Reflexes

Define reflex

Involuntary, fast, automatic response to a specific sensory stimulus

Protective and can integrate motor movements to functions in a coordinated manner, important in diagnosis/localisation of neurologic lesions

Define areflexia

Absence of reflexes

Define hyperreflexia

Increased or overreactive reflexes

Define hyporeflexia

Decreased reflexes

Define innate reflex

Basic neural reflexes, formed before birth and disappear with age (maintained if useful)

Grasp reflex in babies

Define acquired reflex

Rapid, automatic learned motor patterns

Define visceral reflex

Autonomic

Control of heart rate

Define somatic reflex

Stretch

Patellar reflex

Define spinal reflex

Spinal cord = integration centre but sometimes info goes to the brain

Define cranial reflex

Only brain = integration centre

Pupillary reflex

Define monosynaptic reflex

One synapse involves

Patellar reflex

Define polysynaptic reflex

More than one synapse involved

Withdrawl reflex

Describe the five components of reflex arc

Sensory receptor = activated in response to stimulus

Sensory neuron = conducts impulses from receptor to control centre

Control center = one or more regions within CNS that relay impulses from sensory to motor neurons

Motor neuron = conducts impulses from control center to effector

Effector = muscle or gland that responds to motor nerve impulses

Define stretch spinal reflex

Monitor muscle length - patellar reflex

Receptors = muscled spindles which are activated when muscle stretches

Define tendon spinal reflex

Monitors external tension produced during muscular contraction to prevent tendon damage, causes muscle relaxation

Receptor in muscle tendon = golgi tendon organ, activated by tendon stretching

Define flexor/withdrawl reflex

Automatic withdrawl of threatened body part when pain receptors (nociceptors) are activated, involves polysynaptic ipsilateral reflex arc

Define crossed extensor reflex

Ipsilateral withdrawl reflex and a contralateral extensor reflex

Contralateral extensor reflex = when you pull your foot back from something sharp, the opposite leg muscles respond to maintain balance