Lecture 17 Flashcards
What are the four major ways signals are differentiated? what do they mean?
Afferent(ascending): Information heading towards the brain.
Efferent(descending): information heading away from the brain.
Somatic: signals we are aware of e.g skeletal muscle (efferent, motor) control or temperature(afferent, sensory).
Autonomic: signals we are not aware of E.g involuntary muscle control (efferent, motor) or blood pressure (afferent, sensory)
What are the two efferent divisions of the autonomic system?
The sympathetic and the parasympathetic
Features of a somatic motor neuron:
Voluntary control, one neuron between CNS and effector, the neuron has its cell body in the spinal cord, and its axon in spinal nerves, this axon is myelinated. Ends in the neuromuscular junction synapse and releases acetylcholine (ACh).
What is a motor unit?
A single neuron which makes contact with one or several muscle fibers, note that a muscle fibre is never innervated by multiple neurons.
Features of an autonomic motor neuron:
Used for involuntary control, has two neurons between the CNS and effector, the first’s cell body is in the CNS and its axon is in the PNS, the second has both in the PNS (cell body in autonomic ganglion), controls many involuntary processes E.g smooth muscle, cardiac muscle, glands or fat tissue (adipose).
The first neuron (preganglionic) is myelinated and releases acetylcholine, the second neuron (postganglionic) is unmyelinated and uses acetylcholine OR noradrenaline, synapses onto effector organs.
What are the two autonomic subdivisions roles
sympathetic: prepares for stress responses, effects include: increased heart rate, constricting blood vessels, lowering gastric motility and salivation, increasing pupil size and sweating.
Parasympathetic: prepares body for rest, effects include: decreased heart rate, increased gastric motility and salivation and lowered pupil size.
What is the difference between the two autonomic subdivisions in terms of structure?
The sympathetic ganglion is close to CNS (cell body in the sympathetic chain ganglia, first neuron has short axon) and the first neuron leaves the CNS at thoracolumbar level (T1 to L2), releases norepinephrine. Preganglionic axon leaves CNS at cranial and sacral (craniosacral region) spinal cord levels and is relatively longer than sympathetic axon. The parasympathetic ganglia is closer to the effector organs and the second neuron releases acetylcholine.
How many pairs in the sympathetic chain ganglia? What are the collateral ganglia?
21-23 pairs, there are 3 main collateral ganglia and it contains preganglionic axons that did not make synapses in chain ganglia.
