Nervous 1 Flashcards
What does somatic and autonomic system supply and their structure
Somatic NS - skeletal muscle -> Movement - Single peripheral nerve - Spinal cord to skeletal muscle Autonomic NS - ALL other tissues -> Homeostasis - Two peripheral nerves - Pre and post ganglionic nerves 1) Parasympathetic - Craniosacral outflow - Ganglia close to target organ 2) Sympathetic - Thoracolumbar outflow - Ganglia close to spinal cord
What movements does the brainstem and corticospinal tract
1) Brainstem - contains circuitry for initiating locomotion and controlling posture
2) Corticospinal tracts - cerebral cortex influence is necessary for control of individual fine motor movements
What are the 3 levels of control of movement
- Alpha motor neurons are the final common path for motor control
- Peripheral sensory input and spinal cord tracts that descend from the brainstem and cerebral cortex influence the motor neurons
- Cerebellum and basal ganglia contribute to motor control by modifying brainstem and cortical activity
What is the difference between lower and upper motor neurons
Lower motor neuron
- Nerve cell body in spinal cord
- Efferents are alpha motor neurons (supply muscle fibres)
Upper motor neuron
- Nerve cell body in higher CNS centre (cortex or brain stem)
- Efferent are in spinal cord
- Efferent synapse on LMN’s or interneurons
What makes a Pyramidal and extra-pyramidal tract and in which animals are they important
PYRAMIDAL -> are cortical in origin
- More important in higher animals
EXTRA-PYRAMIDAL -> are brainstem in origin
More important in animals with less developed brains
What is the difference between a nucleus and a ganglion
Nucleus - a collection of nerve cell bodies inside the CNS
Ganglion - a collection of nerve cell bodies outside the CNS
What are the 3 brainstem descending motor pathways, their origin and what type of tracts
1) Red nucleus -> Rubrospinal tract
2) Vestibular nucleus -> vestibulo-spinal tract
3) Reticular formation - retirculospinal tract
BRAINSTEM pathways are EXTRA-PYRAMIDAL
What are the tracts called that come from the cerebral cortex, what type of tract, where they synapse and pathway
- Corticospinal tracts
- Pyramidal tracts
- Don’t synpase before LMN is reached
- Cortex -> internal capsule -> cerebral peduncles -> medulla
What are the regions of the brain and regions within
1) Forebrain (Prosencephalon)
○ Telencephalon (cerebral hemispheres)
○ Diencephalon (thalamus, metathalamus, epithalamus, subthalamus and hypothalamus)
2) Midbrain (Mesencephalon)
○ Mesencephalon (tectum, tegmentum, cerebral peduncles)
3) Hindbrain (Rhombencephalon)
○ Metencephalon (dorsal: cerebellum and ventral: pons)
○ Myelencephalon (medulla oblongata)
What are the functional jobs of the forebrain, brainstem and cerebellum (hindbrain) and which cranial nerves where
1) Forebrain
- Perception of sensory input
- Initiation of motor activity
- Integration/association of information
- Cranial nerves I and II
2) Brainstem - midbrain, pons, medulla oblongata
- Thoroughfare for ascending and descending information
- Major upper motor neuron nuclei for movement
- Cranial nerves III and IV
- Consciousness
3) Cerebellum (hindbrain)
- Thoroughfare for ascending and descending information
- Major upper motor neuron nuclei for movement
- Coordination of muscle activity
- Cranial nerves V to XII
- Regulation of many organs functions (cardiovascular, respiratory, gastrointestinal)
List some targets for drug action of neurotransmission
1) Action potential in presynaptic fibre
2) Synthesis of transmitter
3) Storage of transmitter
4) Metabolism of transmitter
5) Release of transmitter
6) Reuptake of transmitter
7) Degradation of transmitter
8) Binding of transmitter to receptor
9) Receptor induced change in ionic conductance
What are the 4 concepts of neurotransmission and give examples for the final one
1) Co-transmission
2) neuromodulators
2) neurotrophic factors
4) fast and slow neurotransmitters
Fast - amino acids - glycine or acetyl choline - relay systems (sensory and motor)
Slow - neuropeptides - substance P, endorphins - global functions (arousal, memory, appetite)
What is derived from the ectoderm, medoderm and endoderm
Ectoderm - Epithelium and derivatives - CNS and PNS (neural plate) - Neural crest Mesoderm - Connective tissues, muscle - Kidney and gonads - Blood vessels, lymph organs Endoderm - Epithelium of gut, lungs, bladder
Why is the notochord important
- provides transient support and persists as the nucleus pulposus of the intervertebral disc
- REQUIRED for the development of the neural tube
What are the 6 steps in the neural tube formation
- neuroectoderm is formed by proliferation of ectoderm dorsal to the notochord
- neural plate is a thickened plate of neurectoderm
- neural groove forms in the dorsal aspect of the neural plate
- neural folds are lateral folds which rise up either side of the neural groove.
- neural tube is formed when the lateral folds fuse dorsally.
- neural canal is the central canal formed by closure of the neural tube
What pathways come from the dorsal horn
DORSAL ROUTE OF THE SPINAL NERVE
- General, somatic, afferent (sensory) -> (muscle, voluntary movement)
- General, visceral, afferent (sensory) -> (involuntary from the organs)
What pathways come from the ventral and intermediate horns and where isn’t the intermediate horn present
VENTRAL ROUTE OF THE SPINAL NERVE
- General, somatic, efferent (motor) -> muscle voluntary movement back out to the body
INTERMEDIATE ROUTE OF THE SPINAL NERVE
- General, visceral, efferent (motor)
- not present in the cervical spinal cord
What are the 3 layers of the neural tube
1) Germinal layer - most medial layer
2) mantle layer - forms the grey matter, middle layer except where extenral in cerebral hemispheres
3) marginal layer - forms the white matter, outer layer except in cerebral cortex
What is the sulcus limitans and what does it demarcate
longitudinal groove that develops in the lateral wall of the neural tube extending from the midbrain to the caudal spinal cord
- Marks the separation between the alar and basal plates
- Alar plate - dorsal - primary sensory
Basal plate - ventral - primary motor
Emrbyonic development of the vertebrae what do somites form and then what occurs
somites form dermatomes, myotomes and sclerotomes
Sclerotomes then split and the nerves from developing spinal cord grow through these splits towards the myotomes
sclerotome divides into cranial and caudal halves, which separate and fuse with the adjacent sclerotome halves
Each complete vertebrae is a product of fusion of four sclerotomes
What forms the dorsal and ventral median fissure of the spinal cord and the dorsal and ventral grey columns
- Dorsal median septum - the dorsal growth of the two halves of the alar plate forms a vertical wall between the two dorsal halves of the spinal cord
- Ventral median fissure - the ventral growth of the two halves of the basal plate forms a cleft between the two ventral halves of the spinal cord
- Dorsal grey columns which are formed from the alar plate Neuroblasts
- Ventral grey columns which are formed the basal plate Neuroblasts
What 2 cellular migrations create the cerebellum
1) Differentiating mantle cells (no longer dividing) form
- Purkinje cells - early in embryonic life so they are susceptible to teratogens
- Neurons of the cerebellar nuclei
2) Dividing germinal cells migrate to the surface of the cerebellum to form the external germinal layer
- Granule cell layer
- Stellate cells of the molecular layer
Midbrain development what does the neural tube form and what are the 3 areas of development
- Neural tube forms the mesencephalic aqueduct
○ Three areas form during development
§ Alar plate forms the tectum
§ Basal plate form the tegmentum
§ Peduncular area - area of the cerebral peduncles is formed by caudally growing neuronal processes from the cerebral cortex
What creates the ventricles and what connects them
The neural tube enlarges to create the ventricles
Interventricular foramina connect third to lateral ventricle on each side and the mesencephalic aqueduct connects the third and fourth ventricle
What are the 2 main double layer folds of dura and what do they demarcate
1) Falx cerebri - fold in longitudinal fissure between two cerebral hemispheres, from ethmoid bone to osseous tentorium
2) Tentorium cerebelli - separating cerebral hemispheres from the cerebellum
What are the 3 main arteries that supply the spinal cord
1) Two dorsolateral arteries
2) ventral spinal artery -> continues as basilar artery at level of foramen magnum
3) radicular arteries - each intervertebral foramen
What are the 3 arteries that supply the base of the brain and what is the main area in which they combine
1) internal carotid (left and right)
2) Basilar artery
3) Rete mirabile - present in ruminants, pigs and cats
- rostral rete - originates from maxillary and internal caroid arteries
- caudal rete - orginates from the vertebral and occiptal
Circle of Willis - left and right internal carotid and basilar artery
What are the arterial supply of cerebral and cerebellar blood supply
Cerebral blood supply - From the circle of Willis 1) Rostral cerebral artery 2) Middle cerebral artery -> largest vessel supplying the brain 3) Caudal cerebral artery -> arises near the oculomotor nerve Cerebellar blood supply - Rostral cerebellar artery - Caudal cerebellar artery
What is the main venous plexus of the spinal cord
Internal vertebral venous plexus consists of paired venous sinuses on the floor of the vertebral canal and veins that arc over the spinal cord
List 3 venous sinuses and the 3 main veins that drain the brain
1) Dorsal sagittal sinus
- Within the flax cerebri
2) Basilar sinus
- Drain into basilar sinus (base of spinal cord)
3) Cavernous sinus
- On the floor of cranial fossa caudal to orbital fissure
Main veins draining
1) Vertebral vein
2) Internal jugular vein
3) Maxillary vein
What is the main CSF cisterns
Cerebellomedullary cistern - lies in the angle between the caudal cerebellum and the medulla oblongata
○ Most common area to collect CSF for investigation
What are the 2 areas of production of the CSF and which area is the primary site
1) Choroid plexi
○ Primary site of production, ultrafiltration by blood plasma and by active transport
○ Tangles network of blood vessels protruding into the ventricles
2) Brain parenchyma and ependymal cells
Describe the movement of CSF and 3 reasons it gets blocked
Rostral out of the lateral ventricles -> caudal through ventricular system -> spaces through roof of 4th ventricle through lateral apertures -> into sub subarachnoid space -> caudally along the spinal cord
Blocked
1) Through mesencephalic aqueduct
2) Lateral apertures aren’t large enough - less likely
3) Not being reabsorbed properly
What are the 2 main places CSF is absorbed
1) Reabsorbed by arachnoid villi that protrude through main sinuses - venous sinus
- Acts like a one-way valve so CSF pressure is greater than venous pressure, if other way around the villi will collapse
2) Some reabsorbed via lymphatics and veins around the brain and within the meninges
What are the 3 main functions of CSF
1) Physical protection
- Buffer against pressure changes within the CNS
2) Chemical protection
- More stable chemically than blood plasma
- Allows increased regulation of the neuronal environment
- CSF pH directly influences the function of the medullary respiratory centre
3) Nourishment
- May transport nutrients between the blood and the brain
- May transport neuroendocrine substances and neurotransmitters
What are the 12 cranial nerves
I) Olfactory II) Optic III) Oculomotor IV) Trochlea V) Trigeminal -> 3 branches -> 1. Ophthalmic 2. Maxillary 3. Mandibular VI) Abducens VII) Facial VIII) Vestibulocochlear IX) Glossopharyngeal X) Vagus XI) Accessory XII) Hypoglossal
CNI name, function, where exit from skull and brain
Olfactory nerve
Function - olfaction, pheromone reception - via vomeronasal nerves
STAYS WITHIN SKULL - cribriform plate
Forebrain - telencephalon
CNII name, function, where exit skull and brain
Optic nerve
Vision
Optic foramen
Forebrain - diencephalon
CNIII name, function, where exit skull and brain
Oculomotor Ocular movement 1. ventral, medial and dorsal recti, venral oblique, levator palpebrae muscles 2. parasymapthetic control of the iris Pupillary light reflex Orbital fissure Midbrain - mesencephalon
