Recognized how reflexes may be classified. (table 13.1)
- 1. Efferent division that controls the effector
- a. Somatic motor neurons control skeletal muscles.
- b. Autonomic neurons control smooth and cardiac muscle, glands, and adipose tissue.
- 2. Integrating region within the CNS
- a. Spinal reflexes do not require input from the brain.
- b. Cranial reflexes are integrated in the brain.
- 3. Time at which the reflex develops
- a. Innate (inborn) reflexes are genetically determined.
- b. Learned (conditioned) reflexes are acquired through experience.
- 4. The number of neurons in the reflex pathway
- a. Monosynaptic reflexes have only two neurons: one afferent(sensory) and one efferent. Only synaptic motor reflexes can be monosynaptic.
- b. Polysynaptic reflexes include one or more interneurons between the afferent and efferent neuron. All autonomic reflexes are polysynaptic because they have three neurons: one afferent and two efferent.
Compare somatic monosynaptic (ms) and polysynaptic (ps) reflexes. Give an example for each reflex. trace the pathway for each.
- - there is on one synapse that occurs in a ms reflex, like the knee jerk reaction
- - stimulus-->receptor-->sensory neuron-->one synapse in the spinal cord, integration-->efferent neuron-->target cell-->response
- ps reflex in integrated in the brain, like stepping on a needle and reacting to it.
-stimulus-->receptor-->sensory neuron-->two synapses in the CNS-->efferent neuron-->target cell-->response
Compare autonomic reflexes with somatic. Note how the brain may be involved or not.
- -autonomic reflexes (visceral reflexes) occurs among internal organs, somatic deals with muscles
- -urination and defecation are spinal reflexes and can be involuntary or involuntary
Define proprioceptor. What are the three types?
- -proprioceptors determine the body's position in space
- -there are muscle spindles and golgi tendon organs found in skeletal muscles and joint receptors
Explain the function and location of muscle spindles and GTO's.
- -muscle spindles are found between extrafusal muscle fibers and sense muscle stretch
- -GTO are found at the junction of muscle and tendon respond to muscle tension during isometric contraction and intensive muscle strech
Differentiate between extrafusal and intrafusal fibers.
- extrafusal fibers are normal contractile muscle fibers
- intrafusal fibers are found within a capsule of a muscle spindle, the ends are contractile but the center lacks myofibrils, the center consists of gamma motor neurons that synapses onto alpha neurons
Compare reflex, voluntary, and rhythmic movements.
Reflex movement is initiated primarily though external via sensory receptors;minimally voluntary, i.e. knee jerk, cough, postural reflexes; it is least complex, integrated at the spinal cord or brain stem with higher center modulation
Voluntary movement is initiated through external stimuli or at will; i.e. playing the piano; most complex, integrated at the spinal cord; becomes "muscle memory" once learned
Rhythmic movment is combo of vol. and reflex movement initiated on the cerebral cortex; i.e. walking or running; intermediate complexity, integrated at spinal cord with higher center input required; once activated center pattern generators(CPGs) maintain spontaneous activity, requires input from the brain stem
What is a feedforward reflex?
Allows the body to prepare for voluntary moment, and feedback mechanism are used to create smooth; continuous motion
Describe the role of the basal nuclei in voluntary motor control and how relates to Parkinson's.
The basal ganglia aids in cognitive function, memory, as well as the coordination of movement. Parkinson's is a progressive neurological disorder, it destroys neurons that release dopamine, s/s are tremors in hands, arms, and legs, mostly at rest. hard to initiate movement, lose facial expression, fail to blink.