Fundamental physiology basics if the neurologic exam Part 1 & 2 Flashcards
An excitable cell that receives a stimulus from a neuron or a receptor (dendrites)
Integrates it (ranks it, compares it to other stimuli) (cell body, axon hillock)
Passes along another stimulus if it is adequately stimulated (axon)
Neurons
Axons are carried in bundles (True/False)
True
-nerves in the peripheral system
-tracts in the central nervous system
Which neuronal cell bodies don’t reside in the CNS?
Dorsal root ganglia, autonomic ganglia, enteric ganglia
Neuronal cell bodies for the axons that bring most sensory information from the PNS to the CNS
Dorsal root ganglia
help regulate the activities of the autonomic nervous system
Autonomic ganglia
Help regulate the activity of the gut
Enteric ganglia
What sections make up the cerebrum?
cortex, basal ganglia, limbic structures
What area of the brain is responsible for most of our “higher functions”
-formation, storage, retrieval of memory (together with the limbic structures)
-speech & language
-abstract thinking, math, planning, and executing plans
Cerebral cortex
Also responsible for “what we’re conscious of”
-perception
-voluntary movements, both simple and complex
Name the lobe based on these functions:
-simple movements; pre-central gyrus
-complex motor plans; anterior portions + pre-central gyrus
-motor aspects of speech; anterior and inferior to the precentral gyrus
-planning, abstract thinking, social behavior (executive functions); distributed throughout this lobe & parietal lobe
Frontal lobe
Name the lobe based on these functions:
-Perception of touch, temperature, vibration; postcentral gyrus
-perception of “where our limbs are” (proprioception); post-central gyrus
-memory, executive functions, abstract reasoning; distributed throughout this lobe
Parietal lobe
Name the lobe based on these functions:
-hearing
-scent, taste
-recognition of speech
-memory (in cooperation with the limbic structures below it)
Temporal lobe
Name the lobe based on these functions:
-Vision
-Areas that relate visual stimuli to “actual things” (association cortex)
-memories related to what has been seen
Occipital Lobe
Memory formation requires what?
Attention and structures that “process” and form new memories.
Attention is associated with what?
prefrontal lobe
the structures of the limbic lobe below the temporal lobe
Memory “processors”
-hippocampus, amygdala
memory storage->
Memories tend to be stored in the cortex “close to” the sensation they’re associated with
ex) memory of a voice or word is likely in or close to the temporal lobe
Structures that lie below the cortex, close to the middle of the parietal and temporal lobes
serve to refine and regulate behaviors or movements
impaired in several diseases-when they lose function: tremors, rigidity, difficulty initiating movements, random/purposeless movements, tics, vocal utterances, personality changes
The basal ganglia
What are the deep structures in the cerebrum?
Basal ganglia: striatum, globus pallidus, subthalamic nuclei
Limbic structures: Amygdala & hippocampus
Relays information from sensory receptors in the peripheral nervous system to the cortex
-Joint/limb position and movement
-pain, touch, temperature
Relays information from brain areas to refine motor planning
-cerebellum, basal ganglia
Thalamus major roles
Controls much of the endocrine system, along with the pituitary gland
Regulates temperature, activity of the autonomic nervous system, fluid balance
Some thalamic nuclei modulate emotion and memory formation
Hypothalamus major roles
Name the structures:
1) Hypothalamus
2) Pituitary gland
3) Thalamus
-About 10% of the mass of the brain
-General function: compares information from the receptors that sense; joint position and movement, gravity, and equilibrium
-uses this information to adjust movements that are formulated in the prefrontal cortex (it very quickly error-corrects movements that are planned by comparing them to data from the receptors described above
Cerebellum
-Composed of the midbrain, pons, and medulla
-Cranial nerves found throughout this area
-All of the pathways that bring sensory information into the brain (from the PNS) or send motor information out of the brain (to the PNS) pass through here.
Brainstem
-Isolated from the peripheral nervous system and the rest of the body by a set of membranes (meninges)
-bathed in unique extracellular fluid (cerebrospinal fluid)
-neurons or axons do not usually regenerate after they have been damaged (regeneration is common after damage to axons in the PNS)
-Different (simpler) structure than the brain
Dorsal components tend to carry sensory information to the brain
Ventral components tend to carry motor information away from the brain to effectors (muscles in particular)
Spinal cord-Central Nervous System
-mostly cell bodies mixed with unmyelinated or lightly-myelinated axons
-Divided into two horns (ventral and dorsal)
Gray matter (yellow in this picture)
Cell bodies of neurons that control skeletal muscles.
Ventral Horns
Cell bodies of neurons that relay and integrate sensory information to the brain.
Dorsal Horns
Divided into columns- these are myelinated axons, no cell bodies. (dorsal, lateral and ventral columns)
White matter
Proprioception(joint/limb position), vibration sense, fast pain fibres - sensory to brain
Dorsal Columns
Pain, temperature, itch-sensory to pain
Anterior & Lateral columns
motor information to skeletal muscles
Anterior columns
Motor plan formed (pre-frontal cortex) ->
Activation of neurons in the primary motor cortex (prefrontal lobe) ->
Axons travel through the brainstem (medullary pyramids) and cross over to the opposite side->
Activation of primary motor neurons in the ventral horn that stimulates skeletal muscle contraction
or
Activation of motor neurons in the ventral horn that modify reflexes
Corticospinal tract
(lateral and anterior)
Lateral corticospinal tract
fine movements of extremities
Anterior corticospinal tract
movements of the trunk
It is estimated that up to ____% of corticospinal output is to “shut down” reflexes that would oppose voluntary movements.
90%
Cerebellum integrates information from proprioceptors ___________________ and the inner ear ____________________
-Compares this information with information from the motor “plan” generated by the _____________________
Cerebellum “adjusts” the motor plan by communicating (via the thalamus) with the ___________ and refining the movements relayed by the _________________________
-Spinocerebellar tract
-vestibulocerebellar tract
(keeps the cerebellum “up to date” on the actual position of the body in general and specific joints)
-Frontal lobe
(relayed through the pons)
-Frontal lobe
-corticospinal tract
The motor system depends heavily on input from receptors about the position of a joint, tension across a joint, and tension in a skeletal muscle.
Together, these are known as _________________
proprioceptors
Inform the cortex, the cerebellum, and neurons in the spinal cord about the actual position of the body.
Proprioceptors
proprioceptor-> dorsal horn-> dorsal column-> thalamus-> post-central gyrus of the parietal lobe
Dorsal column-medial lemniscal system
proprioceptor-> dorsal horn-> dorso-lateral columns -> cerebellum
Spinocerebellar system
A fast, involuntary sequence of muscular movements that:
-do not need higher brain centers; brainstem or spinal cord circuits are adequate
-are simple; usually, only a connection between groups of neurons are needed
-have a protective or stabilizing function; they help you pull away from a painful stimulus or help you stand
-need to be inhibited in order to perform purposeful, complex movements
Motor reflex
(the inhibition often comes from higher brain centers)
A proprioceptor that senses muscle stretch.
Muscle spindle
What happens as the muscle is stretched?
-Activates the muscle to contract against the stretch by stimulating the motor neuron in the ventral horn
-inhibits the antagonist muscle
What reflex helps to maintain posture?
Stretch reflex
Name the type of reflex:
-The antagonist muscle contracts and the agonist relaxes
-Thought to help prevent tearing during excessive force generation
Tendon Reflex
Name the type of reflex:
-In response to a painful stimulus, muscles of flexion are activated to withdraw a limb
Withdrawal reflex
Name the type of reflex:
-In response to an irritating stimulus, this appendage flexes down, and toes curl
Plantar reflex
Deep tendon reflexes:
simple stretch reflexes activated by striking the tendon with a reflex hammer-> contraction of the agonist muscle
ex) plantar reflex and tricep reflex
What are some causes of absent DTR’s?
Normal variation (some people are really difficult to get reflexes from)
Damage to sensory or motor nerves innervating the muscle being tested.
What are some causes of excessive DTR’s?
Loss of inhibition of reflexes from higher brain centers- usually the corticospinal tract (so damage to the corticospinal tract)
Reflexes are easier to interpret as abnormal when they are asymmetrical; one side greater/less than the other side.
Plantar reflex:
-When the lateral side of the foot is stroked firmly, the foot should plantar flex(ankle moves foot downwards) and toes should curl.
-This develops as we learn to walk; it depends on the corticospinal tract providing specific feedback to particular segments of the spinal cord (S1)
-If the foot dorsiflexes and the toes spread, this indicates that the corticospinal input to the lower limb is poor
-An upgoing plantar reflex is usually an abnormal finding
Name some cerebellar tests:
-Rapid alternating movements (RAMS)
-Point to point movements(patient touches his nose and rapidly touches your finger, and repeats)
-Heel to shin movements
-Gait; how coordinated is the patient’s gait?
If the cerebellum has lost function, then these movements are often clumsy, uncoordinated, and slow.
This test is thought to evaluate the function of the dorsal columns. Sensory input from proprioceptors to the cerebellum and the parietal cortex-key for joint and limb position sensing.
The patient stands with her feet together and closes her eyes. (if the patient starts to lose balance and starts to fall, indicates that the dorsal columns could be damaged.
Romberg Sign
How can brain structures in the corticospinal tract can be damaged in a wide variety of ways:
stroke, trauma, demyelinating disease, tumors
structures include: precentral gyrus and prefrontal cortex
Pronator drift:
The patient stands with arms outstretched, palms up, hand open, eyes closed.
The arm “drifts” to a more pronated position, the hand closes, and the arm tends to descend.
Corticospinal tract damage often results in a pattern of loss of muscle strength; extensors and supinators of the arm are weaker than the pronators or flexors.
Nerves that “emerge from the brain” and exit via skull foramina:
Cranial Nerves
Where do all other nerves except for cranial exit and travel through?
Exit the spinal cord, and travel through the intervertebral foramina.
Special senses:
sight, sound, taste, smell, “balance”
muscles that we have voluntary control over
Skeletal Muscles
sensations that we can perceive other than the special senses
Somatic Sensory
Mostly autonomic nervous system to glands/organs or from organs
Motor and sensory information to/from structures that we cannot control or percieve
Name the cranial nerves:
1) Olfactory
2) Optic
3) Oculomotor
4) Trochlear
5) Trigeminal
6) Abducens
7) Facial
8) Vestibulocochlear
9) Glossopharyngeal
10) Vagus
11) Accessory
12) Hypoglossal
Name the cranial nerve:
From the superior part of the nasal cavity-> olfactory bulb-> many different locations in the temporal and frontal lobes
Skull entry/exit point: Axons penetrate the skull via the tiny holes in the cribriform plate (ethmoid)
CN I: Olfactory nerve
How do you test CN I: Olfactory?
Ask the patient to identify a couple of distinctive smells (eyes closed if necessary)
ex) coffee, peppermint
What is the loss of the sense of smell?
Anosmia
Infections, head injuries
Name the cranial nerve:
from the retina(back of eye)-> thalamus-> occipital lobe (cortex)
Skull entry/exit point: Optic foramen (canal)
CN II: Optic nerve
How do we test CN II: Optic Nerve?
-The Snellen eye chart (central vision)
-Peripheral field tests (peripheral vision)
-Observation of the back of the eye (ophthalmoscope)
-Others: pupillary movements, rapid involuntary eye movements
What is the main function of CN III, IV, and VI?
Eye movements
Name the CN:
from the midbrain-> muscles around the eye
-projects to your papillary muscles (dilation, constriction) and your levator palpebrae superioris muscle (helps elevate your eyelid)
-most eye movements and control of pupil
Exit point: Superior orbital fissure
CN III: Oculomotor nerve
Name the CN:
midbrain-> one of the muscles around your eye (superior oblique)
-directs your gaze down and outwards
Exit point: Superior orbital fissure
CN IV: Trochlear
Name the CN:
pons-> one of the muscles around your eye(lateral rectus)
-Directs your gaze laterally
Exit point: Superior orbital fissure
CN VI: Abducens
How do we test CN nerves III, IV, and VI?
1) Ask the patient to “follow your finger”
2) Move your finger so that you draw a big H in the air in front of them. (eyes should smoothly follow your finger)
3) Shine a light into the patient’s eyes and hold an object close to the patient’s eyes. (Pupils should constrict in response)
Name the CN:
Two major functions:
1) Sensation over the face, scalp, nasal cavity, and cornea (somatic sensation)
2) Motor function(somatic motor) for the muscles of mastication (chewing) and some neck, and middle ear muscles
CN V: Trigeminal nerve
Where is the exit point of the CN V: Trigeminal nerve?
Exit from the pons, leaves through the skull:
-Superior orbital fissure: Cornea, forehead, scalp, eyelids, nasal mucosa (upper face, scalp)
-Foramen rotundum: face over the maxillary part of the face, including maxillary teeth (mid-face)
-Foramen ovale: lower jaw, proprioception for tongue (lower face, mouth-but NOT taste)
(temporalis, masseters, pterygoids
How do we test CN V: trigeminal nerve?
1) sensory- sharp, dull, and light touch over the face
2) Strength of jaw clenching and movements of the jaw
Name the CN:
Functions:
1) Facial movements OTHER THAN the tongue, eye muscles, and muscles of mastication. (controls more muscles than any other nerve in the body)
2) Taste from the anterior 2/3 of the tongue
3) Autonomic motor input to glands (salivary & tears, nasal glands)
4) Somatic sensation from the ear canal
Exits/enters the pons-> passes through the internal acoustic meatus and facial canal, exits through the stylomastoid foramen
CN VII: Facial nerve
How do we test CN VII: Facial nerve?
You ask the patient to use their facial muscles (make faces)
Name the CN:
Function: hearing and balance
-from inner ear-> internal acoustic meatus-> pons then it passes through the thalamus and synapses in the temporal lobe for the perception of sound
CN VIII: Vestibulocochlear nerve
How do we test CN VIII: Vestibulocochlear?
-Whisper to patient to test for auditory acuity
-Tuning forks: allow you to tell if there is a problem with the nerve, or ear canal, or ear drum, or cochlea pathway
If you “hear” the tuning fork better when it’s sending vibrations through your skull (versus being held up to your ear)-> problem with sound conduction through the ear canal, ear drum, or the tiny bones of your middle ear
Sound waves enter ear canal-> vibration of the tympanic membrane-> movements of the tiny bones in the middle ear (malleus, incus, stapes)
vibrations transmitted from the stapes into the cochlea within the inner-ear-> vibrations in the cochlea fluid moves the hairs-> hairs turn vibrations into electrical impulses-> electrical impulses are carried by the (1)________________
Hearing apparatus:
1) CN VIII: Vestibulocochlear nerve
If the vestibular apparatus of vestibular component of CN VIII is compromised, what happens?
Balance is impaired
can be seen when a patient is standing with their eyes closed.
many patients with this impairment are also very nauseous and have rapid, involuntary eye movements
Name the CN:
Function:
1) swallowing
2) sensation from the pharynx, part of the external ear and from chemoreceptors/baroreceptors in the carotid body
3) Taste from posterior 1/3 of tongue
4) Innervation of salivary glands (parotid)
Nerve enters.exits through the jugular foramen in the skull and projects to/leaves the medulla.
CN IX: Glossopharyngeal nerve
How do we test the glossopharyngeal nerve?
Stimulate the posterior aspect of the pharynx (this causes a gag reflex)
The soft palate and tongue elevate when stimulation is detected
not very helpful since most people have a diminished gag reflex
Name the CN:
Functions:
Pharyngeal muscles-swallowing and laryngeal muscles-vocal cords
Parasympathetic nervous system input to visceral organs discussed above
Sensation from the visceral organs it impacts and some pharynx and external ear
Sensory input from aortic baroreceptors and chemoreceptors
CN X: Vagus nerve
How do we test CN X: Vagus nerve?
Usually by listening to the patients voice.
-if horse then it may be due to damage of the vagus motor input to the vocal cords
-Ask patient to say “aaahhhh”-> elevation of the palate is part of the somatic function of the vagus nerve
Name the CN:
Function:
Innervation of the sternocleidomastoid and trapezius
cell bodies actually found in the cervical spinal cord
CN XI: Accessory nerve
How do we test SN XI: Accessory nerve?
Turning the head against resistance and shrugging the shoulders
Name the CN:
Functions:
Innervation of the tongue (key for speech and swallowing)
exits the medulla and passes through the hypoglossal canal
CN XI: Hypoglossal nerve
How do we test CN XI: Hypoglossal nerve?
Ask the patient to stick out their tongue and move it from side to side
If patient can’t do this, or if tongue is deviated then damage could be at the level of the nerve, medulla, or motor cortex.
Name the foramen:
1) Foramen magnum
2) Stylomastoid foramen
Name the foramen:
1) Optic canal
2) Superior orbital fissure
3) Foramen rotundum
4) Foramen ovale
5) Foramen spinosum
6) Foramen lacerum
7) Carotid canal
8) Internal acoustic meatus
9) Jugular foramen
10) Hypoglossal canal
11) Foramen magnum
What special senses are all carried via the cranial nerves and eventually project to the cortex?
vision-occipital lobe
sound-temporal lobe
taste and smell-inferior lateral frontal lobes
What senses all project to the post-central gyrus in the parietal lobe?
touch, vibration, proprioception (dorsal column-medial lemniscal system)
pain, temperature (spinothalamic tract)
Neurons that receive sensory input send their axons to the dorsal horns and then project into the dorsal columns (white matter of the spinal cord)
These axons stay on the same side until they enter the medulla -> synapse on another neuron
Second neuron passes to the other side of the medulla and then synapses with another neuron in the thalamus-> post central gyrus
Dorsal column-medial lemniscal system
Neurons that recieve sensory input send their axons to the dorsal horn-> second order axon crosses over to gray matter, then sends its axons to the brain in the lateral and anterior white matter of the spinal cord-> third order synapses to the thalamus
Spinothalamic tract
How do we test loss of sensation at the level of the spinal nerve, the spinal cord, the thalamus, or cortex?
Map out using dermatomes
How do you test dermatomes for the spinothalamic tract??
Sharp or somewhat sharp object
How do you test dermatomes for the dorsal column-medial lemniscal?
Dull or soft cotton swab
Vibration sense(tuning fork on bony prominence)
