Lecture 9 - Reflexes

Question 1

Reflex

Answer 1

Rapid automatic response to a stimuli through the spinal cord (without the involvement of the brain).

Example: blinking, coughing, knee-jerk, salivation, shivering, pain response

Question 2

Reflex Arc

Answer 2

Neural pathway that mediates in a reflex action.

Question 3

5 components of a Reflex Arc

Answer 3

1. Sensory receptor
2. Sensory nerve (afferent neuron)
3. Interneuron (synapse)
4. Motor nerve (efferent neuron)
5. Target organ (muscle or gland)

Question 4

Sensory receptor

Answer 4

Receives information and generates impulses.

Question 5

Primary (sensory receptor)

Answer 5

Neuron with the specialized region for stimulus transduction.

Question 6

Secondary (sensory receptor)

Answer 6

Non-neuronal cell specialized for stimulus transduction, which stimulates neuronal cell through neurotransmitter.

Question 7

Innate reflexes

Answer 7

Result from the connection of neurons that form during normal development, are genetically determined.

Ex: Withdrawal from pain, blinking and sucking

Question 8

Acquired reflexes

Answer 8

Rapid and automatic but are learned responses.

Ex: Salivation when smelling food

Question 9

Somatic reflexes

Answer 9

Control activities of the muscular system

Question 10

Visceral reflexes

Answer 10

Autonomic involuntary reflexes, control the actions of smooth and cardiac muscles and glands

Question 11

Spinal reflexes

Answer 11

Control the activities of the muscular system?

Question 12

Cranial reflexes

Answer 12

Reflexes processed in the brain

Question 13

Monosynaptic reflexes

Answer 13

Sensory neuron synapses directly with the motor neuron. There is little delay between sensory input and motor output. CONTROL THE MOST RAPID REFLEXES.

Question 14

Polysynaptic reflexes

Answer 14

At least one interneuron between sensory afferent and motor efferent. Longer delay between stimulus and response.

Length of the delay is proportional to the # if synapses involved.

Can produce far more complicated responses than monosynaptic reflexes as the interneurons can control several muscle groups.

Question 15

Unconditioned reflexes

Answer 15

Inborn reflex, inherited and are shown from birth onward, and present in all individuals and animals.

Example: withdrawal from pain.

Question 16

Conditioned reflexes

Answer 16

Not inherited, learn by doing the same act several times

Ex. salivation when smelling food

Question 17

Muscle spindles

Answer 17

Sensory receptors within the belly of a muscle that primarily detect changes in the length of the muscle. Detect stretch & protect the muscle.

Composed of 3-12 intrafusal muscle fibers.

Question 18

Muscle spindle receptor

Answer 18

Encapsulated group of specialized (intrafusal) skeletal muscle fibers supplied with BOTH motor and sensory innervation.

Question 19

Extrafusal fibers

Answer 19

Regular contractile tissue, innervated by alpha-motor neurons, stimulates contraction.

Question 20

Intrafusal fibers

Answer 20

Sense organs within muscle fibers. Innervated by gamma-motor neurons.

Question 21

Golgi tendon organ

Answer 21

Senses stretch in tendons - feeds back on alpha-motor neurons

Question 22

alpha-motor neurons (from brain stem and spinal cord) innervate the ________ fibers.

Answer 22

extrafusal

Question 23

Gamma-motor neurons (from pons) innervate the _______ fibers. Function to keeping muscle spindles _________ during muscle contraction. Serves as the volume control of muscle fibers.

Answer 23

1. intrafusal
2. stretched

Question 24

With increases stretch, afferents from the muscle spindle stimulate _______ neurons to _________.

Answer 24

1. alpha-motor
2. contract and relieve the stretch

Question 25

Golgi tendon reflex

Answer 25

Skeletal muscle contraction causes the agonist muscle to simultaneously lengthen and relax.

Question 26

Reinforcement

Answer 26

facilitation that enhances spinal reflexes

Question 27

Plantar reflex

Answer 27

causes a downward response (flexion)

Question 28

Babinski reflex

Answer 28

upward response (extension)

Question 29

Lower motor neurons

Answer 29

Classically defined as alpha-motor neurons. Originated from brainstem and spinal cord.

Disease: paralysis and/or atrophy. losses of sensory neurons.

Question 30

Cell bodies and dendrites are in the CNS and whose axons extend to peripheral nerves and synapse on the _________.

Answer 30

extrafusal skeletal muscle fibers

Question 31

Upper motor neurons

Answer 31

Neurons of the CNS that influence the lower motor neurons.

Disease: inappropriate movement (seizures, circling), exaggerated segmental reflexes such as crossed extensor reflexes.