PNS Afferent

PNS system consists of anything _____

outside the brain and spinal cord

What are 3 specific things in our PNS?

- sensory receptors

- peripheral nerves and associated ganglia

- motor endings (axons terminals)

What are nerves in the PNS, and what are ganglia?

Nerves are bundles of axons in PNS

Ganglia are collections of cell bodies in PNS

what do sensory mechanisms do?

many sensory mechanisms provide brain with info regarding internal and external environment (what happens inside or outside of us?)

survival depends upon ____________ and ______________

sensation and perception

What is sensation?

sensation is awareness, being aware of a stimulus(change) in our internal or external environment

What is perception?

when your brain brain/cortex can provide a meaning/interpretation of the stimuli(change)

What are the 3 basic levels that allow us to have awareness then perception? (neural integration in sensory neurons)

1. receptor levels

2. circuit level

3. perceptual level

describe the receptor level of neural integration

we need to have sensory receptors that pick up on stimuli, then we go through transduction which is when we take a stimuli and convert it to a language our body understands to generate a graded potential

describe the circuit level of neural integration

this is summating GP's, the AP is traveling down the axon of neurons, we are transmitting stimulus to our brain to give an AP a meaning

describe the perceptual level of neural integration

info gets processed to brain in cortical sensory areas which allows us to be AWARE

CNS interprets info based on _______ and ________

origin and frequency

Action Potentials get transmitted to specific ________

to specific brain regions/parts of our brain

visual stimuli travel via _________ _________ directly to brain areas associated with ________. All info traveling through neurons is interpreted as light.

- via sensory neurons

- associated w/ vision

stronger stimuli activate more receptors and trigger what?

trigger a greater frequency of impulses in sensory neurons

can the magnitude of action potentials be affected?

no, not even an intense touch can affect the magnitude of action potentials because they're ALL or NOTHING

Activation of a sensory pathway at any point gives rise to the same situation that would be produced by ....

by stimulation of receptors in the body part itself

What is phantom pain?

pain experienced in the area of a body part that has been amputated. Brain perceives pain but the stimulus isn't there

can we stimulate sensory pathways for phantom pain when a stimulus is not there?

yes we can stimulate sensory pathways for phantom pain when a stimulus is not there

Acuity is...

how accurate we are at being able to distinguish different stimuli

Acuity is influenced by

receptive field size, which is an area on your body that a receptor is responsible for, this are on the skin will trigger a receptor if touched

size of field varies ____________ with density of receptors in region

inversely

the smaller the part of your body the receptor is responsible for, then ....

then the more accurate you will be in determining where that receptor is

the smaller the receptive field, the _________ its acuity

bigger/better

the higher the density, aka more receptors firing on your body, then

the more accurate you'll be because more receptors give us more information (higher acuity)

large receptive field may be perceived as one point, and small receptive field perceived as _______ __________

two points

what is receptor adaptation?

Receptors stop responding to a continuously present stimuli, such as clothes, jewelry, less excitable cells bc they adapt and ignore unimportant stimuli

we can classify receptors based on

1. stimulus type

2. location

3. structural complexity

what are the stimulus types?

mechanoreceptors, thermoreceptors, photoreceptors, chemoreceptors, nociceptors

describe mechanoreceptors and thermoreceptors

mechanoreceptors: touch, pressure, vibration, stretch, itch

thermoreceptors: changes in temperature

describe photoreceptors and chemoreceptors

photoreceptors: light energy aka in retina photons

chemoreceptors: chemicals, info on olfaction smell, taste

describe what nociceptors are

these are pain causing stimuli, such as extreme heat/cold, heavy pressure, can fire at the extreme of other receptors

ex: slap in the face = mechanoreceptor nociceptors

ex: touch hot stove = thermoreceptor nociceptor

what are the TWO locations we can classify receptors?

SOMATIC = skin, muscles, joints, tendons, GI Tract , body movement, pressure, touch, pain, temp

SPECIAL = special senses of taste, hearing, smell, balance, vision

the post central gyrus or primary somatosensory cortex is _______ oriented

sensory oriented

What are proprioceptors?

mechanoreceptors BUT they give us info of voluntary movement like walking, they're critical to everyday movement and found in skeletal muscle, tendons, joints

proprio/mechano receptors respond to changes in _______ _______, _______ ________, and joint position

muscle length, tendon tension, and joint position

purpose of muscle contraction is to move the bones for mobility, but if you contract the muscle,

well the muscle is connected to the tendon, which is connected to the bone, so contracting muscle means the tendon will undergo tension.

what do we use a lot in reflexes?

we use a lot of muscle spindles

what are the 2 categories of reflexes?

- inborn/intrinsic: a reflex already there, born w/ it, tested on babies

- learned: result from practice or repetition

describe the general reflex arc

1. we get a painful stimulus picked up by fired nociceptor

2. sensory neuron takes info to the CNS to the dorsal spinal cord

3. we have a synapse (interneuron in some cases)

4. we have an efferent outgoing output to the effector which happens to be the muscle

5. then the response is flexion bc reflexes are protective

proprioception is essential for

smooth coordinated movements

muscle spindles do what?

they give our brain info of changes of length in muscle (stretch reflexes)

Golgi tendon organs do what?

give us info about tension in muscle and tendons

stretch reflexes maintain _________ _________ in large postural muscles. This is important for __________ _______ ________ in large muscles.

- muscle tone

- balance and stability

a stretch which is an increase in muscle length, causes muscle contractor. What does this mean?

this means you quickly stretch a muscle, and then you have a contraction of the same muscle

if you hit your knee, it jerks up and triggers what?

it triggers muscle spindles to contract

all stretch reflexes are _____ and _____

monosynaptic and ipsilateral

monosynaptic means

one synapse - one afferent neuron communicating w/ efferent motor neuron

Ipsilateral means

on the same side of the body

are tendons connected to muscles?

yes they're connected

reflexes are largely ___________

protective

What do polysynaptic (many synapses) reflexes do?

protect or inhibit muscles from damage/too much tension

- important for coordination of movements

The length of a muscle is communicated to the brain via a __________

muscle spindle b/c they detect length signals

Describe reciprocal inhibition

when we inhibit the opposite muscle from contracting b/c that is dangerous, associated with stretch knee reflex

describe reciprocal activation

when we activate or contract the antagonist/opposite muscle to relax the primary muscle, such as in golgi tendon organ reflex

what are the five special senses?

- taste

- smell

- hearing

- balance

- vision

which cranial nerves have to do with taste?

Facial VII (7)

Glossopharyngeal IX (9)

Vagus X (10)

what cranial nerve is for hearing and or balance?

VIII (8) Vestibulocochlear

what cranial nerve is for vision?

II (2) Optic nerve

what cranial nerve is for smell?

I (1) Olfactory

Taste buds are mostly on papillae of tongues, but they are clusters of ....

clusters of 25 taste cells and 25 supporting cells

taste buds convert chemical signals from foods/drinks dissolved in their saliva to what?

taste buds convert these to action potentials

Taste hairs contain chemoreceptors that are specific for specific chemicals or tastants, what binds to them?

chemicals bind to the chemoreceptors

T OR F

taste hairs, are on taste cells, which are on taste buds

TRUE

most taste receptors are located on tongue. Taste receptors and their associated sensory neurons respond to which tastes?

sweet sour salty bitter savory (umami)

gustatory pathway

1. tastants bind to chemo receptor causing AP to go to brain

2. CN VII, IX, X carry impulses from taste buds to medulla

3. then to thalamus

4. gustatory cortex in insula processes the taste

5.hypothalamus + limic system like or dislike food and hippocampus makes memory of that

what can enhance or detract from taste?

temperature and texture

for smell:: there are olfactory chemoreceptors for more than _____ different odorants.

1,000

in nose: Odorants dissolve in the mucus and bind to chemoreceptors on __________ ________. Olfactory receptor cells then generate an ___________.

- olfactory hairs

- impulse

describe smell process slightly

1. Odorants dissolve in mucus layer, and bind to chemoreceptors on olfactory hairs (which is right above the mucus layer)

2. Those olfactory receptor cells generate AP/impulse and carry that upwards through CN I Olfactory

3. The Olfactory CN synapses with olfactory bulb at the roof of the nose

4. Impulse is sent to olfactory areas in frontal and temporal parts of brain to be processed

In detection of smell, odorants themselves:

bind to receptors and stimulate opening of ion channels

the formation of a rainbow reflects...

visible light and how it consists of many wavelengths

what is photoreception?

this is when the eye detects a visual stimulus by converting light energy to nerve impulses and transmitting them to the brain

what is the pathway of light through the eye?

Light enters and → hits the cornea + refracts → light travels through aqueous humor → light enters the pupil and falls on the lens → travels through vitreous humor → light hits retina → retina translates light as a photo

photoreceptors have rods and cones, what is their difference?

rods work in dim light and cones work in bright lights. Colorblindness is due to lack of 1 or more cone cell types

how does retina convert light into AP?

1. Rods + Cones synapse w/ bipolar neurons to slightly process and integrate info

2. Bipolar neurons synapse with ganglion cells (axons of the ganglion is the optic nerve)

3. AP's travel down ganglion cell axons and exit retina through optic nerve

4. At optic chiasm half fibers from each eye cross over to contralateral side and continue via optic tracts

5. Light signal is sent to thalamus, then to primary visual cortex in occipital lobe

describe light adaption

* going into bright light after being in dimness/darkness

- Occurs b/c immense pigments are broken which produces a glare

- Pupils constrict, and change sensitivity allows our cones to take over

- Visual acuity improves in 5-10mins

Describe dark adaptation

* going into darkness/dimness after being in bright light

- Cones stop functioning in low light so pupils dilate

- Build up of pigment (rhodopsin) accumulates

- Retinal sensitivity increases in 20-30mins

sound intensity is the physical property of sound, whereas loudness is the ......

loudness is the interpretation of sound

both _________ and _________ are related to amplitude of sound wave

intensity and loudness

for hearing, sound waves travel through ear, activating ____________ sensitive ____________ deep in ear. Vibration causes impulses to travel to ______ to be _________

- activating vibration sensitive mechanoreceptors

- travel to brain to be interpreted

describe conduction deafness

blocked sound conduction, can be due to ear wax, scarred ossicles, think cotton swab story

sensorineural deafness

A permanent lack of hearing caused by damage of the inner ear.