Module 4 Flashcards
(74 cards)
What is the somatosensory system
It provides information about the body’s internal and external states and helps maintain homeostasis
What are the three types of sensory receptors?
Exteroceptive: Detect things at skin level (e.g. contact, temp)
Proprioceptive: Detect body movement (joints and limbs)
Enteroceptive: Monitor internal organ function
What are the components of the somatosensory system?
- Somatosensory receptors and neurons
- Afferent axons and neurons
- Neurons in somatosensory cortex
How is the somatosensory cortex organized?
Somatotopic (body) map, which is distorted due to receptor density
What is the pathway of sensory information?
Receptor → Sensory neuron → Spinal cord → Brain → Motor neuron → Skeletal muscle
Which horns of the spinal cord handle sensory and motor info?
Dorsal horn = Sensory input
Ventral horn = Motor output
What are the key characteristics encoded by sensory signals?
- Modality: Receptor specificity (e.g. touch vs temp)
- Intensity: Firing frequency and number of active axons
- Location: Somatotopic mapping
- Duration: AP pattern reflects stimulus start/end
What is the receptive field?
A region of skin that, when stimulated, affects a neuron’s activity. Smaller receptive fields allow finer discrimination (e.g. fingertips)
How does receptive field relative size relate to discrimination?
Smaller fields = better two-point discrimination
Larger fields = less spatial precision
What are the main pathways for somatosensory information to reach the brain?
- Dorsal columns: Touch and proprioception
- Spinothalamic tract: Pain and temperature
- Spinocerebellar tract: Proprioceptive feedback to cerebellum
What wavelength range does visible light cover in the spectrum?
400-750 nm
Name the two main types of components in the eye
Optical components (focus light) and Neural components (detect/transmit visual info)
What structure of the eye controls pupil size?
Iris
What is the function of the cornea?
Initial focusing of light entering the eye
What role do ciliary play in vision?
Change the lens shape to adjust focus (ask what this is known as - accommodation)
Describe the path of light through the eye before phototransduction begins
Cornea → aqueous humor → pupil → lens → vitreous humor → retina
What changes occur in the lens during accommodation?
Lens becomes rounder for near focus (contracted ciliary muscles) and flatter for distant focus (relaxed muscles).
What are the three components of the near response?
Accommodation, Pupil constriction and eye convergence
What optical defect causes myopia and how is it corrected?
Light focusses in front of the retina, corrected with concave lens
What are the three retinal layers from back to front?
Photoreceptors, interneurons and ganglion cells
What happens to photoreceptors in the dark during phototransduction?
Retinal inactive → cGMP-gated channels open → Na+/Ca2+ influx depolarizes photoreceptor → glutamate released continuously
How do rods and cones differ in number and function?
- Rods (~120 million) for night vision, no colour (scotopic)
- Cones (~8 million) for daylight vision and colour (photopic)
Which cone types correspond to which colours?
- S-cones = blue
- M-cones = green
- L-cones = red
What are ON-centre and OFF-centre ganglion cells responsible for?
ON-centre activated by light in center, OFF-centre activated by light in surround, both enhance contrast and edge detection.