ANP 1106 Lecture Notes - Lecture 30: Lateral Geniculate Nucleus, Pupillary Light Reflex, Bulbous Corpuscle
29 Apr 2018
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ANP1106 – Somesthesia
Vision: Connections to Cortex
- Ganglion cells lateral geniculate cells of thalamus forms optic radiation
terminates on primary visual cortex of occipital lobe
- Info coming from rods and blue, green, red cones all come to the primary
visual cortex without mixing
- Visual cortex receives info from contralateral visual field
- 2 options:
o 1) Visual stimuli from ipsilateral visual field strike nasal retina
▪ Ganglion cells go through optic chiasm to contralateral lateral
geniculate nucleus
o 2) Visual stimuli from contralateral visual field strike temporal retina
▪ Ganglion cells go to ipsilateral lateral geniculate nucleus
- Ganglion cell axons between eye and optic chiasm & thalamus is the optic
tract
- Deficits
o Optic nerve – blindness in right eye
o Optic chiasm – bitemporal hemianopsia
o Optic tract – left homonymous hemianopsia
- Ganglion cells have projections towards:
o 1) Lateral geniculate nucleus of thalamus for visual perception
o 2) Suprachiasmatic nucleus of hypothalamus, takes part in
biorhythms from light and dark cycles
o 3) Superior colliculi, participates in fast movements (saccades) of eyes
towards visual stimulus
o 4) Pre-tectal nuclei, participates in pupillary light reflex
Somesthesia: Simple Receptor Types
- Simple receptors are found in:
o 1) Somatic system – detect stimuli to external body
o 2) Vegetative system – detect stimuli to internal organs
- 2 kinds of simple receptors:
o 1) Free nerve endings
▪ Non-specialized naked - detect pain, temp or pressure
▪ Merkel discs – detection of light touch
▪ Hair follicle receptors – detect movement of hair
o 2) Encapsulated dendritic endings
▪ Meissner’s corpuscles – greater density in hands, lips, nipples,
discriminative tactile function
▪ Krause corpuscles – found in mucous membranes like mouth
▪ Pacinian corpuscle – found in dermis and subcutaneous tissue
respond to changes in pressure
▪ Ruffini corpuscle – in dermis, subcutaneous tissue and
articular capsules, respond to stretching
▪ Golgi tendon organs – in tendons, respond to applied tension
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