Lab 8 TAMU Biol 319

reflexes

examples of a motor response

Motor response

series of action potentials that produce a muslce contraction and a movement of ine or more parts of the body

learned reflexes

result from practice or repetition

inborn reflex

a rapid, involuntary, predictable motor response to a stimulus

examples of inborn reflexes

maintain posture, control visceral activities, breathing, knee-jerk

five parts of reflex arcs

receptor, sensory neuron, integration center (mono/polysynaptic), motor neuron, effector (somatic/autonomic)

receptor

senses stimulus and initiates the signal

sensory neuron

carries afferent nerve impulses to the central nervous system

integration center of reflex arc

where the signal is processed; includes monosynaptic and polysynaptic

monosynaptic reflex

a single synapse between a motor and sensory neuron serves as the integration center

polysynaptic reflex arc

the interaction center will include a few synapses and interneurons

the interation center for most reflexes

in the central nervous system

motor neuron

carries efferent signals to the effector from the integration center

the effector

muscle or gland which generates a response to the signal; includes somatic and autonomic

somatic reflex

activates skeletal muscle

autonomic reflex

controls visceral effectors such as smooth muscle, cardiac muscle, or a gland

spinal reflexes

simple, automatic behaviors that are processed in the spinal cord

stretch and tendon reflexes

help your nervous system smoothly coordinate the activity of your skeletal muscles

Astrocytes

Most abundant, versatile, and highly branched glial cells; role in making exchanges between capillaries and neurons help determine capillary permeability, guide migration of young neurons, synapse formation

microglia

small oval cells with relatively long "thorny" processes, touch nearby processes and monitor their health, sense injury, migrate toward neurons when injured

ependymal cells

like central cavities of brain and spinal cord; cilia help circulate cerebrospinal fluid that cushions the brain and spinal cord

Oligodendrocytes

line up along the thicker neuron fibers in the CNS and wrap their processes tightly around the fibers, producing insulating coverings called myelin sheaths

satellite cells

surround neuron cell bodies in PNS

schwann cells

surround and form myelin sheaths around the larger nerve fibers in the PNS; vital to regeneration of damaged peripheral nerve fibers and increase speed of transmission of nerve impulses

glial cells

make up neuroglia; most abundant cells in the nervous system

neurons

consist of dendrites, cell body (soma) and an axon

dendrites

main receptors; convey

messages toward the cell body; graded potentials

graded potentials

short distance signals

cell body (soma)

surrounds the nucleus; contains mitochondria, ribosomes, rough er

rough endoplasmic reticulum granules in the soma

stain dark darkly in histological sections and are termed nissl bodies

nuclei

clusters of somas in the CNS

ganglia

clusters of somas in the PNS

axon

transmits signals to other neurons

parts of an axon

initial segment, axon hillock, collateral branches, telodendria, synaptic terminal, synaptic vesicles, neurotransmitter molecules

how axon parts work together

first part is the initial segment which extends from the axon hillock, the axon then divides into collateral branches, then into smaller branches called telodendria, the distal tip of each telodendrion is a synaptic terminal and has synaptic vesicles that contain neurotransmitter molecules

myelin sheath

covers long/large nerve fibers; protects and electrically insulates fibers; increases the speed of transmission of nerve impulses

myelinated fibers (axons bearing a myelin sheath)

conduct nerve impulses rapidly

unmyelinated fibers

conduct nerve impulses slowly

are myelin sheaths in other parts of neurons?

no, they are only associated with axons; dendrites are always unmyelinated

multipolar neurons

neurons that have more than two dendrites; make up more than 99% of the neurons in the nervous system