Week 4 - Sense Organs Flashcards
What is Peripheral Nervous System?
- Nerves and ganglia (collection of neurosoma outside of CNS)
- Cranial nerves (connects to brain, 12 pairs)
- Spinal nerves (connect to spinal cord, 31 pairs)
What is the Anatomy of a Nerve?
- Bundle of neuron axons in PNS
- Carry sensory neurons, motor neurons or both
- Neuron axons bundled together by connective tissue
What is Cranial Nerves?
- Serve head and neck mainly
- Only vagus nerve pair (NCX) extend to thoracic and abdominal cavities
- Most are mixed nerves
What is Spinal Nerves?
- Formed by the combination of the anterior and posterior roots of spinal cords
- Named by the vertebral region from which they emerged
- Spinal nerves divides into posterior ramus (skin, muscle and joints of back) and anterior ramus (forms complex of networks for lateral and anterior trunk)
- Thoracic and upper lumbar spinal nerves also carry motor output of sympathetic division of ANS
What is the Autonomic Nervous System (ANS)?
- Motor subdivision of PNS
- Two motor neurons - Myelinated pre-ganglionic and unmyelinated post-ganglionic fibre
- Regulates cardiac and smooth muscle and glands
List the two subdivision of ANS?
Sympathetic:
- Fight or Flight
- E Division - Exercise, excitement, emergency and embarrassment
Parasympathetic:
- Calming effect, conserving energy, housekeeping
- D Division - Digestion, defecations and diuresis
Define Sympathetic?
- Originates from spinal nerves
- Ganglia are sympathetic trunk, collateral ganglia and adrenal medulla
- Short pre-ganglionic and long post-ganglionic neuron
Define Parasympathetic?
- Originates from cranial nermes in brain stem and spinal nerves
- Vagus nerve provides 75% of all parasympathetic outflow
What are the special senses?
- Sight
- Hearing
- Equilibrium
- Smell
- Taste
- Pain
What is pain?
- Alerts us to hazards but also helps us with illness
- Somatic pain - skin, muscle and joints
- Visceral pain - Organs
How do we process pain?
- Injured tissues releases chemicals that stimulate Nocireceptor (hurt) of first order neuron e.g prostaglandins
- Signal travels up spinal cord to thalamus in second order neuron
- Thalamus relays signals through third order neuron to cortex where we perceive pain
What are the pain signal destinations?
First Order Neuron:
- Nocireceptor
Second Order Neuron:
- Spinothalmic tract for somatic responses
- Spinoreticular tract for visceral responses
- Reticular formation
- Hypothalamus and limbic system
Third Order Neuron:
- Thalamus
What is referred pain?
- Pain in viscera often mistakenly though to come from skin
- Due to sharing same interneuron in spinal cord
- Brain cannot distinguish source
What are pain relieving mechanisms?
- Endogenous opioids
- Internally produces opium like substances (endorphins and enkephalins)
- Block pain signals from the nocireceptors traveling up the spinal cord to brain
- Labor, exercise therapy for chronic pain
What is taste (gustation)?
- Taste buds (4000) house taste cells
- Taste buds on:
- Superior surface of tongue
- Soft palate, cheeks, pharynx and epiglottis
