Neurology anatomy Flashcards
What is neuron?
- individual cell
- elongated
- excitable tissue
- detect and transmit messages as nerve impulses from one part of the body to another (dendrite receive information/ axon transmits information)
neuron vs nerve
nerve:
- bundle of neuronal axon in the PNS
- no cell body
neuron:
- individual cell with a cell body
- found in both CNS and PNS
_ in CNS, a bundle of axon called a tract
What is nerve?
- A nerve is a visible collection of neuronal fibers held tgt by connective tissue (only in PNS)
Autonomic system include which 2 categories?
Sympathetic nervous system: activated in critical situations
Parasympathetic: activated at rest
What does a single system comprise of?
CNS: brain to spinal cord
PNS: sensory and autonomic nervous system
what are the three layers of meninges?
- dura matter
- tough outer layer
- in the cranium adhered yo periosteum
- in the spinal cord
- bilamina- periosteal layer and meningeal layer (venous sinus) - arachnoid matter
- blood vessels and CSF
- arachnoid trabeculi
- subarachnoid space
- cisterna magna (clinical site to collect CSF) - Pia matter
- adhered to surface of the neuraxis
How many ventricles in central nervous system?
4 ventricles:
- lateral ventricles (L & R)
- third ventricles
- fourth ventricles
What is choroid plexus?
- produce CSF (formed by ultrafiltration of blood plasma and epithelial cell secretions)
- vascular invaginations of pia mater into the ventricles (3rd and 4th ventricles: roof/ lateral ventricle: floor)
Describe cerebrospinal fluid (CSF).
- clear, colourless fluid
- composition: protein, glucose, chloride and sometimes lymphocytes
- found in ventricles of brain/ subarachnoid space/ central canal of spinal cord
- pressure is kept constant by drainage: venules subarachnoid space/ venous sinuses of the brain/ lymphatic vessels of the spinal nerve roots.
what is the function of CSF?
- cushions and protects the CNS
- provides buoyant support for the brain
- nourishes CNS
- removes metabolites from CNS
- pathway for pineal secretions to reach the pituitary gland.
How many pairs of cranial nerves in peripheral nervous system?
12 pairs of cranial nerves
list the 4 peripheral receptors.
- exteroceptors (temp, touch)
- interoceptors
- proprioceptors (muscle stretch, tension, position, joint movement)
- nocioceptors (Pain)
List the 12 cranial nerves
CN I Olfactory nerves
CN II Optic nerves
CN III Oculomotor nerve
CN IV Trochlear nerve
CN V Trigeminal
CN VI Abducent nerve
CN VII Facial nerve
CN VIII Vestibulocochlear nerve
CN IX Glossopharyngeal nerve
CN X Vagus nerve
CN XI Accessory nerve
CN XII Hypoglossal nerver
state the of afferent (sensory) pathway of peripheral nervous system.
- sensory information travels from the sensory receptors to CNS
- ascend in peripheral fibers to spinal cord, then spinal tracts to brain
- pathway can be (i) somatic: interacting with external environment or (ii) visceral: relating to internal environment.
- integration of sensory information occurs in the CNS (e.g. parietal lobe in the cerebral cortex has the somatosensory center: the primary receptive area for touch and proprioception
state the efferent (motor) pathway of peripheral nervous system.
- information travels from the CNS motor cortex/ cerebellum to efferent organs
- descending in upper motor neuron (UMN) in CNS to Lower motor neurons (LMN) in the PNS via peripheral nerves
- these pathways can be: (i) somatic: to skeletal muscle (voluntary) or (ii) visceral: to cardiac muscle, glands (involuntary)
- the efferent organ performs the reaction or response to the stimulus
where is the location of sympathetic nervous system?
thoracolumbar region
where is the location of craniosacral region?
craniosacral region
example of parasympathetic.
- constricts pulpil
- vasodilation
- stimulates salivation
- constricts bronchi
- inhibits heart
- stimulate gallbladder
- stimulate digestive activity
- contracts bladder
What can senses be subdivided in?
- somatic sense
- skin (pain, touch, temp), muscle, tendon and joint
- general somatic afferent fiber - visceral sense
- glands, viscera, blood vessels
- general visceral afferent fibers - special sense
- vision, hearing, smell and taste
- special somatic afferent fibers (vision, hearing, balance)
- special visceral afferent fibers (taste and smell)
describe the pathway of spinothalamic tract.
getting info from the spine up to thalamas. then to the primary somatosensory cortex
What is the 2 categories that can access the function of receptor?
- Acuity
- simple test of sensory nerve function
- the ability to discern two nearby objects touching the skin are truly two distinct points, not one
- determined by the density of receptors - Dermatomes
- an area of skin supplied by nerve from a single spinal root
- they overlap and usually slope ventrocaudally
- named after its spinal nerve
- clinically useful in determining site of spinal damage
what is the 2 main pathways for conscious sensory afferent nervous system?
- spinothalamus pathway
- medial lemniscus pathway
State the 2 sub-divided pathways under the spinothalamic pathway.
- Lateral spinothalamic pathway
- sensation of pain and temperature - Anterior spinothalamic pathway
- sensation of crude touch, pressure, tickling and itching
State the routes of the spinothalamic pathway.
- First order neuron: starts at the sensory receptor
- Secondary order neuron: starts at the dorsal horn of spinal cord
- Third order neuron: starts at thalamus and terminates at cerebral cortex, contralateral hemisphere.
Which 2 areas do medial lemniscus pathway associated with?
Relays sensation of fine touch, proprioception, vibration and stereigenesis
- Fasciculus cuneatus
- signals upper limb: T6> - Fasciculus gracilis
- signal lower limb: <T7
State a medial lemniscus pathway
- First order neuron: start at sensory receptor
- second order neuron: starts at medulla
- third order neuron: starts at medulla and terminates at cerebral cortex, contralateral hemisphere.
What does unconscious sensory pathway transmit info for?
- muscle tone
- posture
- coordination
Where does unconscious sensory pathway terminate?
ipsilateral cerebellum (terminate on the same side)
what is the two pathway of unconscious sensory pathway in afferent sensory nervous system?
- Dorsal spinocerebellar tract
- lower limb information L3-L8 (ipsilateral cerebellum)
- Cuneocerbellar tract T3>: upper limb information (ipsilateral cerebellum) - Ventral spinocerebellar tract
- Spinal interneurons (REFLEXES)
- Double cross the SC to entre on ipsilateral side cerebellum
- Involved in voluntary movement, important cerebellum has access to this information for coordination of movement.
How does proprioception of different areas travel to the brain?
- Neck, trunk, limbs via:
- spinal nerve: dorsal root
- Spinal cord: dorsal and ventral funiculi - Head, its muscle and joint via:
- CN VII vestibulocochlear nerve
- CN V Trigeminal nerve
What is the pathway of conscious proprioception?
- afferent nerve fibers enters spinal cord
- ascending signal to cerebral cortex (contralateral side)
- descending signal to spinal nerve
- efferent nerve fibre
*e.g. Medial lemniscus pathway (secondary neuron decussates to the contralayeral side)
What is the pathway for unconscious proprioception?
- afferent nerve fibers enter spinal cord
- synapse to somatic efferent neuron (reflex arc)
- ascending signal to ipsilateral side cerebellum (requires 2 neurons)
What does cerebellar ataxia affect?
impacting cerebellum/ muscle coordination/ balancing
how does cerebellum integrate in coordination?
- input via:
(i) vestibular
(ii) visual
(iii) proprioception/ somatosensory
(iv)motor efference copy signals - output via:
(i) thalamus
(ii) hippocampus
(iii) super colliculus - to
(i) motor cortex
(ii) posterior parietal cortex
Lesion localization in cerebellum
- lesions to the vermis result in truncal ataxia
- lesions to the flocculonodular lobe results in eye movement abnormalities
- lesions to cerebellar hemisphere results in ipsilateral ataxia
Describe enteric nervous system (ENS)
- embedded in lining GIT
- operates independently of the brain and SC
- consists of 2 plexuses (ganglia):
(i) myenteric (Auerbach’s): inner/ outer layer of muscularis externa - increase tone and peristalsis
(ii) subsacral (meissner’s): submucosa- sensory nerve endings signal both layers of enteric plexus - short reflexes: respond to digestive movement and chemical changes (release acid in the stomach)
- long reflexes: connect ENS to CNS respond to food, emotion or danger (e.g. mastication of food stimulates secretion of gastric acid)
What peripheral nerves are involved in micturition?
- Pudendal nerve (somatic)
- going to urethral external muscle - Hypogastric nerve (sympathetic)
- detrusor muscle relax
- internal sphincter contract - Pelvic nerve (parasympathetic)
- detrusor muscle contract
- internal sphincter relax/ opening internal sphincter
what is the 2 phase of micturition?
- filling phase
- empting phase
Somatic reflexes vs autonomic reflexes
Somatic reflexes:
- respond to external environment
-simple reflex
- 2 nerves and one muscle (stretch reflex/ spinal reflex)
Autonomic reflexes:
- respond to changes in the internal environment
- Brainstem reflexes: complex functions like heart rate, blood pressure
- Hypothalamic reflexes: homeostasis
Definition of UMN
- the neurons of the brain that control body motor activity
- cell bodies are located in the cerebellum and brain stem
- Entire UMN is confined to CNS
what is the function of UMN?
Tells the LMN what to do
- stimulate or inhibit LMN
- initiation of voluntary movement
- maintenance of muscle tone and support against gravity
- regulation of posture
Definition of LMN
- the neurons that directly innervate the muscle
- cell bodies are located in the ventral grey horn of the spinal cord
What is the function of LMN?
- receive input from UMN
- connects CNS with the muscle (PNS)
- spinal reflexes
UMN dysfunction
- Paretic (weakness) to paralysis
- Gait:
> long strided
> crossing
> scuffing - loss of inhibition
> spacicity
> Hyperreflexia/ hypertonia/ abnormal reflexes
> abnormal posture
> extensor opisthotonos
