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Nervous System
Communication, control and Integration
All functions are Linked.
• Communication makes control possible
• Control makes integration possible• Integration leads to homeostasis
which makes survival possible
Nervous system does not work alone.To maintain homeostasis the body must have
the ability to monitor and then respond appropriately to changes that may occur in either the internal or external environment.
• Sense organs such as the eye and simple receptors in the skin or other tissues provide input.
• The Endocrine system produces hormones that also regulate body functions and maintain homeostasis working with the nervous system.
• Nervous systems is rapid and Endocrine systems is slower.
Parts of the Nervou System
2 Divisions of Nervous System• Central Nervous System - CNS BRAIN and SPINAL CORD• Peripheral Nervous System - PNS NERVES
cranial nerves – carry impulses to and from the brain.
Spinal nerves – carry impulses to and from the spine.
Brain, Spinal cord and Nerves
CNS integrates incomingPieces of info and Initiates outgoing responses
PNS – Nerves that lie in the Periphery or outer regions(Cranial and Spinal Nerves)
PNS
• Incoming – Afferent nerves – Sensory nerves –carry toward CNS from somatic or visceral sensory fibers.
• Outgoing – Efferent nerves – Motor nerves – carry away from CNS to somatic effectors (muscles and glands)
ANS – Autonomic Nervous SystemPart of the PNS 2 partsSympathetic Parasympathetic exits the spine exits the brain Fight or Flight Rest & Repair
response response
Activity Normal resting AKA Involuntary nervous system
Nervous Tissue
Neurons (Nerve Cells) and Neuroglia (Supporting Cells)
NeurogliaAstrocytes, Microglia, Ependymal cells, Oligodendrocytes and Schwann Cells
STAR shaped, largest, most numerous and form a sheath around the brain blood capillaries (BBB) Blood-Brain Barrier Form the living barrier between capillaries and neurons to allow exchange between them. Protects neurons from harmful substances that might be in the blood. Pick up excess ions and recaptures neurotransmitters.
Astrocytes
Microglia
• Spiderlike Phagocytes -Enlarge and Engulf and Destroy microbes and cellular debris
Ependymal Cells
• Form thin sheets that line fluid filled cavities in the brain and spinal cord.
• Their cilia help circulate cerebrospinal fluid.
Oligodendrocytes• Produce the fatty myelin sheet around
nerve fibers like insulation around a wire.
Neuroglia cannot conduct impulses!
Schwann Cells
• Form the myelin sheaths around nerve fibers that are found in the PNS
Contain the fatty white substance myelin
Schwann Cells
Neurons
• Cell body• Dendrites• Axons• Synaptic knobs
3 types of Neurons
“The big dogs” of the Nervous system
Unipolar Bipolar Multipolar Neurons
One axon several dendrites
Two processes becomefused as one then separate into axon and dendrite.
One axon andone dendrite
White matter vs. Gray matter• White matter is
myelinated - faster• Gray matter is
unmyelinated - slower
Physiology of an impulse
• Resting Membrane Potential -70mV
• Depolarization• Threshold -56mV• Action Potential -30mV• Repolarization• Depolarization/repolar-
ization repeats down the neuron until it reaches the end. Either at a motor end plate or the next neuron.
Synaptic Cleft and transmission of an impulse
Neurotransmitters bridge the gap at the synaptic clefts.
Acetylcholine – the main neurotransmitterAmines – Serotonin and histamine subclass- dopamine, epinephrine,
norepinephrine Affect learning, emotions, motor control and
other activities.Amino Acids – Most important common
neurotransmitters. Ex. Glutamate -75% of signals in the brain.Neuropeptides – act as hormones and pain relievers
subclass- enkephalins and endorphinsNeuromodulators AKA cotransmitters -regulate the
effects of neurotransmitters.
Which parts Control What?
(another view)
12(pairs) Cranial Nerves
Spinal Nerves (31 Pairs)
Coverings of the Brain and Spinal Cord
Meninges or membranous coverings • Dura mater – Outer covering Tough, leathery – forms a large cavity of
blood along the top of the brain called the sagittal sinus.
• Arachnoid – thin, translucent middle layer – contains cerebrospinal fluid (CSF)
• Pia mater – Inner most covering – Thin, vascular membrane covering the brain.
Meninges of the Brain
HOMEOSTASIS
NO OTHER BODY ORGAN IS SO ABSOLUTELY DEPENDENT ON A CONSTANT INTERNAL
ENVIRONMENT AS THE BRAIN.Other tissues can withstand the small
fluctuations in the concentrations of hormones, ions, and nutrients that continually occur after eating or exercising.
If these changes occurred in the brain, uncontrolled neural activity might result.
Blood-Brain Barrier• The BBB is composed of the least permeable
capillaries in the body.• Only water, glucose and essential amino acids pass
easily through the walls of these capillaries.• Wastes, toxins, proteins, and most drugs are
prevented from entering the brain tissue.• Potassium ions are actively pumped from the brain to
the capillaries.• Fats, respiratory gases, and other fat-soluble
molecules diffuse easily through the BBB.(Thus, alcohol, nicotine, and anesthetics can affect the
brain)
Circulation of CSF
• CSF is continually moving from the 2 lateral ventricles to the 3rd ventricle in the diencephalon and then through the cerebral aqueduct of the midbrain to the 4th ventricle to the pons and medulla oblongata.
• Normal drainage should maintain a volume of about 150mL or ½ a cup
Problems with the Nevous System• Tumors may obstruct drainage of CSF or
interfere with normal function.• Meningitis – inflammation of the meninges bacterial or viral infections• Encephalitis- inflammation of the brain. • Multiple sclerosis
Lumbar (Spinal) Tap – CSF sampling
Brain Dysfunctions• Huntington’s disease is genetic– loss of
coordination of muscle movements - After 40 usually. - Benefit from drugs that block dopamine
• Parkinson’s disease – neurotransmitter deficiency – deficient dopamine
• Concussion – brain injury is slight- dizziness, seeing stars, or unconscious briefly.
• Contusion – marked tissue destruction –severe brain stem contusions result in comas that may last from hours to a lifetime.
• Intracranial hemorrhage – death• Cerebral Edema – Swelling of the brain
Degenerative Brain Diseases• Stroke AKA Cerebrovascular Accident CVAs - 3rd leading
cause of death in the US.• Transient ischemic attack –TIA- temporary 5 to 50
minutes• Alzheimer’s Disease originally called Senile dementia –
structural damage occurs in the brain, abnormal protein deposits and twisted fibers appear within the neurons and localized brain atrophy.
• Half of Nursing Home Patients are stroke victims most of the other half are Alzheimer’s patients.
• Cerebral palsy- during deliveries a temporary lack of oxygen can result in CP - A neuromuscular disability in which the voluntary muscles are poorly controlled and spastic due to brain damage.
• Spina bifida- occurs when vertebrae form incompletely
• Hydrocephalus- Failure of the cerebrum to develop - water on the brain.
Spinal Cord Injuries• IF the spinal cord is transected or
crushed Spastic Paralysis results.Quadraplegic – all four limbs
affected.Paraplegic – only the legs affected.Swelling may cause temporary
paralysis.
Identify the types of neurons below
Identify the parts of this cell.
1.
2 3
4
5 6
7 8 9
10. What are the support cells of the nervous system called?
Place these in order of the 12 cranial nerves as they exit the brain. Then ID the nerve type. (S,M, or B)
• Vestibulocochlear• Trochlear• Oculomotor• Glossopharyngeal• Accessory• Olfactory• Abducens• Vagus• Hypoglossal• Optic• Trigeminal• Facial