Peripheral Nervous System
A. Sensory Receptors
1. Properties of receptors
A) All receptors are transducers
1) They convert one form of stimulus into nerve energy
B) All receptors transmit 4 kinds of information to the CNS
1) Modality – the type of sensation
a) Law of Specific Nerve Energies – a receptor can respond to many types of
stimuli but conveys only one sensation
2) Location
3) Intensity
4) Duration
a) Some receptors experience adaptation
i) Prolonged stimulus leads to a decreased firing by the receptor
2. Sensory receptors are classified on the basis of location and type of stimulation
A) Location
1) Exteroceptors – stimulation arising outside of the body (examples: touch, pain,
pressure, and external temperature)
2) Interoceptors – stimulation arising inside of the body (examples: chemical
levels, stretching of tissues, and internal temperature)
3) Proprioceptors – respond to internal stimuli but located only in skeletal muscle,
tendons, joints, ligaments, and connective tissue covering bones and muscles
a) Monitor stretch and body position
B) Type of stimulus detected
1) Mechanoreceptors – touch & pressure, hearing & equilibrium
2) Thermoreceptors – temperature changes
3) Photoreceptors – light
4) Chemoreceptors – smell, taste, and blood chemicals
5) Baroreceptors – stretch (blood pressure)
6) Nociceptors (free nerve ending) – pain
3. General sensory receptors
A) Unencapsulated – bare dendrites
1) Free dendritic endings (free nerve endings)
a) Located in most body tissues
b) Respond primarily to pain and temperature
2) Merkel discs
a) Located in the basal layers of the epidermis
b) Respond to touch
3) Root hair plexus
a) Nerve endings that surround hair follicles
b) Respond to touch
B) Encapsulated – enclosed in a connective tissue capsule
1) Meissner’s corpuscles
A. Sensory Receptors
1. Properties of receptors
A) All receptors are transducers
1) They convert one form of stimulus into nerve energy
B) All receptors transmit 4 kinds of information to the CNS
1) Modality – the type of sensation
a) Law of Specific Nerve Energies – a receptor can respond to many types of
stimuli but conveys only one sensation
2) Location
3) Intensity
4) Duration
a) Some receptors experience adaptation
i) Prolonged stimulus leads to a decreased firing by the receptor
2. Sensory receptors are classified on the basis of location and type of stimulation
A) Location
1) Exteroceptors – stimulation arising outside of the body (examples: touch, pain,
pressure, and external temperature)
2) Interoceptors – stimulation arising inside of the body (examples: chemical
levels, stretching of tissues, and internal temperature)
3) Proprioceptors – respond to internal stimuli but located only in skeletal muscle,
tendons, joints, ligaments, and connective tissue covering bones and muscles
a) Monitor stretch and body position
B) Type of stimulus detected
1) Mechanoreceptors – touch & pressure, hearing & equilibrium
2) Thermoreceptors – temperature changes
3) Photoreceptors – light
4) Chemoreceptors – smell, taste, and blood chemicals
5) Baroreceptors – stretch (blood pressure)
6) Nociceptors (free nerve ending) – pain
3. General sensory receptors
A) Unencapsulated – bare dendrites
1) Free dendritic endings (free nerve endings)
a) Located in most body tissues
b) Respond primarily to pain and temperature
2) Merkel discs
a) Located in the basal layers of the epidermis
b) Respond to touch
3) Root hair plexus
a) Nerve endings that surround hair follicles
b) Respond to touch
B) Encapsulated – enclosed in a connective tissue capsule
1) Meissner’s corpuscles
