Physiology Of The Nervous System Flashcards

1
Q

Types of nervous system cell and function

A

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

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2
Q

Term for myelinated conduction down an axon?

A

Saltatory

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3
Q

Types of nerve fibre with example in order of decreasing size (with rough size)

A

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

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4
Q

Conduction speed of A type fibres

A

A alpha 70-120m/s
A beta 30-70m/s
A gamma 15-30m/s
A delta 12-30m/s

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5
Q

Speed of conduction in b and c type fibres

A

B 3-15m/s
C 0.5-2m/s (approx)

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6
Q

How is the neurone resting membrane potential set up?

A

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

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7
Q

Term for the gaps in the myelin sheath

A

Nodes of Ranvier

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8
Q

What is the definition of ion conductance in relation to APs

A

The reciprocal of elctrical resistance of the membrane to a specific ion.

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9
Q

Key phases of a neuronal action potential

A

Slow rise to threshold
Spike potential - triggered by marked increase in Na permeability
After depolarisation
After hyperpolarisation

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10
Q

What limits the action potential depolarisation process

A

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

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11
Q

What is the after hyperpolarisation of an action potential

A

Slight but prolonged overshoot on repolarisation
Caused by slow return of k conductance to normal

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12
Q

What are the refractory periods of a neurone

A

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

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13
Q

What forms a synapse? Number per synapse?

A

Terminal buttons of a neurone (1-1000s) with cell body or axon of another neurone

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14
Q

What is the role of a synapse

A

UNIDIRECTIONAL impulse conduciton

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15
Q

What is an electrical synapse?

A

The synapse consists of the membranes meeting to form gap junctions allowing continued diffusion of ions

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16
Q

Width of a typical synaptic cleft

A

20nm

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17
Q

What are the three key organelles found in the synaptic button

A

Vesicles
ER
Mitochondira

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18
Q

Mechanism of synapse neurotransmitter release
Determining factor for amount released

A

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

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19
Q

Why are post synaptic potentials transient

A

Reuptake of neuro transmitter
Enzymatic deactivation of neurotransmitter
Auto receptors on presynaptic membrane inhibit continued neurotransmitter release

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20
Q

What categories of effects can be mediated by neurotransmission

A

Excitatory (EPSP) eg opening of na channels causing depolarisation
Inhibitory (IPSP) eg opening of Cl or K channels causing hyperpolarisation

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21
Q

What are the main CNS neurotransmitters?

A

ACh
NA
A
Dopamine
Serotonin

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22
Q

Location and function of ACh neurotransmitter in CNS

A

Cerebral cortex, thalamus, limbic - memory, perception, cognition, attention

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23
Q

Location and function of NA neurotransmitter in CNS

A

Locus coeruleus, cerebellum, hypothalamus - decending pain, inhibition of purkinje cells, regulation of anterior pituitary secretion

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24
Q

Location and function of adrenaline neurotransmitter in CNS

A

Medulla - uncertain

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25
Location and function of dopamine neurotransmitter in CNS
Substantia nigra, hypothalamus - control of motor functions, regulation of prolactin secretion
26
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
27
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
28
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
29
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
30
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)
31
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
32
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
33
Where is Broca’s area
Inferior frontal gyrus of dominant hemisphere
34
Functions of frontal lobe
Personality Initiative Judgement Insight Control of emotions Contra lateral motor function
35
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
36
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
37
Areas and functions of the occipital lobe
Primary visual area
38
What determins level of consiousness?
Activities of cerebral cortex and the reticular activating system
39
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
40
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
41
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
42
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
43
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
44
Where is short term explicit memory processed
Hippocampus
45
Functions of the basal ganglia
Movement control and posture control
46
Which side of the body does the left cerebellar hemisphere control
Left! Ipsolateral not controlateral
47
Functions of cerebellum
Gait and balance
48
Which cranial nerves have the nuclei outside of the brain stem
I and II
49
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
50
What are the metabolic requirements of the brain % Cerebral blood flow
20% basal oxygen 25% basal glucose 700ml/min cerebral blood flow (around 14%)
51
Where in the brain receives most blood flow
Grey matter receives around 5x that of white matter
52
What is cerebral perfusion pressure e
CPP = MAP - ICP - Venous pressure
53
What factors control cerebral blood flow
Pressure auto regulation Flow metabolism coupling PaO2 PaCO2
54
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
55
What is pressure auto regulation of cerebral blood flow?
As MAP increases cerebral vasculature constricts and viva versa
56
What is the effect of chronic hypertension on cerebral pressure auto regulation
Shifts curve to right (maintains in higher range)
57
What is the effect of voletile anaesthetics on cerebral auto regulation
Dose dependant vasodilation of cerebral vessels impairing auto regulation.
58
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!
59
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
60
Why does co2 increase cerebral blood flow
Increased h+ As ph compensated for with time then cerebral blood flow returns to normal
61
Effect of oxygen on cerebral blood flow
Little change in physiological range but when PaO2 <6.7 or 92% then there is some vasodilation
62
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.
63
Spinal cord end point at birth and adult hood
Birth lower border of l3 Adult l1/2 gap
64
Where is the spinal cord enlarged in diameter, why
Cervical and lumbar corresponding to brachial and lumbosacral plexuses
65
Spaces and potential spaces around the spinal cord
Subarachnoid space Subdural space - potential Extradural space
66
What traverses the subarachnoid space in the spine
3 incomplete trabeculae , 1 posterior subarachnoid septum and bilateral ligamentum denticulatum
67
What are the boundaries of extramural space around the spine
Between dura and spinal canal extending from foramen magnum ending at sacral hiatus
68
Contents of extradural space around spine
Lymphatics, fat, vasculature, Includes vein outs plexus of Bateson communicating between pelvic and cerebral veins
69
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
70
What are the gaps in the shape of the spinal cord in cross section
Anterior median fissure Posterior median sulcus
71
Where is csf located in the spine
In the sa space In the central canal
72
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
73
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
74
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
75
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
76
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
77
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
78
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.
79
Effect of hemisection of spinal cord
Ipsolateral loss of muscle power, fine touch, pressure and joint/vibration sense Contralateral pain and temperature loss
80
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
81
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
82
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
83
What connects anterior and posterior arteries of the spine
Vasa coronae
84
What is the main derivation artery of the anterior spinal artery
The arteria radicularis magna
85
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
86
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
87
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)
88
What are intrafusal muscle fibres
Form muscle spindle
89
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.
90
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.
91
What do golgi organs sense
Muscle tension Detect stretch and provide inhibitory feedback to prevent muscle damage
92
Main function of pre motor cortex
Postural adjustment at the beginning of voluntary motion
93
What is the function of the supplemental motor area of the cortex
Planning of complex movements
94
How are motor signals passed to the spinal cord
Directly through corticospinal tract Indirectly via accessory pathways through cerebellum, basal ganglia and brainstem nuclei
95
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
96
Parts of basal ganglia
Caudate nucleus Putamen Globes pallidus Subthalmic nucleus Substantia nigra
97
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.
98
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
99
Where is csf produced
70% in choroid plexuses of ventricles
100
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
101
How does ICP effect csf volume
No effect on production but increased ICP increases with increasing pressure
102
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
103
Why do large molecules not enter the csf
Tight junctions between endothelium of cerebral capiliaries
104
What agents easily pass the bbb
Water Co2 Oxygen Ions Lipid soluble molecules such as voletile anaesthetics.
105
Total csf volume Amount produced per day in typical adult
150ml 550ml
106
Normal ICP values
5-15mmHg
107
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%
108
How can high ICP cause damage
Direct pressure of brain tissue Distortion and herniation of intercranial contents
109
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.
110
Autoregulatroy Compensatory mechanisms for increased intercranial contents volume
Reduction in csf volume Reduction in cerebral blood volume Cerebral vasoconstriction Increased arterial pressure
111
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
112
What can cause realised jvp
Jv obstruction Increased interthoracic pressures Raised cvp Head down position
113
Outer layer of the eye
Sclera with transparent cornea
114
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:
115
Which muscles cause what pupillary changes
Iris muscles Constriction of circular muscles cause constriction Constriction of radial fibres cause dilation
116
Terms for pupillary constriction and dilatation
Constriction - miosis Dilatation - mydriasis
117
Which muscle controls lens accomodation
Ciliary muscle via suspensory ligaments
118
What is the blood supply to the photoreceptive cells of the eye
From the choroid, not the vessels on the retina surface
119
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
120
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
121
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
122
Effect on vision of a lesion to the optic nerve
Loss of vision in one eye
123
Effect on vision of a lesion to the optic chiasm
Bitemporal hemianopia (damage to decussating fibres only)
124
Effect on vision of a lesion to the optic radiation
Homonymous hemianopia (effecting opposite side of vision to side of lesion)
125
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.
126
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
127
What fills the canals of the cochlea
Scala media filled with endolymph Scala tympani and vestibuli with perilymph
128
Where are sound receptors located in the inner ear
Organs of corti located on basilar membrane in scala media
129
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
130
Where are most taste buds
Papillae at back of tongue
131
How long is the t1/2 of taste cells
2 weeks
132
Four taste modalities
Sweet sour salt bitter
133
Innervation of taste buds
Chorda tympani (anterior 2/3) - branch of facial nerve Glossopharyngeal (posterior 1/3) Greater petrosal (soft palate) - branch of facial
134
Where do the nerves supplying taste buds run too
Tractus solitarious in medulla then thalamus and cortex
135
What is special about olfactory cells
Only neuronal cells in body to robe replaced continually by division of underlying basal cells
136
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
137
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.
138
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)
139
Which nerves contribute to PNS outflow?
CN III, VII, IX, X S2,3,4
140
What percentage of total PNS outflow is accounted for by the two vagus nerves
75%
141
Location of parasympathetic ganglia
In the effector organs thus short postganglionic neurones
142
Neurotransmitters for ANS preganglionic fibres
Ach
143
Neurotransmitters for PNS postganglionic neurones
Ach Rarely vasoactive intestinal polypeptide
144
Neurotransmitter for postganglionic SNS neurones
Noradrenaline Except sweat glands, piloerector muscles and some blood vessels (those supplying skeletal muscle) that use ach
145
Release from adrenal medulla on stimulation by sns with percentages
Adrenaline 80% Noradrenaline 20%
146
Main receptors activated by noradrenaline
Alpha
147
Main receptors activated by adrenaline
Alpha and beta
148
Type of ach receptor in ans ganglia
Nicotinic
149
Type of ach receptor at PNS effector site (postganglionic PNS synapse)
Muscurinic
150
Types of muscurinic ach receptor and locations
M1 - CNS M2 - heart M3 - exocrine glands and vascular endothelium
151
What is a nicotinic ach receptor (receptor type)
Ligand gated ion channel
152
What is a muscurinic ach receptor type
G protein linked
153
Type of ach receptor at skeletal muscle
Nicotinic
154
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
155
Alpha 2 receptors found at
Smooth mucslce of some blood vessels Pancreatic islets for insulin (beta cells) Pancreatic acinar cells
156
Beta one receptors found at
Cardiac muscle Juxtaglomerular cells in kidneys Posterior pituitary Adipose tissue
157
Beta 2 receptors found at
Airways Ciliary muscles of eye Hepatocytes of liver
158
Beta 3 recptors found at
Brown adipose tissue
159
Components of limbic system Functions
Hypothalamus - endocrine function, homeostasis Amygdala - behavioural response to stimuli Hippocampus - memory All - behavioural, emotion
160
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
161
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
162
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
163
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
164
Effects of oxytocin
Milk ejection Uterine contraction
165
How is thirst sensation mediated
High osmolality and low volume detected by hypothalamus Triggers vasopressin release and RAAS
166
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