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Nervous Gissel Hernandez …
Nervous Gissel Hernandez period: 5
Major Functions of Nervous System
Sensory Input: Info gathered by sensory receptors about internal and external changes
Integration: Processing and interpretation of sensory input
Motor output: Activation of effector organs (muscles and glands) produces a response
Central nervous system (CNS): Brain and spinal cord of dorsal body cavity.
Integration and control center: Interprets sensory input and dictates motor output
Peripheral nervous system (PNS):
The portion of nervous systems outisde CNS
Consists mainly of nerves that extend from brain and spinal cord
Spinal nerves to and from spinal cord
Cranial nerves to and from brain
Sensory (afferent) division
Somatic sensory fibers: convey impulses from skin, skeletal muscles, and joints to CNS
Visceral sensory fibers: convey impulses from visceral organs to CNS
Motor (efferent) division
Transmits impulses from CNS to effector organs
Muscles and glands
Somatic nervous system (voluntary)
Somatic motor nerve fibers conduct impulses from CNS to skeletal muscle
Conscious control of skeletal muscles
Autonomic nervous system (involuntary)
Consists of visceral motor nerve fibers
Regulates smooth muscle, cardiac muscle, and glands
Sympathetic, parasympathetic
Microglial cell: Small, ovoid cells with thorny processes that touch and monitor neurons, migrate toward injured neurons
Astrocytes: Most abundant, versatile, highly branches of glial cells, cling to neurons, synaptic ending, and capillaries
Support brace neurons, help info process in brain
: : :
Neuroglia (glial cells): small cells that surround and wrap delicate neurons
Neurons (nerve cells): excitable cells that transmit electrical signals
Neurotransmitters
– NE is released by adrenergic fibers at:
▪ Almost all sympathetic postganglionic axons, except those at sweat glands (release ACh)
• Effects of neurotransmitter depends on whether it binds to cholinergic
receptor or adrenergic receptor
▪ All ANS preganglionic axons and
▪ All parasympathetic postganglionic axons
• Major neurotransmitters of ANS are acetylcholine (ACh) and norepinephrine (NE)
– Ach (same as ACh used by somatic motor neuron) is released by cholinergic fibers at:
Spinal Nerves
Dorsal roots: Contain sensory (afferent) fibers from sensory neurons in dorsal root ganglia, conducts impulses from peripheral recpetors
Ventral Roots: Contain moto (efferent) fibers from ventral horn motor neurons innervate skeletal muscles
8 pairs of cervical nerves, 12 pairs of thoracic nerves, 5 pairs of lumbar nerves, 5 pairs of sacral nerves, 1 pair of tiny coccygeal nerves
Reflex Arc
Integration center: either monosynaptic or polysynaptic region with CNS
Motor neuron: conducts efferent impulses from integration center to effector organ
Sensory neuron: transmits afferent impulses to CNS
Effector: muscle fiber or gland cell that responds to efferent impulses by contracting or secreting
Receptor: Site of stimulus action
Somatic reflexes: activate skeletal muscle
Autonomic (visceral) reflexes: activate effectors (smooth or cardiac or glands)
31 pairs of spinal nerves
Disorder/ Diseases
Autonomic dysreflexia:
Life-threatening, uncontrolled activation of autonomic neurons
in quadriplegics and people with spinal cord injuries above T
Blood pressure skyrockets, posing increased risk for stroke
Raynaud's disease:
Painful, exaggerated vasoconstriction in fingers and toes
Digits turn pale, then cyanotic
Treated with vasodilators
Hypertension (high blood pressure):
Overactive sympathetic vasoconstrictor response to stress
Heart must work harder, and artery walls are subject to
increased wear and tear
Can be treated with adrenergic receptor-blocking drugs
Autonomic nervous system
Make adjustments to ensure optimal support for body activities
Shunts blood areas that need it adjusts heart rate, blood pressure, digestive processes
Innervate smooth muscles, cardiac muscles, and glands
Consists of neurons that:
Drugs of Abuse
Methamphetamine: Removes dopamine from synaptic cleft, enters dopamine vesicles forcing dopamine out. Causes transporters to work in reverse and the excess dopamine becomes trapped in the synaptic cleft overstimulating the cell. Is high addictive and makes the user feel intense pleasure and exhilaration.
Alcohol: GABA binds to receptor, cell is less likely to free. When alcohol enters brain it delivers double sedative punch, it binds to glumate receptors preventing glumate from exciting the cell. It affects the brain nvolving memory formation, decision making and impulse control
Cocaine: Blocks transporters, leaving dopamine trapped in synaptic cell causing to overstimulate the cell. Concentrates in the reward pathway, active in the part of brain controlling voluntary movements. Cocaine abusers are fidgety and unable to sit still.
LSD: Resembles serotonin, elicits its effect by binding to serotonin receptors, it interacts with particular ones and inhibits/ excites them. Makes one feel wakefulness and evoking a startle response to unexpected stimulus.
Heroine: Inhibits dopamine from being released, the release of inhibitory neurotransmitters is shut down, without inhabitation dopamine can be released, mimics natural opiates. Makes one feel sedated and well-being.
Ecstasy: Mimics serotonin and is taken up by serotonin transporters, alters transporter becomes temporarily confused and starts doing job in reverse. Responsible for mood, sleep, perception and appetite, has addictive properties.
Marijuana: Inhibit dopamine from being released, cannabid receptors turn off release of inhibitory neurotransmitters. Without inhibition, dopamine can be released. Slows down movement making people feel relaxed and calm.
Cranial Nerves
Optic Nerves (II): Purely sensory (visual) function
Oculomotor nerves (III): Function is raising eyelid, directing eyeball, constricting iris (parasympathetic), and controlling lens shape
Trochlear nerves (IV): Directs eyeball
Trigeminal nerves (V):Sensory impulses from various areas of face
Abduecens nerves (VI): Innervating lateral rectus muscle
Facial nerves (VII): Facial expression, parasympathetic impulses to lacrimal and salivary glands
Vestibulocochlear nerves (VIII): Adjustment of sensitivity receptors, formerly auditory nerve
Glossopharyngeal nerves (IX):innervate part of tongue and pharynx for swallowing and provide
parasympathetic fibers to parotid salivary glands
Vagus nerves (X):help regulate activities of heart,
lungs, and abdominal viscera
Accessory nerves (XI):Accessory nerves exit skull via jugular foramina to innervate trapezius and
sternocleidomastoid muscles
Olfactory nerves (I): Sensory nerves of smell
Hypoglossal nerves (XII): Innervate extrinsic and intrinsic muscles of tongue that contribute to swallowing
and speech
Major part and functions of brain
Cerebral hemispheres: Superior part of brain
Surface markings: Gyri: ridges, Sulci: shallow grooves, Fissures: deep grooves
Longitudinal fissure, separates two hemispheres
Transverse cerebral fissure, separates cerebrum and cerebellum
Five lobes: frontal, parietal, temporal, occipital, insula
Diencephalon: Thalamus, hypothalamus, epithalamus
Brain Stem:
Consists of three regions: midbrain, pons, medulla oblongata
• Similar in structure to spinal cord but contains nuclei embedded in white matter
• Controls automatic behaviors necessary for survival
Cerebellum: Located between diencephalon and pons
Cerebral peduncles, cerebral aqueduct
Includes corpora quadrigemina, superioir and inferior colliculi