SF3-physiology Flashcards
Tonic receptors
-slow or nonexistent adaptation
-continous signal transmission as long as stimuli is present
-monitoring parameters are continuously raised
Ex. Posture, proprioceptiors
Physic receptors
-fast adaptation
-stop transmitting if intensity of stimulus is continous/constant
-allows body to ignore superficial and constant stimuli
Ex. Touch of clothes
On what does conduction velocity depend?
- the axons diameter
- degree of myelination (Salvatore conduction)
What are the two classes of nerve fibers?
General (motor+sensory):
-type A= large, myelinated fibers for fast signaling
-type C= small, unmyelinated fibers for slow signaling
Exclusive sensory:
-group 1A= fastest, muscle spindles
-group 1B= a bit slower, golgi tendon organs
-group 2= types A, discriminative touch
-group 3= types A,temperature, deep touch, acute pain
-group 4= type C, burning pain, itching, temperature, deep touch
What is somatovis real sensitivity?
In skin and mucus: -tactile sense (superficial) -thermoreception In locomotor system: -proprioception (deep) In most organs: -nociception (pain) In thoracoabdominal visceral: -visceral sensitivity
What is the tactile sense?
- The detecting of non-harmful mechanical stimuli
- processed in CNS
- touch, pressure, vibration, tickle
What kind of receptors does tactile sense have?
- slowly adapting mechanoreceptors
- rapidly adapting mechanoreceptors
- type C mechanoreceptors
What are the types of slowly adapting mechanoreceptors?
- Merkel’s discs
- ruffini’s endings
What are the types of rapidly adapting mechanoreceptors?
- meissner’s corpuscles
- krause’s corpuscles
- tactile hair
- type C fibers (free nerve endings)
What are the very rapidly adapting mechanoreceptor?
Pack Ian corpuscles
What is proprioception?
The sensory ability to control position and movement sequences
The perception of body in space
Where are the proprioception receptors localized?
In locomotor system
Muscles, tendons, bones, joints
What is the classification of proprioception receptors?
Muscle receptors:
- muscle spindle
-golgi tendon organ
Joint receptors
What is the muscle spindle?
- fusiform budles of encapsulated and specialized muscle fibers (intrafusal)
- sensitive to muscle stretching/change of length
What are the two types f intrafusal muscle fibers?
- nuclear bag fibers=central portion dilated with multiple nuclei inside
- nuclear chain fibers=nuclei arranged in a row
What are the sensory and motor components of muscle spindle?
- primary+secondary sensory nerve fibers spiraling around central portion of intrafusal fibers, inform of muscle stretching
- gamma motor neurons= a lower motor neuron keeping spindles tight, adjusting sensitivity
What are the muscle spindle sensory components?
primary/type 1a sensory fibers:
-wraps central part of both nuclear bag and chain fibers w annulospiral nerve endings
-rapid adaptation, constantly monitoring change in velocity of muscle stretch
Type 2 sensory fibers:
-innervates the ends of nuclear bag and chain fibers
-non adapting, informs about position continuously
What is the golgi tendon organ?
- proprioception receptor organ situated at the origins/insertion of muscles into tendons
- innervated by single afferent type 1b sensory nerve endings spiraling around collagen strands
- detects muscle tension, both contraction and extension
What are the types of receptors in proprioception?
- ruffini corpuscles= joint capsule, degree of rotation of joint
- pacini’s corpuscles= joint capsule, sense of speed of movement
- golgi tendon organs= ligaments, jerks or sudden contraction of tendon
- muscle spindles= muscles, length/time of contraction
What are the thermoreceptors?
-sense of cold= surface of skin, Krause’s corpuscle, free endings w myelin
-sense of heat= deeper layers, ruffini’s corpuscles, free unmyelinated endings
Rapid adaptation
What are the characteristics of nociceptors?
- free nerve endings
- non existing in CNS, most of viscera
- very little/no adaptation
- continue perceiving stimuli until it ends
What are the two types of pain?
Fast/acute pain: -mainly felt in superficial tissues -not felt in deeper tissues Slow/chronic pain: -associated w tissue destruction -can occur in almost all types of tissues
What are the types of nociceptors?
Polymodal:
-responds to mechanical, thermal, chemical high intensity stimuli
-slow, type C or 4 fibers
Mechanosensitive:
-fast pain, mechanical height intensity stimuli
-fibers A-delta or 3
-
What are the types of pain stimuli?
- Thermal pain= below 10, above 48 degrees
- chemical pain= bradykinin, histamine, serotonin, Ach, acids, K+
- mechanical pain= tissue disruption, ischemia, muscle spasm, excessive pressure
What is the analgesia system?
In CNS, controlsystem suppressing pain impulses
- areas in mesencephalon, upper pons, 3rd&4th ventricle
- areas of lower pons, upper&lateral medulla
- pain inhibitory complex in dorsal horns of spinal cord
What are the characteristics of visceral pain?
- mostly unconscious, related to regulation of activity
- most consciously perceived sensations in response to mechanical/chemical stimuli
- type 4 fibers
Most common causes of visceral pain?
- tissue ischemia
- chemical stimuli
- smooth muscle spasm
- inflammation
What is referred pain?
- sensation of pain in part of body not related to tissue causing pain
- convergence theory
Characteristics of conscious ascending tracts
3 neurons
- 1 neuron= sensory receptor of spinal nerve synapses in posterior root ganglion
- 2 neuron= decussates and travel up spinal cord
- 3 neuron= synapses in sensory nucleus in thalamus, projects to sensitive cerebral cortex
Lateral and anterior spinothalamic tracts
Lateral= pain and temperature
Anterior= crude touch, pressure
-1 neuron= enters dorsal root ganglia and synapses in posterior horns
-2 neuron= decussates and runs up through medial leminiscus of brain stem
-3 neuron= synapses in thalamus, through ventral posterolateral nucleus to sensory cortex
Leminiscal/dorsal column tract
Fine touch, vibration, awareness of muscle coordination
F. Gracilis= lumbosacral level
F. Cuneatus= cervical level
-1 neuron= enters dorsal root ganglia
-2 neuron= synapses in medulla, decussates and travels up medial lemniscus of brain stem
-3 neuron= synapses in ventral posterolateral nucleus of thalamus, ends sensory cortex
Characteristics of unconscious spinocerebellar tract
2 neurons, unconscious proprioception of extremities and trunk (golgi tendon organ, muscle spindle)
Posterior/dorsal= direct, lower extremities
Anterior/ventral= crossed, trunk/upper extremities
-1 neuron= enters via dorsal root ganglia, synapses in dark column of dorsal nucleus
-2 neuron= synapses, decussates (anterior)or not (posterior) ascends to medulla and/or pons, through cerebellum peduncles and ends at cerebellar cortex
Characteristics of motor neurons
- alpha motorneurons innervate extrafusal skeletal muscle fibers
- gamma motorneurons innervate intrafusal skeletal muscle fibers, makes up muscle spindle
Characteristics of conscious descending pathways
3 neurons
- 1 neuron= upper motor neuron, motor area of cerebral cortex, decussates and descends down to anterior horns of spinal cord
- 2 neuron= very short, synapses in anterior horn
- 3 neuron= lower motor neuron, exits through anterior root to skeletal muscle
What is the pyramidal system?
- Conscious
- Upper Motor neurons responsible for activating skeletal muscles for fine, voluntary and learnt movements
- corticospinal tracts (lateral/ventral)
What is the extrapyramidal system?
- unconscious
- upper motor neurons responsible for antigravity, involuntary and subconscious movements
- for the assistance, modulation and regulation of pyramidal system
- reticulospinal/vestibulospinal/rubrospinal/tactospinal/olivospinal tracts
Characteristics of pyramidal system?
Pass through: -internal capsule -cerebral peduncle -basal part of pons -pyramids of medulla 3 neurons= UMN+Interneuron=LMN
Lateral and anterior corticospinal tract
Fine movements, voluntary, learnt and conscious
- 1 neuron= UMN in ventral cortical layer of corona radiata, go to pyramids in medulla. Lateral decussates, anterior is ipsilateral
- 2 neuron=Interneuron, short, synapses in anterior horn of f spinal cord
- 3 neuron= LMN, synapses still in anterior horn, goes to skeletal muscle
What is the corticonuclear tract?
- Originating in face, primary motor cortex
- does not reach spinal cord
- involves the cranial nerves
- most fibers end in reticular nuclei
- most receive bilateral corticonuclear fibers
Characteristics of extrapyramidal system?
- involuntary motor tracts alternative to pyramidal tracts
- originates in brainstem, does not pass the medullary pyramids
- responsible for involuntary, subconscious and antigravity movement
- maintains balance/equilibrium, posture while voluntary movements are performed
Rubrospinal tract
Facilitates flexor activity, inhibits antigravity and flexor muscles
- 1 neuron= UMN in red nucleus of cerebral cortex & cerebellum, decussates and go through pons and medulla to lateral white matter
- 2 neuron= Interneuron, synapses in grey horns
- 3 neuron= LMN, from grey horns to skeletal muscle
Vestibulospinal tract
Facilitates extension, inhibits flexion, postural balance
- 1 neuron= UMN, lateral vestibular nucleus of pons and medulla, receives into from vestibular Nerve and cerebellum, ipsilateral
- 2 neuron= Interneuron, synapses in grey horns
- 3 neuron= LMN, from grey horns to skeletal muscle
Reticulospinal tract
Controls proximal and axial muscles, extensor responses (position)
- 1 neuron= UMN, reticular formation in midbrain, pons (mainly ipsilateral, pontine reticulospinal tract/medial to anterior white matter) medulla (crossed and direct, medullary reticulospinal tract/lateral to lateral white matter), receives info from cerebral cortex, thalamus, cerebellum.
- 2 neuron= Interneuron, short, synapses in grey horns
- 3 neuron= LMN, from grey horns to skeletal muscle
Tectospinal tract
Reflex postural movement of head due to visual/auditory movement
- 1 neuron= UMN, from superior culiculus of midbrain, decussates mainly, to anterior white matter
- 2 neuron= Interneuron, short, in grey horns
- 3 neuron= LMN, from grey horns to skeletal muscle
Olivospinal tract
Not known function
- 1 neuron= UMN, inferior Olivary nucleus of medulla, mainly decussates, go to lateral white matter
- 2 neuron= Interneuron, short, synapses in grey horns
- 3 neuron= LMN, from grey horns to skeletal muscle
External Chemoreceptors and their basic function
Sensory receptors responding to chemical changes
- alimentary
- defencive
- sexual
- communicator
The taste bud
2 types of modified epithelium
- taste cells
-basal cells (stem cells)
Taste pores is the only communication btw tastecells and exterior
Categories of taste
- sweet= organic molecules, sucrose, aldehyde
- bitter= alkaloids, Quinn, caffeine
- salty= ions of ionizable salts, NaCl, KCl
- umami= amino acids, glutamate
Channels for taste
Ion channels= salty, sour, bitter
Metabotrophic/G-protein= bitter, sweet
Taste transduction
- chemical stimuli
- membrane potential
- neurotransmission
- AP through sensory neuron
- impulse to CNS
Gustatory pathway
- 1 neuron= CN 7, 9, 10 sends signals to brainstem
- 2 neuron= synapses in gustatory nucleus of tractus solitarius in medulla
- 3 neuron= synapses in thalamus, ends in gustatory cortex
Structures of olfactory sensitivity
- Main Olfactory epithelium/MOE
- Main Olfactory bulb/MOB
- Vomeronasal organVNO
- Acessory olfactory bulb/AOB
Transduction pathway of olfactory sensitivity
- chemical signal in olfactory epithelium
- electric signal to OB
- electrical signalto brain
- olfactory tract
What are the three cell types of olfactory epithelium?
- supporting cells
- olfactory cells
- basal cells
