Ch. 14 Flashcards
Sensation
Process initiated by stimuli acting on sensory receptors
Perception
he conscious awareness of sensations
Senses
The means by which the brain receives info about environment and the body
What are the 2 groups senses are divided into?
General and special
General senses
Have receptors distrubuted over a large part of the body
What are the 2 groups general senses are divided into?
Somatic and Visceral
Somatic senses
Provides info about what?
What is the receptor type?
- *Provide sensory info about the body and environment**
1. Touch
2. Pressure
3. Temp
4. Pain
5. Proprioception
Receptor type -
Mechanoreceptors, Thermoreceptors, Noreceptors
Nerve ending -
Meissner corpusle, Hair follicle, Merkel disc, Pacinan corpuscle, free nerve ending, Ruffini end organ
Proprioception
The sense of your bodies position and movement
Visceral senses
Provides info about what?
What is the receptor type?
What are the nerve endings?
Info about various internal organs and consists primarly of
- Pain
- pressure
Special senses
are localized to specific organs that have specialized receptors
Smell, tasts, sight, hearing, and balance
What are the 3 criteria used to classify sensory recpetors?
- Type of stimulus they detect
- Location in the body
- Receptor structure
What are the 5 types of sensory receptors based on type of stimulus they detect?
- Mechanoreceptors
- Chemoreceptors
- Thermoreceptors
- Photoreceptors
- Nociceptors
What are Mechanoreceptors ?
Respond to mechanical force such as compression, bending or stretching of cells.
Physical simulus
** the senses of touch, pressure (BP), proprioception, hearing and balance all depend on a variety of mechanoreceptors
Chemoreceptors
Respond to chemicals
*Smell and taste depend on chemoreceptors
Thermoreceptors
Respond to changes in temp at site of receptor
There are more cold then there are hot receptors
Photoreceptors
Respond to light striking the receptor cells and are necessary for vision
Nociceptors
Aka Pain receptors
Respond to extreme mechanical., chemical and thermal stimuli
What are the 3 types of sensory receptors based on their location?
Cutaneous receptors
Viscerorecepors
Proprioceptors
Cutaneous receptors
Are associated with skin. Provide info about external environment
Viscerorecpetors
Associated with the viscera or organs, provide info about internal environment
Proprioceptors
associated with joints, tendons and other connective tissue
Provide info about body position, movement, and extent of stretch or force of muscular contractions
What are the 8 type of sensory recpetors based on structure?
Free nerve ending
Merkel Disc
Hair follicle
Pacinian corpuscle
Meissner corpuscle
Ruffini end organ
Muscle spindle
Golgi tendon organ
Free nerve endings
Definition
Location
Responsible for / Involved in
Relatively unspecialized neuronal branches simular to dendrites
Distrubuted through out most parts of body and are especially abundent in epithelial and connecive tissues
*Responsible for a number of sensations, pain, temp, itch and movement
Can be either tonic or phasic
Cold receptor
Increases it rate of action potential production as the skin is cooled
Warm receptors
Increases the rate of AP production as skin temp increases
Merkel discs
Defination
Location
Responsible for
AKA Tactile disks
Consists of axonal branches that end as flattened expansions each associated with an epithelial cell.
Distrubted throughout the basal layers of epidermis just superficial to basement membrane
*involved in sensations of light touch and superficial pressure/ can detect skin displacement of less than 1 mm
Hair follicle receptors
Definition
Location
Responsible for / Involved in
Respond to very light bending of the hair
*are involved in light touch
Not very localized but very sensitive
Pacinian corpuscles
Aka Lamellated corpuscles
Definition
Location
Responsible for / Involved in
Complx receptors that resemble an onion
a single dendrite extends to the center of each pacinian corpuscle.
located within subcutaneous tissue.
Responsible for deep cutaneous pressure and vibration
Meissner corpuscles
Definition
Location
Responsible for / Involved in
AKA tactile corpuscles
Evaluating texture
Distributed through out the dermal papillae
Involved in 2 point discrimination
numerous and close together in tounge and fingertips
2 point discrimination
ability to detect simulaneous simulation of 2 meissner corpuscles in 2 disinct receptor fields bu touching 2 points on skin
Numerous on tounge and fingertips
Ruffini end organs
Definition
Location
Responsible for / Involved in
Located in dermis of skin, primarily in fingers
Respond to pressure on skin directly superficial to receptor and to stretch of adjacent skin.
Important in continous touch or pressure
Muscle spindles
3-10 specialized muscle fibers that are located in skeletal muscles; provide info about length of muscle
Golgi tendon organs
Proprioceptive receptors associated with fibers of a tendon near the junction between the muscle and tendon
activated by an increase in tendon tension
Receptor potentional
Once the sensory receptor has been stimulated it produces a graded potential called receptor potential.
Primary receptors
Sensory receptor is the sensory neuron
Secondary receptors
Specialized cell that releases neurotransmitters to the senosry neuron to activate an action potential
*Receptor cells of taste, hearing and balance belong to this category
Adaptation
decreased sensitivy to continued stimulus.
Example clothes touching skin
Tonic receptors
Generate action potentials as long as stimulus is applied to they adapt very slowly
*Merkel disc and ruffini end organs
Phasic receptors
adapt rapidlly so they are more sensitive to changes in stimuli
Pacinian and meisseners
Some ascending pathways in CNS names start with ________ & end with_________
Others pathways indicate_________?
Origin
termination
Ex. Spinocerebellar
Location in spinal cord
What is the 3 neuron pathway?
Primary (Sensory recptor) - From PNS->Posterior horn->Synapse with interneuron
Secondary (Interneuron) - Decussate to other side, enter spinothalamic tract, ascend to thalamus
Tretiary - Thalamus to somaticsensory cortex
The 2 major pathways involved in conscious perception of external stimuli are
- Spinothalamic tract of anterolaeral system
- Dorsal-column/medial -lemniscal system
Anterolateral system
1 of 2 major systems that convey cutaneous sensory info to the brain
Includes 3 tracts: Spinothalamic, spinoreticular, spinomesencaphalic
Spinothalamic tract
Allows conscious perception of pain and temp as well as light touch, pressure, tickle, and itch
- Receptors go into dorsal root ganglion
- Connect with secondary neruon, desuccate and ascend to thalamus
- Connect to tretiary neuron and go to somaticsensory area of cerebral cortex
Spinoretuclar tract & Spinomesencephalic tract
Carry pain and touch sensations to other parts of brain, where info is not consciously perceived
**Some spinoretuclar tracts do not cross over bu ascend on the ipsilateral side of spinal cord
Primary neurons of spinothalamic tract..
1st neurons in pathway
Connect sensory recptor with spinal cord
Primary neuron cell bodies are located in dorsal root ganglia
Relay sensory input from the periphery to the dorsal horn of spinal cord where they synpase with interneurons
Secondary neurons in spinothalamic tract…
relay info to brain
within spinal cord, axons from 2nd neuron cross or decussate to the opposite side of spinal cord (occurs in anerior portion of gray and white commissures) Axons then enter spinothalamic tract and ascend to thalamus. They then synapse with tertiary neurons
Tertiary neurons in spinothalamic tract…
in the thalamus relay info to neurons in somatosensory cortex
Spinotectal tract
A portion of the spinomesencephalic tract that ends in superior colliculi and transmits action potentials involved in relfexes that turn head and eyes toward cutaneous stimulation
Dorsal column/Medial lemniscal system
Consists of 2 pathways that carry the sensation of 2 point discrimination, proprioception, pressure and vibration to cerebellum and cerebrum
- Primary neurons enter dorsal root ganglion from different locations. 1 for lower limbs/trunk and 1 for upper limb/trunk
- Ascend to the gracile and cutaneate nuclei synapse with secondary neuron, then decussate and ascend to thalamus
- Synapse with third order neuron then ascend to primary somatosensory cortex
*Primary neurons are located in dorsal root ganglia, are the largest cell bodies in dorsal root ganglia
Lemniscus means ribbon for thin like ribbon appearance of the pathway
Dorsal column/Medial lemniscal system are divided into what 2 tracts?
based on source of stimulus
Fasciculis gracilis and necleus gracilis
Fasciculus gracilis
Conveys sensations from lower part of the body, below the mid thoracic level
Middle tract
Terminates at Nucleus gracilis by synapsing with secondary neurons in medulla oblongata
Fasciculus cuneatus
conveys sensations from upper part of body, above the mid thorax
outer tract
terminates at nucleus cunteatus by synpasing with 2ndary neurons located in medulla oblongata
Trigeminothalamic tract
Facial equivalent of spinothalamic and dorsal-column/medial -lemniscal system / Carries sensory info from face, nasal cavity, and oral cavity including teeth
Cranial nerve V -The trigeminal nerve
First order neuron enters at dorsal root ganglion at pons. 1 neuron goes down to medulla and synapses with 2nd order neuron while other synapses with 2nd order neuron in the PONS
Second order neruons ascend to thalamus synapse with 3rd order neuron and ascend to primary somatosensory cortex
Spinocerebellar tracts
carry proprioceptive info to the cerebellum (unconscious)
*Posterior and anterior tracts
Primary neuron goes into spinal cord, synapses with 2ndary neuron in gray matter and ascends to cerebellum. No desucating
What are the 2 Spinocerebellar tracts?
Posterior spinocerebellar tract and anterior spinocerebellar tract
Posterior spinocerebellar tract
Carries info from upper part of body in the thoracic and upper lumbar regions. Contains uncrossed nerve fibers that enter cerbellum through inferior cerebellar peducles
Anterior spinocerebellar tract
Carries info from the lower trunk and lower limbs. contains both crossed and uncrossed nerve fibers that enter cerebellum through superior cerebellar peduncle
Not tested on
Pain
a sensation characterized by a group of unpleasant and complex perceptual and emotional expierences that trigger autonomic, psychological and somatic motor responses
Not tested on
What are the 2 components of pain sensation?
- Rapidlly conducted action potentials carried by large diameter, myelinated axons, resulting in sharp, well localized, pricking or cutting pain
- Followed by more slowly propagated action potentials carried by smaller less heavily myelinated axons resulting in diffuse burning or aching pain.
Not tested on
Gate control theory
Primary neurons send out collateral branches that synapse with interneurons which have a inhibitory effect thus pain action potentials can be suppressed
Not tested on
Analgesics
pain relieving medications that act in the same way as gate control
Not tested on
Referred pain
a painful sensation in a region of the body that is not the source of the pain stimulus
Pain is most commonly referred to the most superficial structures
Not tested on
Chronic pain
Long lasting pain
Primary sensory areas
specific regions of cerebral cortex where Sensory pathways project to
*Where sensations are percieved
Primary somatosensory cortex
Aka General sensory area
Recieves general input such as pain, pressure and temp from thalamus
Homunculus
Little human
Projection
Allow the brain to refer to a stimulus to the appropriate location on the surface of the body
What are the areas immediately adjacent to the primary sensory area called?
Association areas
Somatosensory association area
posterior to somatosensory cortex
Functions with visual association cortex in process of recognition
Visual association area
anterior to visual cortex
Functions with somatosensory association area in process of recognition
Upper motor neurons
Connect the cerebral cortex to lower motor neurons directly or through interneurons
Cell bodies are located in cerebral cortex
Lower motor neurons
Connect upper motor neurons to skeletal muscles
Synapse in anterior gray horn/ lower motor neuron cell bodies are in anterior gray horn
Have axons that leave CNS and extend through peripheral nerves to innervate skeletal muscles
Premotor area of cerebral cortex
staging area where motor functions are organized before they are initiated
*More subconscious
Prefrontal area
Controls motivation and foresight to plan and initiate movements
*conscious
Also involved in regulation of emotional behavior and mood
Desending motor fibers are divided into what 2 groups?
Direct and indirect
Direct pathways
AKA pyramidal system
Upper motor neurons synpase directly with lower motor neurons in brainstem or spinal cord
Involved in maintaining muscle tone and controlling the speed and precision of skilled movements
Primarily fine movments involved in dexterity
*Only exist in mammals
Indirect pathways
aka Extrapyramidal system
Control conscious and unconscious movements in trunk and proximal limbs
involved in less precise control of motor functions, especially those associated with overall body coordination and cerebellar function such as posture
Upper and lower motor neurons do not directly connect bvut synapse with intermediate nucleaus in brain stem
Corticospinal tract
Controls?
Direct or indirect pathway?
Types of tracts?
involved in direct cortical control of movements below the head
Direct pathway
Lateral corticospinal tract and Anterior corticospinal tract
Corticobulbar tract
involved in direct cortical control of movements in the face and tounge
Involves cranial nerves VII facial & XII hypoglossal
- Start at cortex descend through cerebral peduncles
- 1 connects to lower motor nueron in the PONs & Facial nerve while the other descends down to the medulla and connects to lower motor neuron and hypoglossal nerve
Cranial nerve nuclei
give rise to nerves that control tounge movements, mastication, facial expression, some eye movements, palatine, pharyngeal and laryngeal movements
What are the indirect pathways
upper and lower motor neurons synapse in an intermediate mass
Rubrospinal tract
Upper neurons synapse in red nucleus - decussates in midbrain and descends in lateral column of spinal cord
Major role in regulating fine motor control of muscles in distal part of upper limb
Vestibulospinal tracts
Originate in vestibular nuclei of Medulla oblongata and descend in anterior column of spinal cord, then synapse with interneurons and lower motor neurons
primary maintaince of upright posture
innervating extensor muscles in trunk and proximal portions of lower limb
Reticulospinal tract
originates in reticular formaion of pons and medulla oblongata and descends in lareral column of spinal cord
maintains posture by controlling trunk and proximal upper and lower limb muscles during certain movments
Tectospinal tract
originates in superior colliculus
Controls reflex movment of head to bright lights., noises and rapid movements
Basal nuclei
important in planning, organizing and coordinating motor movements and posture
Parkinson disease and cerebral palsy are basal nuclei disorders
Not tested on
The cerebellum consists of what 3 functional parts
Vestibulocerebellum
Spinocerebellum
Cerebrocerebellum
Not tested on
Vestibulocerebellum AKA flocculonodular lobe
Recives direct input from the vestibular structures especially the semicircular canals
Helps maintain muscle tone in postural muscles
Also helps control balance, especially during movements and corrdinate eye movement
Spinocerebellum
Consists of vermis and medial portion of the lateral hemisphere.
Helps accomplish fine motor coordination of simple movements
Not tested on
Comparator
sensing device that compares data from 2 sources
Cerebrocerebellum
Consists of the lateral 2/3rds of the lateral hemispheres. Communicates with motor, premotor and prefrontal portions of cerebral cortex in planning and practicing rapid, complex motor actions that require coordination and training
also involved in cognitive functions such as rhythm, concepttualization of time intervals, some word associations and solutions to peg board puzzles
Cerebellar disfunction results in
- Decreased muscle tone
- Balance impairment
- a tendency to overshoot when reaching for or touching an object
- an intention tremor which is shaking in hands that occurs while attempting to perfrom a task
Reticular formation
group of nuclei scattered throughout the brainstem that is involved in regulating cyclical motor functions
Reticular activating system (RAS)
Regulates sleep-wake cycle
is a bundle of nerves at our brainstem that filters out unnecessary information so the important stuff gets through
Recieves input from cranial nerves, optic and vestibulocochlear
Wakefullness is maintained by info coming in from eyes, ears and info from cerebral cortex.
Motor ouput projecting through the brainstem can be classified into what 2 categories
Somatic motor and parasympathetic
What 2 areas are involved in speech?
Wernicke area - Sensory part of parietal lobe
& Broca area - motor part of frontal lobe
What is the process for someone to speak a word they see?
- Primary visual cortex - action potentials from eyes reach primary visual cortex. Word is recognized in visual association area
- Wernicke area - word is understood
- Broca area - Action potentials connect wernicke area to broca area. word is formulated as it would be spoken
- Primary motor cortex - action potentials propagted to the premotor area, then to primary motor cortex where proper movements are triggered
Brain waves
patterns of electrical activity
Produced continually but their intensity and frequency differ from time to time based on state of brain activiy
Regular brain wave patterns are classified as
1 Alpha
- Beta
- Theta
- Delta waves
Alpha waves
observed in an normal person who is awake but in a quiet resting state with eyes closed
Beta waves
Occur during intense mental activity
Theta waves
usually occur in children but can also occur in adults who expierence frustration or certain brain disorders
Delta waves
Occur in infants , in patients with severe brain disorders, and in people who are in a deep sleep
Not tested on
Evoked potentials
Electrical responses caused by light, sound, or somatosensory stimuli
Not tested on
What are the 3 stages of the storage of memory?
Working
Short term
Long term
Not tested on
Working memory
Task associated memory
Brain briefly stores info required for the immediate performance of a task.
it lasts only a few seconds but is highly detailed
Occurs mostly in frontal cortex
Not tested on
Short term memory
Can be stored from minutes to days
*Susceptible to brain trauma
Not tested on
Long term memory
Requires prior formation of short term memory
more stable memory last days to years to lifetime
Not tested on
Consolidation
Process of transferring short term memory to long term
Gradual process involving the formation of new and stronger synpatic connections
Not tested on
Declarative memory
Explict memory
Involveds retention of facts you can easily state or declare
Names/dates/places
Hippocampus - factual content, name
Amygdala - emotional overtones to memory
Not tested on
What is the process of cerebellar comparator function?
- Motor Cortex sends action potentials to lower motor neurons
- Action potentials from motor cortex inform cerebellum of intended movement
- Lower motor neurons cause skeletal muscles to move
- Proprioceptors signals from skeletal muscles and joints send info to cerebellum about movment and postion
- Cerebellum compares info
- Action potentials from cerebellum to spinal cord modify stimulation from lower motor neurons to skeletal muscls
- action potentials sent from cerebellum to cortex to modify movement
Not tested on
Procedural memory
Implicit or reflexive memory
involves the development of skills or procedures
Riding a bike, playing piano
Stored in cerebellum and premotor area
Not tested on
Limbic system
includes olfactory cortex, deep cortical regions and various nuclei
Influences emotions, visceral response to emotions, motivation, mood, long term declarative memory and sensation of pain and pleasure
Associated with reproduction and acquisition of food and water
List the types of somatic and visceral sensory receptors, where they are located and how they function
- *Somatic
- *Located in skin, muscles and joints***
- Mechanoreceptor* - Physical (Compression/touch/hearing/balance)
- Thermorecptor* - Temp change
- Nociceptor* - Pain (Extreme Chemical, thermal, mechanical)
- *Visceral
- *Located in internal organs***
- Nocieptor*- - Pain (Extreme Chemical, thermal, mechanical)
- Mechanorecptor*- - Physical (Compression/touch/hearing/balance)
List the steps in the process of a sensation
- Stimulus is detected and converted into an action potential
- Ap -> CNS -> Cerebral cortex
- Translated so we are consciously aware of stimulis/sensation
Differentiate between primary and secondary receptors
Primary receptor is the one sending the action potential that is monitoring the stimulus
Secondary receptor is when the Specialized cell is separate from the sensory neuron. Specialized cell releases neurotransmitters to activate sensory neuron
*Each neuron can only detect one type of stimulus
What is the 3-neuron pathway?
What are the 3 sensory tracts that involve conscious perception of external stimuli?
Spinothalamic tract
Dorsal-column/medial lemniscal
Trigeminothalamic
What is the sensory tract responsible for unconscious external stimuli?
Spinocerebellar
Recall the homunculus. Which areas have the most and least dedicated space and why?
Most - face, forearm, genitals, leg
Least - trunk, neck, shoulder, elbow
depends on what you use the most to feel things with
Language and possibly artistic functions are not shared equally. What sides of the brain have more?
Left: Math and speech
Right: 3D or spatial perception, recognition of face, musical ability
Where is speech normally functioning in the brain?
Normally in left cerebral cortex
What is wernickes area?
Understanding what is heard and thinking of what you will say
What is Brocas area
Sending messages to appropriate muscles to actually make sounds
Aphasia
Absent or defective speech or language comprehension.
Caused by a lesion somewhere in the auditory/speech pathway
What are the 3 steps in order to decide to control skeletal muscles?
- Decide you want to move with prefrontal cortex
- Initiate movement first in premotor area - send a signal to upper motor neurons
- to send a signal down to activate the lower motor neuron which goes out to skeletal muscles to cause them to contract
Cerebral cortex also interacts with basal nuclei and cerebellum in planning, coordination and execution of movements
Precentral gyrus is also called______
and is responsible for?
Primary motor cortex, primary motor area
Control many voluntary movements especially fine motor movements of hands
What are the 2 direct pathways for motor?
Corticospinal tract
Corticobulbar tract
What is the pathways for the Lateral corticospinal tract & what does it control?
(Controls distal parts of limbs)
- Starts in Cortex and descends down to medulla where it decussates in the pyramid descends down lateral corticospinal tract
- Synapses with lower motor neuron which goes out anterior root to skeletal muscle
What is the pathways for the Anterior corticospinal tract & what does it control?
(Controls proximal part of the limb)
- Starts in cortex and descends
- Dessucates in spinal cord and synapses with lower motor neuron
- Exits anterior root to skeletal muscle
What are the funcitons of brainstem?
- All ascending and descending pathways pass through
- Nuclei of cranial nerves II-XII located
- Many reflexes important to survival located: Heart rate, bp, respiration, sleep, swallowing, vomit, cough, sneezing
- RAS - controls sleep/wake cycle
What is a electroencephalogram (EEG)?
Record of brains elecrical activity. Summation of all action potentials occuring at a particular moment, sensed by electrodes placed on the scalp
