Spinal Cord and Spinal Reflexes

Gross Spinal Anatomy Connects brain to body carries impulses to and from brain. Extends from brain to L1 Braches to create spinal nerves Classified as mixed nerves – made of afferent and efferent fibers 31 pairs – how are these pairs broken up? Cervical Thoracic Lumbar Sacral Coccygeal Named by vertebra above* *

End of the spinal cord

Spinal Meninges Meninges – membranes around the spinal cord Provide shock absorption and stability 3 layers Dura mater – outer most Epidural Space Arachnoid mater – middle layer Subarachnoid space with CSF Pia mater – inner most

Sectional Spinal Cord Label this picture A little help from Edukite Learning

Spinal Cord Parts White matter – myelinated axons Gray matter - neuron cell bodies, neuroglia, and unmyelinated axons Dorsal Root – Sensory Ventral Root – Motor Dorsal Ramus – Provides innervation to dorsum Ventral Ramus – Provides innervation to ventrolateral body Ganglion – bundles of cell bodies

Reflexes Rapid automatic responses to a stimulus

Reflex Arc Receptor Sense change in the internal or external environment. Sensory Neuron Action potential moves along neuron to spinal cord Information Processing Creates an excitatory postsynaptic potential and stimulates a motor response Motor Neuron Carries action potential from spinal cord to periphery Effector Releases neurotransmitter and causes reaction

Reflex Classification Innate Reflexes Form during development Examples: Blinking when eyelashes are touched Acquired Reflexes Learned over time Examples: Slamming on the brakes

Reflex Classification Spinal Reflexes Processing is in spinal cord Cranial Reflexes Processing is in brain

Reflex Classification Somatic Reflexes Involuntary control of the muscular system Why is it involuntary if we have control of our skeletal muscles? Autonomic Reflexes Controls other systems Also known as visceral reflexes

Reflex Classification Monosynaptic Reflexes Only one synapse Little delay Example: Stretch Reflex Patellar Reflex What happened in the lab yesterday? Postural Reflex Polysynaptic Reflexes More than one synapse A little more delay Example: Tendon Reflex – inhibitory responseinhibitory response Withdrawal reflexes with reciprocal inhibition Crossed Extensor Reflex What happened in the lab?

Polysynaptic Reflexes 1. Pools of interneurons Can cause excitation or inhibition 2. Intersegmental Extend across spinal segments 3. Involve reciprocal Inhibition Contraction of one muscle with the inhibition of another 4. Reverberating circuits Maintains stimulation 5. Reflexes may cooperate to produce one response Contraction and inhibition at the same time

Control of Spinal Reflexes Brain can overpower some reactions Examples?? Did this happen at all yesterday?

Plantar Reflex Stroke bottom of foot from side of sole to toes Reaction in adults: curling of toes Negative Babinski reflex Reaction in children: fanning of toes Positive Babinski reflex Why would the reflex produce different results at different ages?

Practice A little help from Khan Academy With your table, come up with a physiological description of one of the reflexes that we did in the lab yesterday? Knee-jerk Ankle-jerk Cross Extensor Reflex Plantar Reflex