NEW mcq physio

Sensory Nervous System

The part of the nervous system responsible for processing sensory information from the environment.

Microglia

Cells in the central nervous system that act as scavengers, removing debris and pathogens.

Glial cells

Supporting cells in the nervous system that do not produce action potentials.

Synaptic knobs

Structures located at the terminal end of dendrites that release neurotransmitters.

Resting Membrane Potential (RMP)

The electrical potential difference across the neuronal membrane when the neuron is at rest.

Chemical transmitter

A substance released by the presynaptic neuron that transmits signals to the postsynaptic neuron.

Chemical synapses

Synapses that allow the diffusion of chemical substances from the presynaptic neuron to the postsynaptic neuron.

Synaptic cleft

The space between two synapses on the surface of neurons where neurotransmitters diffuse.

Synaptic transmission

The process by which signals are transmitted from the presynaptic neuron to the postsynaptic neuron.

Postsynaptic receptors

Proteins located on the postsynaptic membrane that bind to neurotransmitters and initiate a response.

Metabotropic receptors

Receptors that act by changing the level of intracellular cAMP and are involved in the production of synaptic plasticity.

Excitatory post-synaptic potentials (EPSP)

Changes in the membrane potential of the postsynaptic neuron that make it more likely to generate an action potential.

Inhibitory post-synaptic potentials (IPSP)

Changes in the membrane potential of the postsynaptic neuron that make it less likely to generate an action potential.

Action potential

A rapid change in the membrane potential of a neuron that allows for the transmission of signals.

Voltage-gated channels

Channels in the neuronal membrane that open or close in response to changes in membrane potential.

Ligand-gated channels

Channels in the neuronal membrane that open or close in response to the binding of a specific molecule (ligand).

G-protein coupled receptors

Receptors that activate intracellular signaling pathways through the activation of G-proteins.

Synaptic delay

The time needed for the release of neurotransmitter from synaptic vesicles.

Synaptic fatigue

The inability to release neurotransmitters by exocytosis due to prolonged activity of the synapse.

Post-tetanic potentiation

Increased synaptic strength due to prolonged stimulation of the synapse.

Post-tetanic potentiation

The result of rapid active Ca pump out of the presynaptic neuron.

Long-term potentiation

Characterized by important in long term memory and persistent discharge of postsynaptic neurons in hippocampus.

Ionotropic receptors

Act by increasing permeability to Ca2+ ions.

NMDA receptors

Ligand-gated cation channels.

Habituation

Accompanied by decrease in response of presynaptic neuron inspite of repetitive stimulation of postsynaptic neuron.

Neuropeptides

Interact with ligand-receptors and could produce prolonged changes in the structure of postsynaptic neurons.

Glutamate

The most common excitatory neurotransmitter in the brain.

Neuronal pool

Convergence can lead to amplification of a signal.

Facilitation

Occurs when the two afferent neurons have a common discharge zone.

Occlusion

Results in greater response than if each afferent neuron is stimulated alone.

Lateral inhibition

Helps sharpening of sensation and means that inhibited central neurons are surrounded by excitatory neurons.

Renshaw cell

Shows the phenomenon of negative feedback inhibition and is present in dorsal horn of the spinal cord.

Sensory receptor potentials

Are graded in size, depending on stimulus intensity.

Receptor potential

Amplitude is proportional to the intensity of the stimulus and is due to specific increase of the membrane permeability to Na+ ions.

Specificity in sensory nerves

Depends on the labeled line principle.

Receptors

Detect stimulus intensity

Stimulus modality

Depends on the location of the receptors in the body

Localization of stimuli

Depends on the connections between the receptor and the sensory cortex

Posterior column damage

Impairs kinesthetic sensations, vibration sensation, and the ability to stand steadily with eyes closed

Dorsal column of spinal cord

Carries polymodality of sensations and relays on Gracile and Cuneate nuclei of the opposite side

1st ON cell bodies of dorsal column

Found in the dorsal root ganglia

Impulses carrying pain sensation

Relayed by fibers in the left spinothalamic tract

Destruction of somatic sensory area

Results in inability to identify objects put in the corresponding hand

Main destination of kinesthetic sensations

Post-central gyrus of cerebral cortex

Vibration sense

Detected by Pacinian corpuscles

Fine touch

Detected by slowly adapting touch receptors

Crude touch

More effective in evoking an emotional response due to its central pathway connecting with the limbic system

Two-point tactile discrimination

Indicates a greater threshold distance for feeling of two points of touch

Proprioceptive position sense sensations

Include movement sense and kinesthetic sense

Sensations transmitted in the dorsal column of the spinal cord

Temperature, vibration, and proprioception

Proprioceptive sensations

Transmitted by spinothalamic tracts, gracile tract, and cuneocerebellar tract

Astereognosis

Indicates inability to localize the site of touch on the body surface

Lesion of the dorsal column pathway

Most likely affects fine touch

Lesion of the spinothalamic tract

Results in loss of pain and temperature sensation on the corresponding side of the body

Somatosensory area I

Body representation depends on the relative size of body parts

Axons from VBNT to somatosensory cortex

Pass through the internal capsule

Primary somatosensory cortex

Represents various parts of the contralateral body surface according to the relative size of body parts

Body parts represented superiorly and medially within postcentral gyrus

Face

Body part with the largest representation in the somatosensory area

Lower limb

Action potential recorded during stimulation of thermal receptors

Occurs at zero°C in cold pain fibers, maximal rate of discharge from the cold fibers at 25°C, recorded in warm nerve fibers between 10-35°C, and maximum rate of discharge from the warm pain fibers at 40°C

Thermal sensations

Evoked by stimulation of thermo-sensitive pain receptors

Thermal receptors

Rapidly adapting receptors

Pain receptors

Stimulated by a rise in the local tissue K+ concentration

Pain sensation

Arises from small encapsulated receptors and occurs when the stimulus causes damage of the sensory receptors

Reaction to pain

Includes increased heart rate, withdrawal reflexes, and stoppage of impulse discharge from nociceptors in chronic painful conditions

Pain threshold

Differs markedly among different individuals and is elevated by substance P

Lateral spinothalamic tract

Carries fibers that terminate in the thalamus, contains mainly the second-order neurons, and carries fibers that carry information on temperature and pain

Pain receptors

Receptors in the body that are stimulated by a rise in local tissue K+ concentration and are quick to adapt to a constant stimulus.

GIT

Gastrointestinal tract, the pathway through which food travels in the body.

Nociceptors

Pain receptors that are stimulated by prostaglandins and are more numerous in viscera than other tissues.

Substance P

A substance associated with pain sensation.

Lateral spinothalamic tract

A pathway in the spinal cord that carries fibers which terminate in the thalamus and carries information on temperature and pain.

Fast pain fibers

Pain fibers that conduct at about 5 to 30 m/sec and are responsible for the localization of a pain stimulus.

Slow pain fibers

Pain fibers that conduct at a slower rate and are associated with a dull, aching pain.

Cutaneous pain

Pain that arises from the skin and can be caused by excitation of mechanical or thermal receptors.

Visceral pain

Pain that arises from the organs in the body and is often poorly localized.

Referred pain

Pain that is felt in a different area of the body than where the actual stimulus is occurring.

Enkephalin

A substance that blocks pain transmission by inhibiting the response of the cerebral cortical somatic sensory area to pain signals.

Anterolateral cordotomy

A surgical procedure that interrupts the anterolateral pathway in the spinal cord, resulting in relief of pain.

Serotonin

A neurotransmitter that is released by certain neurons and is involved in pain control.

Syringomyelia

A condition characterized by the dilatation of the central canal in the spinal cord, resulting in dissociated sensory loss.

Posterior column

Damage to the posterior column can impair the ability to stand steadily with the eyes closed.

Somatic sensory area I

Destruction of somatic sensory area I on the left side can result in the inability to identify objects put in the left hand.

Brown-Sequard syndrome

Brown-Sequard syndrome is characterized by loss of voluntary movements on the same side below the level of the lesion.

Right hemisection of the spinal cord

Right hemisection of the spinal cord can result in the loss of fine touch and vibration sense on the left side below the level of the section.

Tabes dorsalis

Tabes dorsalis is accompanied by incoordination of voluntary movements.

Secondary hyperalgesia

Secondary hyperalgesia may be caused by thalamic syndrome.

Convex lens

A convex lens with a focal length of 1cm has a refractive power of 100 diopters.

Eye

The fovea does not lie on the visual axis.

Aqueous humor

Light reflexly activates the parasympathetic nerves supplying smooth muscle in the iris.

Glaucoma

Glaucoma results from increased resistance to fluid outflow through spaces of Fontana.

Lens system of the human eye

The biconvex lens can accommodate for near and far vision.

Cataract

Cataract can occur as a complication of diabetes and prolonged exposure to UVR.

Corneal reflex

Touching the cornea with a piece of cotton causes pupillary constriction of both eyes.

Cornea

The cornea is relatively anhydrated due to the presence of metabolic Na-K pump.

Lens

The lens can increase its curvature and power during near vision.

Near response

Convergence is important to increase depth of focus.

Accommodation for near vision

The ciliary muscles relax, thus releasing tension from the suspensory ligaments.

Refractive power

An increase in refractive power is produced by contraction of the ciliary muscle.

Light reflex

The light reflex involves the Edinger-Westphal nucleus, ciliary ganglion, and oculomotor nerve.