Nervous System 2 Flashcards
The Central Nervous System (CNS) is formed of 2 main components. What are they?
The brain and spinal cord
Why is the cranium important?
It provides physical protection for the brain
The spinal cord is an extension of the brain. True or false?
True
What is the name of the bony framework that protects the spine?
Vertebral column
What are meninges?
Layers of tissue / membranes that cover the brain and spinal cord.
List 4 things that the brain is protected by.
- The cranium
- The meninges
- Cerebro-spinal fluid (CSF)
- The blood-brain barrier (BBB)
What type of tissue are the meninges made up of?
Connective tissue
List the 3 layers of tissue that form the meninges.
- Dura Mater (tough outer layer)
- Arachnoid Mater
- Pia Mater
Describe the dura mater (“tough mother’).
- The tough outer layer of the meninges. - - - There for protection and support.
- Divides into 2 layers in the brain
- Attaches to the periosteum (top) and sacrum (bottom).
At which vertebral level do the meninges stop / attach?
S2 level
Which layer of the meninges divides into 2 layers in the brain to create venous sinuses (aka the bridging veins)?
The Dura Mater
What is the role of the venous sinuses in the dura mater of the meninges?
They allow blood to drain out of the brain into the jugular veins.
What is the arachnoid mater made up of?
Collagen and elastin fibres
Which is the most delicate membrane of the meninges, and wraps around the contours of the brain like cling film?
The Pia Mater
Which thin, transparent layer of the meninges contains blood vessels that supply the spinal cord?
The Pia Mater
What is the subdural space between the arachnoid mater and dura mater (meninges) filled with?
Interstitial fluid
What is the sub-arachnoid space between the arachnoid mater and pia mater (meninges) filled with?
Cerebrospinal fluid
What is the sub-arachnoid space?
The space between the arachnoid mater and pia mater layers of the meninges, which is filled with cerebrospinal fluid.
What is a subdural haematoma?
A slow-developing venous bleed in the subdural space of the meninges around the brain.
What is a subarachnoid haemorrhage?
An arterial bleed (rapidly developing) in the sub-arachnoid space of the meninges around the brain.
If a patient feels trauma in the back of the head (like suddenly being punched or hit with a baseball bat, or a ‘thunderclap headache’) what pathology might they be experiencing / have experienced?
A sub-arachnoid haemmorhage
A subdural haematoma is more likely to happen in a patient that has dementia, specifically Alzheimers disease. Why is this?
Because Alzheimers Disease causes gradual brain shrinkage, creating more and more tension through the dura mater.
What is usually the cause of a subarachnoid haemorrhage?
The rupturing of a brain aneurysm (usually a berry aneurism).
What is cerebrospinal fluid?
- A clear liquid that protects the brain and spinal cord from mechanical and immunological trauma.
- It also nourishes the brain and spinal cord by delivering lots of nutrients to them.
What colour and consistency is cerebrospinal fluid?
CSF is colourless and quite gloopy
What is CSF made of?
Cerebrospinal fluid is made from filtered blood, and is mostly water with ions and glucose.
List 3 places where you would find cerebrospinal fluid.
- In the subarachnoid space between the arachnoid mater and pia mater (in the meninges).
- In the ventricles (cavities) in the brain.
- In the central canal of the spinal cord.
Which type of cells produce cerebrospinal fluid?
Ependymal cells (ciliated glial cells)
How much CSF do ependymal cells produce per day?
Around 500mls (more than the brain and spinal cord can actually contain, so large amounts are gradually reabsorbed back into the blood)
List 4 functions of cerebrospinal fluid.
- Support & protection of the brain and spinal cord, acting as a shock absorber.
- Maintains uniform pressure around the brain.
- Circulates nutrients and waste
- Keeps brain and spinal cord moist.
What is hydrocephalus?
Too much CSF accumulated around the brain.
Often due to compromised ability to reabsorb excess CSF
List 3 nutrients found in CSF.
Water, glucose, ions (i.e, sodium and potassium)
What is the choroid plexi?
A cluster of ependymal cells and capillaries that produce CSF.
Blood flows to the brain from the ______ and _______ arteries.
Vertebral and Carotid arteries
Where would you find the carotid arteries and how many are there?
2, in the front of the neck
Where would you find the vertebral arteries and how many are there?
2, in the back of the neck
What percentage of the body’s oxygen and glucose does the brain use at rest?
20%
What is the blood brain barrier (BBB)?
A physical barrier against the movement of substances from the blood into the brain.
Which cells maintain / provide the blood brain barrier?
Astrocytes (star-shaped)
What is the role of the blood brain barrier?
The BBB protects the brain from toxins, harmful substances and bacteria
List 4 substances that can travel across the blood brain barrier.
- Lipid soluble substances
- Glucose
- Gases (i.e, O2 and CO2)
- Ions
List 3 things that can’t (normally) cross the blood brain barrier.
- Proteins
- Blood cells
- Some drugs
List 2 lipid soluble substances that can cross the blood brain barrier.
Alcohol, anaesthetics
List the 4 major parts of the brain
- Brainstem
- Diencephalon (‘interbrain’)
- Cerebrum
- Cerebellum (‘little brain’)
What is the brainstem sub-divided into?
3 parts:
- Medulla Oblongata
- Pons
- Midbrain
What is the diencephalon sub-divided into?
3 parts:
- Thalamus
- Hypothalamus
- Epithalamus
What is the thalamus?
The core of the brain
Where would you find the thalamus?
Right in the middle of the brain
Which area of the brain governs sensory perception and motor control/output?
The cerebrum
Why is the cerebellum important?
We need it for clear speech, balance, posture and regulating movements.
Which part of the brain is the continuation of the spinal cord?
The brainstem
What is the foramen magnum?
The large hole in the bottom of the skull where the spinal cord runs up and becomes the brain stem.
What is the first part of the brainstem (closest to the spinal cord) called?
The medulla oblongata
Which 2 key centres of the body are housed by the medulla oblongata?
Respiratory centre and cardiac centre
Which part of the brainstem regulates the heartbeat and breathing?
Medulla Oblongata
Why could damage to the medulla oblongata be fatal?
Because the medulla oblongata regulates heartbeat and breathing.
Which 3 reflexes are controlled by the medulla oblongata?
- Vomitting
- Hiccuping
- Sneezing
How many cranial nerves are there?
12
How many of the 12 cranial nerves come off of the medulla oblongata?
4
What is cranial nerve 10 also known as?
The vagus nerve
List 4 functions of the medulla oblongata (in the brainstem)
- Contains the respiratory and cardiac centres
- Controls vomiting reflex
- Controls sneezing and hiccuping reflex
- Contains 4 cranial nerves
- Contains motor tracts down the spinal cord, from the brain (the corticospinal tract)
What is the name of the motor tract that descends down the spinal cord from the brain?
The corticospinal tract
What does the pons share with the medulla in the brainstem?
The respiratory centre. So both the pons and the medulla help to control breathing.
Why is the pons known as ‘the bridge’ within the brainstem?
Because it bridges the gap between the main brain and the medulla oblongata (and looks bridge-shaped)
How many cranial nerves are found within the pons?
4
List 3 functions of the pons (in the brainstem).
- Helps to control breathing
- Houses 4 cranial nerves
- Relays motor tracts
Where is the midbrain found?
At the very top of the brainstem, above the medulla oblongata and pons.
Which part of the brain contains the substantia nigra?
The midbrain, in the brainstem.
What is the substantia nigra and where is it found?
A large, darkly pigmented area within the midbrain, which contains dopamine releasing neurons.
Name the large, darkly pigmented area within the midbrain, which contains dopamine releasing neurons and is associated with Parkinsons Disease.
The substantia nigra
List 4 functions of the midbrain
- Contains dopamine releasing neurons (in the substantia nigra)
- Control of subconscious movements
- Eye reflexes and tracking
- Houses 2 cranial nerves (for eye movement)
- Relaying of motor tracts
- Movement of the head and neck
Name the 3 parts that make up the diencephalon area of the brain.
- Thalamus
- Hypothalamus
- Epithalamus
Which area of the diencephalon is known as ‘the core of the brain’?
The thalamus.
It makes up 80% of the diencephalon.
Why is the thalamus known as the ‘major relay centre’?
Because it receives information coming up through the spinal cord and brainstem, and relays it to the appropriate parts of the brain.
Which part of the brain integrates sensory and motor information?
The thalamus
Which part of the brain plays a big part in our body’s maintenance of circadian rhythm?
The epithalamus
Why does the epithalamus play a large role in the maintenance of circadian rhythm and the sleep cycle?
Because it houses the pineal gland, which secretes melatonin.
Which hormone is secreted from the epithalamus area of the brain?
Melatonin
Which gland produces melatonin?
Pineal gland
Which part of the brain, which is also a key gland, is involved in hormone regulation and homeostasis?
The hypothalamus
The hypothalamus works closely with which gland?
The pituitary gland
Which area of the brain controls the autonomic nervous system (ANS)?
The hypothalamus (which sits within the diencephalon)
List 4 functions of the hypothalamus.
- Hormone regulation
- Receiving sensory information
- Control of the Autonomic Nervous System (ANS)
- Controls body temperature
- Regulates circadian rhythm
- Regulates emotional & behavioural patterns
- Regulates appetite / satiety
Which part of the brain makes up just 10% of the overall brain mass, yet contains over half of the neurons in the entire brain?
The cerebellum
Which small area of the brain contains around 50 billion neurons?
The cerebellum
List 3 functions of the cerebellum.
- Posture and balance
- Coordination
- Correction of errors during ongoing movement (ie, learning to walk)
- Proprioception
Which area of the brain plays a key part in learning to walk, balance and play an instrument?
The cerebellum
Which part of the brain is heavily influenced by alcohol, leading to slurred speech, staggering and loss of balance?
The cerebellum
List 3 potential causes of cerebellar damage / injury.
- Chronic alcohol abuse
- Coeliac Disease
- Thiamine (Vit B1) deficiency
What is ataxia?
Loss of balance / imbalance / lack of muscle coordination.
Cerebellar disease produces symptoms of ataxia. List 3 of these symptoms.
- Stumbling and unsteadiness
- Slurred speech
- Intention tremor (i.e, hand tremor when putting key in door)
In which CNS pathology might you see an intention tremor?
Cerebellar Disease
The cerebrum is divided into ____ ______ (left and right)
Two hemispheres / parts
Which part of the cerebrum contains grey matter (i.e, is filled with cell bodies)?
The outer cerebral cortex
Which part of the brain is often referred to as the ‘seat of intelligence’?
The cerebrum
What is found in the inner, deeper region of the cerebrum?
White matter (made up of myelinated axons)
What is the corpus callosum?
The structure that connects the left and right hemispheres of the cerebrum.
What does the corpus callosum do?
- Connects the left and right hemispheres of the cerebrum.
- Allows coordination of movements between the 2 sides of the body (i.e, walking)
List the 2 main functions of the cerebrum.
- Sensory perception
2. Motor control of skeletal muscles (movement)
The right hemisphere of the cerebrum controls the ____ side of the body, whilst the left hemisphere of the cerebrum controls the ___ side of the body.
Right hemisphere controls the left side.
Left hemisphere controls the right side.
(Think ‘opposites attract’)
The ________ makes up the majority of the brain.
Cerebrum
Where do the motor neuron axons that join to form the corticospinal tract, cross over?
In the medulla oblongata (in the brain stem)
What does ‘decussation’ mean?
Crossing over.
i.e, the corticospinal tract decussates in the medulla oblongata.
If a stroke patient presented with weakness on the left side of their body, which cerebral hemisphere was likely affected?
The right cerebral hemisphere (opposite side to the body symptoms)
Each cerebral hemisphere can be further sub-divided into ____ lobes.
4 lobes
Name the 4 lobes that make up each cerebral hemisphere
- Frontal
- Temporal
- Parietal
- Occipital
What are the 4 lobes of the cerebral hemispheres named after?
The bones that cover them.
Frontal, Temporal, Parietal, Occipital
The frontal lobe of the cerebrum is involved in ______ _______
Motor skills
The temporal lobe of the cerebrum is involved in ______
Hearing
The parietal lobe of the cerebrum is involved in ______ , and contains the ______ _______.
Sensation
Contains the sensory cortex
The occipital lobe of the cerebrum is involved in ______
Vision
What is the limbic system?
The area of the brain that is active with different emotions.
List 3 key structures within the limbic system.
- Amygdala
- Hippocampus
- Hypothalamus
The brain receives around ____% of the cardiac output of blood (the same as the kidneys).
20%
Why does the brain need a constant supply of blood?
Because it has a very limited ability to store oxygen and glucose.
Why is cardiovascular health important for brain health?
Because the cardiovascular system supplies the brain with blood and nutrients
Name the 4 arteries that supply blood to the brain.
2 x vertebral arteries
2 x carotid arteries
What is the ‘Circle of Willis’?
A circle of arteries within the brain, where the carotid and vertebral arteries meet.
Where would you find the ‘Circle of Willis’?
Right in the middle of the brain.
If a berry aneurysm was to rupture, this would result in a ___ _______ haemorrhage.
Sub arachnoid haemmorhage
Name a part of the brain where it is common for berry aneurysms to develop.
In the Circle of Willis (where the vertebral and carotid arteries meet)
Say the mnemonic for remembering cranial nerves 1 - 12
On Occasion Our Trusty Truck Acts Funny. Very Good Vehicle Any How.
(OOOTTAFVGVAH)
Say the mnemonic for remembering the sensory or motor (or both) function of each of the 12 cranial nerves
Some Say Marry Money. But My Brother Says Big Brains Matter More.
(SSMMBMBSBBMM)
Which cranial nerve is involved in sense of smell?
Olfactory nerve (1)
Which cranial nerve is involved in vision / sight.
Optic nerve (2)
Which cranial nerve is involved in eye movements, eyelid opening and pupil size?
Oculomotor (3)
Cranial nerve 4, the trochlear nerve is involved in what?
Eye movements
There are 4 cranial nerves involved with the eyes. Only 1 of these is purely sensory, the others are motor. Which is the sensory nerve?
The optic nerve (2)
Which of the cranial nerves is associated with facial sensations and chewing?
Trigeminal nerve (5)
Which cranial nerve is responsible for eye movement (specifically abduction of the eye)?
Abducens (6)
Which cranial nerve supplies masseter and temporalis (the muscles of mastication)?
Trigeminal nerve (5)
Which cranial nerve is involved in facial expression?
Facial nerve (7)
Which cranial nerve is involved in salivary glands and taste?
Facial nerve (7)
Which cranial nerve is damaged in Bells Palsy, creating unilateral paralysis of the face?
Facial nerve (7)
Which pathology is associated with damage to cranial nerve 7, the facial nerve?
Bell’s Palsy
Which cranial nerve is involved in hearing and balance?
Vestibulocochlear nerve (8)
Which cranial nerve is involved in taste, swallowing and tongue sensations?
Glossopharyngeal nerve (9)
Which cranial nerve is the big nerve in the parasympathetic nervous system, helping to reduce blood pressure, reduce heart rate and increase the motility of the digestive tract?
Vagus nerve (10)
List 4 functions of the vagus nerve (cranial nerve 10).
- Reduce blood pressure
- Reduce heart rate
- Increase digestive motility
- Receives sensory information from the thorax and abdomen
Which of the cranial nerves is involved in neck and shoulder movement?
Accessory nerve (11)
What does cranial nerve 12, the hypoglossal nerve do?
Innervates muscles for tongue movement and speech
Why is the optic nerve densely myelinated?
So that vision / what we see keeps up with what we’re actually looking at.
Name a cranial nerve that is unmyelinated
Olfactory nerve (1)
Which 3 cranial nerves move the eyeball?
Oculomotor, Trochlear, Abducens
Name the bony framework that protects the spinal cord.
The spinal column
The _____ _____ begins at the foramen magnum and terminates at the level of L2
Spinal cord
What is the cauda equina (‘horses tail’)?
Spinal nerves that continue downwards past the level of L2 (where the spinal cord terminates - also known as the conus)
What is the conus?
The point at which the spinal cord terminates (L2 - lumbar spine)
The spinal cord consists of _____ matter around a core of _____ matter.
White matter around a core of grey matter.
The motor (descending) and sensory (ascending) tracts exist within the outer _____ matter of the spinal cord.
White matter
The posterior (dorsal) horn, and anterior (ventral) horn receive and integrate incoming and outgoing information. They are found within the inner ______ matter of the spinal cord.
Grey matter
What is the role of the posterior (dorsal) horn within the spinal cord?
It receives sensory impulses.
What is the role of the anterior (ventral) horn within the spinal cord?
It sends out motor impulses in response to sensory information.
Sensory impulses go into the back (posterior) of the spinal cord, whilst motor impulses are sent out the front (anterior) of the spinal cord. True or false?
True
What are the spinal tracts?
Bundles of myelinated axons running up and down the spinal cord.
There are 2 sensory tracts and 1 motor tract.
How many spinal cord tracts are there?
3
Name the 3 spinal cord tracts.
- Dorsal columns (ascending, sensory)
- Spinothalamic tract (ascending, sensory)
- Corticospinal tract (motor)
Name the 2 ascending, sensory spinal cord tracts.
Dorsal columns and spinothalamic tract
Which sensory spinal cord tract carries the signals for light touch, vibration and proprioception?
Dorsal columns
Which sensory spinal cord tract carries the signals for pain and temperature?
Spinothalamic tract
Which motor spinal cord tract carries the signals for voluntary movements?
Corticospinal tract
What is a reflex?
A fast, automatic, unplanned response to a stimulus.
e.g pulling hand away from a source of heat.
Most reflexes are a spinal reflex (don’t even go up to the brain). True or false?
True
Briefly describe the 5-stage sequence of a reflex arc.
Sensory receptor -> sensory neuron -> integrating centre (interneuron) -> motor neuron -> effector organ
What is each spinal nerve named after?
The level of the corresponding vertebrae (i.e, C1, C2 etc)
What are the vertebral foramina?
Small holes in the vertebrae through which the spinal nerves exit the vertebral column.
What is the name given to the small holes in the vertebrae through which the spinal nerves exit the vertebral column.
Vertebral foramina
