1. LAB EXERCISE 18 GENERAL SENSES

2. Sensory Information Afferent Division of the Nervous System Receptors
Sensory neurons
Sensory pathways
Spinal cord to brain
Deliver somatic and visceral sensory information to their final destinations inside the CNS using:
Nerves
Nuclei
Sensory tracts
Sensory processing centers in brain
Higher-Order Functions
Conscious and subconscious motor centers in brain
Memory, learning, and intelligence may influence interpretation of sensory information and nature of motor activities
Sensory pathways
General sensory receptors

3. Somatic Nervous System (SNS)
Sensory Information
Somatic Motor Portion of the Efferent Division
Controls peripheral effectors
Skeletal muscle
Somatic Motor Commands
Travel from motor centers in the brain along somatic motor pathways of:
Motor nuclei
Tracts
Nerves
Motor pathways
Somatic Nervous System (SNS)
Skeletal muscles

4. Sensory Receptors General Senses Describe our sensitivity to:
Temperature
Pain
Touch
Pressure
Vibration
Proprioception

5. Sensory Receptors Special Senses The Special Senses
Are provided by special sensory receptors
Olfaction (smell)
Vision (sight)
Gustation (taste)
Equilibrium (balance)
Hearing

6. SENSATION VS PERCEPTION
Occurs when nerve impulses arrive at the cerebral cortex
From sensory neurons created by an action potential.
Chemoreceptors
Thermoreceptors
Nociceptors
Baroreceptors
What we are not aware of

7. SESNSATION VS PERCEPTION
Perception is the conscious awareness & interpretation of a sensation
Occurs when the cerebral cortex interprets the meaning of sensations.
We have no perception of some information because it never reaches the cortex.
Blood pressure is received in the medulla

8. Sensory Integration Input comes from Exteroceptors Interoceptors
Proprioceptors
Input is relayed toward the head, and is processed along the way

9. Sensory Receptors Exteroceptors
Respond to stimuli arising outside the body
Receptors in the skin
Touch
Pressure
Pain
Temperature
Most special sense organs
Vision
Hearing
Equilibrium
Taste
Smell

10. Sensory Receptors Interoceptors **Visceroceptors
Respond to stimuli arising in internal viscera and blood vessels
Sensitive to
Chemical changes
Tissue stretch
Temperature changes
Pain
Discomfort
Hunger
Thirst

11. Sensory Receptors Proprioceptors Provide a purely somatic sensation
Respond to stretch in
Skeletal muscles
Tendons
Joints
Ligaments
Connective tissue coverings of bones and muscles
Inform the brain of one’s body movements
No proprioceptors in the visceral organs of the thoracic and abdominopelvic cavities
You cannot tell where your spleen, appendix, or pancreas is at the moment
Sensory Receptors

12. Processing at the Circuit Level
This level consists of pathways of three neurons conduct sensory impulses upward to the appropriate brain regions
First order neurons
Second order neurons
Third order neurons

13. Processing at the Circuit Level
First order neurons
Conduct impulses from the receptor level to the second-order neurons in the brain stem or spinal cord

14. Processing at the Circuit Level
Second-order neurons
Transmit impulses to the
Thalamus
Tracts cross over

15. Processing at the Circuit Level
Third-order neurons
Conduct impulses from
The thalamus to
The somatosensory cortex
Perceptual level

16. Processing at the Perceptual Level
The axons of the third order continue to ascend without crossing over to the somatosensory area.
As a result
Left cerebral hemispheres receive info from the right side
Right cerebral hemispheres receive info from the left side

17. Sensory Receptors Learning Outcomes
15-3 Identify the receptors for the
general senses, and describe
how they function.

18. Sensory Receptors General Sensory Receptors
Are divided into four types by the nature of the stimulus that excites them
Chemoreceptors
**Chemical concentration
Nociceptors
**Pain
3. Thermoreceptors
**Temperature
4. Mechanoreceptors
**Physical distortion

19. Classifying Sensory Receptors
Nociceptors (Pain Receptors)
Most concentrated in the superficial portions of the skin
In joint capsules
Within the periostea of bones
Around the walls of blood vessels

20. Classifying Sensory Receptors
Nociceptors
Are free nerve endings with large receptive fields
May be sensitive to:
Temperature extremes
Mechanical damage
Dissolved chemicals, such as chemicals released by injured cells
*Associated with tissue damage
Type A or Type C

21. Classifying Sensory Receptors
Myelinated Type A Nociceptor fibers
Carry sensations of fast pain, or prickling pain, such as that caused by an injection or a deep cut
Sensations reach the CNS quickly and often trigger somatic reflexes
Relayed to the primary sensory cortex and receive conscious attention

22. Classifying Sensory Receptors
Type C Nociceptor fibers
Carry sensations of slow pain, or burning and aching pain
Cause a generalized activation of the reticular formation and thalamus
You become aware of the pain but only have a general idea of the area affected

23. Classifying Sensory Receptors
-Referred pain
“Incorrect" source perceived
*Pain in the forehead when eating ice cream too quick
*Heartburn
*Dentistry
*Angina
–Pain in the arm when the heart does not receive enough oxygen
Classifying Sensory Receptors

24. Classifying Sensory Receptors
Thermoreceptors
Also called temperature receptors
Are free nerve endings located in:
The dermis
Skeletal muscles
The liver
The hypothalamus

25. Classifying Sensory Receptors
Mechanoreceptors
Sensitive to stimuli that distort their plasma membranes
Contain mechanically gated ion channels whose gates open or close in response to:
Stretching
Compression
Twisting
Other distortions of the membrane

26. Classifying Sensory Receptors
Three Classes of Mechanoreceptors
Tactile receptors
Provide the sensations of
Touch
Shape & texture
Pressure
Degree of distortion
Vibration
Pulsing or oscillating pressure

27. Classifying Sensory Receptors
Three Classes of Mechanoreceptors
Baroreceptors
Detect pressure changes in
Walls of blood vessels
Portions of the digestive
Portions of the reproductive
Portions of the urinary tracts

28. Classifying Sensory Receptors
Three Classes of Mechanoreceptors
Proprioceptors
Monitor the positions of joints and muscles
The most structurally and functionally complex of general sensory receptors

29. Classifying Sensory Receptors
Tactile Receptors
Fine touch and pressure receptors
Are extremely sensitive
Have a relatively narrow receptive field
Provide detailed information about a source of stimulation
Including its exact location, shape, size, texture, movement

30. Classifying Sensory Receptors
Tactile Receptors
Fine touch and pressure receptors
Are extremely sensitive
Have a relatively narrow receptive field
Provide detailed information about a source of stimulation
Including its exact location, shape, size, texture, movement

31. Classifying Sensory Receptors
Tactile Receptors
Crude touch and pressure receptors
Have relatively large receptive fields
Provide poor localization
Give little information about the stimulus

32. Classifying Sensory Receptors
Six Types of Tactile Receptors in the Skin
Free Nerve Endings
Sensitive to touch and pressure
Situated between epidermal cells
Free nerve endings providing touch sensations are tonic receptors with small receptive fields

33. Classifying Sensory Receptors
Six Types of Tactile Receptors in the Skin
Root hair plexus nerve endings
Monitor distortions and movements across the body surface wherever hairs are located
Adapt rapidly, so are best at detecting initial contact and subsequent movements

34. Classifying Sensory Receptors
Six Types of Tactile Receptors in the Skin
Tactile discs
Also called Merkel discs
Fine touch and pressure receptors
Extremely sensitive to tonic receptors
Have very small receptive fields

35. Classifying Sensory Receptors
Six Types of Tactile Receptors in the Skin
Tactile corpuscles
Also called Meissner’s corpuscles
Perceive sensations of fine touch, pressure, and low-frequency vibration
Adapt to stimulation within 1 second after contact
Fairly large structures
Most abundant in the eyelids, lips, fingertips, nipples, and external genitalia

36. Classifying Sensory Receptors
Six Types of Tactile Receptors in the Skin
Lamellated corpuscles
Also called Pacinian corpuscles
Sensitive to deep pressure
Fast-adapting receptors
Most sensitive to pulsing or high-frequency vibrating stimuli

37. Meissner’s vs Pacinian
If you close your eyes and have a friend place an object in the open palm of your hand, chances are good you will be able to detect the object but you will not be able to identify it.
By moving the object to your finger tips where Meissner's corpuscles are abundant, you gather information about its shape, texture, and density, information your brain uses to identify the object.
The Pacinian corpuscles enable you to detect the object due to its weight.
Meisner’s enable you to define it by fine touch

38. Classifying Sensory Receptors
Six Types of Tactile Receptors in the Skin
Ruffini corpuscles
Also sensitive to pressure and distortion of the skin
Located in the reticular (deep) dermis
Tonic receptors that show little if any adaptation

39. Classifying Sensory Receptors
Baroreceptors
Monitor change in pressure
Consist of free nerve endings that branch within elastic tissues
In wall of distensible organ (such as a blood vessel)
Respond immediately to a change in pressure, but adapt rapidly

40. Classifying Sensory Receptors
Proprioceptors
Monitor:
Position of joints
Tension in tendons and ligaments
State of muscular contraction

41. Classifying Sensory Receptors
Three Major Groups of Proprioceptors
Muscle spindles
Golgi tendon organs
Receptors in joint capsules

42. Classifying Sensory Receptors
Muscle Spindles
Monitor skeletal muscle length
Trigger stretch reflexes

43. Classifying Sensory Receptors
Golgi Tendon Organs
Located at the junction between skeletal muscle and its tendon
Stimulated by tension in tendon
Monitor external tension developed during muscle contraction

44. Classifying Sensory Receptors
Receptors in Joint Capsules
Free nerve endings detect pressure, tension, movement at the joint

45. Chemoreceptors
Respond to small concentration changes of specific molecules (chemicals)
Internal chemoreceptors monitor blood composition (e.g. Na+, pH, pCO2 )
Found within aortic and carotid bodies
Very important for homeostasis

46. Chemoreceptors
Respond to small concentration changes of specific molecules (chemicals)
Internal chemoreceptors monitor blood composition (e.g. Na+, pH, pCO2 )
Found within aortic and carotid bodies
Very important for homeostasis

47. IN REVIEW
IN REVIEW