week 5 Flashcards
is perception concerned with the efferent of afferent branch of the nervous system?
afferent (periphery to CNS)
special senses (5)
vision
hearing
taste
smell
balance/equilibrium
law of specific nerve energies?
given sensory receptor is specific for each modality
T of F: modalities other than the adequate stimulus may activate receptors
true, but only at relatively high energy levels
what are the characteristics of sensory transduction? (3)
- triggered by sensory stimuli
- graded potentials (“receptor/generator” potentials) [if exceeds threshold, can generate AP]
- opening/closing of ion channels
describe the structure and function of sensory receptors
- sensory receptor responds to stimulus
- changes MP and opens Ca2+ channels, triggering release of neurotransmitters
- would eventually produce AP and carry msg to CNS
diff bw slowly and rapidly adapting receptors?
a) slowly adapting: receptor potential decays slowly during stimulus; always SOME receptor potential. interested in overall magnitude of stimulus.
b) rapidly adapting: receptor potential is elicited by change in stimulus energy. interested in stimulus velocity. decays quickly and nothing happens if stimulus is constant.
what are labelled lines?
specific neural pathways transmitting information of a specific modality
2 types of coding for stimulus intensity?
- frequency coding: frequency of APs
- population coding: # of receptors activated
examples of rapidly and slowly adapting mechanoreceptors?
rapidly adapting:
a) pacinian corpuscle (deep vibration/pressure)
b) meissner’s corpuscle (light touches)
c) hair follicle receptor
slowly adapting:
a) free nerve endings
b) merkel’s disk (superficial pressure)
c) ruffini’s ending (deep pressure)
whats a free nerve ending?
somatosensory receptor types that lacks identifiable specialized structures
warm vs cold receptors?
warm receptors:
- free nerve endings
- respond to temps in range of 30–43°C
- increased frequency with increase in temperature
cold receptors:
- possible free nerve endings
- respond to temps in range of 35–20°C
- increased frequency with decrease in temperature
classes of nociceptors? (3)
- mechanical
- thermal (respond to 44°C+)
- polymodal
a) what somesthetic sensations does the dorsal column–medial lemniscal pathway include?
b) how?
a) touch and pressure, proprioception
b) (1) proprioceptors/mechanoreceptors to spinal cord TO (2) medulla (crosses over) TO (3) thalamus to somatosensory cortex
a) what somesthetic sensations does the spinothalamic tract include?
b) how?
a) pain, temperature
b) (1) nociceptors/thermoreceptors TO (2) spinal cord (crosses midline) (3) thalamus to cortex
chemicals that activate nociceptors? (5)
Potassium
Histamine
Prostaglandins
Bradykinin
Serotonin
diff bw fast pain and slow pain? (3 each)
fast:
1. A-delta fibers (thin, lightly myelinated axons)
2. sharp/pricking
3. easily located
slow:
1. C fibers (thin, unmyelinated axons)
2. dull aching
3. poorly localized
gate-control theory of pain?
- somatic signals of non-painful sources can inhibit signals of pain.
- certain neurons inhibit the second-order neurons that transmit pain info.
- ex rubbing a painful area
describe anatomy of outermost eye (2)
- sclera (white part)
- cornea (transparent, allows light to enter)
describe anatomy of middle eye (3)
- ciliary body (helps focus)
- iris (colour part, in front of lens)
- choroid (beneath sclera and contains blood vessels that nourish inner layer of the eye/photoreceptors)
describe anatomy of innermost eye (1)
- retina (where photoreceptors are)
parts of retina (3)
- fovea: central region of retina, where light from center of visual field strikes (no blood vessels/high density of photoreceptors here)
- blood vessels
- optic disk: “blind spot” where blood vessels/axons enter and exit (no photoreceptors here)
what is accommodation?
lens curvature which enables the eye to focus on objects
is there more curvature of the lens when the object is near or distant?
near
describe the mechanisms of accommodation for viewing distant objects
- ciliary muscles relax
- zonular fibers become tight
- lens becomes larger
describe the mechanisms of accommodation for viewing near objects
- ciliary muscles contract
- zonular fibers become loose
- lens becomes smaller/rounder