Reflexes Review Sheet
List the four types of general sensory receptors based on function, and identify the type of stimulus that excites each type.
Nociceptors Thermoreceptors mechanoreceptors chemical receptors
Describe the role of the corticobulbar tracts.
Provide conscious control over skeletal muscles that move eye, jaw, face, and some muscles of neck and pharynx
adaptation
Reduction in sensitivity in the presence of a constant stimulus - needs stronger stimulus to be activated
developmental
innate reflexes (expected reflex shows up at specific point in development) and acquired reflexes (learned)
complexity of circuit
polysynaptic reflexes (1 interneuron) and monosynaptic reflexes
proprioceptors
position of joints and muscles
Tactile receptors
provide sensations of touch (fine = detailed, crude = little info), pressure, and vibration
reflex
rapid, automatic responses to specific stimuli
processing site
(where interneuron is) spinal reflexes and cranial reflexes
sensory homunculus
("little man") maps somatic sensations to discrete areas in cortex functional map of primary sensory cortex head, face, lips, fingertips, hands require larger patch of
steps in reflex arc
- arrival of stimulus and activation of receptor - activation of sensory neuron - information processing - activation of motor neuron - response of peripheral effector
After injuring her back, 22-year-old Tina exhibits a positive Babinski reflex. What does this imply about her injury?
Can indicate damaged higher centers or descending tracts in adults
During a withdrawal reflex, the limbo the opposite side is extended. this response is called a crossed extensor reflex. collateral interneurons branches
During a withdrawal reflex of the foot, what happens to the limb on the side opposite the stimulus? What is this response called?
flexor reflex
Grabbing an unexpectedly hot pan causes pain receptors in hand to be stimulated
quadriceps
In the patellar reflex, identify the response observed and the effectors involved moderate extension of the leg at the knee joint
Identify the basic characteristics of polysynaptic reflexes.
Responsible for automatic actions involved in complex movements (walking/ running) - involve pools of interneurons - intersegmental in distribution (multiple levels of spinal cord involved) - involve reciprocal inhibition (inhibit antagonistic muscle, and activate muscle wanted) - have reverberating circuits, which prolong the reflexive motor response (positive response of interneurons, pools of interneurons) - several reflexes may cooperate, which produce a coordinated, controlled response ipsilateral - same side contralateral - opposite side
Describe the three classes of mechanoreceptors
Tactile receptors baroreceptors proprioceptors
Lateral spinothalamic tracts (sensory pathway)
Which spinal tracts carry action potentials generated by nociceptors?
Stretch reflex
best known monosynaptic reflex, provides autonomic regulation of skeletal muscle length ex: patellar reflex
chemical receptors
chemical concentrations
baroreceptors
detect pressure changes in blood vessels
Describe the various classifications of reflexes
developmental nature of response complexity of circuit processing site
What purpose does reflex testing serve?
diagnostic testing: Absence of response may indicate damage to descending tracts
Define reinforcement as it pertains to spinal reflexes.
enhancement of spinal reflexes, it occurs when the postsynaptic neuron enters a state of generalized facilitation caused by chronically active excitatory synapse.
corticospinal tracts
motor pathway Provide conscious control over skeletal muscles that move various body areas
central adaptation
occurs along CNS sensory pathways (brain or spinal cord) and generally involves inhibition nuclei along pathway (usually thalamus) Ex: smell adapts, strong scent
peripheral adaptation
occurs at receptor and receptor activity decreases with time - tonic receptor: always low level of activation, action potential frequency changes with stimulus (nociceptors) less likely to adapt - phasic receptor: either on or off (more likely to be adaptive) Ex: thermoreceptors - get in shower, very hot, get used to hit, need to turn water heat up because you're used to it - adapts to certain range of heat Nociceptors (pain receptors) not likely to adapt
Nociceptors
pain
mechanoreceptors
physical distortion
nature of response
somatic reflexes (skeletal muscle) and visceral reflexes (cardiac muscle, smooth muscle, glands, adipose tissue)
What are common characteristics of reflexes?
stimulus, interneurons processing, minimal synaptic delay, immediate, involuntary, predictable, preserve homeostasis
Thermoreceptors
temperature