As it relates to sensory systems, what is adaptation?

Adaptation is the process by which sensory systems filter stimuli to concentrate on novel stimuli

How is the intensity of a stimulus determined?

Action potential frequency

Each sensory system in the brain has what?

Sub-cortical and cortical structures devoted to that sensory function

What three components affect bodily awareness in space?

Pressure from the body surface, vibration of the skin and deflection of hair on the body surface

What are nociceptors?

Nociceptors are free nerve endings of small, myelinated and unmyelinated fibers that transport information regarding noxious stimuli to the CNS

What happens to nociceptors when tissue damage occurs?

Tissue damage depolarizes nociceptors directly

What are mechanoreceptors?

Mechanoreceptors are other sensory neurons which change physical energy in the form of pressure, stretch or vibration into neural energy (transduction)

Mechanoreceptors serve what function in terms of the neural network?

They accomplish trasduction for the nerve endings (ex. stretch organs for propriorreception)

Primary sensory neurons located in the DRG have specialized what?

Neurites. these neurites conduct action potentials and project to the periphery

What is "generator potential"?

It's the process by which neurites transduce physical energy into neural energy by directly depolarizing the most peripheral patch of the membrane

How are generator potentials graded?

They are graded in amplitude according to the strength of the stimulus

The amplitude of generator potentials is then converted to what?

Action potential frequency

In regards to a continuous stimulus, action potentials are what?

Self-terminating; they do not exist for the duration of the stimulus

Axons bearing the action potentials from somatosensory neurons in the DRG synapse where?

In the brainstem. These are second-order neurons that then project into the cortex

Where do central projections of the somatosensory system end up?

Information ends up in the postcentral gyrus of the parietal lobe as the *primary sensory homunculus*

What is a somatotopic map?

It's a neural representation of the body surface

What is so important about a topographically faithful somatotopic map?

Geometric body relationships are preserved

In regards to the homunculus, what does the size of body structures reflect?

It reflects the disproportional sensitivity of some body parts

Cortical areas receiving sensory information from the body lie where with regards to the cortical regions which activate motor output of the body?

Directly across

What is the pinna?

The pinna is a part of the outer ear which comprises the flaps of skin and cartilage that focus sound waves

What is the eardrum (tympanic membrane)?

It is the part of the outer ear which separates the outer and middle ear components

In the middle ear, vibrations cause compression of the tympanic membrane which moves the first of three tiny bones, the (blank)

Malleus (mallet)

In the middle ear, the malleus hammers into the (blank) which vibrates the (blank)

Incus (anvil); stapes (stirrup)

The vibrations from the middle ear does what?

The vibrations deform a membrane called the oval window which separates the air-filled middle ear from the fluid-filled inner ear

What comprises the inner ear?

The cochlea and the vestibular apparatus

What causes movement of fluid and structures in the cochlea?

Deformation of the oval window

What is the scala media?

It is a fluid-filled chamber in the middle of the cochlea (it's also called the cochlea duct)

What is the basilar membrane?

It's the resonany structure within the cochlear duct that houses neurons that transduce sound energy into neural energy

What happens when the basilar membrane becomes deformed by the fluid wave?

The shearing force bends stereocilia (or hair cells) which either activates or inhibits the associated neurite

What happens when stereocilia bend in their normal direction (and Ca++ fluxes into the neurite)?

Depolarization of the nerve fiber

What happens when stereocilia bend the opposite way that they normally bend (and K+ fluxes out of the neurite)?

Hyperpolarization of the nerve fiber

What two inner ear structures are primarily used to determine body position with respect to gravity?

The utricle and the saccule

In the chambers of the inner ear, how are stereocilia bent?

They are bent by action of calcium carbonate crystals (otoliths) in the matrix

Head movement in any direction starts what action in the inner ear?

A generator potential in stereocilia

The frontal lobes are associated primarily with what?

Motor function

The parietal lobes are primarily associated with what?

Sensory function

Where is the precentral gyrus located?

It's located from the first fold rostral to the central sulcus

What does the precentral hyrus contain?

It contains pyramidal motor neurons in a highly conserved order in a map analogous to the somatotopic map of the postcentral gyrus (oriented simiarly to the somatosensory homunculus)

As axons from neurons in the motor cortex pass caudally in the spinal cord toward the lower motor neuron pools, where do they insert and with what do they synapse?

They insert into the ventral horn of the spinal cord and synapse with lower motor neurons

What happens along the spinal cord as the motor cortex is stimulated?

Axon collaterals innervating the lower motor neurons in the ventral horn of the spinal cord are activated at several levels of the spinal cord; this produces localized movements involving several muscles and joints

What is interesting to note about direct control of individual neurons in the primary motor cortex and their control over body parts?

Only lower motor neurons controlling the digits of the hand are under this direct control

How many giant pyramidal cells are located in primary motor cortex?

About 30,000

What is the basal ganglia (general overview)?

The basal ganglia is a midbrain structure which exerts a diffuse and coordinating influence over the output of neurons in the primary motor cortex (pyramidal motor system)

What three parts is the basal ganglia primarily made out of?

It is made out of the caudate, putamen, striatum and globus pallidus

The basal ganglia is prone to a number of diseases. What symptoms are always encountered in these affections?

Inhibition of voluntary movements and initiation of motor mvoements (this indicates the basal ganglia's role in volitional aspects of motor performance)

Why is the basal ganglia often the location of strokes?

It contains arterioles (fine arteries) and venules (fine veins)

What are some of the consequences of stroke?

Loss of blood flow (ischemia), hypoxia (inadequate oxygen supply), anoxia (absence of oxygen) and infarct (tissue damage)

What does stroke cause?

It causes cell death which results in hemiplegia; there will likely be partial paralysis on the contralateral side of the body as well as a loss of sensory function such as numbness or paresthesias

What is Parkinson's Disease?

It's a deficit in striatal dopamine levels secreted by substania nigra (black substance) neurons

What is Parkinson's Disease characterized by?

An inability to initiate movement (akinesia) and a "pill rolling" tremor

What is L-dopa in regards to Parkinson's Disease?

It's an effective treatment which loses effectiveness as the disease progresses

Is transplanting dopaminergic tissue commonly used to treat Parkinson's Disease?

No; it is controversial (it has efficacy and tissue donor issues)

What is Huntington's Disease?

It's a deficit in striatal cells which secrete acetylcholine and GABA

What are the symptoms of Huntington's Disease?

Excess of undesired movements and lack of muscle tone

What are the movements caused by Huntington's Disease called?

They are sudden and are called choreas; they are called hemiballismus if they are violent

Where is the cerebellum located?

It's located in the hindbrain; it is dorsal to the pons and 4th ventricle

What does the cerebellum do?

It exerts a precise and coordinated but limited influence over the activity of the extrapyramidal system, especially with respect to motor execution

What is the vestibulocerebellum?

It's the oldest part of the cerebellum and is most caudally in the flocculonodular lobe; it's mostly used for balance and eye movements

What is the spinocerebellum?

It makes up the bulk of the human cerebellum and is mostly involved in motor execution

What is the corticocerebellum?

It's the part of the cerebellum that surrounds the spinocerebellum laterally and dorsally; it controls motor planning

What function does GABA serve in neuronal signaling?

It is the likely mediator of most inhibitory synapses in the brain

What do GABA antagonists produce?

They produce seizures

What is a focal epilepsy?

A focal epilepsy is a seizure in only one part of the body and results from unbounded excitation in a restricted brain region

What are benzodiazapines?

They are drugs that enhance GABA binding to receptors and are effective treatments for epilepsy