205 NS - Physiology Flashcards
Describe the formation, circulation, and removal of cerebrospinal fluid (CSF).
- Formed in the choroid plexus of ventricles (mainly lateral)
- Enters the third ventricle through foramen of Monro
- Enters the fourth ventricle through the aqueduct of Sylvius
- Enters cisterna magna behind medulla & beneath cerebellum
- Though midline foramen of Magendie & 2 lateral foramina of Lushka, it enters the subarachnoid space
- Removed by arachnoid villi into dural venous sinuses
Broca’s area - location, #, function
Location: near the motor cortex, inferior frontal gyrus
#: Area 44
Function: production of speech
Wernicke’s area - location, #, function, lesion
Location: posterior 1/3 of lateral superior temporal gyrus; close to the auditory cortex
#: Area 22
Function: for comprehension - receives sensory, auditory & visual info
Lesion: causes difficulty in attributing meaning to words
Wernicke’s aphasia
Inability to comprehend speech
Broca’s aphasia
Inability to produce speech
Global Aphasia
Both Wernicke’s & Broca’s area affected
What happens when there’s a lesion in the angular gyrus?
Dyslexia - visual info not processed & transferred to Wernicke’s
4 stages of NREM sleep & its waves
Stage 1 - frequency ↓, amplitude ↑
Stage 2 - frequency ↓, amplitude ↑; sleep spindle
Stage 3 - low frequency, high amplitude
Stage 4 - low frequency, high amplitude; delta waves
Physiological changes during sleep
During NERM → BMR ↓
During REM → BMR ↑ - w rapid eye movement
Hypothalamic regions modulating sleep
Lateral hypothalamus - secretes orexin/hypocretin - maintain awake state Ventral preoptic (VLPO) nucleus - activity inhibits brainstem areas - sleep
*balance of 2 determines awake/sleep
What is REM sleep?
Low amplitude high-frequency waves, as seen in the awake state
What’s the reward & punishment center of the brain?
Ventromedial nucleus
Neural circuits mediating sleep
Stimulate RAS → awake
Low-frequency stimulation of thalamus → sleep
Brainstem regions that maintain an awake state & their secretions
Raphae nucleus - serotonin
Locus coeruleus - norepinephrine
Tuberomamillary nucleus of hypothalamus - histamine
Signs of LMN lesion (6)
Individual muscles affected Severe atrophy Fasciculations seen Flaccid paralysis - hypotonia Tendon reflex absent Normal plantar reflex (flexion)
Signs of UMN lesion (6)
Usually affects groups of muscle No atrophy No fasciculations Spasticity is seen - hypertonia Tendon reflex exaggerated Extensor plantar reflex (Babsinki sign)
Parts of Basal ganglia
Caudate, Putamen, Globus pallidus - cerebrum
Substantia nigra - midbrain
Subthalamic nucleus - diencephalon
Decorticate rigidity
Flexion of UL, extension of LL
by damage to upper midbrain
Decerebrate rigidity
Extension of all limbs
by damage to lower midbrain & upper pons
Role of Basal ganglia
Planning & programming of voluntary movement
What forms the striatum?
Caudate + putamen
What is seen in viral (aseptic) meningitis?
Lymphocyte count increases
Glucose levels normal
What is seen in bacterial (pyogenic) meningitis?
Protein concentration of CSF increases
Glucose levels decrease
Neutrophil count increases
What cannot pass through BBB?
Proteins
Non-lipid soluble substances
What can pass through BBB?
Lipid soluble substances: gases, alcohol, anaesthetics
What can pass through blood-CSF barrier?
Water, lipid soluble substances & gases
Function of blood-brain barrier
Maintains constant electrolyte levels
Prevents entry of toxins into brain
Prevents leak of neurotransmitters into blood
Prevents entry of bilirubin into the brain
Premature babies have leaky barrier
What forms the blood-brain barrier?
Foot process of astrocytes around capillaries
Virchow–Robin space
Perivascular space, space between artery and brain tissue
Function of thalamus
Acts as a relay center, receiving and distributing information between the peripheries and higher centers
Connections of Basal ganglia
Cortical neurons → striatal neurons (stimulatory)
Striatal neurons → globus pallidus (inhibitory)
Globus pallidus → thalamus (inhibitory)
Thalamus → cortical neurons (stimulatory)
What are the 2 classifications of senses?
Somatic senses
Special senses
3 types of somatic senses
Mechanoreceptive
Thermoreceptive
Nociceptive
5 types of special senses
Vision Hearing Smell Taste Vestibular
7 sense receptors
Free nerve endings Meissner's corpuscle Merkel's disc Hair end organ Ruffini's endings Pacinian corpuscles
Free nerve endings
Superficial
i.e. thermoreceptor
Meissner’s corpuscles
Superficial Fingertip, lips Adapt rapidly Sense movement over skin Detect low frequency vibration
Merkel’s disc
Superficial
Texture
Adapt slowly
Hair end organ
Superficial Free nerve ending at base of hair Adapt rapidly Sense initial touch Sense movement of hair
Ruffini’s ending
Dermis
Adapt slowly
Joint capsule
Detect pressure/stretch
Pacinian corpuscles
Dermis
Adapt rapidly
High-frequency vibrations
Deep pressure
How are mechanical receptors stimulated?
By deformation
Adequate stimulus
Receptors respond maximally to 1 stimulus
Where & when is action potential generated?
1st node of Ranvier when threshold is reached
How do Pacinian corpuscles adapt rapidly?
Due to fluid shifts within the corpuscles
Rapidly adapting receptors respond only during ______ of stimuli
beginning or end
Slowly adapting receptors respond to ______ stimuli
sustained
What type of neuron has highest conduction velocity?
A alpha
What type of neuron has lowest conduction velocity?
C
- nonmyelinated
Which is the only non-myelinated type of neuron?
C
Purpose of labeled line principle
Helps brain to identify the type of stimulus producing the sensation
Sensory unit
Each sensory neuron with all its branches and receptors
Receptive field
Area of skin innervated by each sensory neuron
Lateral inhibition
Increases contrast of sensory info
Because it spreads to sides of excitatory signal and inhibit adjacent neurons
Higher stimulus intensity stimulates ______ sensory neurons & ______ number of ______
more; increases; action potential
Recruitment of neurons
Higher stimulus intensity stimulates more sensory neurons
Somatosensory cortex located?
Behind central sulcus
Primary somatosensory area Brodmann’s area #?
3, 1, 2
Primary somatosensory area concerned with?
Reception & interpreation of sensations
Secondary somatosensory area Brodmann’s area #?
5, 7
Secondary somatosensory area concerned with?
Higher order processing of sensory info
Larger areas for ______ & ______ in the sensory homunculus.
lips; fingers
Which layer of somatosensory cortex do ascending nuerons synapse?
Layer 4
Lesion in primary somatosensory cortex causes?
Abnormal tactile localization
2-point discrimination lost
Astereognosis
Graphaesthesia
Abnormal tactile localization
Inability to localize site of sensation
Astereognosis
Inability to detect shape or form of objects
Graphaesthesia
Inability to identify what is written on skin
2-point discrimination
Ability to identify closely applied touch stimuli as 2 separate stimuli
- greater in fingertips & lips bc they have smaller receptive fields
- can distinguish 2 mm
Static proprioception
Info about position of diff body parts in space
In relation to each other
Dynamic proprioception
Info on rate of movement (kinesthesia)
Vibration sense is due to?
Repeated cutaneous stimulation
What fiber carries vibration sense?
A beta fibres
Pain is caused by?
Tissue damage
Fast pain
WIthin seconds
Sharp pain, picking pain, acute pain, electric pain
Superficial
Slow pain
Seconds to minutes
Burning pain, throbbing pain, aching pain, nauseating pain
Superficial & deep
What type of receptors are pain receptors?
Free nerve endings
“nociceptors”
Why is pain sensation non-adapting?
So that we reaact to the pain quickly to prevent further damage
Fast pain is carried by?
A delta fibres
Slow pain is carried by?
C fibres
How does serotonin suppress pain?
Stimulate interneurons that secrete enkephalins
Stimulation of tactile ______ fibres can suppress pain
A beta
Referred pain
Pain in viscera referred to surface of body
bc both have same dermatomal segment origin in embryo
Where does cardiac pain refer to?
Left-arm
What may cause visceral pain?
Ischemia
Distension
Spasm
Chemical stimuli
Visceral pain is carried by ______ fibres.
C
Visceral inflammation stimulates ______ & ______ pain fibres?
visceral; parietal
Where does appendicitis pain refer to?
Around umbilicus
What carries parietal pain?
C fibres carried in autonomic neurons
What causes parietal pain?
Carried by spinal nerves and cause localized pain
What fibres carry thermal sensation?
A delta & C fibres
At what temperature are cold receptors stimulated maximally?
24°C
Brown Sequard Syndrome
Hemi section of spinal cord
Pain, temperature lost on contralateral side
Vibration, light touch, motor lost on ipsilateral side
Phantom limb
Sensations in amputated area - stimulation of nerve stump
Where do dorsal column sensations cross?
Medulla
Where do spinothalamic pathways cross?
Spinal cord
Dorsal column sensations
Fine touch
Vibration
Position
Spinothalamic sensations
Pain
Temperature
UMN lesion - face
Spare upper face - as it has bilateral innervation
LMN lesion - face
Weakness in lower & upper face
Role of premotor cortex
Idea for movement from prefrontal cortex
Converted to plan by basal ganglia & lateral cerebeluum
UMN vs LMN
UMN - CNS - brain + spinal cord
LMN - PNS - others
Direct pathway of basal ganglia
Facilitates intended movement
Indirect pathway of basal ganglia
Suppresses non-synergistic & competing movement
Lead pipe rigidity
Hypertonic state throughout the range of motion
Seen in Parkinson’s disease
Cog-wheel rigidity
Hypertonic state with superimposed ratchet-like jerkiness and is commonly seen in upper extremity movements
Lead pipe rigidity + tremor
Seen in Parkinson’s disease
Oculomotor loop of basal ganglia
Saccadic eye movement
Prefrontal loop of basal ganglia
For cognition - initiating planning
Limbic loop of basal ganglia
For emotions - switching from one mood to another
Cerebellar function
Helps in motor agility
Error correction & motor learning
How does the cerebellum connect w UMN?
Through thalamus
Superior cerebellar peduncle
Sends output from the cerebellum
Inferior cerebellar peduncle
Receives input for cerebellum from spinal cord & brainstem
Also sends out impulses
Middle cerebellar peduncle
Largest
Gets inputs for cerebellum through pontine nuclei from cortex
Vermis of cerebellum
Co-ordinates movements of proximal muscles
Major afferents to cerebellum
Pontine nuclei
Vestibular nuclei
Spinocerebellar & cuneocerebellar tract
Inferior olive
Inferior olive concerned w
Motor learning & error correction
Climbing fibres
Can modulate synaptic connection between parallel fibres & Purkinje cells
Weaken the parallel fibre synapse w Purkinje cells by LTD (long-term depression)
Signs of cerebellar disease
Dysmetria/Dysdiadochokinesia Ataxia Nystagmus Intension tremor Scanning speech Hypotonia
Scanning or staccato speech
Talking syllable by syllable w gap between every syllable
Seen in cerebellar lesion
Why does cerebellar lesions cause ipsilateral problems?
bc spinocerebellar pathways are ipsilateral
