lab eight: introduction to the nervous system Flashcards
if a motor response is initiated, it usually involves a series of _____ that produce a muscle contraction and a movement of one or more parts of the body
action potentials
reflexes
examples of a simple type of stimulus-response reaction
learned reflexes
result from repetition (example: driving)
inborn reflex
rapid, predictable, involuntary, and unlearned, motor response to a stimulus, and is a part of all our neural pathways
an inborn reflex to a painful stimulus can be so rapid that a response is generated _____ you even perceive the pain
before
many of the inborn reflexes are regulated by what?
spinal cord and brain stem
myotatic reflex
knee-jerk that occurs when tapped on the tendon under the kneecap
five parts of reflex arcs
- the receptor that senses the stimulus and initiates the signal
- a sensory neuron that carries afferent nerve impulses to the central nervous system
- an integration center where the signal is processed
- the motor neuron that carries efferent signals to the effector form the integration
- the effector such as a muscle or a gland which generates a response to the signal
simple monosynaptic reflex
a single synapse between a motor and sensory neuron serves as the integration center
polysynaptic reflexes
the integration center will include a few synapses and interneurons
the integration center for most reflexes is where?
in the central nervous system
somatic reflex
activates skeletal muscle
autonomic reflex
controls visceral effectors such as smooth muscle, cardiac muscle, or a gland
_____. _____, or _____ reflexes indicate damage to the nervous system
distorted; exaggerated; absent
_____ and _____ reflexes help coordinate smooth movements of skeletal muscle groups
stretch; tendon
muscle spindles in skeletal muscle
convey information about muscle length or the amount of stretch
golgi tendon organs
convey information about tendon tension so that proper regulation of these reflexes takes place
tendon organs and muscles spindles are examples of what?
proprioceptors
proprioceptors
receptors that supply information to the central nervous system about the body’s position in space and how much a muscle has moved, or not moved, its insertion
_____ are sent to the antagonist muscle to signal for relaxation in the reciprocal muscle to prevent opposition to movement
inhibitory signals
reciprocal inhibition
inhibit contraction; allows for contraction of the stretched muscle without impedance from the basal muscle tone of the opposing muscle
all stretch reflexes are _____ and _____ in the contracting portion of the pathway
involve motor activity on the same side of the body; monosynaptic
ipsilateral
involve motor activity on the same side of the body
monosynaptic
involves one synapse
why is the patellar knee-jerk tested?
to determine if motor and sensory connections between the spinal cord and thigh muscles are functioning
magnitude of the response indicated what?
level of inhibition being processed at the spinal cord
exaggerated reflex
could indicate damage in the brain or spinal cord
absent reflex
could indicate damage of the peripheral nerves
stretch reflex
stimulates muscle contraction when muscle length is increased or the muscle is stretched
tendon reflex
opposite response of causing muscles to relax in circumstances of high tendon tension
“direct light” or pupillary reflex
involves four neurons that connect the retina to the mid-brain and then convey information back to the pupillary sphincter muscles
what happens when light is focused upon the eye?
pupillary sphincter muscle in the iris constricts reducing the aperture (diameter) of the pupil + consensual light reflex
consensual light reflex
pupillary sphincter muscle of the other eye constricts too when light is focused on one eye
miosis
pupillary constriction (meiosis in greek means diminution)
mydriasis
pupillary dilation
plantar reflex
elicited by running a blunt object down the lateral aspect of the sole of the foot; indirectly indicates the functionality of the corticospinal tracts and directly indicated spinal cord integrity from L4 to S2
Babinski’s sign
abnormal reflex displayed if corticospinal tract or primary motor cortex is impaired; instead of toes flexing, the great toe dorsiflexes and the other toes laterally fan
where does a delay in reaction time occur?
synapses between the different neurons involved
the nerves of the peripheral nervous system (PNS) are divided into what two groups?
cranial and spinal nerves
what are the classifications of nerves?
motor, sensory, or both
motor composition is primarily _____; however, there is some sensory activity due to _____
motor; proprioception
epineurium
outer covering that wraps a nerve
perineurium
beneath epineurium; separates the axons into bundles called fascicles
endoneurium
inside a fascicle; surrounds each axon and isolates it from neighboring axons
Schwann cells
forms myelin sheath insulation of axons in nerves of the peripheral nervous system
what are the two types of cells in the nervous system?
glial cells and neurons
glial cells
supportive role in protecting and maintaining nerve tissue; they protect support and anchor neurons into place
neurons
communication cells of the nervous system and are capable of propagating and transmitting electrical impulses
glial cells in the central nervous system
involved in the production and circulation of cerebrospinal fluid (CSF) that circulates in the ventricles in the brain and in the central canal of the spinal cord
glial cells in the central and peripheral nervous system
isolate and support neurons with myelin to increase conduction velocity
what are the four types of glial cells of the central nervous system?
astrocytes, microglia, ependymal, aligodendrocytes
what are the two types of glial cells in the peripheral nervous system?
satellite and Schwann cells
