Sensory Nervous System Flashcards
sensory nervous system
branch of afferent peripheral nervous system (somatic and visceral nervous system)
afferent pathway
starts when an internal or external sense is detected by sensory receptors adapted to detect specific senses (touch, hearing, light, hunger)
conscious senses
general and special senses
general sense
visceral sensations (hunger), touch, temp, pain, proprioception (location of body/limbs in space)
special senses
taste, smell, hearing, equilibrium, vision
subconscious senses
outside of animals awareness (muscle length, muscle tension (baroreceptors), several visceral stimuli to maintain homeostasis (BP and temp))
hypothermia steps
1) activation of a sensory receptor at skin (afferent nerve) and the action potential is sent to the thalamus and hypothalamus in the brain. Internal body temp can also be detected directly at the hypothalamus
2) hypothalamus (CNS) integrates the signal to determine what physiological change needs to occur to increase body. Action potential sent through efferent nerves to arteries in the skin, muscles, and thyroid gland
3) arteries constrict to reduce heat loss and skeletal muscles contract; shivering
4) body temp is increasing back to normal levels, increase in temperature detected by hypothalamus; shuts off signal
hyperthermia steps
1) activation of a sensory receptor at the skin (afferent nerve) and action potential is sent to the hypothalamus
2) thalamus and hypothalamus (CNS) integrates the signal to determine that physiological changes need to occur to lower body temp. Action potential sent through efferent nerves to the arteries in the skin, sweat gland, thyroid gland
3) arteries dilate to increase heat loss and increase secretions of the sweat glands
4) body temp decreases back to normal levels (detected by hypothalamus to shut off response)
olfactory sense pathway
detection of different smells in the environment
vomeronasal organ
chemoreceptor organ
auditory sense pathway
conversion of sound waves to a mechanical force (fluid flow) in the inner ear that activates auditory nerves and transmit signals to integrating regions in the brain
pinna
external ear, sound directed into the ear through here and the ear canal. funnels and collects sound wave vibrations and directs them to the eardrum (tympanic membrane), where they move 3 bones (ossicles) in the middle ear (malleus, incus, stapes)
middle ear
transmits/amplifies vibrations, cause fluid flow in the inner ear (cochlea) that activates hair cell receptors and the auditory nerve (CN 8)
inner ear
has hair cell receptors that convert mechanical vibrations into nerve impulses. important for hearing and equilibrium
organ of corti
hair cells that are receptor cells for hearing with modified dendrites on the surface. tectorial membrane lies on top of the hair cells and vibrates. hair cells send action potential to the cochlear nerve (8) to the midbrain to the thalamus and auditory cortex
equilibrium
maintenance of balance, mechanical receptors help maintain balance
vestibular system
parts of the inner ear and eye, neurons in vestibular nuclei project their axons into the brain
vestibulo-ocular reflex
compensates for head and body movements by stabilizing images on the retina and projecting images to the thalamus
vestibular disease
dizziness, imbalance, vertigo, tinnitus (ear ringing), hearing loss, brain fog, visual impairment, etc
vision
photoreceptor activation in retina –> activates optic nerve –> transmits action potential to integrating regions in the brain (thalamus and visual cortex)
sclera
outer connective tissue layer
choroid
blood vessels
cornea and pupil
opening for light
lens
help direct and control amount of light that reaches the retina by constricting muscles around iris
2 types of photoreceptors
rods and cones, merge at optic disc at back of eye
rods
light
cones
color
tapedum lucidum
part of choroid membrane. back of eye, reflects light back to retina to amplify amount of light reaching photoreceptors (helps night vision, causes eye to ‘glow’ in the dark)
formation of a visual image steps
eye –> oculomotor nerve –> optic tract –> brain –> thalamus (most sensory tracts that reach cerebral cortex expect olfactory) –> primary visual cortex.
Nociceptor steps
1) transduction - conversion of painful stimulus into action potential at end of sensory receptor
2) transmission - conduction of action potential to spinal cord
3) modulation - changes to sensory nerve impulses in the spinal cord (amplification or suppression due to amount of pain). primary target for pain management
4) perception - conscious awareness of pain in the brain, fear centers interact here
gustatory senses
chemical receptors in taste buds, humans - sweet, sour, salty, bitter. Flavor testing important for food companies
