PBSI 235 - Exam 2 - Study Guide

COMPREHENSIVE

Differentiate between skeletal muscles (what are they made of), muscle synergists, and muscle antagonists

Skeletal muscles produce bodily motion by pulling the skeleton. Skeletal Muscles are made up of striate (overlapping layers of myosin and actin); which make up myofilaments (which control muscle contraction and give striped appearance) . Muscle Synergists are muscles that must work together to produce motion. Muscle antagonists must work in opposition to each other to produce motion.

What are the two types of muscle fiber? What sets them apart from one another?

The two types of muscle fiber are fast twitch and slow twitch. Fast twitch move fast and fatigue fast and slow twitch moves slow and fatigue slow.

Name three characteristics of motor neurons

They have cell bodies in the CNS (spinal cord); axons that form the efferent portion of the peripheral nerves; and axon terminals that synapse in muscle fibers.

How is acetylcholine released into the postsynaptic membrane in motor neurons?

The terminals of motor neurons release acetylcholine on the postsynaptic membrane.

How many motor neurons does it take to contact multiple muscle fibers?

In general, one motor neuron can contact many muscle fibers.

What pathway involves cell bodies in the primary motor cortex with axons that form synapses on motor neurons in the spinal cord?

Pyramidal motor system

What controls muscles in distinct parts of the body?

Distinct regions in primary motor cortex (M1)

Where do cell bodies in the primary motor cortex (M1) synapse?

Motor neurons on the contralateral side of the body

What direction is activity in primary motor cortex neurons associated with?

Direction of movement

Describe the non-primary motor cortex

Includes supplementary motor area and premotor cortex; broadly involved in motor planning (preplanned & reaction to external events)

What does the extrapyramidal motor system regulate? Describe one of its central Components.

Regulates pyramidal motor system; includes Basal Ganglia & Cerebellum

How do the basal ganglia and cerebellum influence motor cortices?

Through largely parallel pathways through the nuclei of ventral anterior and ventral lateral nuclei of the thalamus (VA/VL complex)

What is the effect of dopamine release?

Usually to increase movement

What environmental stimuli do specialized sensory systems detect?

Specific forms of energy (light, sound waves, etc) and Particular chemicals (odors, tastes)

Explain sensory transduction

Receptor cell converts the sensory input into an electrical signal that can be processed and interpreted by the nervous system

If two species both possess a given sense, will they perceive the same stimuli?

No; sensory receptors can be tuned differently

How many types of receptor cells can one sensory system have?

Multiple different types for Qualitative and Quantitative purposes

What are receptive fields?

Area within which a receptor cell can detect a stimulus

Differentiate between phasic and tonic receptors.

Phasic receptors display adaptation (will turn off); Tonic Receptors respond as long as the stimulus is present

Where do the earliest stages of perception occur?

In the Primary Sensory Cortex

What cortex processes touch information? Sound information?

Somatosensory is Touch; Auditory is sound

Where do association cortices receive information from?

Primary Sensory cortex and integrate inputs from multiple senses

Describe plasticity.

Change as a result of an experience (ie limb loss)

Where is the primary somatosensory cortex located?

On the postcentral gyrus in the parietal lobe

What is proprioception?

Perception of the position of limbs and body in space

Are pacinian corpuscles tonic or phasic receptors?

They are phasic receptors, they adapt quickly to constant stimulus (pressure & texture)

What determines whether or not an action potential is fired in dorsal root ganglia neurons?

Summation of generator potentials

Explain the pathway from DRG to the primary somatosensory cortex

Axons of DRG neurons travel up the spinal cords to the medulla → DRG neurons form synapses on medulla neurons → medulla neurons send axons across the midline forming synapses on neurons in Ventral Posterior Nucleus (VPN) of thalamus → VPN neurons send axons to the primary somatosensory cortex

What does the amplitude of the wave determine?

The volume, loudness, or intensity of a sound

What does the frequency of the wave determine?

Pitch (Hz)

What comprises the external ear?

Pinna and Ear Canal

Describe each of the components of the middle ear

Tympanic membrane, ossicles and oval window

Explain the role of the cochlea and its Organ of Corti.

The cochlea turns vibrations into pressure waves inside the fluid of the cochlea and then is converted to a signal the CNS understands by the organ of corti

How do certain areas of the basilar membrane differ?

Each region of the basilar membrane responds to specific sound frequency from highest to lowest

What are hair cells and what do they have that don't flex in response to sound?

Hair cells are the receptors that transduce sound into electrical activity; they have stereocilia embedded into the tectorial membrane; the tectorial membrane does not move

How is a generator potential (in hair cells) created and what does it cause?

Displacement of the stereocilia opens mechanically-gated ion channels which creates a generator potential which depolarizes the hair cell

What are the EPSPs created by glutamate (released from hair cells) able to do?

Immediately generate action potential that is conducted down cell body to vestibulocochlear nerve and into CNS

Explain auditory pathways

Spiral Ganglion neurons synapse in the neurons of the cochlear nucleus in the medulla; Axons from the cochlear nucleus cross the midline and synapse on the neurons of the superior olivary nucleus in the pons; while most axons target the contralateral superior olivary nucleus, some cochlear nucleus neurons project to the ipsilateral side

How is sound localized?

Slight differences in volume and slight differences in timing of the sound

What does the organization of the primary auditory cortex (A1) reflect?

Reflects the way the basilar membrane responds to frequencies along its length

What happens if spiral ganglion cells are deprived of input? What does this lead to or cause?

If deprived of input, spiral ganglion cells may die; causing an inability to hear sounds at the same frequency that caused damage or tinnitus

List the three directions in which the head can rotate.

Pitch, Yaw, and Roll

What do the receptors within the ampulla detect? Additionally, which structuredoes this contain (and what happens when it deflects)?

Receptors within the ampulla detects rotation of the head; contains cupula and when it defects stereocilia are displaced opening mechanically gated ion channels

Which parts of the semicircular canals detect linear motion?

Utricle and saccule

What happens when the vestibular ganglion is depolarized?

They release glutamate onto vestibular ganglion neurons

Describe the vestibular-ocular reflex

Sensation of movement in one direction causes the eye to move in the opposite direction to stabilize visual images

What are the three elements of inputs that contribute to flavor?

Taste, Smell, and somatosensory

Where are the taste buds located? What is their role in taste?

Taste buds are located inside the papillae. They respond to taste (there are 50-100 receptor cells that respond to one of five basic tastes)

What are some characteristics of filiform papillae?

Filiform papillae do not contains taste buds and instead have somatosensory receptors

What are the five basic tastes our tongues can distinguish?

The five basic tastes are salty, sweet, sour, bitter, and umami/savory

Is the ATP release caused by taste receptor cells spatially targeted?

No, ATP release is not precisely spatially targeted

Does the entrance of sodium into receptor cells hyperpolarize or depolarize thecell? How is ATP released?

The entrance of sodium (NaCl) in the receptor cells depolarizes the cell and contributes to generator potential directly. This opens voltage gated Ca2+ channels that trigger ATP release.

What kind of ion channels to taste receptors that respond to sour have? How is ATP released?

Sour taste receptors have hydrogen (H+) channels that allow hydrogen into the cell. This creates generator potential that depolarizes the cell and leads to ATP release.

Describe the action of T1R receptors for sweet taste. After they bind to sugars, what ensues?

Once T1R receptors bind to sugars, the receptors bind to each other and form a dimer

What happens once dimerized T1R receptors activate G-proteins inside the taste receptor cell?

Once dimerized T1R receptors activate G-proteins they depolarize the cell and cause ATP release

How do amino acids, such as glutamate, cause umami taste?

Amino acids cause umami taste when glutamate binds to metabotropic glutamate receptors on taste receptor cells, activating G-proteins on the inside of the cell, depolarizing them and leading to ATP release.

How do chemicals cause bitter taste?

They bind to T2R receptors, there are 2-3 dozen types. These activate G-proteins G-proteins, which depolarizes receptor cells & ATP release.

Describe the gustatory pathway. What makes this pathway unique from othersensory pathways?

Taste receptor cells release ATP onto the nerve endings of neurons with cell bodies in the ganglia of 3 cranial nerves. These neurons project to the nucleus of the solitary tract in the medulla, which projects to the thalamus, which projects to the gustatory cortex in the insula and parietal lobe. This pathway is unique because it is ipsalateral.

How does smell play an important role in flavor?

It plays an important role in flavor because there are more distinct odors than there are distinct flavors.

Where are olfactory receptor cells located?

They are located in the olfactory epithelium.

Describe the relationship between G-proteins activation inside the olfactory receptor cell and the firing of action potentials

Each receptor cells expresses one receptor protein. Olfactory receptor proteins activate G-proteins inside the olfactory receptor cell, producing a generator potential that can cause the cell to fire action potentials.

List glomeruli characteristics and talk about where they receive input from

Glomeruli are areas of synaptic connectivity that contains the axons of olfactory receptor cells and the dendrites of mitral cells, neurons that carry olfactory information elsewhere in the brain. Each glomerulus receives input from olfactory receptor cells expressing one specific olfactory receptor protein.

Does olfactory information pass through the thalamus on the way to the cortex?

No, the olfactory information makes it to the cortex WITHOUT passing through the thalamus.

Which organ detects pheromones? Name two actions pheromones play a role in

The vomeronasal organ detects pheromones. Two actions pheromones play a role in are courtship and signaling of genetic relationships.

How can dogs detect the presence of drugs more efficiently than man-madeDevices?

Dogs have an incredibly sensitive olfactory apparatus and can detect odors at concentrations as low as 2 parts per trillion.

What determines the brightness of light?

The brightness of light is determined by teh amplitude of the wave

What is the trend of wavelength from purple light to red light?

Electromagnetic waves with a wavelength between 400 to 700 nanometers

What are the three primary parts of the eye we covered?

Retina, Cornea, and Lens

What happens when opsins are struck by light?

When opsins are struck by light they activate G-proteins that indirectly close ion channels and cause the neuron to hyperpolarize

If photoreceptors are depolarized, what happens in comparison to when they areHyperpolarized?

When photoreceptors are hyperpolarized the cell releases less glutamate.

How do on-center and off-center bipolar cells function? How do bipolar cellscompare to photoreceptors?

On-center bipolar cells are inhibited (hyperpolarized) by glutamate. Off-center bipolar cells are excited (depolarized) by glutamate. Darkness causes more glutamate, Light causes less glutamate. Bipolar cells do not have action potentials but like photoreceptors release glutamate when depolarized.

What category of retinal cells do rods and cones fall into? explain differences

Rods and cones are photoreceptors. Rods are sensitive to low light, designed for low acuity vision, insensitive to color, and more numerous in the periphery of the retina. Cones require higher levels of light, designed for higher acuity vision, responds to color, and more numerous at the center of the retina

Describe the activity of retinal ganglion cells

Bipolar cells release glutamate onto ganglion cells, ganglion cells are excited by glutamate. They have an on off center arrangement with bipolar cells.

What are the two factors that explain why visual acuity is highest at the fovea?

There are more cones at the fovea and the retina is far thinner at the fovea (allowing light to pass through easier)

What structure do many animals have that allow them to make good use of nightVision?

Tapetum Lucidum is a reflective structure being the retina that gives the rods another chance to detect something

What characteristic of the optic disc makes it the blind spot of the retina?

There are no photoreceptors of any kind and so it is insensitive to light.

Describe light level adaptation. How does the pupil play a role in this?

The pupil can expand or contract to allow more or less light.

Describe the relationship of stimulation and detection between light levels between cones and rods.

Rods and cones are sensitive to different levels of light. The minimal light necessary to stimulate cones is roughly the maximum amount that rods can detect.

How is photoreceptor adaptation related to range fractionation?

Within the broad range of light levels that rods & cones respond to, the cells inside can adjust their level of sensitivity. (if there is a big sudden change in light levels a photoreceptor can adjust its level of light sensitivity to match)

How many cones does the typical human retina have? How does this compare to other species?

A typical human has 3 cones (small, medium, large). Other species have ranges from 4 to 16!

How does color blindness show the importance of opsins?

The light-sensitive opsin molecules expressed in cones are what determines the wavelength of light to which that cone is sensitive. Genes for the M and L cones are located on the X chromosome (defects in these cause red-green colorblindness)

What area makes up the visual field?

The area that is visible to you without adjusting your gaze.

How do retinas receive input in humans? Are both retinas involved?

Retinas receive input from the left and right side of the visual field. Both retinas are involved.

Differentiate between the two retina halves

The left side receives input from the nasal retina on the inside (right) and temporal retina on the outside (left). The right side receives input from the nasal retina on the inside (left) and the temporal retina on the outside (right).

Describe how light from the left visual field would then be transmitted in theRetina

Light from the left visual field is transmitted to the retina through the Left eyes nasal retina and the right eye's temporal retina.

How does the position of the eyes in the head differ between prey animals and Predators?

Prey animals have the eyes on the side of their heads to increase field of vision) and Predators have eyes in the front (to increase depth perception).

What forms the optic nerve?

Axons from the ganglion cells form the optic nerve.

What happens when axons cross at the optic chiasm? What does this processAllow?

When axons cross at the optic chiasm visual info from the left nasal retina and right temporal retina are processed on the tight side of the brain. This allows contralateral processing.

What happens before retinal ganglion cells form synapses on neurons in theLGN?

Retinal ganglion cell axons go from the optic nerve to the optic tract before forming synapses on neurons in the lateral geniculate nucleus (LGN) of the thalamus

What area is important for circadian rhythm? What input allows the brain to syncthe rhythm with light levels?

The suprachiasmatic nucleus of the hypothalamus is important for circadian rhythm. Retinal input allows the brain to sync the rhythm with light levels.

Describe the two principles of cortical processing of visual information

The two principals are Hierarchical model of visual processing (ie moving inward each level of visual system combines inputs from level before) and Fragmented visual processing (distinct regions are specialized for specific aspects of vision).

What is meant by the primary visual cortex (V1) being a map of the visible worldcovered by the two eyes?

A given part of the visual field will always be processed by the same part of V1 and nearby parts of the visual field are processed by nearby parts of V1. in addition, higher acuity regions are represented by a disproportionately large number of neurons in V1.

Compare simple and complex cells

Simple cells respond to light or dark but not both. Complex cells receive inputs from multiple cells and sum their activity.

What can cause agnosia?

Can be caused by destruction of V1 or its inputs

What kind of connections does the primary visual cortex have with thenon-primary visual cortex?

V1 has reciprocal connections with V2.

Describe the split off from V2 that occurs for dorsal and ventral streams

The dorsal split off includes V2 through V5 and is relevant to "where" (visuospatial processing related to control of motion). The ventral portion splits off into V2 through V4 and cares about the "what: (recognition of visual stimuli)

What is the MT primarily concerned with? If damage is incurred, what happens?

V5 or MT is concerned with visual motion. If MT is damaged it will cause motion blindness (akinetopsia) where visual images are not smooth but rather appear as a series of leaping stills (lag).

Elaborate on the role of the posterior parietal lobe

The posterior parietal lobe contains a number of ub regions with neurons that respond to sensory properties of objects. Damage to this lobe can cause hemineglect (patient is unaware of ½ of visual field).

What is the V4 thought to integrate?

V4 integrates information from earlier stages of visual processing such as brightness, color, and shape. Damage causes Achromatopia or a complete lack of color perception.

List and describe the three primary areas in the inferior temporal lobe that aretuned for specific kinds of visual stimuli.

The three primary areas are the 1. Parahippocampal place area (PPA) which responds to scenes consisting of multiple objects ie rooms and landscapes. 2. Fusiform Face area (FFA) which responds preferentially to faces and other similar stimuli. Potentially three is V4 (color shape)