Anatomy

Any stimuli the body is aware of

What are we not aware of? And why?

The conscious awareness & interpretation of a sensation

Precisely localization & identification

Where are our memories of perceptions stored?

Has no structural specializations in free nerve endings that provide us with pain, tickle, itch, temperatures

Has some structural specializations in receptors for touch, pressure & vibration

Very complex structures---vision, hearing, taste, & smell

How are sensory receptors classified?

Structural Classification of Receptors:
– bare dendrites
– pain, temperature, tickle, itch & light touch

Structural Classification of Receptors:
– dendrites enclosed in connective tissue capsule
– pressure, vibration & deep touch

Structural Classification of Receptors:
– specialized cells that respond to stimuli
– vision, taste, hearing, balance

Classification by Location:
– near surface of body
– receive external stimuli
– touch, pressure, pain, vibration & temperature

Classification by Location:
– monitors internal environment (BV or viscera)
– not conscious except for pain or pressure

Classification by Location:
– near surface of body
– receive external stimuli
– touch, pressure, pain, vibration & temperature

Classification by Location:
– monitors internal environment (BV or viscera)
– not conscious except for pain or pressure

Classification by Location:
– muscle, tendon, joint & internal ear
– senses body position & movement

Classification by Stimuli Detected:
– detect pressure or stretch
– touch, pressure, vibration, hearing, proprioception, equilibrium & blood pressure

What detects temperature?

Detect damage to tissues

Detect light

Detect molecules
– taste, smell & changes in body fluid chemistr

Name the 4 Somatic Tactile Sensations

Flattened dendrites touching cells of stratum basale
Used in discriminative touch

Dendrites enclosed in CT in dermal papillae of hairless skin
Discriminative touch & vibration-- rapidly adapting • Generate impulses mainly at onset of a touch

Free nerve endings found around follicles, detects movement of hair

Found deep in dermis of skin
Detect heavy touch, continuous touch, & pressur

Onion-like connective tissue capsule enclosing a dendrite
Found in subcutaneous tissues & certain viscera Sensations of pressure or high-frequency vibration

Pain receptors

Free nerve endings found in every tissue of body except ____ _______

Stimulated by excessive distension, muscle spasm, & inadequate blood flow

What causes the release of chemicals such as K+, kinins or prostaglandins that stimulate nociceptors

Little adaptation occur

Pain that is felt just deep to the skin overlying the stimulated organ or in a surface area far from the organ.

Skin area & organ are served by the same segment of the _____ _____

Felt in skin along left arm since both are supplied by spinal cord segment T1-T5

block formation of prostaglandins that stimulate nociceptors

Blocks conduction of nerve impulses along pain fibers

Lessens the perception of pain in the brain.

Awareness of body position & movement
– walk or type without looking
– estimate weight of objects

Sensation that adapts only slightly

Musle spindles, Golgitendon organs and joint receptor

Specialized intrafusal muscle fibers enclosed in a CT capsule and innervated by gamma motor neurons

Stretching of the muscle stretches the _______ _______ sending sensory information back to the CN

Found at junction of tendon & muscle

Consists of an encapsulated bundle of collagen fibers laced with sensory fibers

When the tendon is overly stretched, sensory signals head for the _______ & resulting in the muscle’s __________

Joint Receptors:
Found in joint capsule
Respond to pressure

Found in connective tissue around the joint
Respond to acceleration & deceleration of joints

First-order neuron conduct impulses to ________ or _______ ______

What type of nerve: first-order neuron conduct impulses to brainstem or spinal cord

conducts impulses from spinal cord or brainstem to thalamus--cross over to opposite side before reaching thalamus

Conducts impulses from thalamus to primary somatosensory cortex (postcentral gyrus of parietal lobe)

vibration, discriminative touch, weight discrimination & stereognosis

Signals travel up spinal cord in posterior column and synapse in _________ _______ or __________

Fibers cross-over in medulla to become the medial lemniscus pathway ending in __________

What do thalamic fibers reach?

Spinothalamic Pathways:
What do anterior and lateral spinothalamic tract carry?

Spinothalamic Pathways:
First cell body in ______ with synapses in cord

Spinothalamic Pathways:
In gray matter of cord, sends fibers to other side of cord & up through white matter to synapse in thalamus

In thalamus projects to cerebral cortex

Sensory Innervation for the Head and Face:
Provides touch and pressure and pain and temperature for the face and front of the head

Somatosensory Map of Postcentral Gyrus:
Proportional to number of sensory receptors
Proportional to the sensitivity of each part of the body

Sensory Pathways to the Cerebellum:
Major routes for proprioceptive signals to reach the cerebellum

Used by cerebellum for adjusting posture, balance & skilled movements

Sensory Pathways to the Cerebellum:
Signal travels up to same side of the ________ ________ _________