A&P I, Dr. Bailey
Test 5 Study Guide
Chapter 15 Sensory Pathways and the Somatic Nervous System





The general senses describe our sensitivity to temperature, touch, pressure, vibration, pain
and proprioception. The involve receptors that are relatively simple in structure and distributed
throughout the body.
The special senses include hearing, smell, taste, vision and balance (equilibrium). These
sensations are provided by receptors that are structurally more complex than those of the
general senses.
In order for a sensation to become a perception,it must received by the somatosensory
cortex.
Examples of sensory stimuli include touch, warmth, pain. vibration
General sensory receptors are classified by the type of stimulus that excites them:
o Nociceptors are pain receptors. Endorphins can reduce perception of sensations
initiated by, nociceptors.
o Thermoreceptors are temperature receptors. Thermoreceptors are found within the
dermis, are free nerve endings, for "cold" are structurally indistinguishable from those
for "warm,” are more numerous for cold than for warm temperatures.
o Mechanorecptors are sensitive to stimuli that distort their plasma membranes.
Mechanoreceptors detect pressure, touch, vibration, muscle length.
 Mechanoreceptors that respond to changes in blood pressure are called
baroreceptors. Baroreceptors.are receptors in the aorta that monitor the blood
pressure.
 Receptors that monitor the position of joints belong to the category called
proprioceptors.
 Tacticle receptors provide the closely related sensations of touch, pressure, and
vibration
 Tactile receptors composed of capsules that surround a core of collagen
fibers intertwined with dendrites are called Ruffini corpuscles.
 A tactile receptor composed of highly coiled dendrites that are surrounded by
modified Schwann cells and a fibrous capsule is a tactile (Meissner)
corpuscle.
 A very large, fast-adapting tactile receptor that is composed of a single
dendrite enclosed by concentric layers of collagen is a lamellated corpuscle.
 A fast-adapting tactile receptor that monitors movements across the body
surface is a root hair plexus.
Chapter 16 The Autonomic Nervous System and Higher Order Functions

The parasympathetic division of the autonomic nervous system (craniosacral division)
is said to function during "rest and digest.” It is especially active during the period of digestion
and increases gastric motility.
1









The sympathetic division of the autonomic nervous system (thoracolumbar division)
functions during “fight or flight.” During sympathetic activation, elevated heart rate, elevated
blood pressure, sweating, elevated blood glucose , dilation of the pupils, increased blood flow
to skeletal muscles. Postganglionic sympathetic axons can release the neurotransmitters
acetylcholine, nitric oxide, norepinephrine, Ach at their effector junctions.
The celiac ganglion innervates the stomach, liver, pancreas, spleen
Sympathetic and parasympathetic fibers that innervate the heart pass through the cardiac
plexus.
The suprarenal medullae contain both epinephrine and norepinephrine. Ganglionic
neurons in the suprarenal gland release epinephrine into blood capillaries.
Nicotinic receptors occur on ganglion cells of both the parasympathetic and sympathetic
divisions. They open chemically-gated sodium ion channels.
Muscarinic receptors are normally activated by acetylcholine.
States of consciousness
o The conscious state is maintained by the reticular activating system. Based on
stimulation studies, the "headquarters" of the reticular activating system appears to
be based in the midbrain.
o A state of unconsciousness in which an individual can be aroused by normal stimuli is
sleep.
o A state of unconsciousness in which an individual cannot be aroused even by strong
stimuli is coma.
o The brain waves produced by normal adults while resting with their eyes closed are
alpha waves.
o In deep sleep the EEG pattern is characterized as "slow wave."\Hallucinogenic drugs,
such as LSD, function by stimulating serotonin receptors.
Neurotransmitters influence brain chemistry and behavior
o The inherited brain disorder Huntington's disease is caused by the destruction of
basal nuclei that use different neurotransmitters. One neurotransmitter is acetylcholine
and the other is GABA.
o Depression is a mental illness is often improved by drugs that block serotonin reuptake?
Aging produces various structural and functional changes in the nervous system
o An age-related decline in mental function characterized by difficulties with spatial
orientation, memory, language, and personality is called senile dementia.
o Changes in the central nervous system that accompany aging include reduction in brain
size and weight, decrease in the number of neurons, decreased blood flow to the brain,
changes in synaptic organization in the brain.
Chapter 17 The Special Senses
o Smell
o Taste
o Gustatory receptors are located on the surface of the tongue.
o Taste receptors are distributed in the following places: portions of the larynx, anterior tip
of the tongue, portions of the pharynx, surface of the tongue
o An adult has approximately 3,000 taste buds.
o Taste buds are monitored by the follow cranial nerves: facial nerve (VII), vagus nerve
2
(X), and glossopharyngeal nerve (IX).
o Vision
o The ciliary body of the eye changes the shape of the lens for far and near vision
o The human lens focuses light on the photoreceptor cells by changing shape.
o The shape of the lens is controlled by the ciliary muscles.
o The conjunctiva covers most of the exposed surface of the eye.
o The part of the eye that determines eye color is iris.
o The opening in the iris through which light passes is the pupil.
Extra Credit: A ray of light entering the eye will encounter these structures in this order:
conjunctiva → cornea → aqueous humor → lens → vitreous body → retina → choroid
For the picture above, be able to identify: fovea, retina, anterior chamber, suspensory ligaments,
cornea.
3
For the picture above be able to identify the tympanic membrane, oval widow (the structure that
covers up the stapes), vestibule, auditory ossicles, cochlea (the structure contains the
receptors for hearing)
4