CH 15 Overview of sensory and motor pathways

What are sensory receptors?

Specialized cells that monitor specific conditions in the body or environment

Where does somatic sensory information get distributed?

Primary somatosensory cortex of the cerebrum

Where does visceral sensory information distribution?

Reflex centers in the brain stem and diencephalon

Voluntary or involuntary somatic motor commands control which peripheral effector?

skeletal muscles

What is sensation?

Information from sensory receptors on what's going on outside

What is perception

Conscious awareness of sensation

Transduction

Conversion of stimulus to an action potential that can be propagated to the CNS

Receptor specificity

Characteristic sensitivity to certain stimuli

Which receptor has the least receptor specificity

Nerve endings

What is receptive field

Area monitored by a single receptor cell

What is the relationship between receptor field size and localization?

Larger the field the poorer the ability to localize 

What is a labeled line

The link between a peripheral receptor and a cortical neuron

What are tonic receptors?

Receptors that are always active

Whata are Phasic receptors?

Usually not active

Define adaptation

Decreased sensitivity to a constant stimulus

What are tonic receptors adaptation speed?

Slow adapting

What are phasic receptors adaptation speed?

Fast adapting

Phasic receptor example

Jumping into a pool and feeling cold

Tonic receptor example

Burning your finger and feeling pain for the entire day

Exteroceptors

Monitor external environment

Proprioceptors

Monitor position and movement of skeletal muscles

Interoceptors

Monitor visceral organ function

What general stimulus do nociceptors detect? What does the size of their receptive field indicate?

Pain, Large fields make pinpointing pain difficult

Type A and Type C fibers difference

Type A is myelinated and carries fast pain; Type C is unmyelinated and carries slow pain

Phantom limb syndrome

Pain felt in an amputated limb due to hyperexcitable interneurons

Thermoreceptors structure and adaptation type?

Free nerve endings in the dermis, phasic

What are mechanoreceptors sensitive to?

physical stimuli like stretching, compressions, twisting

3 classes of mechanoreceptors

Tactile, baroreceptors, proprioceptors

Which tactile receptor is the only sensory receptor on the cornea of the eye?

Free nerve endings

Which tactile receptors are most abundant in the eyelids, lips, fingers, nipples, and external genitalia?

Tactile corpuscles (Meissner)

Baroreceptors function

Monitor blood pressure in carotid and aortic sinuses

Receptors involved in defecation and urination reflexes

Baroreceptors

Major groups of proprioceptors

Muscle spindles, golgi tendon organs, receptors in joint capsules

What are chemoreceptors and what do they detect?

Specialized nerve cells that detect changes in chemical concentration 

Describe the function of a first-order neuron

Delivers sensation directly to CNS from spinal/cranial ganglion.

What is a second-order neuron

Interneuron located in spinal cord or brainstem.

Where would you find a third-order neuron

thalamus

Decussation

When a second-order neuron crosses over to the opposite side of the CNS.

Due to the decussation of second-order neurons, the right side of the thalamus receives information from which side of the body?

left

List the 3 main somatic sensory pathways

Spinothalamic, posterior column, spinocerebellar

Which pathway is associated w phantom limb pain

spinothalamic pathway

What is referred pain? Which sensory pathway is associated with? What is a familiar example of this that the book states?

Feeling pain in an uninjured part of the body that originates from somewhere else. This associated w spinothalamic, heart attack 

Which tracts in the spinothalamic pathway carry sensations of crude touch and pressure sensations?

lateral : pain + temp

anterior: crude touch + pressure

What sensations are carried by the posterior column pathway?

Carries highly localized fine touch, pressure, vibration, and proprioception(body position)

What 2 spinal tracts are in the posterior column pathway

Gracile fasciculus

Cuneate fasciculus

What is the sensory homunculus

Functional map of the primary somatosensory cortex

What information is conveyed by the spinocerebellar pathway?

Muscle, tendon, and joint positions from the spine to the cerebellum 

Which tracts of the spinocerebellar pathway contain axons that do not cross over to the opposite side of the spinal cord?

Posterior spinocerebellar

Which tracts of the spinocerebellar pathway are dominated by axons that have crossed over to the opposite side of the spinal cord.

anteiror spinocerebellar

Where is visceral sensory information primarily collected from? (ie: which body cavities)

Thoracic and abdominopelvic cavities

Which nuclei function as major processing and sorting centers for visceral sensory information?

Solitary nuclei

Somatic motor pathways always involve at least two motor neurons. What are they called?

Upper motor neurons and lower motor neurons

Conscious and subconscious motor commands control skeletal muscles by traveling over three integrated motor pathways. Name the motor pathways.

Corticospinal, medial, and lateral

Which motor pathway carries motor command that provides voluntary control over skeletal muscles?

corticospinal

name the three pairs of descending tracts of the corticospinal pathway

Corticobulbar, lateral corticospinal, anterior corticospinal

What is the motor homunculus

Map of corresponding parts of the motor cortex.

What do larger areas of the homunculus represent?

more precise control.

Which motor pathway is associated with the control of muscle tone and gross movements of the neck, trunk, and proximal limb muscles?

Medial

Name four tracts that are part of the medial motor pathway.

Medial/lateral reticulospinal, Tectospinal, vestibulospinal 

Which motor pathway is associated with the control of muscle tone and more precise movements of the distal parts of the limbs?

Lateral

The rubrospinal tract is part of which motor pathway?

lateral motor pathway.

Basal nuclei location

Located in the cerebrum.

What part of the brain contains the basal nuclei? What information do the basal nuclei provide?

Cerebrum, background patterns of movement for voluntary activity

What is the function of the cerebellum?

Monitor proprioceptive sensations, visual info, and vestibular(balance). Essential for precise movement