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Lesson 6
Sesation
Sensation- Perception- Response
- Sensory receptors
- CNS
- Sensory (ascending) pathways
- Motor (descending) pathways
- ANS
- Reflexes
Sensory receptors
Structures specialized to detect a sensory stimulus
● The Fundamental purpose of any sensory receptor is Transduction, or the conversion of a
stimulus into an electrical signal.
● What are the nerve signals?
○ Action Potential
● Are you conscious of every sensory signal that comes into your brain? What kinds of signals is
your brain receiving all the time?
○ NO! Think about heartbeat
● Sensation- a subjective awareness of the stimulus
● Most sensory signals delivered to the CNS produce no conscious sensation
○ Filtered out in the brainstem
○ Some do not require conscious awareness like pH and body temperature
● nicotinic receptors become ion channels for sodium upon binding of the acetylcholine to the
receptor whereas muscarinic receptors phosphorylate various second messengers
Receptor Potential – step 1
Voltage and Mechanically
gated sodium ion channel
(prior to stimulus they are
closed)
Mechanical gates open
because touching things is
mechanical stress!!! Leads to
local potentials!!!
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Receptor Potential – step 2
4 Kinds of information
Modality: type of stimulus or sensation it produces
● Does taste carry the same action potential as vision?
● How does our brain know we saw our laptop and not taste it, if all action potentials are the
same?
○ Somatotopy: the sensory homunculus reflects the relative space body parts occupy on
the primary somatosensory cortex.
Location: Encoded by which nerve fibers are issuing signals to the brain
● Two-point discrimination: some parts of your body have more nerve signals (makes it more
sensitive). You're more likely to feel a tap on your hand than on your shoulder.
Intensity: How strong the stimulus is
● Rate at which action potential is produced
● Number of sensory receptors activated
Duration: How long does the stimulus last
● phasic receptors are fast adapting
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○ Notify on change
● Tonic receptors are slow adapting
○ Notify on duration of the stimulus
Classification of sensory receptors
Sensory receptors are classified by their location
• Exteroceptors – surface of the body (outside stimuli)
• Interoceptors – within the body's interior (inside stimuli)
Sensory receptors can also be classified by the type of stimulation that cause them to depolarize and
generate a receptor potential
● Mechanoreceptors: respond to physical deformation of a cell or tissue
● Thermoreceptors: respond to thermal stimuli
● Chemoreceptors: respond to chemical signals in body fluids or air
● Photoreceptors: respond to changes in light
● Nociceptors: respond to noxious stimuli (pain)
Visceral Reflex Arcs
● Cell to cell communication
Autonomic Nervous System (ANS)
The ANS consists of neurons that:
● Make adjustments to ensure optimal support of physiological activities
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● Operate via subconscious control
Parasympathetic: rest and digest, originate from cranial nerves, ACH
Sympathetic: fight or flight, shorter preganglionic neurons and longer post ganglion neurons, NE
Somatic vs. autonomic nervous system
Sympathetic Neurotransmitters
If Ach was being sent, it has to be a nicotinic or
muscarinic receptor
Downloaded by madiba South Africa stuvia ()
Lesson 6
Sesation
Sensation- Perception- Response
- Sensory receptors
- CNS
- Sensory (ascending) pathways
- Motor (descending) pathways
- ANS
- Reflexes
Sensory receptors
Structures specialized to detect a sensory stimulus
● The Fundamental purpose of any sensory receptor is Transduction, or the conversion of a
stimulus into an electrical signal.
● What are the nerve signals?
○ Action Potential
● Are you conscious of every sensory signal that comes into your brain? What kinds of signals is
your brain receiving all the time?
○ NO! Think about heartbeat
● Sensation- a subjective awareness of the stimulus
● Most sensory signals delivered to the CNS produce no conscious sensation
○ Filtered out in the brainstem
○ Some do not require conscious awareness like pH and body temperature
● nicotinic receptors become ion channels for sodium upon binding of the acetylcholine to the
receptor whereas muscarinic receptors phosphorylate various second messengers
Receptor Potential – step 1
Voltage and Mechanically
gated sodium ion channel
(prior to stimulus they are
closed)
Mechanical gates open
because touching things is
mechanical stress!!! Leads to
local potentials!!!
Downloaded by madiba South Africa stuvia ()
, lOMoARcPSD|44532475
Receptor Potential – step 2
4 Kinds of information
Modality: type of stimulus or sensation it produces
● Does taste carry the same action potential as vision?
● How does our brain know we saw our laptop and not taste it, if all action potentials are the
same?
○ Somatotopy: the sensory homunculus reflects the relative space body parts occupy on
the primary somatosensory cortex.
Location: Encoded by which nerve fibers are issuing signals to the brain
● Two-point discrimination: some parts of your body have more nerve signals (makes it more
sensitive). You're more likely to feel a tap on your hand than on your shoulder.
Intensity: How strong the stimulus is
● Rate at which action potential is produced
● Number of sensory receptors activated
Duration: How long does the stimulus last
● phasic receptors are fast adapting
Downloaded by madiba South Africa stuvia ()
, lOMoARcPSD|44532475
○ Notify on change
● Tonic receptors are slow adapting
○ Notify on duration of the stimulus
Classification of sensory receptors
Sensory receptors are classified by their location
• Exteroceptors – surface of the body (outside stimuli)
• Interoceptors – within the body's interior (inside stimuli)
Sensory receptors can also be classified by the type of stimulation that cause them to depolarize and
generate a receptor potential
● Mechanoreceptors: respond to physical deformation of a cell or tissue
● Thermoreceptors: respond to thermal stimuli
● Chemoreceptors: respond to chemical signals in body fluids or air
● Photoreceptors: respond to changes in light
● Nociceptors: respond to noxious stimuli (pain)
Visceral Reflex Arcs
● Cell to cell communication
Autonomic Nervous System (ANS)
The ANS consists of neurons that:
● Make adjustments to ensure optimal support of physiological activities
Downloaded by madiba South Africa stuvia ()
, lOMoARcPSD|44532475
● Operate via subconscious control
Parasympathetic: rest and digest, originate from cranial nerves, ACH
Sympathetic: fight or flight, shorter preganglionic neurons and longer post ganglion neurons, NE
Somatic vs. autonomic nervous system
Sympathetic Neurotransmitters
If Ach was being sent, it has to be a nicotinic or
muscarinic receptor
Downloaded by madiba South Africa stuvia ()
