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
Describe the position and function of the midbrain
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
26
What is the function of the pons?
Integrates information from the motor cortex and cerebellum (balance) A pneumotaxic centre- regulation of respiration together with the medulla
27
What is the medulla oblingata?
Forms the cavity of the fourth ventricle Autonomic reflex centre involved in maintaining body homeostasis
28
The medulla oblongata is the centre for what responses?
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
29
What is the cerebellum?
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
30
Define proprioceptors
Receptors sending information about muscle tension, tendon and joint position
31
What are the three main protectors of the brain?
The skull (cranium) and its many layers Cerebrospinal fluid The blood brain barrier
32
What are the three protective layers within the cranium?
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
33
What is cerebrospinal fluid and what is its function
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
34
Describe the route of blood supply to the brain
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
35
What are the two major roles of the peripheral nervous system?
To send inflation about the environment to the brain To transmit information to the effector organs of the human body
36
What are sensory receptors and how are they classified?
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
37
Discuss how sensory receptors are classified by location:
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
38
How are sensory receptors classified by stimulus type detection?
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
39
How are sensory receptors classified by structural complexity?
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
40
What is meissners corpuscles:
Pressure sensors on hairless skin e.g. lips and fingertips
41
What are krauses end bulbs?
Sensors on connective tissue
42
What are pacinian corpuscles?
Sensors on skin, tendons and ligaments
43
What are golgi tendon organs?
Sensors in tendons
44
What do uncapsulated receptors in the skin detect?
Pain and movement
45
What do encapsulated receptors in the skin detect?
Pressure and temperate
46
What are sensor receptor potentials?
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
47
What is the spinal column and describe the structure
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 ```
48
What is the functions of the spinal column?
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
49
What is the spinal cord?
Lies encased within the spinal column Bundles of nerves relaying information to and from the brain
50
What is reflex activity?
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
51
List the components of a reflex arc?
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
52
Draw and label a simple reflex arc
See lecture slides
53
What are muscle spindles?
Located within skeletal muscle Act as stretch receptors Respond to increases/decreases in muscle contraction
54
What is the anatomy of muscle spindles?
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
55
What are intrafusal fibres?
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
56
What are gamma fibres?
Cause the intrafusal fibres to contract (small contractions only)
57
What are alpha fibres?
They cause the gross conduction of the muscle
58
What does muscle spindles in recruitment mean?
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
59
What is the stretch reflex?
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
60
Outline the roles/ organisation of the peripheral nervous system
See lecture notes
61
Describe the location classification used fro sensory receptors
See lecture notes
62
Describe the stimulus detection classification used for sensory receptors
See lecture notes
63
Describe the structural complexity classification used fort the sensory receptors
See lecture notes
64
Describe the structure organisation and function of the spinal cord
See lecture notes
65
Draw a labelled diagram of a spinal cord cross section
See lecture notes
66
Outline the components of a reflex arc
See lecture notes
67
Describe the anatomy of muscle spindles and their role in muscle fibre recruitment
See lecture notes
68
Describe the stretch reflex
See lecture notes
69
Describe the location of the human brain
See lecture notes
70
Label a diagram of the major regions of the brain
See lecture notes
71
Outline the major composition and functions associated with the cerebral cortex
See lecture notes
72
Outline the major functions associated with the diencephalon, to include the thalamus, hypothalamus and epithalamus
See lecture notes
73
Label a diagram of the anatomical regions that make up the brain stem
See lecture notes
74
Outline the functions associated with the brain stem
See lecture notes
75
Outline the functions associated with the cerebellum
See lecture notes
76
What protecting mechanisms are in place for the Brain?
See lecture notes
77
Compare the somatic and autonomic nervous system
See lecture notes
78
What are effectors?
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
79
What are efferent the pathways and ganglia:
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
80
Draw the efferent pathways of the autonomic nervous system
See lecture slides
81
What are the effects of neurotransmitters?
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
82
Draw the neurotransmitters of the somatic and autonomic nervous systems
See lecture notes
83
Discuss the overlap of somatic and autonomic function
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
84
What are the divisions of the ANS?
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
85
What does the parasympathetic division do?
Performs maintenance activities and conserves the bodies energy
86
What does the sympathetic division do?
Utilised under extreme conditions ‘fight or flight’ response
87
What is the role of the parasympathetic division?
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)
88
What are the signs that the parasympathetic division is at rest
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)
89
What is the role of the sympathetic division?
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
90
What are the signs the sympathetic division has been activated?
``` Pounding heart Rapid deep breath Cold, sweaty skin Dilated pupils Changes in Brian waves and electrical conductivity of skin ```
91
Describe and compare the innervations of the ANS divisions e.g. what happens to body systems at sympathetic division and parasympathetic division
See lecture diagram
92
What sympathetic adjustments occur during exercise?
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
93
Discuss the physiology of the ANS
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
All ACh receptors are either:
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
Show the typical response to stress
See lecture slides
96
What has been developed to block the inhibitory and excitatory effects of the ANS
Drugs such as atropine and anticholinesterase
97
What does atropine do?
Dilutes pupils before surgery
98
What doe santicholinesterase drugs do?
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
Discuss the interactions of the ANS
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
What is sympathetic tone?
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
What is sympathetic tone?
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
Describe the differences between the somatic and autonomic nervous system:
See lecture notes
103
Describe the structural organisation of the ANS neuronal pathway
See lecture notes
104
Outline the roles of the two divisions of the ANS
See lecture notes
105
List the sympathetic adjustments that occur during exercise
See lecture notes
106
List the receptors of the ANS and their associated activation neurotransmitters
See lecture notes
107
Outline the response to a stressful situation on heart rate
See lecture notes
108
Outline the functions of sympathetic and parasympathetic tone
See lecture notes
109
Define neurons and glia
The cells from which the nervous system is assembled
110
Define neurons
Process and transmit information Include synapses Found in the whole of the nervous system ~ 100 distinct types
111
Define neuroglia
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
Draw and label the anatomy of a neuron
See lecture notes
113
Describe the anatomy of neurons
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
Draw the structures of A) multipolar interneurons B) Motor neurons C) sensory neurons
See lecture notes
115
Draw the pain withdrawal reflex arc
See lecture notes
116
Draw the pain withdrawal reflex showing the peripheral nervous system and central nervous system
See lecture notes
117
What are glial cells
They support neurons and modulate neuronal functions
118
What do oligodendrocytes and Schwann cells do?
Form the insulating sheaths of axons
119
What is an oligodendrocyte and where are they found?
One oligodendrocyte can produce myelin sheaths for segments of as many as 30 axons Found in the central nervous system
120
What are Schwann cells and where are they found?
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
What is the purpose of myelin sheaths?
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
What do astrocytes do?
Participate actively in synaptic transmission
123
Draw the process of synaptic transmission in the central nervous system
See lecture notes
124
What are the supporting roles of astrocytes?
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
What part of the body are astrocytes active components of?
The blood brain barrier
126
What are astrocytes endfeet?
Not much of a structural role Provide nourishment to endothelial cells that form the bbb Filtering of unwanted and possibly harmful substances
127
What are microglia
Microglia play an important role in immunological surveillance of the CNS They are poised to react to foreign invaders of the CNS
128
What do microglia do at resting state?
They scan the interstitial fluid
129
When do microglia work in their active state?
Because of signs of inflammation Presence of bacteria (infection)
130
What are the functions of microglia?
Phagocytosis: clearing debris During inflammation; Secrete cytokines and chemokines that will serve to trigger an immune reaction Antigen presentation to lymphocytes
131
What are ependymal cells
They assist with the move of cerebrospinal fluid CSF though the ventricular system
132
What is the purpose of CSF
It functions as a shock absorber fluid cushion for the brain and the spinal cord
133
What are ependymal cells
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
How do neurons communicate?
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
Define synapse
Anatomically specialised junction between two cells
136
What is divergence
One single neuron can synapse onto many other post synaptic cells
137
What is convergence
Many synapses from different presynaptic neurons can synapse with a single cell
138
What is the function of divergence in neuron communication
A mechanism for spreading stimulation to multiple neurons or neuronal pools in the CNS
139
What is the purpose of convergence in the communication of neurons
A mechanism for providing input to a single neuron from multiple sources
140
What are the two types of snynapse
Electrical synapse and chemical synapse
141
What is an electrical synapse
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
What is a chemical synapse
Operates through the release of neurotransmitters
143
Draw an electrical synapse diagram
see lecture notes
144
Draw a chemical ‘tripartite’ synapse
See lecture notes
145
Draw and label a diagram showing the release of neurotransmitters through chemical synapses
See lecture notes
146
Draw and label a diagram showing the action of drugs pm a chemical synapse
See lecture notes
147
How can a drug work on chemical synapses?
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
Describe the communication of neurons
Information is carried within neurons and from neurons to their target cells by electrical and chemical signals
149
Describe the electrical forces between ions
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
What is the electrical potential of extra cellular and intracellular
The potential difference across the membrane will be ~69mV
151
Draw and label a cell and show the charges within and outside of the cell and discuss what the membrane potential is
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
Draw and label a diagram of the plasma membrane
See lecture notes
153
Discuss the resting potentials of neurons
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
Discuss the electrical and concentration gradients across the plasma membrane of a typical neuron
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
What ions are in higher concentration outside of the cell
Na+ and Cl-
156
What ions are higher in concentration inside of the cell
K+ and OA-
157
What a typical neuron is at rest, what is the voltage across the membrane
~60mV
158
What are the basic principles of electrochemical gradients
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
Draw and label a diagram showing the basic principles of electrochemical gradients
See lecture notes
160
How is the resting membrane potential maintained
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
What are leak channels
Allow ions to move down their concentration gradient Na+ enters the cell K+ leaves the cell
162
What is the Na+/K+ pump?
3 Na+ out for every 2 K+ in. This generates concentration gradients
163
What are the two driving forces known as the electrochemical gradient
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
Describe small and large graded potentials
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
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Graded potentials can summate
Initiated at the level of dendrites and soma Temporal summation Spatial summation
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Draw and label a diagram showing large action potentials
See lecture notes
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Where are action potentials initiated
Axon hillock which is an all or none event
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Depolarisation of action potentials need to…?
Exceed the threshold Potential
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Ion channels allow the generation of…
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
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Describe the propagation of action potentials
• 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
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What are the three main parts of the brain
Cerebrum, cerebellum and brain stem
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What are the four lobes of the brain
Frontal lobe Parietal lobe Occipital lobe Temporal lobe
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What is the function of the frontal lobe
``` Executive functions Thinking Planning Organising and problem solving Emotions Behaviour control Personality ```
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What is the function of the motor cortex?
Movement
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What is the function of the sensory cortex
Sensations
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What is the function of the parietal lobe?
Perception Making sense of the world Arithmetic Spelling
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What is the function of the occipital lobe
Vision
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What is the function of the cerebellum
Coordination and balance
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What is the function of the temporal lobe
Memory Understanding Language
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What is the function of the brainstem
``` Movement Heart rate control Blood pressure regulation Breathing Swallowing Coughing Sneezing Vomiting Sleeping and waking Dreaming ```
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What parts of the brain are exclusively found in the left hemisphere?
Brocas and wernickes areas
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What is Broca’s areas used for
Motor and speech
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What is wernickes areas used for
Language comprehension
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What can brain damage and impaired function occur
Traumatic injuries Acquired injuries
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Give examples of traumatic injuries
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
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Give examples of acquired injuries
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
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Describe an Ischemic stroke and the main causes
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
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What is a haemorrhagic stroke?
The blood vessel is not blocked but it bursts and blood leaks into the soft brain tissue causing major damage
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What are the four types of stroke?
Childhood stroke Ischemic stroke Haemorrhagic stroke A transient ischemic attack (TIA)
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What is a transient ischemic attack?
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
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What is a childhood stroke?
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
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What are risk factors of strokes:
``` Obesity Lack of exercise Sleep apnea Heavy alcohol use Smoking and drug use Diabetes Cardiovascular disease High cholesterol High blood pressure ```
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What is the main artery that supplies blood to the brain?
The middle cerebral artery which branches off into the anterior cerebral artery and the posterior cerebral artery.
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What is the central nervous system composed of?
Brain Spinal cord Relay neurons (interneurons)
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What is the peripheral nervous system composed of?
Cranial nerves Spinal nerves Peripheral nerves Sensory neurons Motor neurons
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What is the function of the basal ganglia?
Movement Reward
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What is the purpose of the thalamus?
Sensory gateway
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What is the purpose of the hippocampus?
Memory
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What is the purpose of the amygdala?
Emotion
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What is the function of the hypothalamus?
Regulates body temperature
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What is a neuron?
The basic unit of structure and function in the nervous system Cells that conduct impulses Made up of dendrites, cell body and an axon
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What are dendrites?
Branch like extensions that receive impulses and carry them toward the cell body
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What is the axon?
Single extension of the neuron that carries impulses away from the cell body
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What is the difference between the axon and dendrites?
The axon branches out at the end to send impulses to many different neurons. Dendrites receive impulses from many other axons
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What are Neuroglia?
Provide physical support, control nutrient flow and are involved in phagocytosis
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What are astrocytes?
Provide physical support, remove debris (phagocytosis) and transport nutrients to neurons
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What are microglia?
Defensive cells Involved in phagocytosis and brain immune function
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What do oligodendrocytes do?
They provide physical support and form the myelin sheath around axons in the brain
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How does ageing impact the brain?
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
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How to differentiate between ageing and neurodegenerative disease?
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.
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List some common neurodegenerative diseases
``` Alzheimer’s disease Dementia Parkinson’s disease Multiple sclerosis Motor neuron disease Spinal muscular atrophy ```
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What is Alzheimer’s disease and how was it discovered?
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).
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What part of the brain is affected by Alzheimer’s and what are the early symptoms:
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
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What causes Alzheimer’s?
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.
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Discuss the differences between early onset and late onset Alzheimer’s.
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
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What are the two main features of Alzheimer’s disease?
Plaques and neurofibrillary tangles
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What is the treatment for Alzheimer’s?
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.
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What is Parkinson’s disease?
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
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What did James Parkinson describe Parkinson’s disease as?
It is a condition which causes characteristic paralysis, diminished muscle strength, abnormal postures and resting tremors.
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What are the three main symptoms of Parkinson’s disease?
Tremor Muscle stiffness Slowness of movement
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What are the two types of Parkinson’s disease?
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
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What are the risk factors of Parkinson’s?
``` Environment: Toxic chemicals Herbicides Pesticides Viruses, bacteria Trauma ``` Lifestyle: Stress Sleep Diet Genes
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What are the main symptoms of Parkinson’s disease?
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
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What causes Parkinson’s disease?
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
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What are the key hallmarks of Parkinson’s disease?
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
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What is the cure for Parkinson’s disease?
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
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Draw the pharmacological treatment of Parkinson’s disease
See lecture slides
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Wha this Huntington’s disease ?
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
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What is the function of the basal ganglia?
It is responsible for voluntary motor control, procedural learning, eye movement and control of behaviour and motivation
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What are the symptoms of Huntington’s disease?
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
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Is Huntington’s disease a genetic order and what is the likelihood of the disease being passed on?
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
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What is a treatment for Huntington’s disease?
Tetrabenazine controls chorea