Princeton Review Ch 8 - Nervous and Endocrine System Flashcards
Cranial versus spinal nerves.
Cranial nerves convey sensory and motor information to and from the brainstem. 12 pairs.
Spanish nerves convey sensory and motor information to and from the spinal cord. 31 pairs.
Vagus nerve function.
A cranial nerve that affects the heart and GI tract. Functions to decrease HR and increase GI activity, as such it is part of the parasympathetic division of the ANS.
What do all somatic motor neurons of the PNS have in common?
All somatic motor neurons innervate skeletal muscles, use Ach as their NT, and have their cell bodies in the brain stem or ventral portion of the SC.
What do all somatic sensory neurons of the PNS have in common.
All somatic sensory neurons have a long dendrite extending from a sensory receptor toward the soma, which is located just outside the CNS in a dorsal root ganglion. The DRG is a bunch of somatic and autonomic sensory neuron cell bodies located just dorsal to the spinal cord. The first synapse occurs in the CNS, either in the cord or all the way up to the brain stem.
DRG.
The DRG is a bunch of somatic and autonomic sensory neuron cell bodies located just dorsal to the spinal cord. The DRG are protected within the vertebral column but are outside of the meninges (protective sheath of the brain and cord).
Autonomic PNS organization.
The preganglionic neuron has its cell body in the brainstem or SC. It sends an axon to an autonotmic ganglion, located OUTSIDE of the SC. In the ganglion, the axon synapses with a post-ganglionic neuron. The postganglionic neuron sends an axon to an effector (smooth muscle or gland).
All parasympathetic postganglionic neurons release?
Acetylcholine (ACh) as their NT
Nearly all sympathetic postganglionic neurons release…
Norepinephrine as their NT
Sympathetic NS versus Parasympathetic NS in terms of preganglionic axon, postganglionic axon, and ganglia.
Sym: Pre - short (ACh NT); ganglia is close to cord, far from target; Post - long (NE is NT)
Para: Pre - long (ACh NT); ganglia is far from cord; Post - short and close to target (ACh is NT)
Describe the anatomy of the Adrenal Gland and which parts secrete what.
1) Medulla: inner portion; part of the sympathetic NS; upon activation of the SNS, the adrenal gland is stimulated to release epinephrine hormone; effects are rapid but short-lived
2) Cortex is an important endocrine gland that releases glucocorticoids (main one is cortisol) and mineralocorticoids (main is is aldosterone), and some sex hormones.
Exteroreceptors versus interoreceptors.
Sensory exteroreceptors detect stimuli from the outside world. Interorecpetors respond to internal stimuli.
Mechanoreceptors.
Respond to mechanical disturbances.
Mechanoreceptors: Pacinian corpuscles, auditory hair cells, and vestibular hair cells.
1) Pressure sensors located deep within the skin. When the corpuscular MB is distorted by the pressure of the skin, the nerve ending becomes depolarized.
2) Hair cells are found in the cochlea of the inner ear and detects vibrations from sound waves
3) Vestibular hair cells are located in semicircular canals of the inner ear and detect acceleration and position relative to gravity.
Chemoreceptors. Give two common examples.
Respond to chemical changes.
1) olfactory: detect airborne chemicals and allows us to smell things.
2) gustatory receptors are taste buds.
3) also chemoreceptors in the walls of the carotid and aortic arteries that respond to changes in arterial pH, PCO2, and PO2 levels.
Nociceptors.
Pain receptors, which are simulated by tissue injury. These can be somatic or autonomic. Autonomic is not always detected but they give the sensating of aching pain.
Thermoreceptors.
Stimulated by changes in temperature. Falls into three categories: cold sensitive, warm sensitive, and thermal nociceptors, which detect painful hot stimuli.
Electromagnetic receptors
Stimulated by EM waves. Humans only have rods and cones. But in some animals, electroreceptors and magnetoreceptors are separate. Some fish can detect e fields. Some birds use magnetoreceptors to sense the Earth’s B-field, which helps them during migration.
All sensory receptors need to encode relevant information regarding the nature of the stimulus being detected. Give 4 properties that need to be communicated to the CNS.
1) Stimulus modality: type of stimulus - the CNS determines this based on which type of receptor is firing
2) Location: communicated by the receptive field of the sensory receptor
3) Intensity: Coded by the frequency of action potentials. The range of intensities that can be detected by sensory receptors can be expanded by including multiple groups of receptors with limited ranges to detect a wider range over alll; ex. cones and vision
4) Duration: may or may not be coded explicitly. Tonic receptors fires AP as long as the stimulus is present. Phasic receptors fires AP only when the stimulus beings.
Adaptation.
The decrease in firing frequency of action potentials when the intensity of the stimulus remains constant. Nociceptors are the only ones that don’t adapt because pain is the body telling us to do something about it.
Proprioception.
Awareness of self (body part position)
Muscle spindle, Golgi tendon organs, and joint capsule receptors.
1) A mechanoreceptors specialized to detect muscle stretch. 2) GTO - monitors tension in the tendons
3) Detect pressure, tension, and movement in the joints.
By monitoring all of this activity, we can coordination motion. The cerebellum is primarily responsible for this.
How is gustation accomplished?
Taste receptors or taste buds can detect 5 flavors. Each one responds most strongly to ONE of these 5 stimuli. The bud is contains a taste pore with taste hairs that detect food chemicals. Info is transmitted via a cranial nerve to an area of the brain’s temporal lobe.
How is olfaction (smelling) accomplished?
There are olfactory receptors in the roof of the nasopharynx (nasal cavity). The receptors detect airborne chemicals that dissolve in the mucous membranes of the nose. Olfactor nerves project directly to the olfactory bulb of the brain, located in the temporal lobe.
Outer ear components.
Auricle, pinna and external auditory canal.
Middle ear components.
The middle ear is divided from the outer ear by the tympanic membrane or eardrum. The middle ear consists of 3 small bones called the malleus (hammer), incus (anvil), and the stapes (stirrup). The stapes is attached to the oval window, the MB that divides the middle and inner ear.
Inner ear components.
Structures of the inner ear include the cochlea, the semicircular canals, and the utricle and saccule. The semicircular canals are important for a sense of balance. The round window is a membrane-covered hole in the cochlea that relieves pressure. The Eustachian tube is the passageway from the back of the throat to the middle ear; equalizes pressure on both sides.
Function of the round window.
The round window is a membrane-covered hole in the cochlea that relieves pressure.
The function of the Eustachian tube (auditory tube)
The Eustachian tube is the passageway from the back of the throat to the middle ear. It functions to equalize pressure on both sides of the eardrum and is the cause of the ear popping one experiences at high altitudes or underwater.
Mechanism of hearing, from outer to middle ear.
Sound waves enter the external ear into the auditory canal, causing the eardrum to vibrate. The malleus attached to the eardrum receives the vibrations, which are passed on to the incus and then to the stapes, which contacts the oval window and.
Mechanism of hearing from middle ear to inner ear.
The vibration of the oval window creates pressure waves in the perilymph and endolymph, the fluids in the cochlea. The pressure waves in the endolymph cause vibration of the basilar membrane, a thin MB extending throughout the coiled length of the cochlea. The basilar MB is covered with hair cells, which are auditory receptors with cilia on the top. The hairs contact the techtorial MB, and when the basilar MB moves, the hairs are dragged across the tectorial MB and they bend. The displacement opens ion channels in the hair cells, which results in NT release. Dendrite from bipolar auditory afferent neurons are stimulated by this NT, and thus sound vibrations are convereted to nerve impulses.
