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Nervous System- Kaylyn Ganiron (p.5) - Coggle Diagram
Nervous System- Kaylyn Ganiron (p.5)
MAJOR FUNCTIONS OF THE NERVOUS SYSTEM
sensory input, integration and processing (decision-making), and motor output (response)
functions: thinking, movement; internal process physiology
Sensory Function
sensory receptors detect internal or external changes
info. travels from receptors to sensory neurons, which transport info. the CNS
Integrative Function
coordination of sensory info. in the CNS (central nervous system)
processing decision-making
Motor Function
motor neurons to effectors
respond to decisions made in the CNS
MAJOR DIVISIONS & SUBDIVISIONS OF THE NERVOUS SYSTEM
Peripheral Nervous System (PNS)
consists of nerves that connect the cerebrospinal fluid to body parts
consists of cranial nerves, arising from the brain, and spinal nerves, arising from the spinal cord
sensory and motor divisions
2 Motor Parts of the PNS:
I. somatic nervous system: connect CNS to skeletal muscles and the skin, and oversees conscious activities
II. autonomic nervous system: connects the CNS to viscera, and controls subconscious activities
Autonomic Nervous System (ANS)
portion of the PNS that functions constantly and independently, without conscious effort
controls visceral motor functions of smooth muscle, cardiac muscle, and glands
helps maintain homeostasis, responds to emotional stress, and prepares the body for strenuous activity
functions: controls heart rate, blood pressure, breathing rate, and body temp
Autonomic neurons
preganglionic neuron- leaves CNS, and synapses w/ 1 or more neurons
postganglionic neuron- axon leaves an autonomic ganglion
sensory receptors- tactile vision, auditory, olfactory gustatory movement
motor impulses- travel through cranial and spinal nerves, then through ganglia, and finally to effectors (muscles or glands)
Sympathetic Divison
short ganglionic fibers
activate in conditions of stress or emergency (fight to flight)
arise from neurons in the gray matter
functions: produce localized adjustments (ex. sweating)
Parasympathetic Division
long preganglionic fibers
active under normal, restful conditions (rest to digest)
arise from the brainstem and sacral region
functions: digestion, metabolism
CLASSIFICATION OF NEURONS
multiplier neurons: have many dendrites and one axon arising from their cell bodies; most neurons w/ cell bodies in CNS are multipolar
bipolar neurons: have two processes extending from the cell body, a dendrite and an axon
unipolar neurons: have only one process extending from the cell body
functional classification of neurons:
sensory (afferent) neurons: conduct impulses (unipolar, bipolar) from peripheral receptors to the CNS
interneurons (association or internuncial neurons): multipolar neurons lying within the CNS that form links between other neurons
motor (efferent) neurons: multipolar neurons that conduct impulses from the CNS to peripheral effectors
CONNECTIVE TISSUE COVERINGS
Dura mater
I. outermost layer of meninges
II. tough, dense connective tissue, very thick
III. sheath around the spinal cord is separated from the vertebrae by an epidural space
Arachnoid mater
I. middle layer
II. subarachnoid space which contains CSF
Pia mater
I. innermost layer of meninges
Meninges: 3 membranes lie between the skull bones and vertebrae and the soft CNS tissues
a. Epineurium = outer covering of a nerve
b. Perineurium = covering around fascicles (bundles) of nerve fibers
c. Endoneurium = covering around individual nerve fibers (axons)
SPINAL NERVES
Numbered in Sequence:
II. 12 pairs of thoracic
III. 5 pairs of lumbar
I. 8 pairs of cervical
IV. 5 pairs of sacral
V. 1 pair of coccygeal
sensory dorsal root and motor ventral root
dorsal root:
contains ganglion
houses the cell bodies of the sensory neurons entering the spinal cord
ventral root:
(with dorsal root) unite to form spinal nerve
extends out of the vertebral canal
PLEXUSES
I.cervical plexuses (C1-C4): lie on either side of the neck
II. brachial plexuses (C5-T1): arise from lower cervical and upper thoracic nerves
definition: main branches of spinal nerves, except in the thoracic region, from networks
III. lumbosacral plexuses (L1-S4): arise from the lower spinal cord
anterior branches of the thoracic spinal nerves do not form plexuses, but become intercostal nerves
definition: intercostal nerves are somatic nerves
MAJOR PARTS & FUNCTIONS OF THE BRAIN
Parietal Lobe
understanding speech and choosing proper words
Occipital Lobe
helps analyze visual patterns and combine visual images with other sensory info.
Temporal Lobe
processing auditory information, recognizing language, and memorizing speech
Cerebellum
I. integrates sensory info. about the position of body parts
II. coordinates skeletal muscle activity
III. maintains posture
IV. ensures that movement occurs in the desired manner
Sensory areas:
I. cutaneous senses: anterior parietal lobe (touch)
II. visual area: posterior occipital lobe (eye)
III. auditory area: posterior temporal lobe
IV. taste area: base of central suculus and insula (mouth)
V. smell area: deep in temporal lobe (nose)
located in several areas of cerebrum, sensory input, feelings, sensations
Frontal Lobe
control a # of higher intellectual processes (ex. problem solving)
The Brain Stem
midbrain- contains main motor pathways between cerebrum and lower portions of the nervous system
pons- contains center that helps regulate the rate and depth of breathing
medulla oblongata- transmits all ascending and descending impulses between the brain and spinal cord
MAJOR PARTS & FUNCTIONS OF THE SPINAL CORD
Cervical enlargement
thickened area near top of spinal cord
provides nerves to upper limbs
Lumbar enlargement
thickened region near the bottom of the spinal cord
gives rise to nerves that serve the lower limbs
Cauda equina (horse's tail)
formed where spinal cord tapers to a point inferiorly
consists of spinal nerves in the lumbar and sacral areas
begins at base of the brain
Structure of the Spinal Cord
white matter=bundles of myelinated nerve fibers (nerve tracks), surrounds core of gray matter (housing interneurons and neuron cell bodies
upper and lower wings of gray matter from the posterior and anterior horns
central canal in the middle of the gray matter contains cerebrospinal fluid (CSF)
Function of the Spinal Cord
I. major functions- transmit impulses and house spinal relflexes
II. ascending tracts carry sensory info.
III. descending tracts- carry motor info.
IV. spinal reflexes- controlled by reflex arcs that pass through the spinal cord
ACTION POTENTIAL & THE NERVE IMPULSES
neuron remains at rest until stimulated
Reaching an action potential is all-or-none response:
I. action potential either occurs or doesn't
II. occurs when the charge reaches -55 mV (minute ventilation)
III. action potentials of a neuron are all of the same strength
when action potential is reached: cell responds by returning to resting potential (-70 mV0 by process of repolarization
repolarization definition: the membrane potential begins to move back toward its resting
as repolarization ends, a slight overshoot called hyperpolarization occurs
Process of Impulse Conduction
I. neuron membrane maintains resting potential
II. threshold stimulus is received
III. sodium channels in the trigger zone of the axon open
IV. sodium ions diffuse inward, depolarizing the axon membrane
V. potassium channels in the axon membrane open
VI. potassium ions diffuse outward, repolarizing the axon membrane
VII: the resulting action potential causes a local electric current that stimulates the adjacent portions of the axon membrane
VIII. a series of action potentials occurs along the axon
Types of Impulse Conduction:
Continuous:
occurs in unmyelinated axons
conduct impulses sequentially over the entire length of their membrane
Saltatory
occurs in myelinated axons
myelinated sheath insulates axons from ion movement across the cell membrane
impulses "jump" from one Node of Ranvier to the next, since sodium and potassium channels occur only at the nodes
CRANIAL NERVES
12 nerves arise from the underside of the brain
most are mixed nerves containing both sensory and motor nerve fibers
1st pair arise from the cerebrum, 2nd pair arise from the thalamus, and most arise from the brainstem
12 pairs are designated by # and name; the #´s in order from superior to inferior
I. Olfactory
II. Optic
III. Oculomotor
IV. Trochlear
V. Trigeminal
VI. Abducens
VIII. Vestibulocochlear
VII. Facial
IX. Glossopharyngeal
X. Vagus
XI. Accessory
XII. Hypoglossai
function: see, hear, smell
function: help control muscle movement in head and neck
NEUROTRANSMITTERS
chemical messengers in a synapse, that convey an electrical impulse from a neuron to another cell
cell body (soma) = major organelles including nucleus
dendrites = impulses toward the cell body, provide the receptive surface for communication with other neurons
axon = impulses away from the cell body
only 1 axon in each nueron
neuroglia (glial cells, "nerve glue") = support neurons
functions: fill spaces, structurally support, protect, and insulate
REFLEX ARC (MAJOR PARTS AND FUNCTIONS)
the routes nerve impulses travel are celled neural pathways, the simplest is reflex arc
provide the basis for involuntary actions called reflexes
I. sensory receptor that detects changes
II. sensory neuron- carries the information from a receptor towards the CNS
III. interneuron- in the CNS (reflex center)
IV. motor neuron- carries a command to effectors
V. effector (muscle or gland that carries out the reflex)- responds to the initial change
receptor to CNS to effector
reflex = automatic response