CNS/Sensory Flashcards
Afferent
Sensory input
Cell bodies out of CNS
Efferent
Motor output
Cell bodies in CNS
Cranial Nerves
Somatic, Visual, olfactory, taste, auditory, vestibular
Spinal Nerves
Somatic sensation
- touch
- temperature
- pain
innervates skeletal muscle only excitatory (ACH)
Somatic efferent
Autonomic efferent
innervates interneurons
smooth & cardiac muscle
excitatory & inhibitory
Enteric Nervous system
Steps of Nervous System development
- Fertilized egg (ovum)
- Ball of cells
- Blastocyst (week 1)
- Blastocyst (week 2)
- Blastocyst (week 3)
- Week 3
Week 1 Blastocyst develops
inner cell mass
Week 3 Blastocyst develops
embryonic disk
neural plate
Ectoderm
Outermost layer
Mesoderm
middle layer
Endoderm
Inner Layer
the 3 layers (ectoderm….) make up the _______
embryonic disk
Neural groove
a shallow median groove of the neural plate between the neural folds of an embryo
What develops in week 4 of the neural tube
vesicles
Neural Crest becomes part of CNS or PNS
PNS
Neural tube becomes “CNS or PNS or both*
CNS and part of PNS
Neural Tube is composed of
Forebrain, Midbrain, Hindbrain
Forebrain becomes
Cerebal hemispheres and Thalamus
Midbrain becomes
Midbrain
Hindbrain becomes
Cerebellum, pons, medulla
Rest of Neural tube becomes
Spinal cord
Cavity becomes
the ventricles and central canal
What do ventricles contain
150 ml of cerebral spinal fluid (CSF)
Cerebrospinal spinal fluid
- produced by the
- rate of production
Produced by the choroid plexus (in the four ventricles, but mainly the two lateral)
at a rate of 500 ml/day.
Cerebrospinal spinal fluid function
1) Supports and cushions the CNS. Specific gravity of CSF and the brain are equal.
2) Provides nourishment to the brain.
3) Removes metabolic waste through
absorption at the arachnoid villi.
Cerebrospinal spinal fluid composition
Sterile, colorless, acellular fluid that contains glucose.
Cerebrospinal spinal fluid circulation (active or passive)
passive (not pumped)
Where does CSF enter?
The subarachnoid space
an abnormal buildup of fluid in the ventricles (cavities) deep within the brain
Hydrocephalus
Communicating Hydrocephalus
The flow of CSF is blocked after it exits the ventricles
Noncommunicating Hydrocephalus
The flow of (CSF) is blocked along one or more of the narrow passages connecting the ventricles.
Meninges cover the
brain and spinal cord
Three membranes of CNS
Pia matter, arachnoid membrane, Dura mater
CSF returns to the blood at the
dural sinus
The only substate metabolized by the brain
Glucose
T/F: There is a lot of glycogen in the brain
F: Very little glycogen in the brain.
What does the brain need continuous supply of? (2)
glucose and oxygen
Glucose transport into the brain does not require ____
insulin
A few seconds of blood supply interruption can lead to
loss of consciousness
A few minutes of blood supply interruption can lead to
neuronal death (stroke)
Brain receives ___ % of total blood
15%
Brain is __% of total mass
2
Function of circle of willis
safety factor
CSF moves from the heart through ………… then back to the heart
Chorioid plexus ventricles subarachnoid space archnoid villi dural sinus venous system
Blood can move from the heart either through … arteries
….. arteries move straight to the circle of willis
….. arteries move through the basilar artery to the circle of Willis
vertebral arteries
carotid arteries
carotid arteries
vertebral arteries
Blood-brain barrier
capillary wall
astrocytes (glia) functions (4)
- provide strucutral support
- induce tight juctions
- glutamate K+
- phagocytosis of debris
Awareness of sensory stimulation
Sensation
The understanding of a sensation’s meaning
Perception
T/F: We perceive energy of a sensory stimulus directly
F: We do not perceive the “energy” of a sensory stimulus directly.
T/F: We only perceive the neural activity that is produced by sensory stimulation.
T: We only perceive the neural activity that is produced by sensory stimulation.
Law of specific nerve energies:
Regardless of how a sensory receptor is activated, the sensation felt corresponds to that of which the receptor is specialized.
Law of projection:
Regardless of where in the brain you stimulate a sensory pathway, the sensation is always felt at the sensory receptors location.
(Law of specific nerve energies/projection):
Rub your eyes hard and you will see light.
Law of specific nerve energies
(Law of specific nerve energies/projection): Penfield electrically stimulated somatic sensory cortex and patients perceived somatic sensation in the body.
Law of projection:
(Law of specific nerve energies/projection): Phantom limb pain after amputation.
Law of projection:
6 sensory systems:
Visual, Auditory, Vestibular, Somatosensory, Gustatory, Olfactory
Modality of visual
Vision
Modality of Auditory
Hearing
Modality of Vestibular
Balance
Modality of Somatosensory
Somatic Senses
Modality of Gustatory
Taste
Modality of Olfactory
Smell
Vision stimulates
B/W, colour
4 Somatic Senses
Touch
Pain
Proprioception
Thermal
Taste stimulates
"BUSSS" Bitter Umani Sweet Sour Salt
Stimulus Energy of Visual sensory system
Light
Stimulus Energy of Auditory sensory system
Sound
Stimulus Energy of Vestibular sensory system
Gravity, Acceleration
Stimulus Energy of Somatosensory system
Mechnical, thermal, chemical
Stimulus Energy of Gustatory sensory system
Chemical
Stimulus Energy of Olfactory sensory system
Chemical
Receptor class of Visual sensory system
Photorecptors
Receptor class of Auditory sensory system
Mechanoreceptors
Receptor class of Vestibular sensory system
Mechanoreceptors
Receptor class of Somatosensory system
Mechanoreceptors
Chemoreceptors
Thermoreceptors
Nociceptors
Receptor class of Gustatory sensory system
Chemoreceptors
Receptor class of Olfactory sensory system
Chemoreceptors
Which of sensory systems use photoreceptors?
Visual
Which of sensory systems use mechanoreceptors?
Auditory
Vestibular
Somatosensory
Which of sensory systems use chemoreceptors?
Somatosensory
Gustatory
Olfactory
Which of sensory systems use thermoreceptors?
Somatosensory
Which of sensory systems use nociceptors?
Somatosensory
Modaility
General class of a stimulus
The brain “knows” the modality and location of every sensory afferent.
Labelled Line
Steps of sensory receptors (5)
- Stimulus energy
- receptor membrane
- transduction
- ion channel activation
- afferent
For stimulus energy there must be
adequate stimulus (specificity)
Stimulus energy is converted into
afferent activiity
Steps of stimulus energy being converted into afferent activity (5)
- Stimulus energy
- receptor potential
- action potentials
- propagation of action potentials
- release of neurotransmitters
Magnitude of receptor potential
determines the frequency with which action potentials are generated
Non-adapting afferent response
Encodes stimulus intensity and slow changes
Slowly adapting afferent response
Some stimulus intensity and moderate stimulus changes
Rapidly adapting afferent response
Fast stimulus changes
Afferent adaption allows us to be
sensitive to changes in sensory input
Receptive field
The region in space that activates a sensory receptor or neuron
stimuilus location
Overlapping RFs produce a
population code
Acuity
ability to differentiate one stimulus from another
High/Low acuity location: Lips
High
High/Low acuity location: Back
Low
High/Low acuity location: Hands
High
High/Low acuity location: Face
High
High/Low acuity location: Lips
High
High/Low acuity location: Thigh
Low
High/Low acuity location: Shoulder
Low
Small RF means ____ acuity
High
Large RF means ____ acuity
Low
Lateral Inhibition
- Sharpens sensory acuity
- Process by which stimulated neurons inhibit the activity of nearby neurons by interneurons
neurons that carry signals from the spinal cord to the thalamus
2nd order
Interneurons
Found only in CNS
It also connects to other interneurons, allowing them to communicate with one another.
Descending pathways modulate (not motor)
sensory inputs
Sensory information is shaped by two types of mechanisms:
“bottom up” and “top down” mechanisms
Mechanoreceptors with specialized end organs that surround the nerve terminal.
These end organs allow only selective mechanical information to activate the nerve terminal.
Touch
Fluid-filled structure enclosing the nerve
terminal. Rapidly adapting. Light stroking and fluttering.
Meissner’s corpuscle
Slowly adapting. Pressure and texture.
Merkel disk
Merkel disk, Meissner’s corpuscle are examples of
Superficial layers receptors
Pacinian corpuscle, Ruffini endings are examples of ….
Deep layers receptors
Large concentric capsules of connective tissue
surround the nerve terminal. Rapidly adapting. Strong vibrations.
Pacinian corpuscle
Nerve endings wrap around a spindle-like structure. Slowly adapting. Stretch and bending of the skin (shape of an object).
Ruffini endings
Muscle spindles provide sense of static position and movement of limbs and body.
Proprioception
Stretching the cytoskeletal strands activates
Mechanoreceptors
Thermoreceptors are free nerve endings containing ion channels that respond to different temperature ranges.
Temperature
Temperature of cold afferents
0 – 35 Celcius
Temperature of warm afferents
30 – 50 Celcius
cold afferents can be activated by
menthol
warm afferents can be activated by
capsaicin and ethanol
Extreme temperatures activate
pain receptors
Nociceptors are free nerve endings containing ion channels that open in response to intense mechanical deformation, excessive temperature, or chemicals.
Pain
T/F: Pain afferents are highly modulated
T: Pain afferents are highly modulated (enhanced and suppressed).
Visceral pain receptors are activated by
inflamation
Nociceptors are enhanced by many
mediators
Steps leading to Hyperalgesia
- cut occurs
- action potential
- susbatnce P released in spinal cord
- pain
- enhancement of surrounding nociceptors by injured tissue & afferent feedback onto mast cells
- Dilation of nearby blood vessels
Hyperalgesia
An increased sensitivity to feeling pain and an extreme response to pain
Dorsal columns
Touch and Propioception
Touch and Proprioception route
Dorsal Root ganglion Dorsal columns Medulla Medial lemniscus Thalmus Somatosensory cortex
(Contralateral or Ipsilateral) Touch and proprioception
Ipsilateral
(Contralateral or Ipsilateral) Temperature and Pain
Contralateral
Temperature and Pain route
Dorsal Root ganglion Dorsa, horn Anterolateral column Branches into the reticular formation Thalamus Somatosensory cortex
Which afferents commonly synapse on the same neurons in the spinal cord?
Visceral & somatic pain afferents
Heart attacks commonly produce pain in the
in the left arm.
Descending pathways regulate
nociceptive information
Analgesia
Reduction of pain through presynaptic inhibition
What do opiate neurotransmitters do?
Presynaptic inhibition
Stop substance P from being released in spinal cord
______ perception is dependent on context
Visual
part of eye that refracts (bends) light to a single point
Lens
Light is refracted by (2)
the cornea and lens
What refracts more light: Cornea or lens
Cornea
What accommodates for changes in object location?
Lens
Nearsighted (eyeball)
eyeball too long
Farsighted (eyeball)
eyeball too short
Nearsightedness is corrected by a ____ lens
concave
Farsightedness is corrected by a ____ lens
convex
Cataract
changes in lens colour
Presbyopia
the lens gets stiff and is unable to accommodate near vision
Astigmatism
the lens or cornea are not spherical
myopic
nearsighted
hyperopic
farsighted
Fovea centralis
the retinal circuitry is shifted out of the way
only neurons that connect the outer retina to the inner retina
Bipolar cells
Help integrate and regulate the input from multiple photoreceptor cells
Horizontal cells
the major carriers of rod signals to the ganglion cells in the retina
Amacrine cells
Ganglion cells
the projection neuron
Make up the optic nerve
Phototransduction
Light causes photoreceptors to hyperpolarize
Four different opsin molecules (rhodopsin is found in the rods)
Rods/Cones:
High sensitivity, night vision
Rods
Rods/Cones:
Low sensitivity, day vision
Cones
Rods/Cones:
More rhodopsin, captures more light
Rods
Rods/Cones:
High amplification, single photon closes many Na+ channels
Rods
Rods/Cones:
Slow response time
Rods
Rods/Cones:
Faster response time
Cones
Rods/Cones:
Lower amplification
Cones
Rods/Cones:
Less opsin
Cones
Rods/Cones:
More sensitivity to scattered light
Rodes
Rods/Cones:
Most sensitive to direct axial rays
Cones
Rods/Cones system:
Low acuity: not present in central fovea, highly convergent
Rod System
Rods/Cones system:
High acuity: concentrated in fovea, less convergent
Cone system
Rod/Cone system:
Achromatic: one type opsin
Rod System
Rods/Cones system:
Chromatic: three types of opsin
Cone system
Bright Light which rod/cones are active/inactive
Rods are inactivate Cones are active
Dark which rods/cones are active/inactive
Cones are inactive Rods are active
Why does temporary blindness occur when going from light to dark?
Temporary blindness until rods “re-activate” and take over
Why does temporary blindness occur when going from dark to light?
Rods are initially saturated. Temporary blindness until rods “inactivate” and cones take over
What breaks in phototransduction
lights breaks the bond between opsin and retinene (chromophore)
T/F: It takes time to put the chromophore and opsin back together
T
Retina reports relative/absolute intensity of light
relative
signal the relative differences of the light (contrast) across their receptive fields
- B/W
- Colour
Retinal ganglion cells
Photoreceptors are sensitive to ________
wavelength
What determines the chromatic sensitivity of the photoreceptor
opsin molecule
What encodes the relative values of brightness and colour
the output of the retina
both eyes with contralateral visual field
Optic tract
one eye with both visual fields
optic nerve
Cervical Nerves
- body part
- pairs
Neck, shoulders, arms and hands
8
Thoracic Nerves
- body part
- pairs
Shoulders, chest, upper abdominal wall
12
Lumbar Nerves
- body part
- pairs
Lower abdominal wall, hips, and legs
5
Sacral Nerves
- body part
- pairs
Genitals and lower digestive tract
5
What muscles control lens shape?
Ciliary muscles
