Nervous system physiology (2) The Brain Flashcards
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What is the function of CSF?
- This is the clear colourless liquid that acts to protect the brain and spinal cord from injury
- It transports oxygen and glucose from the blood to the neurons and neuroganglia.
- It provides mechanical protection to the brain and spinal cord by acting as a shock absorber, in a sense the brain ‘floats’ within the cranial cavity.
CSF provides the optimum chemical environment for neuronal signalling even very slight changes in the ionic environment can have drastic effects on nerve function.
Because CSF circulates, it allows the exchange of nutrients and waste products between the blood and nervous tissue.
What is the total volume of CSF?
The total volume is ~ 80-150 mL
What does CSF contain?
CSF contains glucose proteins, lactic acid, urea, Na+, K+, Ca2+, Mg2+, Cl-, HCO3-, it also contains some white blood cells.
Label this image and where does the CSF flow?
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What/where is the CSF made?
What’s it made from and how?
- Networks of capillaries in the walls of the ventricles, these are covered with ependymal cells it is these which make CSF from the blood plasma by filtration and secretion and forms the blood-cerebralspinal fluid barrier.
- This permits certain substances to enter CSF whilst blocking other potentially harmful substances.
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What does the mid brain do?
This area of the brain relays motor output from the cerebral cortex to the pons. It relays sensory input from the spinal cord to the thalamus
What do the superior and inferior colliculi do?
The superior colliculi coordinates the movement of your eyes in response to visual stimuli.
The inferior colliculi coordinates head and trunk in response to auditory stimuli.
What does the substantia nigra and red nucleus do?
Most of the substantia nigra and red nucleus are concerned with the control of movement.
The substantia nigra is the area of the brain which produces the neurotransmitter dopamine.
Lack of dopamine results in Parkinson’s disease.
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What does the pons do?
This area relays impulses from one side of the cerebellum to the other and between the medulla and mid brain.
With the medulla it is also important in the control breathing.
What does the medulla oblongata do?
Relays sensory input and motor output between the brain and spinal cord there seems to be a function in arousal and consciousness.
Regulates heartbeat blood vessel diameter and breathing, also vomiting, cough reflex, swallowing and sneezing.
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What does the cerebellum do?
- Integration of sensory perception and motor output
- Constant feedback on body position allows fine movement, lesions do not result in paralysis but problems with fine motor movement, posture and motor learning
- Cognitive function, attention, processing language, music and other temporal stimuli
What does the diencephalon comprise of?
Thalamus
Hypothalamus
Epithalamus
Ventral Thalamus
Third ventricle
What does the thalamus do?
•Provides crude perception of pain heat etc, it is also involved in movement planning and control.
What does the hypothalamus do?
- Controls and integrates the autonomic nervous system and pituitary gland.
- It regulates emotion and behaviour.
- It regulates eating and drinking and maintains sleep patterns.
- It has endocrine function as it produces the hormones oxytocin and ADH.
What is the epithalamus?
Consists of the pineal gland which secretes melatonin and the habenular nuclei, the function of this area is poorly understood.
What is the cerebrum, physical properties?
Largest part of brain, divided into two halves, the right and left cerebral hemispheres
The folds and convolutions of the surface of the cerebral hemispheres vastly increase the effective surface area of the brain.
Each ridge is called a gyrus and each groove between ridges is called a sulcus. A deep sulcus is referred to as a fissure.
What is the cerbrum responsible for?
- Perception of sensory information, motor control
- Complex cognitive functions such as memory intelligence and personality
- Basal ganglia regulate the muscle tone of your body and coordinate gross automatic muscle movements
- The limbic system seems to be involved in the emotional aspects related to survival ‘FEAR’
How has mapping of the brain progressed over the years?
Traumatic injuries
Electroencephalogram, Hans Berger recorded the first human EEG in 1924
Computed tomography scan
Positron emission tomography
MRI
Functional MRI
How do computed tomography scans work in imaging the brain?
This uses a series of X-ray beams passed through the head, this gives cross sectional images of the brain.
How does positron emission tomography work?
The scanner detects radioactive material injected or inhaled, the substance enters the blood stream and goes to the areas of the brain that use the substance.
The substance decays via beta decay releasing a positron. When the positron hits an electron, both are destroyed and two gamma rays are released. It is the gamma rays that are detected. This method provides a functional picture of the brain.
How do MRI scans work to image the brain?
MRI scanners detect radiofrequency signals produced by relaxation of protons (hydrogen nuclei) in a magnetic field to give anatomical views of the brain.
What can a functional MRI do that an MRI can’t?
fMRI can detect blood flow to particular areas of the
brain, so gives both functional and anatomical information.
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What does the premotor cortex do?
Co-ordinates voluntary movements
What do the prefrontal association areas do?
Idea and plan for voluntary movement, thoughts, personality.
What does Broca’s area do?
Speech formation
What does the olfactory cortex do?
Smell
What does the limbic association cortex do?
Emotions, learning, memory
What does the primary auditory cortex do?
Hearing
What do the auditory association areas do?
Processes acoustic (sound) signals that the brain interprets as sounds, speech or music.
What does Wernicke’s area do?
Language comprehension
What does the primary visual cortex do?
Vision
What do the visual association areas do?
Higher vision processing
What do the sensory association areas do?
Integration of sensory information
What does the primary somatosensory cortex do?
Somesthetic sensations and proprioception
What does the central sulcus do?
The primary motor cortex from the primary somatosensory cortex.
What does the primary motor cortex do?
Voluntary movement
What does this image depict?
The homunculus,
A representation of the body, based on the amount of cerebral cortex dedicated to each region.
What does this image show?
What causes it?
- Stroke
- This can be caused by inter-cerebral haemorrhage from a blood vessel in the pia mater or brain, the formation of blood clots or artherosclerosis.
- There is a rapid onset of persisting neurological symptoms.
- Risk factors: high blood pressure, high cholesterol, heart disease, diabetes, smoking, obesity and alcohol abuse.
What are the two major types of stroke?
Ischemic
Haemorrhagic
Describe an Ischemic stroke?
In an ischemic stroke a blood vessel becomes blocked, usually by a blood clot and a portion of the brain becomes deprived of oxygen and will stop functioning.
Ischemic strokes are most commonly caused by blockages in the carotid arteries and are responsible for up to 80% of strokes.
When does a haemorrhagic stroke occur?
Occur when blood vessels rupture. (bleeding)
What are the 4 possible reasons for an Ischemic stroke?
- Thrombosis (obstruction of a blood vessel by a blood clot forming locally)
- Embolism (obstruction due to an embolus from elsewhere in the body)
- Systemic hypoperfusion (general decrease in blood supply, e.g., in shock)
- Cerebral venous sinus thrombosis. (the presence of acute thrombosis (a blood clot) in the dural venous sinuses, which drain blood from the brain)
What’s an embolus?
A blood clot, air bubble, piece of fatty deposit, or other object which has been carried in the bloodstream to lodge in a vessel and cause an embolism.
What are the two main types of haemorrhagic stroke?
Cerebral haemorrhagic
Subarachnoid haemorrhagic
What is a Cerebral haemorrhagic stroke?
Also known as intracerebral hemorrhage, which is basically bleeding within the brain itself (when an artery in the brain bursts, flooding the surrounding tissue with blood), due to either intraparenchymal hemorrhage (bleeding within the brain tissue) or intraventricular hemorrhage (bleeding within the brain’s ventricular system).
What is a Subarachnoid haemorrhagic stroke?
Bleeding that occurs outside of the brain tissue but still within the skull, and precisely between the arachnoid mater and pia mater (the delicate innermost layer of the three layers of the meninges that surround the brain).
What does F.A.S.T stand for with a stroke?
Face fallen on a side
Arms above head
Speech slurred
Time to call 999
Describe the effects of Alzheimer’s disease?
AD sufferers loose the ability to reason.
They become progressively dependent on others, because they can not care for themselves.
The cause is unknown, but it is very common.
Eventually the sufferer loses the ability to read, write, talk, walk, eat.
What disease has caused the change in this brain?
Alzheimer’s disease
What does this image show?
- Formation of b-amyloid plaques
- Neurofibrillary tangles
Explain bacterial meningitis?
The pia-arachnoid matter is congested and infiltrated with inflammatory cells, a layer of pus forms and this organises to form adhesions which obstruct the free flow of CSF.
The CSF pressure rises rapidly and its protein concentration increases, this leads to a cellular reaction, which can often prove fatal.
Symptoms: Headache, drowsiness fever and neck stiffness.
Why are brain tumours so bad?
What is shown in this image?
All brain tumours are potentially fatal, whether they are malignant or not.
This is because the brain is confined in the cranium and is unable to expand, therefore the tumour compresses the healthy brain tissue.
In some cases tumours can be completely removed by surgery or treated by chemo or radiotherapy.
Glioma- type of tumor that starts in the brain or spine. It is called a glioma because it arises from glial cells. The most common site of gliomas is the brain. Gliomas make up about 30% of all brain and central nervous system tumors and 80% of all malignant brain tumors.
