nervous system
TRANSCRIPT
THE NERVOUS SYTEM
NERVOUS SYSTEM• Tasting, smelling, seeing,
hearing, thinking, dreaming, breathing, heart beating, moving, running, sleeping, laughing, singing, remembering, feeling pain or pleasure, painting, writing...you couldn't do any of these things without your nervous system!
• The neuron is the functional unit of the nervous system1
http://www.fulton.edzone.net/winkler/chapter08/chapter08.html
1 Higashida. “Ciencias de la Salud” Mc. Graw Hill, 2001
THE NEURONThree basic functions are performed by nervous systems:
1. Receive sensory input from internal and external environments. Sensory input can be in many forms, including pressure, taste, sound, light, blood pH, or hormone levels, that are converted to a signal and sent to the brain or spinal cord.
2. Integrate the input. In the sensory centers of the brain or in the spinal cord, the barrage of input is integrated and a response is generated.
3. Respond to stimuli. The response, a motor output, is a signal transmitted to organs than can convert the signal into some form of action, such as movement, changes in heart rate, release of hormones, etc.
http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookNERV.html
Estructure of a NeuronCell BodyCell BodyDendritesDendrites
Axon from other neurons
Axon from other neurons AxonAxon
MyelinMyelin
Dendrites from other neurons
Dendrites from other neurons
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SynapticTerminalsSynaptic
Terminals
NEURON• Humans have about 100 billion neurons
in their brain alone! While variable in size and shape, all neurons have three parts.
• Dendrites receive information from another cell and transmit the message to the cell body.
• The cell body contains the nucleus, mitochondria and other organelles typical of eukaryotic cells.
• The axon conducts messages away from the cell body. 2
• Some axons are wrapped in a myelin sheath formed from the plasma membranes of specialized glial cells known as Schwann cells which serve as supportive, nutritive, and service facilities for neurons.3
2 Audersirk T., Audersirk T., Byers B. “Biología, Ciencia y naturaleza” Pearson, Prentice Hall, 2004
3 Pruitt, Crumpler, Prothrow-Stith, “Salud: destrezas para el bienestar”, Prentice Hall, 2000
http://www.morphonix.com/software/education/science/brain/game/specimens/neuron_parts.html
NEURON
The junction between a nerve cell and another cell is called a synapse. Messages travel within the neuron as an electrical action potential. The space between two cells is known as the synaptic cleft. To cross the synaptic cleft requires the actions of neurotransmitters which are stored in small synaptic vessicles clustered at the tip of the axon.
http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookNERV.html
TYPES OF NEURONS• Three types of neurons occur. • Sensory neurons typically
have a long dendrite and short axon, and carry messages from sensory receptors to the central nervous system.
• Motor neurons have a long axon and short dendrites and transmit messages from the central nervous system to the muscles (or to glands).
• Interneurons are found only in the central nervous system where they connect neuron to neuron.
3 Pruitt, Crumpler, Prothrow-Stith, “Salud: destrezas para el bienestar”, Prentice Hall, 2000
NERVOUS IMPULSEThe plasma membrane of neurons, has an unequal distribution of ions and electrical charges between the two sides of the membrane. The outside of the membrane has a positive charge, inside has a negative charge. This charge difference is a resting potential and is measured in millivolts. Passage of ions across the cell membrane passes the electrical charge along the cell. The voltage potential is -65mV (millivolts) of a cell at rest. Sodium ions are more concentrated outside the membrane, while potassium ions are more concentrated inside the membrane. This imbalance is maintained by the active transport of ions to reset the membrane known as the sodium potassium pump.
http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookNERV.html
OrgOrg --
OrgOrg --
OrgOrg --
Org
Org -- O
rgO
rg--
Org
Org--
OrgOrg--
Org
Org
--OrgOrg
--
ION GADIENT
KK++
KK++
KK++KK++
KK++
KK++
KK++
NaNa++
NaNa++
NaNa++
NaNa++
NaNa++NaNa++
ClCl--
ClCl--
ClCl--
ClCl--
ClCl--
ClCl--
The sodium potassium pump keeps some ions in:
•K+•Org-
Other ions are kept outside:
•Na+•Cl-
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NERVOUS IMPULSE• An action potential is a
temporary reversal of the electrical potential along the membrane for a few milliseconds.
• Sodium gates and potassium gates open in the membrane to allow their respective ions to cross.
• Sodium and potassium ions reverse positions by passing through membrane protein channel gates that can be opened or closed to control ion passage.
http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookNERV.html
NERVOUS IMPULSESteps in an Action PotentialAt rest the outside of the
membrane is more positive than the inside.
1. Sodium moves inside the cell causing an action potential, the influx of positive sodium ions makes the inside of the membrane more positive than the outside. (DEPOLARIZED)
2. Potassium ions flow out of the cell, restoring the resting potential net charges. (REPOLARIZED)
3. Sodium ions are pumped out of the cell and potassium ions are pumped into the cell, restoring the original distribution of ions.
http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookNERV.html
RESTING POTENTIAL((Extracellular fluidExtracellular fluid))
(Negatively charge(Negatively chargedd neuron cytoplasm) neuron cytoplasm)
((Neuronal MembraneNeuronal Membrane) )
((Neuronal MembraneNeuronal Membrane) )
OrgOrg--
NaNa++
OrgOrg--
OrgOrg--
OrgOrg--
OrgOrg--
KK++
KK++ KK++
KK++
KK++ClCl--
ClCl--
ClCl--ClCl--
NaNa++
NaNa++
NaNa++
Potassium Chanel
Potassium Chanel
Sodium chanel(closed)
Sodium chanel(closed)
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OrgOrg--
NaNa++
OrgOrg--OrgOrg--
KK++KK++
ClCl--
NaNa++
KK++
KK++KK++ KK++
NaNa++
NaNa++
ClCl--
BEGINING OF ACTION POTENTIAL
OrgOrg--
KK++
KK++
KK++
ClCl--
NaNa++
NaNa++KK++
NaNa++
NaNa++
NaNa++
((Extracellular fluid)Extracellular fluid)
((Positive chargePositive charge)) ((Negative chargeNegative charge))((Negative chargeNegative charge))
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BEGINING OF ACTION POTENTIAL
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PROPAGATION OF ACTION POTENTIAL
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OTHER NERVOUS CELLS
There are other type of nervous cells call GLIAL CELLS, which are classified as :
a) Astrocyte.- They functions as support cells for neurons and correlate blood vessels with neurons
b) Oligodendrocytes.- They are smaller and also have supportive function
c) Microglial Cells.- They give immune protection to the nervous system, attacking microorganisms and dead tissue.
http://www.tarleton.edu/~anatomy/nervepix3.html
1 Higashida. “Ciencias de la Salud” Mc. Graw Hill, 2001
CENTRAL NERVOUS SYSTEM (CNS)• Receives and process
information;• Initiates response actions
CENTRAL NERVOUS SYSTEM (CNS)• Receives and process
information;• Initiates response actions
BRAIN• Receives and process
sensory information;• Initiates response;• Memorizes;• Generates touts and
emotions
BRAIN• Receives and process
sensory information;• Initiates response;• Memorizes;• Generates touts and
emotions
SPINAL CORD• Conducts signals from
and to the brain• Controls reflex activities
SPINAL CORD• Conducts signals from
and to the brain• Controls reflex activities
PERIPHERAL NERVOUS SYSTEM (PNS)• Transmits signals from the CNS to the rest
of the body. It is composed by nerves.
PERIPHERAL NERVOUS SYSTEM (PNS)• Transmits signals from the CNS to the rest
of the body. It is composed by nerves.
SENSORY NEURONS• Take signals from
organs to the CNS
SENSORY NEURONS• Take signals from
organs to the CNS
MOTOR NEURONS• Take signals from CNS• Control muscular and endocrine
activities
MOTOR NEURONS• Take signals from CNS• Control muscular and endocrine
activities
SOMATIC NERVOUS SYSTEM (SNS)• Control voluntary movement• Activate skeleton muscle
SOMATIC NERVOUS SYSTEM (SNS)• Control voluntary movement• Activate skeleton muscle
AUTONOMIC NERVOUS SYSTEM• Control internal organs, smooth
muscle and glands
AUTONOMIC NERVOUS SYSTEM• Control internal organs, smooth
muscle and glands
SYMPATHETIC NERVOUS SYSTEM• Prepares the body to stressfull
situations• is involved in the fight or run
response
SYMPATHETIC NERVOUS SYSTEM• Prepares the body to stressfull
situations• is involved in the fight or run
response
PARASYMPATHETIC NERVOUS SYSTEM• is involved in relaxation • Participates in basal activities
PARASYMPATHETIC NERVOUS SYSTEM• is involved in relaxation • Participates in basal activities
ORGANIZATION AND FUNCTIONS
NERVOUS SYSTEMNERVOUS SYSTEM
CENTRAL NERVOUS SYSTEM
Formed by• The brain: is
composed of three parts:
• the cerebrum (seat of consciousness),
• the cerebellum, and • the brain steam
(these latter two are "part of the unconscious brain")
• The Spinal Cordhttp://health.allrefer.com/pictures-images/central-nervous-system.html
http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookNERV.html
The Brain
• The human brain has been called the last great frontier of biology– Cerebrum– Diencephalon– Cerebellum – Brain stem
• Contains 4 ventricles– Two lateral, third,
and fourth
Cerebrum
• The cerebrum is the largest portion of the brain in humans
• Final area to receive sensory input and carry out integration
• Responsible for learning, memory, language and speech
Cerebrum• The cerebral cortex
is a thin but highly convoluted outer layer of gray matter that covers the cerebral hemispheres
• Sensation, voluntary movement, and all thought processes that we associate with consciousness
The Diencephalons• Contains the
hypothalamus and the thalamus
• Thalamus is receiving end for all sensory output except smell– Info integrated and
sent to the cerebrum• Pineal gland
– Secretes melatonin– Sleep, puberty
onset?
The Cerebellum• Primarily white matter
overlain by thin layer of gray matter
• Receives sensory input from the eyes, ears, joints, and muscles about the present position of body parts, and motor inputs from the cerebral cortex
• Integrates and sends out messages
• Ensures coordinated movement
The Brain Stem• The brain stem contains the
midbrain, the pons, and the medulla oblongata
• The midbrain acts as a relay station from cerebrum to spinal cord
• Contains reflex centers for visual, auditory, and tactile responses– Works with the medulla to
regulate breathing rate and has reflex centers for head to smell or sight
– Also vomiting, coughing, sneezing, hiccupping, and swallowing
Spinal Cord
• The spinal cord extends from the base of the brain through a large opening in the skull called the foramen magnum and into the vertebral canal formed by openings in the vertebrae
Functions of Spinal Cord
• Communication between brain and PNS
• Is organized in levels that correspond to body levels
• Sometimes the spinal cord is a relay site and a message from a sensory neuron stimulates a motor neuron via an interneuron
• Reflex actions• Sensory, motor and
interneurons are located here
PERIPHERAL NERVOUS SYSTEM• The PNS consists of • sensory neurons running
from stimulus receptors that inform the CNS of the stimuli
• motor neurons running from the CNS to the muscles and glands - called effectors - that take action.
• The peripheral nervous system is subdivided into – The sensory-somatic
nervous system and – the autonomic nervous
system http://www.sirinet.net/~jgjohnso/periperalns.html
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/P/PNS.html
PERIPHERAL NERVOUS SYSTEM• The somatic nervous system is connected to
skeletal muscle, voluntary movement and skin sensation. The sensory-somatic system consists of – 12 pairs of cranial nerves and – 31 pairs of spinal nerves
• The autonomic nervous system (ANS) which regulates individual organ function and homeostasis, and for the most part is not subject to voluntary control. It is also known as the visceral or automatic system. The autonomic nervous system has two subdivisions, the
• sympathetic nervous system and the • parasympathetic nervous system.
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/P/PNS.html#sensory-somatic
The Sympathetic Nervous System
• the sympathetic system enables the body to be prepared for fear, flight or fight. Sympathetic responses include an increase in heart rate, blood pressure and cardiac output, a diversion of blood flow from the skin and splanchnic vessels to those supplying skeletal muscle, increased pupil size, bronchiolar dilation, contraction of sphincters and metabolic changes such as the mobilization of fat and glycogen. http://www.nda.ox.ac.uk/wfsa/html/u05/u05_011.htm
http://faculty.washington.edu/chudler/auto.html
The Parasympathetic Nervous System
• In physiological terms, the parasympathetic system is concerned with conservation and restoration of energy, as it causes a reduction in heart rate and blood pressure, and facilitates digestion and absorption of nutrients, and consequently the excretion of waste products.
http://www.nda.ox.ac.uk/wfsa/html/u05/u05_011.htmhttp://faculty.washington.edu/chudler/auto.html
http://www.nda.ox.ac.uk/wfsa/html/u05/u05_011.htm
The Central Nervous System Disorders
• Meningitis– Is an infection of the
meninges– Can be caused by
virus, bacteria, or fungi
– Symptoms of stiffness, drowsiness, head ache and light sensitivity
– Can be deadly– Outbreaks more
common
Brain Injury• Can be caused by
– Physical force– Anoxia (no O2)
• Stroke (blockage)• Disease • Tumor
• Concussion – Caused by brain
bouncing off the skull• Contusion
– More serious– Bruising to the brain
Brain Injury
• Damage by– Crushing– Tearing– Bleeding– Swelling– Bruising
• The brain is complex and each injury if unique but these are reasons to wear a helmet when head injury is possible
Spinal Cord Damage
• If a disc slips and pinches the spinal cord you have a “slipped disk” and it hurts