neuroscience quiz 3

sensorimotor system

¡includes those neurons associated with the sensory system as well as the motor system

somatosensory system

¡ is a sensory system for detecting bodily sensations

**Touch**, **Pain**, **Temperature**, and **Proprioception**

¡Somatic sensations include those sensations associated with

mechanical, chemical, temperature, and electromagnetic radiation (as occurs in the visual system)

¡Each of  these sensations is a **modality** of sensation and includes

receptor cells

¡Specialized neurons called **___________** *convert* various **stimuli** into changes in membrane potential that are *transmitted* to the spinal cord and higher brain centers in the form of **action potentials**

sensory transduction

The process of converting sensory stimuli into changes in membrane potentials is called

Pacinian corpuscles

detects vibration and pressure

Meissner’s corpuscles

detects touch

Merkel’s discs

detects light touch

Ruffini corpuscles

detects stretching

nociceptors

detects pain

generator potentials

¡Receptor cells generate **__________** (changes in membrane potentials) that resemble excitatory postsynaptic potentials

sensory transduction

The process of converting sensory stimuli into changes in membrane potentials is called

mechanically-gated sodium channels

¡Activation of a typical receptor cell by such stimuli as stretching, touching, or pressure causes _________ to open, which allows sodium ion influx to produce a graded generator potential

proportional to the strength of the stimulus

Such graded potentials are _________________(that means, their amplitudes are dependent upon the magnitude of the stimulus)

firing rate

¡Stimulus activity within a particular receptive field will lead to changes in that neuron’s ____________

size

¡The ______ of receptive fields vary along the body surface (that is, they vary both size and shape)

dense innervation

¡Receptive fields with ___________ (fingers, lips, toes) are relatively small compared with those in the forearm or back that are less densely innervated

two-point discrimination

**is the ability to perceive two separate stimuli as being separate**

face, lips, fingers, and toes

Two-point discrimination thresholds vary across the body surface: this discrimination is much greater in the _____________ than in the remainder of the body

sensory adaptation

¡is a progressive decrease in the receptor’s response to sustained stimulation

phasic

showing adaptation to stimulus

tonic

showing no adaptation to stimulus

Pacinian corpuscles

large receptive fields, rapidly adapting

Ruffini’s endings

large receptive fields, slowly adapting

Meissner’s corpuscles

small receptive fields, rapidly adapting

Merkel’s discs

small receptive fields, slowly adapting

dorsal roots

Mechanosensory afferents enter the spinal cord via the

ipsilaterally

¡Most of these afferents ascend _______ through the **dorsal columns** (aka the **posterior funiculi**)

**dorsal column neurons**

¡These **first-order neurons**  synapse in the medulla on **____________**

thalamus

¡As is the case for almost all incoming sensory information, this information goes through the ______, on its way to the cerebral cortices

dorsally

¡Sensory information enters the spinal cord _______ via the dorsal roots

dorsal root ganglion

¡Cell bodies of sensory fibers are located in the

ventral roots

¡Motor information exits the spinal cord via

ventral horns

¡Cell bodies of alpha-motor fibers are located in the _______ of the spinal cord

gray matter

¡Synapses occur in the _________ of the spinal cord

distinct part of the thalamus

¡Information concerning each sensory modality is sent to a

postcentral gyrus

¡The primary somatosensory cortex (S1) of each hemisphere is located on the ____________ (this is just posterior of the central sulcus)

large representations

¡Parts of the body that are especially sensitive to touch (for example, the hands and fingers) have __________ in the somatosensory cortices

dermatome

Sensory innervation of the skin and the segmental organization of spinal nerves are related such that, each spinal nerve innervates a particular “segment” of skin called a

somites

Each dorsal root ganglia and its associated spinal nerve arises from embryonic tissue called

**herpes zoster virus**

¡Varicella (chicken pox) is caused by the

dorsal root ganglia

¡Following initial infection, the virus remains in the _____________, where after being dormant for years, can become reactivated, resulting in **shingles**

First order neurons

________ in the sensory system are those sensory axons entering the spinal cord

Dorsal column tracts

___________ synapse in the thalamus

substance P

¡During tissue damage, a variety of substances, including **_______________________________________**, is released

**C-type fibers** (unmyelinated) and **Aδ-type fibers** (myelinated)

¡Most information related to pain is transmitted on **_____________________________________**

anterolateral system

¡Pain information enters the spinal cord dorsally and ascends contralaterally via the **______________** to the thalamus before proceeding to the sensory cortices

cingulate cortex

¡Information related to pain is eventually integrated in the ________________ (recall, the emotional aspect of pain)

the gate theory of pain

(Melzack and Wall) hypothesizes that incoming pain signals can be facilitated or blocked, at least to some degree

The motor cortices

¡__________________ in the frontal lobe are largely responsible for such motor movements

the basal ganglia and the cerebellum

¡These cortices receive input from____________________, which also contribute to motor movements

ventral lateral nucleus

¡The major input to area 6 (primary motor cortex) comes from the **___________________** in the dorsal thalamus, which receives major input from the basal ganglia

caudate and putamen

are the major target of cortical input to the basal ganglia

globus pallidas

the source of output to the thalamus

sensory information (about muscle length) from muscle spindles; upper motor neurons in the motor cortex and brain stem: and interneurons in the spinal cord

3 major sources of input (in the ventral horn) to an alpha motor neuron

ACh binds to nicotinic ACh receptors

Muscle contraction occurs when

motor unit

¡is defined as an alpha motor neuron and all the muscle fibers it innervates

slide past each other

The increase in intracellular calcium causes the thin (actin) filaments and the thick (myosin) filaments to _________________________, shortening the muscle fiber

stretching the muscle

¡causes mechanically gated ion channels to open, triggering an action potential

muscle spindles

¡provide information about muscle length

golgi tendon organs

¡(located between the muscle and the tendon) provide information about muscle tension

apraxia

¡is an impairment in the ability to carry out complex movements in the absence of paresis or plegia: this is often due to problems in central processing of movement sequences

receptor sends AP

Step 1 of the sensory pathway

Dorsal root of spinal cord

Step 2 of the sensory pathway

Medulla

Step 3 of the sensory pathway

Medial lemniscus

Step 4 of the sensory pathway

Thalamus

Step 5 of the sensory pathway

Primary somatosensory cortex

Step 6 of the sensory pathway

A delta fibers/C fibers

Step 1 of the pain pathway

Dorsal horn of spinal cord

Step 2 of the pain pathway

Anterolateral system

Step 3 of the pain pathway

Brainstem

Step 4 of the pain pathway

PAG

Step 5 of the pain pathway

Thalamus

Step 6 of the pain pathway

Primary somatosensory cortex and cingulate cortex

Step 7 of the pain pathway

Info from other cortices to primary motor cortex to brainstem

voluntary motor pathway

Motor command

Step 1 of muscle contraction pathway from CNS to PMS

Ventral roots of spinal cord

Step 2 of muscle contraction pathway from CNS to PMS 

Neuromuscular junction

Step 3 of muscle contraction pathway from CNS to PMS 

Muscle contracts

Step 4 of muscle contraction pathway from CNS to PMS 

Depolarization on the sarcolemma to AP into T tubules to into the sarcoplasm

Excitation phase of muscle contraction

Ca2+ ok troponin to myosin binding site exposed to myosin head binds to actin (ADP released)

Contraction phase of muscle contraction

Myosin head binds to ATP and detaches to ATPase hydrolyzes new ATPs

Relaxation phase of muscle contraction

Supplementary motor cortex

Cortex responsible for initiation of movements

Premotor Cortex

Cortex responsible for motor sequences

No

Is there ATP during the contraction phase

conduction deafness

ossicles; fail to convert sound waves into mechanical waves

sensorineural deafness

Hair cells; inability to create AP in cochlea

central deafness

auditory regions of the brain; inability to process and transmit auditory signals

Ipsilaterally and contralaterally

Fibers of the ASL ascend ___________ upon entering the spinal cord

rods

¡(about 90 million) have low spatial resolution, but are very sensitive to *light:* these receptors allow us to see in the dark

All contain the same type of photopigment

cones

¡(about 4.5 million) have high spatial resolution, but somewhat insensitive to light these receptors are responsible for ourability to see color

¡There are three types, each containing a different pigment

photoreceptors, outer synaptic layer, bipolar cell layer, inner synaptic layer, ganglion cell layer

the neural layers of the eye

Nerve impulses

move in the opposite direction from that of light rays

photoreceptor cells

(rods and cones) convert light energy into changes in membrane potentials

bipolar cells

¡(horizontal and amacrine cells ) are involved with modifying such inputs as they are relayed to the ganglion cells

ganglion cells

¡generate action potentials in response to changes in membrane potentials

magnitude of the input

¡The rate or frequency of AP generation by ganglion cells is dependent upon the ______________________________________

emmetropia

¡Normal vision occurs when lights rays fall directly onto the back of the retina; this is known as **_________**