CH. 17 Pathways and Integrative Functions

Question 1

What are the two types of nervous system pathways?

Answer 1

1. Sensory pathways (ascending pathways): the sensory information gathered by sensory receptors ascends through the spinal cord to teh brain
2. Motor pathways (descending pathways) transmit motor information that descends from the brain through the spinal cord to muscles or glands

Question 2

What are the common characterisitcs of nervous system pathways?

Answer 2

1. Common location of neuron components: neuron cell bodies are located in one of three general places: ganglia within the peripheral nervous syste,. gray horns within the spinal cord, or nuclei within the brain along the pathway.
2. Paired tracts: all pathways are composed of paired tracts. because each tract innervates structures on only one side of the body, both left and right tracts are needed to innervate both the left and right sides of the body
3. Two or more neurons: most pathways are composed of a series of two or three neurons that work together
4. Decussation of pathways: most pathways decussate (to cross over) from one side of the body to the other side at some point along their length; left side processes info from the right side and vice versa
5. Somatotopy: in most pathways, there is a precise correspondence of receptors in body regions, through axons, to specific functional areas in the cerebral cortex - this is called samatotopy

Question 3

What is the difference between somatosensory pathways and viscerosensory pathways?

Answer 3

somatosensory pathways prcoess stimuli received from receptors within the skin, muscles, and joints, whereas viscerosensory pathways process stimuli received from the viscera

Question 4

What are the three types of body sensations that are grouped into spinal cord pathways of the somatosensory system?

Answer 4

1. Discriminative tough: describe textures and shapes of unseen objects
2. Temperature and pain: allow us to detect those sensations
3. Proprioception: allow us to detect the position of joints, amount of stretch in muscles, and tension in tendons

Question 5

Describe the series of neurons that are used to transmit stimulus information from the body periphery to the brain.

Answer 5

1. Primary neuron: dendrites of this sensory neuron are part of the receptor that detects a specific stimulus. cell bodies of primary neurons reside in the posterior root ganglia of spinal nerves or the sensory ganglia of cranial nerves
2. Secondary neuron: an interneuron of which has a cell body that resides within either the posterior horn of the spinal cord or a brainstem nucleus. axon projects either to the thalamus for conscious sensations or to the cerebellum for unconscious prorioception
3. Tertiary neuron: interneuron whose cell body resides with the thalamus. thalamus is the central processing and coding center for almost all sensory information

Question 6

Explain the three major types of somatosensory pathways that have specific tracts that extends through the spinal cord.

Answer 6

1. Posterior funiculus - medial lemniscal pathway: projects through the spinal cord, brainstem, and diencephalon before terminating with the cerebral cortex; derives from two components - tracts within the spinal cord, collectively called the posterior funiculus, and the tracts within the brainstem, collectively called the medial lemniscus. this pathway conducts sensory stimuli concerned with proprioceptive infromation about limb position and discriminative touch
2. Anterolateral pathway - located in anterior and lateral white funiculi of the spinal cord; composed of anterior spinothalamic tract and lateral spinothalamic tract. axons projecting from primary neurons enter the spinal cord and synapse on secondary neurons within the posterior horns. - axons entering these pathways conduct stimuli related to crude touch and pressure as well as pain and temperature
3. Spinocerebellar pathway: copnducts proprioceptive information to the cerebellum for processing to coordinate body movements. composed of anterior and posterior spinocerebellar tracts; these are major routes for transmitting postural input to the cerebellum. - sensory input arriving at the cerebellum through these tractrs is critcial for regulating posture and balance for coordinating skilled movements =; also only have primary and secondary neurons

Question 7

Where is the cell body of the upper motor neuron housed within?

Answer 7

either the cerebral cortex or a nucleus within the brainstem; axons of the upper motor neuron synapse either directly on lower motor neurons or on interneurons that synapse directly on lower motor neurons.

Question 8

Where is the cell body of the lower motor neuron housed within?

Answer 8

either within the anterior horn of the spinal cord or within a brainstem cranial nerve nucleus; axons of the lower motor neurons exit the CNS and project to the skeletal muscle to be innervated

Question 9

Differentiate between the left and right hempispheres in hemispheric lateralization.

Answer 9

the left hemisphere is the categorical hemisphere: contains the wenicke area and motor speech area specialized for language abilities, and is also important in performing sequential and analytical reasoning tasks, such as those required in science and mathematics

the right hemisphere is called the representational hempisphere: concerned with visuospatial relationships and analyses. seat of imagination and insight, musical and artistic skill, perception of patterns and spatial relationships , and comparision of sights, sounds, smells, and tastes

Question 10

How are the wernicke area and motor speech area connected?

Answer 10

wernicke area is involved in interpreting what we read or hear, whereas the motor speech area receives axons originating from the wernicke area and then help regulate the respiratory patterns and precise motor activites required to enable us to speak

Question 11

What are the ways in which memory is classified?

Answer 11

1. Sensory memory: when we form important associations based upon sensory input from the environment
2. Short term memory: follows sensory memory; generally characterized by limited capacity and a brief duration
3. Long term memory: may exist for limitless periods of time; info need to be retrieved occasionally or can be lost

Question 12

What is the conversion of short term to long term memory?

Answer 12

encoding or memory consolidation: requires the amygdaloid body and hippocampus

hippocampus required for the formation of STM, whereas long term memories are stored primarily in the association areas of the cerebral cortex

Question 13

What are the two subdivisions of which sleep can be divided?

Answer 13

1. non-rapid eye movement: primarily for body repair; 75% of total sleep time
2. rapid eye movement: other 25%