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1003 > Nervous System > Flashcards

Nervous System Flashcards

1
Q

Where is the brain located and where does it lead to?

A

The brain is encased in the top of the skull

The base of the brain leads down to the spinal cord

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2
Q

What is the skull supported by?

A

The skull is supported by the spinal column, which is supported by the shoulders

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3
Q

What are the 4 regions and organisations of the brain?

A
  1. Cerebral hemisphere
  2. Diencephalon (thalamus, hypothalamus)
  3. Brain stem
  4. Cerebellum
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4
Q

Draw the organisation of the four regions of the brain

A

See lecture notes

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5
Q

Describe the ventricles of the brain

A

Hollow ventricular chambers, filled with cerebrospinal fluid and lined with ependymal cells which is a type of neuralgia

The human brain has 4 ventricles

  • two lateral ventricles
  • a third ventricle in the diencephalon region
  • in the brain stem
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6
Q

Discuss the structures of the cerebral hemispheres

A

They make up 83% of total brain mass

The surface of the cerebral hemispheres are covered in ridges called gyri (singular gyrus) and grooves called sulci (singular sulcus)

Some sulci are used to divide the brain into anatomical regions termed lobes

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7
Q

Name the lobes of the brain

A 
Frontal 
Parietal 
Temporal 
Occipital 
Cerebellum
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8
Q

Draw the structure of the brain and label the lobes

A

See lecture notes

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9
Q

What are the functions of the cerebral cortex?

A 
Communication 
Language processing 
Sense interpretation e.g. vision, auditory 
Understanding 
Memory 
Voluntary movement (motor processing)
Conscious behaviour
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10
Q

What is the cerebral correct composed of?

A 
Grey matter
Neuronal cell bodies 
Dendrites 
Unmyelinated axons
Glia 
Blood vessels
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11
Q

What three functional areas are contained in the cerebral cortex?

A
  • Motor areas
    Control voluntary motor function
  • Sensory areas
    Provide conscious awareness of sensation
  • Association areas
    Act to integrate information for purposeful function e.g. walking

But the brain works as a whole, global integration

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12
Q

What hemisphere is responsible for which side of the human body?

A

Each hemisphere is responsible for the function of the opposite side of the human body I.e. the right hemisphere governs the left side of the human body

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13
Q

Where is the primary motor cortex located and what does it consist of?

A

Located in the frontal lobe
Consists of large neutrons called pyramidal cells
Large scones that project down the spinal cord to control skeletal muscle movement. Termed the corticospinal tract

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14
Q

What are the three parts of the motor area of the cerebral cortex?

A

Premotor cortex
Located in the frontal lobe
Controls learned motor skills e.g. playing a musical instrument

Broca’s area
Located in the frontal lobe anterior to premotor cortex
Involved in co-ordinating speech muscles e.g. tongue

Frontal eye field
Controls eye movement

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15
Q

What is the sensory area of the cerebral cortex?

A

Somatosensory cortex
Integrated all sensory input for example input from skin (pressure and temperature sensors), vision, olfactory (smell), gustatory (taste) and auditory (sound) information

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16
Q

What is the association area of the cerebral cortex?

A

The parts of the brain that are not primarily involved in specific functions.

Regions of the cerebral cortex that integrate information from other cortical areas and provide a level of consciousness

This is one of the most complex roles played by the brain

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17
Q

What is cerebral Dominance determined by?

A

Language dominance

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18
Q

What does ambidexterity mean?

A

Co-dominance of both hemispheres

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19
Q

What is dyslexia

A

Lack of cerebral dominance. This does not affect intelligence

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20
Q

What is the diencephalon

A

Central core of the brain

Surrounded by the cerebral cortex

Consists of three structures:
Thalamus
Hypothalamus
Epithalamus

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21
Q

What is the thalamus

A

Contains many nuclei that relay information to other regions of the brain e.g. vision and auditory relay centres

It acts as an editing centre And provides direction of motor information

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22
Q

What is the hypothalamus?

A

Major homeostatic processor and regulator

Autonomic control centre: regulates involuntary nervous system e.g. blood pressure and respiratory rate

Centre for emotional response and behaviour e.g. pain, fear, rage

Body temperature regulation, sweating and shivering responses

Regulation of food intake

Regulation of water balance and thirst

Regulation of the sleep wake cycle

Control of endocrine functions

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23
Q

What is the epithalamus?

A

Poorly understood area of the brain

Appears to play a role in the sleep wake cycle along with the hypothalamus

Regulates melatonin levels via the pineal gland

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24
Q

What does the brain stem consist of?

A

Midbrain

Pons

Medulla Oblongata

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25
Q

Describe the position and function of the midbrain

A

Above the pons

Holds up the cerebellum

Co-ordinates head and eye movement in response to visual stimuli e.g. following an object

Sound reflexes e.g. turning your head when you hear your name

Contains the substantia nigra which plays an important role in reward and movement and is effected in patients with Parkinson’s disease

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26
Q

What is the function of the pons?

A

Integrates information from the motor cortex and cerebellum (balance)

A pneumotaxic centre- regulation of respiration together with the medulla

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27
Q

What is the medulla oblingata?

A

Forms the cavity of the fourth ventricle

Autonomic reflex centre involved in maintaining body homeostasis

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28
Q

The medulla oblongata is the centre for what responses?

A

Cardiovascular centre:
Adjusts the force and rate of heart contraction
Regulates blood pressure by vasodilation/vasoconstriction

Respiratory centre:
Rate and depth of breathing
Maintain respiratory rhythm with pons

Other centres:
Regulates reflexes such as; vomiting, hiccupping, swallowing coughing, sneezing

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29
Q

What is the cerebellum?

A

Accounts for 11% of the brains mass

Integrates information from the cerebral motor cortex, proprioceptors throughout the body, visual and equilibrium pathways

Proprioceptors: Receptors sending information about muscle tension, tendon and joint position

Acts to maintain posture and estimate force to ensure smooth, co-ordination movement

Ultimately, the cerebellum sends orders to the motor cortex to fine tune movement

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30
Q

Define proprioceptors

A

Receptors sending information about muscle tension, tendon and joint position

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31
Q

What are the three main protectors of the brain?

A

The skull (cranium) and its many layers

Cerebrospinal fluid

The blood brain barrier

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32
Q

What are the three protective layers within the cranium?

A

Dura matter
Thick tough membrane underneath the skull

Arachnoid matter
Thin membrane, projecting to the pia matter through the subarachnoid space

Pia matter: envelopes the contours of the brain suface and dips into the sulci

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33
Q

What is cerebrospinal fluid and what is its function

A

Cerebrospinal fluid surrounds the entire brain and plays an important role in maintain a constant intracerebral chemical environment

Helps protect the brain form mechanical damage by reducing the effect of impact damage experienced by the head

CSF is secrete by the choroid plexus with is found in the lateral ventricles

The ventricular volume is around 75ml

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34
Q

Describe the route of blood supply to the brain

A

The blood brain barrier:
The blood brain barrier is both a physical barter and a system of cellular transportation mechanisms

It maintains homeostasis by restricting the entrances of potentially harmful chemicals from the blood whilst still allowing the entrance of essential nutrients

Lipid soluble molecules such as ethanol and caffeine are able to penetrate through the barrier relatively easily via the lipid membranes of the cells. In contrast, water soluble molecules such as sodium and potassium ions are unable to transverse the barrier without the use of a specialised carrier - mediated transport mechanisms

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35
Q

What are the two major roles of the peripheral nervous system?

A

To send inflation about the environment to the brain

To transmit information to the effector organs of the human body

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36
Q

What are sensory receptors and how are they classified?

A

They respond to changes in their environment

Environmental changes are called stimuli

There are three basic ways to classify sensory receptors:

1: by their location in the body
2: by the type of stimulus they detect
3: by the relative complexity of their structure

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37
Q

Discuss how sensory receptors are classified by location:

A

Exteroceptors:
Sensitive to stimuli from outside of the body e..g touch, pressure, pain and temperature receptors in skin

Interceptors (visceroceptors)
Sensitive to stimuli from within the body
E.g. chemical receptors, tissue stretch receptors and temperature (internal)

Proprioceptors:
Respond to internal stimuli
Location is much more restricted that interceptors
Located in skeletal muscle, tendons, joints, ligaments and connective tissue coverings of bones and muscles
Constantly inform the brain of our movements and positions by the degree of stretch of the organs they occupy

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38
Q

How are sensory receptors classified by stimulus type detection?

A

Mechanoreceptors:
Generate nerve impulses when they, or adjacent tissues are deformed by mechanical forces e.g. touch, pressure (including blood pressure) vibrations and stretch

Thermoreceptors: sensitive to temperature changes

Photoreceptors: retinal photoreceptors

Chemoreceptors: respond to chemical changes

Nociceptors: respond to damaging stimuli that result in pain

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39
Q

How are sensory receptors classified by structural complexity?

A

Free dendritic endings:
Sensory neutrons
Innervate tissue
Form merkel discs that attach to deep layers of the skin and function as light touch receptors
Root hair plexus Ed wrap around hair roots and function as light touch receptors

Encapsulated dendritic endings:
Dendritic endings are enclosed in connective tissue to form a capsule like structure
Virtually all encapsulated receptors are mechanoreceptors
Meissners corpuscles: pressure sensors on hairless skin e.g. lips and fingertips
Krauses end bulbs: sensors on connective tissue
Pacinian corpuscles: sensors on skin, tendons and ligaments
Muscle spindles: sensors within skeletal muscle
Golgi tendon organs: sensors in tendons

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40
Q

What is meissners corpuscles:

A

Pressure sensors on hairless skin e.g. lips and fingertips

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41
Q

What are krauses end bulbs?

A

Sensors on connective tissue

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42
Q

What are pacinian corpuscles?

A

Sensors on skin, tendons and ligaments

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43
Q

What are golgi tendon organs?

A

Sensors in tendons

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44
Q

What do uncapsulated receptors in the skin detect?

A

Pain and movement

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45
Q

What do encapsulated receptors in the skin detect?

A

Pressure and temperate

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46
Q

What are sensor receptor potentials?

A

Stimuli acting on receptors are converted into electrical signals, by these reports, that the brain can understand

Receptor potentials are generated in graded stages

These receptors are capable of relating the intensity of a stimulus to electrical output e.g. depolarisation

Basically, the greater the stimulus, the greater the graded depolarisation event

These receptors also show adaptation

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47
Q

What is the spinal column and describe the structure

A

The route of sensory transmission to the brain

The route of reflex arc processing/ connections

Structure: 
Made up of vertebrae that can be divided up into the following regions: 
- cervical 
- Thoracic 
- lumbar 
- sacral
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48
Q

What is the functions of the spinal column?

A

To provide protection from spinal cord and peripheral nerves

To provide support for the upper torso and skull

To provide and integration channel for all nerves entering/ leaving the central nervous system

Relaying information to and form the brain to peripheral organs

To provide flexible motion

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49
Q

What is the spinal cord?

A

Lies encased within the spinal column

Bundles of nerves relaying information to and from the brain

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50
Q

What is reflex activity?

A

Involuntary response initiated by the stimulus

A reflex response can be protective or homeostatic, however it is there to maintain body integrity andc function

A reflex tends to occur through the spinal cord without the involvement of the brain

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51
Q

List the components of a reflex arc?

A

Receptor: site of stimulus action

Sensory neuron: transmits affront impulses to the CNS

Integration centre: within the CNS, can be a single interneuron or a network of neural connections

Motor neuron: impulses from the CNS to the effector organ

Effector: muscle fibre or gland that responds to the stimulus

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52
Q

Draw and label a simple reflex arc

A

See lecture slides

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53
Q

What are muscle spindles?

A

Located within skeletal muscle

Act as stretch receptors

Respond to increases/decreases in muscle contraction

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54
Q

What is the anatomy of muscle spindles?

A

Intramural fibres: acts as the receptive surface of the spindle
These fibres are wrapped with two types of sensory fibres:
Primary fibres: respond to the rate and amount of stretch
Secondary fibres: respond to the degree of stretch

Gamma fibres: cause the intrafusal fibres to contract (small contractions only)

Alpha fibres: cause the gross contraction of muscle

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55
Q

What are intrafusal fibres?

A

Intrafusal fibres: acts as the receptive surface of the spindle
These fibres are wrapped with two types of sensory fibres:
Primary fibres: respond to the rate and amount of stretch
Secondary fibres: respond to the degree of stretch

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56
Q

What are gamma fibres?

A

Cause the intrafusal fibres to contract (small contractions only)

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57
Q

What are alpha fibres?

A

They cause the gross conduction of the muscle

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58
Q

What does muscle spindles in recruitment mean?

A

Muscles spindles act to recruit muscle fibres during muscle contraction

For example: when lifting a heavy object, initially your muscles will estimate the weight (via the brain),however if the object is heavier than anticipated, the muscle spindles will stretch on limiting and cause recruitment of muscle fibres i.e. to allow you to apply more force in lifting

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59
Q

What is the stretch reflex?

A

Golgi tendon organ:
Located at the end of the skeletal muscle at site of bone attachment
Responds to stretch: mechanoreceptors
Proprioceptors

A tap on the patellar tendon induces a stretch reflex i.e. the golgi tendon organ is stretched

This then sends signals to the CNS via afferent sensory neurons

Via interneuronal pathways the extensor muscle is excited whilst the flexor muscle is inhibited through efferent innervations

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60
Q

Outline the roles/ organisation of the peripheral nervous system

A

See lecture notes

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61
Q

Describe the location classification used fro sensory receptors

A

See lecture notes

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62
Q

Describe the stimulus detection classification used for sensory receptors

A

See lecture notes

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63
Q

Describe the structural complexity classification used fort the sensory receptors

A

See lecture notes

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64
Q

Describe the structure organisation and function of the spinal cord

A

See lecture notes

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65
Q

Draw a labelled diagram of a spinal cord cross section

A

See lecture notes

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66
Q

Outline the components of a reflex arc

A

See lecture notes

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67
Q

Describe the anatomy of muscle spindles and their role in muscle fibre recruitment

A

See lecture notes

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68
Q

Describe the stretch reflex

A

See lecture notes

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69
Q

Describe the location of the human brain

A

See lecture notes

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70
Q

Label a diagram of the major regions of the brain

A

See lecture notes

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71
Q

Outline the major composition and functions associated with the cerebral cortex

A

See lecture notes

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72
Q

Outline the major functions associated with the diencephalon, to include the thalamus, hypothalamus and epithalamus

A

See lecture notes

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73
Q

Label a diagram of the anatomical regions that make up the brain stem

A

See lecture notes

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74
Q

Outline the functions associated with the brain stem

A

See lecture notes

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75
Q

Outline the functions associated with the cerebellum

A

See lecture notes

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76
Q

What protecting mechanisms are in place for the Brain?

A

See lecture notes

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77
Q

Compare the somatic and autonomic nervous system

A

See lecture notes

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78
Q

What are effectors?

A

The somatic nervous system stimulates skeletal muscle

The ANS innervates cardiac and smooth muscles and glands

The different physiology off the effector organs accounts for the differences between somatic and autonomic effects on target organs

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79
Q

What are efferent the pathways and ganglia:

A

Within the somatic nervous system, the cell bodies lie in the CNS and their axons extend to skeletal muscles (monosynaptic)

These axons tend to be:
Thick
Myelinated fibres
They conduct nerve impulses very fast

In the autonomic nervous system:
The motor unit is a two chain neuron
The cell body of the first neuron (preganglionic neuron) resides in the brain or spinal cord
It’s axon synapses with a secondary motor neuron, the postganglionic is neuron is an autonomic ganglion outside the CNS
The postganglionic axon extends to the effector organ

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80
Q

Draw the efferent pathways of the autonomic nervous system

A

See lecture slides

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81
Q

What are the effects of neurotransmitters?

A

The somatic motor neutrons release acetylcholine and are always excitatory

The ANS utilised noradrenalin/adrenaline or acetylcholine

Within the ANS the response can either be inhibitory or excitatory depending on the receptors present at the target organ

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82
Q

Draw the neurotransmitters of the somatic and autonomic nervous systems

A

See lecture notes

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83
Q

Discuss the overlap of somatic and autonomic function

A

Higher bran centres regulate and co-ordinate both motor and visceral (internal organ) motor activities

The bodies adaptation to the environment involves both skeletal muscle and enhancements to certain visceral organd

Example running; somatic nervous system inducing skeletal muscle contraction within the legs. The ANS increase heart rate and respiratory rate

Both systems work together

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84
Q

What are the divisions of the ANS?

A

There are two parts to the ANS:

Parasympathetic division: performs maintenance activated and conserves body energy

Sympathetic division: utilised under extreme conditions ‘fight or flight’ response

Innervate the same target organs

However one has an excitatory effect and the other has an inhibitory effect

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85
Q

What does the parasympathetic division do?

A

Performs maintenance activities and conserves the bodies energy

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86
Q

What does the sympathetic division do?

A

Utilised under extreme conditions ‘fight or flight’ response

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87
Q

What is the role of the parasympathetic division?

A

Most active in non-stressful conditions

Acts to conserve energy

The parasympathetic division acts as follows at rest:
Reduces blood pressure
Reduced heart rate
Reduced respiratory rate
Increase rate of digestion (especially following a meal)
Pupillary constriction (reducing retina damage)

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88
Q

What are the signs that the parasympathetic division is at rest

A

The parasympathetic division acts as follows at rest:
Reduces blood pressure
Reduced heart rate
Reduced respiratory rate
Increase rate of digestion (especially following a meal)
Pupillary constriction (reducing retina damage)

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89
Q

What is the role of the sympathetic division?

A

Fight or flight response

Active when we are engaged in an excitatory, emergency or life threatening situation

The sympathetic division acts as follows under the above conditions:
Pounding heart
Rapid deep breath
Cold, sweaty skin
Dilated pupils
Changes in Brian waves and electrical conductivity of skin

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90
Q

What are the signs the sympathetic division has been activated?

A 
Pounding heart 
Rapid deep breath 
Cold, sweaty skin 
Dilated pupils 
Changes in Brian waves and electrical conductivity of skin
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91
Q

Describe and compare the innervations of the ANS divisions e.g. what happens to body systems at sympathetic division and parasympathetic division

A

See lecture diagram

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92
Q

What sympathetic adjustments occur during exercise?

A

Visceral organ blood vessels are constricted

Vessels of the heart and skeletal muscles are dilated

This causes blood to be directed mainly to the heart and exercising skeletal muscle

Dilation of the bronchioles to increase ventilation

Temporary reduction in non-essential activity (for exercise) e..g gastrointestinal and urinary tract motility

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93
Q

Discuss the physiology of the ANS

A

Neurotransmitters:
Acetylcholine (ACh) and noradrenalin/adrenaline are the major neurotransmitters of the ANS

ACh is predominantly utilised by the majority of parasympathetic neurons

Fibres that release ACh are called cholinergic fibres

The sympathetic nervous system utilities both ACH and noradrenalin/ adrenalin (from adrenergic fibres)

94
Q

All ACh receptors are either:

A

Nicotine or muscarinic (named after drugs that were first used to discover these receptors)
ACH binding to nicotinic receptors is always stimulatory e..g muscle contraction

ACh binding to muscarinic receptors can be wither excitatory or inhibitory e.g. slows down heart activity whereas increase gastrointestinal tract motility

95
Q

Show the typical response to stress

A

See lecture slides

96
Q

What has been developed to block the inhibitory and excitatory effects of the ANS

A

Drugs such as atropine and anticholinesterase

97
Q

What does atropine do?

A

Dilutes pupils before surgery

98
Q

What doe santicholinesterase drugs do?

A

Drugs such as neostigmine act to inhibit the breakdown of ACh. Used in a condition called myasthenia graves where skeletal muscle activity is impaired due to reduced ACh.

99
Q

Discuss the interactions of the ANS

A

Antagonistic interactions:
Clearly seen in the fight or flight response
The sympathetic nervous system increases e.g. heart rate, ventilation during a fight or flight response, however afterwards the parasympathetic system reduces these effects

100
Q

What is sympathetic tone?

A

E.g. vascular system, where the vessels are constantly in a state of partial constriction

This allows blood pressure to increase rapidly, as these constrictions can provide pulses to further push the blood along

Alpha blockers act to reduce sympathetic tone and decrease blood pressure

101
Q

What is sympathetic tone?

A

Reduces the endogenous rate of function of specific organs
E.g. reduces heart rate below its endogenous rhythm. This is also true of the respiratory system

Pharmacological blockers act to increase the parasympathetic tone e.g. increase heart rate

However, the sympathetic nervous system can override the influences of the parasympathetic nervous system

102
Q

Describe the differences between the somatic and autonomic nervous system:

A

See lecture notes

103
Q

Describe the structural organisation of the ANS neuronal pathway

A

See lecture notes

104
Q

Outline the roles of the two divisions of the ANS

A

See lecture notes

105
Q

List the sympathetic adjustments that occur during exercise

A

See lecture notes

106
Q

List the receptors of the ANS and their associated activation neurotransmitters

A

See lecture notes

107
Q

Outline the response to a stressful situation on heart rate

A

See lecture notes

108
Q

Outline the functions of sympathetic and parasympathetic tone

A

See lecture notes

109
Q

Define neurons and glia

A

The cells from which the nervous system is assembled

110
Q

Define neurons

A

Process and transmit information

Include synapses
Found in the whole of the nervous system
~ 100 distinct types

111
Q

Define neuroglia

A

Support neurons and modulate neuronal function

Specific types of glia for each part of the nervous system

There are more glia than there are neurons (10:1)

112
Q

Draw and label the anatomy of a neuron

A

See lecture notes

113
Q

Describe the anatomy of neurons

A

Process and transmit information in the form of nerve impulses

High degree of morphological and functional asymmetry, 
Neutrites; 
Receptive dendrites 
Transmitting axons 
Synapses

Electrically and chemically excitable

114
Q

Draw the structures of

A) multipolar interneurons
B) Motor neurons
C) sensory neurons

A

See lecture notes

115
Q

Draw the pain withdrawal reflex arc

A

See lecture notes

116
Q

Draw the pain withdrawal reflex showing the peripheral nervous system and central nervous system

A

See lecture notes

117
Q

What are glial cells

A

They support neurons and modulate neuronal functions

118
Q

What do oligodendrocytes and Schwann cells do?

A

Form the insulating sheaths of axons

119
Q

What is an oligodendrocyte and where are they found?

A

One oligodendrocyte can produce myelin sheaths for segments of as many as 30 axons

Found in the central nervous system

120
Q

What are Schwann cells and where are they found?

A

One Schwann cell can produce myeloma sheath for only one segment of a single axon

As many as 500 Schwann cells can participate in the myelination of a peripheral axon

Found in the peripheral nervous system

121
Q

What is the purpose of myelin sheaths?

A

They allow rapid conduction of electrical signals along the axon

Lack of myelination slows down or prevents the conduction of electrical signals alone the axon

122
Q

What do astrocytes do?

A

Participate actively in synaptic transmission

123
Q

Draw the process of synaptic transmission in the central nervous system

A

See lecture notes

124
Q

What are the supporting roles of astrocytes?

A

Scaffold of the CNS (structural role)

Clear out synapses e.g. excess glutamate can become toxic

Regulate neurotransmitter concentrations:
Uptake of excess glutamate
Convert glutamate to glutamine
Transfer glutamine to neurons, where glutamine is the precursors or glutamate

Nourish neurons:
Lactate as a neuronal energy substrate

Promote the development of synapses

125
Q

What part of the body are astrocytes active components of?

A

The blood brain barrier

126
Q

What are astrocytes endfeet?

A

Not much of a structural role

Provide nourishment to endothelial cells that form the bbb

Filtering of unwanted and possibly harmful substances

127
Q

What are microglia

A

Microglia play an important role in immunological surveillance of the CNS

They are poised to react to foreign invaders of the CNS

128
Q

What do microglia do at resting state?

A

They scan the interstitial fluid

129
Q

When do microglia work in their active state?

A

Because of signs of inflammation

Presence of bacteria (infection)

130
Q

What are the functions of microglia?

A

Phagocytosis: clearing debris

During inflammation;
Secrete cytokines and chemokines that will serve to trigger an immune reaction
Antigen presentation to lymphocytes

131
Q

What are ependymal cells

A

They assist with the move of cerebrospinal fluid CSF though the ventricular system

132
Q

What is the purpose of CSF

A

It functions as a shock absorber fluid cushion for the brain and the spinal cord

133
Q

What are ependymal cells

A

They are a single layer of ciliated cuboidal epithelial cells

They line the ventricular system

Barrier between the CAF and interstitial fluid

Secretion of CSF

134
Q

How do neurons communicate?

A

Neurons are excitable cells and communicate via action potentials

A synapse is an anatomically specialised junction between two cells

One single neuron can synapse onto many other post synaptic cells. This is called divergence

Many synapses from different presynaptic neurones can synapse with a single cells which is called convergence

135
Q

Define synapse

A

Anatomically specialised junction between two cells

136
Q

What is divergence

A

One single neuron can synapse onto many other post synaptic cells

137
Q

What is convergence

A

Many synapses from different presynaptic neurons can synapse with a single cell

138
Q

What is the function of divergence in neuron communication

A

A mechanism for spreading stimulation to multiple neurons or neuronal pools in the CNS

139
Q

What is the purpose of convergence in the communication of neurons

A

A mechanism for providing input to a single neuron from multiple sources

140
Q

What are the two types of snynapse

A

Electrical synapse and chemical synapse

141
Q

What is an electrical synapse

A

An electrical synapse is a gap junction

Plasma membranes of cells are joined by gap junctions

Local ionic currents flow from one cell to the next through gap junctions

Communication is extremely rapid

142
Q

What is a chemical synapse

A

Operates through the release of neurotransmitters

143
Q

Draw an electrical synapse diagram

A

see lecture notes

144
Q

Draw a chemical ‘tripartite’ synapse

A

See lecture notes

145
Q

Draw and label a diagram showing the release of neurotransmitters through chemical synapses

A

See lecture notes

146
Q

Draw and label a diagram showing the action of drugs pm a chemical synapse

A

See lecture notes

147
Q

How can a drug work on chemical synapses?

A

A drug might:

1) increase leakage of neurotransmitter from vesicles to cytoplasm in the pre-synaptic neuron
2) increase neurotransmitter release into cleft
3) block neurotransmitter release
4) inhibit transmitter synthesis
5) block neurotransmitter reuptake
6) block cleft enzymes that metabolise neurotransmitter
7) bind to receptor on post synaptic membrane
8) inhibit or stimulate second messenger activity in the post synaptic cell

148
Q

Describe the communication of neurons

A

Information is carried within neurons and from neurons to their target cells by electrical and chemical signals

149
Q

Describe the electrical forces between ions

A

Opposite charged ions attract each other

Charges of the same type repel each other

The electrical force of attraction increases with the quantity of charge

150
Q

What is the electrical potential of extra cellular and intracellular

A

The potential difference across the membrane will be ~69mV

151
Q

Draw and label a cell and show the charges within and outside of the cell and discuss what the membrane potential is

A

See lecture notes

Positive and negative ions will be on both sides of the neurons membrane

Excess positive charges will be outside of the cell

Excess negative charges will be inside the cell

This is the membrane potential

152
Q

Draw and label a diagram of the plasma membrane

A

See lecture notes

153
Q

Discuss the resting potentials of neurons

A

An electrical gradient is maintained across the plasma membrane (treated negative charge inside the cell), thus making the cell polarised

The cell also has a concentration gradient I.e. there is a different in the distribution of ions between the inside and outside of a membrane

154
Q

Discuss the electrical and concentration gradients across the plasma membrane of a typical neuron

A

Extracellular:
Na+ : 145mM
K+ : 5mM
Cl- : 100mM

Intracuellar: 
Na+ : 15mM 
K+ : 150 mM 
Cl- :7mM
OA- :high concentration of organic anions

When a typical neuron is at rest with a voltage across the membrane of ~60mV

155
Q

What ions are in higher concentration outside of the cell

A

Na+ and Cl-

156
Q

What ions are higher in concentration inside of the cell

A

K+ and OA-

157
Q

What a typical neuron is at rest, what is the voltage across the membrane

A

~60mV

158
Q

What are the basic principles of electrochemical gradients

A

Forces that could move ions across cell membranes

Net flux of ions across membranes depends on both the concentration gradient and the electrical different = the two driving forces known as electrochemical gradient

Selective ion channels span the lipid bilayer and allow ions to diffuse across the cell membrane

K+ ions will diffused down their concentration gradient: the next flux occurs from high concentration to low concentration

When k+ ions diffuse down their concentration gradient, they are also going towards a positively charged environment. Charges of the same type will repel each other

159
Q

Draw and label a diagram showing the basic principles of electrochemical gradients

A

See lecture notes

160
Q

How is the resting membrane potential maintained

A

1) inability of most large anions to leave the cell
2) electrogenic nature of Na+/k+ pump maintaining the concentration gradients
3) leak channels, mainly leak k+ channels

161
Q

What are leak channels

A

Allow ions to move down their concentration gradient

Na+ enters the cell

K+ leaves the cell

162
Q

What is the Na+/K+ pump?

A

3 Na+ out for every 2 K+ in. This generates concentration gradients

163
Q

What are the two driving forces known as the electrochemical gradient

A

Electrical gradient: the ions are attracted to the side of the membrane with the opposite charge

Chemical gradient: diffusion force driving ions down their concentration gradient (from high to low concentration)

164
Q

Describe small and large graded potentials

A

SMALL transient changes in the membrane potential confined to small region of the plasma membrane:
Provide signalling in short distances
Depolarising
Hyper-polarising

The magnitude of the transient changes in membrane potential can vary:

Dependent on changes in membrane permeability to ions (ligand gated ion channels)
Decreases with distance and time

LARGE changes in the membrane potential of excitable cells only:
Membrane potentials could change from -60 mV to +40mV
Depolarisation
Overshoot
Repolarization
Hyper polarisation
Return to resting membrane potential

Very rapid

Can repeat at variable frequencies however not during the refractory period

165
Q

Graded potentials can summate

A

Initiated at the level of dendrites and soma
Temporal summation
Spatial summation

166
Q

Draw and label a diagram showing large action potentials

A

See lecture notes

167
Q

Where are action potentials initiated

A

Axon hillock which is an all or none event

168
Q

Depolarisation of action potentials need to…?

A

Exceed the threshold Potential

169
Q

Ion channels allow the generation of…

A

Large, rapid changes in membrane potential

Such as ligand gated channels
Mechanically gated channels
Voltage gated channels - the ones that give the membrane its ability to undergo an action potential

170
Q

Describe the propagation of action potentials

A

• Propagation of APs down the axon is the mechanism the nervous system uses to communicate at long distances
• Each AP produces local currents that depolarize the region adjacent to it
• Sequential opening and closing of voltage-gated Na+ and K+ channels along the axon
• Saltatory conduction: APs appear at the Nodes of Ranvier; Low concentration of voltage
gated Na+ channels on myelinated regions
• AP propagation ceases at the end of the axon

171
Q

What are the three main parts of the brain

A

Cerebrum, cerebellum and brain stem

172
Q

What are the four lobes of the brain

A

Frontal lobe

Parietal lobe

Occipital lobe

Temporal lobe

173
Q

What is the function of the frontal lobe

A 
Executive functions 
Thinking 
Planning 
Organising and problem solving 
Emotions 
Behaviour control 
Personality
174
Q

What is the function of the motor cortex?

A

Movement

175
Q

What is the function of the sensory cortex

A

Sensations

176
Q

What is the function of the parietal lobe?

A

Perception
Making sense of the world
Arithmetic
Spelling

177
Q

What is the function of the occipital lobe

A

Vision

178
Q

What is the function of the cerebellum

A

Coordination and balance

179
Q

What is the function of the temporal lobe

A

Memory
Understanding
Language

180
Q

What is the function of the brainstem

A 
Movement 
Heart rate control 
Blood pressure regulation 
Breathing 
Swallowing 
Coughing 
Sneezing 
Vomiting
Sleeping and waking
Dreaming
181
Q

What parts of the brain are exclusively found in the left hemisphere?

A

Brocas and wernickes areas

182
Q

What is Broca’s areas used for

A

Motor and speech

183
Q

What is wernickes areas used for

A

Language comprehension

184
Q

What can brain damage and impaired function occur

A

Traumatic injuries

Acquired injuries

185
Q

Give examples of traumatic injuries

A

Closed head injury: caused by a rapid forward and backward movement and shaking of the brain inside the bony skull

Concussion: causes impairment in brain function. It can be the result of a closed or penetrating head injury

Contusion; bruise of bleeding in the brain that’s due to a blow or jolt to the head

Penetrating injury: brain injury caused by a bullet, knife or sharpe object. Also known as an open head injury

Shaken baby syndrome: excessive shaking of a young child

186
Q

Give examples of acquired injuries

A

Anoxic/hypoxic: injury to brain cells due to a lack of oxygen
Cardiac arrest
Respiratory arrest
Suffocation

Brain infections/inflammation: infections such as meningitis

Stroke: caused by loss of blood flow to The brain

Tumour: can include brain cancer or a cancer related illness

187
Q

Describe an Ischemic stroke and the main causes

A

The blood supply is stopped because of a blood clot. The reduced blood flow causes brain cells in the area to die from a lack of oxygen.

The main cause is atherosclerosis (plaques) in the walls of the arteries which feed the brain. Account for 85% of stroke cases

188
Q

What is a haemorrhagic stroke?

A

The blood vessel is not blocked but it bursts and blood leaks into the soft brain tissue causing major damage

189
Q

What are the four types of stroke?

A

Childhood stroke

Ischemic stroke

Haemorrhagic stroke

A transient ischemic attack (TIA)

190
Q

What is a transient ischemic attack?

A

Also known as a mini stroke.

This is the same as a stroke except the symptoms last for a short amount of time and no longer than 24 hours. This is because the blockage that stops blood getting to the brain is temporary. The symptoms are the same as a full stroke

191
Q

What is a childhood stroke?

A

A childhood stroke may affect any child from 28 weeks old to the age of 18.
Strokes can be associated with existing conditions, most commonly congenital heart disease and sickle cell disease. Other risk factors include infectious disease, trauma to the head or neck, vascular problems and blood disorders

192
Q

What are risk factors of strokes:

A 
Obesity 
Lack of exercise 
Sleep apnea
Heavy alcohol use 
Smoking and drug use 
Diabetes 
Cardiovascular disease 
High cholesterol 
High blood pressure
193
Q

What is the main artery that supplies blood to the brain?

A

The middle cerebral artery which branches off into the anterior cerebral artery and the posterior cerebral artery.

194
Q

What is the central nervous system composed of?

A

Brain

Spinal cord

Relay neurons (interneurons)

195
Q

What is the peripheral nervous system composed of?

A

Cranial nerves

Spinal nerves

Peripheral nerves

Sensory neurons

Motor neurons

196
Q

What is the function of the basal ganglia?

A

Movement

Reward

197
Q

What is the purpose of the thalamus?

A

Sensory gateway

198
Q

What is the purpose of the hippocampus?

A

Memory

199
Q

What is the purpose of the amygdala?

A

Emotion

200
Q

What is the function of the hypothalamus?

A

Regulates body temperature

201
Q

What is a neuron?

A

The basic unit of structure and function in the nervous system

Cells that conduct impulses

Made up of dendrites, cell body and an axon

202
Q

What are dendrites?

A

Branch like extensions that receive impulses and carry them toward the cell body

203
Q

What is the axon?

A

Single extension of the neuron that carries impulses away from the cell body

204
Q

What is the difference between the axon and dendrites?

A

The axon branches out at the end to send impulses to many different neurons. Dendrites receive impulses from many other axons

205
Q

What are Neuroglia?

A

Provide physical support, control nutrient flow and are involved in phagocytosis

206
Q

What are astrocytes?

A

Provide physical support, remove debris (phagocytosis) and transport nutrients to neurons

207
Q

What are microglia?

A

Defensive cells

Involved in phagocytosis and brain immune function

208
Q

What do oligodendrocytes do?

A

They provide physical support and form the myelin sheath around axons in the brain

209
Q

How does ageing impact the brain?

A

Gerontogens are factors, including substances that Can accelerate the ageing process.

Possible gerentogens include arsenic found in groundwater, benzene in industrial emissions, ultraviolet radiation in sunlight and the cocktail of 4000 toxic chemicals in tobacco smoke.

Activities may also be included like ingesting excessive calories or suffering psychological stress

210
Q

How to differentiate between ageing and neurodegenerative disease?

A

Neurodegenerative disease results in the progressive degeneration and or loss of nerve cells - they are a heterogeneous group of disorders that are characterised by the progressive degeneration of the structure and function of the central or peripheral nervous system. The function is progressively lost

Whereas,

Ageing shrinks nerve cells - the brain undergo use numerous changes that affect memory, motor and sensory functions. The function is affected but it is still there.

211
Q

List some common neurodegenerative diseases

A 
Alzheimer’s disease 
Dementia 
Parkinson’s disease 
Multiple sclerosis 
Motor neuron disease 
Spinal muscular atrophy
212
Q

What is Alzheimer’s disease and how was it discovered?

A

The most common type of dementia which affects 850,000 people in the UK.

Dr Alzheimer noticed changes in the brain tissue of a woman who died of an unusual mental illness. Her symptoms included memory loss, language problems and unpredictable behaviour. After she died, the examined her brain and found many abnormal clumps (now called amyloid plaques) and tangled bundles of fibres (now called neurofibrillary).

213
Q

What part of the brain is affected by Alzheimer’s and what are the early symptoms:

A

Hippocampus, the function of the hippocampus is to form memories

Early symptoms: problems with memory and language
- losing items such as keys and glasses around the house
Struggle to find the right word in a conversation
Forgetting someone’s name
Forgetting about recent conversations or events
Getting lost in a familiar place or journey
Forgetting appointments or anniversaries

214
Q

What causes Alzheimer’s?

A

Researches believe there is not a single cause of Alzheimer’s disease.

However, it can be influence by multiple factors including ache, genetics, lifestyle and environment.

215
Q

Discuss the differences between early onset and late onset Alzheimer’s.

A

Early onset AD: genetically inherited (5%)
Occurs in people aged 30 to 60
Mostly inherited, known as familiar AD

Mutations occur in the following genes:
Amyloid precursor protein
Presenilin 1
Presenilin 2

Late onset AD: sporadic (95%)
In most cases, the cause of AD is multi factorial with both genetics and environmental involvement.
Occurs in people over the age of 60
Combination of genetic and environmental factors

Increased risk associated with other genes:
Apoliprotein E
Triggering receptor expressed on myeloid cells 2
Microtubule associated tau protein

216
Q

What are the two main features of Alzheimer’s disease?

A

Plaques and neurofibrillary tangles

217
Q

What is the treatment for Alzheimer’s?

A

There is currently no treatment for Alzheimer’s but there are medications available to temporarily reduce the symptoms:

Main drugs currently used:
Acetylcholinesterase (AChE) inhibitors e.g. donepezil, galantmaine and rivastigmine
These drugs work by inhibiting the enzyme acetylcholinesterase, which increases the levels of acetylcholine which is the neurotransmitter essential for processing memory and learning.
AChE inhibitors can be prescribed for patients with early or mid stage AD. The latest guidelines do not recommend these medications in later, severe disease stages.

Memantine:
Memantine is a N-methyl-d-aspartate (NMDA) receptor antagonist which blocks the effect of high glutamate levels. This improves mental function and the ability to perform daily activities for some people and can be used for moderate to severe AD.
Memantine is also suitable for patients who cannot tolerate AChE initiations. It can be also be taken by people with severe AD who are already taking an AChE inhibitor.

Antidepressants:
May sometimes be given if depression is suspected as an underlying cause of anxiety.

218
Q

What is Parkinson’s disease?

A

Parkinson’s disease is a progressing nervous system disorder that affected movement.

Parkinson’s is the second most common neurodegenerative disorder after Alzheimer’s disease

219
Q

What did James Parkinson describe Parkinson’s disease as?

A

It is a condition which causes characteristic paralysis, diminished muscle strength, abnormal postures and resting tremors.

220
Q

What are the three main symptoms of Parkinson’s disease?

A

Tremor

Muscle stiffness

Slowness of movement

221
Q

What are the two types of Parkinson’s disease?

A

Parkinson’s disease normally affects older people, but 1 in 20 people diagnosed are under 40. The mean age of onset is 55 years old.

Early onset (genetic): a small proportion of PD cases are genetically inherited

Late onset (sporadic). In most cases, PD is sporadic, with both genetic and environmental involvement

222
Q

What are the risk factors of Parkinson’s?

A 
Environment: 
Toxic chemicals 
Herbicides 
Pesticides 
Viruses, bacteria 
Trauma

Lifestyle:
Stress
Sleep
Diet

Genes

223
Q

What are the main symptoms of Parkinson’s disease?

A

TRAP

Tremor; shaking, usually starting on one side of the body

Rigidity; stiffness of the limbs, neck or trunk

Akinesia; loss or impairment in power of voluntary movement

Posture and balance

224
Q

What causes Parkinson’s disease?

A

Parkinson’s disease is caused by a loss of nerve cells in part of the brain called the substantia nigra. This leads to a reduction in a chemical called dopamine in the brain

Dopamine plays a viral role in regulating the movement of the body. A reduction of dopamine is responsible for many of the symptoms of Parkinson’s disease

225
Q

What are the key hallmarks of Parkinson’s disease?

A

Lewy bodies and lewy neutrites are key histopathological hallmarks of PD.

They are spherical cytoplasmic protein aggregates. They contain numerous proteins including alpha-synuclein, Parkin, ubiquitin and neurofilaments

226
Q

What is the cure for Parkinson’s disease?

A

There is currently no cure however there are medications available to temporarily reduce the symptoms.

Current treatments can only help symptomatically and have a limited time efficacy.

Medications such as levodopa

Surgical; deep brain stimulation

227
Q

Draw the pharmacological treatment of Parkinson’s disease

A

See lecture slides

228
Q

Wha this Huntington’s disease ?

A

It is a genetic disorder (autosomal dominant inheritance) characterised by the gradual and progressive loss of neurons, predominantly in the basal ganglia.

HD can impact movement, learning, thinking and emotions

229
Q

What is the function of the basal ganglia?

A

It is responsible for voluntary motor control, procedural learning, eye movement and control of behaviour and motivation

230
Q

What are the symptoms of Huntington’s disease?

A

Involuntary movements (chorea)
Weight loss
Abnormal gait
Speech and swallowing difficulties

Personally changes
Depression
Aggression
Early onset dementia

Mean onset age 35-55 years old with death occurring 10-20 years from onset. A small percentage of patients (10%) develop symptoms before the age of 20

231
Q

Is Huntington’s disease a genetic order and what is the likelihood of the disease being passed on?

A

HD is a dominant autosomal disorder

If a parent has the gene there is a 1 in 2 chance (50%) chance that each of their children will develop the condition.

Affected children can also pass on the condition to their children

There is a 50% chance of each other of their children never developing the condition- unaffected children cannot pass the condition onto their children

232
Q

What is a treatment for Huntington’s disease?

A

Tetrabenazine controls chorea

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