Lecture 9: Reflexes Flashcards
____ extends from brain stem
Spinal cord
Spinal cord has 2 functions :
- serves as the neuronal link between the ___ and the _____
- is the integrating centre for the spinal ____
Brain and peripheral nervous system
Reflexes
___ pairs of spinal nerves emerge from spinal cord through spaces between adjacent vertebrae
31
Spinal nerves connect with each side of the spinal cord by a ___ and a ____
Dorsal root
Ventral root
a spinal nerve consists of both ___ and ___ fibres
Efferent
Afferent
A ___ is a bundle of peripheral neuronal axons enclosed by a connective tissue covering and following the same pathway
Nerve
White matter is organized into ___
Nerve tracts
_________: Bundles of nerve fibres with a similar function. Each tract begins or ends within a particular area of brain
Nerve tracts
____ tracts: afferent, sensory input
Ascending
____- tracts : efferent motor output
Descending
What are the 3 horns that gray matter is divided into ?
Dorsal
Ventral
Lateral
_____ horn contain cell bodies of interneurons on which afferent neurons terminate
_____ horn contains cell bodies of efferent motor neurons supplying skeletal muscles
_____ horn contains cell bodies of autonomic nerve fibres
Dorsal
Ventral
Lateral
A ____ is an involuntary stereotyped response to a sensory input
Reflex
2 types of reflexes ?
Simple /basic
Acquired / conditional
2 types of reflexes :
______ : built in , unlearned response
______ : result of practice and learning
Simple/basic
Acquired/ conditioned
___________
-> somatic motor neurons and skeletal muscles
- > spinal - integrated in spine
-> cranial - integrated in brain
__________
-> involve autonomic neurons
-> spinal- urination/defecation
-> integrated in brain - brainstem , hypothalamus , thalamus (homeostasis -gag, vomiting, sneezing, coughing, swallowing)
Somatic
Autonomic
What are the 5 reflex pathway components?
Sensory receptor
Afferent pathway
Integrating centre
Efferent pathway
Effector
- A ______ (muscle spindles in the case of somatic muscle reflexes)
2.an _______ to the CNS (sensory axon) - An _____ consisting of one or more synapses in the CNS
- An ____- to the periphery ( motor axon)
- An ___ (the muscle)
Sensory receptor
Afferent pathway
Integrating centre
Efferent pathway
Effector
A _____ has a single synapses between the afferent and efferent neurons
Monosynaptic reflex
______ have two or more synapses
Polysynaptic reflexes
What are 3 Proprioceptors :
Muscle spindle
Golgi tendon organ
Joint receptors
Skeletal muscle reflex sensory receptors ( proprioceptors)
_______- in muscles, sense stretch
________- in tendon , sense force
________- sense pressure , position
Muscle spindles
Golgi tendon organ
Joint receptors
Muscle stretch triggers a _____
Stretch reflex
_____- alpha motor neurons are stimulated to generate contraction
Isotonic contraction
Muscle contraction and receptor responses
-Length changes, but the ____ remains constant
Tension
When the whole muscle mass shortens the _____ also passively shorts
Spindles
The firing rates of the spindle afferent axons are reduced because the tension in the receptor portion of the ________ is relieved
Interafusal fibres
_______ modulate the sensitivities of the spindles
Y motor neurons
The _______ slacken when a muscle shortens (unloading spindles)
Intrafusal fibres
To ensure that info on changes in muscle length are transmitted , the CNS regulates the loading of the intrafusial fires with _______
Y motor neurons
The rapid contraction of the intrafusial fibres increases the ____ on the central sensory element of the spindle and restores the sensitivity of the spindle
During voluntary movement, a and y motor neurons are coactivated by the ____
Tension
CNS
______: The addition of a load stretches the muscle and the spindles , creating a reflex contraction
Muscle spindle reflex
_______ respond to changes in muscle tension
Golgi tendon organs
Encapsulated receptors consisting of______ from the muscle intertwined with the endings of tendon afferent axons
collagen fibres
Applying tension to collagen fibres, squeezes the axons, ____ them and triggering ___ in tendon afferents
Depolarizing
Action potentials
Afferents terminate on ________ in ventral Horn and clarke’s nucleus
Inhibitory interneurons
Primary function of Golgi tendon organs is to provide _______
Sensory information on muscle tension
_____ reflex
- monosynaptic reflex
- ex: patellar tendon reflex
- preliminary assessment of nervous system function
Stretch
Classic example of the stretch reflex ?
Patellar tendon reflex
____ reflex: stretch reflex and reciprocal inhibition
Patellar
____ reflex is an example of a polysynaptic reflex
Flexion
____ injury-> damage to any part of PNS reduces or laminates the muscle stretch reflex and reduces muscle tone
LMN
_______: Reduction/elimination of muscle stretch reflex
Hyporeflexia
LMN injury causes loss of _____ to muscle
Innervation to muscle
_____ injury-> increased tone , hyperreflexia
UMN
____- lower motor neuron, effector neuron in spinal cord
_____- upper motor neuron, neurons in higher brain levels that influence neurons in spinal cord
LMN
UMN
______ are important because they provide an objective sign medicating an abnormality and some indication to the level of the abnormality
Reflexes
The responsiveness of reflexes can be altered by ____ or ____
Trauma or disease
__________
- interruption of reflex arc by either peripheral sensory or lower motor neuron (LMN) lesions
Loss/reduction of reflex
__________
- injury to upper motor neuron (UMN) above the anterior horn cell leads to loss of descending inhibition
Increased reflex and muscle tone
