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DeliaHanlySpin (Reflexes and their roles in nervous system function. -…
DeliaHanlySpin
Reflexes and their roles in nervous system function. - Reflex = INVOLUNTARY motor response to stimulus - occurs WITHOUT action of the cerebral cortex - don't go through the brain so remain even if spinal cord is severed.
Reflex Pathway
1 - A receptor -detects stimulus (pain, temp, muscle stretch, etc)
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4 - Efferent neurons - carry motor info FROM the CNS - cell bodies in interior or lateral horns of gray matter - some stimulated, others inhibited in the integration center
5 - Effector - myocytes, glands, etc.. - produce physical response - most are ipsilateral response (stimulus and action on same side of the body. Some may be contralateral response from OPPOSITE sides of the body
Types of reflexes
Inborn - ones you are born with (blinking, swollowing, coughing) do NOT change through life
Learned - ones you learn as you grow - potty training, talking - CAN BE CHANGED through life
Deep tendon Reflex - stretch reflex - knee jerk reflex - monosynaptic reflex because only there is only one synapse in the circuit (about 50 milliseconds)
Superficial reflex - gental stimulation of the skin - planter reflex (tests for Babinski sign - how the toes move) - changes as a person learns to walk - important neurological test for spinal cord damage
Anatomy of the Spinal cord and nerves. The spinal cord is surrounded by coverings called meninges.
Gross Anatomy
Dura Mater - (Tough Mother) - Thick outer covering of the spinal cord, Outside of dura, epidural space (for injections), not part of meninges or spinal cord.
Subdural space between Dura and Arachnoid layers, only occurs with injury or leakage (subdural hematoma - bleeding on the spine)
Arachnoid Mater - (Middle Layer) - like spider webs - thin and delicate
SubArachnoid - space beneath arachnoid - contains cerebrospinal fluid and blood vessels. (Spinal fluid drawn with spinal or lumbar puncture).
Pia Mater - Tightly bound, extremely thin, in direct contact with the spinal chord.
Spinal nerves run out to the periphery from the spinal cord through holes in the vertebrae called intervertebral foramen. - there are 31 pairs.
Cross-Sectional anatomy
White Matter - Myelinated axons that run up and down the spinal chord - carry sensory and motor information to and from higher-level processors in the brain. - Sensory runs UP the POSTERIOR (back) and DOWN the ANTERIOR (front)
Cross control - right brain - left side, left brain - right side
Gray Matter - Neuron cell bodies - UNmyelinated axons, dendrites near cell bodies, glial cells. - coordinate the transform from white matter and processing back to motor. Also send information into white matter that needs to go to the brain for processing.
looks like butterfly with 4 points of the wings being the gray horns - posterior horns send sensory processing, anterior horns sending motor signals.
Anterior midline in a space called the ventral median fissure, axons leave through the ventral root leading to the motor (efferent) neurons.
Posterior midline is in a space called dorsal median sulcus.- axons enter through the dorsal nerve root ending in dorsal root ganglion - Carry sensory (afferent) neurons.
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Nerves
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Spinal Nerve Plexuses (4) - Network of nerve fibers with no associated cell bodies - extend outward from vertebral column to stimulate the periphery
2 plexuses cervical level - composed of axons from spinal nerves C1-C5. branch to the posterior neck and head, phrenic nerve (connects to the diaphragm at the base of the thoracic cavity.) - Other one from spinal nerves C$-T1 - Brachial plexus - nerves of the arms
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Sacral level - from nerves L4, L5 and S1-S4 - Sciatic nerve
NO thoracic plesus - spinal nerves goes to the intercostal nerves found between the ribs. these articulate with the vertebrae surrounding EACH spinal nerve
Dermatomes - an area of skin supplied by a single spinal nerve. As unique as individual fingerprints.- clinical significance in diagnosing certain diseases. pain or rash pathway can show viral infection from a virus laying dormant in the ganglia (i.e. Varicell zoster virus - Chicken Pox or Shingles)