ANAPHY - CHAPTER 8 NERVOUS SYSTEM

BRAIN AND SPINAL CORD

major organs for processing sensory input and initiating responses

BRAIN

is the center of mental activity, including consciousness, memory, and thinking

CENTRAL NERVOUS SYSTEM (CNS)

division of the nervous system that consists of the brain and spinal cord

PERIPHERAL NERVOUS SYSTEM (PNS)

division of the nervous system that consists of all the nervous tissue outside the CNS, including nerves and ganglia

SENSORY DIVISION

afferent (toward) division; conducts action potential from sensory receptors to the CNS

SENSORY NEURONS

the neurons that transmit action potential from the periphery to the CNS

MOTOR DIVISION

efferent (away) division; conducts action potential from the CNS to effector organs, such as muscles and glands

MOTOR NEURONS

the neurons that transmit action potentials from the CNS toward the periphery

MUSCLE TISSUE

includes skeletal muscle (voluntarily controlled), and cardiac and smooth muscle (involuntarily controlled)

SOMATIC NERVOUS SYSTEM

transmits action potential from the CNS to skeletal muscles

AUTONOMIC NERVOUS SYSTEM (ANS)

transmits action potentials from the CNS to cardiac muscle, smooth muscle, and glands; is divided into sympathetic and parasymphathetic divisions

SYMPATHETIC NERVOUS SYSTEM

division of the autonomic nervous system that prepares the individual for physical activity; fight-or-flight; releases adrenaline and noradrenaline

PARASYMPATHETIC NERVOUS SYSTEM

division of the autonomic nervous system rest and digest; calms body to conserve and maintain energy; activates involuntary functions, such as digestion

ENTERIC NERVOUS SYSTEM (ENS)

is a unique part of the peripheral nervous system; has both sensory and motor neurons contained wholly within the digestive tract

ENTERIC NERVOUS SYSTEM (ENS)

can function without input from the CNS or other parts of the PNS, although it is normally integrated with the CNS by sensory neurons and ANS motor neurons

NEURONS

nerve cells; receive stimuli, conduct action potential, and transmit signals to other neurons or effector organs

CELL BODY

contains a single nucleus; Nissl bodies - protein synthesis

DENDRITES

are short, often highly branching cytoplasmic extensions that are tapered from their bases at the neuron cell body to their tips; usually receive information from other neurons or from sensory receptors and transmit the information toward the neuron cell body

DENDRITIC SPINES

smaller dendrites

AXON

a single long cell process extending from the neuron cell body

AXON HILLOCK

the area where the axon leaves the neuron cell body

SENSORY NEURON

(types of neuron according to function) carrying information to the CNS from a specific receptor in the body; toward

MOTOR NEURON

(types of neuron according to function) sending information to an effector of the body from the CNS

INTERNEURONS

(types of neuron according to function) one neuron to another

MULTIPOLAR NEURONS

(types of neuron according to structure) have many dendrites and a single axon; most of the neurons within the CNS and nearly all motor neurons

BIPOLAR NEURONS

have two processes: one dendrite and one axon; located in some sensory organs, such as in the retina of the eye and in the nasal cavity

PSEUDO-UNIPOLAR NEURONS

have a single process extending from the cell body, which divides into two processes a short distance from the cell body (one extends periphery, the other extends to the CNS); most sensory neurons

GLIAL CELLS

neuroglia (nerve glue); are the supportive cells of the CNS and PNS; these cells do not conduct action potentials

ASTROCYTES

serve as the major supporting cells in the CNS; can stimulate or inhibit the signaling activity of nearby neurons; regulate extracellular brain fluid; release chemical that promote the formation of tight junction

BLOOD-BRAIN BARRIER

what can pass from the blood into the nervous tissue of the brain and spinal cord

EPENDYMAL CELLS

line a fluid-filled cavities (ventricles and canals) within the CNS; some produce cerebrospinal fluid, and others, with cilia, help move the cerebrospinal fluid through the CNS

MICROGLIA

act as immune cells of the CNS; help protect the brain by removing bacteria and cell debris

OLIGODENDROCYTES

provide an insulating material that surrounds axons

SCHWANN CELLS

provide insulating material around axons

SATELLITE CELLS

found around the cell bodies of certain neurons of the PNS; provide support and nutrition to the neurons and protect the neurons from heavy-metal poisons, such as lead and mercury

MYELIN SHEATHS

are specialized layers that wrap around the axons of some neurons; are formed by the cell processes of oligodendrocytes in the CNS and Schwann cells in the PNS

MYELINATED AXONS

axons with these myelin sheaths; protects and electrically insulates axons from one another; faster

MYELIN

is an excellent insulator that prevents almost all ion movement across the cell membrane

NODES OF RANVIER

gaps in the myelin sheath; occur about every millimeter between the myelinated areas; where ion movement can occur

UNMYELINATED AXONS

lack the myelin sheaths; these axons rest in indentations of the oligodendrocytes in the CNS and the Schwann cells in the PNS; slower

DEMYELINATION

damage in myelin sheath

GRAY MATTER

consists of groups of neuron cell bodies and their dendrites, where there is very little myelin

CORTEX

In the CNS, gray matter on the surface of the brain

NUCLEI

clusters of gray matter located deeper within the brain

GANGLION

In the PNS, a cluster of neuron cell bodies

WHITE MATTER

consists of bundles of parallel axons with their myelin sheaths, which are whitish in color

NERVE TRACTS

white matter of the CNS which propagate action potentials from one area of the CNS to another

NERVES

white matter of the PNS consists of bundles of axons and associated connective tissue

LEAK CHANNELS

are always open; ions can "leak" across the membrane, down their concentration gradient

GATED CHANNELS

are closed until opened by specific signals

CHEMICALLY GATED CHANNELS

are opened by neurotransmitters or other chemicals

VOLTAGE-GATED CHANNELS

are opened by a change in the electrical property of the cell membrane

POLARIZED

uneven charge distribution across the cell membrane

POTENTIAL

small voltage difference that can be measured across the cell membrane

RESTING MEMBRANE POTENTIAL

in an unstimulated (or resting) cell; is generated primarily by the uneven distribution of K+, Na+, and negatively charged proteins across the cell membrane.

ACTION POTENTIALS

electrical signals that are conducted along the cell membrane; graded potential summate to a level called threshold

DEPOLARIZATION

loss of polarization; loss of the difference in charge between the inside and outside of the plasma membrane of a muscle or nerve cell due to a change in permeability and migration of sodium ions to the interior

REPOLARIZATION

the reestablishment of polarity, especially the return of a cell's membrane potential to resting potential after depolarization

GRADED POTENTIAL

is a relatively small change in the membrane potential; dendrites send signal → changes membrane potential

DEPOLARIZATION

more positive; movement of ions to inside; movement membrane potential closer to zero

HYPERPOLARIZATION

more negative; movement of ions to outside; away from zero

CONTINUOUS CONDUCTION

occur in unmyelinated axons; in this process, an action potential in one part of a cell membrane stimulates local currents in adjacent parts of the cell membrane (local currents in the adjacent membrane produce an action potential)

SALTATORY CONDUCTION

occur in myelinated axons; in this process, an action potential at one node of Ranvier cause a local current to flow through surrounding extracellular fluid and through the cytoplasm of the axon to the next node, stimulating an action potential at that node of Ranvier

SYNAPSE

is a junction where the axon of one neuron interacts with another neuron or with cells of an effector organ, such as a muscle or gland

PRESYNAPTIC TERMINAL

(components of synapse) end of the axon

POSTSYNAPTIC MEMBRANE

(components of synapse) membrane of the dendrite or effector cell

SYNAPTIC CLEFT

space separating the presynaptic and postsynaptic membranes

SYNAPTIC VESICLES

present in the presynaptic terminal; stores chemical substances called neurotransmitters

NEUROTRANSMITTERS

chemical substances that act as these chemical signals

CONVERGING PATHWAY

two or more neurons synapses with the same postsynaptic neuron; this allows information transmitted in more than one neuronal pathway to converge into a single pathway

DIVERGING PATHWAY

the axon from one neuron divides and synapses with more than one other postsynaptic neuron; this allows information transmitted in one neuronal pathway to diverge into two or more pathways

SUMMATION

process where many presynaptic action potentials are needed

SPATIAL SUMMATION

occurs when the local potentials originate from different locations on the postsynaptic neuron - for example, from converging pathways

TEMPORAL SUMMATION

occurs when local potentials overlap in time; this can occur from a single input that fires rapidly, which allows the resulting local potentials to overlap briefly

CENTRAL NERVOUS SYSTEM (CNS)

consists of the brain (housed within the skull) and spinal cord (is in the vertebral column)

PERIPHERAL NERVOUS SYSTEM (PNS)

consists of all the nerves and ganglia outside the brain and spinal cord

• collects information from numerous sources both inside and on the surface of the body and relays it by way of sensory neurons to the CNS, where one of three results is possible:

the information is ignored triggers a reflex is evaluated more extensively

SPINAL CORD

extend from the foramen magnum at the base of the skull to the second lumbar vertebra

CAUDA EQUINA

the inferior end of the spinal cord and the spinal nerves exiting there resemble a horse's tail

ASCENDING TRACTS

each column of the spinal cord contains this that is consists of axons that conduct action potentials toward the brain

DESCENING TRACTS

each column of the spinal cord contains this that is consists of axons that conduct action potentials away from the brain

CENTRAL CANAL

is a fluid-filled space in the center of the spinal cord

DORSAL ROOT GANGLION

region in the dorsal root; it contains the cell bodies of pseudo-unipolar sensory neurons; the axons of these neurons originate in the periphery of the body

VENTRAL HORN

Somatic motor neurons

LATERAL HORN

Autonomic motor neurons

DORSAL HORN

axons either synapse with interneurons or pass into the white matter and ascend or descend in the spinal cord

DORSAL ROOT

Sensory axons

VENTRAL ROOT

motor axons

REFLEXES

is an involuntary reaction in response to a stimulus applied to the periphery and transmitted to the CNS; allow a person to react to stimuli more quickly than possible if conscious thought is involved

REFLEX ARC

the neuronal pathway by which a reflex occurs; is the basic functional unit of the nervous system because it is the smallest, simplest pathway capable of receiving a stimulus and yielding a response

SENSORY RECEPTOR

picks up stimulus

SENSORY (afferent) NEURON

sends stimulus to interneurons in spinal cord

INTERNEURONS (associated neuron)

located between and communicating with two other neurons; process stimulus

MOTOR (efferent) NEURON

sends response to effector

EFFECTOR ORGAN

component of reflex arc muscle, gland or organ

KNEE-JERK REFLEX

also called the patellar reflex; classic example of the stretch reflex; involving the spinal cord used to determine if the higher CNS centers that normally influence this reflex are functional

STRETCH REFLEX

simplest reflex; occurs when muscle contract in response to a stretching force applied to them; important in maintaining posture and in coordinating muscular activity

WITHDRAWAL REFLEX

also called flex or reflex; to remove a limb or another body part from a painful stimulus; the sensory receptors are pain receptors, and stimulation of these receptors initiates reflex

SPINAL NERVES

arise along the spinal cord from the union of the dorsal roots and ventral roots

MIXED NERVES

all the spinal nerves contain axons of both sensory and somatic motor neurons

DERMATOME

is the area of skin supplied with sensory innervation by a pair of spinal nerves