Chapter 8 Nervous System (pictures)

Homeostasis
metabolic equilibrium actively maintained by several complex biological mechanisms that operate via the autonomic nervous system to offset disrupting changes
Central Nervous System
Central Nervous System
the portion of the vertebrate nervous system consisting of the brain and spinal cord
Peripheral Nervous System
Peripheral Nervous System
the section of the nervous system lying outside the brain and spinal cord
Cranial Nerves
12 pairs of nerves arising from the brain
Spinal Nerves
Spinal Nerves
31 pairs of nerves arising from the spinal cord
Effector
Effector
an organ (a gland or muscle) that becomes active in response to nerve impulses
Somatic Nervous System
the division of the peripheral nervous system that controls the body’s skeletal muscles
Autonomic Nervous System
the part of the nervous system of vertebrates that controls involuntary actions of the smooth muscles and heart and glands
Visceral Nervous System
another name for ANS, controls smooth muscle, cardiac muscle, and glands
Sympathetic Nervous System
the division of the autonomic nervous system that arouses the body, mobilizing its energy in stressful situations
Parasympathetic Nervous System
the division of the autonomic nervous system that calms the body, conserving its energy
Biofeedback
using of feedback about biological conditions to bring involuntary responses, such as blood pressure and relaxation, under voluntary control
Neuron
a cell that is specialized to conduct nerve impulses
Dendrites
Dendrites
the bushy, branching extensions of a neuron that receive messages and conduct impulses toward the cell body
Axons
Axons
a part of a neuron that carries impulses away from the cell body
Myelin
Myelin
a fatty substance that helps insulate neurons and speeds the transmission of nerve impulses
Schwann cells
Schwann cells
Specialized cells that myelinate the fibers of neurons found in the PNS
Nodes
Nodes
Part of the neuron that ion flow occurs across the membrane; action potential jumps from one of these to the next; located on the myelin sheath; sole location of ion transfer
Myelin Sheath
a layer of fatty tissue segmentally encasing the fibers of many neurons; enables vastly greater transmission speed of neural impulses as the impulse hops from one node to the next
Neurilemma
Neurilemma
additional sheath external to myelin that is formed by Schwann cells and found only on axons in the peripheral nervous system
White fibers
White fibers
myelinated axons
Gray matter
Gray matter
Brain and spinal cord tissue that appears gray with the naked eye; consists mainly of neuronal cell bodies (nuclei) and lacks myelinated axons.
White Matter
White Matter
whitish nervous tissue of the CNS consisting of neurons and their myelin sheaths
Sensory Neurons
Sensory Neurons
neurons that carry incoming information from the sense receptors to the central nervous system
afferent neurons
afferent neurons
Neurons that transmit messages from sense organs to the central nervous system.
Motor Neurons
Motor Neurons
neurons that carry outgoing information from the central nervous system to the muscles and glands
Efferent Neurons
motor neurons
Interneurons
Interneurons
Central nervous system neurons that internally communicate and intervene between the sensory inputs and motor outputs
Nerve
Nerve
any bundle of nerve fibers running to various organs and tissues of the body – PNS
Tract
a bundle of mylenated nerve fibers following a path through the brain- CNS
MIXED NERVES
nerves composed of both sensory and motor fibers
NEUROGLIA
NEUROGLIA
known as glial cells: connective tissue that supports,nourishes, protects, insulates and organizes neURons
Glial
Glial
Type of cell located in the nervous system that surrounds a portion of the neuron to provide support.
Astrocytes
Astrocytes
largest, most numerous glial cells; maintain blood-brain barrier to isolate CNS from general circulation; provide structural support for CNS; regulate ion and nutrient concentrations; perform repairs to stabilize tissue and prevent further injury
Potential
the difference in electrical charge between two points in a circuit expressed in volts
Polarized
Electrical condition of the plasma membrane of a resting neuron
Nerve impulses
a wave of depolarization and repolarization that self-propagates along the plasma membrane of a neuron; AKA nerve action potential
Action Potential
a neural impulse; a brief electrical charge that travels down an axon. the action potential is generated by the movement of positively charged atoms in and out of channels in the axon’s membrane
Resting state
the period during which the inside of a neuron has a slightly higher concentration of negatively charged ions than the outside does. a neuron during this time is inactive
Depolarization
sodium rushes into neuron through membrane, potassium ruses out; results in a change in charge
Repolarization
after Na+ ions have rushed into the cell, K+ ions rush out of the cell to restore the balance and the original polarity
Sodium Potassium Pump
a carrier protein that uses ATP to actively transport sodium ions out of a cell and potassium ions into the cell
saltatory
Action potential regenerated at each step, jumps from node to node
Synapse
the junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron. The tiny gap at this junction is called the synaptic gap or cleft.
presynaptic cell
the transmitting cell at a synapse – AXON
postsynaptic cell
the receiving cell – DENTRITE
synaptic cleft
synaptic cleft
synaptic gap or synaptic space; tiny gap between the terminal of one neuron and the dendrites of another neuron (almost never touch); location of the transfer of an impulse from one neuron to the next
Neurotransmitter
chemical used by a neuron to transmit an impulse across a synapse to another cell
end bulbs
Look like tiny bubbles, are located at the extreme ends of the axon’s branches. Each one is like a miniature container that stores chemicals called neurotransmitters, which are used to communicate with neighboring cells.
Receptors
Receptors
parts of the cell membrane that receive the neurotransmitter and initiate a new electric signal
Adrenaline
Neurotransmitter or Chemical that prepares the body for emergency activity by increasing blood pressure, breathing rate, and energy level
Norepinephrine
neurotransmitter that is involved in arousal and the fight-or-flight system (also mood, sleep, and learning)
Acetylcholine
Acetylcholine
a neurotransmitter that enables learning and memory and also triggers muscle contraction
Spinal Cord
a major part of the central nervous system which conducts sensory and motor nerve impulses to and from the brain
Dorsal horns
spinal nerve cells, sensory, afferent, ascending, message enters posteriorly, the two dorsal arms of the spinal gray matter
Ventral horns
The anterior columns of the gray matter of the spinal cord.
Gray commissure
across center of gray matter; contains central canal; an open space continuous with the ventricles of the brain (arises from 4th ventricle)
Central Canal
Central Canal
The narrow cavity in the center of the spinal cord that is continuous with the fluid-filled ventricles of the brain.
Posterior Median Sulcus
shallow longitudinal groove on the dorsal surface of the spinal cord
Anterior Median Fissure
wide, deep crease along the ventral surface of the spinal cord
Ascending Tracts
carry nerve impulses toward the brain
Descending Tracts
carry nerve impulses away from the brain
Reflex Arc
Reflex Arc
sensory receptor, sensory neuron, motor neuron, and effector that are involved in a quick response to a stimulus
Simple Reflex
aka Natural Reflex or Unconditioned Reflex
Spinal Reflex
A simple automatic action of the spinal cord not requiring involvement of the brain, such as the knee-jerk reflex
Stretch Reflex
knee jerk(patella reflex) Stretch receptors in muscles(muscle spindles) are stimulated when muscle is stretched. Input goes via sensory then connects with motor that contracts same muscle that is stretched
Spinal Nerves
Spinal Nerves
31 pairs of nerves arising from the spinal cord
Dorsal Root
Dorsal Root
contains the axons of the sensory neurons in the dorsal root ganglion; each segment of the spinal cord is associated with a pair of these
Ventral Root
Ventral Root
Motor Neurons
Dorsal Root Ganglion
Dorsal Root Ganglion
A group of sensory neuron cell bodies found just posterior to the spinal cord on either side. A pair of root ganglia exists for each spinal nerve that expands from the spinal cord. The ganglia are part of the peripheral nervous system (PNS).
Ganglion
Ganglion
A mass of nerve cells
Plexuses
Formed from groups of nerves that join together to do a common function after they have left the spinal cord
Cervical Plexus
a nerve plexus lying beneath the sternocleidomastoid muscle
Brachial Plexus
consists of ventral rami C5-T1; innervates the pectoral girdle and upper limbs; nerves in this plexus originate from cords or trunks
Lumbosacral Plexus
Innervates the legs. The sciatic nerve and the femoral nerve; et al.
Dermatomes
areas of the skin that send sensory information to a specific spinal nerve
Autonomic Nervous System
The part of the peripheral nervous system that controls the glands and the muscles of the internal organs (such as the heart). Its sympathetic division arouses; its parasympathetic division calms.
Sympathetic Nervous System
the division of the autonomic nervous system that arouses the body, mobilizing its energy in stressful situations
Parasympathetic Nervous System
the division of the autonomic nervous system that calms the body, conserving its energy
Sympathetic Chain
A chain of ganglia that runs along each side of the spinal column; part of the sympathetic nervous system.
Collateral Ganglia
set of ganglia the contribute to a network called the abdominal aortic plexus- 3 types: celiac, superior mesenteric, and inferior mesenteric ganglion (located at points where arteries of the same names branch off the aorta
Celiac Ganglion
Which sends fibers mainly to the digestive organs
Superior Mesenteric Ganglion
supplies nerves in the small and large intestine
Inferior Mesenteric Ganglion
supplies nerves in the large intestine, urinary system, and reproductive system
Adrenergic
Pertaining to nerve fibers in the SNS that react to epinephrine, norepinephrine, or dopamine neurotransmitters.
Craniosacral
parasympathetic division
Terminal Ganglia
contain cell bodies of parasympathetic and postsympathetic neurons; ganglia located at the end of an autonomic motor pathway close to or actually within the wall of a visceral organ.
Cholinergic
releasing or activated by acetylcholine or a related compound
Types of Neurons
Types of neurons based on function:
motor neurons – these carry a message to a muscle, gland, or other effector. They are said to be efferent, i.e. they carry the message away from the central nervous system.

sensory neurons – these carry a message in to the CNS. They are afferent, i.e. going toward the brain or spinal cord.

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interneuron (a.k.a. association neuron, connecting neuron) – these neurons connect one neuron with another. For example in many reflexes interneurons connect the sensory neurons with the motor neurons.

Functions of Glial Cells
Functions of Glial cells:
They provide mechanical support to neurons.
Because of their non-conducting nature, the glial cells act as insulators between the neurons and prevent neuronal impulses from spreading in unwanted directions.
They can remove the foreign material and cell debris by phagocytosis.
They can repair the damaged areas of nervous tissue by proliferation (gliosis) they form glial scar tissue, and fill the gaps left by degenerated neurons.
Glial cells can take up and store neurotransmitters released by the neighboring synapses. These can-either be metabolized or released again from the glial cells.
They help in neuronal functions by maintaining a suitable metabolic and ionic environment for the neurons.
Oligodendrocytes myelinate tracts.
Ependymal cells are concerned with exchanges of materials between brain and Cerebrospinal Fluid.
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