Nervous system structure and function Flashcards
What is gastrulation?
Defined as an early development process in which an embryo transforms from a 1D layer of epithelia cells (blastula) and reorganises into a multilayered and multidimensional structure called gastrula.
What is the primitive streak?
An elongated band of cells that forms along the axis of a developing fertilised egg early in gastrulation and is considered a forerunner of the neural tube and nervous system.
Primitive streak is a linear band of thickened epiblast that first appears at the caudal end of the embryo and grows cranially. At cranial end its cells proliferate to form the primitive knot (primitive node).
What is the germ layer formulation?
The germ layers form during the process of gastrulation, when the hollow ball of cells that constitutes the blastula begins to differentiate into more-specialized cells that become layered across the developing embryo.
What is the outermost layer of germ cells known as and when is it formed?
Ectoderm (outermost layer of germ cells) - 1 of the 3 primary germ layers formed in early embryonic development
What are the examples of ectoderm found in the body?
- Epidermis
- Mouth
- Teeth
- Nostrils
- Hair
- Nails
- Nervous system
What is the middle germ layer called and where is it devloped?
Mesoderm (middle layer of germ layer) - develops during gastrulation in very early development
What are the examples of mesoderm found in the body?
- Muscle
- Connective tissue
- Heart
- Blood vessels
- Some organs (kidneys)
What is innermost layer of germ cells called where is formed?
Endoderm (innermost layer of germ cells) - of an embryo in source of the epithelium of the digestive tract and the lower respiratory tract
What are the examples of endoderm found in the body?
- GI tract
- Respiratory system
- Liver
- Pancreas
- Thymus
- Thyroid
- Bladder
Where is neural tube formed?
Forms the early brain and spine - the CNS.
What happens when errors occur in the neural tube?
Errors in this process can lead to congenital anomalies such as neural tube defects.
What is the 2 most common neural tube defects?
The 2 most common neural tube defects are spinal bifda (a spinal cord defect) and anencephaly (a brain defect).
What happens when neural crest fusion fails?
Neurocristopathies are a group of diseases caused by the abnormal generation, migration or differentiation of neural crest cells.
Involve multiple organ systems in a single person, often familial - associated of neoplasms.
What cells make up 10% of the nervous system and what is its function?
Principle cells (10%)
- Neurons
- Projection, communication
What cells make up 90% of the nervous system and what is its function?
Gila (90%):
Astrocytes: specialised glial cells that outnumber neurons by over fivefold. They regulate blood flow, but also transfer mitochondria to neurons and supply the building blocks of neurotransmitters which fuel neuronal metabolism
Metabolic support
Where are interneurons found and what is its function?
Ones in between - connect spinal motor and sensory neurons
Found in brain/spinal cord - others within autonomic ganglia.
Function of interneurons is integration.
Local modulation
What is microglia, where is it found and what is its function?
Microglia are resident macrophages of the CNS.
Plays key role in brain development and physiology during life and aging.
What is the function of phagocytotic?
Phagocytotic: process for ingesting and eliminating particles larger than 0.5 um in diameter including microorganisms, foreign substances and apoptotic cells.
What is the structure and function of Oligodendrocyte (CNS)?
Function: in CNS oligodendrocytes assemble myelin, a multi-layered sheath of membrane, spirally wrapped around axonal segments and best known for its role in enabling fast saltatory impulse propagation.
Structure: have small amounts of cytoplasm’s surrounding rounded nuclei. 2 main types: satellites around neurons in the Gray matter. Myelin-forming cells in the white matter.
What is the function and structure of - Schwann cell (PNS) ?
Function: role in development, maintenance, function, and regeneration of peripheral nerves. Can be myelinating/non-myelinating cells.
Structure: form thick myelin sheath or an intended plasma membrane that folds around peripheral axons in the PNS. Schwann cell covers an axon, outer cell surface is called neurilemma - shields axon from interstitial.
What is the function and structure of - Myelination?
Function: allows more rapid transmission of neural info along neural fibres. Critical in cerebral nervous system depends on long axon connections between hemispheres, lobes and cortical and subcortical structures.
Structure: Myelination is the process by which brain oligodendrocytes produce layers of myelin that wrap around the neuronal axons and act as a layer of insulation for the transmission of electric action potentials down the neuronal axon.
What is the central nervous system organs and their function?
Central:
- Brain
- Spinal cord
- Processing of sensory input
- Generate motor output
What is the peripheral nervous system nerves involved?
Peripheral:
- Peripheral nerves
- Cranial nerves (12 pairs)
- Spinal nerves (31 pairs)
What is the function of the meninges?
Function: Provide a supportive framework for cerebral and cranial vasculature. Acting with cerebrospinal fluid protect the CNS from mechanical damage,
Meninges common site of infection (meningitis) and intracranial bleeds.
What are the 3 layers in the meninges?
3 layers: DURA MATER, ARACHNOID MATER, PIA MATER.
What are the 3 layers of the dura mater and its structure and function?
Dura mater:
Outermost layer of meninges - located directly underneath bones of skull and vertebra; column.
Thick, rough and inextensible.
Periosteal layer: lines the inner surface of the bones of the cranium
Meningeal layer: located deep to the periosteal layer. Continuous with dura mater of spinal cord.
What is the Dural venous sinuses responsible for and where is it located?
Dural venous sinuses located between 2 layers of dura mater - responsible for venous drainage of cranium and empty into the internal jugular veins.
Receives own vascular supply - middle meningeal artery and vein.
What are the 4 Dural reflections and its function?
Meningeal layer of dura folds inwards itself to form 4 Dural reflections.
Falx cerebri: projects downwards to separate the right and left cerebral hemispheres.
Tentorium cerebelli: separates the occipital lobes from the cerebellum. It contains a space anteromedially for passage of the midbrain - the tentorial notch.
Flax cerebelli: separates the right and left cerebellar hemispheres.
Diaphragm sellae: covers the hypophysial fossa of the sphenoid bone. It contains a small opening for passage of the stalk of the pituitary gland.
What is the arachnoid mater?
Middle layer of meninges lying underneath the dura mater.
Consists of layers of connective tissue, is avascular doesn’t receive any innervation.
Underneath arachnoid is a space known as sub-arachnoid space - contains cerebral fluid which acts to cushion brain.
Small projections of arachnoid mater into dura (known as arachnoid granulations) allow CSF to re-enter the circulations via the Dural venous sinuses.
What is the pia mater?
Located underneath sub-arachnoid space.
Very thing and tightly adhered to surface of brain and spinal cord.
Only covering to follow contours of brain (gyri and fissures).
Highly vascularised with blood vessels perforating through membrane to supply the underlying neutral tissue.
What is the function of cranial fibres?
Carry fibres connecting brain with head and neck.
What is the function of spinal nerves?
Carry fibres between spinal column and neck, thorax, abdomen, pelvis, limbs.
Pairs of nerves emerge between spinal vertebrae.
C1 to C7 above corresponding vertebra C8, T1 to T12, L1 to L5, S1 to S5, Co below corresponding vertebra
What are dermatome?
Dermatome is an area of skin that is mainly supplied by single spina or cranial nerve.
What are myotome?
Myotome is a group of muscles which is innervated by single spinal nerve root.
The brain structure known as hindbrain contains which part of the brain and what is its function?
- Medulla oblongata
- Pons
- Basic survival functions
- Breathing
- BP
- sleeping
The brain structure known as midbrain contains which part of the brain and what is its function?
- Thalamus
- Hypothalamus
- Pituitary gland
- Basic awareness
- Endocrine control
- Thirst
- Hunger
The brain structure known as cortex contains which part of the brain and what is its function?
- Neocortex
- Cerebellum
- Consciousness
- Thinking
- Memory
- Motor skills
- Special senses.
The autonomic nervous system contains cranial and spiral nerves?
Cranial nerves - 3,7,9,10 - parasympathetic
Spiral nerves T1 to L2 - sympathatic, S2 to S4 - parasympathetic
What is the nervous systems function?
- Signaling
- Integration
What is the function of nerves in communication?
Inputs coordinated with outputs
Graded signaling: differential responses.
What are the 3 primary roles of the spinal cord?
send motor commands from the brain to the body
send sensory information from the body to the brain
coordinate reflexes.
What is the sensory homunculus?
Map along cerebral cortex of where each part of body is processed.
Sensations occur all along the body.
Impulses from body will be sent into spinal cord and eventually back to brain to be processed
What is the function of the motor cortex and what part of the brain can be found in?
Generate signals to direct the movement of the body
Part of frontal lobe and anterior central sulcus.
Consists of primary motor cortex, premotor cortex and supplementary motor area.
What do sensory (afferent) neurons do?
Transport sensory info from skin, muscles, joints, sense organs & viscera to CNS.
What does the Motor (efferent) neurons do?
Send motor nerve impulses to muscles & glands.
What does Interneurons (association) neurons connect?
Connect sensory to motor neurons.
90% of neurons in the body.
What is the charge of the action potential at the resting membrane potential , at depolarisation and at repolarisation?
Resting membrane potential is -70mV. Depolarisation is change from -70mV to +30mV
Repolarization is reversal from +30mV back to -70mV.
What are the 2 types of synapses for signal transmission?
2 types of synapses:
Electrical:
- Ionic current spreads to next cell through gap junctions
- Faster two-way transmission and capable of synchronizing groups of neurons.
Chemical:
- One-way info transfer from a presynaptic neuron to a postsynaptic neuron.
- Axodendritic: from axon to dendrite
- Axosomatic: from axon to cell body
- Axoaxonic: from axon to axon
What are chemical synapses?
Action potential reaches end bulb
Voltage-gated Ca^2+ channels open
Ca^2+ flows inward triggering release of neurotransmitter.
Neurotransmitter crosses synaptic cleft
Binds to ligand-gated receptors.
Synaptic delay is 0.5 msec
One-way info transfer.
What is an Agonist?
Agonist:
- Anything that enhances a transmitters effect
What is an Antagonist?
Antagonist:
- Anything that blocks action of a neurotransmitter.
What are the symptoms, causes of Parkinson’s disease?
Parkinson’s disease:
Symptoms:
- Rigidity
- Muscle tremors
- Difficulty initiating movement + mental activity
- Depression
Causes:
Progressive death of dopamine producing neurons in the substanita nigra and amygdala
These areas help coordinate movement.
