Chap 13 pt 2 Flashcards
Sensory Receptors
structures that monitor changes in specific variables inside and outside the body
Receptor Specificity
- end of afferent neuron
- each receptor responds to specific types of stimulus
- ex .pressure receptors are stimulated by pressure
2 types of senses
General and Special
General Senses
Temp, pain, touch, pressure, vibration, proprioception (muscle stretch)
General Sense Receptors
dendrite ends of afferent sensory neuron
Special Senses
Olfactory (smell), vision, gustation (taste), equilibrium (balance), hearing
Detection of stimulus
a change in the permeability of the membrane
Graded depolarization/ hyperpolarization
receptor potential
Depolarization of sensory neuron
generator potential
If stimulus is strong enough, summation of ___ ____ leads to the generation of an _____ _____
Graded Potentials, Action potential
Process of translating a stimulus into an action potential
transduction
Receptive field
area of body monitored by one particular afferent neuron and all its receptors
to generate conscious sensations, sensory info must be transmitted to the
cortex
Sensation
- raw experience
- may be unconscious
- activity in all sensory neurons
Perception
- conscious awareness of sensation
- activity in cerebral cortex
Labelled line
from receptor to specific neurons in cortex
Info about type, strength, duration, and variation of the stimulus is coded by:
- Type of sensory receptor
- rate of action potential
The harder the stimulus the ___ action potential
MORE
Tonic receptors
always active
Phasic receptors
- not always active
- fire only when stimulated
Reduction in sensitivity of nervous system to constant stimulus
adaption
Peripheral Adaption
phasic sensory receptors become less responsive
-ex. becoming used to background noise
Central Adaption
- central adaption
- inhibition
Higher centers can ___ receptor sensitivity or ____ transmission
increase, facilitate
Nociceptors
-pain
Where? -walls of blood vessels
Responds to? temps, mechanical damage
Thermoreceptors
- dermis
- info sent along lateral spinothalamic
- fast adapting
Mechanoreceptors
-Respond to: stimuli that distort cell membrane
Chemoreceptors
detects changes in pH, O2 and CO2
First order neurons
- afferent, sensory neurons
- location: dorsal root
Second Order neurons
- interneurons
- location: MO or posterior/ dorsal horn
Third order neurons
-thalamus
-
Sensory pathways can be divided into
- somatic sensory pathways
- visceral sensory pathways
Somatic Sensory pathways
sensory info from skin, muscles, joints
Visceral Sensory pathways
sensory info from visceral tissues and organs
3 major pathways of somatic sensory pathways
- Posterior column pathway
- Anterior Spinothalamic pathway/ Lateral Spinothalamic Pathway
- Spinocerebellar Pathway
Posterior Column Pathway
PFPV- pressure, fine touch, vibration, proprioception
- origin of second neuron: MO
- Ascends: Posterior column
- Site of decussation: MO
Anterior Spinothalamic Pathway
CAP- Crude touch And Pressure
- origin of second neuron: Anterior column
- Site of decussation: 2nd order neuron crosses in spinal cord
Lateral Spinothalamic Pathway
PAT- Pain And Temp
- origin of 2nd order neuron: posterior/dorsal horn of spinal segment
- Ascends: Lateral Column
- Site of decussation: 2nd order neuron in spinal cord
Spinocerebellar pathway
- does not go to cortex
- position of muscles, joints, tendons, and cerebellum
- Origin of 2nd order neurons: dorsal gray horns
- termination of 2nd order neurons: cortex of cerebellum
Referred pain is due to _____ of afferent neurons on same interneuron
convergence
Visceral Sensory Pathways
monitor visceral tissues and organs
- 2nd order neurons ascend via: spinothalamic pathway
- terminate : in solitary nucleus of the MO
Somatic NS
Controls skeletal muscles
Somatic motor pathways involves 2 motor neurons:
- Upper and lower motor neurons
- both in cell body
Upper motor Neurons
In CNS processing center
Lower Motor Neuron
In brain stem or spinal cord
Motor Homunculus
different parts of primary motor cortex control different regions of body
- Corticospinal Pathway
provides voluntary control
- Corticobulbar tact
- Lateral Corticospinal tract
- Anterior Corticospinal tract
Corticobulbar
Crosses over in brain stem
Lateral Corticospinal
descends on opposite side to synapse with LMNs in anterior gray horns
Anterior Corticospinal
crosses over in spinal cord
- Medial Pathways
- axons cross immediately
- controls gross movements of trunk and proximal limb muscles and eye, head and neck
- Lateral pathway
controls precise movements of distal upper limb, but not fine finger movements
Somatic motor pathways are also overseen by
basal nuclei and cerebellum
Basal Nuclei deep within
cerebral hemispheres
Basal nuclei function
provide background patterns of activity in voluntary movements
Basal nuclei operated by
upper and lower motor neuron
2 major pathways of Basal Nuclei operation
- thalamic neurons
- brainstem
Cerebellum
receives sensory info from proprioceptors and eyes also balance from ears
Cerebellum function
modifies activities of upper motor neurons to generate smooth, accurate movements and maintains balance