Class 8

somatic sensory and visceral sensory make up the

afferent division

somatic motor and visceral motor come from the

efferent division

what is the visceral motor broken down into

sympathetic and parasympathetic

includes the cranial nerves, spinal nerves, their roots/branches, peripheral nerves, and neuromuscular junctions

PNS

what are the general and specialized functions for somatic sensory

general: touch, pain, pressure

specialized: hearing, vision, smell

what are the general and specialized functions of the visceral sensory

general: stretch, pain, temperature, hunger

specialized: taste

what is the general function for somatic motor

all skeletal muscles

what is the general function for visceral motor

smooth/cardiac muscle, glands

what is the visceral motor equivalent to

ANS

(afferent) information from PNS via spinal cord goes to

higher CNS levels

(efferent) information from higher CNS levels via spinal cord go to

PNS and effectors

what carries sensory information from the periphery to the CNS

1st order sensory neuron

where is the first order sensory neuron located and what does it do

in the periphery, detects the stimulus and sends it to the spinal cord or medulla

what is the role of the second order sensory neuron

located in the spinal cord or medulla, relays information and synapses with the third order sensory neuron

where is the third order sensory neuron found

thalamus

what is the function of the third order sensory neuron

transmits information to the cerebral cortex for perception

which sensory neuron is in the peripheral nervous system

first order

what do the receptive fields of the three primary sensory neurons do

overlap to form one large secondary receptive field

what is the link between the periphery and CNS

PNS

what carries info between the CNS and other parts of the body

nerve fibers

info from receptors to CNS about the inside and outside organs

Afferent

responses from CNS to effectors to make the body act

efferent

between sensory and motor, which is related to afferent and which is efferent 

affernet: sensory

efferent: motor

sensory info that is processed

where can sensory information be processed before reaching the primary sensory cortex?

in the spinal cord, or directly to the brain stem and thalamus

what are the 3 main categories of sensory information

Visceral, somatic, and special senses

what does somatic sensory information include

pain, temp, tactile (touch), and proprioception (skin, muscles, joints, inner ear)

what does visceral sensory information include

pain, temp, stretch, chemical signals, osmotic changes from internal organs

what are the special senses

vision, hearing, balance, taste, smell

at peripheral endings of afferent neurons or receptor cells detect stimuli (change that is detectable by the body)

sensory receptors

conversion of different forms of energy into electrical signals (APs)

sensory transduction

different types of sensation - e.g, sound, light, taste touch, etc..

modality

what are the three categories of sensory receptors based on the source of stimuli

exteroreceptors

proprioceptors

interoreceptors

for information from the external world (hearing, vision, touch)

exteroreceptor

for information from the musculoskeletal system (deep sensation from muscles, tendons, joints)

proprioceptors

for information from the internal organs

interoreceptors

what are the 6 categories of receptors based on function/modality

1. photoreceptors

2. mechanoreceptors

3. thermoreceptors

4. nociceptors

5. chemoreceptors

6. osmoreceptors

responsive to visible wavelengths of light

photoreceptors

sensitive to mechanical energy

mechanoreceptors

sensitive to heat and cold

thermoreceptors

sensitive to pain

nociceptors

sensitive to specific chemicals

includes receptors for smell and taste that detect O2 and CO2 concentrations in blood and chemical content of digestive tract

chemoreceptors

detect change in osmotic pressure

osmoreceptors

each type of receptor is specialized to one type of stimulus, requires the least amount of energy to activate the receptor

adequate stimulus

the sensation characteristics of each sensory neuron is that produced by its adequate stimulus

law of specific nerve energies

what is an example of an adequate stimulus

in photoreceptors, the adequate stimulus is light, it requires the least amount of energy to activate

what are the 3 things structures that receptors can be

1. receptors can be the free nerve endings (nociceptors)

2. receptors can be specialized endings of sensory neurons (encapsulated receptors)

3. receptors can be specialized structures that have synaptic connections with sensory axons (photoreceptors, taste buds, hair cells)

what does a stimulus do to a receptor’s permeability

alters permeability by causing nonselective opening of small ion channels

which ion usually enters during receptor potential formation, and what effect does it have

Sodium ions (influx), depolarizes the receptor membrane 

what is the local depolarization called in a separate receptor vs a nerve fiber ending

separate: receptor potential

nerve endings: generator potential

what type of potentials are receptor/generator potentials

graded potentials whose amplitude and duration vary

how does stimulus strength affect receptor potentials?

stronger stimuli → greater permeability change → larger potential

do receptor potentials have a refractory period

no

what is the functional consequence of receptor potentials lacking a refractory period

they can summate with rapidly successive stimuli

in generator potential: what happens first when a stimulus acts on an afferent neuron ending

stimulus opens stimulus-sensitive channels → Na+ enters → receptor potential forms

in generator potential: how does the local current flow contribute to action potential generation in generator potentials

depolarization spreads to adjacent region, opens voltage-gated Na+ channels

In generator potential: what finally initiates the action potential

Na+ entry into the afferent fiber triggers an AP that self-propagates to the CNS

What happens first when a stimulus acts on a separate receptor cell

stimulus opens stimulus-sensitive channels → Na+ enters → receptor potential forms

what does the local depolarization in a receptor cell open 

voltage-gated Ca2+ channels 

what is triggered by Ca2+ entry in receptor cells

exocytosis of neurotransmitter

how do neurotransmitters stimulate the afferent neuron in receptor potentials 

they bind to chemically gated receptor channels → Na+ entry into afferent ending

what does the depolarization in the afferent fiber open

voltage-gated Na+ channels in the adjacent region

what finally initiates the AP in the receptor potentials

Na+ entry into the afferent fiber triggers an AP that self-propagates to the CNS

where is the site of initiation of an AP in an afferent neuron

peripheral terminal (free nerve ending or receptor)

in which direction does the action potential propagate in an afferent neuron

from peripheral terminal towards cell body and then into CNS

in which direction does the AP propagate in an efferent neuron 

from the axon hillock down the axon toward the effector organ

what is the difference between AP initiation in afferent vs inter/efferent neurons

Afferent neurons: AP begins at peripheral receptor terminal

Efferent neurons: AP begins at axon hillock

receptors that either adapt slowly or don’t adapt

tonic

receptors that rapidly adapt

phasic

what does modality mean in sensory physiology

the type of sensation detected

how is particular modality detected

by a specialized receptor that responds to that type of stimulus

how is information about modality transmitted to the brain

through specific afferent and ascending pathway

where does sensory information about modality ultimately excite neurons

in a defined area of the somatosensory cortex

what is the 1:1 association in somatosensory pathways called 

labelled line coding 

what ensures that the brain interprets receptor activation as a specific sensation

dedicated labeled line pathway from receptor to cortex

where do olfactory pathways from the nose project

through the olfactory bulb to the olfactory cortex

most sensory pathways project to

the thalamus

modifies and relays information to the cortical centers

thalamus

where do equilibrium pathways project primarily to

the cerebellum

what is an exception to sensory information being mapped along specific pathways

synesthesia

stimulation of one pathway automatically triggers and involuntarily triggers perceptions in another sensory modality

synesthesia 

the region of skin surface that the somatosensory neuron responds to

receptive field

a circumscribed area of the skin surrounding the point of stimulation

receptive field

the ________ the receptive field for a sense on the skin surface, the ________ the acuity

smaller, greater

two receptive fields stimulated by the two points of stimulation means 

two points are felt

only one receptive field stimulated by the two points of stimulation the same distance apart means 

one point felt

in lateral inhibition, what happens to the receptor at the site of most intense stimulation

activated to the greatest extent

in lateral inhibition, are surrounding receptors also activated during stimulation

yes but to a lesser degree

in lateral inhibition, how does the most intensely activated receptor pathway affect weaker pathways 

halts transmission of impulses in less intensely stimulated pathways

what is the main function of lateral inhibition

facilitates localization of the site of stimulation

where is the primary sensory cortex and what does it do

in the 3postcentral gyrus, handles signals coming in from thalamus

the rate of Action potentials is proportional to

the intensity of the stimulus

the variable stimulus intensity produces _______ which produces ________

variable receptor potentials, variable patterns of action potentials in the CNS

receptor potentials are graded and are proportional to_________

stimulus strength and duration

a stronger potential _________ produce a larger AP

does not

a stronger potential can induce

higher frequency firing of APs

a reduction in receptor potential despite sustained stimulation of the same magnitude

adaptation

an example of adaptation

the reduction of APs in response to continuous presence of stimulus

what does adaptation help prevent

sensory overload

what does the law of specific energies state

each receptor is most sensitive to a particular adequate stimulus