-
Any stimuli the body is aware of
Stimuli
-
What are we not aware of? And why?
- X-rays
- Ultra high frequency sound waves
- UV Light
- Because we have no sensory receptors for those stimuli
-
The conscious awareness & interpretation of a sensation
Perception
-
Precisely localization & identification
Perception
-
Where are our memories of perceptions stored?
Cortex
-
Has no structural specializations in free nerve endings that provide us with pain, tickle, itch, temperatures
General Sensory Receptors (Somatic Receptors)
-
Has some structural specializations in receptors for touch, pressure & vibration
General Sensory Receptors (Somatic Receptors)
-
Very complex structures---vision, hearing, taste, & smell
Special Sensory Receptors (Special Sense Receptors)
-
How are sensory receptors classified?
- 1. Structural classification
- 2. Location of receptors & origin of stimuli
- 3. Type of stimuli they detect
-
Structural Classification of Receptors:
– bare dendrites
– pain, temperature, tickle, itch & light touch
Free nerve endings
-
Structural Classification of Receptors:
– dendrites enclosed in connective tissue capsule
– pressure, vibration & deep touch
Encapsulated nerve endings
-
Structural Classification of Receptors:
– specialized cells that respond to stimuli
– vision, taste, hearing, balance
Separate sensory cells
-
Classification by Location:
– near surface of body
– receive external stimuli
– touch, pressure, pain, vibration & temperature
Exteroceptors
-
Classification by Location:
– monitors internal environment (BV or viscera)
– not conscious except for pain or pressure
Interoceptors
-
Classification by Location:
– near surface of body
– receive external stimuli
– touch, pressure, pain, vibration & temperature
Exteroceptors
-
Classification by Location:
– monitors internal environment (BV or viscera)
– not conscious except for pain or pressure
Interoceptors
-
Classification by Location:
– muscle, tendon, joint & internal ear
– senses body position & movement
Proprioceptors
-
Classification by Stimuli Detected:
– detect pressure or stretch
– touch, pressure, vibration, hearing, proprioception, equilibrium & blood pressure
Mechanoreceptors
-
What detects temperature?
Thermoreceptors
-
Detect damage to tissues
Nociceptors
-
Detect light
Photoreceptors
-
Detect molecules
– taste, smell & changes in body fluid chemistr
Chemoreceptors
-
Name the 4 Somatic Tactile Sensations
- 1. Touch
- 2. Pressure
- 3. Pain
- 4. Temperature
-
Flattened dendrites touching cells of stratum basale
Used in discriminative touch
Merkel's Disc
-
Dendrites enclosed in CT in dermal papillae of hairless skin
Discriminative touch & vibration-- rapidly adapting • Generate impulses mainly at onset of a touch
Meissner's Corpuscle
-
Free nerve endings found around follicles, detects movement of hair
Hair Root Plexus
-
Found deep in dermis of skin
Detect heavy touch, continuous touch, & pressur
Ruffini Corpuscle
-
Onion-like connective tissue capsule enclosing a dendrite
Found in subcutaneous tissues & certain viscera Sensations of pressure or high-frequency vibration
Pacinian Corpuscle
-
Pain receptors
Nociceptors
-
Free nerve endings found in every tissue of body except ____ _______
the brain
-
Stimulated by excessive distension, muscle spasm, & inadequate blood flow
Pain sensation
-
What causes the release of chemicals such as K+, kinins or prostaglandins that stimulate nociceptors
Tissue injury (a pain sensation)
-
Little adaptation occur
Pain sensations
-
Pain that is felt just deep to the skin overlying the stimulated organ or in a surface area far from the organ.
Visceral pain
-
Skin area & organ are served by the same segment of the _____ _____
Spinal cord
-
Felt in skin along left arm since both are supplied by spinal cord segment T1-T5
Heart attack
-
block formation of prostaglandins that stimulate nociceptors
Aspirin & Ibuprofen
-
Blocks conduction of nerve impulses along pain fibers
Novocaine
-
Lessens the perception of pain in the brain.
Morphine
-
Awareness of body position & movement
– walk or type without looking
– estimate weight of objects
Proprioceptive Sensations
-
Sensation that adapts only slightly
Proprioceptors
-
Musle spindles, Golgitendon organs and joint receptor
Proprioceptors
-
Specialized intrafusal muscle fibers enclosed in a CT capsule and innervated by gamma motor neurons
Muscle Spindles
-
Stretching of the muscle stretches the _______ _______ sending sensory information back to the CN
muscle spindles
-
Found at junction of tendon & muscle
Golgi Tendon Organs
-
Consists of an encapsulated bundle of collagen fibers laced with sensory fibers
Golgi Tendon Organs
-
When the tendon is overly stretched, sensory signals head for the _______ & resulting in the muscle’s __________
CNS; relaxation
-
Joint Receptors:
Found in joint capsule
Respond to pressure
Ruffini corpuscles
-
Found in connective tissue around the joint
Respond to acceleration & deceleration of joints
Pacinian corpuscles
-
First-order neuron conduct impulses to ________ or _______ ______
brainstem; spinal cord
-
What type of nerve: first-order neuron conduct impulses to brainstem or spinal cord
Either spinal or cranial nerves
-
conducts impulses from spinal cord or brainstem to thalamus--cross over to opposite side before reaching thalamus
Second-order neurons
-
Conducts impulses from thalamus to primary somatosensory cortex (postcentral gyrus of parietal lobe)
Third-order neuron
-
vibration, discriminative touch, weight discrimination & stereognosis
Touch and Pressure Proprioception
-
Signals travel up spinal cord in posterior column and synapse in _________ _______ or __________
nucleus gracilus or cuneatus
-
Fibers cross-over in medulla to become the medial lemniscus pathway ending in __________
thalamus
-
What do thalamic fibers reach?
Somatosensory cortex
-
Spinothalamic Pathways:
What do anterior and lateral spinothalamic tract carry?
pain & temperature
-
Spinothalamic Pathways:
First cell body in ______ with synapses in cord
DRG
-
Spinothalamic Pathways:
In gray matter of cord, sends fibers to other side of cord & up through white matter to synapse in thalamus
2nd cell body
-
In thalamus projects to cerebral cortex
3rd cell body
-
Sensory Innervation for the Head and Face:
Provides touch and pressure and pain and temperature for the face and front of the head
Trigeminal Cranial nerve (CN V)
-
Somatosensory Map of Postcentral Gyrus:
Proportional to number of sensory receptors
Proportional to the sensitivity of each part of the body
Relative sizes of cortical areas
-
Sensory Pathways to the Cerebellum:
Major routes for proprioceptive signals to reach the cerebellum
- 1. anterior spinocerebellar tract
- 2. posterior spinocerebellar tract
-
Used by cerebellum for adjusting posture, balance & skilled movements
Subconscious information
-
Sensory Pathways to the Cerebellum:
Signal travels up to same side of the ________ ________ _________
inferior cerebellar peduncle
|
|