Physiology Of The Nervous System Flashcards
Types of nervous system cell and function
Neurone - action potential generation and transmission
Astrocytes - support neurones and form bbb
Oligodendrocytes - insulate CNS neurones
Microglial cells - immune CNS response
Ependymal cells - line ventricles and spinal cord
Schwann cells - insulate PNS
Term for myelinated conduction down an axon?
Saltatory
Types of nerve fibre with example in order of decreasing size (with rough size)
Aalpha - proprioception and somatic motor - 12-20mm
Abeta - touch, pressure - 2-12mm
Agamma - muscle spindle 3-6mm
Adelta- pain, touch, temperature 2-5Mm
B - preganglionic ANS <3mm
C dorsal root - pain, temp, mechanoreceptors, reflex 0.4-1.2mm
C sympathetic - postganglionic ANS 0.3-1.3mm
Conduction speed of A type fibres
A alpha 70-120m/s
A beta 30-70m/s
A gamma 15-30m/s
A delta 12-30m/s
Speed of conduction in b and c type fibres
B 3-15m/s
C 0.5-2m/s (approx)
How is the neurone resting membrane potential set up?
NaKATPase 3:2 ratio
Both na and K diffuse back down their concentration gradient but membrane more permeable to K
Membrane impermiable to anions
Overall results in interior being more negative at -70mV
Term for the gaps in the myelin sheath
Nodes of Ranvier
What is the definition of ion conductance in relation to APs
The reciprocal of elctrical resistance of the membrane to a specific ion.
Key phases of a neuronal action potential
Slow rise to threshold
Spike potential - triggered by marked increase in Na permeability
After depolarisation
After hyperpolarisation
What limits the action potential depolarisation process
Na channels open only very transiently
Inside of cell becomes increasingly electropositive thus gradient that drives na influx disappears
K conductance also increases causing repolarisation
What is the after hyperpolarisation of an action potential
Slight but prolonged overshoot on repolarisation
Caused by slow return of k conductance to normal
What are the refractory periods of a neurone
Absolute refractory period - totally unresponsive to any stimuli regardless of strength - from time threshold is reached until repolarisation 1/3rd complete
Relative refractory period - period where stronger than normal stimuli may lead to excitation - from 1/3rd of repolarisation until start of after hyperpolarisation
What forms a synapse? Number per synapse?
Terminal buttons of a neurone (1-1000s) with cell body or axon of another neurone
What is the role of a synapse
UNIDIRECTIONAL impulse conduciton
What is an electrical synapse?
The synapse consists of the membranes meeting to form gap junctions allowing continued diffusion of ions
Width of a typical synaptic cleft
20nm
What are the three key organelles found in the synaptic button
Vesicles
ER
Mitochondira
Mechanism of synapse neurotransmitter release
Determining factor for amount released
Action potential reaches synaptic button.
Opening of voltage gated calcium channels - influx of calcium.
Proteins in vesicles bind to the calcium and spread apart allowing fusion with terminal membrane
Contents of vesicles released into cleft
Amount determined by calcium concentration
Why are post synaptic potentials transient
Reuptake of neuro transmitter
Enzymatic deactivation of neurotransmitter
Auto receptors on presynaptic membrane inhibit continued neurotransmitter release
What categories of effects can be mediated by neurotransmission
Excitatory (EPSP) eg opening of na channels causing depolarisation
Inhibitory (IPSP) eg opening of Cl or K channels causing hyperpolarisation
What are the main CNS neurotransmitters?
ACh
NA
A
Dopamine
Serotonin
Location and function of ACh neurotransmitter in CNS
Cerebral cortex, thalamus, limbic - memory, perception, cognition, attention
Location and function of NA neurotransmitter in CNS
Locus coeruleus, cerebellum, hypothalamus - decending pain, inhibition of purkinje cells, regulation of anterior pituitary secretion
Location and function of adrenaline neurotransmitter in CNS
Medulla - uncertain
Location and function of dopamine neurotransmitter in CNS
Substantia nigra, hypothalamus - control of motor functions, regulation of prolactin secretion
Location and function of serotonin neurotransmitter in CNS
Neocortex, limbic system, hypothalamus, nucleus and phase Magnus, spinal cord
Mood and behaviour, increase prolactin secretion, pain modulation
What is a sensory receptor
A transducer that converts a stimuli eg mechanical or thermal energy into an electrical stimuli
Can be part of a neurone or separate structure that is capable of generating and transmitting action potentials to the neurone
Can be either visceral or somatic
What is the distinction between visceral and somatic sensory receptors
Visceral perceive changes to internal environment are are not usually consciously perceived e.g. chemoreceptors
Somatic receptors respond to external stimuli such as temperature or touch, usually consciously perceived
Route of pain perception to brain
Nerve ending
A and C fibres
Dorsal root ganglion
Dorsal horn
Spinothalamic tract
Ventral and medial nuclei of thalamus
Somatosensory cortex
Layers of the dura mater
Inner cerebral layer covering brain and spine,
Outer endosteal which merges with periosteum of skin at foramen magnum (only in head, no endosteal layer in spine, just vertebra periosteum)
Where does the dural sac end in adults?
How is it attached down the spine
Ends around S2
Attached to the edge of the vertebral canal except posteriorly where it is free
Areas of the frontal lobe
Precentral area - with anterior (pre motor) and posterior (primary motor) regions
Prefrontal cortex - with superior, middle and inferior frontal gryi
Where is Broca’s area
Inferior frontal gyrus of dominant hemisphere
Functions of frontal lobe
Personality
Initiative
Judgement
Insight
Control of emotions
Contra lateral motor function
Regions within the temporal lobe and function
Primary and secondary auditory areas - hearing (primary locates source of sound, secondary interprets sounds)
Wernickes area in dominant hemisphere - speech comprehension
Areas and functions of the parietal lobe
Postcentral gyrus - primary sensory - judgement of shape and form, pressure and weight, position sense, localisation of stimuli
Sylvian fissure - secondary sensory - relating sensory information to past experience and interpreting it
Areas and functions of the occipital lobe
Primary visual area
What determins level of consiousness?
Activities of cerebral cortex and the reticular activating system
What is the reticular activating system
Inputs and outputs
A network of neurones in the brain stem reticular formation
Receives sensory input from ascending tracts and head senses (eyes, hearing, taste, trigeminal Sensation)
Projects to the cerebral cortex directly and via thalamus
Types of EEG rhythm with frequency
Alpha - 8-12Hz, usually occipital in adult human at rest with eyes closed
Beta - 18-30Hz, frontal region of alert adult
Omaga - 4-7Hz, large amplitude usually very old or very young
Delta - <4Hz
Basic sleep patterns and EEG findings
NREM - four stages (from 1-4 light to deep) with progressive slowing of EEG and increased amplitude of waves
REM - nrem pattern replaced with fast low voltage activity similar to alert individual
What are the roles of wernickes and broccas areas? Pathology results in…
How do they communicate
Wernickes - comprehension of audible and visual information - receptive dysphasia
Communicate via arcuate fascicules
Broccas - output of speech and coordination of vocal aparatus - expressive dysphasia
Main types of memory and regions involved
Explicit memory - conscious retrieval and awareness, either episodic (memory of events) or semantic (memory of words, rules, languages etc). Involves hippocampus and medial temporal lobes
Implicit memory - does not require conscious awareness, eg skills for day to day activities and habits e.g driving once a routine task (not learning). Does not involve hippocampus
Where is short term explicit memory processed
Hippocampus
Functions of the basal ganglia
Movement control and posture control
Which side of the body does the left cerebellar hemisphere control
Left! Ipsolateral not controlateral
Functions of cerebellum
Gait and balance
Which cranial nerves have the nuclei outside of the brain stem
I and II
Contents of the brain stem
Nuclei of cranial nerves III - XII
RAS
Ascending and decending tracts
Centres for respiratory, cardiovascular and gastrointestinal function
Centres for eye movement, balance and equilibrium
What are the metabolic requirements of the brain %
Cerebral blood flow
20% basal oxygen
25% basal glucose
700ml/min cerebral blood flow (around 14%)
Where in the brain receives most blood flow
Grey matter receives around 5x that of white matter
What is cerebral perfusion pressure e
CPP = MAP - ICP - Venous pressure
What factors control cerebral blood flow
Pressure auto regulation
Flow metabolism coupling
PaO2
PaCO2
What does the brain closely regulate to maintain constant oxygen and nutrient delivery
How?
In what range of CPP is It maintained
Cerebral blood flow
When CPP varies vascular resistance altered to maintain blood flow.
Between around 50-150mmHg
What is pressure auto regulation of cerebral blood flow?
As MAP increases cerebral vasculature constricts and viva versa
What is the effect of chronic hypertension on cerebral pressure auto regulation
Shifts curve to right (maintains in higher range)
What is the effect of voletile anaesthetics on cerebral auto regulation
Dose dependant vasodilation of cerebral vessels impairing auto regulation.
What is flow metabolism coupling in cerebral auto regulation
Increase in cerebral metabolic rate (e.g. seizure, fever)
Mediator release such as ach, no, substance p, serotonin (all possibly)
Cause increase in cerebral blood flow.
Opposite effect with decreased metabolic rate eg anaesthetics!
Effect of carbon dioxide on cerebral blood flow
Cerebral vasodilation increasing flow
In physiological range roughly linear
Outside normal range 1kpa increase in pCO2 increases cbf by 30%
No further effect above 10kpa or beneath 2.5kpa as max dilation/restriction reached
Why does co2 increase cerebral blood flow
Increased h+
As ph compensated for with time then cerebral blood flow returns to normal
Effect of oxygen on cerebral blood flow
Little change in physiological range but when PaO2 <6.7 or 92% then there is some vasodilation
What are the effects of the ans on cerebral blood flow
Mainly on larger vessels
B1 vasodilates
A2 vasoconstriction
Significant vasoconstriction can occur at very high concentrations of catecholamines.
Spinal cord end point at birth and adult hood
Birth lower border of l3
Adult l1/2 gap
Where is the spinal cord enlarged in diameter, why
Cervical and lumbar corresponding to brachial and lumbosacral plexuses
Spaces and potential spaces around the spinal cord
Subarachnoid space
Subdural space - potential
Extradural space
What traverses the subarachnoid space in the spine
3 incomplete trabeculae , 1 posterior subarachnoid septum and bilateral ligamentum denticulatum
What are the boundaries of extramural space around the spine
Between dura and spinal canal extending from foramen magnum ending at sacral hiatus
Contents of extradural space around spine
Lymphatics, fat, vasculature,
Includes vein outs plexus of Bateson communicating between pelvic and cerebral veins
What are the coverings of spinal nerves
Emerge from cord covered in pia and arachnoid mater, pierce the dura which then fuses with them forming the epineurium
What are the gaps in the shape of the spinal cord in cross section
Anterior median fissure
Posterior median sulcus
Where is csf located in the spine
In the sa space
In the central canal
What neurones make up most decending tracts
First order neurones from cerebral cortex
Synapse with second order neurones in anterior grey column of spinal cord
Second order neurone synapse with third order neurone (lower motor neurone) again in the anterior grey column of the spinal cord.
Third order neurone heads peripherally through the anterior root of the spinal nerves innervating skeletal muscle
What are the key descending tracts of the spinal cord? Brief function
Corticospinal - skeletal motor
Reticulospinal - alpha and gamma motor neurones
Tectospinal - reflex postural movements due to vision
Rubrospinal - posture and balance activating flexor and inhibiting extensor action
Vestibulospinal - posture and balance activating extensor and inhibiting flexor action
Olivospinal
Descending autonomic fibres
Route of corticospinal tract
Role
First order - motor cortex, medulla. 80% decussate forming lateral corticospinal tract, 20% remain ipsolateral forming anterior corticospinal tract
Skeletal muscle innervation
Neuronal structure of ascending spinal tracts
First order neurones posterior root ganglion - peripheral process receives sensory information from receptor, central process into spine vi posterior root and synapse with second order neurone in posterior grey column.
Second order neurone decussate and ascends to thalamus synapsing with third order neurone,
Third order neurone projects from thalamus to sensory cortex
Key ascending spinal pathways and what they carry,
Spinothalamic tract - pain and temp from 1st order Adelta and C fibres,
Gracile and curate tracts - touch, vibration and proprioception
Ant and post spinocerebellar tract - muscles and joint reception
Spinotectal - pain temp and touch facilitating spinovisual reflex
Spinoreticular tract - info effecting consciousness
Spinoolivary tract
Effect of a complete spinal cord transaction
Initially
All spinal reflexes depressed or absent
All muscle innervation below level paralysed
All sensation below level paralysed
Slow recovery of involuntary reflexes over several weeks but not voluntary
What is the recovery pattern of spinal reflexes post a complete cord transection
Initially flexor response to touch and anogenital reflexes
Last are tendon reflexes
Reflexes initially hyperactive when initially recovered
Can have mass reflex response to minor noxious stimuli with significant blood pressure changes.
Effect of hemisection of spinal cord
Ipsolateral loss of muscle power, fine touch, pressure and joint/vibration sense
Contralateral pain and temperature loss
Where do the spinothalamic and gracile/cuneate tracts decusate
Spinothalamic 2nd order neurones decusate at spinal level or one above/below
Gracile/cuneate - second order neurones decusate in above the gracile/cuneate nuclei I;the medulla
What is the basic blood supply to the spine and derivation
Single anterior spinal artery - union of branches from each vetebral artery, also from radicular arteries arising from deep cervical, intercostal and lumbar arteries
Two small poster spinal arteries - from posterior inferior cerebellar arteries
What is the effect of thrombosis of the anterior spinal artery
Anterior spinal artery syndrome With paralysis due to ischaemia of pyramidal tracts but continued sensation due to posterior supply of posterior columns
What connects anterior and posterior arteries of the spine
Vasa coronae
What is the main derivation artery of the anterior spinal artery
The arteria radicularis magna
What sort of reflex in the stretch reflex? How does it work
Monosynaptic
Spindle fibre stretched
Afferent conduction via 1a fibre through dorsal horn.
Synapse with efferent Aalpha motor neurone
Contraction of muscle
Example of polysynaptic muscle reflex
Withdrawal reflex
Noxious stimuli sensed
Afferent sensory signal activates 2 interneurones in spine
interneurone activates one muscle and other inhibits the antagonistic muscle
Limb withdraws from stimuli
What sort of muscle fibres do motor neurones control? What basis in the number of these fibres to number of neurones decided
Extrafusal fibres
Depends on how fine a action is required (ie one nerve to a finger supplies far fewer extrafusal fibres than a nerve to the thigh)
What are intrafusal muscle fibres
Form muscle spindle
Function of a muscle spindle
Detect muscle length
Central bag or chain of noncontractile fibres supplied by either Ia (both) or II (chain) afferents
Either end has a contractile region supplied by Agamma efferents
When muscle contracts spindle relaxes and afferent firing stops - opposite occurs on muscle relaxation or on passive stretching.
What happens to spindle sensitivity on muscle contraction
Spindle contacts and also becomes more sensitive
If muscle met with resistance intrafusal fibres shorten more than extrafusal fibres stretching the centre of the spindle and causing increased motor contraction.
What do golgi organs sense
Muscle tension
Detect stretch and provide inhibitory feedback to prevent muscle damage
Main function of pre motor cortex
Postural adjustment at the beginning of voluntary motion
What is the function of the supplemental motor area of the cortex
Planning of complex movements
How are motor signals passed to the spinal cord
Directly through corticospinal tract
Indirectly via accessory pathways through cerebellum, basal ganglia and brainstem nuclei
Three key functional parts of cerebellum and their function
Vestibulocerebellum - equilibrium during motion
Spinocerebellum - proprioception and coordination of motor actions
Neocerebellum - planned execution of voluntary movements esp rapid ones
Parts of basal ganglia
Caudate nucleus
Putamen
Globes pallidus
Subthalmic nucleus
Substantia nigra
Function of basal ganglia
Forms a loop with the cortex via the thalamus
Helps coordinate action with subconscious movements that are required to carry out the voluntary action.
Factors involved In posture control
Spinal cord - stretch reflex, proprioception transmission
Brainstem - facilitation and inhibition of stretch reflex,
Midbrain - tonic reflexes controlling head and neck position
Cortex - Agamma discharge to muscle spindle with physical postural reflexes
Where is csf produced
70% in choroid plexuses of ventricles
What are choroid plexuses
Function
Vascular invagination of highly vascular pia mater covered by single layer of ependymal epithelium
Secretion and filtration of plasma to form csf
How does ICP effect csf volume
No effect on production but increased ICP increases with increasing pressure
What is the route of csf
Lateral ventricles
Foramen of monro
Third ventricle
Aqueduct of Sylvius
Fourth ventricle
Formen of megendie and luschka
Subarachnoid space
Arachnoid villi Reabsorb into venous sinus
Why do large molecules not enter the csf
Tight junctions between endothelium of cerebral capiliaries
What agents easily pass the bbb
Water
Co2
Oxygen
Ions
Lipid soluble molecules such as voletile anaesthetics.
Total csf volume
Amount produced per day in typical adult
150ml
550ml
Normal ICP values
5-15mmHg
What is the monro Kellie doctrine
Regions discussed and %s
Change in volume of one intracranial compartment is accompanied by a reciprocal change in the other
Solid 10%’
Tissue Water 75%
Csf - 10%
Blood 5%
How can high ICP cause damage
Direct pressure of brain tissue
Distortion and herniation of intercranial contents
What is the effect of increasing volume of intercranial contents on ICP
Initially compensatory mechanisms keep in normal range then exponential increase as they fail.
Autoregulatroy Compensatory mechanisms for increased intercranial contents volume
Reduction in csf volume
Reduction in cerebral blood volume
Cerebral vasoconstriction
Increased arterial pressure
What therapeutic measures can be taken to control ICP by triggering auto regulatory changes
Reduction in cerebral metabolic rate (eg seizure termination, anaesthetic)
Reduced pCO2
Avoidance of low PaO2
Avoid raised JVP
What can cause realised jvp
Jv obstruction
Increased interthoracic pressures
Raised cvp
Head down position
Outer layer of the eye
Sclera with transparent cornea
Pathway of aqueous humour
Produced by ciliary processes catalysed by the action of carbonic anhydrase
Passes from posterior chamber to anterior chamber via the pupil
Drains through canal of schlemm into venous syste:
Which muscles cause what pupillary changes
Iris muscles
Constriction of circular muscles cause constriction
Constriction of radial fibres cause dilation
Terms for pupillary constriction and dilatation
Constriction - miosis
Dilatation - mydriasis
Which muscle controls lens accomodation
Ciliary muscle via suspensory ligaments
What is the blood supply to the photoreceptive cells of the eye
From the choroid, not the vessels on the retina surface
What pigments are contained in rods and cones
Where are cones concentrated
Rods - rhodopsin
Cones - red green and blue sensitive opsins
Cones are located at the fovea
Visual pathway up to point of optic nerve
Light stimulates photoreceptors causing electrical potential
Transmitted to ganglion cells via bipolar/horizontal and amicrine cells
Axons from ganglia converge forming optic nerve
Visual pathway from optic nerve onwards
Nasal retina axons (temporal vision) deccusate at optic chiasm
Temporal retina axons (nasal vision) continue ipsilatral
Follow optic tract back to lateral geniculate body where they synapse
Axons follow optic radiations back to primary visual cortex
Effect on vision of a lesion to the optic nerve
Loss of vision in one eye
Effect on vision of a lesion to the optic chiasm
Bitemporal hemianopia (damage to decussating fibres only)
Effect on vision of a lesion to the optic radiation
Homonymous hemianopia (effecting opposite side of vision to side of lesion)
Structure of the cochlear
Coiled tube divided into three canals lengthways - scala vestibuli, scala media and scala tympani separated by the reissners and basilar membranes.
What do the oval and the round window of the middle ear connect to
Oval window to stapes
Round window to scala tympani of cochlea
What fills the canals of the cochlea
Scala media filled with endolymph
Scala tympani and vestibuli with perilymph
Where are sound receptors located in the inner ear
Organs of corti located on basilar membrane in scala media
Mechanism of hearing
Sound wave vibrates tympanic membrane
Ossicles vibrate vibrating oval window
Pressure waves in scala vestibuli displace endolymph and then tectorial membrane displaced with respect to basilar membrane
Hair cells in organ of corti stimulated triggering a depolarisation And AP
Transmitted via ganglion cells to cochlear nerve
Cochlear nerve to cochlear nucleus in brainstem
Second order neurones transmit to Contralateral inferior colliculus
Then to the medial geniculate body
Then to primary auditory complex in temporal lobe
Where are most taste buds
Papillae at back of tongue
How long is the t1/2 of taste cells
2 weeks
Four taste modalities
Sweet sour salt bitter
Innervation of taste buds
Chorda tympani (anterior 2/3) - branch of facial nerve
Glossopharyngeal (posterior 1/3)
Greater petrosal (soft palate) - branch of facial
Where do the nerves supplying taste buds run too
Tractus solitarious in medulla then thalamus and cortex
What is special about olfactory cells
Only neuronal cells in body to robe replaced continually by division of underlying basal cells
Pathway of smell
Odoriferous compounds dissolve in mucus
Chemical interaction with chemoreceptors on olfactory cells cilia
Action potential spreads through neurone passing through cribiform plate to olfactory bulb.
Second order neurone project to olfactory cortex and also thalamus and limbic system
Definition of autonomic nervous system
The part of the nervous system that provides neurological control over the cviceral activities of the body. It is involuntary and allows the body to adjust to varying demands.
Where does the SNS arise
Route of nerves (general)
Exceptions?
Arise T1-L2 - the thoracolumbar outflow
Synapse in the paired sympathetic chain ganglia either side of vertebral column then postganglionic fibres to organs.
Some preganglionic fibres run straight through the sympathetic chain ganglia to ganglia close to effector site such as the coeliac and mesenteric ganglia or adrenal medulla (which is unique in having no postganglionic fibres)
Which nerves contribute to PNS outflow?
CN III, VII, IX, X
S2,3,4
What percentage of total PNS outflow is accounted for by the two vagus nerves
75%
Location of parasympathetic ganglia
In the effector organs thus short postganglionic neurones
Neurotransmitters for ANS preganglionic fibres
Ach
Neurotransmitters for PNS postganglionic neurones
Ach
Rarely vasoactive intestinal polypeptide
Neurotransmitter for postganglionic SNS neurones
Noradrenaline
Except sweat glands, piloerector muscles and some blood vessels (those supplying skeletal muscle) that use ach
Release from adrenal medulla on stimulation by sns with percentages
Adrenaline 80%
Noradrenaline 20%
Main receptors activated by noradrenaline
Alpha
Main receptors activated by adrenaline
Alpha and beta
Type of ach receptor in ans ganglia
Nicotinic
Type of ach receptor at PNS effector site (postganglionic PNS synapse)
Muscurinic
Types of muscurinic ach receptor and locations
M1 - CNS
M2 - heart
M3 - exocrine glands and vascular endothelium
What is a nicotinic ach receptor (receptor type)
Ligand gated ion channel
What is a muscurinic ach receptor type
G protein linked
Type of ach receptor at skeletal muscle
Nicotinic
Alpha 1 receptors found at
Blood vessels supplying salivary glands, skin, mucus membranes, kidneys, abdominal vicera, radial muscles of iris, urinary bladder sphincter
Salivary glands
Sweat glands in palms and soles
Alpha 2 receptors found at
Smooth mucslce of some blood vessels
Pancreatic islets for insulin (beta cells)
Pancreatic acinar cells
Beta one receptors found at
Cardiac muscle
Juxtaglomerular cells in kidneys
Posterior pituitary
Adipose tissue
Beta 2 receptors found at
Airways
Ciliary muscles of eye
Hepatocytes of liver
Beta 3 recptors found at
Brown adipose tissue
Components of limbic system
Functions
Hypothalamus - endocrine function, homeostasis
Amygdala - behavioural response to stimuli
Hippocampus - memory
All - behavioural, emotion
How does the hypothalamus contribute to temp homeostasis
Recieves afferent input of temp data from peripheral receptors and from receptors in anterior hypothalamus
Initiates physiological response to temp eg shivering, vasoconstriction and also behavioural changes eg extra clothes
How does the hypothalamus control anterior pituitary
Secretion from nerve endings in median eminance of hypothalamus of releasing and inhibiting hormones into the portal hypophyseal vessels
What are the hormones released by the hypothalamus that control anterior pituitary secretions
Adrencorticotrophic hormone releasing hormone
Thyrotropin releasing hormone
Growth hormone releasing hormone
Luteinising hormone releasing hormone
FSH releasing hormone
Prolactin releasing hormone
Prolactin inhibiting hormone
What hormones are secreted by posterior pituitary
Where are they produced
Oxytocin
Vasopressin
Produced in neurones of supraoptic and paraventricular nuclei of the hypothalamus - transported down the axons to endings in the posterior pituitary
Effects of oxytocin
Milk ejection
Uterine contraction
How is thirst sensation mediated
High osmolality and low volume detected by hypothalamus
Triggers vasopressin release and RAAS
How does the hypothalamus control food intake
Two centres feeding centre and satiety centre
Likely feeding centre constantly active and inhibited by saitity centre itself triggered by raised bm
