Biology > Nerves > Flashcards

Nerves Flashcards

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1
Q

What is the cell body?

A

Contains nucleus, carries genetic code for production neurotransmitters
Nissl granules, dense group of ribosomes and ER, site of protein systhesis to make neurotransmitter

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2
Q

Where is the cell body in sensory neurones?

A

Cell bodies in the middle, in dorsal root ganglia

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3
Q

Where is the cell body in the motor neurone?

A

Cell bodies in spinal cord or brain

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4
Q

What is an axon?

A

Transmits action potential away from cell body
Can be over 1m in length, 10μm diameter
Allows for rapid transmission of impulse, reduces number of synapses required which are the area of slower transmission
Contains axoplasm and usual cell organisms

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5
Q

What are dendrons?

A

Fine extension of cell, transmits action potential towards cell body

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6
Q

What are dendrites?

A

Fine extension of the cell to allow communication with other neurones

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7
Q

What is the plasma membrane?

A

Phospholipid bilayer with many protein ion channels

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8
Q

What are schwann cells?

A

Thin cells which are wrapped around neurone
Have a higher than usual phospholipid content in their membranes and fewer ion channels, increasing electrical insulation of the neurone

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9
Q

What is the myelin sheath?

A

Enclosing layer made by Schwann cells

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10
Q

What is the node of Ranvier?

A

Regions of uninsulated membrane where ion movement occurs to create action potential

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11
Q

What is the synaptic knob?

A

Point at which neurotransmitter is released from neurone to transfer the action potential to another neurone

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12
Q

What is the motor end plate/neuromuscular junction?

A

Point at which neurotransmitter is released from neurone to transfer the action potential to a muscle

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13
Q

What are sensory neurones?

A

Transmit nerve impulse from sensory receptor to CNS
At CNS may synapse with relay/motor
Cell body in ganglia just outside CNS

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14
Q

What are motor neurones?

A

Transmit nerve impulses from CNS to an effector.
Could be a gland or muscle.
Cell body in CNS

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15
Q

What is the CNS?

A

Central Nervous System

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16
Q

What is a nerve?

A

A bundle of neurones

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17
Q

What are relay neurones?

A

Connect sensory and motor neurones.
Totally in CNS

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18
Q

What are myelinated neurones?

A

Schwann cells wrap themselves around the neurone, creating myselin sheath.
Schwann cell plasma has higher than usual phospholipid content with few ion channels, so ion movement only occurs at nodes of Ranvier
Electrically insulates the nerve

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19
Q

What are sensory receptors?

A

Specialised cells that can detect changes in our surroundings
Initiate a nerve impulse
Are transducers
Specific to a stimulus

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20
Q

What are transducers?

A

Cell that converts one form of energy into another
Stimulus converted into a nerve impulse: electrical energy

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21
Q

What is the Pacinian Corpsucle?

A

A sensory receptor that detect mechanical pressure on skin

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22
Q

How does the pacinian corpsucle detect change?

A

Detects mechanical pressure on skin
Changes deform the layers of connective tissue
This pushes against the nerve ending
Initiates nerve impulse
Sensitive to changes in pressure, so if the pressure becomes constant it will stop initiating nerve impulses, explains why you stop feeling clothes soon after putting them on

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23
Q

What does polarised mean?

A

A membrane which has a potential difference across it. This is the resting potential

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24
Q

What does depolarisation mean?

A

Loss of polarisation across the membrane, refers to the period where sodium ions are entering the cell making inside less negative

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25
What is the resting potential?
The potential difference across the membrane whilst the neurone is at rest
26
What is the p.d of the resting potential?
~-70mV (millivolts)
27
What is the action potential?
The depolarisation of the cell membrane. A fleeting reverse of the resting potential
28
What is the p.d of the action potential?
~+40mV (millivolts)
29
What is hyperpolarisation?
When the potential difference overshoots slightly and becomes more negative than the resting potential
30
What is the p.d of hyperpolarisation?
~-80mV (millivolts)
31
What is the refractory period?
The time after an action potential has passed when it is impossible to stimulate the cell membrane because sodium voltage gated channels will not reopen. It ensures that action potentials only move in ONE DIRECTION and keeps each impulse separate
32
What is threshold potential?
A potential different of across the membrane of about -50mV. If depolarisation of the membrane does not reach this value then an action potential is not generated.
33
What is generator potential
A small change in the p.d within the cell due to some Na+ diffusing into the cell
34
What is the all or nothing principle?
If the stimulus reaches the threshold value then an action potential will be generated No matter how larger the stimulus, the action potential is always the same size
35
What is repolarisation?
When the neurone returns to having a negative potential difference inside it, returns to resting potential
36
What is saltatory conduction?
When an action potential 'jumps' from a node of Ranvier to another, and depolarisation of the membrane only occurs at the nodes
37
What is potential difference?
The difference in charge between the inside and outside of a neurone
38
How is resting potential achieved?
Na+/K+ pump uses energy from ATP hydrolysis to move 3Na+ out and 2K+ in All Na+ channels closed, no Na+ able to diffuse in Some K+ channels open, so some K+ diffuse out, increases p.d across membrane Large organic anions (negative) in cytoplasm, add to neg. charge within the cell All the above keep the cell polarised with a slight p.d across membrane of -70mV inside compared to outside
39
What does polarised mean?
Membrane with a charge difference across it
40
What happens in the neurone when a stimulus is recieved in order to generate an action potential?
Stimulus causes strech-mediated Na+ channels to open Some sodium ions diffuse into the neurone This reduces the charge difference across the membrane -Membrane starts to depolarise (becomes less -ve inside neurone)
41
What is a reflex action?
Response to change in environment (stimulus) that doesn’t involve any brain processing to coordinate the movement. Usually just 3 neurones - short = fast The brain may be informed that the reflex is happening, but it is not involved in coordinating the response.
42
How do reflex actions increase the chance of survival?
Immediate: fast, removes us from danger Innate: present from birth so provide immediate protection Involuntary and invariable: same response every time, so the higher levels of the brain are freed up for more complex decisions.
43
What is involved in the blinking reflex?
Sensory receptor and neurone in cornea Non-myelinated relay neurone Motor neurone
44
What is involved in the knee jerk reflex?
Patella tendon Relay neurone Motor neurone
45
What type of reflex is the blinking reflex?
Cranial reflex, happens in brain
46
What type of reflex is the knee jerk reflex?
Spinal reflex, only goes up spinal cord and not into brain
47
What are the steps of generating an action potential?
1. Resting potential 2. Stimulus recieves 3. Depolarisation 4. Repolarisation
48
Draw out the generation of the action potential
See cursive online drawing
49
Outline what the refractory period is and the 2 advantages it gives to the neurone
Short period of time when neurone cannot be depolarised again Voltage gated sodium ion channels cannot re-open, even with a raised potential difference Ensures action potential goes in ONE DIRECTION (!!) only and do not go backwards, helps to keep action potentials separate, do not combine
50
Draw out the propagation of an action potential in a non-myelinated neurone
See cursive online drawing
51
Draw out the propagation of an action potential in a myelinated neurone
See cursive online drawing
52
What is saltatory conduction?
Jumping action potential from one Node of Ranvier to another
53
Why is conduction in myelinated neurones faster than in non-myelinated?
Reduced the number of places where ion channels open and move along the membrane
54
Why is saltatory conduction more energy efficient than non-myelinated conduction?
Repolarisation uses ATP, so reducing amount of repolarisation needed makes it more efficient.
55
What are 3 factors that will increase the speed of transmission of an action potential?
Axon diameter: the bigger, the faster as less resistence to flow of ions in cytoplasm Temperature: higher, faster, ions diffuse faster at higher temperatures, only occurs up to 40°C, as higher denatures Presence of myelin sheath: allows for saltatory conduction
56
What are synapses?
Junctions between neurones Information is sent between neurones by chemical transmission Neurotransmitters pass across the synaptic cleft A new action potential will be triggered in the post synaptic neurone
57
Draw and annotate the parts of a synapse
See cursive online drawing
58
Draw and annotate synaptic transmission
See cursive online drawing
59
What is the role of synapses?
To ensure action potentials travel in ONE DIRECTION !! only -Vesicles containing neurotransmitters are only in synaptic knobds -Receptor molecules are only on post To allow impulses from one neurone to be spread to many neurones -A single stimulus can result in multiple responses To allow many neurones to feed into one synapse so only one neurone transmits further Summation (spatial and temporal
60
What is summation?
When the effects of several generator potentials are added together
61
What is spatial summation?
When the combined effect of neurotransmitters released from several neurones reaches threshold lvl in the post synaptic neurone
62
What is temporal summation?
When frequence impulses from one neurone result in enough neurotransmitters being released to reach threshold lebvel in post synaptic neurone
63
What is the central nervous system composed of?
Brain and spinal cord
64
What is the peripheral nervous system composed of?
All the other neurones that connect CNS to the body Sensory neurones carrying nerve impulses from nerve impulses from receptors to CNS Motor neurones carrying impulses from CNS to effectors, muscles and glands
65
What is/are features of the spinal cord?
Ascending and descending nerve tracts allow communication with the brain Relay neurones have multiple connections allowing this communcation Much of the brain is composed of relay neurones enabling complex neural pathways
66
What is the structural difference between grey and white matter?
White matter is neurones which have myelinated sheath, appear white Grey matter is where there is no myelin sheath, mainly synapses and cell bodies
67
What type of matter are relay neurones?
Mostly non-myelinated, make up much of the grey matter
68
Draw a summary of the mammalian nervous system
See cursive online drawing
69
Where is the ganglia of the parasympathetic pathway?
Ganglia are close to inside wall of the effector -Far from CNS -Organs will be activated only when time and energy allows
70
Where is the ganglia of the sympathetic pathway?
Closer to spinal cord -Send a quick impulse to synapse to trigger multiple responses very quickly via many different neurones to many effectors
71
What do both sympathetic and parasympathetic systems release at the synapse in the ganglia?
Acetylcholine
72
What does the parasympathetic system release at the synapse with the effector?
Acetylcholine
73
What does the sympathetic system release at the synapse with the effector?
Noradrenaline
74
What is the function of the skull?
Bones called cranium which protect delicate nervous tissue
75
What is the function of meninges?
Membranes which surround the CNS Secrete CSF Along with the cerebral spinal fluid they offer protection
76
What is the function of the cerebro-spinal fluid?
Secreted by meninges, provides protection via absorbing mechanical shocks Provides nutrients and oxygen to brain cells
77
What is the function of the ventricles?
Spaces within brain filled with cerebro-spinal fluid
78
What is the function of the corpus callosum?
Connects left and right cerebral hemispheres, allowing the two sides of the cerebrum to communicate
79
What is the cerebrum?
Consists of 2 cerebral hemispheres Connected via corpus callosum Each hemisphere controls one half (the opposite) side of the body Ascending and descending nerve tracts cross over in the medulla oblongata
80
What is the function of the cerebrum?
Controls the higher brain functions -Conscious thought -Conscious actions (including the ability to override some reflexes) -Emotional responses -Intelligence, reasoning, judgement, and decision making -Factual memory
81
What is the cerebellum?
Contains over half the neurones in the brain Involved in unconscious functions (eg fine coordination of movement) Recieves information from sensory receptors -Retina -Balance organs of inner ear -Spindle fibres in muscles, provide info about muscle lengths and joints
82
What are some examples of cerebellum control?
-Coordinating contraction and relaxation of antagonistic skeletal muscles to maintain body position and balance (walking, cycling) -Judging position of limbs when playing sport -Tensioning muscles in order to use tools or play musical instruments Many of these processes require learning
83
What is the medulla oblongata?
Has only autonomic control over non-skeletal muscles Contains following centres: -Cardiac centre to regulate cardiac cycle and heart rate -Vasomotor area to regulate circulation and blood pressure -Respiratory centre to regulate rate and depth of breath Also controls swallowing, vomiting and coffin
84
What is the hypothalamus?
Main area controlling centre for the autonomic nervous systems and has 2 centres: sympathetic and parasympathetic Controls homeostatic mechanisms by negative feedback
85
What are the functions of the hypothalamus?
Temperature regulation by monitoring core body temperature as well as using peripheral skin receptors Osmoregulation, contains osmoreceptors to monitor blood water potential, brings about corrections by stimulating the pituitary gland to secrete hormones Produced hormones, stimulate pituitary gland for fight or flight Controls feeding sleeping and aggression
86
What is the pituitary gland?
Consists of 2 lobes -Posterior pituitary: stores and releases hormones produced by hypothalamus eg ADH -Anterior pituitary: produces own hormones which release into the blood and is stimulated by release factors (hormones) produced by the hypothalamus )eg hormones to control growth, reproduction and response to stress)
87
What happens if the cerebellum is damaged?
Results in jerky, uncoordinated movement, like when very drunk
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