L3 Introduction to the Nervous System Flashcards
What are nuclei in the central nervous system?
Nuclei in the CNS are functional clusters of nerve cell bodies. They give rise to functionally distinct regions in the CNS.
What is a tract, when referring to the nervous system?
Tracts are groups of axons that allow for communication between specific nuclei.
Fill in the gaps: \_\_1\_\_ cells (\_\_2\_\_) are excitable cells that communicate via electrical and \_\_3\_\_ signals. \_\_4\_\_ cells account for 90% of the cells in the nervous system and \_\_5\_\_ neurons.
1) Nerve
2) neurons
3) chemical
4) Glial
5) support
If a cell has a single process from the cell body, what is its structural classification?
Unipolar.
Very rare in humans - found in olfactory system and retina
Describe the structure of a cell that is classified as multipolar.
The cell has multiple (more than 2) processing coming from the soma (cell body).
One is the axon, the others are dendrites.
If a cell has 2 projections from the cell body, what is its structural classification?
Bipolar.
One of the projections is the axon and the other is a dendrite.
Describe the structure of a cell is classified as pseudo-unipolar.
A pseudo-unipolar cell has a single process from the cell body, but this projection splits into a distinct dendrite and axon.
Common structure for sensory neurons
What is an afferent neuron?
The neuron that takes the signal from a receptor to the CNS.
Most afferent neurons are pseudo-unipolar and have cell bodies that are in clusters called ganglia. These ganglia lie outside the CNS.
What is an efferent neuron?
The neuron that relays a signal from the CNS to the effector organ(s)
Fill in the gaps:
__1__ make up 99% of all neurons in the body. Located entirely in the __2__, they go between the __3__ and __4__ neurons and carry out functions within the brain.
1) Interneurons
2) CNS
3) afferent
4) efferent
What are the 5 types of glial cell, plus their function.
1) Astrocytes - support, nutrients, develop/maintain BBB
2) Microglia - small, mobile, macrophages for CNS
3) Ependymal cells - line cavities and fluid-filled spaces
4) Oligodendrocytes - form myelin sheath in CNS
5) Schwaan cells - form myelin sheath in PNS (only 1 schwaan per axon, though)
True or false:
Oligodendrocytes form myelin sheaths in the PNS
False. Oligodenrocytes form myelin sheaths around axons in the CNS.
Schwaan cells form myelin around axons in the PNS.
Fill in the gaps:
__1__ form myelin around axons in the CNS. Each __2__ forms myelin around the axon of just one neuron.
1) Oligodendrocytes
2) Schwaan Cell
Schwaan cells are loyal.
Fill in the gaps:
The nervous system is made up of two major constituents: the __1__ and the __2__.
1) central nervous system
2) peripheral nervous system
The central nervous system comprises of the __1__ and the __2__.
1) brain
2) spinal cord
The peripheral nervous system is subdivided into the __1__ (which gives rise to __2__ and __3__ function) and the __4__ (which is made up of the __5__ and __6__ nervous systems).
1) somatic
2) sensory
3) motor
4) autonomic
5) parasympathetic
6) sympathetic
The somatic nervous system (SoNS) has dual functionality. What are the two functions of the SoNS?
Sensory and motor.
Sensory (afferent nerves): communicates information about the environment (internal or external to the body)
Motor (efferent nerves): voluntary movement
What are four things protect the brain?
1) Skull
2) Cranial meninges
3) Cerebrospinal fluid
4) Blood brain barrier
What 3 things protect the spine?
1) Vertebral column
2) Spinal meninges
3) Cerebrospinal fluid
What are the three layers of the meninges (from most deep to most superficial)?
1) Pia mater (deepest)
2) Arachnoid mater
3) Dura mater (most superficial)
In addition to the meninges, what other layers or spaces protect the brain and spine?
Epidural space: between dura mater and vertebral canal (contains fat). Only present in the spine, as the dura mater around the brain is attached to the skull
Subdural space: between dura mater and arachnoid (contains interstitial fluid)
Subarachnoid space: between arachnoid and pia mater (contains CSF)
Roughly how much CSF do humans have?
100-150ml
True or false: CSF is normally clear. Cloudiness or discolouration indicates underlying pathology
True
Where is cerebrospinal fluid (CSF) produced?
Choroid plexus
Fill in the gaps:
Cerebrospinal fluid contains __1__ amounts of protein, glucose and potassium. It also contains relatively __2__ amounts of sodium chloride.
1) small
2) large
True or false: CSF maintains it’s own pressure in healthy individuals
True
How is CSF sampled?
Lumbar puncture (spinal tap)
Fill in the gaps:
The brain contains __1__ cavities called __2__, which are continuous with the __3__ - a long, thin cylindrical cavity that runs the length of the spinal cord.
1) four
2) ventricles
3) central canal
What are the four ventricles?
There are two lateral ventricles, which are the largest, and further down are the ‘Third Ventricle’ and ‘Fourth Ventricle’
True or false: In patients with neurodegenerative diseases, such as Alzheimer’s, the ventricles appear larger
True. As the brain degenerates, the ventricles increase in size.
Where are the choroid plexuses located?
The choroid plexuses arelocated in the ventricles, which fills the ventricles and subarachnoid space with CSF, following a cycle of constant production and reabsorption.
True or false: Although the CNS only accounts for around 2% of body weight, it requires 17% of cardiac output and 20% of the oxygen utilised by the body
True
By which route does blood flow to the brain?
Blood flows via internal carotid and vertebral arteries into the dural sinuses and empties into the internal jugular veins.
By which route does blood flow to the spinal cord?
Blood flows via posterior intercostal and lumbar arteries and empties into posterior intercostal and lumbar veins.
In the majority of the body, small solutes can diffuse across intercellular clefts in the blood vessel walls. This would be disastrous to the CNS, so what prevents this happening?
Glial cells called astrocytes stimulate endothelial cells to develop tight juctions, which severely liits permeability to and from the CNS. This barrier is known as the blood brain barrier.
Can any molecules passively permeate the blood brain barrier?
Yes. Water, lipid-soluble molecules, and some gasses can passively cross the BBB.
Which can be organised into nuclei, grey matter or white matter?
Grey matter
Grey matter contains neuronal cell bodies, which can form clusters called nuclei.
Which can be organised into tracts, grey matter or white matter?
White matter
White matter consists of neuronal axons (mostly myelinated) which can be bound together into tracts.
Where would synaptic transmission and neural integration take place, in the grey matter or white matter?
Grey matter
Grey matter contains neuronal cell bodies, dendrites, axon terminals, unmyelinated axons and glial cells.
What bony structure protects the spinal cord?
Vertebral column
How many pairs of spinal nerves branch off the spinal cord at regular intervals?
31 pairs
The spinal cord is divided into 4 sections. What are these sections called?
1) Cervical
2) Thoracic
3) Lumbar
4) Sacral
True or false: The spinal cord acts as a conduit for both motor and sensory information
True
True or false: The spinal cord acts as a centre for coordinating reflex actions
True
True or false: Like the brain, the spinal cord contains grey matter and white matter
True
In cross-sectional view, the spinal cord is disk-shaped with a butterfly-shape in the middle. What is the butterfly-shape made from?
Grey matter
in the saggital plane, the spinal cord is symmetrical. What are the names of the two “horns” found on either side?
Dorsal horn (posterior)
Ventral horn (anterior)
Fill in the gap:
Afferent fibres originate in the periphery as sensory receptors and terminate in the __?__ horn.
dorsal
Fill in the gap:
Efferent neurons originate in the __?__ horn and travel to the periphery, where they form synapses with effector organs e.g. skeletal muscles
ventral
True or false: Grey matter consists of tracts that provide communication either between the levels of the spinal cord or between the brain and various levels of the spinal cord.
False. It is white matter (not grey matter) that does this
True or false:
White matter tracts link the peripheral nerves to the brain
True
Which region of the brain contains the cerebrum and diencephalon?
Forebrain
The brain has 3 main sections to it. What are they?
- Forebrain (cerebrum + diencephalon)
- Cerebellum
- Brainstem (midbrain, pons, medulla oblongata)
Where is the reticular formation housed?
Brainstem
Describe the structure of the brainstem
The medulla oblongata sits directly above the spinal cord and contains several centres that control vital autonomic (involuntary) functions including digestion, breathing and heart rate.
The pons (including overlying cerebellum) sits above the medulla, acts as a relay station conveying information from the cerebral hemispheres to the cerebellum.
The midbrain, sits on top of the pons controls many of the sensory and motor functions including eye movement and the coordination of audio visual reflexes.
Fill in the gaps:
The reticular formation is involved in many involuntary functions and is a network of __1__ and the __2__.
- interconnected nuclei
2. reticular activating system
What are the functions of the reticular formation?
The output of the reticular formation directly affects the activity of the cerebral cortex so functions include:
- Awareness
- Attention
- Wakefulness (and therefore sleep)
- Consciousness
Which structure lies beneath the occipital lobe and behind the brainstem?
Cerebellum
True or false, the cerebellum contains more neurons that the cerebral hemispheres combined?
True!
What is the primary function of the cerebellum?
Control and coordination of movement control centre (i.e. comparing the intended movement to actual movement, responsible for motor memory).
While the highest level of motor control comes from the cerebral cortex, the basal ganglia and cerebellum provide feedback that supports this.
Which structure lies rostral to the midbrain?
Diencephalon
Rostral = towards the front
Fill in the gaps:
The diencephalon contains 2 structures:
- The __1__ processes most of the sensory information reaching the cerebral cortex from the rest of the CNS.
- The __2__ is involved in regulating autonomic (temperature, circulation, food intake), endocrine and visceral functions.
1) thalamus
2) hypothalamus
The cerebrum consists of two components. What are they?
- Deep (subcortical) nuclei
2. The cerebral cortex
What is the corpus callosum?
A neural bridge that connects the two hemispheres of the brain, allowing them to communicate.
What are the deep nuclei in the cerebrum?
Basal ganglia
Thalamus
Hypothalamus
Limbic system nuclei
What is the largest part of the brain?
The cerebral cortex
Fill in the gaps:
The __1__ is a highly convoluted layer of __2__ matter consisting of __3__ and __4__.
1) cerebral cortex
2) grey
3) sulci
4) gyri
The cerebral cortex can be divided into 4 lobes, named after the bones that cover them. What are the names of the lobes?
1) Frontal
2) Temporal
3) Parietal
4) Occipital
Which cerebral lobe is responsible for personality?
Frontal
Which cerebral lobe is responsible for voluntary motor activity?
Frontal
Which cerebral lobe is responsible for sense of smell, hearing, and taste?
Temporal
Which cerebral lobe is responsible for peripheral sensations?
Parietal
Which cerebral lobe is responsible for vision?
Occipital
What is the frontal lobe responsible for?
Personality, voluntary motor activity
What are the temporal lobes responsible for?
Senses of smell, hearing, and taste
What is the parietal lobe responsible for?
Peripheral sensations
