Stanbridge - T4 - Peds - W1 - Prenatal Development & Primitive Reflexes

### PT Through the Lifecycle (PTA 1011)

• This course covers the development of the neurologic system, central nervous system (CNS) and peripheral nervous system (PNS)
• Key developmental stages are tracked, pre- and post-natal, through adolescence
• These include motor milestones and reflexes
• Learning objectives include tracing neurologic development, identifying CNS/PNS levels, and understanding developmental stages

Key Terms

• Blastocyte
• Central Nervous System
• Embryonic stage
• Germinal stage
• Peripheral nervous system
• Primitive reflexes
• Rigidity
• Tone
• Zygote

Nervous System Development

• The nervous system develops from a few cells of the primitive ectoderm, the "neural tube"
• The neural tube develops into the CNS (brain and spinal cord)
• Basic CNS form is completed by the 6th week of gestation
• Disease or injury to the developing CNS or PNS can affect a child's development
• It's important to understand how the nervous system develops

Neural Tube Defects

• Folic acid and vitamin B-12 are important during the first trimester to prevent deficiencies
• Deficiencies may cause neural tube defects
• Spina bifida can result if the posterior neural tube does not close properly

Embryonic Brain Development

• Early in development, the cerebral surface is smooth
• Folding begins in month 6, and convolutions become more obvious as development continues
• Key parts of the brain develop during this stage

Brain Development

• If cells continue to multiply and compress the cerebral aqueduct, it can lead to congenital hydrocephalus
• Hydrocephalus occurs when there's an increase in cerebrospinal fluid ("water on the brain")

Nervous System Development and Function

• The brain is the only organ not fully developed at birth
• By birth, the brain is about ¼ the size of an adult brain
• Average brain weights for birth, 6 years, and adulthood are given
• Brain consists of gray and white matter
• Myelin is an electrically insulating material forming the myelin sheath

The Lobes of the Cerebral Hemispheres

• Frontal lobe- controls cognition, awareness, abstract thinking, mood, and impulse control; also includes motor cortex and expressive language
• Occipital lobe- controls visual stimuli; includes visual cortex
• Temporal lobe- controls language, receptive language, and auditory cortex and musical discrimination
• Parietal lobe- receives sensory messages and includes primary sensory cortex (except vision and hearing)

Cerebral Hemispheres

• Two hemispheres, each with three subdivisions (cortex, subcortical white matter, and basal ganglia)
• Cortex covers the outer surface of each hemisphere
• Subcortical white matter consists of highly concentrated myelinated fibers carrying information to and from the cortex
• Basal ganglia are nuclei acting as a cohesive unit involved with motor function

Cerebral Cortex

• Plays a key role in memory, attention, perceptual awareness, language, thinking, and consciousness; divided into gyri (raised folds) and sulci (grooves)
• Allows information storage in the brain

Subcortical White Matter

• Acts in transmitting electrical impulses and controls many involuntary physical functions such as reflexes and balance- injuries to this area can cause lesions often difficult for children to recover from during development

Basal Ganglia

• A group of several structures deep in the cerebrum, involved in many functions including procedural learning, habits, routine behaviors, voluntary motor control, eye movements, cognitive emotional functions, muscle tone, and posture
• Involved in neurological conditions like Parkinson's Disease, Huntington's Disease, and OCD

Brainstem

• Consists of midbrain, pons, and medulla oblongata
• Midbrain houses efferent pathways/nuclei for the CNS, concerned with vision, auditory, and pain pathways
• Pons contains nuclei of several CNS and acts as a relay station between the cortex, cerebellum, and efferent pathways
• Medulla oblongata regulates autonomic functions, including breathing, heart rate, and blood pressure; helps with transfer of messages to the spinal cord and thalamus and is a reflex center for coughing, sneezing, and swallowing; part of the hindbrain

Cerebellum

• In Latin, means "little brain"
• Made up of tightly folded gray matter
• Important role in motor control, coordination, precision, accuracy, hand-eye coordination, fine motor skills, attention, and language

Thalamus

• Surrounds almost completely, except for olfactory nerves
• All sensory information, except for smell, passes through the thalamus on its way to the cortex
• Conveys information regarding muscle tension and limb position sense to the cortex

Peripheral Nervous System (PNS)

• Consists of nerves and ganglia outside of the brain and spinal cord
• Allows signals to travel between the cortex, spinal cord, and peripheral muscles
• Separated into somatic (cranial nerves and spinal nerves) and autonomic (sympathetic and parasympathetic divisions) systems for controlling circulation, respiration, digestion, metabolism, secretion, body temperature, and reproduction
• Afferent and efferent tracts carry sensory and motor messages

Postnatal Development (Infancy to Adulthood)

• Development is variable with a constant drive to progress from infants to toddlers, early childhood, and through middle childhood to adolescence, then young adulthood, middle adulthood and late adulthood

Normal Postnatal Development

• Is variable and there's a constant drive for overall development from infancy to adulthood.
• Factors affecting motor development are also covered, and include social-emotional development, environmental, and cultural factors

Motor Development Concepts, and Directional Concepts

• Motor development is based on prior development (like building a pyramid).
• Motor development occurs in a sequence of head-to-toe and proximal-to-distal, with flexion preceding extension
• The developmental sequence is orderly, starting with head control and progressing to rolling, sitting, creeping, and walking, which may overlap as several skills develop simultaneously

Primitive (Neonatal) Reflexes

• Reflex actions originating in the CNS, typically seen in normal infants
• Initially dominate an infant's movements, helping with development and motor control against gravity
• They usually disappear or are inhibited by the frontal lobe during normal development

Assessing Primitive Reflexes

• Symptoms
• Physical tests
• Reflex strengths (0 = integrated, 1 = moderately present/retained, 2 = strongly retained) are used to evaluate the degree of integration

Specific Primitive Reflexes (and their function and integration time):

• Rooting, Suck-Swallow, Flexor withdrawal, Crossed extension, Traction response, Grasp, Babinski, Positive Support, Walking/ Stepping Reflex, ATNR (asymmetrical tonic neck reflex), STNR (symmetrical tonic neck reflex), TLR (tonic labyrinthine reflex), Moro reflex. Galant reflex, Plantar Reflex, Palmar Grasp

Causes of Retained or Non-Integrated Primitive Reflexes

• Birth trauma
• C-section
• Premature birth
• Falls during pregnancy
• Head trauma
• Toxin exposure to mother
• Chronic ear infections
• Delayed/skipped creeping/crawling
• Anesthesia
• Neurological disease (Cerebral Palsy, autism)
• Vertebral subluxations
• Abnormal muscle tone
• Upper Motor Neuron Lesion, stroke, Traumatic Brain Injury (TBI), or multiple sclerosis

Techniques to Help Break Up Primitive Reflexes

• Specific exercises and positions are designed to help integrate, re-integrate, and decrease the influence of these reflexes.
  • Include slow angels, robot exercises, and others for specific reflexes.

Learning Assessment Questions

• Questions on the development of certain reflexes and the stages of development are included.