Lab #5: Reflex Arcs, Cutaneous Receptors, and Referred Pain

neural reflexes

involve negative feedback (reacting) and feedforward (anticipatory)

somatic reflex

autonomic response to a stimulus that involves contracting skeletal muscles

monosynpatic

a single synapse between afferent and efferent neurons

polysynaptic

two or more synapses involved

autonomic/visceral reflexes

involuntary reflexes that control internal organs

spinal autonomic/visceral reflexes

urination, defecation (modified by thought, emotion, & stress)

brain autonomic/visceral reflexes

heart rate, blood pressure, breathing

brainstem autonomic/visceral reflexes

sneezing, coughing, swallowing

emotion-driven autonomic/visceral reflexes

butterflies in stomach, blushing, blanching

skeletal muscle reflex

involuntary response of a muscle to a stimulus (stretch or tap)

3 types of proprioceptors

muscle spindles, golgi tendon organ, joint receptors

muscle spindles

monitors muscle length and prevents overstretching

tonically active

at rest, the muscle spindles are stretched to activate sensory neurons

muscle tone

amount of tension in muscles

golgi tendon organ

triggers reflex inhibition to relax the muscle before it gets damaged

joint (knee) receptors

tap stretches quad muscles and activates spindles, relaxes hamstrings at the same time

movement

highly integrated, require input from multiple regions of the brain

reflex movement

quick and automatic, can still be modified by CNS

postural reflex movement

maintain body position, requires continuous sensory input

voluntary movement

can be initiated without external stimuli, muscle memory

rhythmic movement

walking, running, combo of reflex and voluntary

clonus

involuntary, rhythmic muscle contractions and relaxations

Sensory receptors detect -, -, and -

touch, pain, temperature

Action potential

signal to transmit info along the cell, language of nerves

the -, -, and - have the most touch receptors and motor innervation

hands, lips, face

homunculus

visual representation of sensory and motor cortical areas

two-point test

measures how close 2 points can be felt separately, uses calipers

sensory adaptation

responds stronger to new stimuli but stops responding if the stimulus is constant (temp and smell)

referred pain

the brain misinterprets sensory signals, leading to perceived pain in a different location

how to test referred pain?

tap the ulnar nerve in elbow (bt olecranon process and medial epicondyle) and the sensation is felt in pinky

phantom pain

amputees feel pain in missing limb bc the brain region responsible for that limb remains active

how to fix phantom pain?

mirror therapy tricks the brain into thinking the missing limb is still there

spinal cord movement

integrates spinal reflexes and contains central pattern generators

brain stem and cerebellum movement

control postural reflexes, hand, and eye movement

cerebral cortex and basal ganglia movement

responsible for voluntary movement, reflex movement don’t require CNS input

alpha motor neurons

fire and muscle contracts

gamma motor neurons

fire at the same time, shortening ends, lengthening central region, spindle remains active