Neuroanatomy Flashcards
What are the 4 types of cutaneous receptors?
Mechanoreceptors, thermoreceptors, nociceptors and pruritoceptors.
What types of hair follicles Afferents are slow adapting and which are fast adapting ?
Slow adapting - Ruffini’s ending and Merkels disk
Fast adapting - Meissner’s corpuscle and Pacinian corpuscle
What are nociceptors named if they respond to all 3 stimuli (thermal, mechanical and chemical)?
Polymodal nociceptors
What is the main stimulus of pruritoceptors?
Chemical (e.g. histamine)
What is ‘Peizo2’?
A type of mechanosensitive ion channel that is responsible for the transduction of mechanical stimuli. They are the main contributor of the mammalian sensory nerve.
What family of channels are used for the transduction of thermal stimuli? Name some examples.
Transient receptor potential (TRP) channels signal various temperature.
- TRPV1: responds to temperature >43oC
- TRPM8: main transducers of non-painful cooling
Where are the cell bodies of primary sensory Afferents located?
Dorsal root ganglion
What type of cells are primary sensory Afferents?
Pseudo-unipolar cells as they have a part in both the PNS & CNS.
What neurotransmitter do ALL primary sensory Afferents use?
The excitatory NT glutamate.
Name and describe the two sub-types of myelinated (A fibres) of primary Afferents.
- Large myelinated (A-beta): larger diameter of 6-12microm and conduct at 35-75m/sec with a low threshold. They are found in both the dorsal horn and medulla.
- Small myelinated (A-delta): smaller diameter of 1-5microm and conduct at 5-30m/sec (I.e. “fast pain”). They are only located in the dorsal horn.
What is the origin and termination of the dorsal column-medial lemniscal pathway (DCML)?
It carries sensory information from tactile sensation, vibration and Proprioception to the sensory cortex.
For the dorsal column-medial lemniscal pathway, where to the upper and lower limbs travel through?
Upper limbs (>T6) fibres travel in the faciculus cuneatus of the medulla oblongata (lateral). Lower limbs (
What order neurones decussate in the dorsal columm-medial lemniscus pathway?
Second order neurone decussate
What is the difference between the anterior and lateral spinothalamic tracts?
The type of sensory information they carry:
Anterior - crude touch and pressure
Lateral - pain and temperature
What are the types of glial cells found in the PNS?
Schwann and satelitte cells.
What type of glial cells are found in the CNS and what is the embryological derivative?
Macroglial (astrocytes and oligodendrocytes)- ectoderm
Microglial - mesoderm
What type of glial cells are affected by multiple sclerosis?
Oligodendrocytes
How much do astrocytes contribute to total brain volume?
20-50%
Name the 2 types of astrocytes and where they can be found.
- Fibrous astrocytes: present in white matter
* Postoplasmic astrocytes: present in grey matter
What 2 processes are involved in forming a glial scar?
Hypertrophy (I.e. enlargement of tissue) and proliferation.
What component of an astrocytes is responsible for initiating changes in Vasculature diameter (I.e. vasodilation)?
The perivascular end feet receive signals from astrocytes to initial vasodilation in the cerebral capillaries.
What are the 3 types of microglial cells?
- Perineuronal: close to neurones
- Parenchymal: in the chymal sending signals in the ECM.
- Perivascular: near the cerebral blood supply
Describe the structure of cerebral arteries’ histology including any endothelial junctions present.
Cerebral capillaries are lined with squamous epithelial cells in the lumen and are lined with a continuous basement membrane. The endothelial cell’s are joined together by: zonula occludens, tight junctions and zonulae adherens. These junctions create and impermeable barrier between the capillary lumen and brain tissue.
What is responsible for dilation and construction of intracerebral arterioles?
Vascular smooth muscle cells
What is the main difference between the BBB and the blood-CSF barrier?
The blood-CSF barrier contains genes treated endothelial cells.
What cells produce CSF?
Chorodial epithelial cells
What is the corticospinal/ pyramidal tract responsible for coordinating?
The processing of voluntary, discrete and skilled movements.
What structures protect the CNS?
Skull, vertebrae and meninges.
What type of receptors do Afferents fibres of the somatic and autonomic nervous system stimulate?
Nicotinic ACh receptors.
What forms a mixed spinal nerve?
The combination of the dorsal root (sensory Afferents fibres) and ventral root (motor efferent fibres).
Where do the preganglionic fibres of the sympathetic and parasympathetic nervous system arise from?
- sympathetic: T1-L2
* parasympathetic: brainstem & S2-S4
Where does the hypogastric plexus carry impulses to?
To the pelvis and lower abdomen.
Where does the splanchic nerves carry impulses to?
The viscera.
What carries the impulses to the thorax and upper abdomen?
The vagus nerve (CNX)
Where are the sympathetic efferent axon endings located in the spinal cord?
The intermediolateral column
What neurotransmitters to the pre- and post- ganlionic fibres use in the ANS?
All fibres use ACh except the postganglionic fibres of the sympathetic nervous system that use noradrenaline (NA)
What nerves are not apart of the sympathetic chain (I.e. do not synapse there)
The splanchnic nerves
Name 2 parasympathetic ganglions.
The ciliary and optic ganglion.
What plexi innervates the submucousa and tunica muscularis of the GI tract?
Submucosa: submucous plexus (Meissner’s plexus)
Tunica muscularis: myenteric plexus (Auerbach’s plexus)
What structures are involved in the basal ganglia? (7)
Caudate nucleus, putamen nucleus, lent inform nucleus (putamen and globes pallidus), amygdala, claustrum, substantia nigra and subthalamic nucleus.
What fibres connect the subthalamic nucleus and globes pallidus?
Subthalamic fasciculus
Describe the sub-components of the substantia nigra.
- reticulata: fibres are further away from each other
- compacta: fibres run relatively close to each other; this area makes the inhibitory NT dopamine that plays an important role in the main output of the basal ganglia - striatal pathway
What 2 types of neurones are found in the striatum and what neurotransmitter do they use?
- spiny projection neurones - GABAergic inhibitory (90%)
* interneurones - Cholinergic excitatory (10%)
What are the 2 main areas in the brain that are associated with processing and producing language?
- Broca’s area: helps produce speech and involved with language expression
- Wernickle’s area: helps understand speech
What results in non-fluent aphasia and describe the condition.
Non-fluent aphasia (Broca’s aphasia) is associated with people who suffer frontal lobe lesions an results in problems with producing speech - words become slurred and broken.
What is global aphasia ?
A combination of both Broca’s and Wernickle’s aphasia
Describe the condition “Wernickle’s aphasia”.
The patient has no trouble producing speech but sentences produced do not make sense and words are jumbled. Patients can also experience difficulty in understanding what others are saying.
What connects Broca’s and Wernickle’s areas?
By a bundle of fibres called the arcuate fasciculus
What 5 areas of the brain are considered a part of the Limbic system?
Thalamus, hypothalamus, amygdala, hippocampus and nucleus accumbens.
What is a function of the nucleus accumbens?
It plays an important role in the reward circuit.
How is the hypothalamus split regionally in regards to the parasympathetic and sympathetic nervous system?
Parasympathetic = anterior and medially Sympathetic = posterior and laterally
Define orexigenic.
An appetite stimulant; can be a drug, hormones, endogenous neuropeptide etc,
Where is considered to be the ‘satiety centre’ in the Limbic system and what occurs when it is stimulated?
The ventromedial hypothalamus is considered to be the satiety centre and when stimulated, food intake decreases as a sensation of adequate intake has been reached.
What is/are regarded as the feeding centre in the Limbic system and what does stimulation lead to?
The paraventricular nucleus and lateral hypothalamus is considered the feeding centre and stimulation leads to an increase of food intake.
What are the 3 main suggested mechanisms controlling appetite and food intake?
- Stomach contractions
- Glucostat (hypoglycaemia/ insulin induces feeding)
- Lipostat
What is the ‘ob-gene’ important for (experiment using knock-out mice)?
The ob-gene is important as it produces a chemical called leptin, which suppresses feeding and increases fat metabolism. BUT too high leptin levels have been linked to obesity.
Where does the hormone leptin have a direct effect on (in the Limbic system)?
The hypothalamus; also can cross the BBB and act upon receptors in the acruate nucleus, VMH, LH & PVN.
What 3 feeding neurotransmitters are found within the hypothalamus?
Neuropeptide Y (NPY), Cholecytokinin (CCK), 5-hydroxy-tryptamine (5-HT)
What effect does the drug fenfluramine have in regards to controlling appetite.?
Fenfluramine decreases 5-HT uptake in the PVN but also increases 5-HT secretion = appetite suppressant
Describe the actions of NPY.
NPY acts on hypothalamic neurones and induces feeding by reducing thermogenesis and increasing fat storage. It acts on 5 receptors in the brain: Y1-Y5.
- Y1: obesity by reduced metabolism and exercise
- Y5: obesity by hyperphagia
What are the neuropeptide Oxerins A&B responsible for?
They regulate wakefulness and energy balance.
What are the main functions of Ghrelin?
It decreases fat oxidation and increases growth via fat & muscle deposition. An antagonist of the peptide is thought to decrease obesity.
What is the action of the drugs tetrahydrolipstatin (orlistat)?
It acts by inhibiting pancreatic and gastric lipase which reduces hydrolysis of triglycerides and decreases fat absorption. This is considered a pharmaceutical method of combating obesity.
What splits the brain into left and right hemispheres?
The longitudinal fissure
What stain can be used on spinal cord sections to produce an ‘opposite image’ (i.e. grey matter appears light and vice versa)?
Weigert stain
Define ‘neuropil’.
A dense network of interwoven nerve fibres, branches and synapses together with glial filaments
Where are the 2 spinal cord enlargements?
The cervical and lumbar regions: this is due to an increase volume of nerve fibres in these areas.
What types of fibres terminate in the substantia gelatinosa?
The primary Afferents sensory neurones for pain and temperature
What levels of the spinal cord contain the nucleus dorsalis?
C8-L3
Name cranial nerves I, IV & X.
I: olfactory
IV: trochlear
X: vagus
Name cranial nerves II, III & VI.
II: Optic
III: oculomotor
VI: abducens
Name cranial nerves V, VIII & IX.
V: trigeminal
VIII: vestibulocochlear
IX: glossopharyngeal
Name cranial nerves VII, XI & XII.
VII: facial
XI: accessory
XII: hypoglossal
What connects the cerebellum to the brainstem?
The superior, middle and inferior peduncles.
