APK4144 Exam 1

Compare the 4 types of mechanoreceptors.

Merkel cells: static/slow, epidermis, high spatial resolution, fingertips and lips, sensitive to light pressure, processes info about shape and texture, cutaneous receptor Meissner's Corpuscle: dynamic/rapid; dermis, grip control, vibrations, sensory info in hands Ruffini: static/slow, dermis, cutaneous, vibrations transmitted through objects grasped in hand Pacinian: Dynamic/rapid, hypodermis, largest receptive field, cutaneous, sensitive to stretching of fingers and hands

Suppose you are recording APs from a neuron. How will the AP be affected if you remove Na+ or K+ from the external medium?

Na+: AP will not occur K+: AP will be more difficult to occur because cell will be even more negative

Glial cells are at least as numerous is the brain as neurons, yet neurons are the predominant focus of neuroscience textbooks. Why?

Neurons actually transmit signals around the body and glial cells cells just aid in transmitting signals

After entering the spinal cord, which of the following is true regarding nociceptors and mechanoreceptors coming from the hands via the dorsal root ganglia?

Nociceptors cross the midline in the spinal cord and mechanoreceptors cross in the medulla

Ganglion cell axons cross at the _______, thus the _____ contains info from both eyes

Optic chiasm; optic tract

Thomas is having trouble with discriminative touch and it is determined that his rapidly adapting, large receptive field mechanoreceptors are dysfunctional. Which mechanoreceptors is he having trouble with?

Pacinian corpuscles

Describe the 5 types of retinal neurons.

Photoreceptors: rods and cones (outer nuclear layer) Bipolar cells: connected to ganglion and amacrine cells Ganglion cells: sends images to brain Amacrine cells: interneurons; makes connections between ganglion and bipolar cells Horizontal cells: laterally connecting; cell bodies in inner nuclear layer; surround antagonism; provide inhibitory feedback

How does membrane permeability to K+ and Na+ change during an AP?

Pk exceeds Pna at rest; Pna temporarily increases during the AP

What is proprioception? Name 2 kinds of proprioceptors, their function, and their afferent group innervation.

Proprioception: perception or awareness of the position or movement of your body Muscle spindles: act (like a string) when muscle stretches - 1a afferent fibers attach to capsular part and rapidly adapt - group II fibers slowly adapt Golgi tendon organs: receptors found at tendons; related to muscle tension - alpha motor neurons

Is the world mapped upside down on the retina? On V1? If the right visual cortex stops functioning, what part of the visual field will be lost.

Retina: upside down and RL revered V1: upside down and upper part is below calcarine sulcus and lower part is above calcarine sulcus - if R visual cortex stops functioning the L visual field will be lost

The _______ is inversely proportional to the density of the fibers supplying an area.

Size of the receptive field

Markel receptors, which are in the epidermal layer, have small receptive fields and are slowly adapting or rapidly adapting?

Slowly

Which experimental evidence supports the claim that Ca2+ is sufficient and/or necessary?

Sufficient: inject presynaptic terminal with Ca2+ and membrane potential increases because more neurotransmitters are released Necessary: if you block Ca2+ in presynaptic terminal no post synaptic potential occurs

In the sequence of events in post-synaptic signaling, which event occurs just after the "post-synaptic cells excited or inhibited"?

Summation determines whether or not an AP occurs

Describe the laminar organization of primary visual (striate) cortex (V1).

The LGN is a nucleus in the thalamus that sends info to the primary visual cortex (V1) which is located in the posterior occipital cortex. There are 6 layers. All inputs go to layer 4, ascending output to the extrastriate cortex come from layers 2 and 3, descending outputs to the superior colliculus are from layer 5 and outputs to the LGN are from layer 6.

Which statement correctly differentiates between the passive and active current in a myelinated axon?

The active current flows only in the nodes of ranvier, unlike the passive current

Compare the neural pathways for touch and proprioception for upper and lower body.

Upper: Cuneate nucleus and cervical spinal cord Lower: gracile nucleus and lumbar spinal cord

The axon of the medial lemniscus synapses with neurons of the...

Ventral posterior nucleus of the thalamus

Compare the function of the ventral and dorsal visual pathways. What are the functions of MT and V4?

Ventral: identify objects and process details in stimulus features Dorsal: movement and location of stimulo MT: neurons detect speed and direction so if damaged cannot detect these things (cerebral akinetopsia) V4: colors and shapes so if damaged cannot see colors (cerebral achromotopsia)

Describe the 2 main neural pathways in myotatic spinal reflex that innervate the flexor and extensor muscles.

When a muscle is stretched, its muscle spindle is stretched and nerve activity increases - alpha motor neuron activity increases - causes fibers to contract and resist stretching - gamma motor neurons regulate how sensitive the stretch reflex is - 1a afferent neuron goes to spinal cord to tell muscle to contract - efferent neurons make correct muscles contract contraction of other muscles - interneuron = inhibitory

Explain the steps in phototransduction of a rod.

When light is present cGMP increases and opens ion channels. NA+ and Ca2+ flow into the cell and K+ leaves. When it is dark cell makes K+ leave rapidly and cell becomes hyperpolarized.

The most important factor determining whether a receptor-operated channel is inhibitory or excitatory is...

Whether the permeant ion's reversal potential is positive or negative to threshold

The amplitude of an AP of a given neuron is...

always the same

The resting potential of a cell is given because...

at rest there is an excess of K+ inside the cell and the membrane is permeable chiefly to K+

The cornea and lens allow light to enter the eye. Many times the transparency of the lens can break down, and cause the following eye abnormality.

cataracts

The eye has both internal and external muscles. The _____ muscles are the internal muscles that control the shape of the lens.

ciliary

Which structure can be found exclusively at an electrical synapse (gap junctions)?

connexons

What is the magnitude of a typical neurons resting membrane potential? Why do neurons and their cells have a negative resting membrane potential?

- typical is about -70mv - negative because there is more Na+ outside the cell than K+ inside the cell

What are the main components of a neuron?

dendrites, axon, axon terminal, and soma

An AP occurs if current injected into a neuron ______ the neuron to reach _____ potential

depolarizes; threshold

An AP occurs if current injected into a neuron ______ the neuron to reach ______ potential

depolarizes; threshold

Presynaptic and postsynaptic neurons that form _____ synapses are connected via _______

electrical; gap junctions

superior colliculus (ganglion cells)

eye movements

Compare spatial and temporal resolution of fMRI to those of EEG. Why if fMRI so popular in human neuroscience studies?

fMRI: high spacial resolution and low temporal resolution - popular because it shows areas of high activity and functional connectivity across multiple brain regions EEG: excellent temporal resolution and not so great spacial resolution

A dermatome is an area innervated by...

fibers from one spinal cord segment

In relation to other retinal ganglion cells, a P ganglion cell has...

finer spatial resolution and etter color sensitivity

Which of the following is not a feature of the muscle spindle based proprioceptive system?

in-parallel attachment to tendons

In the sequence of events in neurotransmission, which even occurs just after the AP arrives at the presynaptic terminal?

influx of Ca2+ into presynaptic terminal

Rode have a refractory period that is ______ is comparison to cones.

longer

The resting membrane potential of a neural cell is..

mainly determined by K+ channels

Central projections of retinal ganglion cells

optic nerve, optic tract, optic chiasm, LGN, optic radiation, hypothalamus, pretectum, and superior colliculus

Sub-threshold current injected into an axon flows ____ (actively/passively) along the axon and _____ (decays/stays the same) with distance from the site of injection.

passively; decays

Which structures contribute to the sensory-discriminative aspect of pain?

primary somatosensory cortex and ventral posterior lateral/medial nucleus of thalamus

The mechanism that accounts for light induced hyperpolarization of photoreceptors is...

rapid fall in cGMP cone, leads to closure of Na+ and Ca2+ channels

pretectum (ganglion cells)

reflex control of pupil and lens

An AP travels in only one direction along the axon because of its ______ property

refractory

Hypothalamus (ganglion cells)

regulates circadian rhythm

There are 3 layers of tissue that form the anatomy of the eye. The ______ is the part of the eye that has light sensitive neurons that transmit visual signals to the optic nerve.

retina

If the ________ for post-synaptic potentials is more positive than the _____, the effector of a transmitter is excitatory, and generates EPSPs.

reversal potential; AP threshold

Which region is not a target of retinal ganglion cell axons?

striate cortex

Which statement best describes the relationship between receptive fields, density of mechanoreceptors, and 2 point discrimination?

the smaller the receptive field, the higher density of mechanoreceptors, the smaller the 2 point discrimination

On which body part would the 2-point discrimination threshold e the shortest?

thumb

True or false -- when a cone is hyperpolarized, the on-center bipolar cells depolarize and the on-center ganglion cells increase their firing rate?

true

List the sequence of events involved in transmission at a typical chemical synapse.

1. AP influx of Ca2+ 2. vesicles fuse with presynaptic membrane 3. Neurotransmitters released into presynaptic terminal 4. bind to receptor molecules 5. open ligand gated channels

List the sequence of main steps involved in postsynaptic signaling.

1. neurotransmitter released 2. receptor binding 3. ion channels open/close 4. conductance change causes current flow 5. postsynaptic potential changes 6. postsynaptic cells excited/inhibited 7. summation determines whether or not an AP occurs

Are there functional differences between the 4 Brodmann's areas?

3b and 1: cutaneous 3a: proprioception 2: both

Brodmanns' areas _____ and _____ primarily respond to tactile stimuli, while area ______ primarily responds to proprioceptive stimuli, and area ______ process both tactile and proprioceptive stimuli.

3b and 1; 3a; 2

Axons from the lGN terminate in which layers on the primary visual cortex?

4A and 4C

Explain the differences between APs and synaptic potentials. How is stimulus strength encoded by synaptic or action potentials?

AP: all or none; always depolarize; need to be a certain strength to occur; strength = frequency of AP Synaptic: graded; changes in potential that vary in size; can be hyper or depol; magnitude of response is proportional to strength of stimulus

A spinal motor neuron generates an AP when the membrane potential reaches a threshold voltage level. The somatosensory receptors generate a different kind of potential called a receptor potential. Which of the following statements best characterizes these two types of potentials?

APs have frequency encoding and receptor potential amplitude can be graded by the intensity of the stimulus

Compare and contrast EPSPs and IPSPs.

EPSP: increase the likelihood of a postsynaptic AP occurring; depolarizing IPSP: decrease the likelihood of postsynaptic AP occurring; temporary hyperpolarizing of postsynaptic membrane

Neurons in the visual cortex respond to which type of stimulus?

Bars or edges in a particular orientation

A man is brought to the emergency room after a car crash. A doctor shines a light in his right eye and only the right pupil constricts. Which of the following regions is most likely damaged?

Edinger-Westphal Nucleus

True or false -- the knee jerk reflex contains afferent feedback from stretch receptors that enter the ventral horn of the spinal cord?

False

true or false -- Receptive fields of all nociceptors are rapidly adapting to painful stimuli?

False

true or false -- The nociceptors carry painful info in highly myelinated axons that respond quickly to painful stimuli?

False

Which feature of an electrical synapse allows synchronizing the electrical activity of multiple neurons?

Fast speed of transmission and bidirectional transmission of electrical signals

Which structures are included in the CNS and which are part of the PNS?

CNS: brain and spinal cord PNS: nerves

Compare and contrast electrical and chemical synapses.

Chemical: gap between 2 neurons where info passes chemically using a neurotransmitter; allows a single post-synaptic cell to amplify, modify, and compute excitatory or inhibitory signals received from multiple presynaptic neurons Electrical: gap with channel proteins connecting 2 neurons so signal can travel straight over synapse; transmission is faster because it is passive and bidirectional

On its way to the retina, light passes through tissues and fluids in what order?

Cornea, aqueous humor, lens, vitreous humor, retina

At which point during signal transmission at a chemical synapse is exocytosis ocuring?

During neurotransmitter release into the synaptic cleft

Nodes of ranvier represrn what?

Gaps in myelin wrapping

Compare the gate theory of pain with the descending modulation of pain.

Gate theory: perception of pain is modified by sub-threshold mechanoreceptors in the spinal cord Descending modulation of pain: brain basically decides whether or not it is a good time to feel pain

What are the three main glial cell types in the CNS?

Astrocytes, oligodendrocytes, and microglial cells

What are the main types of glial cells, and what is the main function of each?

Astrocytes: blood brain carrier (CNS) Microglial cells: inflammatory response (CNS) Oligodendrocytes: myelin (CNS) Schwann cells: myelin (PNS)

Where would voltage gated Ca2+ channels be most abundant?

Axon terminal

The somatic system has three major subsystems 1) mechanical stimuli 2) proprioceptive stimuli and 3) painful and temperature related stimuli. Is it true or false that these three subsystems travel down the same type of axonal fiber in the peripheral nervous systems?

False

True or False -- There is a higher concentration of potassium outside the cell than inside the cell?

False

True or False -- passive potentials maintain the same amplitude as they travel along an axon?

False

Compare the cause and clinical symptoms of glaucoma, retinitis pigmentosa, and macular degeneration.

Glaucoma: hereditary eye disorder from too much pressure from a buildup of aqueous fluid causes damage to the optic nerve Retinitis pigmentosa: hereditary eye disorder caused by degeneration of photoreceptors. starts with loss of rods and then cones. Macular degeneration: hereditary eye disorder caused by degeneration of photoreceptors. Two types: wet and dry. Dry is much more common but does not have treatments but wet does.

Which cell type is thought to be responsible for surround antagonism of ganglion cells?

Horizontal

Hyperpolarization of an OFF-center bipolar cell would indicate...

Hyperpolarization of the center cone and a bright center display

A photoreceptor cell is exposed to a flash of light. Ho does the membrane potential of this cell and its corresponding ON-center bipolar and ganglion cells change?

Hyperpolarized, depolarized, depolarized

Which type of somatosensory afferents transit info from the muscle spindles to the CNS?

Ia and II

Where would the primary afferent axons conveying mechanosensory signals from the right arm be found?

In the right cuneate tract of the cervical spinal cord

Compare the benefits and limitations of extracellular versus intracellular electrophysiological recordings.

Intra: measures true membrane potentials at all times; low spatial resolution but shows single cells very accurately Extra: high spatial resolution but cannot see single cells

What are the 2 broad families of receptor proteins?

Ionotropic and metabotropic receptors

What is the action of the neurotransmitter at a chemical synapse?

It acts of receptors in the post synaptic membrane

Which statement about electrochemical equilibrium is true?

It occurs when the potential across the membrane exactly offsets the concentration gradient

Suppose you are recording a neurons resting membrane potential. If you add KCl to the external medium what will happen to the resting membrane potential? What if you add NaCl to the external medium?

KCl: resting potential will get more positive because K+ will rush into cell NaCl: nothing will happen because Na+ channels are closed at rest

Are binocular neurons found in the lateral geniculate nucleus? Are they found in layer 4 of the primary visual cortex? Where does input from both eyes first converge?

LGN: monocular only Layer 4: monocular only because info comes from LGN Both eyes first converge at the optic tract

The right gracile nucleus projects to the...

Left thalamus

Compare the magnocellular and parvocellular streams.

Magno: large receptive field, layers 1 and 2, responds transiently to visual stimulus, large bodies and extensive dendritic field Parvo: small receptive field, layers 3/6, high spatial resolution, responds in a sustained fashion, transmits info about color

What is an important difference between the Meissner and Pacinian receptor?

Meissner has a small receptive field and Pacinian has a large receptive field

Which afferents have the highest spatial resolution

Merkel cells

While in the library studying, you observe another student reading a braille textbook. Which mechanoreceptor is responsible for registering the sharpest perception of the braille type?

Merkel cells

Which statement about active ion transporters is true?

They move certain ions against the concentration gradient

MEPPS are produced by a spontaneous release of neurotransmitters, true or false?

True

True or false -- extracellular recordings occur outside the cell to measure the rate of AP firings?

True

Which part of the thalamus does the upper body somatosensory information innervate?

ventral posterior lateral nucleus of the thalamus