Sensory system Flashcards
list the 5 components to the reflex arc
Receptor on skin
afferent neurone (sensory neurone)
integration centre (CNS)
Efferent neurone (motor neurone)
Effector organ/muscle response
what stimuli different receptors respond to
Mechanoreceptors - touch
chemoreceptors - pH
photoreceptors - light
thermoreceptors - temp
nociceptors - pain
baroreceptors - changes in pressure
what is a sensory unit
a single afferent neuron and all its receptor endings
types of sensory receptors
neuron with free nerve endings
neuron with encapsulated ending
specialised receptor cells closely associated with neuron
How sensory signals are generated
Environmental changes cause membrane potential in receptor to change.
Receptor becomes graded and reaches threshold –> action potential generated.
Information goes to the brain via afferent nerve fibres.
The stronger the stimulus, the larger the graded receptor potential, the more frequent action potentials are fired, more neurotransmitter is released.
How motor pathways take the message to the spinal cord and muscles
2 neurons which synapse with each other in the spinal cord cross the midline
there is an upper and lower neurone
terminate at the neuromuscular junction with skeletal muscle
How ascending sensory pathways work
Responsible for fine touch,vibration,position,temp,pain
Made of 3 neurones which synapse in the spinal cord and thalamus, cross the midline in the CNS
terminate in the somatosensory cortex
what are the systems involved for the special senses?
pressure + warmth + vibration +limb position= somatosensory system
sight=visual system
hearing=auditory system
taste=gustatory system
smell=olfactory system
describe the three tissue layers of the eye wall
Outer - Fibrous layer made of the sclera and cornea
Vascular layer:
Choroid- dark melanin containing cells which absorb light
ciliary body - ciliary muscles which change thickness of lens
Iris-coloured part and light passes through pupil
Inner most layer (nervous tissue layer):
Retina - prevents light reflection
what are the cells called which contain melanin
melanocytes
what three main types of neurones are within the sensory layer of the retina?
photoreceptors e.g. rods and cones
bipolar cells
ganglion cells
how does light pass through the eye
through the components of the anterior cavity and is focused by lens and passes through vitreous humor
Past between axons, ganglion cells and bipolar cells, to photoreceptors next to pigmented layer
Direction of travel of neuronal signal in eye
photoreceptor cells synapse with bipolar cells which synapse with ganglion cells
ganglion cells axons run to the posterior of the eye to form optical nerve
differences between rod and cone cells
Rod are more sensitive to light and only black and white
Cone are for colour vision and have blue,red and green light cones
Describe photo transduction
-Retina takes light energy and converts it to electrical
-rods operate in dim light
-Rhodopsin is the protein opsin bound to pigment retinal
-light causes retinal change shape and splitting
- This stimulates the rods, resulting in vision
-generates receptor potential
-ATP required for retinal and opsin to bind back to rhodopsin.
parts of the outer ear
Pinna
external auditory canal
parts of middle ear (ossicles)
Tympanic membrane
Malleus (hammer)
Incus (anvil)
Stapes (stirrup)
Parts of Inner ear (Labyrinth)
Mechanoreceptors for hearing and balance
Vestibular apparatus
Semi-circular canals
Cochlea
How the middle ear operates
-air filled
-oval and round window connect to inner ear
-tympanic membrane causes ossicles in air filled middle ear to move:
Hammer, anvil and stirrup form a lever system
Amplification and transmission of vibratory motion from the tympanic membrane occur –> to fluids in the inner ear cochlea via oval window
auditory canal to pharynx opens
which parts of the inner ear are responsible to balance
Vestibule and semi circular canals filled with perilymph and endolymph fluids
describe structure and function of cochlea
snail shell shape with 2 canals
contains specialised sensory hair cells stereocilia on the basilar membrane
Basilar membrane moves when waves in perilymph move over it
when stereocilia bend receptor depolarises and receptor potential is generated
sound transmission through the ear summary
-sound waves vibrate TM
-auditory ossicles vibrate –> amplification
-stapes connected to oval window send vibration to cochlea
-pressure waves push basilar membrane and energy waves dissipate at round window
-hair cells bend –> transmit signal
-neurotransmitter released activates sensory neurones and action potential sent to the brain
how is equilibrium controlled in the inner ear?
Vestibular apparatus contain hair cells where tips are embedded in gelatinous mass weighed down by otoliths. Otoliths move in relation to gravity, when hairs bend depolarisation of receptor cells send action potential to brain about head position
Semi circular canals (3 at right angles)
-ampula that float in endolymph
endolymph moves in opposite directions
-cupula and stereocilia on hair cells bend –> action potential
-vestibulocochlear nerve to cerebellum
