Essay Questions : Chapte 7,13,14 Flashcards
Describe the pathway through which sound information travels from the environment to the organ of Corti.
Sound waves enter the pia travel from the outer ear down the auditory canal and cause the tympanic membrane (eardrum) to vibrate.
These vibrations are then transferred to the three ossicles – the small bones of the middle ear. Malleus (hammer), incus(anvil) and the stapes (stirrup)
The vibrations of the stapes trigger vibrations of the the oval window, which in turn transfers the vibrations to the fluid of the snail-shaped choclea.
The cochlea is a long coiled tube with an internal membrane running almost to its tip. This internal membrane is the auditory receptor organ, the organ of Corti.
Explain the anatomical organization/structure of the organ of Corti. What is the relationship between pitch perception and the organ of Corti.
- The organ of Corti is composed of two membranes: the basilar membrane and the tectorial membrane.
- The auditory receptors,(hair cells), are mounted in the basilar membrane. And the tectorial membrane rests on the hair cells.
- At the same time deflection off the organ of Corti at any point along its length causes a force on the hair cells.
- This force stimulates the hair cells, which in turn increase firing in axons of the auditory nerve. The vibrations of the cochlear fluid are dissipated by the round window, and elastic membrane in the cochlea wall.
- The cochlea is sensitive and creates different frequencies. The higher frequencies (pitch) produce greater activation closer to the windows and lower frequencies produce greater activation at the tip of the basilar membrane.
- The frequencies that compose each complex sound activate hair cells at many different points along basilar membrane—the many signals created by a single complex sound are carried out of the ear by many different auditory neurons
What is the pathway through which auditory information travels in the central nervous system, beginning at the hair cells?
- The auditory nerves synapse in the ipsilateral cochlear nuclei, from which many projections lead to the superior olives on both sides of the brain stem at the same level. ‘
- The axons of the olivary neurons project via the lateral lemniscus to the inferior colliculi, where the synapse of neurons that project to the medial geniculate nuclei of the thalamus, which in turn project to the primary auditory cortex.
- Signals from each ear are combines at a very low level and transmitted to both ipsilateral and contralateral auditory cortex.
Compare and contrast the characteristics of the four types of cutaneous receptors found in human skin.
- Free Nerve Endings – sensitive to temperature changes and pain; simple
- Pacinian Corpuscles – detects mechanical stimuli, especially vibrations, larger receptive fields, fast adaptin; largest and deepest appear onion-like; responds to sudden displacements of skin, but not to constant pressure
- Meissner’s Corpuscles – touch sensitive, small receptive fields, fast adapting
- Merkel’s Disks – touch sensitive, small receptive fields, slow adapting; help sustain touch and pressure; Ruffini Corpuscles- vibration sensitive, large receptive fields, slow adapting; helps sustain pressure
Describe the neuroanatomy of the dorsal-column medial lemniscus system and the anterolateral system. What does each system do.
a.Dorsal-column mediallemniscus system carries information about touch (kinesthetic) and proprioception.
Sensory neurons enter the spinal cord via a dorsal root, ascend ipsilaterally in the dorsal columns, and synapse in the dorsal column nuclei of the medulla.
The dorsal column nuclei axons cross over to the then ascend in the medial lemniscus and other side of the brain to the contralateral ventral posterior nucleus of the thalamus.
Anterolateral system
Carries information about pain and temperature.
Most dorsal root (decussate) neurons of the anterolateral system synapse as soon as they enter the spinal cord.
The axons of most of the second-order neurons cross over to the other side of the brain but then ascend to the brain in the contralateral anterolateral portion of the spinal cord.
The anterolateral system comprises three different tracts: the spinothalamic tract, which projects to the ventral posterior nucleus of the thalamus,
the spinoreticular tract which projects to the reticular formation and
the spinotectal tract which projects to the tectum. The three brances of the trigeminal nerve carry pain and temperature information from the face to the same thalamic sites.
The pain and temperature information that reaches the thalamus is then disturbed to SI, SII, posterior parietal cortex, and other parts of the brain.
Explain the gate-control theory and the characteristics of the descending analgesia circuit.
a. Melzack and Wall proposed the gate-control theory to account for the ability of cognitive and emotional factors to block pain. They theorized that signals descending from the brain can activate neural gating circuits in the spinal cord to block incoming pain signals.
a. Opiates inhibit the activity of inhibitory interneurons in the PAG (Periaqueductal Gray). This increase the activity of neurons whose axons descend to the raphe nuclei. The activity of axons that descend from the PAG excites the raphe neurons whose axons descend in the dorsal columns of the spinal cord. The serotonergic activity of descending dorsal column axons excites inhibitory spinal interneurons that block incoming pain signals
Describe the pathway though which olfactory information would travel through the nervous system, beginning at the olfactory receptor. At one point this information splits forming two distinct paths. What is the role of each path?
Olfactory receptors (that are located in olfactory mucosa) send information to the olfactory bulbs. Next the Olfactory bulbs sends information to the prepyriform cortex, the amygdala.
The Prepyriform cortex and Amygdala sends information to the medial dorsal thalamus and the hypothalamus.
The medial dorsal thalamus sends information to the Orbitofrontal cortex
and the hypothalamus sends information to the Lateral posterior orbitofrontal cortex
Describe the relationship between papillae, the anatomy of the tongue, and taste. What is the neuroanatomical pathway through which gustatory information travels to/through the brain.
a. On the tongue, taste buds are often located around small protuberances called papillae. Taste receptors do not have their own axons; each neuron that carries signals away from a taste bud receives input from many receptors.
b. Gustatory afferent neurons leave the mouth as part of the facial, flossopharyngeal, and
vagus cranial nerves, which carry information from the front of the tongue, to the back of the tongue, and the back of the oral cavity. These fibers all terminate in the solitary nucleus of the medulla, where the synapse on neurons that project to the ventral posterior nucleus of the thalamus. The gustatory axons of the ventral posterior nucleus project to the primary gustatory cortex, which is near the face area of the somatosensory homunculus, on the superior lip of the lateral fissure, and to the secondary gustatory cortex, which is hidden from view in the lateral fissure. Particular tastes seem to be encoded in the brain by profiles of activity in groups of neurons.
Explain the physical/anatomical relationships between the hypothalamus and the pituitary gland. What are these “systems” responsible for doing?
Even though the Pituitary Gland is considered the “Master Gland”, the hypothalamus is really the master over the pituitary gland. The reason for this is that the neurons of the hypothalamus extend down into the Posterior Pituitary. The Pituitary Gland is broken up into Anterior and Posterior Pituitary.
The Anterior Pituitary (circulatory system) was form the same tissue that becomes the roof of the mouth. It secretes hormones that act on target organs such as the thyroid (growth), adrenal cortex , and gonads (reproduction). The Posterior Pituitary (neural communication) deals with the reabsorption of water into the kidneys with the help of the peptide hormone Vasopressin. In females, it also helps with birth contractions and milk let-down with the peptide protein Oxytocin.
Explain the anatomical and hormonal components necessary for the development of the reproductive organs (both male and female). Make sure you use the appropriate terminology.
At 6 weeks after conception, each fetus has the same pair of gonadal structures called primordial gonads.
Each primordial gonad has an outer covering, or cortex, which has the potential to develop into an ova, and each has an internal core, or medulla, which has the potential to develop into testis.
Males:If the fetus is a genetic male, Sry gene on the Y chromosome of the male triggers the synthesis of Sry protein and this protein causes the medulla of each primordial gonad to grow and to develop into testis. In the third month of male fetal development, the testes secrete testosterone and Mullerian-inhibiting substance. This causes the mullerian system (female to degenerate and the testes to descend into the scrotum.
Girls: Since there is no female counterpart of Sry protein, the cortical cells of the primordial gonads automatically develop into ovaries. The development of the mullerian systems occurs in any fetus that is not exposed to testicular hormones during the critical fetal period.
Both male and female genitals develop from the same precursor. The biopotential precursor of the external reproductive organs consists of four parts: the glans, the urethral folds, the lateral bodies, and the labioscrotal swelling.
The glans grows into the head of the penis in a male, of the clitoris in the female; the urethral folds fuse in the male or enlarge to became the labia minora in the female; the lateral bodies form the shaft of the penis in the male or the hood of the clitoris in the female; and the labioscrotal swellings form the scrotum in the male and the labia majora in the female.
What are the similarities and differences between hormones in the endocrine system and neurotransmitters in the central nervous system?
a) Neural communication )
i. Telephone system – goes from one specific point to the target point
i. Rapid (MS)
i. Digitalized (all-or-none)
i. Some Voluntary Control (ex: u choose when u write
a. Hormonal communication
i. TV Broadcasting System – starts from one point but anywhere can be a target point
i. Slow (sec to min)
I. Analog (graded) the more hormone grater effect
i. Involuntary Control
a. Both
i. Production and Storage
i. Stimulation-Induced release
i. Variety
i. Receptor Molecules
i. Second Messengers
How do steroid and protein hormones work? Describe 6 of the 10 principles of hormone action discussed in class.
- Slow onset with extended duration
- After intensity or probability of behavior - do not turn a behavior on (activates)
- Reciprocal relationship between behavior (environment) and hormones - environmental factors
influence hormone release which then reacts to environment - Hormones have multiple effects, thus single behaviors or physiological changes may be governed
by multiple hormones - Not just one hormone that does one thing - Pulsatile secretion - Released in small bursts
- Rhythmic or circadian variation - Increase mating in certain times
- Induce long-term metabolic changes
- Hormones interact
- Similar chemical structure, different functions across species
- Require receptor proteins on cells to alter function
Describe the different stages of sleep based on their EEG patterns. What is paradoxical about REM sleep?
a. Waking – Beta Activity (high frequency low amplitude)
b. Prior to sleep – alpha rhythms (regular oscillation with 9-12 Hz frequency)
c. Stage 1 – (amplitude decreases, frequency become irregular, heart rate decreases, loss of muscle tone)
d. Stage 2 – sleep spindles (bursts of 12-14 Hz)
e. Stage 3 – appearance of Delta waves (large amplitude very slow waves)
f. Stage 4 – at least 50% Delta waves
g. REM or paradoxical sleep – (small amplitude, high frequency similar to waking)
Explain how we typically cycle through the stages of sleep throughout the night. How does this cycle change the longer we sleep? How is the typical cycle different in elderly individuals?
a. Awake – Stage 1 – Stage 2 – Stage 3 – Stage 4 – Stage 3 – Stage 2 – Stage 1 – REM
i. Stages shorten, or eventually don’t go down to Stage 3 and 4, staying in stage 1, 2 and REM
ii. Periodically wake for short periods of time.
iii. REM gets longer throughout the night.
a. Elderly repeatedly awake during the night
i. Less time in stages 3 they experience no 4
i. REM not distributed evenly, they go through rem during the beginning of sleep but not towards the end.
Describe the major theories attempting to explain why we sleep.
a. Theories of Restoration ( your body is physically tired)
i. Rest and Recovery – no central nervous system support
a. Theories of Adaptiation (evolution we don’t see very well at night so we can’t defend ourselves from animals, the people that slept stayed alive and reproduce and visa versa)
i. Sleeping keeps us out of trouble, normally at night, and allows us to conserve energy
