General Senses Flashcards
1
Q
General vs Special senses
A
- general sensory receptors (somatic receptors)
- no structural specializations in free nerve endings that provide us with pain, itch, tickle, temp
- some structural specializations in receptors for touch, pressure, vibration
- special sensory receptors
- very complex structures: vision, hearing, taste, smell
2
Q
Structural classification of receptors
A
- free nerve endings
- bare dendrites
- pain, temp, tickle, itch, light and touch
- encapsulated nerve endings
- dendrites enclosed in connective tissue capsule
- pressure vibration and deep touch
- separate sensory cells
- specialized cells that respond to stimuli
- vision, taste, hearing, balance
3
Q
Classification of receptors by location
A
- exteroceptors
- near surface of body
- receive external stimuli
- touch, pressure, pain, vibration and temp
- interoceptors
- monitors internal environment (viscera)
- not conscious except for pain or pressure
- proprioceptors
- muscle, tendon, joint, internal ear
- senses body position and movement
4
Q
Classification by stimuli detected
A
- mechanoreceptors
- touch, pressure, vibration, proprioception, hearing, equilibrium
- thermoreceptors detect temp
- nociceptors detect damage to tissues
- photoreceptors detect light
- chemoreceptors detect molecules
- taste, smell and changes in body fluid chemistry
5
Q
Somatic tactile sensations
A
- touch
- pain
- pressure
- temp
6
Q
Merkel’s Disc
A
- epidermis
- flattened dendrites touching cells of stratum basale
- used in discriminative touch
7
Q
Meissner’s corpuscle
A
- dendrites enclosed in CT in dermal papillae of hairless skin
- discriminative touch and vibration: rapidly adapting
- generate impulses mainly at onset of a touch, and then adapt to sensation
8
Q
Ruffin Corpuscle
A
- found deep in dermis of skin - reticular layer
- detect heavy touch, continuous touch, and pressure
9
Q
Pacinian Corpuscle
A
- onion-like connective tissue capsule enclosing a dendrite
- found in subcutaneous tissues and certain viscera
- sensations of pressure or high-frequency vibration
10
Q
Hair root plexus
A
-free nerve endings found around follicles, detects movement of hair
11
Q
Free nerve endings: pain and temp
A
- extend between layers of epidermis
- no connective tissue around them
- skin, viscera, muscles
- inadequate blood supply, distinction of stomach, muscle spasms
12
Q
Pain sensations
A
- nociceptors: pain receptors
- free nerve endings found in every tissue of body except brain
- stimulated by excessive distension, muscle spasms, inadequate blood flow
- tissue injury releases chemicals such as K+, kinins or prostaglandins that stimulate nociceptors
- little adaption occurs
13
Q
Referred Pain
A
- visceral pain that is felt just deep to the skin overlying the stimulated organ or in a surface area far from the organ
- skin area and organ are served by the same segment of the spinal cord
- heart attack is felt in skin along left arm since both are supplied by spinal cord segment T1-T5
14
Q
Pain relief
A
- aspiring and ibuprofen block formation of prostaglandins that stimulates nociceptors
- novacaine blocks conduction of nerve impulses along pain fibres
- morphine lessens perception of pain in the brain
- acupuncture
15
Q
Proprioceptive sensations
A
- awareness of boys position and movement
- walk or type without looking
- estimate weight of objects
- proprioceptors adapt only slightly
- proprioceptors: muscle spindles, Golgi tendon organs and joint receptors
16
Q
Muscle spindles
A
- specialized intrafusal muscles fibres enclosed in a CT capsule and inner aged by gamma motor neurons
- stretching of the muscle stretches the muscle spindles sending sensory information back to CNS
- feel stretch until a certain point
- reflexes to avoid tearing
17
Q
Golgi tendon organs
A
- found at junction of tendon and muscle
- consists of an encapsulated bundle of collagen fibres loaded with sensory fibres
- when the tendon is overly tense, sensory signals head to CNS and result in muscles relaxation
- sometimes not conscious
18
Q
Joint receptors
A
- ruffini corpuscles
- found in joint capsule
- respond to pressure
- pacinian corpuscles
- found in connective tissue around the joint
- respond to acceleration and deceleration of joints
19
Q
Somatic sensory pathways
A
- first order neuron conduct impulses to brain stem or spinal cord
- either spinal or cranial nerves
- second order neurons conducts impulses from spinal cord or brain stem to thalamus: cross over to opposite side before reaching thalamus
- third order neuron conducts impulses from thalamus to primary somatosensory cortex (postcentral gyrus of parietal lobe)
20
Q
Posterior column-medial lemiscus pathway of CNS
A
- touch and pressure, proprioception (vibration, discriminative touch, weight discrimination and stereognosis)
- signals travel up spinal cord in posterior column and synapse in nucleus gracious or cuneatus
- fibres cross over in medulla to become the medial lemniscus pathway ending in the thalamus
- thalamic fibres each somatosensory cortex
21
Q
Spinothalamic pathways
A
- anterior and lateral spinothalamic tracts carries pain and temperature
- first cell body in dorsal (posterior) root ganglion with synapses in spinal cord
- second cell body in gray matter of cord, sends fibres to other side of cord and up through white matter to synapse in thalamus
- third cell body in thalamus projects to cerebral cortex
- second order neurons cross
22
Q
Sensory innervation of head and face
A
- trigeminal cranial nerve (CN V)
- provides touch and pressure and pain and temp for the face and front of head
- sensory info from face relayed to thalamus then to postcentral gyrus
23
Q
Sensory pathways to cerebellum
A
- major routes for proprioceptive signals to reach cerebellum
- anterior spinocerebellar tract
- posterior spinocerebellar tract
- subconscious information used by cerebellum for adjusting posture, balance, and skilled movements
- signal travels up to Same side inferior cerebellar peduncle
- terminates on same side of cerebellum unlike contralateral processing in cerebral cortex
