a receptor. Data integration happens when the input (excitation and/or inhibition) signals are received and processed.
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The CNS
The CNS has two parts the brain and the spinal cord. This is where integration and initiation of motor responses occurs.
The Brain
The parts of the brain are: the cerebrum, the diencephalon, the cerebellum, and the
brain stem.
The Cerebrum is the last center to receive sensory input, then integrates those
inputs and commands the appropriate motor response. It also coordinates and communicates with the other parts of the brain.
∙cerebral hemispheres - left and right halves connected by the corpus callosum.
∙each hemisphere is divided into four lobes
∙ Frontal lobe - which contains the primary motor area, premotor area
motor speech area, prefrontal area, and primary olfactory area.
∙ Temporal lobe - which contains the auditory association area, primary
auditory area, and sensory speech area.
∙ Parietal lobe - which contains the primary somatosensory area,
somatosensory association area, primary taste area, and the general
interpretation area.
∙ Occipital lobe - which contains the primary visual area and the visual
association area.
The Diencephalon contains the thalamus and the hypo-thalamus.
∙ The thalamus controls all sensory inputs to the cerebrum except for
smell.
∙ The hypo-thalamus helps maintain homeostasis by regulating hunger,
thirst, sleep, body temperature, and water balance. Also by controlling
the pituitary gland it can communicate with the endocrine and nervous
systems.
The Cerebellum coordinates skeletal muscles to produce smooth and graceful
motions.
The Brain stem helps regulate certain autonomic functions such as breathing,
heart rate, and blood pressure. It also contains the centers for coughing,
sneezing, vomiting, swallowing and hiccupping.
http://www.prs.k12.nj.us/schools/PHS/Science_Dept/APBio/pic/brain.gif.
The Spinal Cord
The spinal cord is the link between the PNS and the brain. It carries cerebrospinal
fluid and has gray and white matter. The spinal cord is also the center for
thousands of reflex arcs.
The Limbic System and Higher Mental Functions
Limbic System
The Limbic system involves two distinct structures that are tied to emotions, learning and memory. The two structures are the amygdala and the hippocampus. The amygdala is directly associated with the emotion of fear, the ‘fight or flight’ reaction and the hippocampus is involved in the process of where and whether or not a memory is needed and then stored to be used at a later time.
The PNS
The PNS is made up of two parts, the nerves and ganglia. And is divided into two systems the somatic and the autonomic. But the autonomic has two divisions; the sympathetic and the parasympathetic. Also the nerves involved with the head (cranial nerves) only communicate with the brain and the spinal nerves only with the spinal cord.
The Somatic System
This system includes the sensory nerves of the skin and the effector nerves of the muscles and tendons. These actions can be voluntary or involuntary as in reacting to a pin prick.
The Autonomic System
This system has two divisions; the sympathetic and the parasympathetic. All of the actions or reactions in this system are automatic and involuntary. Basically the sympathetic system reacts to situations, whereas the parasympathetic system has the opposite reaction or calming affect. The sympathetic system is more associated with the fight or flight actions where the parasympathetic is the rest and digest system.
Drug Abuse
Have basically two effects; they affect the limbic system and therefore altering the mood or emotions of the individual or they affect specific neurotransmitters interactions with specific receptors.
Sources:
Human Biology 10th Edition by Sylvia S. Mader
Larry M. Frolich Power Point Unit III
http://www.emc.maricopa.edu/faculty/farabee/biobk/BioBookNERV.html
http://eleceng.ukc.ac.uk/~sd5/pics/research/big/actpot.gif.
http://www.emc.maricopa.edu/faculty/farabee/biobk/BioBookNERV.html
http://www.prs.k12.nj.us/schools/PHS/Science_Dept/APBio/pic/brain.gif.
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