Nervous System Physiology Part 5 Flashcards
What is the general function of sensory systems?
Receive information from the environment via specialized receptors in the periphery and transmit this information through a series of neurons and synaptic relays to the CNS.
What are the three main categories of sensory systems mentioned?
- Somatic senses
- Visceral senses
- Special senses
What types of sensations are included in the somatic senses?
Sensation from the skin, skeletal muscles, bones, tendons, and joints (touch, pressure, posture, movement, temperature, pain).
What do visceral senses detect?
Sensations of the internal organs.
What are the five special senses listed?
Vision, hearing, balance, taste, smell.
what does survival depend upon?
Survival depends upon sensation and perception.
Define sensation.
the awareness of changes in the internal and external environment.
Define perception.
the conscious interpretation of those stimuli (from sensation).
What is the origin of somatic senses?
Sensation from the skin, skeletal muscles, bones, tendons, and joints.
Activation of somatic receptors gives rise to the sensations of…?
Touch, pressure, awareness of the position of the body parts and their movement, temperature, and pain.
Give examples of the locations of somatic sensory receptors.
Skin (various types shown in the diagram), skeletal muscles (stretch receptors shown), tendons, and joints.
What type of nerve fibers enter the dorsal roots of the spinal cord carrying sensory information from somatic receptors?
Afferent nerve fibers (the first-order afferent neuron).
Where is the sensory information carried by the second-order afferent neuron transferred after the spinal cord?
The thalamus
Where is the sensory information transferred after the thalamus?
To the third-order neuron and carried to the cerebral cortex.
What are the two major types of somatosensory pathways from the body to the brain?
- The ascending anterolateral pathway
- The dorsal column pathway
Where does the ascending anterolateral pathway make its first synapse?
In the gray matter of the spinal cord.
What happens to the second neuron in the ascending anterolateral pathway after synapsing in the spinal cord?
This second neuron immediately crosses to the opposite side of the spinal cord and then ascends through the anterolateral column of the cord to the thalamus.
Where does the second neuron of the ascending anterolateral pathway synapse
In the thalamus, where it synapses on cortically projecting neurons.
What type of sensory information does the anterolateral pathway primarily process?
Pain and temperature information.
In the dorsal column pathway, do sensory neurons cross over or synapse immediately upon entering the spinal cord?
No, sensory neurons do not cross over or synapse immediately upon entering the spinal cord.
Where do the first-order neurons in the dorsal column pathway ascend?
They ascend on the same side of the spinal cord and make the first synapse in the brainstem.
Where does the second neuron in the dorsal column pathway cross over to the opposite side?
In the brainstem, as it ascends.
Where does the second synapse occur in the dorsal column pathway?
In the thalamus
Where do the projections from the thalamus in the dorsal column pathway go?
To the somatosensory cortex.
Where do both the anterolateral and dorsal column pathways cross over?
Both pathways cross from the side where the afferent neurons enter the central nervous system to the opposite side either in the spinal cord or in the brainstem.
Where do sensory pathways from somatic receptors on the left side of the body ultimately terminate in the cerebral hemisphere?
In the somatosensory cortex of the right cerebral hemisphere.
How does somatosensory information from the head and face travel to the brain?
It does not travel via the two main spinal cord pathways; it enters the brainstem directly via cranial nerves.
How many neurons typically conduct sensory impulses upward to the appropriate brain regions?
three neurons.
What are first-order neurons and what do they conduct impulses from and to?
- Sensory neurons
- Conduct impulses from the receptor level to the second-order neurons in the CNS.
What are second-order neurons and where do they transmit impulses to?
- Interneurons
- Transmit impulses to the thalamus or cerebellum.
What are third-order neurons and what do they conduct impulses from and to?
- Interneurons
- Conduct impulses from the thalamus to the somatosensory cortex (perceptual level).
