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Neuroscience > Nervous System Anatomy > Flashcards

Nervous System Anatomy Flashcards

1
Q

How is the nervous system organised?

A 
CNS and PNS. Afferent pathways = periphery to CNS. Receptors are either somatic or visceral. Efferent = CNS to periphery. Somatic NS or Autonomic NS. Autonomic split into Sympathetic (Fight or Flight) 
and Parasympathetic (Rest & Digest).
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2
Q

Which nerves make up the PNS and describe some features of the PNS

A

12 pairs of cranial nerves : I - XII.
31 pairs of spinal nerves : 8 Cervical, 12 Thoracic, 5 Lumbar, 5 Sacral, 1 Coccygeal.
Ganglia - Groups of soma
Plexuses - Networks of intersecting nerves or fibres

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3
Q

Describe the structure of a nerve

A

A collection of nerve fibres (axons) organised into fasicles. Nerves also contain blood vessels. Some cranial nerves are purely motor (occulomotor), some purely sensory (optic) and some mixed (trigeminal). All spinal nerves are mixed, and have an autonomic component

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4
Q

Describe the structure and organisation of cranial nerves

A

They are numbered in the order they emerge from the CNS, cranial to caudal. I and II emerge from cerebrum, rest along brainstem until just above spinal cord. Carry info to and from head and neck. Vagus (X) reaches heart, lungs, stomach. III, VII, IX, X have parasympathetic outflow.

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5
Q

Describe some functions of cranial nerves

A 
Olfactory (I) - Smell
Optic (II) - Vision
Occulomotor (III) - Eye movement
Trochlear (IV) - Eye movements
Trigeminal (V) - Face sensation, Chewing
Abducens (VI) - Horizontal eye movements
Facial (VII) - Expression muscles, Taste
Vestibulo-cochlear (VIII) - Hearing and Balance
Glossopharyngeal (IX) - Tongue and Pharynx
Vagus (X) - Swallowing, Heart, Lungs, Abdominal Viscera
Spinal Accessory (XI) - Neck muscles
Hypoglossal (XII) - Tongue muscles
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6
Q

What is the ventral (anterior) root of the spinal cord?

A

Made of motor and autonomic fibres leaving the spinal cord, ending on muscle via a NMJ. Motoneuron soma in the ventral horn, autonomic soma in the lateral horn (little one)

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7
Q

What is the dorsal root of the spinal cord?

A

Sensory fibres, coming from peripheral receptors into the CNS. It has a swelling, the dorsal root ganglion, where the soma of sensory neurons are located.

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8
Q

How do these two roots form a spinal nerve?

A

The two roots join to form a spinal nerve which leaves via the intervertebral foramen (holes). After this it branches into a ventral and dorsal ramus. Dorsal innervates skin of the back of the trunk, and ventral innervates front of the body and limbs. Each ramus branches into smaller peripheral nerves which are mixed.

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9
Q

What are dermatomes and myotomes?

A

Each spinal nerve innervates a specific area of skin (dermatome) and a group of muscles (myotome). It innervates them via peripheral nerves, but before the branching into peripheral nerves, spinal nerves enter plexuses. This means that there is overlap - one spinal nerve innervates many dermatomes/myotomes

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10
Q

How do dermatomes and myotomes impact the effects of nerve damage?

A

Damage to a peripheral nerve results in a more specific loss of feeling/movement ie. area more defined. Damage to a root will lead to a more general parasthesia/muscle weakness as one root only serves small patches of skin/muscles.

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11
Q

How can knowledge of dermatomes and myotomes assist in a clinical setting?

A

Knowledge of nerve distribution allows the use of pin prick tests and muscle contractility tests to determine the location of a spinal cord injury

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12
Q

What is the organisation of the CNS?

A

Brain and spinal cord. Structures in layers, new layers are overlayed as time goes on. Complex functions develop with evolution

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13
Q

Describe the gross structure of the spinal cord

A

Highly segmented, consisting of repeating units that are roughly cylindrical. The cord is encased in the vertebral column. The column has a central canal which is connected to the cerebral ventricles and filled with CSF.

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14
Q

What is the cauda equina and how does it exist?

A

A bundle of nerve roots below the L1/L2 vertebra that is not in the vertebral canal. It happens because the neural tissue of the spinal cord is shorter than the vertebral canal

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15
Q

Why is the cauda equina important clinically?

A

It allows lumbar punctures to be performed and CSF to be collected from L3/L4 or L4/L5 vertebrae without damaging neural tissue

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16
Q

What is white matter? How is it organised?

A

Made from myelinated axons connecting different parts of NS. Organised in columns (funiculi) - posterior, lateral, anterior. Descending fibres carry motor signals from brain to motor neurons in grey matter. Ascending fibres carry sensory info to brain.

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17
Q

What is grey matter? How is it organised?

A

Soma, dendrites, unmyelinated axons, glia.
Dorsal horn neurons receive terminals from sensory neurons via dorsal root of corresponding spinal nerve and project onto higher parts of CNS.
Ventral horn consists of motoneurons receiving impulses from PMC, sending their axons out via ventral root of spinal nerve to skeletal muscles. Interneurons connect neurons in spinal cord - can be inhib or stim

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18
Q

What is a reflex?

A

A reflex is an involuntary action that bypasses the brain. The simplest reflex arc is receptor, afferent, integration centre (synapse/interneuron), afferent, effector. It doesn’t completely exclude the brain, as sensory fibre forms many synapses, and one goes to the brain (awareness of feeling)

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19
Q

Describe and explain the Patellar Reflex

A

When the patellar tendon is stretched, it’s detected by stretch receptors (muscle spindles) which stimulate sensory neurons that travel to spinal cord, synapsing with motor neurons that contract quadriceps. Inhibitory interneurons are stimulated by sensorys causing hamstrings to not oppose quadriceps contraction.

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20
Q

How can the different structures in the brain be grouped?

A

Developmental approach: Hindbrain (cerebellum, medulla oblongata, pons) midbrain (mesencephalon), and forebrain (diencephalon, cerebral hemispheres).
Functional approach: Brainstem (medulla, pons, midbrain), cerebrum (diencephalon and cerebral hemispheres), and cerebellum.

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21
Q

What is the brain stem?

A

A continuation of the spinal cord which passes through the foramen magnum at the base of the skull. Consists of medulla, pons, and midbrain (going up).

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22
Q

What is the function of the brainstem?

A

Contains nuclei (groups of soma) where cranial nerves III onwards originate. Medulla controls defensive reflexes like vomiting, sneezing, coughing. Also contains nuclei important for respiration, blood pressure, heart rate. Pons has nuclei for tear and saliva production. Midbrain has the substantia nigra which is considered one of the basal ganglia. Also has VTA. Superior and inferior colliculi which are bumps at the back of the midbrain. Superior = eye movements and visual processing, inferior = auditory processing.

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23
Q

What is the reticular formation?

A

A network of neurons and tracts (bundles of fibres which connect nuclei in the CNS). It runs through the brainstem and is connected to most other parts of the CNS. It controls sleep, arousal, wakefulness.

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24
Q

What is the cerebrum?

A

The part of the brain consisting of the Diencephalon (Thalamus and Hypothalamus) and the Cerebral hemispheres (Basal ganglia and Cerebral Cortex).

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25
Q

What is the thalamus?

A

A collection of nuclei (groups of soma) which is roughly egg shaped - a key relay centre. There is one on each side of the centre of the brain, above the brainstem. All sensory systems are connected to a thalamic neuron (apart from olfactory). Has a key role in regulation, of sleep, attention, consciousness.

26
Q

What is the hypothalamus?

A

Funnel shaped area below the thalamus (HYPO). Pituitary is attached ventrally at infundibulum. Has endocrine role but also nuclei important in regulation of temperature, eating, drinking, sleep/wake cycle

27
Q

What are the basal ganglia?

A

Interconnected groups of neurons buried deep within the brain and involved in movement control. Theyre grouped on function rather than location. Should be Basal nuclei as nuclei refers to soma in CNS.

28
Q

List the basal ganglia and their location

A

Corpus Striatum - Caudate nucleus and putamen
Globus Pallidus - With putamen forms Lentiform nucleus
Subthalamic Nucleus - Hypothalamus
Substantia Nigra - Midbrain

29
Q

Describe the location and structure of the striatum

A

Connections between the caudate and putamen appear as radial lines (striations)

30
Q

Describe the location and structure of the caudate

A

Tadpole shaped, with a tail and a head. In the body is the globus pallidus. Next to the globus pallidus is the lentiform nucleus, which is on the thalamus. Outside the lentiform nucleus is the putamen.

31
Q

Describe and explain the main function of the basal ganglia

A

Info from cortex comes into caudate/putamen - the main input nuclei. Globus pallidus and substantia nigra are the main output nuclei, projecting onto cortex mostly by way of the thalamus, as well as to nuclei in brain stem. BG influences activity in other areas to affect movement. Don’t really know how. Main output could be inhibition from globus pallidus to thalamus, inhibiting unwanted movements. Initiation signal sent from cortex to BG, following the direct pathway, silencing GP neurons. So thalamus allows movement to occur. Indirect pathway = subthalamic neurons increasing suppression of unwanted movements. Balancing these pathways leads to smooth movements. BG also connects with limbic system, linking motion with emotion.

32
Q

How do disorders affecting BG affect movement?

A

Results in exaggerated (rigidity, tremors, jerks) movements or suppressed (slow, hesitant) movements. Parkinson’s = substantia nigra degeneration.

33
Q

What is the cerebral cortex?

A

The highest centre in the CNS, responsible for higher mental functions such as movement initiation, perception, processing of sensation, emotions, memory, thinking, language. A 2-4 highly folded layer on the outer surface of the brain.

34
Q

Describe the structure of the cerebral cortex

A 
Hemispheres are separated by the longitudanal fissure. Central sulcus (Rolandic fissure) splits frontal lobe from parietal lobe. 
Lateral sulcus (Sylvian fissure) splits temporal lobe. 
Parieto-occipital sulcus splits occipital lobe but the boundary is not clearly defined.
35
Q

Describe the function of each of the surface lobes of the brain

A

Frontal lobe - Movement and higher order thought such as decision making, planning, rationality
Occipital lobe - Primary Visual Cortex
Temporal lobe - Auditory signals, memory, learning
Parietal lobe - Processing sensory info, attention, representation of space around us

36
Q

What side of the body does each hemisphere control and why?

A

Hemispheres usually control the opposite side of the body (contralateral) because fibres usually cross over.

37
Q

Describe the structure and function of the frontal lobe

A

Contains PMC - origin of movement signals. Adjacent to this is the pre-motor cortex and supplementary motor area to plan and organise complex movement. Also contains prefrontal cortex which is an association area (receives inputs from multiple areas) concerned with social behaviour, judgement, concentration, problem solving, personality

38
Q

Describe the structure and function of the parietal lobe

A

Occupied by the PSC - receives and interprets sensory info. Sensory association area allows recognition of our body parts and identifying unseen objects by touch

39
Q

Describe the structure and function of the occipital lobe

A

Primary visual cortex - processes visual info. Lesions in this area = loss of vision. Visual association areas important for colour and shape recognition, location and direction of moving objects

40
Q

Describe the structure and function of the temporal lobe

A

Primary auditory area as well as areas helping to recognise distance and direction of sound. Also has higher association areas involved in long term memory..

41
Q

How are the PMC and PSC represented in the cortex?

A

Somatotopically. This means that the body has a precise and ordered correspondence with a defined area of the cortex. Areas with a high conc. of receptors map to a larger area of the cortex.

42
Q

Where are most right handed people’s speech and language areas?

A

In the left hemisphere. Area of Broca in the frontal lobe for speech production and Area of Wernicke in the temporal lobe for spoken and written language recognition.

43
Q

Describe the structure and function of the limbic system

A

Cortical and subcortical structures from all lobes form the limbic system. They are located around the medial and inferior cerebral cortex rim. Include Hippocampus, Amygdala, Cingulate gyrus, Entorhinal cortex. The limbic system deals with emotions, memory, learning. Closely associated with olfactory system.

44
Q

Describe the function of the amygdala

A

Main structure for the processing of fear. Connected to the hypothalamus in order to elicit a physical fear response

45
Q

Describe the function of the hippoocampus

A

Essential for memory acquisition and consolidation. Close connection with the limbic system means that memories with a strong emotional content are reinforced.

46
Q

Descirbe the structure of the cortex

A

The cortex is organised in layers of cells and fibres - 6 in recent parts (neocortex), 3-5 in older parts (paleo- and archicortex) such as olfactory bulb, hippocampus respectively. The main neuronal types are pyramidal cells which mainly project out of the cortex, and granule cells which are the main interneurons, connecting cells in the cortex.

47
Q

What is the composition of each layer of the cortex?

A

Some layers contain mostly cell bodies, others like layer 1 have only glia and connecting axons.

48
Q

Describe the structure of cerebellum

A

Two hemispheres connected by the vermis in the midline. The cerebellum is attached to the brainstem posteriorly by 3 pairs of peduncles (stalks). It has a surface cortex of grey matter which is organised in folia (thin parallel folds and a deeper white matter layer which contains 4 sets of nuclei.

49
Q

Describe the neuronal cell types found in the cerebellum

A

Cerebellar cortex has many small granule cells and characteristic Purkinje cells with large soma and dendritic trees connected by parallel and climbing fibres by a specific architecture

50
Q

What is the function of the cerebellum?

A

Movement coordination and posture control - allowing smooth and precise movement. Also detects and corrects error during the course of a movement. Also motor learning to reduce errors in the future. It is connected to the vestibular system (balance control), spinal cord and muscles of locomotion and posture, cerebral motor cortex and thalamus for learned movements (manual skills, trajectory, timing, speed, force)

51
Q

Describe the different parts of the cerebellum and their functions

A

Cerebrocerebellum (on each side) receive cortical input involved with planning and initiating movement. Spinocerebellum (outside vermis in the middle) receives info about limb position and touch and pressure sensations from spinal cord. Compares limb location with intended position and sends signals to modify the movement.
Vermis is involved with posture, limb and eye movements
Vestibulocerebellum maintains equilibrium, balance, and posture.

52
Q

How does the cerebellum communicate with the rest of the NS?

A

Via the peduncles. When info is sent to cerebellum, the indirect path is taken to reach the very branched Purkinje cells. They project to the deep cerebellar nuclei which send info to various areas in thalamus and brainstem that sends info to cortical motor areas or descending motor tracts to modify movements

53
Q

What is the functional of cerebral white matter?

A

Responsible for communication between cerebral areas and also cortex and lower CNS areas. White matter is mainly myelinated axons bundled into large tracts.

54
Q

What are commissural fibres?

A

Allows each hemipshere of the brain to coordinate and function as a whole by connecting correspodning grey areas of each hemisphere. The largest of these is the corpus callosum which connects both hemispheres.

55
Q

What are association fibres?

A

Connect different parts of the same hemisphere. Short fibres connect adjacent gyri. Longer fibres are bundled into different tracts and connect different cortical lobes.

56
Q

What are projection fibres?

A

They connect the cortex to lower brain (sensory input, motor output). Run vertically not horizontally. They form the internal capsule, a compact band passing between the thalamus and some basal nuclei. Above this, fibres radiate out through the white matter to the cortex, forming an arrangement called the corona radiata.

57
Q

What is a callosum resection and what does it cause?

A

Divison of the callosum, a treatment for epilepsy. Causes inability to name objects seen with the left eye because the language centre is on the left and the fibres are crossed.

58
Q

Describe the structure and function of the ventricular system

A

Throughout the CNS, interconnected cavities (ventricles) are filled with CSF. They are the lateral ventricles, which are C shaped within the hemispheres and have anterior, posterior, inferior horns. Connecting each side is the 3rd ventricle, located between the thalami. Below this is the cerebral acqueduct, connecting to the 4th ventricle which is between the brainstem and cerebellum. It continues caudally with the spinal cord’s central canal. Ependymal cells line the surface of the ventricles. Vascular structures called choroid plexus are in the ventricular system and produce CSF by selective filtration of the plasma.

59
Q

What is the function of CSF?

A

It circulates around the brain in the subarachnoid space where it is reabsorbed into the venous sinus. It provides the brain with extra protection, but also helps maintain homeostasis, and transports substances and immune cells. Diagnoses can be made by taking into account CSF composition

60
Q

Describe the structure and function of the meninges

A

Protecting the brain. The outermost layer - dura mater - is hard and fibrous. In some areas it splits in two (periosteal and meningeal) which contain the venous sinuses. The arachnoid mater is made of trabeculae (thin filaments) like a spider web, keeping blood vessels in place in the subarachnoid space which is filled with CSF. Pia mater is thin and covers the neural tissue, penetrating the sulci.

Neuroscience (9 decks)

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