Neuroanatomy Flashcards
What is the CNS?
Central control centre of the body
What is the PNS?
collects info from environment and produces the changes required within the body
What is the ANS?
communicates with internal organs
What is a neuron?
The neuron is the major functional unit of the nervous system.
• They are electrically active cells
What are the 4 parts of the neurone?
- Cell body: Contains at least 3 organelles
for cellular function: nucleus, endoplasmic reticulum (forms part of the vascular delivery to cells), golgi apparatus (processes proteins for energy). - Dendrites: information receiving area of cell
- Axon: information transmitting area of cell body
- Presynaptic terminal: transduction of electrical impulses into chemical signals for transmission to adjacent cells
What are the three types of neurones?
- Pseudounipolar cells
- Bipolar cells
- Multipolarcells
What are nerves made up of?
- Hundreds of thousands of neurons are accumulated together to form nerves.
- Neurons are short and will not travel the full length of the nerve. This aids in speed of signalling
What are the supporting cells of the nervous system?
Ependymal
• Ependymal cells: line the ventricular surfaces of the canals of the CNS. Involved in cerebrospinal fluid production
What are the supporting cells of the nervous system?
Glial
Glial Cells
• supportive cell in the central nervous system.
• Glial cells do not conduct electrical impulses.
• The glial cells surround neurons and provide support for them and insulation between them. Glial cells are capable of extensive signalling in response to a diversity of stimuli. Bidirectional communication exists between glial cells and neurons, and between glial cells and vascular cells.
What are the supporting cells of the nervous system?
Schwann
Oligodendroglial cells: some of these cells are known as Schwann cells.
They are involved in myelination of axons and local nutrient support.
What are the supporting cells of the nervous system?
Astrocytes
Astrocytes: form a structural and enzymatic barrier between the
nervous system and the rest of the body.
What are the supporting cells of the nervous system?
microglial
Microglial cells: major cellular defence system of the nervous system. Phagocytotic cells.
What are nerve impulses?
- Stimuli is received at the dendrites
- Converted into a nerve impulse (action potential)
- Conducted along the axon
- To the presynaptic terminal and converted into a chemical signal
What are the properties of neurone cell membranes that enables maintenance of membrane potential?
- Semi permeable cell membrane
- Selective regulation of movement of charged ions across cell membrane
- Presence of an energy dependant (active) sodium/potassium pump in the cell membrane
• Sodium and potassium ions can be moved across the cell membrane, even against their concentration gradients, although this requires energy.
• The controlled influx or efflux of sodium, potassium and chloride ions into and out of the neuron results in the generation of the action potential.
What are the events at a synapse?
- action potential arrives
- Ca2+ permeability and influx increased
- release of transmitter by exocytosis of vesicles
- reaction of postsynaptic receptors
- activation of synaptic channels- produces postsynaptic potential
What are the three methods of classification?
- Topographicalclassification
- Classification based on direction of impulse travel
- Functional classification
What is topographical classification?
split into CNS and PNS
What is classification based on direction of impulse travel?
can relate to individual neurone or fascicles
large nerves can have both afferent and efferent qualities
What is functional classification?
SOMATIC – locomotor function - voluntary control
- Spinal nerves
VISCERAL – regulation of internal function
- Involuntary control - autonomic
What are the divisions of the brain?
forebrain
brainstem
cerebellum
What does the forebrain split into?
Telencephalon
• CEREBRAL CORTEX Regulates behaviour, sensation, motor
activity, conscious perception, proprioception
• WHITE MATTER Contains ascending and
descending sensory and
motor neurons
• BASAL NUCLEI Regulation of muscle
tone and initiation of voluntary motor activity
Diencephalon
• THALAMUS, SUBTHALAMUS, METATHALAMUS, HYPOTHALAMUS
• Sensory integration centre, relays info to cerebral cortex
• Control of endocrine and autonomic function
• Root of cranial nerves I (Olfactory) and II (Optic)
• Emotion and behaviour
What is the brainstem?
- Regulator centre for consciousness, cardiovascular system and breathing
- Links cerebral cortex to the spinal cord via ascending and descending motor pathways
- Root of 10 pairs of Cranial Nerves
What is the cerebellum?
• Controls the range and force of movements
• Does not initiate motor activity
• Coordinates muscle activity
• Smoothes movements initiated by upper motor neurons
• Close association between cerebellum, brainstem and
vestibular nuclei in regulation of balance and muscle tone.
• Inhibitory effect on urination
What is the spinal cord made up of?
- Grey matter
- White matter
- Ventral root
- Dorsal root
- Spinal Ganglia
- Spinal nerve
- Pia Mater
- Arachnoid
- Dura Mater
ascending and descending signals
What is spinal cord segmentation?
- A spinal cord segment is a portion of the spinal cord which gives rise to one pair of spinal nerves
- Neurological lesion localisation refers to the spinal cord segments
- Innervation of the body occurs in a segmental fashion. Each cutaneous region of the body (dermatome) and group of muscle fibres (myotome) is innervated by one or more spinal segments
What are meninges (CNS)?
- The brain and spinal cord are surrounded by three continuous membranes and two potential spaces:
- Outermost membrane – Dura mater
- Epidural space
- Middle membrane – arachnoid
- Subarachnoidspace
- Inner membrane – Pia Mater
What are the functions of Cerebrospinal fluid?
• Functions of Cerebrospinal Fluid (CSF):
- Support and cushioning of the brain and spinal cord
- Permits variations in blood volume within the cranium
- Maintains a constant fluid environment for nervous tissue
- Nutrition of the Nervous System
- Movement of Neurotransmitters
- Regulation of respiration
How is the PNS structured?
- Peripheral nerves contain both sensory and motor fibres.
- Motor axons originate in the ventral horn of the spinal cord, or grey matter of the brain stem.
- Cell bodies of sensory axons are located in the dorsal root ganglion
- Peripheral nerves leave the vertebral column via the intervertebral foraminae
What are ascending signals in the spinal cord and what can damage here lead to?
- Ascending
- Noxious (harmful) stimuli
- Nociception (perception of pain)
- Nociceptors (pain receptors/ PNS)
- Detect mechanical, thermal or chemical changes
- Skin, periosteum, joint surfaces
• Damage to sensory neurons will result in lack of sensation or loss of proprioception or increased sensation and pain
What are ascending signals in the spinal cord?
- Descending - Motor tracts & motor neurons
- Upper motor neurons (CNS)
- Originate in higher levels of CNS
- Regulate and influence activity of motor cells that innervate muscles in periphery
- Lower motor neurons (PNS)
- Leave CNS
- Innervate target structures in periphery
What does the PNS neuromuscular junction consist of?
- An axon terminal
- Synaptic cleft
- End plate region of skeletal muscle fibres
- The NMJ is a transducer: electrical – chemical – electrical signals
What occurs at the PNS neuromuscular junction?
• 1. Action potential in motor nerve • 2. Influx of calcium ions • 3. Ca2+ binds with neurotransmitter vesicles • 4. Neurotransmitter - Acetylcholine (Ach) released into synaptic cleft • 5. Ach binds with receptors on myofibril membrane • 6. Influx of Na+ into myofibril • 7. Action potential generated
Where is the PNS located?
- Peripheral nerves also have topographical classifications.
- Cranial nerves
- Spinal nerves
- Brachial plexus
- Lumbosacralplexus
What are the cranial nerves of the PNS?
- 12 nerves
* Not all contain both sensory and motor fibres.
What are olfactory nerves?
• Olfactory (I)
• Smell (food, hand)
• Irritation of nasal
mucosa also tests trigeminal
What are optic nerves?
• Optic (II) • Menace or blink • Lesions of eye and optic nerve ipsilateral blindness • Lesions of optic tracts and cortex contralateral blindness • Cerebellar disease alters menace response • Foals have no menace until several days old
What are oculomotor nerves?
- Oculomotor (III)
- Size and symmetry
- Pupillary light reflex => constriction
- Direct (ipsilateral)
- Consensual(contralateral)
- Reflex within brainstem
- Visual cerebral cortex lesions do not affect reflex
What are oculomotor, trochlear and abducens nerves?
• Oculomotor (III), Trochlear (IV), Abducens (VI)
• Extra ocular muscles
• Strabismus (wall eye)
• Vestibular nystagmus (involuntry movement of the
eye)
• Corneal reflex
eyeball retraction
What are trigeminal nerves?
- Trigeminal (V) • 3 branches
- Mandibular • Maxillary
- Ophthalmic
- Motor to mandibular mastication muscles
- Sensory from all parts of head
- Reaction to stimulation of septum and internal nares aswell as skin (see facial nerve)
What are facial nerves?
- Facial (VII)
- Facial expression
- Ears
- Eyelids
- Lips
- Nostrils
- Lacrimal glands
- Salivary glands
- Clinical signs
- Droopingear
- Ptosis
- Drooping upper lip
- Dropped nostril
What are vestibulocochlear nerves?
- Vestibulocochlear (VIII)
- Cochlear division
- Hearing
- Vestibular division
- Balance
- Vestibular system
- Highercentres
- Cerebellum
• Head tilt • Accommodation Blindfold • Fast phase/head tilt away from peripheral lesion
What are glossopharyngeal, vagus and accessory nerves?
- Glossopharyngeal (IX), Vagus (X), Accessory (XI)
- Sensory and motor innervation of larynx and pharynx
- Swallowing
- Food and water at nostril
- Endoscopy
- Roaring
- Stertorous breathing
What are hypoglossal nerves?
- Hypoglossal (XII)
- Motor nerve
- Tongue
- Symmetry
- Atrophy
- Movement
- Withdrawal
What are the spinal nerves of the PNS?
- Pair of spinal nerves emerge at each vertebral level.
- Eachconsistsof dorsal and ventral root.
Brachial Plexus
Lumbosacral Plexus
