interoception

ascending pathway

carry sensory information from the body up to the brain such as pain, touch, temperature.

interception starts with 

interoceptive signals originating from within an animal/person

descending pathway

carry motor commands from the brain down to the spinal cord to control movement

3 major types of interoceptive signals

biochemical signals, mechanical forces, thermal and electromagnetic signals

biochemical signals

simple ions - acidity (acid) also more complex inorganics molecules

• such as acidic ions, to organic molecules and small peptides

mechanical forces

alter physical structures such as cellular shape through stretch or tissue extensive [ lungs expanding when you breathe or Blatter filling up tissue ]

[pressure]

thermal and electromagnetic signals 

internal temperature changes , energy transmission ; delivered in various wave frequencies across the electromagnetic spectrum

revised description of interoception

the bidirectional signal processing between the brain and internal organs that generates a representation of the new internal state of an animal/person

interoceptors

molecular sensors or receptors in neurons that catch/detect these signals and turn them into something; the systems in our body [nervous , CNS , etc] can understand an electrical, hormonal/ other non-neural signal to be interpreted by the brain

interoceptors include

chemoreceptors [for chemicals], humoral receptors [ detect body fluids] , specialized mechanoreceptors [stretch & pressure ] , free nerve endings [involved in pain ]

signals generate by 

a interoceptor 

interoceptor location determines whether

the signal can be transmitted through the peripheral neural system or a non-neural system.

body talking to the brain: 2 major pathways - neural route

cranial and vagus pathways , both neural routes : carry signals from internal organs [stomach, lungs, heart] up towards the brain stem [fast & direct] in an area called - nucleus tractus solitarii [NTS]

parasympathetic afferents 

sensory nerve fibers that carry messages from the bodys organs back to the brain; body whispering its inner state to the brain  

• travel mostly through the vagus nerve, brining signals about heartbeats, breathing, gut stretch

• purpose - to let the brain ‘feel the inside’ - the calm, slow side of bodily state so we can regulate stress, digestion, & emotions

routes for interoceptive signals

• neural route = nerves [PNS] : signals from organs carried by afferent nerves [ like the vagus nerve] to the brainstem

• non - neural route (circulatory / lymphatic] : signals carried by chemical messengers in the blood or lymph reach receptors inside brain

mechanical/thermal interoceptors

plug into wires (nerves)

• the receptors have built in nerve connections = direct / fast transmission

chemical interoceptors

travel by mail (blood/lymph)

• the chemicals need to reach the brain itself ! slower, indirect detection

in the revised description, what are the 4 processes included in interoception

includes the proceses by which an organism senses, interprets, integrates, & regulates signals from within itself

in interoception, what does sensing mean & through which pathways does it travel to the CNS

the body is sending signals from organs/systems up to the CNS through ascending pathways.

the action of ‘regulating’ is communication from

the brain to other physiological systems via descending pathways

this major organ is primarily responsible for interpreting & integrating interoceptive signals into a representation of the internal world

the brain, a key part of the central nervous system (CNS)

besides the peripheral & central nervous systems, what three other systems are involved in processing signals about the internal environment

the vascular , endocrine , and immune systems

the three major categories of interoceptive signals that originate from within an organism 

biochemical signals, mechanical forces, & thermal / electromagnetic signals 

the term for the molecular sensors or receptors in neuron that directly detect interoceptive signals & transduce them

interoceptors

the two major ascending peripheral neural pathways that transmit interoceptive signals to the CNS

the cranial / vagal pathways & the spinal nerve pathway

sensory ganglia in the cranial / vagal pathway (nodose & jugular ganglia) project to which brainstem structure 

to the nucleus tractus solitarius (NTS)

visceral afferent that travel along cranial nerves including the vagus, are also referred to as

parasympathetic afferents

visceral afferents that travel through the dorsal column of the spinal cord are often called

sympathetic afferents

vagal afferents are hypothesized to primarily carry what two types of signals 

mechanoreceptor and chemosensory signals 

spinal afferents are hypothesized to carry signals related to what three sensations

temperature, pain , and tissue injury

the three subcortical brain structures where interoceptive information is often first processed

the medial nucleus tractus solitarii (NTS), the parabriachial nucleus (PB), and the ventromedial nucleus of the thalamus

from subcortical structures, neurons processing interoceptive signals may project to

higher brain regions including the hypothalamus three cortical areas: the insulation, anterior cingulate cortex, & somatosensory cortex 

the brain regions which emerged early as a crucial cortical node in the interoceptive system

the insula

primary interoceptive information is relayed from the ventromedial nucleus of the thalamus to

the posterior insula

the blank insular cortex is most strongly connected to paralimbic cortical regions like the OFC