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Mid Semester Exam > Nervous System ll > Flashcards

Nervous System ll Flashcards

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Nervous system classification:

What is the CNS? What parts make it up?

A

The CNS is the central nervous system - it consists of the brain and spinal cord. It is the integrating and control centre of the nervous system. It interprets sensory input and dictates motor output (based on reflexes, current conditions and past experience).

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Nervous system classification:

What is the PNS? What does it consist of?

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The peripheral nervous system is a part of the nervous system outside of the CNS. It consists mainly of nerves (axon bundles) from the brain and spinal cord and ganglia (collection of neuron cell bodies)

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Nervous system classification:
How are nervous pathways categorised? What are the two categories of nervous pathways?

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Nervous pathways are categorised into divisions according to the direction in which they carry information. The main nervous pathways are the afferent division (carry toward brain) and efferent division (carry away)

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Nervous system classification:
What does the afferent division in the peripheral nervous system consist of + do?

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The afferent division consists of all the incoming or ‘afferent’ pathways. It translates to carry toward

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Nervous system classification:
What does the afferent division in the peripheral nervous system consist of + do?

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The efferent division consists of all the outgoing motor or ‘efferent’ pathways. Translates to carry away

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Nervous system classification:
What are the two motor/efferent pathway classifications of the peripheral nervous system?

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The somatic nervous system (SNS- directly controls the skeletal muscles), and autonomic nervous system (ANS - controls smooth muscles, cardiac muscles, glands, adipose tissue and other involuntary tissues). It is further categorised into the sympathetic and parasympathetic

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Nervous system classification:
What part of the nervous system is the parasympathetic nervous system and sympathetic nervous system?

A

Part of the autonomic nervous system (ANS), which is part of the peripheral nervous system (PNS) overall

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Nervous system classification:
What is the role of the parasympathetic nervous system? What is it sometimes referred to as?

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The parasympathetic nervous system is responsible for coordinating the body’s regular resting activities. It exits the lower part of the brain or the spinal cord. It is often called the ‘rest and relax/digest’ system

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Nervous system classification:
What is the role of the sympathetic nervous system? What is it commonly referred to as?

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The sympathetic nervous system is responsible for preparing the body for ‘fight or flight’ response. It exits the brain in the middle section of the spinal cord. It is commonly referred to as the ‘fight or flight’ system

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Cell anatomy - Neuron Structure:

Which two types of cells make up nervous tissue?

A
  • Neurons
  • Glial cells (support cells): can be called neuroglia
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Cell anatomy - Neuron Structure:

What is each neuron cell made up of?

A
  • Cell body (nucleus and organelles)
    Dendrites - branching projections (for incoming information)
  • Axon - A single elongated projection that carries impulses away from the cell body
  • Myelin sheath - Covers and protects the axon fibres; increasing transmission rate. Is a white, fatty material .
  • Synapse - A point where two cells meet. There is a junction between the dendrite and the axon
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Cell anatomy - Neuron structure:
How do synapses work?

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Information is sent via chemical molecules called neurotransmitters across the synaptic cleft between the 2 cells. They lock into a specific receptor site, allowing an electrical charge to take place resulting in the relay of the nerve signal

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Cell anatomy - Neuron structure:

What parts of the neuron make up the ‘input zone’? - What is its function?

A
  • Dendrites and soma (cell body).
  • The input zone of the neuron receives input from other neruons or from sensory stimuli (stimulated gated ion channels present).
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Cell anatomy - Neuron structure:

What parts of the neuron make up the ‘summation zone’? - What is its function? What is this zone commonly referred to as?

A
  • The summation zone is commonly referred to as the ‘axon hillock’ zone.
  • It is located at the point in which the axon originates from the cell body.
  • It serves as the site where the nerve impulses combine and possibly trigger an impulse that will be conducted along the axon—or conduction zone. Both the summation (trigger) zone and conduction zone have many voltage-gated Na + channels and K + channels imbedded in the plasma membrane
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Cell anatomy - Neuron structure:

Where is the ‘output zone’ of a neuron located? What is its function?

A
  • The output zone (distal end of axon) is where the nerve impulse triggers the release of neurotransmitters. The output zone includes many voltage-gated Ca ++ channels in the membrane.
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Cell anatomy - Neuron injury and regeneration:

(CNS)

  • Why will there typically be no regeneration/cell repair in neurons?
A

Because unlike other cells, they lack the supply of ‘stem cells’ that create new neurons

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Cell anatomy - Neuron injury and regeneration:

What typically happens to damaged axons?

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They will slowly degenerate, become irregular, breakdown, and then disappear

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Cell anatomy - Neuron injury and regeneration:

What method can be used to identify damaged axons?

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Axonal injury protein staining methods can be used to identify damaged axons: * APP, a transmembrane protein normally transported within axons, accumulates and becomes visible when axonal transport is disrupted, indicating injury.
Methods:*

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Cell anatomy - Neuron injury and regeneration:

Lack of communication signals can impair other neurons
At times the CNS neurons can reorganise and other areas of the brain can take over the damaged role (plasticity)

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Cell anatomy - Neuron injury and regeneration: NOTES

  • PNS: Neurons have the ability to repair, depending on the circumstances.
  • The closer the injury to the cell body of the nerve cell, the greater the chance the nerve cell will die and not regenerate.
  • Schwann cells are required to form a tunnel for the neuron to repair
A

Crushed nerve cells sometimes recover fully, whereas cut nerves can form connective tissue scars that block or slow regenerating axonal branches.
When cut, a damaged axon of a motor neuron can regrow to its distal connection only if the Schwann cells remain intact (to form a guiding tunnel) and if scar tissue does not block its way.

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23
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What is required to form a tunnel for damaged neurons to repair?

A

Schwann cells

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Glial Cells: Types

What is the location, function and description of Glia cells?

A

Location: Brain, spinal cord and nerves
Function: Structural and functional support of neurons
Description: Support cells; far outnumber neurons

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Glial Cells: Types What is the location, function and description of Astrocytes?
Location: CNS Function: Promote nervous tissue development: provide nutrients to neurons, restore ion balance: help to form and regulate synapses; part of blood brain barrier Description: Central body with many radiating prcoesses
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Glial Cells: Types What is the location, function and description of microglia?
Location: CNS Function: Engulf microbes + debris, prune neural circuits Description: Very small and stationary, but can enlarge and move when stimulated
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Glial Cells: Types What is the location, function and description of ependymal cells?
Location: CNS Function: Line fluid space, propel fluid (help create CSF in choroid plexus**) Description: Form sheets with motile cilia
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Glial cells: Types What is the location, function and description of oligodendrocites?
Location: CNS Function: Form insulating myelin sheath around CNS nerve fibres, which promotes rapid conduction along neurons Description: Central body with processes that wrap around neuron processes
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Glial cells: Types What is the location, function and description of Schwann cells?
Location: PNS Function: Entire cell wraps around neuron processes, outer portion called neurilemma Description: Form insulating myelin sheath around CNS nerve fibres, and this promotes rapid conduction along neurons; promotes regeneration of damaged nerve fibres
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Neuron Cells: Types What is the location, function and description of a Neuron cell?
Location: Brain, spinal cord, nerves Function: Detect stimuli, conduct impulses, signal other cells Description: Central body with fibre like processes
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Neuron Cells: Structural types What is the location, function and description of a multipolar neuron?
Location: Brain and spinal cord Function: Processes (integrates) information, conduct impulses along motor pathways Description: Single axon, multiple dendrites
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Neuron Cells: Structural types What is the location, function and description of bipolar neurons?
Location: Retina, inner ear, olfactory pathway Function: Conduct information along sensory pathways Description: Single axon, single highly branched dendrite
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Neuron Cells: Structural types What is the location, function and description of unipolar neurons (psuedounipolar)? - unipolar only found in invertebrates, pseudounipolar found in humans**
Location: Sensory pathways Function: Conduct information along sensory pathways Description: Single process branches to form a central and peripheral process
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What type of neuron cell are unipolar, multipolar and bipolar neurons?
Sensory neurons
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What are the three different types of functional neurons?
Sensory, Motor, Interneurons
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What does a sensory neuron do?
- Send afferent information to the CNS - Translate physical and chemical signals to electrical signals (action potentials), then carry them from PNS to CNS
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What does a motor neuron do?
- Transmit efferent information out from the CNS to an effector (muscle or organ) - In skeletal muscle the innervation of the muscle by a motor neuron forms the neuromuscular junction
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What do interneurons do?
- Send impulses from neuron to neuron (sensory to motor - acting as intermediate*) - Located in the CNS - Connect signals between different sensory neurons, enabling multiple systems to be integrated
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Cell anatomy - Neuron Physiology: What is a reflex?
A reflex is a rapid, predictable and involuntary response to stimuli. The reflex action takes place out of our conscious control. These nerve impulses can reach speeds of up to 100m/s
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What do all reflex arcs have? (arc referring to the neural pathway of the reflex)
1. Sensory receptor (respond to stimuli) 2. Sensory (afferent) neurons 3. Interneurons 4. Motor (efferent) neurons 5. Effector organ (muscle/gland eventually stimulated)
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Where are most cell bodies found within the PNS?
In ganglia - clusters of cell bodies.
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Cell anatomy - Sensory receptors: Thermoreceptor - - Location - Detects?
- Located in the skin - Detects temperature (e.g cool, hot)
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Cell anatomy - Sensory receptors: Nocireceptor - - Location - Detects?
- Skin, viscera (organs of abdomen/chest), muscle - Detects pain (damage)
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Cell anatomy - Sensory receptors: Mechanoreceptors - - Location - Detects?
- Skin, viscera, muscle, ear - Touch, pressure, stretch, vibration (hearing)
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Cell anatomy - Sensory receptors: - Chemoreceptors - - Location - Detects?
- Blood vessels, brain, nose, mouth - Chemicals (e.g acid, sour), taste, smell
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Cell anatomy - Sensory receptors: Poprioreceptors - - Location - Detects?
- Muscle - Body positioning
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Cell anatomy - Sensory receptors: - Photoreceptors - Location - Detects?
- Eye - Light (vision)
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Cell anatomy: NOTES Bundles of nerve fibres (neuron processes) running through the CNS are called tracts – no connective tissue coverings Whereas in the PNS they are called nerves, held together by several layers of connective tissue that form a myelinated sheath (image below) White matter consists of dense collections of myelinated fibres (tracts) Grey matter contains mostly unmyelinated fibres and cell bodies in CNS
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CNS - Brain anatomy: (protection) - What are the three main avenues for nervous system protection in the brain?
1. By enclosing them within bone (skull and vertebral column, covered in musculoskeletal system) 2. Membranes (meninges) 3. Cerebro Spinal Fluid (CSF) - a 'watery cushion' - The blood brain barrier (BBB) provides protection from harmful substances in the blood
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CNS: Brain Anatomy What do the meninges (brain membrane) consist of?
Three layers of connective tissue membranes covering and protecting the CNS structures: - Dura mater - Arachnoid mater - Pia mater
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What do the meninges provide?
Provide support for the rich network of blood vessels serving the brain tissues
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What arises from the meninges?
The choroid plexuses (that create CSF)
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What is cerebrospinal fluid?
Clear, colourless fluid that is similar to plasma and intersitial fluid
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What is the function of cerebrospinal fluid?
- Buoyant properties of CSF prevent the brain from pulling on the meninges, nerve roots and blood vessels - Acts as a shock absorber - Constantly moves around the brain and maintains a set volume and pressure
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CNS: Consciousness What does the term 'consciousness' refer to?
A state of being conscious. Being aware of oneself and the environment, and with the ability to enact a set of typical and characteristic responses to that environment
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CNS: Consciousness NOTES: on RAS and glasgow coma scale
- Reticular activating system (RAS) The fully conscious individual responds to external stimuli, such as noise, light, pain and temperature changes, with a wide array of responses. - Any decrease in this state of awareness and responsiveness is considered a decrease in consciousness and affects the Glasgow Coma Score
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CNS: Sleep Define 'sleep'
- Considered a state of partial unconsciousness - Brain stem functional, and can be aroused from sleep - RAS fundamental role is regulating arousal and sleep wake transitions
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CNS: Memory What does each thought involve in the process?
Neuronal circuits in portions of the cerebral cortex, thalamus, limbic system, and reticular formation of the brainstem
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Where is a memory stored?
A memory is not stored in one particular place - rather it is the outcome of a pattern or circuit of neuronal activation.
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What component of a thought is the limbic system supposedly though to determine?
The emotional value of the thought/memory - e.g pleasant, painful or neutral (particularly in the amygdala)
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What component of a thought are the neurons in the cerebral cortex thought to determine?
The details of the thought (e.g specific details)
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What are two prerequisites to thinking?
Consiousness and memory
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What is memory phenomenon?
A synaptic phenomenon in which neurons in the memory trace/circuit alter the efficiency of synaptic transmission
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What results in longer lasting effects of memory?
Greater stimulation of neurons in the memory circuit
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How can a memory trace/circuit be reactivated, once it has been established?
It can be reactivated by the thinking mind to reproduce the memory
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Memory: NOTE
- The mechanisms for different types of memory are mostly unknown
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Imbalance of brain: TBI (traumatic brain injury) Define a TBI?
- A complex mixture of two principal insults - primary brain injury, and secondary brain injury
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Imbalance of brain: TBI (traumatic brain injury) What causes a primary brain injury?
Caused by external forces on the skull and brain structures at the time of injury
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Imbalance of brain: TBI (traumatic brain injury) What causes a secondary brain injury?
Damage to the brain that results from both primary brain injury, and from acute disorders of the respiratory and cardiovascular system (e.g hypoxia, ischaemia, increased ICP (increased intracranial pressure)
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Imbalance of the brain: Cerebrovascular accident (CVA) What is CVA used to describe?
Both brain accidents and strokes
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Imbalance of brain: TBI (traumatic brain injury) How does a stroke occur?
When there is inadequate blood flow (ischaemia) to a part of the brain, or haemorrhage (bleeding) into the brain that results in the death of brain cells
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Imbalance of brain: TBI (traumatic brain injury) What functions are lost/impaired during a stroke?
Functions such as movement, sensations, thinking, talking or emotions, that were controlled by the affected area of the brain are lost or impaired
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Imbalance of brain: TBI (traumatic brain injury) - Stroke What does the severity of loss of function depend on?
The location and extent of the damage to the brain EG If blood flow to the brain is totally interrupted (e.g., cardiac arrest), neurologic metabolism is altered in 30 seconds, metabolism stops in 2 minutes, and cell death occurs in 5 minutes.
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Imbalance of brain: Dementia Define dementia?
A disorder characterised by a decline from the 'normal' level of function in one or more cognitive domains: - complex attention - executive function - language - learning and memory - perceptual motor - social cognition The cognitive decline interferes with the ability to function and perform daily activities
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Imbalance of brain: Dementia What causes dementia?
Both treatable and untreatable conditions: - Treatable: (infections, medications, metabolic, regular head injuries or nutrition diseases) - Untreatable: (Plaques, damaged neurons, loss of connections between neurons, neurofibre tangles alter brain structure and function) - Treatable causes may initially be reversible. However, irreversible changes can occur with prolonged exposure or disease.
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Imbalance of brain: Alzheimer's Define Alzheimer's disease?
A chronic, progressive, irreversible neurodegenerative brain disease
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Imbalance of brain: Alzheimer's How long can the 'preclinical' phase of alzheimer's last for?
Up to 20 years. The average 'clinical' duration is 4-8 years
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Imbalance of brain: Alzheimer's NOTES
Exact cause of Alzheimer's is unknown Women are more likely to develop Alzheimer's because they live longer
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Imbalance of brain: Alzheimer's What can an early onset of alzheimer's disease indicate?
A pattern of familial genes
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Imbalance of brain: Chronic neurological conditions - Define parkinson's disease?
A chronic neurological disorder characterised by slowness in the initiation and execution of movement (bradykinesia), increased muscle tone (rigidity), tremor at rest, and gait changes (patterns of walking)
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Imbalance of brain: Chronic neurological conditions - Define Huntington's disease?
A progressive, degenerate brain disorder causing deterioration of physical, emotional and cognitive abilities. It is a genetically transmitted, autosomal dominant disorder (meaning if you have the gene you will have the disease).
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Imbalance of brain: Chronic neurological conditions - Defined Multiple Sclerosis (MS)?
MS is a chronic and unpredictable progressive degenerative disorder of the CNS. It is characterised by disseminated demyelination of nerve fibres of the brain and spinal cord. There are four types of MS with differing characteristics
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Imbalance of brain: Chronic neurological conditions - What are the four types of MS (multiple sclerosis)?
1. Relapsing remitting: Clearly defined attacks of worsening neurologic function (relapses) with partial or complete recovery (remission). 85% of people first diagnosed with this type. 2. Primary progressive: Steadily worsening neurologic function from the beginning with minor improvements but no distinct relapses or remissions. 10% of people first diagnosed with this type. 3. Secondary progressive: relapsing-remitting initial course, followed by progression with or without occasional relapses, minor remissions, and plateaus. New treatments may slow progression. Most people initially diagnosed with relapsing remitting MS eventually transition to this type 4. Progressive relapsing: Progressive disease from onset, with clear acute relapses, with or without full recovery. Periods between relapses are characterized by continuing progression. 5% of people with MS.
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Spinal cord - Anatomy: Where is the spinal cord located?
In the vertebral canal
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Spinal cord - Anatomy: What is the approximate length of the spinal cord?
Around 42cm long
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Spinal cord - Anatomy: What is the spinal cord?
- It is a continuation of the brain stem – extending from the foramen magnum of the skull to the first or second lumbar vertebrae - It is a two-way conduction pathway to and from the brain
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What is the spinal cord protected/cushioned by?
The meninges NOTE: Meningeal coverings extend past L2 (unlike spinal cord), the area inferior to L2 is ideal for removing CSF for testing
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Spinal cord: Anatomy NOTES
the vertebral column grows faster than the spinal cord, the spinal cord does not reach the end of the vertebral column, and the spinal nerves leaving its inferior end must travel through the vertebral canal for some distance before exiting.
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Spinal cord: Anatomy What is the spinal cord composed of?
H shaped grey matter (nerve cell bodies) surrounded by white matter (nerve tracts and fibres) The collection of spinal nerves at the inferior end of the vertebral canal is called the cauda equina (it looks similar to a horse's tail)
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How does spastic paralysis occur?
If the spinal cord is damaged
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Spinal cord: FURTHER NOTES
- If Spinal cord is damaged, spastic paralysis occurs - Spinal shock occurs immediately after injury and is characterized by temporary loss of reflexes below the level of injury - The affected muscles stay healthy due to spinal reflex arc stimulation, however movements are involuntary and not controllable - Loss of sensory input occurs below areas of damage – this can increase change of infection later as those with spinal cord injuries (SCI) are unable to feel whether there is a damage to the skin or something else, and often experience sepsis regularly
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Spinal cord - Birth disorders What creates the spinal cord and brain during development?
The neural tube
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Spinal cord - Birth disorders What can a neural tube defect cause?
Birth disorders - most of which occur very early on in pregnancy as the brain and spinal cord develop (neural tube defects)
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Spinal cord - Birth disorders What is spina bifida?
- The developmental anomaly characterised by defective closure of the neural tube (more common) - Incomplete closure of the skin and bones around the spinal cord and meninges exposes them to amniotic fluid in utero - Folic acid supplementation taken before conception and during pregnancy appears to decrease the prevalence of neural tube defects.
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PNS - Describe PNS?
PNS is a part of the nervous system outside of the CNS
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What does the PNS mainly consist of?
- nerves (axon bundles), extending from the brain and spinal cord and ganglia (collections of neural cell bodies)
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PNS: What is a nerve?
A bundle of neuron fibres found outside the CNS
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PNS: what are cranial nerves?
Nerves that originate from the brain and exit through the skull
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PNS: what are spinal nerves
Nerves that originate in the brain and do not exit the spinal cord
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PNS: how many pairs of - cranial - spinal ... nerves are found in the body?
- 12 pairs of cranial nerves - 31 pairs of spinal nerves
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Nerves: NOTES
- Within a nerve, neuron fibres, or processes, are wrapped in protective connective tissue coverings. Each fibre is surrounded by a delicate connective tissue sheath, an endoneurium. Groups of fibres are bound by a coarser connective tissue wrapping, the perineurium to form fibre bundles, or fascicles. Finally, all the fascicles are bound together by a tough fibrous sheath, the epineurium, to form the cordlike nerve
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PNS: NERVES notes
They are wrapped in protective connective tissue coverings Bundles are called fascicles, and these are bound together to form cord like nerve These nerves are myelinated with Schwann cells
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PNS: Notes
The PNS is not protected by CSF, meninges or bony coverings PNS serves both afferent sensory functions and efferent motor functions of the somatic and autonomic systems A large group of nerves that merge is called a plexus (plexuses) In the plexus the nerve fibres are recombined into different groups and emerge as peripheral nerves Due to the recombination the spinal nerves and peripheral nerves have different somatic distributions The knowledge of the innervations from the groups can allow clinicians to differentiate between spinal nerve compression or peripheral neuropathy
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Mid Semester Exam (8 decks)

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