L23 & 24: Central Nervous System and Control Flashcards
Which organ exerts centralised control over the other organs?
Brain
What is a benefit of centralised control?
Allows rapid and coordinated responses to changes in environment
How does the brain act on the rest of the body?
1) Generating patterns of muscle activity
2) Driving secretion of hormones
Why does sophisticated purposeful control of behaviour require the brain?
Complex sensory inputs require the information-integrating capabilities of the brain.
(It can understand and combine multiple sensory inputs)
What are the 4 functions of glial cells?
1) To surround neurons and hold them in place
2) To supply nutrients and oxygen to neurons
3) To insulate one neuron from another
4) To destroy pathogens and remove dead neurons
50% of CNS is made up of neuroglia, the other 50% is neurones. Where would tumours occur in adults? Is this different in children?
In adults, tumours occur in the neuroglia because adult neurones don’t divide. In children, they can occur in the neurones because their neurones are dividing as brain development takes place
How does cerebral spinal fluid provide protection for the brain?
Acts as a cushion to lessen impact of blow to the head
Where is the occipital lobe located?
To the rear of the brain, beneath the occipital bone of the skull
Where is the parietal lobe located?
On the side of the brain, beneath the parietal bone of the skull
Where is the frontal lobe located?
At the front of the brain, beneath the frontal bone
What are neuroglia?
Non-neuronal cells that support the brain
e.g. maintain homeostasis, form myelin, support and protect neurones
What are the 6 types of neuroglia?
- Satellite cells
- Schwann cells
- Oligodendrocytes
- Astrocytes
- Microglia
- Ependymal cells
What is the role of satellite cells?
- Surround neuron cell bodies in ganglia
- Regulate O2, CO2, nutrient, and neurotransmitter levels around neurons in ganglia
What is the role of Schwann cells?
- Surround axons in peripheral nervous system (PNS)
- Responsible for myelination of peripheral axons
- Participate in repair process after injury
What is the role of Oligodendrocytes
- Myelinate central nervous system (CNS) axons
- Provide structural framework
What is the role of astrocytes?
- Maintain blood-brain barrier
- Provide structural support
- Regulate substance concentrations
- Absorb and recycle neurotransmitters
- Form scar tissue after injury
What is the role of microglia?
- Remove cell debris, wastes, and pathogens by phagocytosis
What is the role of ependymal cells?
- Line ventricles (brain) and central canal (spinal cord)
- Assist in producing, circulating, and monitoring cerebrospinal fluid
What type of cell forms the choroid plexus, where cerebrospinal fluid is produced?
Ependymal cells
Which cells line the ventricles (brain) and central canal (spinal cord)?
Ependymal cells
Ependymal cells are involved with a fluid called cerebrospinal fluid. This fluid surrounds the brain and spinal cord; what are its functions?
- Protection - acts as a cushion for the brain
- Buoyancy - relieves pressure on the brain stem by floating the brain
- Excretion - CSF flows in a one-way system, and carries waste and toxins away from the brain
- Endocrine medium for the brain - transports hormones around the brain
Fill in the gap:
In early development/childhood, ependymal cells are ciliated. By adulthood, ciliation is limited to __?__.
the ventricles
True or false:
The main role of ependymal cells is sensory
True (e.g monitoring the composition of the CSF)
Fill in the gap:
In adults, the ependymal contains __?__ that can divide to produce additional neurones
stem cells
True or false: Ependymal cells have slender processes which contact other neuroglia, their role is unknown.
True
Which are the largest and most numerous of central nervous system neuroglia?
Astrocytes
Do dissolved compounds in blood have free access to the cerebrospinal fluid?
No, access is regulated by blood brain barrier (which is formed by endothelial cells and maintained by astrocytes)
What is the blood brain barrier comprised of?
Endothelial cells that form the blood vessels. Because they are leaky, astrocytes wrap around the capillaries to plug any holes.
How do astrocytes help in the structure of the CNS?
- Create cytoskeleton framework for neurons to build on
2. Build structures that prevent further harm to damaged neural tissue
Why is important to keep axons isolated from each other? What cells help with this?
To prevent cross firing. Oligodendrocytes and Schwann cells
What is the difference between Schwann cells and oligodendrocytes?
Schwann cells myelinate axons in the PNS and oligodendrocytes myelinate axons in the CNS. Schwann cells wrap their bodies around a single axon; oligodendrocytes have many processes that reach out to axons, allowing them to myelinate multiple axons at once.
What does myelination do to the speed of impulse transmission?
Increases transmission speed
You see a glial cell with many processes. Some are connected to a capillary while its other processes are connected to neuron axons. Which type of glial cell are you observing?
Astrocyte.
Astrocytes provide a link between the vasculature and neurons, transporting glucose and other substances out of the bloodstream
What is the main role of myelin?
The main role of myelin is to mediate rapid saltatory propagation of action potential between Nodes of Ranvier, thereby facilitating neuro-transmission
Which glial cells are immune effectors in the CNS?
Microglia
Which demyelination condition is autoimmune brought on by viral infection?
Guillain-Barre syndrome
How does diphtheria cause demyelination?
Destroys Schwann cells
Which demyelination condition affects axons in optic nerve, brain and spinal cord?
Multiplesclerosis
Which of the glial cells is responsible for CSF production?
Ependymal
Which glial cell maintains the blood brain barrier?
Astrocytes
Which glial cell clears up waste and pathogens?
Microglia
Which glial cell myelinates CNS neurons?
Oligodendrocytes
Which glial cell monitors the composition of the cerebrospinal fluid (CSF)?
Ependymal
Which glial cell may be damaged by diphtheria?
Schwann cells
Which glial cells guide neural development?
Astrocytes
What protection does the brain have?
Cranium, cranial meninges, cerebrospinal fluid, blood-brain barrier
What are the cranial meninges?
Pia mater, arachnoid, dura mater. Layers that absorb shock
What is the endosteal layer of the meninges?
A sublayer of the dura mater. It is at the top and is fused to the cranial bones.
What is the meningeal layer of the dura mater?
The inner layer that forms the contact with the arachnoid layer
The dura mater consists of 3 sublayers, with gaps between each one. What are these gaps for?
Containing tissue fluids and blood vessels, including large venous sinuses. Veins of the brain open into these sinuses
Which layer of the meninges contains trabeculae and creates a smooth surface that does not follow the brains folds?
Arachnoid
What anchors the pia mater to the brain?
Astrocytes
Is meningitis caused by bacterial or viral infection?
It can be either
What effect does meningitis have?
Disrupts circulation of CSF, killing neurons and neuroglia. Bacteria and neutrophils turn CSF milky.
True or false: The CNS is fed nutrients primarily from CSF
False, CSF is primarily for protection. Primarily fed by nutrients absorbed across the blood brain barrier
Describe the journey taken by CSF
- Produced ibythe choroid plexus in the ventricles
- Travels from lateral ventricles to the third ventricle via interventricular foramen.
- Travels down the midbrain through the cerebral aqueduct.
- Leaves cerebral aqueduct through either lateral or median aperture, or continues down the central canal of spinal cord.
- Enters subarachnoid space and cycles back up to the brain.
- Enters the superior sagittal sinus via arachnoid villus.
- Finally CSF is reabsorbed into venous circulation.
True or false: Neurons can store some glucose to use for energy later on
False. Because of their inability to store energy, neurons require an extensive blood supply
Which arteries supply the brain?
Carotid and vertebral arteries
Which veins carry blood away from the brain?
Jugular veins (drain the dural sinuses)
What are pericytes?
Contractile cells that form part of the blood brain barrier. They help regulate blood flow.
Why is it difficult to manufacture drugs that can treat CNS diseases (e.g. meningitis)?
The blood brain barrier is very difficult to cross, and it is hard to trick it to allow a drug across
How is the CNS protected from physical damage?
Cushioned by cerebrospinal fluid, cerebral meninges, cranium
What are the three main functions of CSF?
Protection/cushion, buoyancy for brain, transport soluble nutrients
How and where is CSF produced?
Produced in ependymal cells of choroid plexus in ventricles
What is the blood-brain barrier? How is it produced? What is its main function?
Layer of astrocytes around the capillaries, prevent fluid and particles from crossing to the brain cells.
Where is the BBB disrupted normally? Why does this occur?
Around the endocrine glands, allows hormones to pass into blood
What are the cranial meninges and what is their function?
Dura mater, arachnoid, pia mater. Serve to cushion the brain, and to allow flow of CSF
Many water soluble molecules that are abundant in the blood only occur in small amounts in the extracellular fluid of the brain. Why?
Astrocytes prevent them from crossing the BBB
Most of the brain is dominated by the cerebrum. It is divided into two __1__ __2__.
- cerebral
2. hemispheres
What is the neural cortex?
Grey matter that covers the cerebrum
What is the function of the cerebrum?
The seat of most higher mental functions, conscious thought, intellect, memory
Cerbral cortex comprises of ridges (__1__) which increase its surface area, small grooves (__2__), and large grooves (__3__).
- gyri
- sulci
- fissures
What is the function of the cerebellum?
Fine motor. Allows you to perform the same movements over and over.
Adjusts ongoing movements by comparing arriving sensations with previously experienced sensations - relays to the cerebellum.
What are the two main components of the diencephalon?
Thalamus and hypothalamus
What is the main function of the thalamus?
Contains final relay and processing centres for most sensory pathways, filters information sent to cerebral cortex
What are the 8 functions of the hypothalamus?
- Subconscious control of skeletal muscle
- Control of autonomic function
- Coordinates activities of the nervous and endocrine system
- Produces oxytocin and ADH
- The production of emotional and behavioural drives (e.g. feeding and thirst centres)
- Coordination between voluntary and autonomic functions
- Regulation of body temperature
- Control of circadian rhythms
Which component(s) connects the hypothalamus to the pituitary gland?
Infundibulum
Which component(s) is/are responsible for integration of nervous and endocrine systems?
Hypothalamus and pituitary gland
What component links the cerebral hemispheres to the brain stem?
Diencephalon
What are the three divisions that make up the brain stem?
Midbrain
Pons
Medulla
What is the key unique function(s) of the midbrain?
Processing audio-visual stimuli and processing AV-related reflexes
What does the red nucleus of the midbrain do?
Issues subconscious motor commands to the limbs
What does the black nucleus (substantia nigra) of the midbrain do?
Regulates activity in basal nuclei (basal ganglia)
What is the function of the pons?
Connects cerebellum to brain stem and is involved with somatic and visceral motor control. Contains nuclei involved in respiration - pneumotaxic centre.
What is the function of the medulla oblongata?
Connects brainstem to the spinal cord. Contains ALL sensory and motor tracts, relays to the thalamus.
Reflex centres involved in cardiovascular and respiratory rhythmicity.
Contains sensory and motor nuclei of cranial nerves
What is the corpus callosum?
Band of nervous tissue that connects the cerebral hemispheres
Which hemisphere is responsible for sensory and motor control of the left side of the body?
The right hemisphere
Which hemisphere is responsible for sensory and motor control of the right side of the body?
The left hemisphere
Which hemisphere is responsible for logic, numeracy, and language?
The left hemisphere
Which hemisphere is responsible for recognition of faces and facial expressions?
The right hemisphere
Which hemisphere is responsible for musical and artistic awareness?
The right hemisphere
Which hemisphere would be responsible for generating mental images to compare spatial relationships?
The right hemisphere
The central sulcus separates the __1__ lobe and the __2__ lobe
- frontal
2. parietal
The lateral sulcus separates the __1__ lobe and the __2__ lobe
- frontal
2. temporal
FRONTAL LOBE:
What are the functions of the pre-frontal cortex?
Higher level thought, decision-making, planning and organising,
Inhibiting impulses and actions.
Personality
FRONTAL LOBE:
What are the functions of the motor cortex?
Processes and transmits information regarding body movement and position.
Plans and coordinates fine movements via basal ganglia
What are the functions of the parietal lobe?
Primary sensory cortex - touch, pressure etc.
Spatial orientation and information processing.
Memory for numeracy and spelling.
What are the functions of the temporal lobe?
Auditory processing, memory, dreams, language, understanding
What are the functions of the occipital lobe?
Main vision centre - processes info from the eyes.
