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