Chapter 13 Flashcards
Somatic reflex
Reflexes that involve somatic motor neurons and skeletal muscles
Autonomic reflexes
Reflexes whose responses are controlled in the autonomic neurons
Spinal reflexes
Integrated in the spinal cord. These reflexes may be modulated by higher input from the brain but can occur without that input.
Cranial reflex
Reflexes integrated in the brain
Innate reflexes
Born with reflexes, genetically determined, example is the knee jerk, or patellar tendon reflex.
Learned reflex
Acquired through experience. Dwight eating Altoids every time Jim pushes a button on the computer.
Monosynaptic reflex
The simplest reflex. Named for the single synapse between the two neurons in the pathway
Polysynaptic reflex
May be quite complex, with extensive branching into the CNS to form networks involving multiple inter neurons
Alpha motor neuron
The somatic motor neurons that innervate skeletal muscle fibers.
Extrafusal muscle fiber
The effectors are contractile skeletal muscle fibers. Action potentials in alpha motor neurons cause extrafusal fibers to contract .
Muscle tone
Resistance to stretch even when the muscle is relaxed and at rest.
Structure and function of the golgi tendon organ
A type of receptor found at the junction of tendons and muscle fibers, GTOs respond primarily to muscle tension created during the isometric phase of contraction. Relatively insensitive to muscle stretch
Gamma motor neuron
Small neuron that innervates intrafusal fibers within the muscle spindle
Intrafusal fiber
Modified muscle fibers of the muscle spindle that lack myofibrils in their central portions
Muscle spindle
Muscle receptors that send information about muscle length
Myotatic unit
Collection of synergistic and antagonistic muscles that act in a coordinated fashion to control a single joint
How does a stretch reflex and reciprocal inhibition coordinate joint movement
When a muscle spindle is stretched and the stretch reflex is activated, the opposing muscle group must be inhibited to prevent it from working against the resulting contraction of the homonymous muscle.
The process of muscles on one side of a joint relaxing to accommodate contraction on the other side of the joint
How can flexor and crossed extensor reflexes coordinate limb movements
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How flexion and crossed extensor reflex’s can coordinate movements
The crossed extensor reflex is contralateral, meaning the reflex occurs on the opposite side of the body from the stimulus. (Stepping on a nail and your other leg compensating all of the body weight as you lift the injured foot)
Compare reflex, voluntary and rhythmic units
Reflex is an involuntary or automatic action in response to stimulus.
Voluntary movement is purposeful, goal directed movements. Initiated entirely from within the CNS, performance improves with practice, reflex and postural movements are often initiated that compensate for the effects of the intended action on other parts of the body.
Rhythmic movements a combination of reflex and volition. Initiation and termination is voluntary but the actual movement is more stereotyped (
Walking, running, chewing)
Central pattern generator
Neuronal circuits that when activated can produce rhythmic motor patterns such as walking, breathing, flying, and swimming.
Spinal cord— reflexes and locomotion
The central pattern generator provides the basic locomotor rhythm and synergies by integrating commands from various sources that serve to initiate or modulate its output to meet the requirements of the environment
Brain stem and cerebellum — postural reflex, eye movement, hand movement
The cerebellum receives information from the sensory systems, the spinal cord, and other parts of the brain and then regulates motor movements.
Cerebral cortex and basal ganglia— voluntary movement
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Phases of voluntary movement
Planning
Initiation
Execution
Feedforward controls
Element or pathway within a control system that passes controlling signal from a source in its external environment to a load somewhere in its external environment
Feedback control
A response within a system that influences the continued activity or productivity of that system. In essence it is the control of a biological reaction by the end products of that reaction
Features of visceral muscle movement
Involuntarily controlled
Not striated
Not branched
And singly nucleated
Controlled by the autonomic and enteric nervous systems .
